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The Eastern Pontides orogenic belt (EPOB) represents a significant segment of the Alpine-Himalayan orogenic belt that evolved from the Paleozoic to Cenozoic periods. Here we report new zircon U-Pb ages, together with Lu-Hf isotopes, and whole-rock geochemical and Sr-Nd isotopic analyses of plutonic rocks from EPOB, northeastern Turkey. Our aim is to interpret magmatic evolution in which the granitoids formed. Zircon U-Pb dating of six samples yielded crystallization ages of ∼134, ∼82, ∼39 Ma, respectively. They show a wide range of 87Sr/86Sr(i) (0.703 9–0.710 9), and εNd(t) values varying from −9 to +4.6, yielding model ages (TDM) from 520 to 1 623 Ma, suggesting a heterogeneous magma source. Dated zircons show exlusively positive εHf(t) values (+12.4 to +1.4), yielding model ages (TDM) from 352 to 1 059 Ma, implying that they are most likely derived from a juvenile lower crust rather than the mature continental crust. In this study, we suggested that the northward subduction of the Neo-Tethyan oceanic slab began from the Early Cretaceous and resulted in the Late Cretaceous magmatism. Moreover, the Middle Eocene magmatism in the EPOB was related to the collision of the Anatolide Taurid Platform (ATP) with the Pontides. [ABSTRACT FROM AUTHOR]

Published U-Pb-Hf values for detrital zircons of Mesoproterozic age in Cambrian and Ordovician strata of the Argentina Precordillera and San Rafael Block of the Cuyania Terrane overlap extensively with values from Grenville/Appalachian detritus and the Granite-Rhyolite Province of Laurentia and with values from Sierra de Maz and Sierra de Pie de Palo of the Western Sierras Pampeanas (WSP) of western Argentina. These data have been interpreted as evidence of the Laurentian origin of Cuyania and the WSP. However, U-Pb and corresponding εHf values presented here for Mesoproterozoic zircons from Ediacaran sandstones deposited on the Río de la Plata Craton (RPC) are markedly similar to those of Mesoproterozoic zircons from Laurentia, Cuyania, and the WSP, thus contradicting the previous interpretation. Given the geotectonic history of southwestern Gondwana, the U-Pb-Hf values from the Mesoproterozoic zircons of the Piedras de Afilar and Cerro Largo Formations of the RPC are consistent with a proto-Andean Mesoproterozoic belt on the western margin of the RPC. This belt would have served as the basement and thus the provenance of Mesoproterozoic detrital zircons in Cuyania and the WSP. The existence of this Mesoproterozoic belt introduces a different paradigm for interpreting the late Neoproterozoic to early Paleozoic geotectonic history of the proto-Andean margin of Gondwana and renders Neoproterozoic–early Paleozoic transfers of a Sierra de Maz–Arequipa–Rio Apa Terrane and the Cuyania Terrane from Laurentia unnecessary. [ABSTRACT FROM AUTHOR]

The crustal evolution of the Yangtze block and its tectonic affinity to other continents of Rodinia and subsequent Gondwana have not been well constrained. Here, we present new U-Pb ages and Hf isotopes of detrital zircons from the late Neoproterozoic to early Paleozoic sedimentary rocks in the northwestern margin of the Yangtze block to provide critical constraints on their provenance and tectonic settings. The detrital zircons of two late Neoproterozoic samples have a small range of ages (0.87-0.67 Ga) with a dominant age peak at 0.73 Ga, which were likely derived from the Hannan-Micangshan arc in the northwestern margin of the Yangtze block. In addition, the cumulative distribution curves from the difference between the depositional age and the crystalline age (CA-DA) together with the mostly positive εHf(t) values of these zircon crystals (-6.8 to +10.7, ~90% zircon grains with εHf[t] > 0) suggest these samples were deposited in a convergent setting during the late Neoproterozoic. In contrast, the Cambrian--Silurian sediments share a similar detrital zircon age spectrum that is dominated by Grenvillian ages (1.11-0.72 Ga), with minor late Paleoproterozoic (ca. 2.31-1.71 Ga), Mesoarchean to Neoarchean (3.16-2.69 Ga), and latest Archean to early Paleoproterozoic (2.57-2.38 Ga) populations, suggesting a significant change in the sedimentary provenance and tectonic setting from a convergent setting after the breakup of Rodinia to an extensional setting during the assembly of Gondwana. However, the presence of abundant Grenvillian and Neoarchean ages, along with their moderately to highly rounded shapes, indicates a possible sedimentary provenance from exotic continental terrane(s). Considering the potential source areas around the Yangtze block when it was a part of Rodinia or Gondwana, we suggest that the source of these early Paleozoic sediments had typical Gondwana affinities, such as the Himalaya, north India, and Tarim, which is also supported by their stratigraphic similarity, newly published paleomagnetic data, and tectono-thermal events in the northern fragments of Gondwana. This implies that after prolonged subduction in the Neoproterozoic, the northwestern margin of the Yangtze block began to be incorporated into the assembly of Gondwana and then accept sediments from the northern margin of Gondwanaland in a passive continental margin setting. [ABSTRACT FROM AUTHOR]

This article presents U–Th–Pb and Lu–Hf detrital zircon isotope data, as well as whole-rock Sm–Nd isotope data on metasedimentary rocks from the eastern part of the Tukuringra Terrane. Our analyses show that the zircons in metasedimentary rocks are mostly early Mesozoic. The Early Mesozoic, Early Paleozoic and Neoproterozoic zircons are predominant and Early Precambrian zircons are almost absent in these rocks. The age of the youngest zircon population places a lower age limit of sedimentation at 204 Ma for the Tungala Formation (Upper Triassic, Rhaetian), at 181 Ma for the Dugda Formation (Lower Jurassic, Toarcian), and at 189 Ma for the Tangomen Formation (Lower Jurassic, Pliensbachian). Practically all Mesozoic, Paleozoic, and Neoproterozoic zircons are characterized by Neo- and Mesoproterozoic Hf-model ages (tHf(DM)) = 1.41–0.46 Ga, tHf(C) = 1.55–0.49) and Mesoproterozoic Nd-model ages (tNd(DM) = 1.25–1.10 Ga, tNd(C) = 1.31–1.14). These results indicate that the sedimentary rocks were mainly sourced from the Amur continental superterrane, but not from the southern framing of the North Asian Craton. [ABSTRACT FROM AUTHOR]

Abstract: To constrain the paleoposition of the Tengchong block within Gondwana during the Early Paleozoic, we performed in-situ U–Pb and Hf isotope analyses on detrital zircons from Carboniferous strata in the Tengchong block. The age distributions yield dominant Neoarchean (~2.5Ga), Mesoproterozoic (1.7–1.4Ga), Grenvillian (~0.95Ga), and Pan-African (0.65–0.5Ga) age groups. Hf isotope compositions of Mesoproterozoic, Grenvillian, and Pan-African zircon age groups exhibit wide range of ε Hf(t) suggesting their diverse sources. The oldest Hf model ages indicate that the source magma included reworked Eoarchean (3.8–3.7Ga) crustal materials. The remarkable resemblance of zircon age spectra and Hf isotopes from the Tengchong block with those from Tethyan Himalayan, western Qiangtang and Indochina suggests that the Tengchong block was located along the Indian margin of Gondwana during the Early Paleozoic. In Grenvillian and Pan-African, crustal growth for the source areas was insignificant. [Copyright &y& Elsevier]

Garnet peridotite, garnet pyroxenite, mafic granulite and dominant felsic granulite constitute a high-pressure/high-temperature (HP/HT) metamorphic terrane in the south Altyn Tagh, North Tibet (China). Garnet peridotite and associated garnet pyroxenite occur as slices or lenses within high pressure felsic granulite. Previous studies indicate that garnet peridotite experienced the peak HP/HT metamorphism, followed by a medium pressure granulite-facies overprint. However, the origin of the garnet peridotite and associated garnet pyroxenite remains controversial. In this contribution, we present new zircon U–Pb and Hf isotopic data and whole-rock major, trace element and Sr–Nd isotopic data for the representative garnet peridotites and associated garnet pyroxenites. SHRIMP U–Pb dating on the inherited (magmatic) zircons from the garnet peridotites gave an U–Pb age of ca. 780 Ma, which is interpreted as the age of the ultramafic magma crystallization. The metamorphic zircons yield an age of ca. 500 Ma, which is consistent with the Sm–Nd isochron age of 493 ± 24 Ma for whole rock, garnet and clinoproxene from a garnet pyroxenite, representing the timing of peak metamorphism. The Baishiwake garnet peridotites and garnet pyroxenites show relatively high contents in Fe 2 O 3 , TiO 2 , P 2 O 5 , Nb, Zr, and Y, but significantly low MgO, Cr, A1 2 O 3 and Ni contents. They possess enriched LREE, nearly flat HREE, slightly positive Eu anomaly and weak negative anomalies in Nb and Ti. The relatively high 87 Sr/ 86 Sr ratios (0.707–0.710) and low 143 Nd/ 144 Nd ratios (0.5123–0.5124) imply a possible crust contamination prior to HP metamorphism. Integrating these data together with previous studies, we suggest that the Bashiwake garnet peridotites and associated garnet pyroxenites were derived from mantle-derived magmas which intruded into the continental crust during the Neoproterozoic and then experienced a common HP/HT metamorphism with felsic crustal rocks in the Early Paleozoic (ca. 500 Ma). [ABSTRACT FROM AUTHOR]

Abstract: To constrain the paleoposition of Indochina within Gondwana during the Early Paleozoic, we performed in-situ U–Pb and Hf isotope analyses on detrital zircons from three river sediment samples in the Truong Son Belt of the Indochina block. The age distributions yield dominant Neoarchean (~2.5Ga), Mesoproterozoic (1.7–1.4Ga), Grenvillian (~0.95Ga), and Pan-African (0.65–0.5Ga) age groups and minor Paleo- to Meso-archean zircons. Hf isotope compositions of zircons for each age group exhibit large ranges of εHf(T), suggesting that the zircon host rocks have diverse sources. The oldest Hf model ages for zircons of Neoarchean, Grenvillian, and Pan-African age group yield ~3.7Ga or older, while those of Mesoproterozoic age group show ~3.3Ga. The remarkable similarity of age distribution and Hf isotope compositions among detrital zircons of Indochina and those of Tethyan Himalaya, western Cathaysia, and Qiangtang suggests that Indochina was located outboard of Qiangtang and south of South China in the Indian margin of Gondwana during the Early Paleozoic. Our results are consistent with the paleontological correlations of east Gondwana margin during the Early Paleozoic. [Copyright &y& Elsevier]

Abstract This study presents new zircon U-Pb geochronological, whole-rock geochemical, and zircon Hf isotopic data along with regional geological observations for five late Paleozoic granitic plutons within the Xing'an Block of northeastern China. These data provide insights into the petrogenesis of these granitoids and the late Paleozoic tectonic evolution of the region. The geochronological and geochemical data indicate that the intrusions were emplaced during two separate periods, with the resulting granites having distinct geochemical features. The early Late Carboniferous (321–310 Ma) granitic Lizishan (LZS), Xiaonangou (XNG), and Dabeigou (DBG) plutons have high Sr/Y values (33.15–126.73), with low concentrations of Y and heavy rare earth elements (HREE), indicating adakitic affinities. However, the XNG granodiorites contain higher concentrations of MgO, Cr, and Ni, and have higher Mg# values (57–59) than the other plutons. The latest Carboniferous–Early Permian (301–296 Ma) granitic Weilegesi (WLGS) and Wuyi (WY) plutons are high-K calc-alkaline, with low Sr/Y ratios (0.18–24.15), and show petrological and geochemical characteristics of I-type granites. In addition, the magmatic zircon crystals within these plutons yield positive ε Hf (t) values (+4.1 to +12.9) and juvenile two-stage model (T DM2) ages (1056–499 Ma). The timing of emplacement and geochemical and isotopic compositions of the LZS and DBG granitoids are indicative of derivation from magmas generated by the partial melting of thickened lower crustal material, whereas the XNG granitoids were most likely formed from magmas generated by the partial melting of delaminated lower crustal material that subsequently interacted with mantle material during ascent. The latest Carboniferous–Early Permian low-Sr/Y granitoids may have formed from magmas generated by the partial melting of a dominantly juvenile amphibolite-facies crustal source under relatively low-pressure conditions, with these magmas subsequently undergoing variable degrees of fractional crystallization. Combining these new data with the results of previous research indicates that the terminal collision between the Xing'an and Songliao blocks occurred between the late Early and early Late Carboniferous, and the voluminous Late Carboniferous to Early Permian granitoids in the Xing'an Block are most likely related to post-collisional delamination. Graphical abstract Unlabelled Image Highlights • Late Paleozoic high- and low-Sr/Y granitoids are identified in the Xing'an Block. • The collision between the Xing'an and Songliao blocks occurred during ~330–310 Ma. • Late Carboniferous–Early Permian magmatisms formed by post-collisional delamination. [ABSTRACT FROM AUTHOR]

Abstract: The leucogranites in the Baoshan Block of the Tethyan belt in Western Yunnan, are composed mainly of two-mica granite with subordinate muscovite granite. Here we present zircon U–Pb ages from four intrusions that show ages of 448–476Ma suggesting that these rocks were emplaced during the Ordovician. The leucogranites are high-K calc-alkaline and strongly peraluminous, with K2O/Na2O>1 and A/CNK=1.12–1.54. These rocks are enriched in large-ion lithophile elements (LILEs) and light rare-earth elements (LREEs) [(La/Yb)N =1.13–32.4] and Pb, and are depleted in high field-strength elements (HFSEs). They show similar chondrite-normalized REE patterns, with negative Eu anomalies (Eu/Eu*=0.03–0.46). A wide range of zircon εHf(t) values (−9.6 to −2.6) and varying Hf-isotope crustal model ages (2.1–1.6Ga) are also observed. The geochemical signatures indicate that the leucogranites are S-type granites derived mainly from the anatexis of ancient crustal materials. The ages, geochemistry and tectonics in the Baoshan Block and the Lhasa Terrane are closely comparable, suggesting that the Baoshan Block might represent part of an Early Paleozoic magmatic arc in the Gondwana continental margin facing the proto-Tethyan Ocean. The Pinghe granites of the early phase in the Baoshan Block which are coeval with the Cambrian magmatism (ca. 492Ma) identified in the central and southern Lhasa subterranes can be interpreted as products of the slab break-off associated with the subduction of proto-Tethyan oceanic lithosphere. However, the late leucogranite stocks are analogous to the North Himalayan leucogranites, which formed in a short-lived extensional setting caused by the slab break-off associated with the subduction–collision system. [Copyright &y& Elsevier]

Abstract: Detrital zircon grains from Lower Paleozoic sedimentary rocks in the Yucatan Peninsula have an age distribution characterized by major probability peaks at ~1.0, ~1.2, and ~1.5Ga (Martens et al., 2010). Here, we present new Lu–Hf data (MC–ICPMS) paired with U–Pb ages (ID-TIMS) for additional zircon grains from the same rocks. This analytical approach yields precise information about the time and geochemical environment of zircon growth, which in turn helps to distinguish between different crustal source regions that just happen to host zircon populations of similar age. In addition, single zircon grains from granitoids that intruded the sedimentary rocks were dated by U–Pb laser ablation MC–ICPMS and ID-TIMS, and their Hf-isotope compositions were determined by solution MC–ICPMS. The zircon data are complemented by Sm–Nd analyses of the sedimentary and igneous whole rocks. The Yucatan Peninsula, which forms part of the Maya block of Central America, includes lower Paleozoic rocks in the Maya Mountains of Belize. The pre-Mesozoic geologic history of the Maya block is related to the evolution of the mid-Proterozoic basement in Mexico (Oaxaquia), other Paleozoic peri-Gondwanan terranes, and the Pan-African–Brasiliano type basement of Florida. The initial 176Hf/177Hf values of ~1.0Ga detrital zircon grains lie on a crustal evolution trajectory similar to that defined by older, ~1.2 to ~1.5Ga grains. This trajectory is consistent with those that would be produced by crustal reservoirs that separated from the depleted mantle between 1.70 and 2.05Ga. However, some grains have significantly less radiogenic 176Hf/177Hf(t), indicating influence from even older cratonic crust. Zircon grains from granitoids that intruded the Early Paleozoic sedimentary rocks of the Yucatan Peninsula yielded Late Silurian to Early Devonian (~415–400Ma) crystallization ages. More radiogenic Hf isotope ratios indicate anatexis of a crustal reservoir that is distinct from that of the Early Paleozoic sedimentary rocks. The Sm–Nd systematics of whole rock samples further support the results from the Hf isotopes in zircon grains. The data suggest a more continental provenance for the sedimentary rocks from Yucatan as compared to typical ca. 1.3 to 1.0Ga outcrops in southern and central Mexico. The results indicate that sediments were shed either from mid-Proterozoic complexes of NW Amazonia or from similar continental sequences that were thrust over Oaxaquia during the Grenville orogeny and subsequently eroded in the early Paleozoic. Integrating the data into a new model for early Paleozoic times, the southern Maya block is inferred to have formed during the opening of the Rheic Ocean along the western margin of Amazonia adjacent to Oaxaquia. The paucity of Ediacaran (Pan African–Brasiliano) signatures implies that before the Silurian, the southern Maya block evolved geographically separated from NW Yucatan and Florida, where Pan African–Brasiliano crystalline rocks have been reported. [Copyright &y& Elsevier]

This work presents the whole-rock elemental geochemistry and Sr − Nd isotopes and zircon Hf − O isotopes for dikes from Tagaolemiao and Tuilamamiao, the southern margin of the southeast Central Asian Orogenic Belt (SE CAOB), to explore their origin and dynamic setting. Zircon U − Pb dating reveals that the Tagaolemiao dikes emplaced at ca. 242 Ma and the Tuilamamiao dikes emplaced at ca. 250 Ma, which postdated the Late Permian magmatic lull and convergent events in the SE CAOB. Dikes from the two areas are I-type rhyolitic rocks and exhibit high SiO 2 , low MgO, and low Cr, Co, and Ni contents. The Tagaolemiao dikes have depleted zircon Hf (ε Hf (t) = +3.75 to +9.82), whole-rock Sr − Nd (I Sr (t) = 0.704340–0.704855; ε Nd (t) = +1.3 to +2.1) isotopic composition and variable zircon δ18O values (4.88–7.29‰), and were derived from the mixing melts of the juvenile crust and depleted mantle. In contrast, the dikes from Tuilamamiao show negative zircon ε Hf (t) (−2.33 to −10.85) and whole-rock ε Nd (t) (−6.7 to −15.5) values, low I Sr (t) (0.706640–0.708208) and high δ18O (6.38–7.61‰) values, which originated from the partial melting of the old continental lower crust. The Triassic dyke swarms from this work indicate the SE CAOB switched into an intra-continental extension tectonic setting after the Paleozoic long-term accretion-convergence. • Early-Middle dikes were derived from the thickened lower crust. • Triassic dyke swarms reveal an intra-continental extension setting. • Vigorous mantle perturbation is important to the Triassic tectonics in the SE CAOB. [ABSTRACT FROM AUTHOR]

Hf-isotope data of >1100 detrital zircon grains from the Palaeozoic, south-central Andean Gondwana margin record the complete crustal evolution of South America, which was the predominant source. The oldest grains, with crustal residence ages of 3.8-4.0 Ga, are consistent with complete recycling of existing continental crust around 4 Ga. We confirm three major Archaean, Palaeoproterozoic (Transamazonian) and late Mesoproterozoic to early Neoproterozoic crust-addition phases as well as six igneous phases during Proterozoic to Palaeozoic time involving mixing of juvenile and crustally reworked material. A late Mesoproterozoic to early Neoproterozoic, Grenville-age igneous belt can be postulated along the palaeo-margin of South America. This belt was the basement for later magmatic arcs and accreted allochthonous microcontinents as recorded by similar crustal residence ages. Crustal reworking likely dominated over juvenile addition during the Palaeozoic era, and Proterozoic and Archaean zircon was mainly crustally reworked from the eroding, thickened Ordovician Famatinian arc. [ABSTRACT FROM AUTHOR]

It is broadly accepted by researchers that the North China Craton (NCC) was linked with the Pangea supercontinent by the Central Asian Orogenic Belt (CAOB) resulted from the final closure of the Paleo Asian Ocean (PAO), but when and how still be controversial, such as one-sided subduction and continental collision, or double-sided subduction and soft collision, the ocean basin closed in the Devonian or Late Permian and so on. We conducted zircon U-Pb-Hf isotopes analyses of 5 Paleozoic sedimentary samples which collected along the Bainaimiao area, locates at the northern margin of the NCC, and compared their zircon U-Pb isotopic ages and εHf(t) values with those former published data in the north orogenic belt (NOB) and the south orogenic belt (SOB) to trace provenance differences between the NOB and SOB. Our sedimentary samples have several prominent age peaks at circa 270 Ma, 460 Ma, 1350 Ma, 1750 Ma and 2500 Ma, respectively, and cover different εHf(t) values in different age peaks, which have shown complex tectonic evolution of the NCC and the Bainaimiao arc belt. In our comparison, the Neo-Proterozoic zircons are common seen in the NOB data, but rare in the SOB data, and Devonian zircons from the NOB have mostly shown positive εHf(t) values while most of which from the SOB are negative, which mean that the NOB magmatism events in Paleozoic period had formed juvenile crust but the SOB magmatism events in temporary period result from reworking of older crust according to detrital zircon ages and relevant εHf(t) values. In addition, trace elements analysis of the detrital zircons, such as U, Hf, Y, Th, Yb and so on, was also used to help distinguishing the tectonic setting of the formation of these zircons. Our data shows that most Paleozoic zircons have lower Y concentration and higher U/Yb (>0.1) ratios, which can be inferred that these zircons may crystalized in continental magmatic setting, which supports the viewpoint that the oceanic crust of the PAO subducted beneath the NCC in the Paleozoic to form and transform the Bainaimiao arc belt. In summary, we use detrital zircons geochronology and trace elements analyses to outline Paleozoic magmatic events occurred in the northern margin of the NCC, to discuss the attribute of the Bainaimiao arc belt, and imply that there was no material exchange between the NOB and the SOB in the Paleozoic, namely, the PAO oceanic basin still remained open until the Permian, and the eastern segment of the CAOB may finally formed after the Paleozoic. [ABSTRACT FROM AUTHOR]

Considerable controversy concerns the consumption and closure processes of the North and South Altyn Oceans resulting in the formation of the North Altyn Tagh subduction-accretion belt and the South Altyn Tagh subduction-collision belt in the Altyn Tagh orogen in southeastern Tarim. This study focused on U–Pb ages and Hf isotopes of detrital zircons from early Paleozoic sedimentary rocks in the Central Altyn Tagh terrane. Our dating results revealed that the studied sedimentary rocks were deposited at ca. 467–429 Ma. The predominant early Paleozoic detrital zircons demonstrate negative εHf(t) values, highlighting their derivation from the coeval intermediate-felsic magmatic rocks sourced from ancient supracrustal materials with enriched isotopes. These inferred, enriched intermediate-felsic magmatic rocks were probably generated in different consumption and closure processes of the North and South Altyn Oceans, based on geochronology and geochemistry of the early-middle Paleozoic intermediate-felsic magmatic rocks in the Altyn Tagh orogen. A number of ca. 520–490 Ma detrital zircons were primarily derived from the coeval, enriched intermediate-felsic magmatic rocks in the local Central Altyn Tagh terrane and the adjacent North Altyn Tagh subduction-accretion belt associated with the advancing subduction of the North Altyn Ocean. The ca. 490–470 Ma detrital zircons are most prominent and suggest a derivation from the coeval, enriched magmatic rocks subject to the rollback of the North Altyn Ocean. These inferred magmatic rocks might have once existed in the region but have been intensely exhumed to be source material for the studied sedimentary rocks. A few ca. 450 Ma detrital zircons indicate a provenance from the North Altyn Tagh subduction-accretion belt during collision after the final closure of the North Altyn Ocean. In contrast, some ca. 470–460 Ma detrital zircons were probably derived from the coeval intermediate- to felsic-magmatic rocks in the Central Altyn Tagh terrane during the exhumation stage of the deep continental collision after the final closure of the South Altyn Ocean. Combination of provenance study and magmatic record provides potential to establish complicated orogenic evolution. [ABSTRACT FROM AUTHOR]

Coupled U–Pb and Lu–Hf LA-ICP-MS detrital and igneous zircon data were obtained from metasedimentary sequences (Kaserer Formation, Schmirntal Quartzite, Seidlwinkel Formation, Bündnerschiefer Basin, Riffler Basin) of the western Tauern Window (Eastern Alps). Results show maximum deposition ages between the Late Permian and the Triassic, indicating protracted sedimentation and magmatism between the Late Paleozoic and the Mesozoic. The Lu–Hf fingerprint shows a change from subchondritic to variable subchondritic to suprachondritic compositions at ca. 290 Ma, possibly documenting the transition from Late Paleozoic Variscan post-collisional processes to intracontinental extension. Lithospheric thinning and magmatic underplating may explain the observed Hf isotopic evolution as the result of mixing of crustal and mantellic sources. From a paleogeographical perspective, results confirm that the Tauern Window was situated between Alpine basement units (South Alpine, Austroalpine and External Massifs) and the Bohemian Massif during the Permian–Triassic. [ABSTRACT FROM AUTHOR]

The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic. [ABSTRACT FROM AUTHOR]

The formation and evolution of the ancient continental crust are crucial issues in solid-earth geology which are commonly associated with global tectonic events and the formation of economically valuable magmatic-hydrothermal ore deposits. The Cathaysia Block, one of the ancient continents in Southeast Asia, can be subdivided into two parts: the West Cathaysia Block and the East Cathaysia Block. Unlike the East Cathaysia Block, no Precambrian rocks are exposed in the West Cathaysia Block, constraining further understanding of the formation and evolution of this block. In this study, a total of four hundred and thirty-three zircon U-Pb dating analyses and two hundred and eighteen Lu-Hf isotopic analyses on zircon grains from the Jurassic Dengfuxian granites and Ordovician Tanghu granites, Nanling Range, were carried out. LA-ICP-MS zircon U-Pb dating yields mean average 206Pb/238U ages of 152.6 ± 2.2 Ma (MSWD = 1.6) and 442.4 ± 1.7 Ma (MSWD = 3.8), which are regarded as the rock-forming age for the Jurassic Dengfuxian granites and Ordovician Tanghu granites, respectively. The 207Pb/206Pb ages of the inherited zircons from the Jurassic Dengfuxian granites and Ordovician Tanghu granites range from 522 Ma to 3395 Ma, hosting two major peaks at the 0.9–1.0 Ga and 2.4–2.5 Ga. In contrast to the East Cathaysia Block, the West Cathaysia Block lacks the age peak of 1.8–1.9 Ga, indicating that the West Cathaysia Block was not influenced by the assembly of the Columbia supercontinent in the Paleo-Proterozoic. In combination with the Lu-Hf isotopes, we proposed that the crust evolution of the West Cathaysia Block in Archean is dominated by juvenile crustal growth events, and dominated by the crustal reworking since the Proterozoic. The long duration of crustal reworking in the West Cathaysia Block resulted in the enrichment of lithophile elements (e.g., W, Sn, Nb, and Ta) in the crust of that region. Therefore, the Jurassic granites in the Nanling Range, which are mainly derived from the partial melting of Proterozoic basement rocks, became associated with large-scale tungsten polymetallic mineralization. [ABSTRACT FROM AUTHOR]

The Polish Lowlands, located southwest of the Teisseyre-Tornquist Zone, within Trans-European Suture Zone, were affected by bimodal, but dominantly rhyolitic, magmatism during the Late Paleozoic. Thanks to the inherited zircon they contain, these rhyolitic rocks provide a direct source of information about the pre-Permian rocks underlying the Polish Lowland. This paper presents zircon U-Pb geochronology and Hf and O isotopic results from five drill core samples representing four rhyolites and one granite. Based on the ratio of inherited vs. autocrystic zircon, the rhyolites can be divided into two groups: northern rhyolites, where autocrystic zircon is more abundant and southern rhyolites, where inherited zircon dominates. We suggest that the magma sources and the processes responsible for generating high silica magmas differ between the northern and southern rhyolites. Isotopically distinct sources were available during formation of northern rhyolites, as the Hf and O isotopes in magmatic zircon differ between the two analysed localities of northern rhyolites. A mixing between magmas formed from Baltica-derived mudstone-siltstone sediments and Avalonian basement or mantle can explain the diversity between the zircon compositions from the northern localities Daszewo and Wysoka Kamieńska. Conversely, the southern rhyolites from our two localities contain zircon with similar compositions, and these units can be further correlated with results from the North East German Basin, suggesting uniform source rocks over this larger region. Based on the ages of inherited zircon and the isotopic composition of magmatic ones, we suggest that the dominant source of the southern rhyolites is Variscan foreland sediments mixed with Baltica/Avalonia-derived sediments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porphyry Cu mineralizations are closely related to adakitic igneous rocks. • SHRIMP zircon dating yields a middle Carboniferous intrusion age. • Zogdor granodiorite and monzogranite were derived from a depleted mantle source. The Zogdor Cu occurrences are located in the Gurvansayhan island arc terrane of southern Mongolia, which corresponds to the southern part of the Central Asian Orogenic Belt (CAOB). The major porphyry type copper–gold (molybdenum) mineralized belt including Oyu Tolgoi, Tsagaan Suvarga, Shuteen, and Kharmagtai deposits are located in this terrane and were known to have formed during 372–324 Ma. The Zogdor Cu occurrences are found within this porphyry Cu-Au mineralized belt and are limitedly distributed in granitoids including granodiorite and monzogranite. In this study, we present new SHRIMP zircon U-Pb geochronology, LA-MC-ICPMS zircon Lu-Hf isotopes, and geochemical data for the granitoids in the Zogdor Cu occurrences and provide a new tectonic model including igneous activities and Cu mineralization in southern Mongolia. The emplacement ages of granodiorite and monzogranite are 329.1–326.4 Ma, and 329.9–326.1 Ma, respectively. All zircons have positive ε Hf values corresponding to two-stage model ages (T 2DM) ranging from 581 to 331 Ma, possibly demonstrating that late Neoproterozoic to middle Carboniferous juvenile continental crust growth was derived from a depleted mantle source. Both granitoids are characterized by high Al 2 O 3 and Sr, and low Y and Yb contents, as well as high Sr/Y and (La/Yb) N ratios, which are typical geochemical characteristics of adakites. The trace elements are characterized by an enrichment in the large ion lithophile elements (e.g., Cs, Rb, Ba, and Sr) and a depletion in the high field strength elements (e.g., Nb, P, and Ti), indicating that these granitoids intruded in subduction tectonic settings. In conclusion with data from previous studies, the intermittent igneous activities during the Cambrian to Ordovician (519–482 Ma), middle Devonian (374–363 Ma), middle to late Carboniferous (353–304 Ma), and early Permian (298–286 Ma) took place in the southern Mongolia and porphyry copper mineralizations seem to be closely related the middle Devonian and middle Carboniferous adakitic or adakite-like magmatism. The Lu-Hf isotopic results for these associated granitoids including previous Rb-Sr and Sm-Nd isotopic studies imply that the Neoproterozoic to middle Carboniferous juvenile continental growth derived from a depleted mantle source. The middle Devonian and middle Carboniferous magmatic activities triggered by the subduction of the Paleo-Asian Oceanic plate and formed the porphyry copper deposits in the southern Mongolia. [ABSTRACT FROM AUTHOR]

Earth's evolution involves deep, hot rocks rising upward by convection to near-surface environments, as well as the unique scenarios such as the formation and breakup of Gondwana and Pangea. These processes have been well recorded by the widely distributed magmatism. To understand the tectonic evolution and Gondwana assembly, we compiled early Paleozoic zircon U–Pb ages (n = 67), in-situ zircon Hf isotopes (n = 1011), and bulk-rock elemental compositions (n = 293) and Sr–Nd isotopes of magmatic rocks in the Tibetan–Himalayan orogen. Three stages of Paleozoic magmatism were identified here, including early (>490 Ma) to middle (490–470 Ma) to late (<470 Ma) stages, in response to the final assembly of the Gondwana supercontinent. Early-stage magmatic rocks are characterized by highly variable SiO 2 (48.0–80.0 wt%) and MgO (0.02–9.65 wt%) contents with Mg# range from 5.4 to 78, K 2 O/Na 2 O ratios ranging from 0.14 to 2.81, and whole-rock Sr–Nd (87Sr/86Sr(i) (0.7035–0.7340), ε Nd (t) (-9.5–+1.0)) and zircon Hf (ε Hf (t) = –15 to + 8.0) isotopic compositions with significant mantle contributions; they could be generated in an Andean-type arc setting along the active northern continental Gondwana margin. Middle-stage magmas were dominated by fertile continental crustal signatures (SiO 2 > 70 wt%, A/CNK > 1.10, MgO < 2.69 wt%) in a crustal thickening setting. Late-stage magmas also have highly variable Si, Mg and isotopic components, with coeval mantle-derived magmas developing in an extensive setting. Importantly, the widespread presence of early Cambrian to late Ordovician peraluminous high-K calc-alkaline magmatism in the Tibetan–Himalayan orogen indicates that the reworking of ancient continental crustal materials played a key role in reconstructing and stabilizing the final Gondwana assembly. [ABSTRACT FROM AUTHOR]

Plagiogranites are a volumetrically minor component of oceanic crust and ophiolites, but offer an opportunity to probe the processes and mechanisms by which felsic crusts were produced from the mafic oceanic crusts. The Qinling-Tongbai orogenic belt in central China is a typical composite orogenic belt that records the amalgamation processes between the North China Block and the South China Block. The Erlangping unit represents an accretionary oceanic unit in the Qinling-Tonbai orogenic belt and contains minor plagiogranites, which have received little attention. In this study, we carried out an integrated study of U–Pb geochronology and Hf–O isotopes in zircon, as well as whole-rock isotope and geochemical analyses for felsic rocks in the Erlangping unit. These rocks occur as dikes to stocks intruding ambient basalts. They have relatively high Na 2 O and Al 2 O 3 , moderate MgO and low K 2 O contents, and are classified as oceanic plagiogranites. Zircon U–Pb geochronology yielded formation ages of ca. 465 Ma. Zircon δ18O compositions (4.4–5.1‰) are lower than or similar to those of zircons from normal mantle. The low TiO 2 content, elevated Zr/Hf, and light rare-earth element (LREE) enrichments in these rocks indicate that these plagiogranites were generated by partial melting of hydrothermally altered oceanic crust. These samples have more depleted whole-rock ε Nd (t) (+4.4 to +5.1) and zircon ε Hf (t) (+10.5 to +12.8) values than the basaltic wall-rocks, implying they were derived from a newly accreted oceanic arc. Taking into account the tectonic framework of the broader Qinling Orogenic belt, a subduction-induced magma flare-up in the Ordovician could have triggered the anatexis of the existing Erlangping oceanic arc, and in turn generated these plagiogranites. Partial melting of oceanic crust that has been enriched in a subduction system may be an important mechanism for the formation and maturation of continental crust in oceanic arc settings. • Plagiogranite dikes and stokes in the Erlangping unit were emplaced at ca. 465 Ma. • The plagiogranites were formed by partial melting of lower oceanic crust. • Subduction induced the anatexis of the existing Erlangping oceanic arc. • Partial melting of ocean crust is important for the maturation of continental crust. [ABSTRACT FROM AUTHOR]

The Pan-African and Brasiliano orogenies endowed West Gondwanaland with U–Pb 700–500 Ma zircons, which, together with 1200–1000 Ma zircons from Rodinian collisions, are scattered in the Ediacaran–Paleozoic syn- and post-tectonic molassic outflow from the orogens. A more complete (T DM , εHf) isotopic signature in places narrows the search for provenance but exclusive use of the signature is of limited value given the ubiquity of primary and secondary 700–500 Ma and 1200–1000 Ma zircons. To overcome this shortcoming, I link the detrital-zircon signature with paleogeographical indicators of downslope preserved in minor sedimentary structures generated by gravity currents: the cross-dip azimuth in fluvial sediments, flute marks and other vectorial markings in turbidites. The prominent East African-Antarctic Orogen (EA-AO) trends through Africa-Arabia southward through East Africa/Madagascar to Dronning Maud Land in Antarctica. Squire et al. (Squire et al., 2006. Did the Transgondwanan Supermountain trigger the explosive radiation of animals on Earth? Earth and Planetary Science Letters 250, 116–133) postulated > 8000-km-long and > 1000-km-wide Transgondwanan Supermountains (TGSM) atop the EA-AO that resulted in extreme erosion and sedimentation rates; super-fans of quartz sand spread across continental North Africa-Arabia and oceanic crust offshore East Gondwanaland, as seawater 87 Sr/ 86 Sr rose to a maximum. Downslope indicators and the isotopic signature confirm the suggested deposition of the enormous North African-Arabian Super-fan from the Oubanguides Orogen-TGSM (Burke et al., 2003. Africa's petroleum systems: four tectonic ‘Aces’ in the past 600 million years. Geological Society of London Special Publications 207, 21–60), and the Cape Group from the TGSM. Other major provenance → sink relations are the Oubanguides Orogen → Congo Basin and the Damara Orogen and Dom Feliciano Orogens → Nama Basin. Minor and proximal provenance → sink relations are the Tuareg Shield and the Dahomeyides-Nigerian Shield → Volta Basin, and the Paraguay Orogen → Puncoviscana Basin. The voluminous primary sediment deposited during the Ediacaran, Cambrian, and Ordovician was recycled many times up to its present-day appearance in river and beach sand in Africa and in Australia . Compared with 60–0 Ma (~ Cenozoic) collisional Himalaya-Tibet and Mongolian Plateaus and related sediment fans of East Asia, the 700–500 Ma (Ediacaran–Cambrian) collisional continental super-fan in North Africa and Arabia and the deep-sea super-fan off East Gondwanaland are larger in extent and in their impact on seawater 87 Sr/ 86 Sr, probably because West Gondwanaland underwent crustal shortening over a much longer span; furthermore, the ancient morphotectonic regime lasted to the Carboniferous/Permian (~ 300 Ma) merger of Gondwanaland and Laurussia in Pangea, which instituted widespread Pangean-induced subsidence in broad basins that overlapped the planed-off orogens. [ABSTRACT FROM AUTHOR]

Voluminous rhyolitic lavas and ignimbrites (c. 34 000 km3) were formed in the NE German Basin in a post-collisional setting at c. 295 Ma. Trace elements, &varepsilon;Hf and δ18O have been measured in dated magmatic and inherited rhyolitic zircons from three drill cores across the basin. Magmatic zircons crystallized in two stages: the first stage in less differentiated and isotopically heterogeneous magmas and the second stage in more differentiated and isotopically homogeneous magmas. The first and second stages can be related to the crystallization of zircons within a heterogeneous pluton and in an evolved, silicic magma that was later erupted. Some zircons crystallized entirely during the evolved magma stage and provide good resolution for identifying and characterizing processes happening shortly before eruption. The isotopic compositions of the magmatic zircons constrain the proportions of juvenile and reworked materials involved in the formation of voluminous silicic magmas in a post-collisional tectonic setting. The advantage of studying the volcanic rocks from the NE German Basin is that their petrogenesis involved a relatively simple, two-source interaction during magma production, which permits quantitative estimation of the amount of each source component. AFC modelling shows that the first stage zircons crystallized from magmas containing 5–80% of the juvenile component, whereas the final rhyolitic magmas contained 30–40% of this material. The inherited zircons have Hf model ages of 1·9–2·2 Ga, suggesting that much of the local basement was initially derived from the mantle at that time and that it was subsequently reworked at around 1·5 Ga. Similar model ages are a feature of Baltica-derived sediments and the implication is that such sediments underlie large areas of the NE German Basin. The lack of any record of Avalonian basement in the NE German Basin may indicate that both the sedimentary cover and the underlying basement are part of Baltica. [ABSTRACT FROM AUTHOR]

Late Paleozoic (Variscan) magmatism is widespread in Central Europe. The Lusatian Block is located in the NE Bohemian Massif and it is part of the Saxothuringian Zone of the Variscan orogen. It is bordered by two major NW-trending shear zones, the Intra-Sudetic Fault Zone towards NE and the Elbe Fault Zone towards SW. The scarce Variscan igneous rocks of the Lusatian Block are situated close to these faults. We investigated 19 samples from Variscan plutonic and volcanic rocks of the Lusatian Block, considering all petrological varieties (biotite-bearing granites from the Koenigshain and Stolpen plutons, amphibole-bearing granites from three boreholes, several volcanic dykes, and two volcanites from the intramontane Weissig basin). We applied whole-rock geochemistry (18 samples) and zircon evaporation dating (19 samples). From the evaporation data, we selected six representative samples for additional zircon SHRIMP and CA–ID–TIMS dating. For the Koenigshain pluton, possible protoliths were identified using whole-rock Nd-isotopes, and zircon Hf- and O-isotopes. The new age data allow a subdivision of Variscan igneous rocks in the Lusatian Block into two distinct magmatic episodes. The spatial relation of the two age groups to either the Elbe Fault Zone (298–299 Ma) or the Intra-Sudetic Fault Zone (312–313 Ma) together with reports on the fault-bound character of the dated intrusions suggests an interpretation as two major post-collisional faulting episodes. This assumption of two distinct magmatic periods is confirmed by a compilation of recently published zircon U–Pb CA–ID–TIMS data on further Variscan igneous rocks from the Saxothuringian Zone. New geochemical data allow us to exclude a dominant sedimentary protolith for the Koenigshain pluton as supposed by previous investigations. This conclusion is mainly based on new O- and Hf-isotope data on zircon and the scarcity of inherited zircons. Instead, acid or intermediate igneous rocks are supposed as the main source for these I-type granitoids from the Koenigshain pluton. [ABSTRACT FROM AUTHOR]

Highlights • Detrital zircon ages and Hf isotopes, Nyainqentanglha Group, central Lhasa terrane. • The earliest coarse clastic rocks in central Lhasa terrane deposited at 803 ± 5 Ma (Tonian). • Some Mesoproterozoic zircons may come from the terranes that became the Himalayas. • Neoproterozoic zircons may be derived from convergent plate margin system along NW Rodinia. • Lhasa and Himalaya may have been adjacent before Gondwana's amalgamation. Abstract Cimmerian terranes in Tibet are thought to be as old as Archean or as young as Neoproterozoic or even early Paleozoic in age. However, their Precambrian history and their role in the assembly and dispersal of early supercontinents (e.g., Rodinia) are still poorly known. Here, U-Pb dating, trace-element geochemistry and Lu-Hf isotopes of detrital zircons (351 grains) from the Nyainqentanglha-Group clastic rocks, the earliest strata overlying the Lhasa Block (South Tibet), are used to constrain the provenance of the sediments and test paleogeographic and tectonic models for the Lhasa Block during the breakup of the Rodinia supercontinent. The youngest detrital zircon cluster (803 ± 5 Ma) in the clastic rocks and granitic dykes (797 ± 10 Ma) intruding them constrain the deposition age close to 800 Ma. Four main groups of detrital zircons in these sediments record several sources, including Mesoproterozoic and Neoproterozoic juvenile terranes, a Grenvillian orogenic belt and an Archean continental-crust component. Detrital-zircon age distributions and Lu-Hf isotopic data reveal the variation of the sedimentary provenance and suggest its affinity to the Himalaya and/or the East Africa Orogen. These results show that the Lhasa Block was probably located within a giant convergent plate margin system surrounding the Rodinia supercontinent during its breakup in the Tonian time. [ABSTRACT FROM AUTHOR]

The Tauride block in Turkey is a peri-Gondwana, Cadomian-type terrane that rifted from the Afro-Arabian margin of Gondwana in the Permo-Triassic and re-accreted to Arabia in the Neogene. In the Karacahisar dome in the southern-central Taurides, Neoproterozoic basement metasediments and intrusive rocks are overlain by Cambro-Ordovician, Carboniferous and Triassic sediments. We studied U–Pb–Hf in zircons from major rock units exposed in Karacahisar in order to constrain the Cadomian crustal evolution of the Taurides, to evaluate the provenance of the Neoproterozoic and overlying sediments, to constrain the paleogeography of the Taurides, and to assess their linkage to Gondwana. The Neoproterozoic metasediments are low-grade metamorphic wacke-type turbidites that evolved in a broad back-arc basin peripheral to Afro-Arabia. Their detrital zircon U–Pb signal comprises a preponderance (40–68%) of Neoproterozoic-aged zircons (peak ages defined at 635 and 830 Ma), indicating that the sedimentary pile was built mainly from the erosion of Pan-African terranes from Afro-Arabia. The εHf values of the younger population (635 Ma) are mostly positive, indicating derivation from a juvenile arc, whereas Cryogenian–Tonian detrital zircons spread vertically (− 25 < εHf < 15), indicating a different provenance where mixing of juvenile magmas with Paleoproterozoic to Neoarchean crust was widespread. An unusually high proportion of pre-Neoproterozoic zircons is found in all Cadomian metasediments, including up to 31% Grenvillian-aged (ca. 1.0 Ga) and up to 35% of ca. 2.5 Ga zircons; about a third of the latter possess positive εHf values. Because only minor exposures of 1.0 and 2.5 Ga crustal vestiges are currently known in North Africa and Arabia, we infer that pre-Neoproterozoic terranes were dispersed within the Cadomian realm itself. The youngest detrital zircons in all Cadomian metasediments concentrate at 0.58 Ga, indicating that the proto-Cadomian back-arc basin was formed towards the Late Ediacaran. The termination of Neoproterozoic sedimentation is marked by the intrusion of dyke swarms yielding a U–Pb zircon age of 544 ± 4 Ma, coeval with magmatism in other Cadomian basement units in the Taurides (e.g., Sandıklı and Menderes massif). Shortly afterwards the Tauride basement was overstepped by the Cambro-Ordovician platform. From the Cambrian to the Triassic, the U–Pb–Hf detrital zircon signal of the cover sediments in the Taurides in Karacahisar portrays remarkable resemblance to that of typical North Gondwana Cambro-Ordovician cover sediments, and shows that the Taurides accreted to Afro-Arabia by the onset of the Cambrian. The short time interval between Cadomian basin fill and deposition of the Cambrian platform implies that the Taurides evolved within a short distance from their present position relative to the Afro-Arabian margin of Gondwana. The Gondwana provenance of the Tauride sedimentary cover is maintained through the Upper Triassic, indicating that Neo-Tethys rifting was incipient at that time, allowing Afro-Arabian detritals to reach the Taurides. [ABSTRACT FROM AUTHOR]

The late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton. To clarify the framework, petrogenesis of early Permian intrusive rocks from southeastern Inner Mongolia was studied. Zircon U‐Pb dating for bojite and syenogranite from Ar‐Horqin indicate that they were emplaced at 288–285 Ma. Geochemical data reveal that the bojite is highly magnesian and low‐K to middle‐K calc‐alkaline, with E‐MORB‐type REE and IAB‐like trace element patterns. The syenogranite is a middle‐K calc‐alkaline fractionated A‐type granite and shows oceanic‐arc‐like trace element patterns, with depleted Sr‐Nd‐Hf isotopes, (87Sr/86Sr)I = 0.7032–0.7042, εNd(t) = +4.0 to +6.6 and zircon εHf(t) = +11.14 to +14.99. This suggests that the bojite was derived from lithospheric mantle metasomatized by subducted slab melt, while the syenogranite originated from very juvenile arc‐related lower crust. Usng data from coeval magmatic rocks from Linxi–Ar‐Horqin, the Ar‐Horqin intra‐oceanic arc was reconstructed, i.e., initial transition in 290–280 Ma and mature after 278 Ma. Combined with regional geological and geophysical materials in southeastern Inner Mongolia, an early Permian tectonic framework as 'one narrow ocean basin of the PAO', 'two continental marginal arcs on its northern and southern' and 'one intra‐oceanic arc in its southern' is proposed. [ABSTRACT FROM AUTHOR]

The Ellsworth-Whitmore Mountain terrane of central Antarctica was part of the early Paleozoic amalgamation of Gondwana, including a 13,000 m section of Cambrian- Permian sediments in the Ellsworth Mountains deposited on Grenville-age crust. The Jurassic breakup of Gondwana involved a regional, bimodal magmatic event during which the Ellsworth-Whitmore terrane was intruded by intraplate granites before translation of the terrane to its present location in central Antarctica. Five widely separated granitic plutons in the Ellsworth-Whitmore terrane were analyzed for their whole-rock geochemistry (X-ray fluorescence), Sr, Nd, and Pb isotopic compositions, and U-Pb zircon ages to investigate the origins of the terrane magmas and their relationships to mafic magmatism of the 183 Ma Karoo-Ferrar large igneous province (LIP). We report high-precision (±0.1 m.y.) isotope dilution- thermal ionization mass spectrometry (IDTIMS) U-Pb zircon ages from granitic rocks from the Whitmore Mountains (208.0 Ma), Nash Hills (177.4-177.3 Ma), Linck Nunatak (175.3 Ma), Pagano Nunatak (174.8 Ma), and the Pirrit Hills (174.3-173.9 Ma), and U-Pb sensitive high-resolution ion microprobe (SHRIMP) ages from the Whitmore Mountains (200 ± 5 Ma), Linck Nunatak (180 ± 4 Ma), Pagano Nunatak (174 ± 4 Ma), and the Pirrit Hills (168 ± 4 Ma). We then compared these results with existing K-Ar ages and Nd model ages, and used initial Sr, Nd, and Pb isotope ratios, combined with xenocrystic zircon U-Pb inheritance, to infer characteristics of the source(s) of the parent magmas. We conclude that the Jurassic plutons were not derived exclusively from crustal melts, but rather they are hybridized magmas composed of convecting mantle, subcontinental lithospheric mantle, and lower continental crustal contributions. The mantle contributions to the granites share isotopic similarities to the sources of other Jurassic LIP mafic magmas, including radiogenic 87Sr/86Sr (0.706-0.708), unradiogenic 143Nd/144Nd (εNd < -5), and Pb isotopes consistent with a low-μ source (where μ = 238U/204). Isotopes and zircon xenocrysts point toward a crustal end member of predominantly Proterozoic provenance (0.5-1.0 Ga; Grenville crust), extending the trends illustrated by Ferrar mafic intrusive rocks, but contrasting with the inferred Archean crustal and/or lithospheric mantle contributions to some basalts of the Karoo sector of the LIP. The Ellsworth-Whitmore terrane granites are the result of mafic rocks underplating the hydrous crust, causing crustal melting, hybridization, and fractionation to produce granitic magmas that were eventually emplaced as post-Ferrar, within-plate melts at higher crustal levels as the Ellsworth-Whitmore terrane rifted off Gondwana (47°S) before migrating to its current position (82°S) in central Antarctica. [ABSTRACT FROM AUTHOR]

This paper presents the results of U–Pb dating of detrital zircons from six metasedimentary rocks in the Taowan and Kuanping groups in the northern margin of the North Qinling Orogenic Belt (NQB), Central China, for constraining the tectonic affinity of the NQB, the existence time and tectonic features of the Kuanping Ocean and the accurate northern boundary of the NQB. Zircon U–Pb dating indicates that the protoliths of the two metasedimentary rocks from the upper and lower parts of the Taowan Group were deposited later than ∼1111 and ∼871 Ma respectively. However, the protoliths of the four metasedimentary rocks from different layers of the Kuanping Group were deposited later than ∼781, ∼668, ∼515 and ∼477 Ma, respectively, suggesting that the Taowan Group and the Kuanping Group both have an abnormal or non-Smithian stratigraphic sequence. The age populations and predominant peak ages of detrital zircon grains from the Mesoproterozoic–middle Neoproterozoic metasedimentary rocks in the Taowan and Kuanping groups indicate that their provenances were mainly attributed to the NQB and subordinately from the Yangtze Craton (YZC), suggesting that the two groups both belong to the NQB and the northern boundary of the NQB should be placed to the north of the Taowan Group, which can be called the Paleo-Luonan–Luanchuan Fault. However, the Nd–Pb whole-rock isotopes, zircon Hf isotopes and trace element compositions of the Precambrian basement rocks and the Neoproterozoic granitic magmatic events in the NQB are significantly different from those in the YZC, suggesting that the NQB was more likely to be an independent microcontinent adjacent to the YZC from the Mesoproterozoic to the Neoproterozoic, and experienced a unique geological history. On the other hand, together with the record of the oldest MORB-type basalt with an age of 1445 Ma in the Kuanping Group, the first late Mesoproterozoic sedimentary record (∼1111 Ma) in the Taowan Group, to be reported using precise geochronological data in this study, it indicates that the Kuanping Ocean separated the NQB from the NCC that had already existed to the north of the NQB before the Mesoproterozoic, and was a major ocean basin which had lasted for a long time, rather than as a back-arc basin. [ABSTRACT FROM AUTHOR]

Data from ophiolites indicate that the Longmuco–Shuanghu Suture Zone (LSSZ) was connected with the Changning–Menglian Suture Zone (CMSZ) during the Paleozoic. Numerous geological records of late Cambrian–Silurian arc magmatism have been found along the LSSZ and CMSZ. However, all the reported early Paleozoic arc magmatism in the South Qiangtang subterrane (SQT) was based on crust-derived magmatic rocks, which constrained our acknowledge of the complicated geodynamic evolution processes. Here, we present bulk-rock geochemistry, Sr Nd isotopes, and zircon U Pb dating and Hf isotope data for a newly discovered Silurian complex in the Xiangtaohu (XTH) area of the central Qiangtang Terrane, central Qinghai–Tibetan Plateau, to investigate the magmatic and tectonic evolution of the LSSZ and CMSZ. The XTH complex is composed of diorite, monzogranite, and biotite monzogranite. Zircon U Pb dating results show that the XTH complex was emplaced at 438–429 Ma. The diorites belong to the calc-alkaline to high-K calc-alkaline series, showing metaluminous to weakly peraluminous features. All of the granites are high K, calc-alkaline, and weakly peraluminous. The diorites have low initial 87Sr/86Sr ratios (0.704526–0.705002) and ε Nd (t) values (−1.32 to 0.12), with zircon ε Hf (t) values ranging from −1.2 to 0.4, indicating a metasomatic mantle source with subducted-sediment-derived melts, and low MgO, Mg#, Cr, and Ni values, reflecting crystal fractionation from basaltic magma. The monzogranites and biotite monzogranites show I-type granite geochemical affinity, with slight negative ε Nd (t) values (−2.03 to −1.67) and low initial 86Sr/86Sr values (0.704056–0.705165), with zircon ε Hf (t) values ranging from −3.1 to 4.8, suggesting that they were derived mainly from partial melting of juvenile mafic lower crust. The samples are enriched large-ion lithophile elements, depleted high-field-strength elements, and have high U/Yb ratios of zircons, suggesting that the XTH complex was formed in a continental arc setting. The XTH Silurian complex is the youngest magmatic record of the southward subduction of the Longmuco–Shuanghu Prototethys oceanic plate, which represent the melting productions of the mantle wedge and mafic lower crust. It is different from the previously discovered S-type granites in the same area. Combining our new results with comprehensive existed data in the region, we propose that the Changning–Menglian Prototethys oceanic plate subducted beneath the Baoshan block (eastward) and the Yangtze block (westward) during early Paleozoic, while the Longmuco–Shuanghu Prototethys oceanic plate only subducted southward under the southern Qiangtang subterrane. [Display omitted] • Newly discovered Silurian magmatic complex developed at Xiangtaohu area in the LSSZ. • The Xiangtaohu complex has continental margin arc affinity. • Arc magmatic rocks derived from melting of mantle wedge and basic lower crust. • The southward subduction of the LSTO lithosphere. [ABSTRACT FROM AUTHOR]

Abstract The South Tianshan Orogenic Belt (STOB) occupies the southwestern margin of the Central Asian Orogenic Belt (CAOB), and is the key region to understanding the Paleozoic evolution of the southern part of the Palo-Asian Ocean. Here we present an integrated study of zircon U–Pb ages, whole-rock major and trace elements and Sr–Nd isotopes on Silurian and Late Carboniferous intermediate-felsic intrusions exposed in the Oxidaban area located in the South Tianshan region in Xinjiang, NW China. The Silurian intrusion is composed of quartz diorite, granodiorite and monzogranite, whereas the Late Carboniferous rocks include granite porphyry and granite porphyry enclaves. LA–ICP–MS zircon U–Pb dating yields ages of 426.8 ± 4 Ma for quartz diorite and 424.5 ± 4 Ma for monzogranite, respectively. The quartz diorite shows middle–K calcic and metaluminous affinity, and the granodiorite exhibits similar features, but peraluminous. They display enrichment in large-ion lithophile elements (LILEs) and depletion of high field strength elements (HFSEs) together with negative Eu anomalies, broadly comparable with typical arc-type rocks. They have similar Sr–Nd isotopic compositions, with a narrow range in (87Sr/86Sr) i of 0.70578 to 0.70644 and ε Nd (t) of −0.95 to −2.16. Based on geochemical and isotopic characteristics, we infer that the granodiorite is produced by fractional crystallization of quartz diorite rocks, which were dominantly produced by partial melting of medium to high–K basaltic protoliths. Besides, the monzogranite also exhibits arc-type geochemical signatures, which we correlate to partial melting of middle-lower juvenile crust and subsequent contamination by ancient crust during ascent and emplacement. Zircon LA–ICP–MS U–Pb analyses yielded crystallization ages of 300.4 ± 1.5 Ma for the granite porphyry and 304.8 ± 2.3 Ma for the granite porphyry enclave. These rocks are dominantly shoshonite and peraluminous, and are likely derived from partial melting of the greywacke mixed with minor pelitic components. The low Al 2 O 3 /TiO 2 (<100) ratios suggest a high temperature condition, which may be attributed to heat input from underplated mantle-derived magmas in the post-collision extension setting. Base on these scenarios, we propose that the bi-directional subduction of the South Tianshan Ocean occurred during the Early Paleozoic and the subduction polarity changed to northward during Middle Devonian, followed by the collision between Yili-Central Tianshan Block and Tarim Craton in the Late Carboniferous. Highlights • Silurian and Carboniferous felsic magmatic suite in the STOB. • Zircon U–Pb dating yields emplacement ages of ca. 425 Ma and ca. 300 Ma. • Southward subduction of the South Tianshan Ocean in the Early Paleozoic. • The final collision is constrained to have occurred before ca. 300 Ma. [ABSTRACT FROM AUTHOR]

The geological history of the Amazon River is a complex story driven by geodynamic processes operating in the South American plate. In spite of recent research, the pre-Neogene structure of Amazon paleodrainage is still underconstrained. A recent study has suggested that the western Amazonian paleodrainage system was reversed, cratonic in origin during the Cretaceous. However, the extent and duration of this system are not well-constrained. To add new constraints, we investigated the sources of Cretaceous sedimentary rocks in the Brazilian Acre and Peruvian Madre de Dios basins, based on major and trace element concentrations, Sm–Nd isotopic compositions, and U–Pb detrital zircon dating. The late Cretaceous samples of the Acre Basin have ε Nd (0) values between −21.2 and −8.4 and zircon grains derived from terranes situated in the easternmost part of the Amazonian Craton: Ventuari–Tapajos (2.0–1.82 Ga) and Rio Negro–Juruena (1.82–1.54 Ga). In contrast, the Madre de Dios Basin samples have ε Nd (0) values ranging from −15.2 to −7.1 and a wide range of U–Pb zircon age distributions. The samples from the northern part of the basin (MD234 and MD238) are dominated by zircon ages between 0.9 and 1.3 Ga (Grenville/Sunsás, 30 %–43 %) and 0.5 and 0.7 Ga (Brazilian/Pampean, 26 %–16 %) with felsic provenance. The oldest MD234 sample also shows a dominant contribution from Paleozoic zircon (20 %). On the other hand, the samples from the southern part of the Madre de Dios Basin (samples MD-2019-4A; MD-2019-10; MD-2019-13; MD-2019-11D and MD-2019-12A) have U–Pb age distributions dominated by zircon ages between 0.9 and 1.3 Ga (Grenville/Sunsás, 30 %–45 %) and 1.54 and 1.3 Ga (Rondonia–San Ignácio, 16 %–43 %), pointing to a cratonic origin for these sedimentary rocks. To elucidate the distinction in provenance between the samples from the northern and southern parts of the Madre de Dios Basin, we suggest that a structural barrier (the Madidi Arch (?)) was active during the late Cretaceous. In this scenario, the northern part of the Madre de Dios Basin had similar sedimentary sources as the nearby basins like Huallaga, Bagua, Ucayali, and Marañón, whereas, in the southern part of the basin, sedimentation was influenced by local sources. Together with previously published studies, these data indicate that the continent-wide cratonic drainage developed between the Cenomanian and Maastrichtian in response to the Purus Arch uplift was probably driven by a geodynamic process related to the post-rift opening of the Atlantic Equatorial Ocean. [ABSTRACT FROM AUTHOR]

Accretionary orogens are the primary sites for continental growth, but the rate and amount of crust generation throughout its evolution are poorly constrained. In this contribution, our new results about the genesis of two intermediate-felsic plutons are combined with a compiled granitoid dataset to evaluate the amount and rate of crustal growth throughout the evolution of the Western Kunlun orogen, which is a typical accretionary orogen associated with the consumption of the Proto-Tethys during the early Paleozoic. The ca.446 Ma Sanshili pluton was formed through interactions between metasomatized mantle wedge-derived oxidized magmas and the lower arc crust, as indicated by high whole-rock Mg#, high Ce4+/Ce3+ ratios (308–861) of ca.446 Ma zircons, and the existence of inherited zircons with ages of 546–472 Ma. The Yirba dioritic to granodioritic pluton was emplaced at 474 ± 3 Ma. Samples from the Yirba pluton are characterized by high K 2 O content, higher Mg# (40–49) than pure crustal melts, slightly higher Y + Nb concentrations, and high Th/Nb ratios, and slightly enriched to depleted Hf–Nd isotopes. Combined with the presence of the 502–531 Ma inherited zircons, the Yirba pluton is suggested to from through differentiation of the metasomatized lithospheric mantle derived-magmas beneath the juvenile intra-oceanic arc in combination with crustal reworking during regional extensions. The Yirba pluton, together with contemporary A 1 -type granites, thus marks an extension event at ca. 475 Ma in the Western Kunlun orogen. The compiled dataset reveals three magmatic flare-ups at 530–500 Ma, 480–470 Ma, and 445–430 Ma, corresponding to two slab rollback events and the slab break-off after the final closure of the Proto-Tethys. The three episodes of more intensive magmatism are associated with more radiogenic Hf–Nd isotopes and increased Nb/La and Nb/Y ratios, indicating more contributions from intraplate-like sources during lithospheric extensions. Meanwhile, element ratios (La/Yb, Sm/Yb, and Sr/Y) that are sensitive to crustal thickness are also elevated. These phenomena are consistent with rapid juvenile crust generation during extensional stages of accretionary orogens. Our study has also shown that the rate of new crust production is quite uniform for different extensional events. The crustal generation rate during slab break-off is much higher than that during slab rollback, although the proportions of juvenile inputs in granitoids formed during slab rollback are relatively higher. This may reflect extra inputs from partial melting of oceanic slabs and subducting sediments like those in continental collision zones and/or rapid asthenospheric upwelling coupled with enhanced crust reworking during slab break-off. • The Yirba pluton was formed at ca.475 Ma during regional extensions. • There are three magmatic flare-ups in the Western Kunlun orogen. • The crust generating rate is uniform for different extensional events. [ABSTRACT FROM AUTHOR]

The article offers study of the tectonic evolution history of the Early Paleozoic in the middle of the north margin of the North China Craton, and provides evidence for the regional tectonic evolution and solution of geological problems. Topics include samples for zircon dating, and zircon Hf isotopic analyses were collected from tonalite in the Yangjiawopu village, Faku County, Liaoning Province; and concluded the discovery of Early Paleozoic igneous rocks in the Songliao Basin.

Debate on whether the Early Paleozoic tectono-magmatic event in South China is related to a subduction–collision or an intracontinental orogen has been lasted for decades within the geoscience community. This study deals with LA-ICP-MS zircon U–Pb ages, whole-rock chemistry, rare earth elements, trace elements and Hf isotopes from granitoid samples collected in the Yunkai domain in order to better constrain the Early Paleozoic tectonic evolution of the South China Block. The weighted mean 206 Pb/ 238 U ages for eight samples range from 426 Ma to 443 Ma, representing the crystallization ages of the magma. Fourteen samples were analyzed for geochemistry, all of which are characterized by a peraluminous signature with A/CNK values greater than 1.0. The REE geochemistry reveals enrichment in light rare earth element. LREE/HREE values range from 2.81 to 30.36 and (La/Yb) N vary from 1.23 to 55.14 (mean of 14 analyses is 14.69). All the samples exhibit distinct negative Ba, Sr and Nb anomalies and enrichment in Rb, Th, U and Pb. Hf isotopic analyses indicate negative εHf (t) values mainly ranging from − 3 to − 12, corresponding to two model age distributing from 1637 Ma to 2208 Ma. The geochemical analyses indicate that the Silurian granitic magmas in the Yunkai domain were derived from partial melting of crustal materials with little or no input of mantle source. These new data support the intracontinental subduction model already proposed to account for the Early Paleozoic tectonic, metamorphic and magmatic event of South China. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fourth member of the Qiasi Group was deposited at ca. 456 – 419 Ma. • Provenance of Ediacaran and early Paleozoic clastic rocks is markedly different. • The Yidun Terrane was linked with East Gondwana in the early Paleozoic. The Yidun Terrane, sandwiched between the Qiangtang and Songpan-Ganze terranes, hosts important information on the tectonic evolution of the eastern Tibetan Plateau. However, its tectonic link with adjacent terranes and East Gondwana remains equivocal. Here, we present U-Pb-Hf isotopes of detrital zircons from the upper Neoproterozoic-lower Paleozoic clastic rocks in the Yidun Terrane. The results show that detrital zircons from the Neoproterozoic rocks are mainly of ca. 821 – 890 Ma, 1714 – 1977 Ma, and 2317 – 2520 Ma, with ε Hf(t) values of each group comparable to coeval magmatic rocks in the nearby South China Block. This suggests that the Yidun Terrane and South China were possibly connected in the late Neoproterozoic, with the latter being the main sedimentary provenance. In contrast, the five Paleozoic samples have markedly different detrital zircon age spectra at ca. 2600 – 2300 Ma, 1100 – 900 Ma, 900 – 740 Ma, and 690 – 480 Ma, which were interpreted to have derived from Pan-African and Grenville-age provinces in the East Gondwana, as well as the South China Block and Songpan-Ganze Terrane. Such a major change on provenance suggests that after prolonged isolation in the Proto-Tethys, the Yidun Terrane began to collide with the East Gondwana in late Ediacaran to early Paleozoic. Integrated with published works, we consider that the Yidun Terrane, along with Songpan-Ganze Terrane and Yangtze Block, was located on the northern margin of East Gondwana during the early Paleozoic. [ABSTRACT FROM AUTHOR]

Precise timing of granitoids and constraints of their magma sources are critical to understanding the subduction–collision tectonic evolution of the Altun orogenic belt (AOB), a vital part of the Qinghai-Tibet plateau in northwestern China. We provide in-situ zircon U–Pb age, Hf isotopic composition and whole-rock geochemistry of the Yusupualeke granitic pluton in the South Altun orogenic belt (SAOB), an integral unit of the AOB, to determine the tectono-magmatic evolution of the SAOB at early Palaeozoic. The Yusupualeke granitic pluton comprises the medium-coarse grained porphyritic monzogranite and medium-fine grained granodiorite. The monzogranite sample yielded a weighted mean 206Pb/238U age of 476.8 ± 3.6 Ma (MSWD = 0.59), while the granodiorite yielded a weighted mean 206Pb/238U age of 453.2 ± 4.7 Ma (MSWD = 0.013). Zircon U–Pb ages suggest that the subduction–collision process of the SAOB remained from the middle stage of the early Palaeozoic to the end. Both of the studied granitoids belong to metaluminous to weakly peraluminous series and show typical I-type granite characteristics with depletions in Ba, Nb, Sr, P, and Ti, and enrichments in light rare earth elements (LREEs), Rb, Th, K, and slightly negative Eu anomalies. Based on the geochronological data and regional geological background, we believe that the porphyritic monzogranites were formed during the northward subduction process of the South Altun ocean (SAO), while the granodiorites were formed during the tectonic regime transition stage. Besides, combing the previous research achievements with our newly obtained data, we put forward a new division and geodynamic model of the early Palaeozoic tectono-magmatic evolution for the South Altun orogenic belt. [ABSTRACT FROM AUTHOR]

• The gneisses record two period metamorphic events as Neoproterozoic and early Paleozoic metamorphism. • 920–929 Ma from granitic gneisses and ca. 0.9 Ga from paragneisses represent the Neoproterozoic tectono-thermal event. • The early Paleozoic metamorphic ages given by the rim domains of zircons from gneiss samples record the the UHP-HP metamorphic evolution in EKO. The East Kunlun Orogen (EKO) is a long-lived accretionary orogenic belt that records the Paleozoic–Mesozoic amalgamation processes of the East Asia continent. The belt consists mainly of various kinds of gneisses with minor amounts of eclogite and garnet amphibolite occurring as lenses. We report zircon U–Pb ages and Hf–O isotopic compositions for the granitic gneisses and paragneisses in the Xiarihamu area near Golmud in Qinghai Province, to investigate the metamorphic history and evolution of the orogenic belt. For the granitic gneisses, zircon U–Pb chronology reveals a Neoproterozoic magmatic event and an early Paleozoic metamorphic event. The magmatic crystallization ages of the two granitic gneisses are 920 ± 6 and 929 ± 2 Ma, and yield ε Hf (t) values of −8.4 to 1.7 and δ18O values of 7.94–11.19‰, suggesting their derivation mainly from continental crustal materials. The detrital zircons from the paragneisses record a Neoproterozoic metamorphic event and a Paleozoic metamorphic event. Most of the detrital zircons from the two paragneiss samples yielded ages of 2.1–0.9 Ga, indicating that the sources of the sediment were formed mainly during the Neoproterozoic to Paleoproterozoic. These Neoproterozoic magmatic and metamorphic events suggest that the EKO underwent a Neoproterozoic tectonothermal event that was related to the assembly of the Rodinia supercontinent. The similar tectonic histories of the EKO and North Qaidam belt (NQB) indicate they were probably part of a single tectonic unit during the Neoproterozoic. Some of the zircons have metamorphic overgrowth rims yielding two stages of Paleozoic metamorphic ages of ca. 440 Ma (438 ± 2 Ma) and ca. 420 Ma (419 ± 6 Ma, 416 ± 6 Ma, and 423 ± 6 Ma). Combined the discover of high-pressure mineral inclusions (jadeite + quartz) in these rims with the results in previous studies, the ages of these rims (ca. 440 Ma and ca. 420 Ma) are suggested to represent of HP-UHP metamorphism of the EKO. These age data imply that the gneisses in this study might share common early Paleozoic metamorphic event with the HP–UHP eclogites in the EKO. [ABSTRACT FROM AUTHOR]

The Baoshan block is one of the important members in the southeastern margin of the Tibetan Plateau. Cambrian to Jurassic (meta-) sedimentary strata and their metamorphic counterparts were well preserved in the eastern part of the Baoshan block. Zircon U–Pb dating, trace elements, and Hf isotope data for both the Cambrian to Jurassic (meta-) sedimentary sequences and the Lincang granite were used to deduce the provenance of sediments and crustal affinity with eastern Gondwanaland. The Lincang granite outcropped in the Fengqing area is typical S-type, with crystallization age of ~ 230 Ma and narrow range of zircon ε Hf (t) values from − 15.5 to − 10. Detrital zircons from Paleozoic strata range in age from Archean to early Paleozoic, with age peaks at ~ 2.5, ~ 0.95, and ~ 0.6 Ga. Triassic age peak (~ 230 Ma) was also detected in the Jurassic strata. Detrital zircon ε Hf (t) values exhibit a wide range from negative to positive for each of the four major age groups, showing the host magma of zircons from these groups have diverse sources. The Baoshan block should be along the Indian margin as the Qiangtang, Tengchong and Simao–Indochina blocks in Early Paleozoic based on the provenance analyses. Sediment inputs eroded from both the Lincang granite and the coeval igneous rocks in the Baoshan and Gongshan blocks were the dominant contributions to the Jurassic strata after the amalgation of the Baoshan and Simao–Indochina blocks. Tectonic processes linking dispersion of the Baoshan–Sibumasu terrane from the Gondwana supercontinent to the collision with the Simao–Indochina block and the deposition of the Cambrian to Jurassic sedimentary sequences were reconstructed. [ABSTRACT FROM AUTHOR]

This work presents the first results of dating of detrital zircons ( dZr) from the Lower Paleozoic terrigenous-carbonate rocks of the Cambrian Blåstertoppen (samples 08-137 and 08-142, south of the Wedel Jarlsberg Land) and Ordovician Wiederfjellet (sample K06-17, north of the Land) sequences, which are widespread to the north and south of the Hornsund Fjord, on the southwestern coast of Spitsbergen Island. Against the background of sporadic values of 1-3 Ga, samples K06-17 and 08-142 showed similar spectra of the age distribution of dZr with dominant compact numerous age groups of ∼1.8-1.9 Ga and peaks of the maximum of the probability density of 1850 and 1862 Ma, respectively. The only noticeable difference in these spectra is the presence of a young grain of 541 Ma in sample 08-142 (with a very good value of concordance), which is close to the suggested Cambrian age of formation of the Blåstertoppen sequence. The distribution of the dZr ages in sample 08-137 is significantly distinct. First, the general age range is narrower: 1.15-1.95 Ga (no Archean ages). Second, the age of 1.8-2.0 Ga dominant in the other two samples corresponds to only one grain. Thus, although samples 08-137 and 08-142 were taken from closely located levels of the section of the Cambrian Blåstertoppen sequence (in the same interception), the age spectra of dZr from these samples differ cardinally. The statistical Kolmogorov-Smirnov test quantitatively supports the visual similarity of age spectra of dZr from samples K06-17 and 08-142 ( p = 0.913) and the distinction of those from samples 08-142 and 08-137 ( p = 0). Thus, the provenance areas, which supplied the clastic material to the sedimentary basin, whose remnants are presently located in the southwestern part of Spitsbergen, abruptly changed in the Cambrian. The basal levels of the Cambrian section of this basin (sample 08-137) were mostly formed due to accumulation of the erosion products of the local (Spitsbergen) sources: metarocks of the Eimfjellet Group located in the south of the Wedel Jarlsberg Land and of the Smerenburgfjord Group abundant on the Albert I Land. The dZr age spectrum is a print of the ages of the Late Paleoproterozoic-Mesoproterozoic (pre-Grenville) basement unaffected by assemblage of Rodinia. Then the conditions changed and the basin became to accumulate the material from the remote regions, significant parts of which were the areas of ancient cratons, including Archean blocks. The general sedimentation conditions did not change considerably, because the rock type remained the same. [ABSTRACT FROM AUTHOR]

The Miao’ershan–Yuechengling batholith (MYB) is one of the largest granitic batholiths in South China. At least five individual phases have been identified for the Paleozoic granites in the MYB. SHRIMP and LA–ICP–MS zircon U–Pb dating results imply that these granites were emplaced at 435±4Ma, 427±3Ma, 417±6Ma, 404±6Ma and 382±2Ma, respectively. The ages gradually decreased from the southeast to the northwest, implying that the MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian. Most granites are metaluminous to weakly peraluminous, and contain low P2O5 contents (<0.15%). These granites show enrichment of Rb, Th, U and depletion of Ba, Sr, Eu, Ti. They show relatively high (87Sr/86Sr)i ratios (>0.715), low ε Nd(t) values (−8.9 to −6.7), and low zircon ε Hf(t) values (−9.5 to −4.0). These geochemical and isotopic characteristics indicate that these granites may have formed from partial melting of Paleoproterozoic basement rocks. Slight geochemical differences between different phases can be interpreted as resulting from partial melting of heterogeneous sources or different proportion mixing of meta-igneous and meta-sedimentary rocks. Zircon Hf isotope model ages vary from 1.77 to 1.93Ga, with an average value of 1.84±0.07Ga. These data indicate that crust growth in this region took place mainly during the Paleoproterozoic (ca. 1.84Ga), and the basement in the MYB should belong to the Cathaysia Block. The formation of the Paleozoic granites in the MYB was suggested to be related to the late orogenic magmatism of the Wuyi–Yunkai orogeny. Thus, the late orogenic magmatism in the northwestern part of the Wuyi–Yunkai orogeny must have lasted until ca. 381Ma and took place also to the east of the Anhua–Luocheng Fault. [ABSTRACT FROM AUTHOR]

• The sediments in the Qinling Group were deposited in an accretionary or collisional setting during the Early Neoproterozoic. • The main provenance of sediments in the Qinling Group was the North Qinling Terrane itself and East Laurentia. • The North Qinling Terrane was located between the North China Craton and East Laurentia in Rodinia. • The microcontinent may provide a missing link in supercontinent reconstruction. The North Qinling Terrane was a microcontinent in the Late Neoproterozoic and then subducted northwards beneath the North China Craton for regional metamorphism in the Early Paleozoic. In order to constrain its location in supercontinent Rodinia, metasedimentary rocks were sampled from it for a combined study of whole-rock major and trace elements as well as zircon U-Pb ages and Lu-Hf isotopes. The metasedimentary rocks show greywacke compositions with A/CNK ratios of 0.99–1.28 and upper continental crust-like trace element patterns. They have metamorphic ages of ca. 510–490 Ma, recording continental collision for the regional metamorphism. The youngest detrital zircon U-Pb ages from three metasedimentary rocks are 1161 ± 54 Ma, 954 ± 15 Ma, 861 ± 10 Ma, respectively. In combination with ages of granitic intrusions of 960 to 890 Ma in the target region, their deposition ages are constrained to be 1110–960 Ma, ca. 960 Ma and ca. 860 Ma, respectively. The cumulative proportions of the difference between the detrital zircon crystallization ages and the deposition ages for the sediments of ca. 960 Ma and ca. 860 Ma suggest their deposition in a collisional setting. Detrital zircon age spectrum from the Qinling Group yields two major populations at 1000–900 Ma and 1700–1400 Ma and three subordinate populations at 900–800 Ma, 1300–1200 Ma and 1800–1700 Ma with rare Neoarchean grains. Neoproterozoic detrital zircons mainly have negative ε Hf (t) values, consistent with Neoproterozoic granitoids in the North Qinling Terrane. On the other hand, Mesoproterozoic detrital zircons mainly have positive ε Hf (t) values, similar to those in East Laurentia and East Greenland. This means that the major provenance of sediments in the Qinling Group was the North Qinling Terrane itself and East Laurentia, supporting the connection between the North Qinling Terrane and East Laurentia in Rodinia prior to its breakup. In combination with the coeval strata in the southern margin of the North China Craton, we propose that the North Qinling Terrane is a missing piece connecting the southern margin of the North China Craton with the northern part of East Laurentia in Rodinia in the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ordovician to Triassic maximum depositional ages are determined from Sibumasu in NW Thailand. • 1200–900 Ma, 650–500 Ma and 2500–2460 Ma populations are present in all 8 NW Thai detrital samples. • Hf signatures change provenance from Gondwana in Ordovician-Permian to Indosinian in Triassic. • Our comparison with published detrital data is inconsistent with composite Sibumasu models. The evolution of the Sibumasu Terrane forms a principal component in the history of the Tethys Oceans with the northward movement of Gondwana-derived terranes creating the Asian continent that we recognise today. While there are various reconstructions for the palaeoposition of the Sibumasu Terrane during the Proterozoic and Paleozoic, the terrane is commonly placed outboard of the northwest Australian margin in the Gondwanan supercontinent. In this study, U–Pb and Lu–Hf isotopic information has been collected from detrital zircons of Paleozoic and Mesozoic sedimentary rocks obtained from the Sibumasu Terrane in northwest Thailand. This is the first zircon Hf analysis from these sedimentary sequences. These new data are statistically and visually compared with data from Sibumasu, Indochina, Sukhothai, West Burma and Tethyan Himalayas terranes along with the terranes of China, India and Western Australia. Our detrital data are consistent with other published data indicating consistent sources across the Sibumasu Terrane, inconsistent with composite terrane reconstructions. However, temporally, the detrital ages change from older Paleozoic sedimentary sequences (sourcing zircons from Neoproterozoic and older "Gondwanan" sources) to latest Permian-Triassic sedimentary units with Indosinian zircon sources. This change is consistently reflected in this study through both the U–Pb ages and Hf signatures with Proterozoic age peaks characteristic of Gondwana and younger Indosinian sources being consistent with granitoids emplaced through the amalgamation of Thailand. The temporal changes in the isotopic systems reflect the movement of the Sibumasu Terrane from the northwest Australian margin of Gondwana to its collision with the terranes of present-day Asia. [ABSTRACT FROM AUTHOR]

The oldest-known air-breathing land animal is the millipede Pneumodesmus newmani, found in the Cowie Harbour Fish Bed at Stonehaven, Scotland. Here we report the youngest, most concordant 238U-206Pb zircon age from ash below the fish bed of 413.7±4.4 Ma (±2σ), whereas the youngest age from a tuffaceous sandstone above the fish bed is statistically indistinguishable at 414.3±7.1 Ma. The Cowie Harbour Fish Bed thus appears to be lowermost Devonian (Lochkovian), contrary to the previously accepted mid-Silurian age based on palynomorphs from adjacent exposures. This has implications for the evolutionary timetable of land colonization, as the Cowie ages overlap late Lochkovian zircon ages reported elsewhere for andesite below the nearby (~50 mi) Rhynie Chert, which has more advanced terrestrial biota. The results postdate the possible late Silurian Ludford Lane locality in Shropshire, England. Pneumodesmus newmani is thus not the earliest air-breathing land animal, unless the Ludford Lane locality is younger than presently assigned. [ABSTRACT FROM AUTHOR]

The Song Ma zone in NW Vietnam bears important tectonic implications as a potential subduction corridor between the Indochina and South China blocks. On the basis of U-Pb ages, the Hf isotopic characteristics of zircons and the geochemical composition of granitoids, a two-stage magmatic evolution process of the Song Ma zone at ~290-260 and ~245-230 Ma can be proposed. Isotopic analyses indicate magmatic contributions from Neoproterozoic oceanic island basalt, Proterozoic continental crust, and depleted mantle or juvenile lithosphere. By combining geochronological and geochemical data from the granitoid rocks, we suggest that the staged magmatic processes of Song Ma zone may be related to a long-lasting period of ocean subduction (ca. 290-260 Ma) and subsequent syn-/post-collisional evolution (ca. 245-230 Ma). [ABSTRACT FROM AUTHOR]

U–Pb and Lu–Hf isotopic data of detrital zircons from late Paleozoic and Mesozoic strata along the southern flank of the Chinese western Tianshan enable to identify provenance changes and reconstruct early stage uplift and denudation history of the Tianshan range. Detrital zircons from Permian and Early–Middle Triassic siliciclastic rocks show two prominent age populations at 500–390 Ma and 310–260 Ma, and subordinate Precambrian ages at ~ 2.5 Ga, 2.0–1.7 Ga, 1.2–0.9 Ga and 900–600 Ma, with rare ages between 390 and 310 Ma. These characteristics and zircon ε Hf (t) data consistently suggest a sediment source predominantly from the Tarim Craton, rather than the Central Tianshan–Yili Block. In contrast, Late Triassic to Cretaceous strata additionally contain abundant 390–310 Ma and 260–220 Ma detrital zircons, implying multiple source regions from the Central Tianshan–Yili Block, Tarim Craton, and Western Kunlun Orogen. A significant switch of sedimentary provenances occurred in the mid-Triassic and is consistent with contemporaneous change of paleocurrent directions and the onset of intense tectonothermal events in the broad region of the Chinese western Tianshan and Kyrgyz Tianshan. These data collectively indicate that the significant surface uplift and denudation of the Tianshan range were probably initiated in the mid-Triassic (~ 240 Ma) after the assembly of the southwestern Central Asian Orogenic Belt. This uplifting event represents an intracontinental orogeny most likely in response to the collision between the Qiangtang Block and southern Eurasia, following the closure of the western part of the Paleo-Tethys Ocean. [ABSTRACT FROM AUTHOR]

The bimodal association of basalts and rhyolites in the Hongshankou area of the East Tianshan area (NW China) provides an important suite to investigate magma petrogenesis and tectonics evolution in a convergent margin setting. In this study we present petrological, geochemical and zircon U–Pb geochronological data from the basalts and rhyolites. Zircons from the basalts yield crystallization ages of 347.1±3.9Ma whereas those from the rhyolites are dated as 344.4±1.9 and 345.0±2.5Ma. The major and trace element signatures of basalts suggest high alumina basalt (HAB) as the source magma which was generated from metasomatised asthenosphere mantle. Both the mafic and felsic rocks are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and are depleted in high field strength elements (HFSE). Broadly homogenous Rb–Sr and Sm–Nd isotopic compositions of mafic and felsic rocks are also characteristic. The basalts display a distinct enrichment in incompatible elements and positive εNd(345Ma) (from +5.87 to +8.25). We envisage a subduction-related origin to account for the LILE enrichment with arc-like melts (enriched in Th and LREE and depleted in Nb, with εNd(345Ma)>+6) produced through the partial melting of a depleted-mantle source, and the involvement of minor crustal component. The rhyolites also display high εNd(345Ma) (from +6.35 to +8.53). Consequently, we suggest a mixing process between a source similar to mid-ocean ridge basalt (depleted end-member mantle) and arc-like magmas for the petrogenesis of the mafic rocks, whereas the rhyolites are best interpreted to have formed by fractional crystallization from the parental magma of the basalts. Several lines of evidence from elemental and isotopic geochemistry suggest a close genetic relationship between the mafic and felsic rocks in the Hongshankou bimodal suites. We propose that the essentially bimodal character of this complex reflects the features of back-arc extensional magmatism, induced by the subduction of the Junggar plate during the Late Paleozoic. [ABSTRACT FROM AUTHOR]

The main rock types of the Boluonuo and Daguangding plutons are diorite, quartz diorite, tonalite, granodiorite, and subordinate plagioclase-bearing hornblendite and hornblende gabbro. Zircon SHRIMP U-Pb dating for a quartz diorite of the Boluonuo pluton suggests that the pluton was emplaced at about 296 ± 4 Ma. Plagioclase-bearing hornblendites show typical cumulative textures, which, in combination with their convex-upward REE patterns and the large variation of compatible elements such as Co, V and Sc, suggests that these hornblendites formed through accumulation of hornblende during magma evolution. Microgranular mafic enclaves (MMEs) are common in the Boluonuo and Daguangding intermediate to felsic plutons. Many plagioclase grains show compositional and textural disequilibrium, with calcium-rich cores (An) mantled abruptly by sodium-rich plagioclase (An). Whole-rock samples of the plutons are characterized by quite negative ɛ( t) values (−16.5 to −11.8) and ɛ( t) values (−22.5 to −16.8), and the ɛ( t) values are negatively correlated with silica contents. All these features suggest that the intermediate to felsic plutons formed through magma mixing of enriched mantle-derived, evolved basaltic magma with granitic, crustal melts, followed by fractional crystallization of mainly hornblende and small amounts of pyroxene, apatite and zircon. The hornblende-dominated fractionation contributed significantly to the adakite-like features of the intermediate to felsic plutons, like the high Sr and Sr/Y ratios and low Yb abundance. In addition, the Boluonuo and Daguangding plutons are highly enriched in LILEs (e.g., Ba and Sr), but depleted in HFSEs (e.g., Nb, Zr and Ti), which is typical of arc magmas. Therefore, the formation of Boluonuo and Daguangding plutons was probably related to the subduction of the Paleo-Asian oceanic slab beneath the North China Craton in the Paleozoic. [ABSTRACT FROM AUTHOR]

Abstract: To achieve a better understanding of the Kwangsian orogenic event of the eastern South China Block, this paper documents a set of new zircon U–Pb geochronological and Hf isotopic data and whole-rock elemental and Sr–Nd isotopic analytical results for the representative massive granite intrusions across the Jiangshan-Shaoxing fault. The studied samples are classified into two groups, representing the rocks from the Cathaysia Block to the east of the Jiangshan-Shaoxing Fault (Group 1) and those from the eastern Yangtze Block between the Anhua-Luocheng and Jiangshan-Shaoxing faults (Group 2). The Group 1 samples gave the zircon U–Pb ages of 405–454Ma and εHf(t) values of −3.6 to −15.2 with Hf model ages of 1.6–2.4Ga. Group 2 yielded the zircon U–Pb ages of 400–432Ma and εHf(t) values of −0.2 to −12.7 with Hf model ages of 1.3–2.2Ga. Geochemically, the Group 1 samples (A/CNK=1.02–1.43) have relatively lower Al2O3, MgO, CaO, P2O5 and εNd(t) but higher K2O+Na2O than those of Group 2 (A/CNK=0.93–1.44). Both groups show similar chondrite-normalized patterns of rare-earth elements with Eu/Eu* values of 0.15–0.92 and strongly negative Ba, Sr, Nb, P and Ti anomalies in primitive mantle-normalized spider diagrams. Their εNd(t) values range from −11.1 to −8.0 for Group 1, and −8.9 to −5.0 for Group 2, generally similar to those of Precambrian paragneiss and contemporaneous gneissoid granites in the eastern South China Block. Our geochronological results indicate that the Kwangsian massive granites in the eastern South China Block were crystallized between 400Ma and 454Ma, synchronous to the Kwangsian gneissoid granites along the Wugong and Wuyi-Baiyun-Yunkai domains in the eastern South China Block. The synthesis of these whole-rock geochemical and in-situ zircon Hf isotopic data suggests that both the Group 1 and 2 granites across the Jiangshan-Shaoxing Fault were predominantly derived from a crustal source with some proportional metapelitic and metaigneous components from the Precambrian basement. The input of juvenile mantle-derived magma is insignificant. Taking into account other available evidences, it is proposed that the Jiangshan-Shaoxing Fault might be a pre-existing boundary between the Yangtze and Cathaysia Blocks, which was reactivated during the middle Paleozoic (Kwangsian) orogenic event. The massive granitic magmatism was probably resulted from the doubly crustal thickening and subsequent isostatic readjustment in an intracontinental tectonic regime. [Copyright &y& Elsevier]

• Part of uppermost basement in the West Kunlun Orogen is early Paleozoic. • Arc-related magmatism in the West Kunlun Orogen continuous during early Paleozoic. • Subduction retreating during Neoproterozoic and advancing during early Paleozoic. • Advancing subduction at 540–420 Ma likely responsible for closure of Proto-Tethys Ocean. The West Kunlun Orogenic Belt (WKOB) is a key area for evaluating the evolution of the Proto-Tethys Ocean. To constrain this history, we present geochemical and zircon U-Pb geochronological data from a suite of metasedimentary rocks within this orogenic belt. Detrital zircons ages are clustered between 1000 and 400 Ma, with major peaks at ca. 510 Ma and 460 Ma, and minor peaks at ca. 840 Ma and 650 Ma. The age groups younger than 1000 Ma broadly overlap magmatic activity at ca. 540–420 Ma and minor magmatism at 920–540 Ma in the WKOB. The age data also reveal Early Paleozoic metamorphic basement rocks in the WKOB that were probably sourced from Kunlun terranes and blocks of Gondwanan affinity rather than the Tarim Craton. Compiled geochemical data suggest a protracted subduction setting in the WKOB in the Early Paleozoic. εHf(t) values show increasing trends at 900–740 Ma and 740–600 Ma and a distinct decreasing trend at 540–420 Ma, consistent with retreating subduction during the Neoproterozoic and advancing subduction in the Early Paleozoic. The retreating-advancing subduction cycle in the WKOB was possibly related to the opening and closure of the Proto-Tethys Ocean along the margin of Gondwana. [ABSTRACT FROM AUTHOR]