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[Display omitted] • A regional geology systematic review based on cross-sections and space–time diagrams. • The Dom Feliciano Belt orogenic cycle records pre-, syn- and post-collisional stages. • PT-paths are characteristic of hinterland and foreland tectonic domains. • Northern DFB foreland rifting contrasts with central DFB active margin in the Tonian. • The symmetric schismogenesis of West Gondwana Orogen models can be conciliated. The Dom Feliciano Belt evolution is reviewed based on cross-sections, space–time diagrams, P-T paths, and Sr–Nd isotopic data of pre-collisional metaigneous rocks. The belt is divided into northern, central and southern sectors, subdivided into tectonic domains, developed at Neoproterozoic pre-, syn- and post-collisional stages. The northern sector foreland pre-collisional setting represents a rift, with tholeiitic (meta)volcanic rocks (∼800 Ma) chronocorrelated to hinterland intermediate and acidic orthogneisses of high-K calc-alkaline arc signature. In contrast, the central sector records a complete section from the forearc towards the back-arc region during pre-collisional times. In the western domain, ophiolites (∼920 Ma) are associated with arc-related orthogneisses and metavolcanic rocks (880–830 Ma; 760–730 Ma). At back-arc position, continental arc-related magmatism (800–780 Ma) is registered by hinterland orthogneisses and central foreland metavolcanic rocks. Ophiolites on the hinterland opposite side comprise two compositional groups, with N-MORB and supra subduction signature, interpreted as a back-arc basin record (∼750 Ma). The pre-Neoproterozoic basement of the whole belt is correlated with the Nico Perez Terrane and Luis Alves Block (Archean to Mesoproterozoic, with Congo Craton affinity). This contrasts with the Piedra Alta Terrane (Rio de La Plata Craton, only Paleoproterozoic), westernmost Uruguay. The suture between the Piedra Alta and Nico Perez terranes is correlated with the suture zone in the westernmost central sector. Transpression affected both foreland and hinterland during collision (660–640 Ma), with high-T/low-P hinterland progressive exhumation, whilst foreland low- to medium-grade correlated sequences record underthrusting. Post-collisional processes included magmatism throughout the belt (640–580 Ma), strain partitioning along strike-slip shear zones, and foreland basin fill. Late tectono-metamorphic and magmatic processes (560–540 Ma) were attributed to the Kalahari Craton collision. Arc magmatism migration due to subduction angle variations suggests modern-style plate tectonics during Gondwana amalgamation. Diachronism and kinematic inversion are characteristic of an oblique convergent multi-plate orogenic system. [ABSTRACT FROM AUTHOR]

Continental orogens that involve subduction and collision are important target areas for studying the growth, stabilization and transformation of Earth's continents. In particular, the nature of the lithospheric mantle and its relationship to the overlying crust in these active subduction-collision zones are key factors to be constrained. Mantle xenoliths entrained by Cenozoic basalts from the Indochina Block, the Sukhothai Arc and the Inthanon Zone (IB-SA-IZ) provide direct deep-seated samples of the lithospheric mantle derived from part of the Tethyan orogenic belt, offering a unique opportunity to study mantle processes during orogenesis in response to the closure of the Paleo-Tethys Ocean. The studied mantle xenoliths comprise 32 spinel lherzolites, six harzburgites, and one olivine websterite. We present a comprehensive study of the elemental geochemistry and Os isotopes of this sample suite. Their lithophile element systematics indicate that they represent mantle residues after varying degrees of melt extraction (5–24%), followed by melt refertilization. Although the highly siderophile element abundances have been affected to some extent by melt refertilization through removal of sulfides, the Os isotopic compositions of the studied xenoliths were minimally disturbed. Lherzolites and the sole olivine websterite from the IB-SA-IZ share similar Re-Os isotope systematics (187Os/188Os: 0.121–0.137) to global abyssal peridotites, representing juvenile lithospheric mantle accreted from the upwelling asthenosphere, most likely associated with arc-continent collision in response to the closure of the Paleo-Tethys Ocean and back-arc basin during the Middle-Late Triassic. In contrast, the refractory harzburgites from the Indochina Block and Sukhothai Arc are characterized by substantially lower 187Os/188Os ratios (187Os/188Os: 0.117–0.122) than the lherzolites, yielding Mesoproterozoic Re-depletion Os model ages, which can be interpreted as either ancient lithosphere relics beneath these regions or accreted ancient mantle debris from the upwelling asthenosphere. Although the interpretation for the origin of the older harzburgites is ambiguous, we can conclude that rejuvenation of the lithospheric mantle commonly occurred beneath different tectonic units of the Tethyan orogenic belt: i.e., the pre-existing lithospheric mantle beneath different tectonic units of the Tethyan orogenic belt has been largely replaced by upwelling asthenospheric mantle during the Middle-Late Triassic orogenesis. This mantle was then further refertilized to varying degrees by asthenosphere-derived melts. Both processes play key roles in defining the nature of the lithospheric mantle in orogenic settings. This study also highlights that the geodynamic processes in the lithospheric mantle beneath orogenic belts can be well constrained by integrated evidence from lithophile and highly siderophile elements and their isotopes (e.g., Os isotopes) of mantle xenoliths. [ABSTRACT FROM AUTHOR]

Four Tethyan ocean basins are recognised in Asia, the Proto-Tethys (Late Proterozoic - Silurian), Palaeo-Tethys (Middle Devonian - Late Triassic), Meso-Tethys (Middle Permian - Late Cretaceous) and Ceno-Tethys (late Middle Triassic - Eocene). Multi-disciplinary data, including ages of pelagic sediments, ocean plate stratigraphy, seamounts, ophiolites, blueschists, eclogites in accretionary complexes, volcanic arc and magmatic rocks found along suture zones of the Tethyan oceans are described and used to date the opening and closure of these oceans. The evolution of the Tethyan ocean basins in Asia illustrates that Asia has been a giant convergent zone for more than 500 million years and the Phanerozoic construction and evolution of Asia involved the opening and closure of Tethyan ocean basins and the collision and accretion of Gondwana-derived continental blocks and the Indian Craton. Subduction processes, arc and back-arc basin generation, and continent-continent and arc-continent collisions led to the principal orogenic events, basin development and related mineral and energy resource deposits recorded in Asia. Three major orogenic belts are recognised in Asia, the Central Asian Orogenic Belt, that relates to the evolution of the Palaeo-Asia Ocean, and the Tethyan (Tethysides) Orogenic Belt and the Alpine-Himalayan Orogenic Belt which relate to the evolution of Tethyan ocean basins. The principal Tethyan basin related orogenies in Asia are the Bhimphedian Orogeny (Ordovician-Silurian) that reflects the collision of major Asian continental blocks ("Asian-Hun Superterrane") with Gondwana, the Indosinian (Cimmerian) Orogeny (Permian-Triassic) resulting from Palaeo-Tethyan subduction processes, collisions of Asian blocks and collision of the Cimmerian continent with Asia, and the Himalayan-Tibetan Orogeny (Cretaceous-Palaeogene) caused by subduction of the Meso- and Ceno-Tethys oceans and the Lhasa-Asia and India-Asia collisions. [Display omitted] • Proto-, Palaeo-, Meso-, and Ceno-Tethys oceans are recognised in Asia. • Orogeny was driven by subduction/closure of Tethyan oceans and collision of blocks. • Tethyan & Alpine-Himalayan orogenic belts relate to evolution of Tethyan oceans. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three phases of deformation (D 1 -D 3) are recognized in the Langzishan Barrovian metamorphic series. • The kyanite zone rocks record a clockwise P-T-D path in the Paleoproterozoic. • Metamorphic and deformational characteristics documented by Barrovian metamorphic series in the Paleoproterozoic and Phanerozoic are comparable, possibly indicating a similar orogenic mechanism. Orogenesis always involves multiple tectonic events accompanied by metamorphic cycles. The Barrovian metamorphic series often records complicated prograde metamorphism and deformational features, which are crucial for understanding the related orogenic evolution. While Barrovian metamorphism have been widely documented in the Phanerozoic orogenic belts, limited stuides have been conducted on Paleoproterozoic Barrovian metamorphic series. In this contribution, Barrovian metamorphic series extending from biotite to kyanite zones in the middle of Jiao-Liao-Ji Orogenic Belt (JLJOB) from eastern part of North China Craton (NCC) was investigated. The current studies identified the occurrence of polyphase deformation and metamorphism within the Langzishan Barrovian metamorphic series. D 1 fabrics are characterized by the development of S 1 foliation and L 1 lineation in association with greenschist facies metamorphism (M 1) that occurrs at ca. 490 ℃ and ca. 5.7 kbar. D 2 fabrics that include different folds (F 2), S 2 crenulation cleavage, S 2 foliation and L 2 lineation, accompanied by the low amphibolite metamorphism (M 2) that occurrs at ca. 670 ℃ and 8.2–8.6 kbar. D 3 fabrics involving kink band postdate sillimanite growth that occurrs at ca. 660 ℃ and ca. 6.5 kbar, and predate chlorite occurrence. Monazite U-Pb dating suggests the peak and retrograde metamorphic ages of ca. 1.93 Ga and 1.86 Ga, respectively. Thus, a clockwise pressure–temperature-time-deformation (P-T-t-D) path is established, possibly related to the crustal thickening process. These features are very similar to those documented in Phanerozoic Barrovian metamorphic series, suggesting that a comparable orogenesis mechanism could be shared in the Paleoproterozoic and Phanerozoic. [ABSTRACT FROM AUTHOR]

The pressure-temperature-time (P-T-t) evolution of metamorphic rocks is directly related to geodynamics as different tectonic settings vary in their thermal architecture. The shapes of P-T paths and thermobaric ratios (T/P) of metamorphic rocks have been extensively used to distinguish different tectonic domains. However, the role of metamorphic timescales in constraining tectonic settings remains underutilized. This is because of the poorly understood relationship between them, and the difficulty in accurately constraining the onset and end of a particular metamorphic event. Here, we show why and how the intrinsic relationship between thermal regime, rheology and rate of motion controlled by the heat, mass and momentum conservation laws translate to differences in heating, cooling, burial, exhumation rates of metamorphic rocks and thereby, to the duration of metamorphism. We compare the P-T-t paths of the orogenic metamorphic rocks of different ages and in particular, analyse their retrograde cooling rates and durations. The results show that cooling rates of the metamorphic rocks are variable but are dominantly <50 °C/Ma during most of the Precambrian before increasing by an order of magnitude (>100 °C/Ma) during the late Neoproterozoic to Phanerozoic. To seek what controlled this secular change in metamorphic cooling rates, we use thermomechanical modelling to calculate the P-T-t paths of crustal rocks in different types of continental orogenic settings and compare them with the rock record. The modelled P-T-t paths show that lithospheric peel-back driven orogenic settings, which are postulated as an orogenic mode operating under the hotter mantle conditions of late Archean to early Proterozoic, are characterised by longer durations of metamorphism and slower cooling rates (a few 10s of °C/Ma) as compared to the modern orogenic settings (a few 100s of °C/Ma) operating under relatively colder mantle conditions. This is because peel-back orogens feature: (1) hot lithospheres with very high crustal geotherms being sustained by high mantle heat-flow and profuse magmatism, and (2) distributed deformation patterns that limit vertical extrusion (exhumation) of the metamorphic rocks along localized deformation zones and instead, trap them in the orogenic core for a long time. In contrast, modern orogens mostly involve colder lithospheres and allow rapid exhumation through localized deformation, which facilitates faster cooling of hot, exhumed metamorphic rocks in a colder ambience. Thus, we propose that the secular change in metamorphic cooling rates indicates a changing regime of orogenesis and thereby, of plate tectonics through time. Predominance of the slower metamorphic cooling rates before the Neoproterozoic indicate the occurrences of peel-back orogenesis and truncated hot (collisional) orogenesis during that time, while the appearance of faster cooling rates since the late Neoproterozoic indicates the transition to modern style of orogenesis. A transition between these orogenic styles also accounts for the prolonged longevity (>100 million years) of many Precambrian orogenic belts as compared to the Phanerozoic ones. This study underscores the strength of timescales in combination with P-T paths to distinguish tectonic settings of different styles and ages. [Display omitted] • Metamorphic cooling rates show a secular change. • Cooling rates were slower until the late Neoproterozoic • Changing styles of orogenesis explains this change in cooling rates. • Distributed deformation in Precambrian orogens account for the slowercooling • Localized deformation in modern orogens facilitate faster cooling. [ABSTRACT FROM AUTHOR]

Key in understanding the geodynamics governing subduction and orogeny is reconstructing the paleogeography of 'Greater India', the Indian plate lithosphere that subducted since Tethyan Himalayan continental collision with Asia. Here, we discuss this reconstruction from paleogeographic, kinematic, and geodynamic perspectives and isolate the evolution scenario that is consistent with all three. We follow recent constraints advocating a ~58 Ma initial collision and update a previous kinematic restoration of intra-Asian shortening with a recently proposed model that reconciles long-debated large and small estimates of Indochina extrusion. Our new reconstruction is tested against paleomagnetic data, and against seismic tomographic constraints on paleo-subduction zone locations. The resulting restoration shows ~1000–1200 km of post-collisional intra-Asian shortening, leaving a 2600–3400 km wide Greater India. From a paleogeographic, sediment provenance perspective, Eocene sediments in the Lesser Himalaya and on undeformed India may be derived from Tibet, suggesting that all Greater Indian lithosphere was continental, but may alternatively be sourced from the contemporaneous western Indian orogen unrelated to India-Asia collision. A quantitative kinematic, paleomagnetic perspective prefers major Cretaceous extension and a 'Greater India Basin' opening within Greater India, but data uncertainty may speculatively allow for minimal extension. Finally, from a geodynamic perspective, assuming a fully continental Greater India would require that subduction rates close to 20 cm/yr was driven by a down-going lithosphere-crust assemblage more buoyant than the mantle, which seems physically improbable. We conclude that the Greater India Basin scenario is the only sustainable one from all three perspectives. We infer that old pre-collisional lithosphere rapidly entered the lower mantle sustaining high subduction rates, whilst post-collisional continental and young Greater India basin lithosphere did not, inciting the rapid India-Asia convergence deceleration ~8 Myr after collision. Subsequent absolute northward slab migration and overturning caused flat slab subduction, Tibetan shortening, arc migration and arc volume decrease. Unlabelled Image • Following 58 Ma India-Asia collision, Asia shortening 1000-1200 km and 2600-3400 km of (Greater) India subducted • Combined paleogeographic, kinematic, and geodynamic constraints strongly suggest a Greater India Basin scenario • Post-58 Ma upper mantle slab buckling induced flat slab subduction causing India-Asia slowdown and Tibetan shortening [ABSTRACT FROM AUTHOR]

Abstract In this paper we present a series of thermo-mechanical experiments on continent-continent collision zones to investigate the role of lateral strength contrasts in terms of collision dynamics and orogen geometries. Our results show that differences in crustal rheology, may lead to a variety of different patterns of deformation and crustal geometries. Upper plate indentation forms a sequence of foreland propagating thrust units made of brittle upper crust on the lower plate. The strong deformation of the lower plate stands in stark contrast to the undeformed upper plate. In contrast, subduction of strong lithosphere beneath a weak upper plate forms a complex pattern of deformation. Deformation initiates on the lower plate and forms an antiformal stack made of brittle upper crust, before it indents the upper plate. Hence, deformation is present on both, the lower and upper plate, despite differences in initial strength. The outcome of this study has direct implications to natural collision zones, where differences in strength between the upper and lower plate exist. For example, along strike variability of upper vs. lower plate shortening in the Alps are likely to be controlled by contrasts in crustal strength. Furthermore, we suggest that the antiformal stack in the axial zone of the Pyrenees might indicate a strong lower plate at the onset of collision. Our results may therefore provide important constraints for the rheological state of continents during collision. Graphical abstract Image 1 Highlights • We study influences of crustal strength contrasts on continent-continent collision. • Crustal deformation always migrates from the stronger into the weaker plate with time. • Large-scale mountain geometries are controlled by crustal strength variations. [ABSTRACT FROM AUTHOR]

Although the Helvetic nappes of the Western Alps have been widely studied, their style, amount, and timing of deformation during the Alpine orogeny remain a subject of controversy. The discussion partly arises from various interpretations of the external crystalline massifs geometry and of the cover/basement relationships. Here, we apply structural analysis based on new field data, microtectonics, and 3D geological modeling on the Aiguilles Rouges and Mont-Blanc massifs, to better quantify their tectonic evolution and their relationship with the nappe stacking. Our results show large thrusting of the Helvetic Mesozoic sedimentary cover above the Aiguilles Rouges basement towards the WNW. The basal contact of the Helvetic nappes, which we call the Helvetic Basal thrust (HBT), often corresponds to a décollement level localized above the Triassic unconformity, but that locally also affects the basement. We suggest that most of the subalpine ranges are klippes above the HBT, and estimate the shortening of the thrust from previously published cross-sections to be between 13 and 32 km. According to published ages, we argue that the HBT was active in the Oligo-Miocene, between ∼30 and ∼14 Ma. After ∼14 Ma and until ∼6 Ma, the HBT is offset by late steep out-of-sequence faults, including back-thrusts and the Mont-Blanc shear zone that was previously a ramp of the HBT. The transition of the major thrust system from the HBT rooting above (east) of the Mont-Blanc to the Alpine sole thrust rooting below (west) of the Aiguilles Rouges occurred between 18 and 14 Ma. • Structural analysis and 3D mapping of the Aiguilles Rouges and Chamonix zone. • Thrust of the Mesozoic sedimentary cover ∼30 km WNW at 30–14 Ma. • Steep thrusts in the Miocene (14–6 Ma). • 15 Ma long Helvetic thrusting has been overlooked in alpine orogeny models. [ABSTRACT FROM AUTHOR]

For many tectonicists, the structural development of the northern Tibetan Plateau stops at the Altyn Tagh Fault (ATF). This study challenges that assumption. Structural field observations and remote sensing analysis indicate that the Sanweishan and Nanjieshan basement cored ridges of the Archean Dunhuang Block, which interrupt the north Tibetan foreland directly north of the ATF, are bound and cut by an array of strike-slip, thrust and oblique-slip faults that have been active in the Quaternary and remain potentially active. The Sanweishan is a SE-tilted block that is bound on its NW margin by a steep south-dipping thrust fault that has also accommodated sinistral strike-slip displacements. The Nanjieshan consists of parallel, but offset basement ridges that record NNW and SSE thrust displacements and sinistral strike-slip. Regional folds characterize the extreme eastern Nanjieshan and appear to have formed above blind thrust faults which break the surface further west. Previously published magnetotelluric data suggest that the major faults of the Sanweishan and Nanjieshan ultimately root to the south within conductive zones that are inferred to merge into the ATF. Therefore, although the southern margin of the Dunhuang Block focuses significant deformation along the ATF, the adjacent cratonic basement to the north is also affected. Collectively, the ATF and structurally linked Sanweishan and Nanjieshan fault array represent a regional asymmetric half-flower structure that is dominated by non-strain partitioned sinistral transpression. The NW-trending Dengdengshan thrust fault system near Yumen City appears to define the northeastern limit of the Sanweishan-Nanjieshan block, which may be regionally viewed as the most northern, but early-stage expression of Tibetan Plateau growth into a slowly deforming, mechanically stiff Archean craton. [ABSTRACT FROM AUTHOR]

The Eurekan Orogeny, which created much of the high topography of Ellesmere Island and adjacent Greenland, exhibits a crustal architecture linked to intraplate orogenesis in the Cenozoic. It is generally considered that the rotation of Greenland in the Eocene (related to sedimentary basin formation in Baffin Bay) produced compressional intraplate tectonics. Deformation in the region is notably localized to the Central Ellesmere Domain and the Northern Ellesmere Domain. However, an important tectonic feature of Ellesmere Island is the Hazen Stable Block, which shows horizontal Paleogene Eureka Sound group strata overlying Palaeozoic-age steeply dipping beds. The intense deformation in the Hazen Stable Block is related to continental orogenesis in the Late Silurian–Devonian. Therefore, the Hazen Stable Block is thought to have undergone only minor Eurekan-age (55–35 Ma) deformation, while surrounding (highly deformed) units may have re-activated faults from Paleocene continental amalgamation. Here, high-resolution thermal–mechanical numerical experiments are implemented to explore lithospheric deformation (related to continental shortening) for a range of tectonic scenarios, namely, the presence of inherent deformational “scars” and rheologically strengthened crust/mantle lithosphere (both due to ancient continental accretion). This study marks the first geodynamic excursion to this high Arctic region, and we present some of the first interpretations of the development of Eurekan-age lithospheric evolution. Our results show that a rheologically strong Hazen Stable Block crust produces tectonics similar to the Eurekan Orogeny. Furthermore, lithospheric scars can generate more localized deformation and topography than rheological changes to the lithosphere and may offer a new interpretation on enigmatic intraplate tectonics. [ABSTRACT FROM AUTHOR]

The observation that sediment flux from mountain ranges struck by high magnitude earthquakes can be strongly influenced by coseismic mass movements brings into question the nature of coseismic deformation as a net contributor to mountain building. To better constrain the role of high-magnitude earthquakes in orogenesis, high-resolution data of earthquake induced mass wasting is required for areas of differing tectonic, morphological, and climatic settings. Here we compare the erosional flux to the tectonic flux associated with the 2010 M w = 7.2 Sierra El Mayor earthquake in Mexico and examine the landslide patterning of coseismic mass movements associated with this event. The ruptured fault system has a significant strike-slip component with subsidence along the eastern flank and uplift on the western flank of the range. Peak ground acceleration was highest along the steepest sections of the range such that the frequency of landslide occurrence was strongly correlated to slope gradient. Both vertical and horizontal coseismic displacement demonstrated a strong control over landslide initiation. This result suggests that strike-slip systems experience very different landslide patterning to thrust faults during earthquakes. Based on interferometric analysis of synthetic aperture radar images, the earthquake resulted in a total uplifted volume of 41.6 × 10 6 m 3 and a loss of 95.2 × 10 6 m 3 due to subsidence. This suggests a net tectonic volumetric flux of − 53.6 × 10 6 m 3 . Sediment mobilisation by coseismic landslides is estimated at − 2.7 × 10 6 m 3 derived from a manually mapped inventory using SPOT 5 multispectral imagery. Thus, the net volume loss through coseismic subsidence of the mountain range generated a strongly negative mass flux, which was only marginally enhanced by mass wasting. [ABSTRACT FROM AUTHOR]

The assembly and dispersion of continental crust are first-order controls on paleogeography and geochemical cycles. The associated reworking of Earth's crust can be tracked with zircon initial hafnium (ε Hf T) through space and time. Here we apply a new method of quantitative analysis using ε Hf T density estimates based on a compilation of 155,329 ε Hf T values. Investigation of the global database reveals significant geographic and temporal bias in the ε Hf T record associated with sampling and regional tectonic events. Recent research has attempted to address global ε Hf T bias using resampling methods to augment gaps of low ε Hf T data density, which in turn obfuscates tectonic signals and artificially weights outliers. Instead, we evaluate ε Hf T density patterns for both igneous and detrital zircon on eight continental zones demarcated by Paleozoic sutures: Africa, Antarctica, Asia, Australia, Baltica, North America, Peri-Gondwana, and South America. Pairwise two-dimensional quantitative comparison highlights similarity in timing and ε Hf T values between zones, all of which can be linked to documented shared regional tectonism. Integration of all pairwise comparisons reveals that peak similarity corresponds to the timing of supercontinent amalgamation, and that the associated ε Hf T differs depending on the style of supercontinent amalgamation, particularly internal versus external orogenesis. The three most recent supercontinents produced distinctive ε Hf T signals, shared by the constituent continental zones. The supercontinents Rodinia and Pangea were constructed through collisions of marginal arc terranes, peripheral to ancient crust, and did not produce highly enriched ε Hf T values. In contrast, Ediacaran to Cambrian formation of the Gondwana supercontinent was largely the product of internal Pan-African orogens that formed directly after Neoproterozoic Rodinia rifting and arc accretion forming the Arabian Shield. The final assembly of Gondwana was dominated by continent-continent collisions of old radiogenic crust without establishment and accretion of extensive intervening depleted arc terranes, resulting in a more enriched distribution of ε Hf T values compared to prior and subsequent supercontinent formation. The secular ε Hf T record is the product of spatiotemporally biased sampling and preservation of specific orogenic belts with predictable ε Hf T data arrays, modulated by the amalgamation, tenure, and breakup of supercontinents through time. • Zircon Hf is predictable based on tectonic context. • Global Hf records are geographically and temporally biased. • All major Hf excursions can be linked to regional orogenic events. • Zircon Hf is modulated by the amalgamation, tenure, and breakup of supercontinents. [ABSTRACT FROM AUTHOR]

Abstract: New SHRIMP U/Pb zircon ages of 472.2±5.8Ma and 471.2±5.9Ma are presented for the age of peak metamorphism of Barrovian migmatites. 40Ar/39Ar ages for white mica from the Barrovian metamorphic series are presented, and are recalculated using recently-proposed revisions to the 40K decay constants to allow more precise and accurate comparison with U/Pb ages. The 40Ar/39Ar ages are found to vary systematically with increasing metamorphic grade, between c. 465Ma for the biotite zone and c. 461Ma for the sillimanite zone. There is no evidence for any significant metamorphic heating during the first 15Myr of the Grampian Orogeny (before c. 473Ma) or the final 4Myr (after c. 465Ma). The Barrovian metamorphism occurred over a period of ~8Myr within the ~27-Myr Grampian Orogeny. The Barrovian metamorphism records punctuated heating, was temporally and spatially associated with large-scale bimodal magmatism, and developed within crust that was not overthickened. The temporally distinct nature of the Barrovian metamorphic episode within the Grampian Orogeny, and its heating pattern and tectonic context, are not consistent with significant heat contribution from thermal equilibration of overthickened crust. Rather, the Barrovian metamorphism records a transient phase of crustal thermal disequilibrium during the Grampian Orogeny. Temporal and spatial association with Grampian bimodal magmatism is consistent with production of the Barrovian metamorphic series within the middle crust as the result of advection of heat from the lower crust and/or mantle. The Barrovian metamorphic series – the classic example of ‘orogenic regional metamorphism’ – did not form in response to crustal thickening and thermal relaxation, but appears to record large-scale contact metamorphism. [Copyright &y& Elsevier]

Abstract: The surface expression of a lateral polarity change of continental mantle lithosphere subduction has been studied by using lithosphere-scale physical models. Key parameters investigated were: the degree of lateral coupling between adjacent domains of opposing subduction polarity, the width of the zone separating the domains, and the lithosphere geometry and rheology. The model results illustrate an asymmetric lithospheric structure induced by deformation of the downgoing plates, which have been separated by a narrow transition zone. A wide and symmetric orogenic wedge overlying a region of thickened mantle lithosphere and hampered subduction characterizes this transition zone. In addition, interaction between the neighboring subduction domains caused downbending of the upper plates and resulted in the lateral termination of crustal structures and lowering of surface topography. The lateral extent of interaction between the domains strongly depends on the degree of coupling between the domains, the rheology of the mantle lithosphere and the amount of bulk shortening. The modelling results have major implications on the interpretation of seismic and tomographic data from the European Alps in terms of the crust and lithosphere geometries. It appears that an observed lateral change of subduction polarity at mantle depth can explain the variations of wedge build-up between the Western/Central and Eastern Alps. [Copyright &y& Elsevier]

Abstract: Trench motion and upper plate deformation ultimately respond to mantle flow. Herein I build upon the mantle flow model results of Conrad and Behn (2010) and compute the drag forces underneath all plates, and show that they control the dynamics of plates and plate boundaries. The small misfit angle between between the traction azimuths of mantle traction and absolute plate motion corroborates the idea that convective mantle drag is a prominent driver of plate tectonics. Less intuitive is the fact that the interplay between the drag forces from the upper and lower plates, that amounts to −5 to 8.5×1012 Nm−1 (per unit trench length), dictates both trench migration rates and upper plate deformation. At odds with the classic view that assigns the prime role to the idiosyncrasies of subduction zones (slab age, interplate friction, water content etc), I find that the intrinsic properties of subduction zones in fact only modulate this behavior. More specifically, the mean value of the integrated trenchward mantle drag force from the lower and upper plates (from −2 to 6.5×1012 Nm−1) controls upper plate deformation. Conversely, it is the difference between the lower and upper plates mantle drag forces (from −3 to 10×1012 Nm−1) that controls trench migration rates. In addition, I find that a minimum trenchward force of ∼2.5×1012 Nm−1 must be supplied by mantle drag before trenches can actually advance, and before upper plates undergo compression. This force results from the default tendency of slabs to rollback when solely excited by their own buoyancy, and is thus the effective tensional force that slab pull exerts on the plate interface. [Copyright &y& Elsevier]

Abstract: A growing set of data indicates a stark contrast between the evolution of two types of ultrahigh-pressure (UHP) terranes: large terranes that evolved slowly (over 10–30Myr), and small terranes that formed and were exhumed on timescales of <10Myr. Here we compare the characteristics – area, thickness, formation rate, exhumation rate, age, and tectonic setting – of these two endmember types of UHP terrane worldwide. We suggest that the two UHP terrane types may form during different orogenic stages because of variations in the buoyancy and traction forces due to different proportions of subducting crust and mantle lithosphere or to different rates of subduction. The initial stages of continent collision involve the subduction of thin continental crust or microcontinents, and thus tectonic forces are dominated by the density of the oceanic slab; subduction rates are rapid and subduction angles are initially steep. However, as collision matures, thicker and larger pieces of continental material are subducted, and the positive buoyancy of the down-going slab becomes more prominent; subduction angles become gentle and convergence slows. Assessing the validity of this hypothesis is critical to understanding the physical and chemical evolution of Earth''s crust and mantle. [Copyright &y& Elsevier]

Abstract: The geometric and kinematic evolution of the Andes provides insight onto the nature of the force balance beneath the South American plate. While the Andean load is opposed on its western edge by the force induced by subduction of the Nazca plate, its more elusive eastern counterpart, which we explore herein, requires some contribution from the mantle beneath the South Atlantic. Using a mantle flow model, we show that the Andes owe their existence to basal drag beneath South America caused by a cylindrical convection cell under the South Atlantic. We find that the observed Andean uplift requires both westward push from active upwelling beneath Africa and westward drag toward the downgoing Nazca slab. These mutually-reinforcing downwellings and upwellings amount to 38% and 23% of the total driving force, respectively. Further decomposition reveals that the South Atlantic cell is most vigorous near its center, rendering the net drag force higher where the Andes also reach their highest elevation. Kinematic reconstructions suggest that the South Atlantic cell could have grown owing to the migration of the Nazca slab until ~50Ma. We propose that from 50Ma onwards, the cell may have ceased growing westward because (i) it had reached an optimal aspect ratio and (ii) the Nazca slab became anchored into the lower mantle. Continued westward motion of the plates, however, moved the surface expressions of spreading and convergence away from the upwelling and downwelling arms of this cell. Evidence for this scenario comes from the coeval tectonic, morphologic, and magmatic events in Africa and South America during the Tertiary. [Copyright &y& Elsevier]

Abstract: Jupiter''s moon Io possesses numerous tectonic mountains in addition to its ubiquitous volcanoes and volcanic features. Remarkably, a distinct global anticorrelation exists between the spatial distribution of mountains and volcanic centers on Io. This relationship indicates an explicit connection between volcanism and mountain formation, even though the mountains are tectonic in origin (predominantly upthrusted crustal blocks). Spherical harmonic analysis shows the distribution of mountains and volcanic centers have statistically significant power at degree 2; this result is especially striking for the volcanic center distribution, and directly implicates models of asthenospheric tidal heating. The latter predict enhanced heat flux along the equator in a degree-two pattern that matches observations. Mountain formation on Io appears to be a form of dominantly vertical tectonism unique in the modern Solar System: continual burial by widespread volcanism drives the crust inward, which leads to strong compression, and at discrete locations, mountains. Correlation coefficients between the volcanic and mountain distributions indicate statistically meaningful anticorrelation at low spectral degrees (l =1, 2, 4, and 6); the anticorrelation is especially significant between the longitudinal (sectorial) l =2 components when considered on their own. We compare this anticorrelation with published models that link volcano and mountain formation. While consistent in part with l =2 convection models, which predict such an anticorrelation (in principle), such low degree anticorrelations are also (if not more) compatible with mountain formation due to, or influenced by, thermal expansion of Io''s crust, and deep compression and thrust faulting in regions of lower than average volcanic heat-piping. Positive correlations between mountain and volcanic center distributions at high spectral degree may reflect structural links between a good fraction of mountain blocks and adjacent volcanic paterae, whereas the anticorrelation at low degree implies that most volcanic features (which are far more numerous overall) form independently of mountains. [Copyright &y& Elsevier]

Abstract: Large scale tectonic mode switches from lithospheric shortening to lithospheric extension may play a fundamental role in the tectonometamorphic evolution of orogens located along convergent plate margins. Short-lived episodes of lithospheric extension can be inferred from the concomitant occurrence of bimodal magmatism, rapid exhumation of rock units, activity of extensional shear zones, steep geothermal gradients and, possibly, topographic collapse of the orogenic belt. Here we provide a synthesis of existing data from the European Alps, supporting the hypothesis on tectonic mode switches. Data are interpreted to suggest that at ca. 38–34Ma a period of N–S (orogen perpendicular) shortening led to the formation of medium to ultra-high-pressure mineral assemblages by lithosphere-scale thrust imbrication. A tectonic mode switch took place at ca. 34Ma, marked by the onset of E–W extension. During this extensional event, internal units of the Western and Central Alps were rapidly exhumed to mid-crustal level in the footwall of regional-scale extensional shear zones. Tectonic thinning was also accomplished through pervasive E–W stretching of the nappe pile. Lithospheric stretching resulted in the onset of an anomalous thermal regime, which was responsible for the overprint of the older medium- to ultra-high pressure mineral assemblages by Barrovian-type mineral assemblages and by migmatization. At the same time, attenuation of the isotherms led to partial melting of mantle lithosphere and to bimodal magmatism. Contemporaneous topographic collapse of the orogen is suggested by the deposition in the foreland of flysch units rich in minerals that were probably derived from erosion of the Early Oligocene calc-alkaline volcanics erupted in the hinterland. This short-lived episode of lithospheric stretching took place in no more than 4myr, from ca. 34Ma to ca. 32–30Ma. Renewed lithospheric thickening, which is observed in seismic tomography studies, resulted in large-scale folding of the extensional structures and the in rapid generation of topographic relief, feeding abundant clastic sedimentation in the peripheral basins. [Copyright &y& Elsevier]

Abstract: Unveiling how the interaction of friction (μ), pore pressure (p) and normal stress (σ n) controls the shear strength distribution along megathrust faults at convergent plate boundaries is crucial to our understanding of processes leading to the occurrence of devastating earthquake and the construction of mountains. An existing density model of the Chilean margin (18°–45°S) allows the computation of the so-called Vertical Stress Anomaly (VSA) that accounts for the component of normal stress due to the weight of the overlying crustal column. A spatial correlation between VSA, surface geology and several earthquake parameters suggests a significant control exerted by the geologically-dominated density structure of the crust on megathrust shear strength. The very seismogenic forearc in front of the high Central Andes (18°–34°S) has positive VSA values (up to 60MPa) and a mafic-dominated crust, which suggest high values of shear strength at the megathrust that are partially controlled by the weight of a dense forearc crustal column, in addition to a likely dry subduction channel characterized by high-μ and low-p. In contrast, the Southern Andean forearc (34°–45°S) shows neutral-to-negative VSA (down to −30MPa) correlated with a felsic-dominated crust, which added to a presumably wet subduction channel (low-μ and high-p) configures a rather weak megathrust below a light forearc. Earthquakes here are concentrated around the Arauco peninsula, a first-order morpho-structural anomaly characterized by comparatively higher values of VSA than the rest of this segment, which is the nest of the giant (Mw 9.5) Valdivia 1960 earthquake and the southern rupture termination of the recent Mw 8.8 Maule earthquake. The ultimately giant size of the 1960 earthquake resulted from rupture propagation along a 1000km long region characterized by negative VSA values. The correlation between VSA and the along-strike segmentation of the Andean orogen indicates that the geologically-inherited density structure of the forearc also rules long-term mechanical coupling between converging plates and prescribes the possible structure of the orogen. Because Central and Southern Andes represent two extremes in terms of orogenic structure and seismogenic behavior, results presented here have significant implications for the general comprehension of processes occurring at short and long time scale at convergent margins. [Copyright &y& Elsevier]

The Pressure–Temperature–time–deformation evolution of the high- to ultra-high-pressure units of the Western Alps has been progressively refined in the last 40years, leading to several paradigm shifts in the understanding of orogenesis. This set of information, combined with Cretaceous–Tertiary plate kinematic reconstructions and Mesozoic palaeogeography, indicates that the Western Alps represent the amalgamation of a Cretaceous and an Eocene orogen, which developed at the expense of the Adriatic and European rifted margins, respectively. In the Cretaceous, NNE-directed drift of the Adriatic plate, parallel to the inherited Jurassic structural trends, led to the development of a highly oblique subduction boundary. In this setting, the Canavese Zone and parts of the Sesia Zone, derived from the hyper-extended Adriatic margin, underwent deformation and metamorphism at conditions ranging from sub-greenschist to eclogite facies. A Lower Eocene switch to NNW-directed motion, perpendicular to the rift-related Jurassic structural trends, culminated in the collision between the proto-Alps and the Briançonnais block at ca. 44Ma. As a result, the Briançonnais Domain and parts of its hyper-extended margin, preserved in the (U)HP Piemonte Units, were accreted to the orogen. Continued convergence was subsequently accommodated by subduction of the more external Valaisan basin and of the thinned European margin. The arrival of thick European continental crust at the subduction zone at ca. 35–30Ma marked the onset of the final continental collision. To a first order, the orogen grew through the progressive episodic accretion of units located towards north-westerly positions. Accretion of subducting units at the front of the orogen was coeval with kinematic reworking of tectonic contacts in the hangingwall units, locally resulting in renewed deformation/metamorphism. [Copyright &y& Elsevier]

Abstract: Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one of the converging plates is oceanic and plunges beneath the other into the mantle, or a collision zone, where two continents or a continent and a magmatic arc collide. Convergent plate margins are arguably the most complicated and dynamic plate boundaries on Earth and have been the subject of many investigations and discussions since the advent of plate tectonic theory. This paper provides a historical background and a review of the development of geological and geodynamic theories on convergent plate margins. Furthermore, it discusses some of the recent advances that have been made in the fields of structural geology, geophysics and geodynamics, which are fundamental to our understanding of this phenomenon. These include: (1) the finding that plates and plate boundaries move at comparable velocities across the globe; (2) the emerging consensus that subducted slabs are between two to three orders of magnitude stronger than the ambient upper mantle; (3) the importance of lateral slab edges, slab tearing and toroidal mantle flow patterns for the evolution of subduction zones; and (4) clear evidence from mantle tomography that slabs can penetrate into the lower mantle. Still, many first-order problems regarding the geodynamic processes that operate at convergent margins remain to be solved. These include subduction zone initiation and the time of inception of plate tectonics, and with it convergent plate margins, on Earth. Fundamental problems in orogenesis include the mechanism that initiated Andean mountain building at the South American subduction zone, the potential episodicity of mountain building with multiple cycles of shortening and extension, and the principal driving force behind the construction of massive mountain belts such as the Himalayas–Tibet and the Andes. Fundamental questions in subduction dynamics regard the partitioning of subduction into a trench and plate component, and the distribution of energy dissipation in the system. In seismic imaging, challenges include improving resolution at mid to lower mantle depth in order to properly understand the fate of slabs, and better constraining the 3-D flow-related anisotropic structure in the surrounding mantle. Future insights into such fundamental problems and into the regional and global dynamics of convergent plate margins will likely be obtained from integrating spatio-temporal data, structural geological data, geophysical data and plate kinematic data into plate tectonic reconstructions and three-dimensional geodynamic models of progressive deformation. [Copyright &y& Elsevier]

Abstract: The Early–Middle Miocene exhumation of the crystalline core of the Himalaya is a relatively well-understood process compared to the preceding phase of burial and prograde metamorphism in the Eocene–Oligocene. Highly deformed rocks of the Greater Himalayan Sequence (GHS) dominate the crystalline core, and feature a strong metamorphic and structural overprint related to the younger exhumation. The Tethyan Sedimentary Series was tectonically separated from the underlying GHS during the Miocene by the South Tibetan Detachment, and records a protracted and complex history of Cenozoic deformation. Unfortunately these typically low-grade or unmetamorphosed rocks generally yield little quantitative pressure–temperature–time information to accompany this deformation history. In parts of the western Himalaya, however, the basal unit of the Tethyan Sedimentary Series (the Haimanta Group) includes pelites metamorphosed to amphibolite facies. This presents a unique opportunity to explore the tectono-thermal evolution of crystalline rocks which record the early history of the orogen. Pressure–temperature–time–deformation (P–T–t–d) paths modelled for two Haimanta Group pelitic rocks reveal three distinct stages of metamorphism: (1) prograde Barrovian metamorphism to 610–620 °C at c. 7–8 kbars, with garnet growing over an early tectonic fabric (S1); (2) initial decompression during heating to 640–660 °C at c. 6–7 kbars, with development of a pervasive crenulation cleavage (S2) and staurolite and kyanite porphyroblast growth; (3) further exhumation during cooling, with minor retrograde metamorphism and modification of the pervasive S2 fabric. Monazite growth ages constrain the timing of initial garnet growth (>34 Ma), the start of D2 and maximum burial (c. 30 Ma), and the termination of garnet growth (c. 28 Ma). Muscovite Ar/Ar ages indicate cooling through c. 300 °C at c. 13 Ma, from which we derive an initial exhumation rate of c. 1.3 mm year−1 for the Haimanta Group. The underlying GHS was exhumed at a rate of 2.2 to 3 mm year−1 during this time. The difference in exhumation rate between these two units is considered to reflect Early Miocene displacement on the intervening South Tibetan Detachment. Slower exhumation (c. 0.6 mm year−1) of both units after c. 13 Ma followed the cessation of major displacement on this structure, after which time the Haimanta Group and the GHS were exhumed as one relatively coherent tectonic block. [Copyright &y& Elsevier]

Abstract: A high degree of correlation between present-day relative rock uplift measured using continuous GPS geodesy and spatially averaged surface elevations suggests that long-wavelength topographic relief is presently increasing along the southeastern flank of the Sierra Nevada range and within an adjacent portion of the northern Basin and Range province. Current estimates for erosion rate are an order of magnitude smaller than the relative rates determined by geodesy. Thus, although the uplift serves to enhance long-wavelength relief, it cannot be explained entirely as an isostatic response to erosion. If uplift rates have been constant through time, the duration over which the uplift could have been active (<1.6Myrs) is shorter than expected based on our current understanding of the geodynamic history of the region. One possible explanation for the observed present-day uplift pattern is that it represents an ongoing isostatic response to gradual reduction of the equivalent elastic thickness (EET) of the lithosphere under temporally constant loads. Another explanation is that the loads currently supporting the high elevations of the southern Sierra are evolving with time. According to either hypothesis, vertical surface motions may have slowly accelerated since ~mid-Pliocene time. Several possible mechanisms for progressive reduction of EET may be attributable to thermo-mechanical disequilibrium that began with the removal of an ultramafic root from the Sierran batholith during late Miocene or early Pliocene time. Specific mechanisms for ongoing enhancement of loads are less obvious. Based on these results, we suggest that dense networks of long-running continuous GPS stations around the world currently represent an underutilized resource for studies of orogenesis and upper mantle processes. [Copyright &y& Elsevier]

Central Anatolia (Turkey) is a small and nascent example of a high orogenic plateau, providing a natural laboratory to study processes driving plateau rise. The 1-km-high plateau interior uplifted since c. 8–5 Ma, with a further phase of kilometre-scale uplift affecting the southern plateau margin since 0.45 Ma. Several causes of plateau rise have been proposed: peeling or dripping delamination of the lithospheric mantle; asthenospheric upwelling through slab gaps created by slab fragmentation or break-off, and; continental underthrusting and crustal shortening below the southern plateau margin. The Neogene history of the plateau has not been diagnostic of the causes of plateau rise. We thus evaluate proposed uplift causes in the context of the Anatolian orogenesis, which formed the plateau lithosphere during subduction since the Cretaceous. We combine this analysis with available constraints on uplift, and geophysical data that illuminate the modern mantle (and crustal) structure. Our analysis suggests that lithospheric dripping, which followed arc magmatism and shortening in the Kirsehir Block (eastern Central Anatolia), is the most likely cause of plateau interior uplift. Lithospheric dripping is, however, an unlikely sole driver of multi-phase uplift along the southern plateau margin. There, underthrusting of the African continental margin, recorded by c. 11–7 Ma thrusting on Cyprus, is a viable cause of uplift since 0.45 Ma, but cannot account for earlier uplift since c. 8–5 Ma. Instead, slab break-off below the southern plateau margin is likely in light of geophysical data. On the SW plateau margin, small-scale peeling delamination of the Central Taurides by the Antalya slab since early Miocene times accounts for >150 km slab retreat with no corresponding upper-plate deformation. A southwest-travelling wave of subsidence and uplift signalled this retreat and may have contributed to coeval oroclinal bending of the western Central Taurides and southeastward thrusting of the Lycian Nappes. • Lithospheric dripping is compatible with the orogenic evolution since the Cretaceous. • Cyprus slab break-off at c. 8–5 Ma related to initial south plateau margin uplift. • Subduction of African margin a viable cause of 0.45 Ma south plateau margin uplift. • Small-scale peeling delamination a driver of Antalya Basin subsidence and uplift. [ABSTRACT FROM AUTHOR]

Abstract: Basin-averaged cosmogenic 10Be concentrations, apatite (U–Th)/He thermochronometry and incision into a dated palaeosurface constrain spatial and temporal variations in the rates of denudation experienced during the early-stages of orogenesis in the San Bernardino Mountains, California. Cosmogenic 10Be analysis measures denudation over intermediate (∼102–104 years) time scales and records rates which decrease from a maximum of 2700±500 mm ka−1 in the south to a minimum of 52±5 mm ka−1 in northern catchments. Corresponding rates from (U–Th)/He and incision into a dated palaeosurface measure long-term (∼106 years) denudation rates which decrease from between 1200±400 mm ka−1 in the south to a minimum of 30±20 mm ka−1 in the north. The temporal consistency observed in the broad-scale patterns of denudation rates probably results from the persistent imprint of the initial crustal architecture and drainage network. These have maintained an influence on slope distributions, and are thus fundamental factors controlling the gross patterns of denudation throughout the early stages of orogenesis. Where variations between the denudation rates measured over different time scales are apparent the intermediate-term rates are found to be consistently greater than the long-term, with the increase being more pronounced around the fault bounded peripheries of crustal blocks relative to quiescent block interiors. This provides empirical support for a model of mountain building whereby topographic development is dictated by the headward retreat of drainage systems that propagate away from zones of displacement. Our findings indicate that recent localised increases in denudation rates in young fault block orogens may be explained by a progressive denudational response to prior tectonic uplift, rather than a consequence of climatic change. [Copyright &y& Elsevier]

Abstract: The origin of high temperatures during regional low-pressure granulite facies metamorphism within the Proterozoic Broken Hill Block, Australia, has been reinterpreted to be the result of burial of anomalously hot rock packages for which the lithospheric geothermal gradient was initially elevated during early rifting ca. 1.71–1.67Ga, and then maintained during a ca. 1.62Ga short-lived mid-crustal extensional event. Mid-crustal extension at ca. 1.62Ga was associated with amphibolite facies metamorphism and elevated lithospheric geothermal gradients, and occurred prior to activity along D2 high-temperature shear zones, peak low-pressure granulite facies metamorphism (ca. 1.60Ga) and crustal shortening during the Olarian Orogeny (ca. 1.60–1.59Ga). This reinterpretation places the Broken Hill Block within an environment in which multiple episodes of transient extension (ca. 1.71–1.62Ga) were followed by a switch to shortening at ca. 1.60Ga. The interpreted tectonic environment is a continental back-arc setting located in the over-riding plate of a subduction zone along the southern margin of Palaeoproterozoic Australia. [Copyright &y& Elsevier]

Abstract: Evidence of two burial–exhumation cycles that took place during a single orogeny has been found in rocks belonging to the Piemonte unit of the Western Alps. An early high pressure event, which resulted from tectonic burial down to pressures of 1.5 GPa, was followed by exhumation to ca. 0.20–0.35 GPa as a result of extensional deformation. Renewed shortening culminated in a second burial episode down to pressures of 0.65–0.80 GPa, before the final exhumation took place. Existing geochronological data allow only ca. 13–19 Ma for the completion of both burial–exhumation cycles. Therefore, we suggest that the evolution of orogens is characterized by multiple short-lived burial–exhumation cycles related to orogen-scale alternance between shortening and extensional deformation. [Copyright &y& Elsevier]

Abstract: Seventy skarn-type gold deposits, including 1 super-large, 19 large and 24 medium-sized, are known from different geotectonic units of China. They contain a total resource of approximately 1000 t of gold (625 t in South China), and account for 20% of China''s gold reserves. These skarn deposits are sited in collisional orogenic belts, fault-controlled magmatic belts and reactivated cratonic margins. All of the Chinese skarn gold provinces were affected by Phanerozoic collisional orogenesis. The timing of the metallogenic events and the spatial–temporal distribution of the Chinese skarn gold deposits indicates that they were formed during ore-forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen, and not to subduction systems as is commonly advocated for porphyry copper systems around the Pacific Rim. [Copyright &y& Elsevier]

Abstract: Among the south Asian Sericini only a very few endemic monophyletic lineages developed in the lowland areas, such as the taxa belonging to Maladera (subgenus Cycloserica). Twenty species of Sericini (Coleoptera: Scarabaeidae) representing the principal lineages of Maladera occurring in the Palearctic region were included in a parsimony analysis based on 37 morphological characters. Maladera (Cycloserica) was found be monophyletic, composed by a clade comprising (Maladera caspia (Cycloserica excisipes, Leucoserica arenicola)) being distributed in the Middle Asian lowlands and its sister group the Maladera quinquidens-group with four endemic species in the Himalayan and North Indian lowlands. The ranges of these two clades as well as of the sister group of Cycloserica reveal a separating effect by the uplifted Himalayan–Alpine belt. It is hypothesized that these two Cycloserica lineages existed before they dispersed into the two separated areas, the northern Indian subcontinent (Himalayas) and the Middle Asian lowland. Due to the sister group relationship of Cycloserica and Leucoserica, both nested deeply within the species of Maladera, it seems reasonable to consider both synonymous with Maladera. Based on this conclusion one new combination is necessary, Maladera (Cycloserica) arenicola, and Leucoserica Reitter, 1896, is placed in synonymy with Cycloserica Reitter, 1896). [Copyright &y& Elsevier]

Abstract: The sediment archive, of material eroded from an active tectonic region and stored in adjacent basins, can provide a valuable record of hinterland tectonism especially when information in the source region itself is obscured by later metamorphism or removed by tectonism or erosion. Using the sediment record to document tectonism is a well established approach, but more recently there has been a burgeoning of the number of isotopic techniques which can be applied to detrital material, in particular single-grain analyses. Thus the scope for application of detrital studies to a number of different tectonic problems has widened considerably. In this review, the example of sediments eroded from the Himalayan orogen and preserved in the suture zone basin, foreland basin, remnant ocean basins and deep sea fans is used to illustrate the approach. Techniques as diverse as petrography, heavy mineral, XRF and Sr–Nd studies; single grain dating by Ar–Ar, U–Pb and fission track methodologies; and single grain Sm–Nd and Pb isotopic analyses, are described. The paper documents how the sediment record can be used to determine the thermal and tectonic evolution of the orogen, constrain mechanisms of continental deformation, exhumation rates and palaeodrainage. [Copyright &y& Elsevier]

Abstract: During Upper Triassic to Lower Jurassic time, arc magmatic rocks of the Stikine terrane, arc-marginal sediments of the Whitehorse Trough, igneous and mantle rocks of the Cache Creek ‘ophiolite’ and Kutcho assemblage, and oceanic sedimentary and volcanic rocks of the Cache Creek terrane represented a magmatic arc, forearc basin, forearc basement, and subduction complex, respectively. The Cache Creek subduction complex was thrust to the southwest over the Whitehorse Trough forearc basin and the Stikine terrane in the Middle Jurassic during collision with an inboard continental domain. Interpretation of the various lithotectonic assemblages of the northern Intermontane belt in terms of a new plate tectonic model has a number of important implications for the Canadian Cordillera: (a) the model allows comparisons to be drawn with available seismic reflection interpretations of Cordilleran crustal structure; (b) ‘ophiolite’ emplacement was achieved by ramping of forearc oceanic lithosphere onto thick crustal parts of a subducting plate during collisional orogenesis; (c) island–arc collision and accretion were the principal mechanisms for continental growth with relatively minor contributions from ‘sliced-off’ oceanic seamounts and/or plateaux; and (d) some terrane-bounding faults such as the Nahlin Fault do not represent major lithospheric-scale boundaries and their importance in tectonic reconstructions has been overemphasised. [Copyright &y& Elsevier]

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46°30' and 47°30′S. The right lateral transtensional Marques–Zeballos Pass fault system (MZPRS) controlled the 800–1200 m uplift of the Andes at 16.1–18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10–15° westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148–178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif. The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge −1 segment (SCR −1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47°S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E –W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N–S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological "twin" of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in–depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3–4 Myr. [ABSTRACT FROM AUTHOR]

The geodynamic system of Earth is controlled by the horizontal motion of fragmented tectonic plates due to complex interaction between the mantle and the crust. Land and marine paleomagnetic signatures, along with extensive petrochronological and structural data, suggest non-continuous, multi-directional convergence histories for modern orogenic belts, as seen in the Himalayas and Betic Cordillera, among others. The consequences of radical changes in the direction of plate motions are obscured by complex structural settings and repeated cycles of metamorphism in orogenic belts. Although, subduction was operational on Earth in the Paleoproterozic, one of the major questions is: how far back in geological time can we trace the scale of modern-style subduction, collisional tectonics and poly-metamorphism? The metasedimentary and volcanic rocks (2.5 to 2.05 Ga) of the Sodankylä belt of northern Finland were deformed and metamorphosed during a prolonged period, now represented by the Svecofennian orogen (ca. 1.92–1.77 Ga). The orogenic belt represents a window into the deep levels of a Paleoproterozoic crust, where the interplay between deformation and metamorphism can be compared with the modern orogenic settings. In this study, five discrete heterogeneously developed superimposed, near-orthogonal, deformation events (D1 to D5) have been identified and mapped based on the high-resolution aeromagnetic data and field studies. Regional correlation of tectonic fabrics, along with metamorphic textures across the Sodankylä belt and northern Finland, suggest that each deformation event was a regional-scale phenomenon rather than a local one. Previous geochronological data obtained from the Sodankylä belt and adjacent Central Lapland Granitoid Complex on different Paleoproterozoic deformed rocks allow us to propose a time-constrained tectono-metamorphic model for the Sodankylä belt. The sequence of near-orthogonal deformation history and the polymetamorphic evolution offer comparisons with modern-style orogenic settings. The most notable aspect is the occurrence of Mesoarchean and Paleoproterozoic eclogitic high-pressure granulites reported from the Belomorian belt of Fennoscandian Shield, which lies to the east of the Sodankylä belt. From a tectono-metallogenic viewpoint, the Sodankylä belt is located in the centre of Ni-Cu-PGE, orogenic gold-cobalt deposits of the northern part of Fennoscandian Shield, therefore, the tectonic processes and overprinting role of multiple deformation phases need to be well understood as they directly link mineral exploration to the timing and controls on mineralization. [ABSTRACT FROM AUTHOR]

• Creation of 3D velocity-corrected discontinuity model for the Cascadia margin. • Forearc crustal thickness and seismic structure highlights zones of subcretion. • Slab morphology, fluid release, and subcretion contribute to significant margin variations. • Subcretion is the primary control on Cascadia forearc differential topography. A number of seismic and other geophysical phenomena exhibit significant lateral heterogeneity along the strike of the Cascadia forearc. Both the overriding and downgoing plate have been invoked to play the dominant role in controlling along-strike correlations between seismogenic behavior, potential field measurements, morphological/tectonic characteristics, and seismic structure; however, significant feedbacks likely exist between the two. In this study, we apply a 3D velocity correction to receiver function data and interpret the resulting discontinuity model alongside a recently published shear-wave velocity model to understand the possible causative relationships between correlative along-strike variations. Our discontinuity model indicates that the forearc crust thickens as it approaches the mantle wedge corner before progressively thinning toward the magmatic arc, likely due to the basal accretion of material from the downgoing plate to the overriding plate. In the northern and southern portions of the forearc, this "subcreted" material is characterized by thick (∼10 km) anomalously low shear-wave velocity zones. The thickness, high internal reflectivity, and low Bouguer gravity signatures associated with the low velocity zones likely indicate that this subcreted material is composed of dominantly (meta)sedimentary material that has been emplaced through successive subcretion events over geologic timescales. Furthermore, the anomalously low velocities and spatial correlation with high non-volcanic tremor (NVT) density and short slow slip recurrence intervals indicate that these regions are fluid-rich. While first-order variations in the fluids that control NVT and slow slip likely result from differences in the permeability of the downgoing slab as inferred from its stress state and the distribution of intraslab seismicity, these subcreted packages likely represent thick, vertically-impermeable regions in the lower crust that further accentuate this correlation. Variability in the amount of subcretion explains patterns of exhumation and uplift along the Cascadia margin and the resulting forearc topography over geologic timescales, and is likely controlled by some combination plate interface geometry/rheology and overriding plate architecture. [ABSTRACT FROM AUTHOR]