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The Cantabrian orocline is a large structure that bends the Variscan orogen of Western Europe in NW Iberia. The extensively studied kinematics of its core, the foreland of the orogen, indicates that the structure is secondary, i.e. acquired after the formation of the orogenic edifice. However, the extent of the Cantabrian orocline away from its core is under debate. In this paper we study the kinematics of the Cantabrian orocline beyond the foreland. We collected and analyzed samples from the northern and central parts of the Truchas syncline, which provides new data within the hinterland of the orogen in NW Iberia. The analysis of 320 samples shows a late Carboniferous remagnetization with an E to NE declination and shallow downward inclinations. These results suggest a counter-clockwise rotation of ~ 60° and peri-equatorial but still southern hemisphere latitude for Iberia during the uppermost Carboniferous–Early Permian. This rotation fits with the expected kinematic evolution of the Truchas syncline if it indeed was part of the Cantabrian orocline. [ABSTRACT FROM AUTHOR]

The Taiwan mountain belt is generally thought to develop above a through-going basal thrust confined to within the sedimentary cover of the Eurasian continental margin. Surface geology, magnetotelluric, earthquake hypocenter, and seismic tomography data suggest, however, that crustal levels below this basal thrust are also currently being involved in the deformation. Here, we combine seismic tomography and earthquake hypocenter data to investigate the deformation that is taking place at depth beneath south-central Taiwan. In this paper, we define the basement as any pre-Eocene rifting rocks, and use a P-wave velocity of 5.2 km/s as a reference for the interface between these rocks and their sedimentary cover. We found that beneath the Coastal Plain and the Western Foothills clustering of hypocenters near the basement-cover interface suggests that this interface is acting as a detachment. This detachment is located below the basal thrust proposed from surface geology for this part of the mountain belt. Inherited basement faults appear to determine the geometry of this detachment, and their inversion in the Alishan area result in the development of a basement uplift and a lateral structure in the thrust system above them. However, across the Shuilikeng and the Chaochou faults, earthquake hypocenters define steeply dipping clusters that extend to greater than 20 km depth, above which higher velocity basement rocks are uplifted beneath the Hsuehshan and Central ranges. We interpret these clusters to form a deeply penetrating, east-dipping ramp that joins westward with the detachment at the basement-cover interface. It is not possible to define a basal thrust to the east, beneath the Central Range. [ABSTRACT FROM AUTHOR]

The Pan-African Lufilian orogenic belt hosts world-class Cu deposits. In the Congolese Copperbelt (DRC), Cu(–Co) deposits, are mostly hosted within evaporitic and siliciclastic Neoproterozoic metasedimentary rocks (Mines Subgroup) and are interpreted as syn- to late-diagenetic deposits. In this paper, we present new data on Cu(–U) deposit hosted in metamorphic rocks of the internal zone of the Lufilian belt known as the Western Zambian Copperbelt in which a primary Cu mineralization is overprinted by a second syn-metamorphic Cu mineralizing event. This mineralizing event is synchronous with the Pan-African metamorphism affecting both the pre-Katanga basement and the Katanga metasedimentary sequence. Cu(–U) occurrences in the Western Zambian Copperbelt are hosted by kyanite-micaschists metamorphosed in the upper amphibolite facies. Mineral inclusions of graphite, micas and sulfides in kyanite porphyroblasts of the Cu-bearing kyanite-micaschists in the Lumwana Cu deposit point to a sedimentary protolith with relics of an inherited Cu stock. Based on petrologic, microstructural and geochronological evidence, we propose that this initial Cu-stock was remobilized during the Pan-African orogeny. Graphite, micas and sulfides preserved in a first generation of kyanite poikiloblasts (Ky 1 ) define an inherited S 0/1 foliation developed during the prograde part of the P – T path (D 1 deformation-metamorphic stage) reaching HP–MT metamorphic conditions. Remobilization during the retrograde part of the P – T path is evidenced by chalcopyrite–pyrrhotite and chalcopyrite–bornite delineating a steep-dipping S 2 schistosity and by chalcopyrite and bornite delineating a shallow-dipping S 3 schistosity associated with top to the south kinematic criteria. This retrograde path is coeval with ductile deformation in the kyanite field as evidenced by a second generation of synkinematic kyanite porphyroblasts (Ky 2 ) transposed in the S 3 schistosity (Ky 2–3 ), and is marked by progressive cooling from ca. 620 °C down to 580 °C (rutile geothermometry). Syn-S 2–3 metamorphic monazite grains yield U–Th–Pb ages ranging from ca. 540 to 500 Ma. Final retrogression and remobilization of Cu is marked by recrystallization of the sulfides in top to the north C 3 shear bands associated with rutile crystals yielding temperatures from ca. 610 to 540 °C. This final remobilization is younger than ca. 500 Ma (youngest U–Th–Pb age on syn-S 3 recrystallized monazite). These data are consistent with successive Cu remobilization for more than 40 Ma during Pan-African reworking of sediment-hosted deposits either from the basement of the Katanga sedimentary sequence or from the Katanga sequence itself marked by burial (D 1 ), syn-orogenic exhumation (D 2 ), and post-orogenic exhumation during gravitational collapse (D 3 ). [ABSTRACT FROM AUTHOR]

Although the Himalaya is the archetype of collisional orogens, formed as a consequence of the closure of the Neo-Tethyan ocean separating India from Asia, high-pressure metamorphic rocks are rare. Beside few eclogites, corresponding to the metamorphosed continental Indian crust dragged below Asia or underthrusted beneath southern Tibet, blueschists occur seldom along the Yarlung–Tsangpo Suture zone, i.e. the suture marking the India–Asia collision. These blueschists, mostly interpreted as related to paleo-accretionary prisms formed in response to the subduction of the Neo-Tethyan ocean below the Asian plate, are crucial for constraining the evolution of the India–Asia convergence zone during the closure of the Neo-Tethyan Ocean. In the Western Himalaya, the best occurrence of blueschist is that of the Sapi–Shergol Ophiolitic Mélange in Ladakh. This unit is dominated by volcanoclastic sequences rich in mafic material with subordinate interbedding of metasediments, characterized by very fresh lawsonite blueschist-facies assemblages. In this paper, the lawsonite blueschist-facies metasediments have been petrologically investigated with the aims of (i) constraining the P–T evolution of the Sapi–Shergol Ophiolitic Mélange, (ii) evaluating the influence of Fe 2 O 3 and of H 2 O on the stability of the high-pressure mineral assemblages, (iii) understanding the processes controlling lawsonite formation and preservation, and (iv) interpreting the P–T evolution of the Sapi–Shergol blueschists in the framework of India–Asia collision. Our results indicate that (i) the Sapi–Shergol blueschists experienced a cold subduction history along a low thermal gradient, up to peak conditions of ca. 470 °C, 19 kbar; furthermore, in order to preserve lawsonite in the studied lithologies, exhumation must have been coupled with significant cooling, i.e. the resulting P–T path is characterized by a clockwise hairpin loop along low thermal gradients (< 8–9 °C/km); (ii) the presence of ferric iron in the investigated system has a non-negligible (lowering) effect on pressure estimates, whereas temperatures estimates are not influenced by the oxidation state of the system; (iii) the observed sequence of mineral growth (i.e. simultaneous growth of lawsonite and garnet) suggests that (a) the system was initially H 2 O-undersaturated and lawsonite growth was triggered by a protracted H 2 O influx at high pressure (equilibrium approach), or (b) the system was H 2 O-saturated since the beginning, but lawsonite growth was delayed due to the predominance of kinetic factors over equilibrium dynamics (nonequilibrium approach); (iv) the inferred P–T evolution is consistent with a cold subduction zone system in an intra-oceanic subduction setting. Moreover, the estimated peak P–T conditions roughly coincide with the maximum P–T estimates predicted by thermo-mechanical models for the metasediments exhumed in accretionary wedges, and with the maximum P–T conditions recorded by natural occurrences of blueschist accretionary complexes worldwide. [ABSTRACT FROM AUTHOR]

Shear zones are common structures in orogenic belts and elucidation of the tectonic evolution of these orogenic belts to a large degree depends on understanding the kinematics and timing of shear deformation. However, there is a lack of an accurate, fast and convenient way to determine the timing of deformation. In this paper, we apply the ESR (electron spin-resonance spectroscopy) dating method to three syntectonic quartz veins from the Funiushan tectonic belt in the Qinling orogenic belt in central China. The results agree well with the available ages of deformation in the area obtained through other dating methods. This demonstrates the accuracy and feasibility of using the ESR method to date quartz crystals formed during deformation. The method is fast and convenient, and satisfies the accuracy requirement. It is an effective means for determining the timing of deformation, especially in areas with intensive fluid activity during deformation. [ABSTRACT FROM AUTHOR]

The Zhuxi ore deposit is a super-large scheelite (copper) polymetallic deposit discovered in recent years. It grew above copper/tungsten-rich Neoproterozoic argilloarenaceous basement rocks and was formed in the contact zone between Yanshanian granites and Carboniferous-Permian limestone. Granites related to this mineralization mainly include equigranular, middle- to coarse-grained granites and granitic porphyries. There are two mineralization types: skarn scheelite (copper) and granite scheelite mineralization. The former is large scale and has a high content of scheelite, whereas the latter is small scale and has a low content of scheelite. In the Taqian-Fuchun Basin, its NW boundary is a thrust fault, and the SE boundary is an angular unconformity with Proterozoic basement. In Carboniferous-Permian rock assemblages, the tungsten and copper contents in the limestone are both very high. The contents of major elements in granitoids do not differ largely between the periphery and the inside of the Zhuxi ore deposit. In both areas, the values of the aluminum saturation index are A/CNK>1.1, and the rocks are classified as potassium-rich strongly peraluminous granites. In terms of trace elements, compared to granites on the periphery of the Zhuxi ore deposit, the granites inside the Zhuxi ore deposit have smaller δEu values, exhibit a significantly more negative Eu anomaly, are richer in Rb, U, Ta, Pb and Hf, and are more depleted in Ba, Ce, Sr, La and Ti, which indicates that they are highly differentiated S-type granites with a high degree of evolution. Under the influence of fluids, mineralization of sulfides is evident within massive rock formations inside the Zhuxi ore deposit, and the mean SO content is 0.2%. Compared to peripheral rocks, the δEu and total rare earth element (REE) content of granites inside the Zhuxi ore deposit are both lower, indicating a certain evolutionary inheritance relationship between the granites on the periphery and the granites inside the Zhuxi ore deposit. For peripheral and ore district plutons, U-Pb zircon dating shows an age range of 152-148 Ma. In situ Lu-Hf isotope analysis of zircon in the granites reveals that the calculated εHf( t) values are all negative, and the majority range from -6 to -9. The T values are concentrated in the range of 1.50-1.88 Ga (peak at 1.75 Ga), suggesting that the granitic magmas are derived from partial melting of ancient crust. This paper also discusses the metallogenic conditions and ore-controlling conditions of the ore district from the perspectives of mineral contents, hydrothermal alteration, and ore-controlling structures in the strata and the ore-bearing rocks. It is proposed that the Zhuxi ore deposit went through a multi-stage evolution, including oblique intrusion of granitic magmas, skarn mineralization, cooling and alteration, and precipitation of metal sulfides. The mineralization pattern can be summarized as 'copper in the east and tungsten in the west, copper at shallow-middle depths and tungsten at deep depths, tungsten in the early stage and copper in the late stage'. [ABSTRACT FROM AUTHOR]

This paper presents 40 Ar/ 39 Ar and U-Pb age data, Sr-Nd isotopes, whole-rock and mineral compositions of Upper Cretaceous volcanic rocks from the Ordu area of the Eastern Pontide Orogenic Belt (EPOB) in northeastern Turkey. The volcanic rocks exhibit a wide compositional range: basalt, basaltic-andesites, andesites and a rhyodacite suite; they are characterized by subparallel light rare earth element (LREE)-enrichment, relatively flat heavy rare earth element (HREE) patterns with Eu anomalies and moderate fractionation [average (La/Yb)N = 8.55]. The geochemical results show that the volcanic rocks have calc-alkaline affinity consistent with arc volcanic rocks erupted in an active continental margin. Initial 87 Sr/ 86 Sr values vary between 0.70569 and 0.70606, while initial 143 Nd/ 144 Nd values lie between 0.51244 and 0.51249. Crustal contamination affected the mantle-originated primary magma, as indicated by increased 87 Sr/ 86 Sr and decreased 143 Nd/ 144 Nd ratios with increasing SiO 2 . New precise laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) 206 Pb– 238 U age analyses of zircon and 40 Ar/ 39 Ar age data of plagioclase from the volcanics enable a more precise reconstruction of the EBOP. The ages provide insight into the timing of arc formation in this region, constrain the volcanic activity between 86 My (Coniacian) and 75 My (Campanian) and constrain the timing of closure of the Neo-Tethys. [ABSTRACT FROM AUTHOR]

The Jiangnan Orogen is traditionally considered the suture zone, along which the Yangtze and Cathaysia blocks collided to form the united South China Block. There are still major controversies surrounding the pre-collisional tectonic pattern and amalgamation process along the Orogen and the relationship of the united South China Block (SCB) with the Rodinia. Our recent field investigations identified the presence of the volcano-sedimentary unit of the Lengjiaxi Group at Jianxichong, with the thickness of over 1700 m. A set of new zircon U–Pb geochronological, whole-rock elemental and Sr–Nd isotopic data for the metabasites have been obtained and presented in this paper. The layered diabase and tuffaceous samples from the Jianxichong volcano-sedimentary unit yielded the weighted mean ages of 837 ± 5 Ma and 835 ± 6 Ma, respectively. The U–Pb ages of detrital zircons from the phyllite interlayer form a main age-cluster at the peak age of 870 Ma with the youngest apparent age of 845 ± 23 Ma. This indicates that the metabasites in the Jianxichong volcano-sedimentary unit formed at ∼845–835 Ma rather than in the previously-thought Neoarchean in the Central Jiangnan Orogen. The metabasitic samples have SiO 2 ranging from 48.78 wt.% to 53.72 wt.% and MgO from 7.71 wt.% to 12.74 wt.% with mg-number of 63–71, and hence can be classified as tholeiitic basalt and basaltic andesite. They demonstrate a sub-parallel and right-sloping chondrite-normalized REE pattern with slightly negative Eu anomalies and sub-parallel spiky PM-normalized patterns with enrichment in LILEs, depletion in HFSEs and P–Ti negative anomalies, similar to those of arc volcanic rocks. Their ɛ Nd ( t ) values range from −1.64 to −0.37 and initial 87 Sr/ 86 Sr values from 0.7046 to 0.7081, respectively. Such crust-like geochemical characteristics might have been inherited from a sub-arc source modified by fluid/melt released from the subduction sedimentary component. In conjunction with available data and geological observations, we herein propose the development of the early Neoproterozoic (∼840 Ma) continental arc-basin system along the Central Jiangnan Orogen in response to an arc-continent accretionary assembly along the Rodinia exterior. [ABSTRACT FROM AUTHOR]

The paper presents the results of U-Pb geochronological and geochemical studies of the rocks of the monzodiorite-granodiorite association in the northeastern flank of the South Mongolia-Khingan orogenic belt, which composes a tectonic block among the provisionally Lower Paleozoic volcanosedimentary complexes of the Nora-Sukhotinsky Terrane. It is shown that the studied rocks have similar petrographic features (with the presence of transitional varieties) and form common trends in the petrographic diagrams. This suggests that they are members of a single magmatic association. The geochemical features of the monzodiorites, quartz monzodiorites, and granodiorites, in particular their enrichment in large ion lithophile elements (LILE) and depletion in some HFSE, indicate their similarity with island-arc magmatic rocks. The presence of monzonites and quartz monzonites in the studied monzodiorite-granodiorite association along with high K, Rb, Th, and Pb concentrations gives reasons to believe that it formed in active continental margin or ensialic island-arc environments. The granodiorites of the monzodiorite-granodiorite associations of the Nora-Sukhotinsky Terrane are dated at 440 ± 10 Ma and may be considered as a fragment of the early Silurian active continental margin or ensialic mature island arc in the structure of the South Mongolia-Khingan orogenic belt. [ABSTRACT FROM AUTHOR]

Petrographic and geochemical data obtained on the Araguainha impact crater (Goiás/Mato Grosso States, Brazil) indicate the existence of several molten products that originated during impact-induced congruent melting of an alkali-granite exposed in the inner part of the central uplift of the structure. Although previous studies have described these melts to some extent, there is no detailed discussion on the petrographic and geochemical variability in the granite and its impactogenic derivatives, and therefore, little is known about the geochemical behavior and mobility of trace elements during its fusion in the central part of the Araguainha crater. This paper demonstrates that the preserved granitoid exposed in the core of the structure is a magnesium-rich granite, similar to postcollisional, A-type granites, also found in terrains outside the Araguainha crater, in the Brasília orogenic belt. The molten products are texturally distinct and different from the original rock, but have very similar geochemical composition, making it difficult to separate these lithotypes based on concentrations of major and minor elements. This also applies for trace and rare earth elements ( REE), thus indicating a high degree of homogenization during impact-induced congruent melting under high pressure and postshock temperature conditions. Petrographic observations, along with geochemical data, indicate that melting occurs selectively, where some of the elements are transported with the melt. Simultaneously, there is an effective dissolution of the rock (granite), which leads to entrainment of the most resistant solid phases (intact or partially molten minerals) into the melt. Minerals more resistant to melting, such as quartz and oxides, contribute substantially to a chemical balance between the preserved granite and the fusion products generated during the meteoritic impact. [ABSTRACT FROM AUTHOR]

This paper presents the first report of the coexistence of tholeiitic mid-ocean ridge basalt (MORB) – type and alkaline ocean island basalt (OIB) – type mafic volcanics from the Manipur Ophiolite Complex (MOC), Indo-Myanmar Orogenic Belt, northeast India. The MORB-types have comparatively lower TiO 2 concentrations (0.6–1.6 wt.%), show almost flat REE patterns with depleted LREEs [(La/Sm) N = 0.62–1.03]. However, few samples in the MORB group show enrichment in LREE [(La/Sm) N = 2.83–2.95] which is the typical composition of P-MORB. Alkaline OIB-types are characterized by high concentration of TiO 2 (1.7–3.5 wt.%) with highly enriched LREE pattern as compared to their HREE [(La/Sm) N = 2.27–3.44, (Sm/Yb) N = 2.56–3.29]. Such geochemical variation implies more than two sources. Possibly, one for OIBs (enriched mantle) and several ones for MORBs; from depleted MORB mantle (DMM) source to significantly enriched DMM source by OIB-type components. Petrogenetic modeling suggests that 20% partial melting of depleted mantle within spinel stability facies zone (shallow depth) is responsible for generation of MORB tholeiites and 5–10% partial melting of enriched mantle or plume material at garnet facies stability zone (deeper depth) is responsible for production of alkaline OIB-type. Geochemical signatures of variably enriched MORB and P-MORB samples further suggest possible scenario of mixing of depleted N-MORB and enriched OIB melt. It is therefore likely that mafic volcanics of the MOC were derived from chemically heterogeneous mantle sources erupted at the sea floor spreading zone as MORB generated by partial melting of depleted upper mantle and as OIB generated by partial melting of enriched mantle or a plume source, which was proximal to the spreading axis. Later, due to prolonged subduction of the Indian plate beneath the Myanmar plate and afterward collisional activity, they might have accreted along the Indo-Myanmar Orogenic Belt as upthrust ocean crust. [ABSTRACT FROM AUTHOR]

This paper investigates the petrogenesis of the Xinxian granitic batholith and its tectonic implications for the Dabie orogen. Two Xinxian granites yield Early Cretaceous U/Pb ages of 122.7 ± 1.3 Ma and 123.6 ± 2.2 Ma. The granites are metaluminous differentiated I-type granites, with A/NKC ranging from 0.90 to 0.96. The chondrite-normalised REE patterns display significant LREE/HREE enrichments with moderate negative Eu anomalies (Eu/Eu = 0.30 ~ 0.85). The granites show enrichments in large-ion lithophile elements (LILEs, e.g. Rb, K, Th and U) and depletions in Sr, Ba and high field strength elements (HFSEs, e.g. Nb, Ta and Ti). Inherited zircons of different age (Neoproterozoic, one Early Proterozoic, one Archean and two Triassic inherited metamorphic zircons) are identified. The Early Cretaceous magmatic zircons contain enriched Hf isotopes with ε ( t) values ranging from −26.9 to −18.7 (average = −22.5), more enriched than their probable alleged source, i.e. the Dabie Complex, represented by the Neoproterozoic and Triassic inherited zircons. Thus, the Archean and Early Proterozoic crustal materials may represent an enriched end member source for the parental magma of the Xinxian granites. Provenance analysis of the magmatic zircons in the North China and Yangtze blocks demonstrates that the Early Proterozoic inherited zircon in Xinxian has North China affinity. Thus, we proposed a multiple-sourced petrogenetic model for the Xinxian granitic batholith, which suggests that the batholith was formed by the remelting of a mixed crustal assemblage, including the Archean and Early Proterozoic crust of the North China Block, the Neoproterozoic crust of the Yangtze Block, as well as some Triassic collision-related ultra-high pressure (UHP) metamorphic rocks. [ABSTRACT FROM AUTHOR]

The Pieniny Klippen Belt (PKB) is a narrow, discontinuous zone rich in olistostromes and olistoliths (Klippen) in the western Carpathians. This paper, based on prior works including tectonic and stratigraphic evidences, suggests that the PKB rocks were deposited from the Triassic to the Early Paleogene along the eastern footwall of a major Split–Karlovac-Initial PKB-Crustal-Zone (SKICZ) paleotransform fault zone. This transform fault was then separating the continental crust of the Austro-Alpine zone in the west and a Carpathian Embayment Ocean in the east. It was only during the Late Paleogene–Early Miocene that the PKB rocks were integrated into the accretionary prism that formed at the front of the eastward-extruded ALCAPA units. This interpretation therefore supports the existence of a major paleotransform fault zone in the Neo-Tethys during the Triassic–Early Paleogene. This paleotransform had been previously suggested to explain the observed reversal in obduction and subduction at the junction between the eastern–southern Alps and the Carpathians–Dinarides. [ABSTRACT FROM AUTHOR]

The Yenisei Ridge was traditionally perceived as an uplifted segment of the western Siberian craton affected by Neoproterozoic collision events. However, the suggestions for Archaean or Palaeoproterozoic (‘Siberian’) basement in Transangaria have not been confirmed by reliable geochronological data. A new view regards most of the Ridge, namely, its Transangarian segment, to be an exotic Neoproterozoic terrane that collided with Siberia in the late Neoproterozoic. This paper presents new U–Pb SHRIMP zircon ages demonstrating that Archaean rocks (2611 ± 12 Ma) actually exist in this territory. We also provide a review of published U–Pb zircon ages for igneous and metamorphic rocks of Transangaria together with our new age data. This geochronological dataset clarifies the geology of the Yenisei Ridge and leads to new conclusions, as follows. (1) It is likely that Transangaria was originally underlain by an Archaean–Palaeoproterozoic basement, similar to that of the Siberian craton. (2) Geochronological data do not confirm the idea of widespread “Greenvillian age” granitoides in Transangaria. (3) The Neoproterozoic evolution of the Yenisei Ridge segment of the Siberian craton margin includes the following events. (i) Collision of an unidentified terrane with the western margin (in recent coordinates) of the Siberian craton during 900–855 Ma. The colliding terrane is no longer present in the current structure. (ii) Dextral shearing during 830–800 Ma may have been caused by counter-clockwise rotation of the Siberian craton. (iii) Extensional conditions prevailed during 800–700 Ma. The Isakovka oceanic basin formed at this time interval. (iv) Thrusting of the Isakovka island arc and accretionary prism onto the Siberian margin occurred during the late Neoproterozoic (650–630 Ma) and caused high-pressure metamorphism. [ABSTRACT FROM AUTHOR]

Geophysical data allowed the construction of a ~250-km-long lithospheric-scale balanced cross section of the southern Black Sea margin (Espurt et al. in Lithosphere 6:26-34, ). In this paper, we combine structural field data, stratigraphic data, and fault kinematics analyses with the 70-km-long onshore part of the section to reconstruct the geodynamic evolution of the Central Pontide orogen. These data reveal new aspects of the structural evolution of the Pontides since the Early Cretaceous. The Central Pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults. Extensional subsidence occurred with an ENE-trend from Aptian to Paleocene. We infer that the Black Sea back-arc basin also opened during this period, which was also the period of subduction of the Tethys Ocean below the Pontides. As in the Western Pontides, the Cretaceous-Paleocene subsidence was interrupted from Latest Albian to Coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone. The restoration of the section to its pre-shortening state (Paleocene) shows that fault-related subsidence locally reached 3600 m within the forearc basin. Structural inversion occurred from Early Eocene to Mid-Miocene as a result of collision and indentation of the Pontides by the Kırşehir continental block to the south, with 27.5 km (~28 %) shortening along the section studied. The inversion was characterized by NNE-trending shortening that predated the Late Neogene dextral escape of Anatolia along the North Anatolian Fault and the modern stress field characterized by NW-trending compression within the Eocene Boyabat basin. [ABSTRACT FROM AUTHOR]

Permian mafic-ultramafic intrusions in or besides the Central Asian Orogenic Belt (CAOB) have been the focus of several recent studies, mainly located in Altay, East Tianshan, and Beishan Rift from north to south. Some of them host economic magmatic sulfide deposits. Among those, Poyi is a large magmatic Cu-Ni sulfide deposit related to ultramafic rock in Beishan Rift. Poyi does not have massive ore, but only disseminated ore in hornblende-peridotite, so Poyi is not as rich as the Karatongk Cu-Ni deposit in the Altay area or the Huangshandong and Tulargen Cu-Ni sulfide deposits in Eastern Tianshan. To address these questions, this paper contrasts the feature of PGE (Platinum Group Element) and olivine composition in magmatic Cu-Ni deposits between three regions (Altay, East Tianshan, and Beishan Rift) to provide a view of the metallogenic process of the Poyi magmatic Cu-Ni deposit. The degree of sulfide segregation (DSS) of Poyi is around 0.01%; the value of R (the ratio of the mass of silicate magma to the mass of sulfide that reached equilibrium together) is 500-5000, and is 2333 on average; the R value of Cu-Ni sulfide deposits in East Tianshan is in the range of 100-500, and the degree of sulfide segregation is about 0.013%; Poyi Cu-Ni deposit is not as rich as the magmatic Cu-Ni deposits in East Tianshan, probably because the degree of sulfide segregation of the former (0.01%) is lower than that of the latter (0.013%). From Beishan area to East Tianshan and then to Altay Region, the R value changed from 2333 to 100-500 and then to 100 according to the theory of Naldrett (2011). Poyi does not have the potential to be a PGE deposit. The olivine of Poyi has higher contents of MgO and SiO and lower contents of FeO and CaO, which reach sulfur saturation more easily, but due to the lack of sulfur, it is still very difficult to reach sulfur saturation, and therefore the olivine of Poyi has the highest Ni content among the Permian magmatic Cu-Ni deposits in Xinjiang. [ABSTRACT FROM AUTHOR]

In this paper we present new data for the metamorphic Garm Block (150 × 40 km) that was traditionally shown on regional maps as fragment of a Precambrian basement. The Garm Block comprises migmatized gneisses and schists for some of which peak metamorphic conditions (600–660 °C at 7–9 kbar) characteristic for medium P/T series metamorphic belts were determined. U–Pb ages of overgrown rims of zircon grains and newly grown magmatic zircon grains from four migmatitic samples indicate that melting occurred during peak metamorphic conditions between 299 and 290 Ma. Thus the Garm Block is the first Early Permian regional metamorphic terrane established in the southern part of the Central Asian Orogenic Belt. A crosscutting granite intrusion yields a concordia age of 290 Ma identical to the age of metamorphism and similar to ages of post-collisional intrusions elsewhere in the Tien Shan. Detrital zircon grains from the Garm samples yield an age spectrum with major peaks at 700–550 Ma and 1150–700 Ma, and smaller ones at ca. 2.7–2.4 Ga and 3.5–3.3 Ga. The youngest grains define an Ediacarian maximum depositional age of the sedimentary protoliths. The presence of Grenvillian ages of 1150–800 Ma, which are characteristic for the Tarim Craton, and the lack of ca. 1.6–1.2 Ga ages, characteristic for the Northern Tien Shan, suggest an origin of the Precambrian zircon grains from southern continental blocks similar to the Tarim Craton. Six granitoid samples yield negative εNd values of −10.6 to −3.7 consistent with the reworking of crustal material with 1.8–1.1 Ga average crustal residence times and the formation of the South Tien Shan belt on a continental basement with Paleoproterozoic or older crust. The Garm Block formed as a consequence of lithospheric thickening during the Late Carboniferous collision of two continental blocks that created the South Tien Shan fold belt. Lateral crustal melt flow coupled with extension may have resulted in exhumation of the Permian metamorphic rocks. [ABSTRACT FROM AUTHOR]

The thermal water ecosystem of Diyadin (Agri region) is poorly known in terms of biodiversity, as only few bacteria species were identified and some of their specific enzymes were isolated. However, the geological structure of this old inactive volcanic zone as well as the chemical composition of the thermal water characterized by therapeutic properties and temperatures up to 64°C were thoroughly studied. Diyadin zone has been insufficiently capitalized from the tourist and industrial viewpoints so far, but the discovery of some gold deposits seems to revitalize its economy. The present paper is the first one dedicated to the ciliates living in surface thermal waters; 9 species have been identified till present. The data are preliminary and they will be completed with other data after the inventory of other protozoa and metazoa species, which could represent new taxa or varieties of the species originating in the Murat River and adapted to the special abiotical factors of this ecosystem. [ABSTRACT FROM AUTHOR]

Once situated between the Central Tianshan and Junggar terranes during Paleozoic time, the Junggar Ocean was a major southern branch of the Paleo-Asian Ocean. Thus, when and how it was closed are essential in understanding the final assembly of the Central Asian Orogenic Belt. However, the exact closure time of the Junggar Ocean remains unresolved due to the lack of reliable timing of collision-related regional metamorphism. This paper reports whole-rock geochemical and zircon U–Pb and Lu–Hf isotopic data for granitic gneisses from the northern margin of the Central Tianshan block, which can provide crucial constraints on the final closure of the Junggar Ocean. Mineral assemblages and geochemical suggest that the protoliths of the Central Tianshan gneisses are weakly peraluminous high-K calc-alkaline I-type granites, possessing typical subduction-related features such as strong enrichment in LREE and LILE and depletion in HFSE. Negative Eu anomalies (δEu = 0.46–0.81) and highly variable zircon Hf isotope compositions indicate various amounts of residual plagioclase in the source and crustal contamination during magma formation. LA-ICPMS U–Pb dating on magmatic-type zircons (72%), characterized by euhedral to subhedral shapes, concentric oscillatory zoning, high Th/U ratios (0.30–2.05) and large ranges of ε Hf (t) values (− 3.4 to + 8.7; up to 6 epsilon units in each sample), yields consistent weighted mean 206 Pb/ 238 U ages of ca. 325–320 Ma, interpreted as the crystallization ages of the granitic protoliths. Geochemical signatures and dominantly positive zircon ε Hf (t) values reveal that the protoliths were emplaced in a continental arc setting, pinpointing the development of a late Early to early Late Carboniferous continental arc system on the northern margin of the Central Tianshan block, probably related to the southward subduction of the Junggar oceanic plate. Meanwhile, younger ages at ca. 303–301 Ma were obtained on recrystallized zircon-rims and unzoned/homogeneous zircons (25%) with narrow ranges of ε Hf (t) values (− 1.8 to + 7.2; < 3 epsilon units in each sample), considered as the timing of a later tectonothermal event, which was associated with strong deformation that formed the gneissosity of the granitic gneisses. Combined with previous studies, we suggest that this event most likely resulted from the arc–continent collision/accretion between the island arcs (e.g. Bogda, Dananhu) in the Junggar Ocean and the Central Tianshan block during the final closure of the Junggar Ocean, which led to the final assembly of the Eastern Tianshan during the latest Carboniferous time. [ABSTRACT FROM AUTHOR]

V. Ngako and E. Njonfang addressed in their comment an interesting and debated issue about the collision geodynamics of the Pan-African Central African Orogenic Belt (CAOB) in Cameroon. However, the reason for this comment is still not clear to us since it mainly deals with issues far away from the scope of our study, namely, the pre-collisional set up of the belt. The comment raises two main points – the reworking process during plate collision and the Pan-African strain pattern – not discussed in our paper for the simple reason that it was not our goal and because our data set does not even allow such discussion. Having said that, the comment gives us the opportunity to clarify our view on the nature of the Adamawa-Yade domain (Central Cameroon) and the early evolution of the CAOB. We will successively discuss two other points raised in the comment: (1) our Fig. 12 depicting a possible pre-collisional configuration at the northern and southern margin of the Congo craton in the Early Neoproterozoic, and (2) the nature and extent of the Adamawa-Yade domain. [ABSTRACT FROM AUTHOR]

The Río Damas Formation is an Upper Jurassic volcano-sedimentary succession, whose outcrops are largely distributed between 33°S and 35.30°S in Chile and Argentina, as part of the retroarc Neuquén Basin fill. This unit was deposited during an important marine regressive phase of the basin. We studied the Río Damas Formation exposures at the Los Gateados creek valley, in the Alto Atuel depocenter (34°40′S; westernmost Malargüe fold and thrust belt), next to the Argentinean-Chilean border. This area represents a key location where the formation interdigitates with the nonmarine red beds of the time equivalent Tordillo Formation, representing a continentalization episode of the Neuquén Basin. This paper presents a lithofacial characterization of the Río Damas Formation, a new U–Pb igneous crystallization age, and a paleographic reconstruction for this period. The Río Damas Formation in the Alto Atuel depocenter consists of porphyritic basaltic and andesitic lavas, interbedded with fine-grained sandstones, conglomerates, volcanic lithic breccias, and pyroclastic deposits. Based on field and petrographic analyses, we associate the Río Damas Formation with a piedmont environment where sedimentary fluvial and alluvial setting coexisted with volcanic effusive and pyroclastic activity. A regional comparison of the Río Damas and Tordillo Formations along the Argentinian-Chilean border shows that the composition and thickness of these units present important latitudinal and longitudinal variations. The increase in thickness and the volcanic component of the Río Damas Formation towards the west could be associated with the proximity to the Jurassic magmatic arc. • The Río Damas Fm. is a volcano-sedimentary unit outcropping at 33°-35.30°S in Central Andes. • We present the first Late Jurassic U–Pb igneous crystallization age for the unit. • Volcanism include lava flows, dykes and pyroclastic rocks associated with lahar deposits. • Regionally, lithofacial and thickness variations in latitude and longitude are recognized. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Subashi ophiolite in West Kunlun Orogenic Belt was formed at ca. 455–446 Ma. • Geochemical features indicate the Subashi ophiolite formed in a MOR setting. • Mazha-Kangxiwa mélange zone with Subashi ophiolite marks a Proto-Tethys suture. The West Kunlun Orogenic Belt (W-KOB) in the northwestern Tibetan Plateau retains critical information about the tectonic evolution of the Proto- and Paleo-Tethys during the Early Paleozoic to Mesozoic. Although a trench-arc-back arc basin model was used to address the tectonic evolution of Proto-Tethys, records about the evolution of this ocean basin remain ambiguous, particularly no studies about ages and tectonic affinities of ophiolites in the W-KOB are available. In this paper, we present new results on whole-rock elemental and Sr-Nd isotopic composition of basalts, and U-Pb zircon ages of gabbro, diabase and basalt from the Subashi ophiolite. The basalts are characterized by low REE concentrations, depleted LREEs in the chondrite normalized REE patterns, and unfractionated HFSEs in the primitive mantle normalized trace element spider diagrams, resembling normal mid-ocean ridge basalts. They have constant 87Sr/86Sr(i) values of 0.70472–0.70590 and positive ε Nd values of +7.5 to +7.9. Accordingly, it can be concluded that the Subashi ophiolite was derived from a depleted spinel lherzolite mantle source in a mid-ocean ridge setting. Zircon grains separated from basalt, diabase and gabbro have 206Pb/238U ages of 455 ± 4 Ma, 451 ± 6 Ma, and 446 ± 6 Ma, respectively, which are taken to be the crystallization ages of these rocks. Together with previously published data, our new data propose that the Mazha-Kangxiwa-Subashi ophiolitic mélange zone marks the existence of the Proto-Tethys ocean basin during the Early Paleozoic. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grenville-age terrane is identified in the Qilian orogen. • The Precambrian basement of the Qilian orogen is divided into four distinct mega-sequences. • ∼475 Ma metamorphism was related to the subduction of the Proto-Tethys Ocean. The Qilian orogen at the northeastern margin of the Tibetan Plateau records a complete history from continental breakup to oceanic basin evolution and back to continental collision during the Neoproterozoic to Paleozoic interval. The Qilian Ocean, as a branch of the Proto-Tethys Ocean, was connected to the Iapetus Ocean but is lesser known than its two more famous counterparts. This paper presents zircon U-Pb and biotite-muscovite 40Ar/39Ar isotope data from the Yemananshan Complex in the western Central Qilian belt to assess the age and provenance of late Mesoproterozoic-early Paleozoic successions in the Qilian orogen. The results indicate the Central Qilian belt is characterized by Late Mesoproterozoic-early Neoproterozoic orogenesis with magmatism from 1200 Ma to 900 Ma and clastic metasedimentary rocks deposited between 1050 and 920 Ma. Statistical analysis of detrital zircon data and auxiliary temporal information from the Qilian orogen affirms the notion that sedimentation occurred in four distinct megasequences: (1) 1950–1850 Ma, the oldest known strata, (2) 1250–920 Ma, during Grenvillian-Sveconorwegian orogenesis, (3) 840–760 Ma, the disintegration of Rodinia, and (4) 650–550 Ma, which is typical of the orogenic belts that sutured the Gondwana continental blocks. Metamorphic zircon and 40Ar/39Ar isotope data indicate early Paleozoic metamorphism at ca. 475 Ma, which overlaps with magmatic activity associated with arc-back-arc basin development in the Central Qilian belt, which was associated with subduction of the Proto-Tethys in eastern Gondwana. [ABSTRACT FROM AUTHOR]

Adakites with continental origin have K-rich compositions distinctive from the sodic, subduction-related adakites and are generally considered as partial melting products of thickened mafic lower crust at high pressure conditions (above 1.5 GPa; >50 km depth). In order to compare the geochemical differences and to constrain their source compositions and partial melting conditions, we compiled published data for the sodic adakites related to subduction processes in the Central Asian Orogenic Belt (CAOB) and the potassic adakite-like rocks related to continental collision in the Lhasa Terranes (LT) of the Tibetan Plateau. Based on the spatial similarity of Sr-Nd isotopes and nature of inherited zircons, the origin of the CAOB sodic adakites is best explained by fluid-fluxed melting of low-K arc basalts, while the LT potassic adakites are best explained as generated by fluid-fluxed melting of rocks similar to the voluminous high-K Linzizong mafic volcanic successions (LVS). The phase equilibria and trace-element modeling reveal that these low Mg# mafic sources would expand garnet stability to pressures as low as 7-8 kbar and fluid-fluxed melting (X(H 2 O) = 2-3 wt%) would significantly decrease the modal content of plagioclase, resulting in melts with "high pressure" signature (e.g., high Sr/Y and La/Yb). This paper provides an alternative model for the origin of sodic or potassic continental adakites arguing that they originate from fluid-fluxed melting at garnet amphibolite facies at normal lower crustal pressures (10-11 kbar). Our findings highlight the importance of the source composition and fluid content in generating the "high pressure" signatures of adakites, which may also explain the origin of Archean tonalite-trondhjemite-granodiorites (TTGs). • Both sodic and potassic continental adakites originate from fluid-fluxed melting. • The adakites generation at normal lower crustal pressures (10-11 kbar). • The source composition and fluid content control the "high pressure" signatures of adakites. [ABSTRACT FROM AUTHOR]

The Paleo-Asian Ocean eventually closed along the Solonker Suture Zone during the Late Permian and Early Triassic, before the collision between the Siberian Craton and the North China Craton (NCC) formed the eastern Central Asian Orogenic Belt (CAOB). In this paper, Magnetotelluric (MT) profile data across the south-eastern CAOB and the northern margin of the NCC are explored to image the two-dimensional resistivity structure of the region. According to the resistivity model, a north-dipping conductive layer to the north of the Xilinhot fault and a south-dipping conductive layer to the south of the Linxi fault are revealed. The two conductors are interpreted as evidence of the late-stage low-angle bidirectional subduction of the Paleo-Asian Ocean, which constrains the northern and southern deep boundaries of the Solonker Suture Zone. Another couple of mantle conductors with opposite dipping angles are revealed under the Solonker Suture Zone and Bainaimiao Belt, which are interpreted as evidence of the early-stage high-angle bidirectional subduction of the Paleo-Asian Ocean. Compared with the results from previously reported MT profiles in this area, the subduction angle becomes more gentle from west to east. The difference of convergence rate between the NCC and the Siberian Craton is considered to be the major cause of the closure difference along the strike. The northern margin of the NCC has a conductive lower crust, which may result from the magma underplating or crust-mantle decoupling, as it is imaged to be connected with the south-dipping conductive layer beneath the Solonker Suture Zone. [ABSTRACT FROM AUTHOR]

Coupling of deformation and magmatism has been widely reported in several old orogenic belts, particularly along faults and shear zones. The syn-kinematic plutons in exhumed shear zones offer the best opportunity to understand the complex relationship between magmatism and regional deformation. The present paper investigates the geometry and internal structure of granite plutons emplaced in thrust faults and shear zones, and structural control on their emplacement mechanism. Abu Ziran pluton is an example of the intrusions emplaced in an active brittle-ductile thrust shear zone in the Nubian shield, and documents clear evidence on the interaction between magmatism and deformation during melt ascent and emplacement. Results from detailed geological mapping, remote sensing and structural analysis of the pluton permitted the constraining of the pluton's geometry, emplacement mechanism, and spatio-temporal evolution. Structural analysis indicates that pluton emplacement was syn-to-late-tectonic. The brittle-ductile fabrics in the wall rock are consistent with a sub-horizontal thrust shear zone with a top-to-NW shear sense. The activity of the shear zone was accompanied by an episode of a calc-alkaline magmatic pulse. Granitic magma ascended upward via non-exposed feeder dykes, or through ramps and flats in the thrust system and emplaced laterally along the shear zone, forming complex sub-horizontal sheet-shaped intrusion. The geometry and extent of pluton emphasize that inherited heterogeneities and regional stress states played important role in the emplacement processes. In addition, localization of pluton along or near the contact between ophiolitic nappes and mylonitic metasediments suggests that the rheological boundaries act as barriers that impede the rise of ascending magma, causing magma arrest and trigger lateral spreading and emplacement. The outcomes of this study allowed the reconstruction of the geometry and internal structure of Abu Ziran pluton and grasping its evolution in space and time. • Exhumed thrust shear zones documents a coupling of magmatic and deformational processes. • Plutons emplaced in shear zones have a distinctive tabular or sheet-shaped geometry. • Inherited structures and stress states play a significant control on the room required for magma emplacement. • Rheological boundaries in the orogenic belts act as a trap for ascending melt. • Syn-kinematic plutons record a spectrum of microstructures ranging from magmatic to solid-state fabrics. [ABSTRACT FROM AUTHOR]

The Sohar Basin, located offshore the East Coast of the Arabian Peninsula, is an area that has seldom been the focus of international oil companies. While all commercial discoveries in the UAE and Oman have been made to the west and south of the Oman Mountains, the Sohar Basin is underexplored and remains prospective. This lack of activity is primarily because the Thamama reservoir, which has yielded huge success to the west of the Oman Mountains is likely not present within the Sohar Basin. However, potential traps, reservoirs, and source rocks are present within the Tertiary succession. The Sohar Basin formed in the late Cretaceous after the obduction of the Semail Ophiolite onto the Arabian Plate. Following a period of tectonic quiescence, which lasted until the Early Eocene, the gravitational collapse occurred along the eastern edge of the present-day Oman Mountains. Interpretation of both 2D and 3D seismic reveals that the subsurface is comprised of three tectonostratigraphic units, defined as pre-, syn-, and post-tectonic packages. North-South trending thrust faults generate distinct mini-basins within the pre- and syn-tectonic sequences. The post-tectonic sequence is defined by the development of prograding systems in a tectonically quiescent margin formed in the Lower Miocene and which persists to the present day. Deep-water depositional systems dominate the undrilled far-east and south of the basin where the presence of submarine canyon systems and associated basin floor fans is supported by 3D seismic data. In recent times, the Sohar Basin has been subject to extensional faulting likely driven by sediment load caused by a prograding delta system. The results of this work reveal that multiple untested play types exist within the Sohar Basin, which are comprised of both structural and stratigraphic elements. This paper integrates both a structural and sequence stratigraphic interpretation to provide insights into the tectonostratigraphic evolution of the Sohar Basin. Consequently, the fundamentals of play fairway mapping have been employed to unlock the hydrocarbon prospectivity offshore the UAE's East Coast. • A sequence stratigraphic approach unlocks the prospectivity in the Sohar Basin, offshore the east coast of the UAE. • Untapped prospectivity lies within deep marine turbidities within the Northern Sohar Basin. • Toe thrust systems have developed in response to post orogenic collapse of the Hajar Mountains. • A passive continental margin developed during the Miocene within the Northern Sohar Basin. [ABSTRACT FROM AUTHOR]

Oroclines are features of orogenic belts that exhibit curvature in plan on a map scale, with the additional requirement that this curvature resulted from relative rotation of the limbs around a vertical or near-vertical axis. Much debate has centred on contrasts between thin-skinned and thick-skinned systems, and on the question of whether the structural fabric was imposed prior to or synchronous with the development of curvature, leading to a variety of inconsistent terminology. A simple hierarchy, in which all map-scale curved orogenic features which pass a test for rotation are termed oroclines (as distinct from primary arcs), and in which these are then subdivided by timing into progressive (synchronous fabric and curvature) and secondary (pre-existing fabric is then rotated), and by mechanism into thin- or thick-skinned, is applied to a suite of curved orogenic features in the Tasmanides of eastern Australia. This analysis includes the first formal application of the “orocline test” (palaeomagnetic or palaeocurrent directions plotted against structural strike) to the Tasmanides. The Neoproterozoic to early Mesozoic Tasmanides comprise four orogens, each of which contains curved orogenic features which are highlighted by extensive aeromagnetic datasets. The Delamerian Orogen, developed on the Gondwana margin, exhibits two curved structures in the Neoproterozoic to Cambrian Adelaide Fold Belt, termed the Fleurieu and Nackara arcs: previous structural interpretations have indicated that the Nackara Arc is non-rotational, and hence not oroclinal. Re-examination of existing palaeomagnetic data, including a positive palaeomagnetic orocline test, shows the Nackara Arc to in fact be a hinge of the Adelaide orocline. Curvature in the Adelaide orocline was dominantly progressive and thin-skinned, but may have been influenced by secondary rotation of the pre-existing, partly underlying Curnamona Craton. Mega-kinks in a buried Delamerian arc-volcanic chain revealed in aeromagnetic images follow the curvature of the Nackara Arc, suggesting an accompanying thick-skinned, secondary oroclinal deformation further from the continental margin. Orogenic curvature in the Palaeozoic Lachlan Orogen has only been widely recognised since the advent of tilt-filtered aeromagnetic images, and a model of oroclinal folding with two hinges (Riverina and Tambo) and strike-slip offset during the Silurian Bindian orogeny has recently been proposed to explain perplexing repetitions of sequence and inversions of structural vergence and directions of sediment provenance. Palaeomagnetic data indicates rotation of elements within the proposed orocline, and a preliminary study indicates a positive palaeomagnetic orocline test for the Riverina hinge. Palaeocurrent data around the Tambo hinge provide a positive, if scattered, orocline test. An independently conceived numeric model of the roll-back response to congestion of a subduction zone has generated an oroclinal structure which shares many features with the proposed Lachlan orocline, and deep crustal ambient-noise seismic data confirms that the major curved and strike-slip features persist throughout the crust. The Lachlan orocline appears to be secondary and thick-skinned. Orogenic curvature in the largely covered Thomson Orogen occurs along its southern border with the Lachlan Orogen (the putative Olepoloko orocline) and around its geometrically complex boundary with the Mossman Orogen in northern Queensland (the Charters Towers orocline). Rotation of the Olepoloko structure cannot be confirmed, and competing models for its formation leave open the question of whether this is a primary arc, a thin-skinned progressive orocline, or a thick-skinned secondary orocline. Palaeomagnetic data from the Charters Towers orocline are limited to two poles, but a change in declination between the Silurian pole and the Devonian pole matches the apparent rotation of the orocline, which appears to have been thick-skinned and secondary. In contrast to the other orogens, consensus that at least part of the curvature in the Palaeozoic to Triassic New England Orogen is oroclinal has been broad, although not universal. There remains substantial debate over the number of hinges (from two to four) and mechanism. Palaeomagnetic poles have previously been cited as evidence of rotation of blocks within the orocline, but this paper presents the first formal palaeomagnetic orocline test, which is positive for the Manning and Texas hinges. A palaeocurrent orocline test of the Manning hinge, in younger rocks than the palaeomagnetic sample, is negative, constraining rotation in the southern, Manning hinge to the Carboniferous before 322 Ma, while rotation in the northern, Texas hinge appears to be latest Carboniferous or Permian. The existence of a Hastings hinge is questionable, but if real, its rotation also appears to be younger than that of the Manning hinge. Thick-skinned, secondary rotation of the hinges of the New England orocline appears to have been diachronous. [ABSTRACT FROM AUTHOR]

The fold-and-thrust belt in the eastern Sichuan basin is represented by a series of subparallel chevron anticlines. Under the orogenic tectonic setting within the South China Block in Meso-Cenozoic period and the influence of the multi-layer detachment fault, the deformation of the thrust belt exhibits remarkably layered and large-scale intracontinental thrusting structural characteristics. In this paper, we focus on the structural geometry and deformational mechanisms using the latest two-dimensional (2D) and three-dimensional (3D) seismic reflection data in combination with well and outcrop data. The multi-layer detachment faults, especially the upper gypsum-bearing detachment in the Middle Triassic Jialingjiang Formation and lower detachment with gypsum or shale in the Lower–Middle Cambrian system, directly control the deformational styles of the study area. Interpretation of seismic sections indicates that the fold-and-thrust belt has various deformational styles during folding, including fault-propagation fold, fault-bend fold, and detachment fold with box-fold or pop-up structural geometry. Regional location and structural boundaries play significant roles in controlling the deformational styles, and distinct differences exist among the different anticlines. The Huayingshan anticline located at the front of the thrust belt shows intense structural deformation with northwestward thrusting direction and a relatively weak opposite southeastward thrusting. In addition, the anticlines exhibit structural differences along strike and the fold-and-thrust belt in the northern segment is influenced by the North China Block. [ABSTRACT FROM AUTHOR]

The closure time of the Junggar Ocean is one of the hottest topics surrounding the tectonic evolution of the Central Asian Orogenic Belt (CAOB). This paper reports SIMS zircon U–Pb ages of the ophiolitic mélange and collisional igneous rocks in the Zhifang area, East Junggar. Our new results reveal the following evidence: (1) the West Hill ophiolitic mélange in the Zhifang area contains segments of the 371 Ma MORB-type layered rocks and 363 Ma oceanic islands, which were intruded by the 348 Ma syn-collisional quartz diorites; (2) the ophiolitic mélange and 348 Ma syn-collisional quartz diorites are overlain by the 342 Ma andesitic tuffs; and (3) the 342 Ma andesitic tuffs and successive 332 Ma granodiorites-gabbro were formed at late-collisional setting, whereas the 314 Ma granitic porphyry at post-collisional setting. We suggest that the Junggar Ocean in the Zhifang area was opened before 371 Ma and 363 Ma, and possibly closed before 348 Ma. By combining the published U–Pb ages of the Mayile–Tangbale–Darbute–Kalamaili–Zhifang–Daheishan (MTDKZD) ophiolite belt, Early-Carboniferous volcanic rocks unconformably overlying the MTDKZD ophiolite belt, bimodal volcanic rocks and granitoids within and adjacent to the MTDKZD ophiolite belt, it is suggested that the Junggar Ocean was possibly opened scissors-like from the Neoproterozoic–Ordovician Mayile–Tangbale ocean eastwards through the Silurian–Devonian Darbute–Karamay ocean finally to the Devonian–Early-Carboniferous Kalamaili–Zhifang ocean, and closed scissors-like from the Zhifang–Kalamaili area in the eastern segment westwards to the Darbute–Karamay area in the western segment. Tectonic collage between the Yemaquan–Xiemisitai arc and Junggar block occurred at approximately 343–348 Ma. The Junggar orogenic belt went through late-collisional stage at 343–330 Ma, post-collisional period after 330 Ma, and post-collisional extensional regime after 320 Ma with an intensive stage at around 303 Ma. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of active tectonics on the geomorphic processes and landscape evolution along the Kazerun Fault Zone (KFZ) in the Zagros Mountains of Iran using spatial analysis of geomorphic indices. We document how topography and morphology are influenced by active tectonic deformation. The Zagros fold-thrust belt is an area of active crustal shortening where northwest-southeast oriented fault-related folds become younger from north to south and from southeast to northwest. This temporal and spatial evolution of the belt was tested using geomorphic indices of active tectonics that include mountain front sinuosity index (Smf), the valley width/height ratio (Vf), drainage basin asymmetry factor, hypsometric integral, drainage basin shape ratio and mean axial slope of the channel. Change in the geomorphic indices is the result of active fold growth and change in the uplift rate. Decreasing Smf and Vf values from north (Smf=2.01; Vf=0.5) to south (Smf=1.12; Vf = 0.2) and from southeast (Smf=1.84; Vf = 0.8) to northwest (Smf=1.54; Vf=0.1) points to a migration of the active crustal shortening towards W-SW. The combined geomorphic (field evidences) and morphometric data (quantitative analysis of geomorphic indices) provide evidence of relative variation in the tectonic activity along the Kazerun Fault Zone and related landforms. The utilization of geomorphic parameters with comparison to the field observations exhibits change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area. [ABSTRACT FROM AUTHOR]

This paper reviews the tectonic, magmatic, and metallogenic history of the Tethyan orogen from the Carpathians to Indochina. Focus is placed on the formation of porphyry Cu ± Mo ± Au deposits, as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region. Relatively little is known about the history of the Paleotethys ocean, which opened and closed between Gondwana and Eurasia in the Paleozoic, and few ore deposits are preserved from this period. The Neotethyan ocean opened in the Permian–Early Triassic as the Cimmerian continental fragments (the cores of Turkey, Iran, Tibet, and Indochina) rifted from the northern Gondwana margin and drifted northwards. These microcontinents docked with the Eurasian margin at various points in the Mesozoic and Cenozoic, and formed a complex archipelago involving several small back-arc basins and remnants of the Paleotethyan ocean. The main Neotethyan ocean and these smaller basins were largely eliminated by collision with India and Africa–Arabia in the early Eocene and early-mid Miocene, respectively, although Neotethyan subduction continues beneath the Hellenic arc and the Makran. The majority of porphyry-type deposits are found in association with Neotethyan subduction (mainly in the Mesozoic and Paleogene), and syn- to post-collisional events in the mid-Paleogene to Neogene. They are found throughout the orogen, but some sections are particularly well-endowed, including the Carpathians–Balkans–Rhodopes, eastern Turkey–Lesser Caucasus–NW Iran, SE Iran–SW Pakistan, southern Tibet, and SE Tibet–Indochina. Other sections that appear barren may reflect deeper levels of erosion, young sedimentary cover, or lack of exploration, although there may also be real reasons for low prospectivity in some areas, such as minimal subduction (e.g., the western Mediterranean region) or lithospheric underthrusting (as proposed in western Tibet). Over the last decade, improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction-related are in fact broadly collision-related, some forming in back-arc settings in advance of collision, some during collision, and others during post-collisional processes such as orogenic collapse and/or delamination of subcontinental mantle lithosphere. While the formation of subduction-related porphyries is quite well understood, collisional metallogeny is more complex, and may involve a number of different processes or sources. These include melting of: orogenically thickened crust; previously subduction-modified lithosphere (including metasomatized mantle, underplated mafic rocks, or lower crustal arc plutons and cumulates); or upwelling asthenosphere (e.g., in response to delamination, slab breakoff, back-arc extension, or orogenic collapse). The most fertile sources for syn- and post-collisional porphyry deposits appear to be subduction-modified lithosphere, because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events, and retain the oxidized and relatively metalliferous character of the original arc magmatism. Unusually metallically enriched lithospheric sources do not seem to be required, but the amount of residual sulfide phases in these rocks may control metal ratios (e.g., Cu:Au) in subsequent magmatic hydrothermal ore deposits. Relatively Au-rich deposits potentially form in these settings, as observed in the Carpathians (e.g., Roşia Montană), Turkey (Kisladag, Çöpler), and Iran (Sari Gunay, Dalli), although the majority of syn- and post-collisional porphyries are Cu–Mo-rich, and resemble normal subduction-related deposits (e.g., in the Gangdese belt of southern Tibet). This similarity extends to the associated igneous rocks, which, being derived from subduction-mod [ABSTRACT FROM AUTHOR]

The Balkhash Metallogenic Belt (BMB) in Kazakhstan, one of the most important mineral concentrations in the Central Asian orogenic belt, hosts numerous porphyry Cu–Mo deposits, Cu-polymetallic skarns and W–Mo-bearing veins (greisens). In this paper, we present zircon U–Pb, biotite and K-feldspar 40 Ar/ 39 Ar, and apatite fission-track ages to reveal the thermal evolution of the East Kounrad, Akshatau, and Zhanet W–Mo deposits in the western part of the BMB. Ore-related intrusions of these three deposits have SHRIMP zircon U–Pb ages of 294 ± 3 Ma, 306 ± 1 Ma, and 304 ± 4 Ma, respectively. Magmatic biotite and K-feldspar from the Akshatau deposit yield 40 Ar/ 39 Ar ages of 292 ± 3 Ma, 289 ± 4 Ma, respectively, whereas K-feldspar from the East Kounrad deposit has a 40 Ar/ 39 Ar age of 278 ± 5 Ma. These deposits have significantly younger apatite fission-track ages of 92 ± 6 Ma, 92 ± 5 Ma and 80 ± 5 Ma, respectively. The age data document a regional magmatic-hydrothermal event between 306 and 294 Ma that formed the major W–Mo deposits. These deposits underwent staged cooling at least in the late Permian and late Cretaceous due to tectonic uplift. The results from this study, when combined with previous Re–Os data, provide, for the first time, significant insights into the thermal evolution of the magmatic-hydrothermal systems within the Balkhash Metallogenic Belt. [ABSTRACT FROM AUTHOR]

Geodynamic models offer insight into deformation styles of syn- and post-collisional extensional processes. Such models often ignore the effect of lateral viscosity contrast between accreted terranes and inherited tectonic boundaries. This paper presents a set of crustal-scale analog experiments of one-way post-collisional gravitational spreading testing the effect of crustal heterogeneity by using two mechanically contrasting blocks, pre-existing cuts with varying dips, and three layers with contrasting rheologies. Two blocks represent strong, mature, and weak, juvenile crustal parts. Both blocks have three horizontal crustal layers: brittle upper, weak partially molten middle and dry strong lower layer. Cuts represent pre-existing crustal-scale shear zones and tectonic boundaries. The experiments indicated that tectonic boundaries may facilitate exhumation and increase extensional strain, when the boundaries dip opposite to the flow direction. The tectonic boundaries may also split and divide the crust into separate blocks with independent deformation signatures: shortening, elongation or rotation. The tectonic boundaries rotated along vertical axes toward the flow direction. The modeling results suggest that in areas with inherited tectonic boundaries and compositional differences the amount of extension is unevenly distributed between the different parts during the widespread unilateral gravitational spreading and that the flow has different effects on the contrasting crustal units, in both lateral and vertical directions. To validate the modeling, the results are compared to geophysical and geological data from the Paleoproterozoic Svecofennian orogen in the Fennoscandian Shield. The comparison suggests that the orogen underwent 50% extension and was thinned by maximum of 20% via westward gravitational spreading. This spreading rotated the crustal-scale blocks, shear zones and tectonic contacts. It also brought exhumed, high grade middle crustal blocks into contact with subsided, low grade, upper crustal blocks. We suggest that results of the analog models can be used as proxies in both ancient and modern hot accreted orogens, which have undergone post-convergence continental mid-crustal weakening and have comprised of juxtaposed terranes with varying rheological compositions. [ABSTRACT FROM AUTHOR]

This paper presents new zircon and sphene U–Pb ages, biotite and hornblende 40 Ar/ 39 Ar ages, Hf isotopic data, and geochemical data for five Mesozoic plutons in the Erguna Massif of NE China. These data are used to constrain the late Mesozoic tectonic evolution of the Mongol–Okhotsk orogenic belt. This new dating, when combined with previously published ages, indicates that the Late Jurassic–Early Cretaceous (J 3 –K 1 ) intrusive rocks can be subdivided into three stages that represent periods of magmatism during the Late Jurassic (~ 155 Ma), early Early Cretaceous (~ 137 Ma), and late Early Cretaceous (~ 123 Ma). In addition, the rocks have undergone later deformation recorded by peak ages of ~ 137 and ~ 123 Ma. The Late Jurassic and early Early Cretaceous intrusive rocks in the study area are dominantly syenogranites and are either A-type granites or are classified as alkaline series, suggesting that they formed in an extensional environment. The late Early Cretaceous intrusive rocks in this area are generally monzogranitic and were emplaced as dikes in an extensional environment, along with coeval bimodal volcanics. These data, combined with the presence of regional unconformities in the northern part of Hebei Province and western part of Liaoning Province, and the spatial distribution of coeval volcanic rocks in NE China, suggest the Late Jurassic and early Early Cretaceous magmatisms and the early Early Cretaceous deformation in this area occurred in an extensional environment related to the delamination of a thickened part of the crust after closure of the Mongol–Okhotsk Ocean. In comparison, the late Early Cretaceous deformation and magmatism occurred in an extensional environment related to either delamination of the previously thickened crust related to the Mongol–Okhotsk tectonic regime or the subduction of the Paleo-Pacific Plate, or the combined influence of these two tectonic regimes. [ABSTRACT FROM AUTHOR]

The Gorny Altai terrane (GA) is a key area in understanding the crustal evolution of the Central Asian Orogenic Belt (CAOB). This paper reports U–Pb and Hf-isotope data for detrital zircons from Cambrian to early Devonian sedimentary sequences to constrain their provenance, as well as the tectono-magmatic events and crustal growth in this region. Nearly all the detrital zircons are characterized by euhedral to subhedral morphology, high Th/U ratios (ca. 0.1–1.6) and typical oscillatory zoning, indicating a magmatic origin. The three samples from the Gorny Altai Group (middle Cambrian to early Ordovician) yield detrital zircon populations that are composed predominantly of 530–464 Ma grains, followed by a subordinate group of 641–549 Ma old. The Silurian and Devonian samples exhibit similar major zircon populations (555–456 Ma and 525–463 Ma, respectively), but a significant amount of additional 2431–772 Ma zircons occur in the early Devonian sample. Our results suggest that detritus from the nearby Kuznetsk–Altai intra-oceanic island arc served as a unitary source for the Cambrian–Silurian sedimentary sequences, but older detritus from other sources added to the early Devonian sequence. The low abundance of ca. 640–540 Ma detrital zircons may testify that this island arc was under a primitive stage in this period, when mafic volcanic rocks probably dominated. In contrast, the dominant population of ca. 530–470 Ma zircons may indicate an increased amount of granitic rocks in the source area, suggesting that the Kuznetsk–Altai island arc possibly evolved into a mature one in the Cambrian to early Ordovician. The ca. 530–470 Ma detrital zircons are almost exclusively featured by positive ε Hf (t) values and have two-stage Hf model ages of ca. 1.40–0.45 Ga, indicating that the precursor magmas were sourced predominantly from heterogeneous juvenile materials. We conclude that the late Neoproterozoic to early Paleozoic magmatism in the Kuznetsk–Altai arc made a significant contribution to the crustal growth in the CAOB. The absence of middle Ordovician to early Devonian detrital zircons possibly implies that the area changed to a passive margin in the middle Ordovician. Of special significance are the 2431–772 Ma zircons in the early Devonian sample, which are quite comparable to the Precambrian detrital zircons from the Altai–Mongolian terrane (AM) but distinct from those from the Siberian continent. This indicates that the AM is a plausible source for the 2431–772 Ma zircons. Our data therefore imply that the GA possibly amalgamated with the AM before the early Devonian rather than in the late Devonian to early Carboniferous as previously suggested. [ABSTRACT FROM AUTHOR]

The Qinling orogen is a typical composite orogen for understanding multi-stages of magmatism and orogenic processes. Many studies have been carried out on the magmatic rocks in the Qinling orogen but their petrogenesis is still controversial. This paper presents a review of all granitoid rocks based on previous and new studies of geochronology and geochemistry. Four distinct periods of granitoid magmatism, Neoproterozoic (979-711 Ma), Paleozoic (507-400 Ma), Early Mesozoic (250-185 Ma) and Late Mesozoic (160-100 Ma), have been recognized from the Qinling orogen according to zircon U-Pb ages, intrusion associations and deformation, as well as regional geology. The Neoproterozoic granitic rocks consist of three stages at 979-911, 894-815 and 759-711 Ma, respectively, corresponding to strongly deformed S-type, weakly deformed I-type and A-type granitoids. They can be interpreted as magmatic occurrences in syn-collisional, post-collisional and extensional settings, respectively, in response to old continental terranes of the Neoproterozoic tectonomagmatic events in the old continents of China, such as South China and Tarim cratons. Although this continental terrane would be involved in the Phanerozoic Qinling orogeny, the Neoproterozoic magmatic rocks are not the products of the Qinling orogenic processes. The Paleozoic magmatic rocks can be classified into three stages at 507-470, 460-422 and 415-400 Ma, respectively. The first-stage magmatism is temporally associated with ultra-high pressure metamorphism in the North Qinling terrane. These magmatic rocks are interpreted as magmatic occurrences in subductional, syn-collisional and post-collisional settings, respectively. The Early Mesozoic magmatic rocks occur in two stages at 252-185 and 225-200 Ma, respectively. The first-stage granitoids are mainly represented by I-type quartz diorites and granodiorites, and the second stage by granodiorites and monzogranites with the I-to A-type characteristics and some with rapakivi textures. Their emplacement ages and geochemical parameters such as A/CNK, KO/NaO ratios and εNd( t) values do not show any polarity change in perpendicular to subduction/collision zone. Therefore, all these Early Mesozoic granitoids are unlikely the product of continental subduction as some researchers suggested. Instead, they are plausibly related to the subduction of the Mianlue Ocean and the subsequent collision between the South China Craton and the South Qinling terrane. The Late Mesozoic granitoids were emplaced mainly at two stages of 160-130 and 120-100 Ma, and characterized by the evolution from I- to I-A- and A-type granitoids. These characteristics are consistent with the granitoid magmatic evolution from contractional to extensional settings during the Jurassic/Cretaceous in eastern China. Accordingly, the Late Mesozoic granitoid rocks in the Qinling orogen probably have a similar petrogenetic mechanism to those of the huge magmatic belt along the western Pacific margin, i.e., intra-continent magmatism related to a far-field effect of the subduction of Paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

Karstic aquifers are the main groundwater source in Southeastern Europe and the Middle East. Many large springs and sources which drain Alpine orogenic belt and its branches are tapped and utilized for drinking water supply. Due to the unstable regime of the karstic springs, the main challenge for most of the waterworks is to ensure water supply during recession periods which coincide with the dry season, usually summer and early autumn months. Besides the problem of water shortage, water pollution of this open and generally very permeable type of aquifer is another major constraint in local water management. However, in comparison with other type of aquifers, the highly developed karst and its significant storage capacity as found in the studied areas may attenuate significant rainfall/runoff variations and possible climate changes. Most commonly, intensive rain episodes do not result in extreme floods in the studied karst terrains, while stored groundwater provides sufficient base flows for dependent ecosystems during the recession or periods of drought. Several typical hydrographs and results of some models applied for forecasting climate change impact presented in this paper represent a good example of specific karst aquifer behaviours and importance of considerable storage capacity in deeper parts of the aquifer. [ABSTRACT FROM AUTHOR]

Ultrahigh-temperature ( UHT) granulites in the South Altay orogenic belt of Northwestern China provide important clues for the lower crustal components and tectonic evolution of the Central Asian Orogenic Belt during the Paleozoic. In this paper, we studied whole-rock geochemistry and mineral characteristics to understand the protolith and metamorphic evolution of the Altay UHT granulite. The Altay granulite shows negative discriminant function values ( DF) of −9.27 to −3.95, indicating a sedimentary origin, probably an argillaceous rock. The peak metamorphic temperature-pressure conditions of 920-1010 °C and > 9 kbar were estimated from the geothermobarometry, together with the stability of spinel (low ZnO) + quartz and orthopyroxene ( Al2O3 up to 9.2 wt.%) + sillimanite + quartz in the Altay UHT rock, indicate a UHT metamorphic condition has been achieved. Two stages of retrograde conditions are recognized in these rocks; the first is an isothermal decompression to approx. 750 °C at 5.2-5.8 kbar at the early stage, and the second is the cooling down to 520-550 °C at 4.8-5.2 kbar. Combined with previous study, the formation of the Altay UHT pelitic granulite with a clockwise retrograde P- T path is inferred to be related with collisional and accretional orogenic process between the Siberian and Kazakhstan- Junggar plates. [ABSTRACT FROM AUTHOR]

The authors explains the geochronological and stratigraphic data relating to Silurian rocks and the detrital zircon data on the southern Quebec Appalachian, in response to a comment about their paper published in this journal. Topics discussed include the tectonic characteristics of the Miramichi terrane and Matapadia basin in New Brunswick, the limited magmatic activity in the area, and the source of volcanic rocks. A discussion on the northwest-directed subduction model is also offered.

The early Paleozoic orogen of South China is possibly one of the few examples of intraplate orogeny in the world. It is characterized by an angular unconformity between post-Silurian cover and pre-Devonian strata and by the intensive and extensive early Paleozoic granitic plutonism. However, synchronous mafic–ultramafic rocks have not been well-studied, but they are crucial for understanding the nature and evolution of the orogen. In this paper, we present the first detailed LA-ICP-MS zircon U–Pb dating, major and trace element geochemical and Sr–Nd–Hf isotopic data for a Silurian gabbroic pluton (Dakang) and a coeval granitic pluton (Guiyang), that have recently been identified in central Fujian, in the southeastern part of the orogen. We assess the origin of these mafic and granitic rocks and their relationship to the evolution of the early Paleozoic orogen in South China. LA-ICP-MS zircon U–Pb dating shows that the Dakang and Guiyang plutons were emplaced at 441–438 Ma and 431 Ma, respectively. The Dakang pluton consists of gabbros and minor intermediate rocks (diorite, monzodiorite and monzonite). These rocks are all metaluminous and potassic, and are enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE). They have initial 87 Sr/ 86 Sr of 0.7066–0.7098, ε Nd (T) of − 7.0 to − 3.3 and ε Hf (T) (in-situ zircon) of − 5.2 to − 4.4. Geochemical data suggest that the Dakang gabbroic magmas were derived by partial melting of previously subduction-modified lithospheric mantle in the spinel–garnet transition zone at a high temperature (~ 1300 °C). These primary magmas underwent fractionation crystallization of clinopyroxene and amphibole, forming the evolved gabbros and intermediate rocks. The Guiyang pluton consists of weakly peraluminous granites, which show low Ga/Al ratios (10,000*Ga/Al < 2.6) and so can be classed as I-type granites. They have initial 87 Sr/ 86 Sr of 0.7095–0.7113, ε Nd (T) of − 6.7 to − 5.9 and ε Hf (T) (in-situ zircon) of − 7.7 to − 0.8. Geochemical data suggest that the Guiyang granites were generated by partial melting of a mixed source of Paleoproterozoic metaigneous and metasedimentary rocks in the lower crust. Our new data, together with published data, confirm that lithospheric delamination occurred along the metamorphic core of the early Paleozoic orogen of South China during the Silurian (442–420 Ma), and that this represents a post-orogenic tectonic regime in the orogen core. [ABSTRACT FROM AUTHOR]

This paper presents new results on zircon U–Pb dating, Hf isotope analyses, and trace and major element analyses of Late Devonian and early Carboniferous metavolcanic rocks and early Carboniferous alkaline granites of central Jilin Province, NE China, and uses these data to constrain the late Paleozoic tectonic evolution of the southern margin of the Central Asian Orogenic Belt (CAOB). Zircon U–Pb ages, determined using laser ablation–inductively coupled plasma–mass spectrometry, indicate that Late Devonian Jifanggou Group metarhyolites formed at ∼360 Ma, whereas the early Carboniferous Panling Formation metabasaltic andesites and metarhyolites and the Silengshan alkaline granite formed at ∼340 Ma. The Late Devonian metarhyolites, which exhibit zircon ε Hf ( t ) values of +2.77 to +8.94 and corresponding two-stage model ages ( T DM2 ) ages of 969–1525 Ma, are geochemically similar to I–A-type granites, which is indicative of formation from a primary magma generated by partial melting of juvenile lower crustal material in an extensional environment. The early Carboniferous metabasaltic andesites and metarhyolites are geochemically bimodal, with SiO 2 concentrations of 52.1–61.4 and 72.8–75.1 wt.%, respectively. The former are enriched in Ba, Sr, Th, and U, and are depleted in K, Rb, Nb, Ta, and Ti, whereas the latter are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, K, Th and U), and are depleted in heavy REEs (HREEs), high field strength elements (HFSEs; e.g., Nb, Ta, Ti, and P), and Sr. Zircons from the metabasaltic andesite and metarhyolite units have ε Hf ( t ) values of +9.80 to +12.8 and +11.0 to +13.1, respectively, and corresponding single-stage model ages ( T DM1 ) and two-stage model ages ( T DM2 ) of 468–606 and 584–776 Ma, respectively. Silengshan alkaline granite samples contain minor amounts of riebeckite, are relatively LREEs and LILEs enriched and HREEs and HFSEs depleted, and have markedly negative Eu anomalies, features that are typical of A-type granites. These granite samples have zircons with ε Hf ( t ) values of +8.04 to +13.4 and corresponding T DM2 ages of 549–1037 Ma. These data suggest that the primary magma that formed the early Carboniferous metabasaltic andesites was derived from partial melting of depleted lithospheric mantle material that had been modified by subduction-related fluids, whereas the primary magmas for the coeval metarhyolites and the Silengshan alkaline granite were derived from partial melting of newly accreted crust. These early Carboniferous igneous rocks formed in an extensional setting within the eastern segment of the southern CAOB. [ABSTRACT FROM AUTHOR]

This paper is concerned with the spatial variation of the elastic thickness ( T e ) in the Himalayan–Tibetan orogen and its implications for the understanding of lithospheric structure and deformation. New T e maps of the Himalayan–Tibetan orogen are generated from the new combined satellite-terrestrial gravity (EIGEN6C3stat) and topography (ETOPO1) models using the fan wavelet coherence technique. The high- T e values ( > 60 km ) are observed in the Indian shield and the Tarim basin; while the low- T e values ( < 40 km ) are prevailing over most of the Tibetan Plateau. We also find that the T e distributions estimated using the high and low central wavenumber (i.e., | k 0 | ) wavelets are different in southern Tibet. By combining constraints from the current seismic and thermo-rheological modeling, this difference may reflect that the strength of the lithosphere in southern Tibet mainly resides in the lithospheric mantle. Within most parts of central and northern Tibet, the T e values are relatively low ( < 30 km ), indicating that the entire lithosphere is weak. Our analysis finds that the T e variations are probably associated with changes in lithosphere structure. We interpret the abrupt changes in T e between southern and northern Tibet to indicate the location of the underthrusting strong Indian lithosphere beneath Tibet. Our results suggest that the northern limit of the underthrusting Indian plate reaches as far north as the Hindu Kush and the southwestern margin of the Tarim basin (near 70 ° – 80 ° E ), and extends along the Bangong-Nujiang Suture in the central ( 80 ° – 87 ° E ). Eastward between 87 ° E – 93 ° E , it may move to the Indus-Tsangpo Suture, indicating a delamination of Indian mantle lithosphere there. Further to the east, it may underthrust northward beneath the eastern Qiangtang block. [ABSTRACT FROM AUTHOR]

The Meso-Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt, which is one of the key areas of the Alpine-Himalayan system, is still controversial due to lack of systematic geological, geophysical, geochemical and chronological data. The prevailing interpretation is that this belt represents the southern margin of Eurasia during the Mesozoic and its geodynamic evolution is related to northward subduction of oceanic lithosphere. This paper reports the first detailed geological, geochemical and chronological data from felsic tuffs interbedded with late Cretaceous turbidites in the Southern Zone of the Eastern Pontides Orogenic Belt. Individual tuff layers are thin, mostly < 2 m in thickness, implying that these are dominantly air-fall tuffs. Petrographic data indicate that the felsic tuffs, which exhibit various degrees of alteration, can be classified as crystal-rich and crystal-poor tuffs. The crystal-poor tuffs consist mainly of 45–65% devitrified glass shards and 10–20% broken quartz crystals, whereas the crystal-rich tuffs consist of > 50% crystals. The zircon U–Pb data show three statistically distinct ages at 84, 81 and 77 Ma, with uncertainties of about 1 Ma, suggesting that tuff-forming late Cretaceous magmatism started about 84 Ma ago and was episodically active over a minimum of 7 Ma. The age data also indicate that the average accumulation rate of the turbiditic sequence that hosts the felsic tuffs remained constant between 36 and 40 cm/10 ky. Their enrichment in LIL and LRE elements relative to HFS and HRE elements, and also strongly negative Nb, Ta and Ti anomalies, are consistent with those of magmas generated by subduction-related processes. The tuffs have relatively low initial ratios of 143 Nd/ 144 Nd (0.512296–0.512484; ε Nd : − 2.1 and − 7.2) and 87 Sr/ 86 Sr (0.704896–0.706159). Their initial Pb isotopic compositions range from 18.604 to 18.646 for 206 Pb/ 204 Pb, from 15.644 to 15.654 for 207 Pb/ 206 Pb and from 38.712 to 38.763 for 208 Pb/ 204 Pb. The distribution of Sr–Nd isotopic compositions in the late Cretaceous igneous rocks from different locations of the Eastern Pontides Orogenic Belt is consistent with two-component mixing between depleted mantle and crust. However, the Pb isotopic data are not compatible with two-component mixing and require at least a third component. Considering all of the new data and also previous data such as southward migration and increasing potassium content of the late Cretaceous arc volcanism, the northward migration of Cenozoic igneous activity, northward drift of the belt since the late Cretaceous and the existence of south-dipping reverse fault systems in the whole region, the Meso-Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt can be best explained by southward subduction of Tethys oceanic lithosphere, rather than northward subduction. [ABSTRACT FROM AUTHOR]

The Altai-Mongolian terrane (AM) is a key component of the Central Asian Orogenic Belt (CAOB), but its tectonic nature has been poorly constrained. This paper reports geochemical compositions of Cambrian–Ordovician meta-sedimentary rocks from the northern AM to trace their source nature and depositional setting, which in turn place constraints on the geodynamic evolution of the AM. The Cambrian–Ordovician meta-sedimentary rocks from the northern AM show variable major-element compositions, with negative correlation between SiO 2 and TiO 2 , Al 2 O 3 , Fe 2 O 3 T , MgO and K 2 O. Their high ICV values (1.18–2.53) and relatively low CIA values (37.9–76.3) indicate that the sediments were immature and probably underwent mild to moderate chemical weathering. The low-SiO 2 samples are characterized by relatively restricted SiO 2 /Al 2 O 3 (mostly 2.60–6.07) and low Rb/Sr ratios (0.02–1.89), implying their proximal deposition without obvious sedimentary sorting and recycling. In contrast, the high-SiO 2 samples show much higher SiO 2 /Al 2 O 3 ratios (15.4–19.9) possibly due to sedimentary sorting and/or silicification. All these samples yield relatively high Al 2 O 3 /TiO 2 ratios (15.6–22.8), strong LREEs/HREEs differentiation ((La/Yb) N = 4.86–10.7) and obvious negative Eu anomalies (δEu = 0.61–0.83). Combined with their Th/Sc, Zr/Sc, La/Th and Co/Th ratios comparable with intermediate-acidic magmatic rocks, we infer that these kinds of magmatic rocks served as a major source for the investigated meta-sedimentary rocks. The TiO 2 , Al 2 O 3 and Fe 2 O 3 T + MgO concentrations are mostly higher than typical sediments from passive margin, and the Th/U, La/Sc, Th/Sc, Eu/Eu ∗ , Zr/Hf, Zr/Th and La/Th ratios are quite similar to sediments from continental arcs. These data suggest that the Cambrian–Ordovician meta-sedimentary rocks from the northern AM were most likely deposited in an environment related to a continental arc setting rather than a passive regime. These rocks show strong similarities to their counterparts in the Chinese Altai (CA, southern AM) and Tseel terrane (southeastern extension of the CA in western Mongolia) in terms of geochemical compositions and depositional setting. With combination of recent isotopic studies for detrital zircons, our data suggest that the AM probably represented a coherent accretionary prism along a continental arc in the early Paleozoic. [ABSTRACT FROM AUTHOR]

The SW Alps result from the inversion of the European continental margin during the oblique convergence between Europe and Adria since the Cretaceous. The orogenic deformation is controlled by two factors: the inherited sedimentary and structural record and the geodynamic interaction between the two plates. In this paper we present a stratigraphic and structural analysis of the external SW Alps (Ventimiglia–Menton area) in order to define the sedimentary and deformational geometries of the chain and to reconstruct the evolutionary history. The field-data highlight the preeminent role played by inherited salt-structures, which derive from the depositional history experienced by the European margin since the Mesozoic onwards. From Late Triassic to Jurassic, evaporites and carbonates deposited as a response to the Thetyan rifting. The following emplacement of the Cretaceous flysch and of the Eocene foreland basin succession was strongly influenced by the extensionally-triggered salt diapirism and by the interactions with deformations connected to the Pyrenees dynamics. The resulting geologic discontinuities (i.e. diapir-induced highs and basins, inherited normal and trasform faults) strongly influenced the successive Oligo-Miocene evolution of the belt in the study area. Observed changes in the thrusts and folds kinematics are considered as the results of rotation during their approaching to inherited highs. Furthermore, the overturning of thrusts and folds in the front of the diapiric flanks are associated with the progressively salt squeezing into the anticlines cores promoted by ongoing Alpine compression. Finally, the kinematic data from the study area show radical differences in the tectonic transport direction with respect to the rest of the SW Alps (NW- to W-ward in the Ventimiglia–Menton area, S- to SW-ward in Provence and Ligurian Alps). This difference is interpreted to be caused by the relative motions of crustal blocks dominated by transpressive tectonics in the frame of the Oligo-Miocene western Mediterranean geodynamics. [ABSTRACT FROM AUTHOR]

The dynamic evolution of the Paleo-Tethys Ocean from continental rift-drift and seafloor spreading to initial subduction and final closure has been hotly debated. This paper tries to bring new constraints to this longstanding debate based on the compiled the latest data and investigations into Carboniferous-Triassic magmatism in the westernmost segment of the Eastern Kunlun orogenic belt, North Tibetan Plateau. New results indicate that the ca. 335 Ma appinite stocks were derived from the asthenosphere mantle wedge slightly modified by slab-derived materials. The ca. 244 Ma dioritic appinite stocks were sourced from the partial melting of hydrothermally altered upper oceanic crust following the closure of the Paleo-Tethys Ocean. The ca. 231 Ma adakitic granite stock originated from the partial melting of the thickened eclogitic lower crust in the syn -collisional setting, and the ca. 219–215 Ma granite batholith had a mafic source in the post-collisional setting. By integrating records available, new scenarios of the evolution of the Paleo-Tethys Ocean in Eastern Kunlun were established. The ca. 390–380 Ma continental rifting leading to the opening of the Paleo-Tethys Ocean is attributed to the post-collisional gravitational instability subsequent to the closure of the Proto-Tethys Ocean and the far-field extensional stress induced by the retreating subduction of the Paleo-Asian Oceanic lithosphere along the northern margin of Tarim-Qaidam. The Paleo-Tethys Oceanic lithosphere initially northward subducted at ca. 366–335 Ma. The closure of the Paleo-Tethys Ocean leading to the "soft" collision between the Eastern Kunlun and Bayanhar terranes occurred at ca. 235–225 Ma followed by the ca. 225–200 Ma post-collisional extension. • The ca. 390–380 Ma opening of the PTO due to gravitational instability and retreating subduction. • The initial northward subduction of PTO occurred at ca. 366–335 Ma. • The closure occurred at 235–225 Ma followed by 225–200 Ma post-collisional extension. [ABSTRACT FROM AUTHOR]

We review in this paper the major late Mesozoic contractional deformation in North and NE China and establish the tempo-spatial distribution pattern of Jurassic-Cretaceous magmatism, with the aim at clarifying its link with evolving multi-plate convergent geodynamics in NE Asia. We recognize two major changes in tectonic regime, one occurring at ~170 Ma, which marks the tectonic switch from extensional to compressional regimes, while another at ~135 Ma which manifests the change from compressional to extensional settings. Accordingly, Jurassic-Cretaceous magmatism migrated from the marginal zones in ~200 -170 Ma to the continental interior in 170-135 Ma and then was followed by Mid-Cretaceous (135-120 Ma) magmatic flare-up in the continental interior, which migrated progressively eastward since ~120 Ma. Based on these observations, we make a division of three tectonic stages and discuss their plate geodynamic setting. (1) The early stage in 200-170 Ma was dominantly under extensional setting with A-type granitoids and bi-modal volcanism occurring along the eastern and northern marginal zones. (2) The middle stage in 170-135 Ma was manifested by significant multi-directional crustal shortening and rejuvenation of the ancient orogenic belts, as distant response to multi-plate convergence along the East Asia continental margins. (3) The late stage was manifested first by a thermal surge in 135-120 Ma with the formation of extensional structures and rift basins in the continental interior, then followed by alternation of tectonic compression and extension, related to the effect of paleo-Pacific slab subduction. We propose that the thickening acquired during the middle tectonic stage and subsequent lithospheric thinning in the late stage triggered large-scale crustal melting, episodic magmatism and associated metallogenic outbreak in North and NE China. [Display omitted] • Two major tectonic switches were identified to occur at 170 Ma and at 135 Ma in North and NE China. • Jurassic-Cretaceous magmatic migration trends coincide with the change in tectonic regimes. • Jurassic-Cretaceous tectono-magmatic evolution was divided into three stages (200–170 Ma, 170–135 Ma, and 135–75 Ma). • Jurassic-Cretaceous tectonic evolution stages were linked with multi-plate convergence geodynamics in NE Asia. [ABSTRACT FROM AUTHOR]

• Three episodes of Neoproterozoic magmatisms are identified in the Songnen Massif. • These Neoproterozoic granitoids formed by reworking of Paleo-Mesoproterozoic crust. • The ca. 790 Ma monzonites were formed via a magma mixing process. • Precambrian basement composition of the Songnen Massif is laterally heterogeneous. This paper reports new zircon U–Pb geochronological, whole-rock geochemical, and zircon Hf isotopic data for Neoproterozoic intrusive rocks in the Songnen Massif in the eastern Central Asian Orogenic Belt (CAOB), with the aim of revealing the petrogenesis of the Neoproterozoic intrusive rocks, and constraining the basement composition and crustal growth process of the Songnen Massif. Dating results identify three episodes of Neoproterozoic magmatism at ca. 950, ca. 856, and ca. 790 Ma in the eastern Songnen Massif. The ca. 950 Ma magmatic rocks consist of syenogranites, the ca. 856 Ma magmatic rocks comprise mainly gneissic monzogranites, and the ca. 790 Ma magmatic rocks consist of gneissic monzonites and monzogranites. The Neoproterozoic granitoids have high contents of SiO 2 and K 2 O, low contents of total Fe 2 O 3 and MgO, and show characteristics of enrichment in large-ion lithophile elements (e.g., K and Rb), and depletion in high-field-strength elements, implying that their primary magmas could have been derived from partial melting of the lower crust. However, compared with the ca. 790 Ma monzogranites [ε Hf (t) = +7.3 to +9.5] in the south of the Songnen Massif, the ca. 950 and ca. 856 Ma granitoids in the north have much lower zircon ε Hf (t) values (−2.0 to −0.2 and −10.6 to −8.9, respectively), suggesting that the ca. 950 and ca. 856 Ma magmas were generated by the reworking of ancient mafic lower crust, whereas the ca. 790 Ma granitic magma was generated by the reworking of juvenile mafic lower crust. In contrast, the ca. 790 Ma gneissic monzonites were formed by mixing of the mantle-derived and crust-derived melts. Considering the Precambrian magmatism, detrital and captured zircons, and zircon Hf model ages together, the Precambrian basement of the Songnen Massif includes not only the Neoproterozoic crustal materials, but also the Neoarchean–Mesoproterozoic components. Zircon ε Hf (t) values of the Neoproterozoic granitoids in the Songnen Massif appear to progressively decrease from south to north, reflecting a lateral heterogeneity of basement composition of the eastern Songnen Massif, and indicating that crustal growth occurred mainly during the late Mesoproterozoic and Neoproterozoic in the south, while during the late Paleoproterozoic in the north. [ABSTRACT FROM AUTHOR]

• Distribution and evolution of middle-deep groundwater in marine strata were studied. • Qinling-Dabie and Jiangnan orogenic belt affected the erosion of the strata. • Transfer direction of tectonic stress affects hydrochemical types and flow paths. • Salinity comes from connate water and/or dissolved rock flushed by rainwater. Large marine sedimentary basins often contain concentrated geothermal mineral resources. Chongqing Municipality, located in the Sichuan marine sedimentary basin and the surrounding mountainous area of southwest China, is rich in thermal waters and brines. Chongqing belongs to the Middle-Upper Yangtze Tectonic Block. Previous studies have mostly been based on basin structure, but less on the whole plate structure to study the distribution and evolution of groundwater. In this paper, 78 middle-deep groundwater samples in the study area were collected to better understand the occurrence and hydrochemical evolution of middle-deep groundwater using ionic ratios, hydrogen and oxygen isotopes, and geothermometers. Tectonic stress has been transferred from SE to NW in the Jiangnan Orogenic Belt and from NE to SW in the Qinling-Dabie Orogenic Belt, making the extent of tectonic denudation and its related properties such as hydrochemical type, reservoir temperature, and maximum circulation depth trend along the same directions. Four of the water samples have Br × 103/Cl and Na/Cl molar ratios >1.5 and <0.87, respectively, indicating that they are marine metamorphic brines. The ratios of the rest of the samples are mostly distributed in a range suggesting precipitation-dissolved halite or somewhere in between. This suggests that the study area is in the denudation leaching period of the hydrogeological cycle, and the middle-deep groundwater system is still in the dynamic process of formation water (residual metamorphic paleo-seawater) of the previous hydrogeological cycle diluted in places by rainwater. A conceptual circulation model for regional middle-deep groundwater is proposed. Rainfall in the late Pleistocene infiltrated as groundwater recharge via fractures and karst valleys and circulated to deep strata driven by gravity, where it could mix with residual, paleo-evaporated seawater. Then the groundwater was heated by geothermal and chemical energy sources, mixing with shallow groundwater as it moved upward along faults toward the surface eventually to emerge from springs. [ABSTRACT FROM AUTHOR]