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The volcanic rocks of the Chon Aike Silicic Large Igneous Province (CASP) are recognized as magmas dominantly produced by crustal anatexis. Investigating the zircon of the CASP provides an opportunity to gain further insight into geochemical and isotopic differences of the potential magmatic sources (i.e., crust versus mantle), to identify crustal reservoirs that contributed to the felsic magmas during anatexis, and to quantify the contributions of the respective sources. We present a combined zircon oxygen and hafnium isotope and trace element dataset for 16 volcanic units of the two youngest volcanic phases in Patagonia, dated here with LA-ICP-MS U–Pb geochronology at ca. 148–153 Ma (El Quemado Complex, EQC) and ca. 159 Ma (western Chon Aike Formation, WCA). The EQC zircon have 18O-enriched values (δ18O from 7 to 9.5‰) with correspondingly negative initial εHf values (− 2.0 to − 8.0). The WCA zircon have δ18O values between 6 and 7‰ and εHf values ranging between − 4.0 and + 1.5. Binary δ18O-εHf mixing models require an average of 70 and 60% melt derived from partial melting of isotopically distinct metasedimentary basements for the EQC and WCA, respectively. Zircon trace element compositions are consistent with anatexis of sedimentary protoliths derived from LIL-depleted upper continental crustal sources. The overlap between a high heat flux environment (i.e., widespread extension and lithospheric thinning) during supercontinental breakup and a fertile metasedimentary crust was key in producing voluminous felsic volcanism via anatexis following the injection and emplacement of basaltic magmas into the lower crust. [ABSTRACT FROM AUTHOR]

Polycyclic caldera complexes hold clues to understanding why some magmatic systems develop into supersized magma bodies and how they can recover to produce several caldera-forming eruptions. However, the geologic records of the transitions between successive caldera events are very often inaccessible due to limited preservation of eruptive products of inter-caldera activity, prompting the search for alternative archives of magma evolution such as accessory minerals. Here we applied multiple geochemical tools to study one of the most active caldera centres of the Quaternary, the Toba caldera complex in Sumatra (Indonesia), which produced at least four caldera-forming eruptions in the last 1.6 My, including the iconic Youngest Toba Tuff at 74 ka. We combined feldspar 40Ar/39Ar and zircon U–Pb geochronology of proximal pyroclastic deposits with glass and mineral chemistry of both the tuffs and distal marine tephra to revise the eruption chronology of Toba, obtaining new eruption ages of 1417 -31/+14 ka (zircon) or 1339 ± 39/39 ka (plagioclase, internal/full external 2 σ uncertainty) for the Haranggaol Dacite Tuff, 783.81 ± 0.85/1.32 ka (sanidine) for Oldest Toba Tuff, and 503.61 ± 1.36/1.50 ka (sanidine) for Middle Toba Tuff. Isotope dilution thermal ionisation mass spectrometry (ID-TIMS) U–Pb crystallisation ages, trace element contents and Hf isotopic ratios of zircons illuminate changes in the shallow magma reservoir which saw near-continuous zircon crystallisation over 1.6 My. Prolonged build-ups to each eruption with highly scattered zircon trace element compositions reflect a complex, heterogeneous character of the shallow reservoir, without a clear temporal trend or indications of the eruption trigger. In contrast, hafnium isotopes in zircon display a pronounced shift towards unradiogenic values immediately after the OTT caldera collapse, followed by a gradual recovery to a baseline value of ε Hf = -7 at the time of YTT eruption, interpreted as a reflection of the shift in magma reservoir position corresponding to change in the character of assimilated crust. We can show in unprecedented detail how a large caldera collapse affects magma geochemistry; however, identification of patterns in the behaviour of the Toba system and making geochemistry-based predictions about its future development remain a challenge. • 40Ar/39Ar dating and tephra correlations reveal four, not five major Toba eruptions. • Zircon compositions sample a heterogeneous magma reservoir prior to each eruption. • Abrupt shift in zircon ε Hf, bulk 87Sr/86Sr after Oldest Toba Tuff caldera collapse. • Geochemical changes linked to shifting locus of magma accumulation. [ABSTRACT FROM AUTHOR]

Piaoac granites exposed in the Cao Bang region, northern Vietnam, are S-type granite, which are associated with W-Sn-Mo-Be-F mineralization. Zircon U-Pb ages, major and trace elements, mineral chemical and Hf isotopic compositions of the W-Sn-bearing granites from the Piaoac District have been investigated in detail. LA-ICP-MS U-Pb dating of zircon grains from these granites yielded ages of 82.5±2.3 and 82±1.8 Ma, representing an episode of Late Cretaceous magmatic event. These granites are characterized by high peraluminous and have typical S-type geochemical signatures with high SiO2 (72.37 wt.%-73.07 wt.%), high A/CNK values (1.61-1.65) and Аl2О3 (14.4 wt.%-15 wt.%). They are enriched in Rb, U, K, Th, Ta and Pb and display pronounced negative Ba, Sr, Nb, Ti and Eu (Eu/Eu*=0.19-0.24) anomalies. The high degree of fractional crystallization is characterized by low Rb, Sr, Ba and Eu concentrations with high ratios of La/Sm and Eu/Eu*. Zircon grains show εHf(t) values from -9.69 to -0.9 and the corresponding TDm2 range from 1.2 to 1.7 Ga, indicating that these granites could be derived from the Proterozoic basement rocks with minor input from mantle-derived magmas. The calculation of Fe3+ and Fe2+ of biotites indicates a low oxygen fugacity condition (log fO2 ranging from 10-17 to 10-18 bars, below MH), which is favorable for the W-Sn mineralization. Tungsten and tin have been enriched in granitic magmas through fractionation, and low oxygen fugacity conditions have promoted the accumulation and transportation of W-Sn in the hydrothermal fluids, leading to deposition of mineral phases. The geochemical data suggest that Piaoac granites formed in an extensional setting related with the Late Cretaceous magmatism occurring large-scale lithospheric extensional in South China Block. [ABSTRACT FROM AUTHOR]

The Truong Son metallogenic belt in central Laos and Vietnam is an important Fe-Cu-Sn-Au polymetallic ore district. The Pha Lek Fe deposit is closely related to Late Carboniferous- Early Permian I-type granitic magmatism, and contains >50 Mt @ 45% to 50% of Fe ore. Ore minerals occur mainly as magnetite and hematite in the skarn alteration zone between a granitic pluton and metamorphosed Middle-Upper Devonian carbonates. The granitic pluton comprises granodiorite and granite, with zircon U-Pb dating indicating synchronous emplacement at 288.2±1.3 and 284.9±1.2 Ma, respectively. Zircons from these granitoids have εHf(t) values of 2.9-11.2 and relatively young TDM2 ages (<1.0 Ga), indicating an origin by partial melting of depleted mafic crust or magma mixing. Previous studies have shown that these granitoids have high Y, Yb, and K2O contents, and low Sr and Na2O contents, which are interpreted as the melting of mafic continental crust. Pyrite of the main mineralization stage yields an 187Re/188Os-187Os/188Os isochron age of 287±17 Ma, indicating that mineralization is associated with Pha Lek granitic magmatism. A Late Carboniferous-Early Permian subduction-related skarn-type Fe mineralization model is proposed for the Pha Lek deposit. More evidence is needed to verify a hypothesis of volcanic overprinting during Late Triassic post-collisional extension. [ABSTRACT FROM AUTHOR]

The metasedimentary Lujiapuzi Formation crops out along the northeastern margin of the North China Craton, close to the Yan‐Liao Rift. The age and tectonic setting of the formation, and its relationship with the Yan‐Liao Rift are currently unclear. Here we present detrital zircon U‐Pb ages, and Hf isotopic and geochemical data for the Lujiapuzi Formation to constrain the timing of deposition, the provenance of the formation, and the regional stratigraphy relationship. Zircon U‐Pb dating constrains the timing of deposition of the Lujiapuzi Formation to younger than 1780 Ma, and indicates that most grains were sourced from the Longgang Block and the Paleoproterozoic Liao‐Ji Belt. Detailed field investigations and a correlation of the regional stratigraphy reveal that much of the Lujiapuzi Formation is equivalent to the Tuanshanzi Formation in the Yan‐Liao Rift; the lower section may represent the earliest sediments deposited within the Fanhe Basin. Based on these results and the findings of previous studies, we suggest that the base of the Changcheng System has an age of 1.80 Ga. Zircon Hf isotopic data indicate that the main period of crustal growth along the northeastern margin of the North China Craton occurred at 3.2–2.5 Ga, with a peak at 2.9–2.7 Ga. [ABSTRACT FROM AUTHOR]

The sedimentary record in the Late Palaeoproterozoic‐Neoproterozoic Bayan Obo rift belt can provide critical insight into tectonic evolution of Columbia and the North China Craton. In this study, we present new U–Pb geochronology, Hf isotopic analyses from the Bayan Obo Group, the Mesoproterozoic kimberlite, and gabbro to constrain the depositional age and potential provenance information of the Bayan Obo Group. We show that the Dulahala‐Jianshan, Bilute, and Baiyinbaolage formations were deposited at ca. 1.81–1.7 Ga, ca. 1.58–1.35 Ga, and ca. 1.25–1.0 Ga, respectively. Our data suggest the following potential provenance for sediments within the Bayan Obo Group: (a) The Khondalite Belt, Yinshan Block, and crystalline basement complex of the North China Craton to the south were the most potential provenance of the Dulahala and Jianshan formations during the initial deposition of Bayan Obo Group; (b) The Yinshan Block, and crystalline basement complex of the North China Craton, and local intermediate‐acid igneous rocks were the most potential provenance of the Bilute Formation; and (c) the local gabbro and volcanic rocks were the most potential provenance of the Baiyinbaolage Formation. Based on regional geologic constraints and the sedimentary history, we propose that the Northern Marginal Rift System probably represented several distinct rifting events. Furthermore, the Bayan Obo and Huade rift belts were active more recently than 1.0 Ga, which suggests that these rift systems were not only related to the rifting of the Columbia supercontinent. We propose that the Bayan Obo rift belt also records the rifting related to the breakup of Rodinia with the deposition of Qingbaikou System (Tonian) strata. [ABSTRACT FROM AUTHOR]

The Geysers Plutonic Complex (GPC) in the California Coast Ranges underlies one of the world's premier geothermal resources. The GPC consists of three major intrusive phases, orthopyroxene-biotite microgranite porphyry, orthopyroxene-biotite granite, and hornblende-biotite-orthopyroxene granodiorite (in sequence of emplacement). These are nearly coeval and compositionally equivalent to lavas of the overlying Cobb Mountain Volcanic Center which includes (from older to younger) rhyolite of Alder Creek, dacite of Cobb Mountain, and dacite of Cobb Valley. Zircon from GPC plutonic and associated volcanic rocks were analyzed at high spatial resolution for their trace element abundances along with oxygen and hafnium isotopic compositions. Pronounced negative Eu anomalies and high incompatible trace element (e.g., Y, Hf, and U) abundances in zircon along with low Ti-in-zircon temperatures reveal that the GPC microgranite porphyry magma was more evolved than GPC granite and granodiorite. Isotopically, GPC microgranite porphyry, granite, and granodiorite zircon crystals closely overlap (δ18O = +4.76 to +9.18; εHf = +1.4 to +10.7), but a subpopulation with elevated δ18O (∼8.05) and lower εHf (∼4.4) is only present in GPC granite and granodiorite. Zircon from coeval volcanic units share this dichotomy, with a dominant population at (δ18O = +4.92 to +9.38; εHf = +3.4 to +11.3) and a generally minor population with elevated δ18O and low εHf, which is particularly prominent in dacite of Cobb Valley. Anticorrelated δ18O and εHf values indicate progressive assimilation of Franciscan Complex basement rocks, but fractional crystallization was decoupled from crustal assimilation. Together with published U-Th-Pb geochronology, these data reveal distinct degrees of crust-mantle interaction and constrain the thermochemical conditions during different stages in the evolution of a composite intrusive body that fed the GPC and contemporaneous volcanoes. A thermal model for such a body emplaced at ∼7 km depth quantitatively matches the GPC zircon age distribution when magma accumulation started at low recharge rates (0.1 km3/ka), intermittently peaked during a brief flare-up (4 km3/ka for 50 ka), and then returned to a low recharge flux (0.1 km3/ka). This model also qualitatively explains the initial presence of small-volume, highly evolved melts forming the microgranite porphyry, followed by massive emplacement of less evolved magmas forming the GPC granite-granodiorite complex. During this second stage, crustal assimilation locally intensified due to prior thermal priming of the country rock. The total injected magma volume into the upper-crustal reservoir between c. 2.1 and 1.1 Ma amounts to ∼300 km3, which is about three to four times the known volume from geothermal well penetration into the GPC. The accumulation of large volumes of silicic magma along the western North American continental margin in the wake of the northward migrating Gorda slab edge thus appears limited to a brief (c. 50 ka) pulse of high magma influx from the mantle that was pre- and post-dated by protracted low-flux magmatism. [ABSTRACT FROM AUTHOR]

Ferroan (A-type) granitoid batholiths typically intrude during the periods of crustal-scale extension either at the terminal phase of an orogenic cycle or in an unrelated ‘anorogenic’ event. Elevated magmatic temperatures coupled with the anhydrous nature of the melts warrants the involvement of the lower crust along with the mantle as material and/or heat source. Granitoid batholiths from the north-eastern part of the Chotanagpur Granite Gneissic Complex (CGGC) show extreme iron enrichment with high alkali and HFSE contents associated with elevated magmatic temperatures (∼900 °C), typical of ferroan (A-type) granites. Whole-rock trace element compositions indicate that the granitoids were dominantly produced by low-pressure anhydrous melting of middle- to lower-crust. U-Pb zircon geochronology constrains the intrusion age of the granitoids to ca. 1450 Ma. Lu-Hf isotopic compositions of the dated zircon indicate a limited contribution of contemporaneous juvenile mantle material; instead point to a dominant involvement of Palaeoproterozoic crustal source. Based on these findings, we suggest that the ferroan (A-type) granitoids occurring in the north-eastern CGGC are the results of melting of Palaeoproterozoic crust, triggered by mantle upwelling and increased heat transfer resulting from crustal extension associated to the fragmentation of the Indian landmass during the breakdown of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

The Pamir Plateau at the western end of the India–Asia collision zone underwent long-term terrane drifting, accretion and collision between early Paleozoic and Mesozoic. However, the detailed evolution of this plateau, in particular, the timing of the Proto- and Palaeo-Tethys ocean subduction and closure, remains enigmatic. Here we report new field observations and zircon U-Pb ages and Hf isotopic compositions of the representative rocks from the so-called Precambrian basement in the northeastern Pamir, i.e., the Bulunkuole Group. The rock associations of the Bulunkuole Group indicate volcano-sedimentary sequences with arc affinities. Geochronological data demonstrate that the deposition age of the Bulunkuole Group in the NE section of the Pamir was Middle to Late Cambrian (530–508 Ma) rather than Paleoproterozoic. The deposition age became progressively younger from south to north. The amphibolite- to granulite facies metamorphism of the Bulunkuole Group took place at ca. 200–180 Ma. Unlike the scenario in the Southern Kunlun terrane (SKT) in the eastern section of the West Kunlun Orogenic Belt (WKOB), early Paleozoic metamorphism (ca. 440 Ma) was absent in this area. Two phases of magmatic intrusions, composed of granites and minor gabbros with arc geochemical signatures, emplaced at 510–480 Ma and 240–200 Ma. The amphibolite (meta mafic sheet? 519 Ma) and the meta-rhyolite (508 Ma) have zircon εHf(t) values of 1.6 to 5.9 and − 1.5 to 1.4, respectively. The 511 Ma gneissic granite sheet and the 486 Ma gabbro have zircon εHf(t) values of − 0.1 to 2.4 and 1.3 to 3.6, respectively. Zircon εHf(t) of the 245 Ma augen gneissic granite sheet varies from − 2.2 to 2.0 whereas the metamorphic zircons from the amphibolite (193 Ma) and high-pressure mafic granulite sample (187 Ma) have negative εHf(t) values of − 5.3 to − 2 and − 15 to − 12, respectively. In line with rock association and the deposition age of the Bulunkuole Group and the Saitula Group in the eastern section of WKOB, we propose that both of them were accretionary wedge between the Tarim and Tianshuihai terrane formed during the Proto-Tethys ocean south- southwestward subduction (present orientation). The timing of deposition and metamorphism documents two distinct phases of arc magmatism and sedimentary basin evolution. This indicates that the Proto-Tethys ocean closed at ca. 440 Ma in the eastern section of WKOB whereas in the western section, a remnant of the Proto-Tethys ocean between the Tarim and the NE Pamir did not close till Late Triassic. This remnant ocean was filled by the Ordovician-Triassic sequences. The accretion between NE Pamir and the Central Pamir was completed by ca. 180 Ma as demonstrated by the metamorphic zircon U-Pb age of the high pressure mafic granulite in the NE Pamir. [ABSTRACT FROM AUTHOR]

Five Hadean (> 4 Ga) aged zircon grains from the Jack Hills metasedimentary belt have been investigated by a secondary ion mass spectrometry scanning ion image technique. This technique has the ability to obtain accurate and precise full U-Pb systematics on a scale < 5 μm, as well as document the spatial distribution of U, Th and Pb. All five of the grains investigated here have complex cathodoluminescence patterns that correlate to different U, Th, and Pb concentration domains. The age determinations for these different chemical zones indicate multiple reworking events that are preserved in each grain and have affected the primary crystalized zircon on the scale of < 10 μm, smaller than conventional ion microprobe spot analyses. In comparison to the spot analyses performed on these grains, these new scanning ion images and age determinations indicate that almost half of the spot analyses have intersected several age and chemical domains in both fractured and unfractured parts of the individual crystals. Some of these unfractured, mixed domain spot analyses have concordant ages that are inaccurate. Thus, if the frequency of spot analyses intersecting mixed domains here is even close to representative of all other studies of the Jack Hills zircon population, it makes the interpretation of any trace element, Hf, or O isotopic data present in the literature tenuous. Lastly, all of the grains analysed here preserve at least two distinguishable 207 Pb/ 206 Pb ages. These ages are preserved in core-rim and/or complex internal textural relationships in unfractured domains. These secondary events took place at ca. 4.3, 4.2, 4.1, 4.0, 3.7, and 2.9 Ga, which are coincident with previously determined statistically robust age peaks present in this zircon population. [ABSTRACT FROM AUTHOR]

The South Qinling Belt in Central China is an important window to investigate the Neoproterozoic tectono-magmatic processes along the northern margin of the Yangtze Block. Here we present whole-rock geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes of a suite of Middle Neoproterozoic intrusion from the Wudang Uplift in South Qinling. Zircon LA-ICP-MS U-Pb ages reveal that these rocks were formed at ca. 705–716 Ma. Geochemical features indicate that the felsic magmatic rocks are I-type granitoids, belong to calcic- to calc-alkaline series, and display marked negative Nb, Ta and Ti anomalies. Moreover, the enrichment of light rare earth elements (LREEs) and large ion lithophile elements (LILEs), combined with depletion of heavy rare earth elements (HREEs) support that these rocks have affinity to typical arc magmatic rocks formed in Andean-type active continental margins. The REE patterns are highly to moderately fractionated, with (La/Yb) N = 5.13–8.10 in meta-granites, and 2.32–2.35 in granodiorite. The granitoids have a wide range of zircon ε Hf (t) values (−29.91 to 14.76) and zircon Hf two-stage model ages (696–3482 Ma). We suggest that the ca. 705–716 Ma granitoids were sourced from different degrees of magma mixing between partial melting of the overlying mantle wedge triggered by hydrous fluids released from subducted materials and crustal melting. The hybrid magmas were emplaced in the shallow crust accompanied by assimilation and fractional crystallization (AFC). Both isotopic and geochemical data suggest that the ca. 705–716 Ma felsic magmatic rocks were formed along a continental arc. These rocks as well as the contemporary A-type granite may mark a transitional tectonic regime from continental arc to rifting, probably related to slab rollback during the oceanic subduction beneath the northern margin of Yangtze Block. [ABSTRACT FROM AUTHOR]

Hf isotope data for zircons and whole-rocks from lower crustal mafic granulite and pyroxenite xenoliths from NW Russia are presented together with the results of U-Pb zircon dating, Sm-Nd and Rb-Sr isotopic compositions of bulk-rocks and minerals, and trace element compositions of minerals. Most zircons preserve a record of only the youngest metamorphic events, but a few Grtgranulite xenoliths retain Archean magmatic zircons from their protolith. Metamorphic zircons have highly variable εHf(t) values from -25 to -4. The least radiogenic zircons were formed by recrystallization of primary magmatic Archean zircons. Zircons with the most radiogenic εHf grew before garnet or were contemporaneous with its formation. Zircons with εHf(t) from -15 to -9 formed by various mechanisms, including recrystallization of pre-existing metamorphic zircons, subsolidus growth in the presence of garnet and exsolution from rutile. They inherited their Hf isotopic composition from clinopyroxene, pargasite, rutile and earlier-formed zircon that had equilibrated with garnet. Subsolidus zircons were formed in response to a major change in mineral association (i.e. garnet- and zircon-producing reactions including partial melting). Recrystallized zircons date the onset of high-temperature conditions without a major change in mineral association. Age data for metamorphic zircons fall into five groups: >1.91 Ga, 1.81-1.86 Ga, 1.74-1.77 Ga, 1.64-1.67 Ga and <1.6 Ga. Most ages correlate with metamorphic events in the regional upper crust superimposed onto rocks of the Belomorian belt during formation of the Lapland Granulite Belt. Zircon formation and resetting at 1.64-1.67 Ga significantly postdates Lapland-Kola orogenic events and may relate to the onset of Mesoproterozoic rifting. The youngest ages (1.6-1.3 Ga) correspond to an event that affected only a few grains in some samples and can be explained by interaction with a localized fluid. The observed garnet-granulite associations were formed at 1.83 Ga in Arkhangelsk xenoliths and 1.74-1.76 Ga in most Kola xenoliths. By the end of the Lapland-Kola orogeny, the rocks were already assembled in the lower crust. However, no addition of juvenile material has been detected and preservation of pre-Lapland-Kola metamorphic zircon indicates that some xenoliths represent an older lower crust. Granulites, pyroxenites and Phl-rich rocks have a common metamorphic history since at least c. 1.75 Ga. At about 1.64 Ga metasomatic introduction of phlogopite took place; however, this was only one of several phlogopite-forming events in the lower crust. [ABSTRACT FROM AUTHOR]

We report the results of combined U-Pb and Lu-Hf isotope analyses of detrital and metamorphic zircon grains from a variety of metavolcano-sedimentary rocks of the Dwalile Supracrustal Suite (DSS) from the ca. 3.66 to 3.20 Ga Ancient Gneiss Complex (AGC) in Swaziland. The results indicate that the DSS is made up by Palaeo- and Mesoarchaean rocks which have been affected by a polymetamorphic overprint and became tectonically assembled during the Neoarchaean. The oldest Dwalile rocks were formed during a phase of felsic to intermediate volcanism at ca. 3.46 Ga, and are derived from the same magma source as the Tsawela Gneisses. Based on the combined U-Pb-Hf isotope data, two groups of metasedimentary rocks can be distinguished: an older Dwalile Group I that is similar in age to the Hooggenoeg and Kromberg Formations (3.46–3.40 Ga), but with a different source area. A younger Dwalile Group II is coeval with the Fig Tree and possibly Moodies Groups (<3.23 Ga) and the data suggest there was a similar provenance. The U-Pb-Hf isotope data and petrological observations demonstrate that the DSS was affected by three stages of metamorphic overprint: an event at 3.23 Ga, pervasive amphibolite-facies metamorphism at 3.15 Ga, and low-P granulite-facies metamorphism at 2.99 Ga. Metamorphic zircon in the amphibolite-facies rocks resulted from new growth in aqueous fluids at 3.15 Ga, whereas in the granulite-facies rocks new zircon was formed in the presence of melt. The 3.23 Ga event coincides with the last significant metamorphic overprint documented in the Barberton Greenstone Belt (BGB), whereas as two younger events are restricted to the AGC. The data support the model suggesting amalgamation between the AGC and BGB terranes at ca. 3.23 Ga. In addition, they require crustal thickening in the AGC terrane at ca. 3.15 Ga, causing Barrovian-type metamorphism in the DSS and granulite-facies metamorphism in the Luboya-Kubuta Terrane. Low-P granulite-facies metamorphism at ca. 2.99 Ga is most likely related to crustal extension during the onset of Pongola Basin rifting, causing mantle upwelling, mafic magmatism, and heat transfer from the mantle into the thinned crust. [ABSTRACT FROM AUTHOR]

U–Pb and Hf isotopic data from metasedimentary and magmatic rocks from the Windmill Islands in Wilkes Land, East Antarctica, confirm age and crustal evolution links between the Albany–Fraser Orogen and this part of East Antarctica. Detrital zircon age data indicate that the protoliths to the metasedimentary rocks of the Windmill Islands have maximum depositional ages of c. 1350 Ma. Metamorphic zircon growth at c. 1300 Ma and a crystallisation age of c. 1315 Ma for the protoliths to an orthogneiss that intrudes the metasedimentary rocks provide a minimum depositional age. Significant detrital zircon age components are identified at 1790 Ma, 1595 Ma and 1390 Ma. The 1350–1300 Ma depositional interval and the detrital age components suggest that the Windmill Islands metasedimentary rocks can be linked to metasedimentary rocks of the Arid Basin in the Albany–Fraser Orogen. The sediment sources were likely to be the West Australian Craton as well as a significant component from the c. 1410 Ma Loongana Arc in the Madura Province. This combination of sources suggests a back-arc setting for the Arid Basin, consistent with the short interval between deposition and high thermal gradient metamorphism. The magmatic rocks in the Windmill Islands have intrusive ages of c. 1315 Ma, 1250–1210 Ma and 1200–1160 Ma. The first phase of magmatism was likely to be derived from melting of Arid Basin metasedimentary rocks, based on abundant inherited zircon with similar ages to the surrounding metasedimentary rocks. The final two phases of magmatism have juvenile ε Hf (t) values consistent with a greater proportion of mantle melt sources. [ABSTRACT FROM AUTHOR]

Widespread Late Triassic granitoid rocks in the South Qinling Belt (SQB) represent excellent subjects to study the geochemical and geodynamic evolution of magmatic rocks during the collision between the North China Craton and South China Block. In this study, we report new geological, geochemical, zircon U–Pb geochronology and zircon Hf isotopic data for the Dongjiangkou and Zhashui intrusions, two large igneous complexes typical of the SQB. We also summarize published geochemical data of similar granitoid rocks. Our results show that the Dongjiangkou intrusion is composed of ca. 223–214 Ma quartz diorites, tonalites and granodiorites with abundant coeval mafic magmatic enclaves (MME), and the Zhashui intrusion consists of ca. 203–197 Ma monzogranites and K-feldspar granites with rare MME. The Dongjiangkou granitoid rocks are characterized by high K 2 O, MgO, Rb, and Mg# values, but low TiO 2 , Sc, and A/CNK (molar Al 2 O 3 /(CaO + Na 2 O + K 2 O)) values, with εHf(t) values of − 18.1 to − 0.4 and T DM2 (Hf) values of 1141–2117 Ma. We suggest that the Dongjiangkou granitoid rocks are formed by magma mixing between 70%–90% melts derived from partial melting of the Neoproterozoic basement rocks of the SQB and 10%–30% mantle-derived mafic melts with minor involvement of Archean to Paleoproterozoic old basement materials of the SQB. The Zhashui granitoid rocks exhibit high K 2 O, Rb, A/CNK, AMF(Al 2 O 3 /(MgO + FeOT)), Al 2 O 3 /TiO 2 and Rb/Sr values, but low MgO, TiO 2 , Sc, CaO/Na 2 O values, with εHf(t) values of − 3.5 to + 2.3 and T DM2 (Hf) values of 979–1300 Ma, suggesting they are mainly produced by partial melting of Neoproterozoic metamorphic greywackes mixed with minor amounts of mantle-derived melts. The MME are characterized by low SiO 2 , Sr/Y ratio, but high MgO, K 2 O, and Rb contents, with εHf(t) values of − 0.8 to + 4.3 and T DM (Hf) values of 732–905 Ma, suggesting they are produced by partial melting of metasomatized continental lithospheric mantle. A flare-up event is recognized during 225–205 Ma and the lower SiO 2 and Sr/Y of the granitoid rocks during this period indicate prominent involvement of mantle-derived melts mixed with crustal melts. The granitoid rocks with higher SiO 2 and Sr/Y during 225–205 Ma, however, suggest they are formed under a greater pressure than those of previous period (235–225 Ma) granitoid rocks. Few granitoid intrusions are formed after 205 Ma, and they display high SiO 2 with low Sr/Y reflecting that they may be produced by low pressure partial melting of crustal materials or may represent highly fractionated magmas in the upper crust. These geochemical variations show a regular change with their formation ages, reflecting the possible variation in petrogenesis and crustal thickness. We propose that the granitoid rocks may have been formed in a transitional setting from subduction to collision during ca. 235–225 Ma, and a slab break-off event followed during ca. 225–205 Ma. Slab detachment was completed during ca. 205–190 Ma. We propose that no intensive delamination/convective removal of lower crust occurred in the SQB. [ABSTRACT FROM AUTHOR]

In this contribution, the largest porphyry Mo deposit in NE China, Chalukou, is selected to provide insights into the tectonic evolution of NE China. The deposit was considered to be rift-related (or Climax-type) porphyry Mo deposit developed in an extensional setting, while other researchers attributed its formation to the subduction of the Paleo-Pacific Ocean. In view of different granite petrogenesis between rift-type and subduction-type porphyry Mo deposits, geochronological and zircon Lu–Hf isotope studies have been carried out on granitic rocks associated with the Chalukou deposit. Zircon grains from the ore-host monzogranite and ore-causative granite porphyry yield weighted mean 206 Pb/ 238 U ages of 166 ± 2 Ma and 152 ± 2 Ma, with molybdenite samples yielding a Re–Os isochron age of 150 ± 2 Ma, indicating a Jurassic age for both granitic intrusion and Mo mineralization. Zircon εHf(t) values of monzogranite and granite porphyry range from 0.9 to 3.0 and from − 1.4 to 0.5, respectively. When integrated with published zircon Lu–Hf isotopic data, our data suggest that the barren granites (both pre- and post-ore) were mainly derived from mantle-derived juvenile rocks, whereas the syn-ore granite requires additional involvement of old continental crust. Thus, a contribution of continental crust to Mo mineralization is suggested. The petrogenesis and geochemical data reveal that the Chalukou deposit is a subduction-related porphyry Mo deposits and not rift-related. Integrated evidence links its formation to the southeastward subduction of the Mongol–Okhotsk Ocean, instead of the westward subduction of the Paleo–Pacific Ocean. [ABSTRACT FROM AUTHOR]

In recent years, a number of Mo deposits have been discovered in the Dabie region of the Qinling-Dabie orogenic belt. These deposits have a genetic relationship with Late Jurassic to Early Cretaceous granites. In this study, we present a geochemical and geochronologic study on the recently found Huangjiagou Mo deposit, which is the first Mo deposit found in Hubei Province from the Dabie region. The Huangjiagou deposit is currently under exploration, and a middle-sized Mo deposit with 100,000 t of proven Mo metal reserves has already been reached. Mo mineralization mainly occurs as small quartz-molybdenite veins and disseminations within the country rocks next to the Huangjiagou granite. Re-Os isotope dating of molybdenites from the ore veins yields an age of 137.0 ± 8.1 Ma, which is consistent with the LA-ICP-MS zircon U-Pb age of the Huangjiagou granite (137.6 ± 1.6 Ma), suggesting a coeval and causative relation between the granite and mineralization. Geochemical analysis indicates that the Huangjiagou granite is high-K calc-alkalic to shoshonitic and weakly peraluminous with relatively low Mg contents. The rocks are enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs). The (La/Yb) N ratios vary from 24.39 to 40.37, and no significant Eu anomalies occur for these samples. The rocks also show enrichment in large ion lithophile elements (LILEs, e.g., Pb, Ba) and depletion in high-field-strength elements (HFSEs, e.g., Nb, Ti). The Hf isotopic compositions of zircons from the granite indicate ε Hf(t) variations from − 17.3 to − 22.1 (average − 19.8 ± 0.5) with two-stage model ages (T DM2 ) from 2.26 to 2.56 Ga (average 2.42 Ga). These geochemical and isotopic features imply that the Huangjiagou granite was likely derived from partial melting of a thickened lower crust that mainly contained garnet and clinopyroxene without feldspar. The abundance of Re in the molybdenites also indicates that the Mo may be derived from the thickened crust with possible minor mantle material mixing. Considering all of the available data for the Mo deposits and related granites in the entire Dabie region, the Mesozoic Mo mineralization can be divided into two stages. The early-stage Mo mineralization (> 130 Ma) is mainly related to granites that resulted from partial melting of the thickened lower crust (including eclogite) with few mantle components added, whereas the late-stage Mo mineralization (< 130 Ma) is related predominantly to continental crust melts, as eclogite had already been removed at ca. 130 Ma in the region. [ABSTRACT FROM AUTHOR]

The Great Hingan Range is located in the eastern sector of the Central Asia Orogenic Belt, and is the second important Mo province in China, next to the Qinling–Dabie orogenic belt. Previous studies concluded that all the Mo deposits (Mo-only or Mo-dominated polymetallic) in the area were formed in the Mesozoic, and related either to the syn- to post-collisional setting following the closure of the Paleo-Asia Ocean, or to the westward subduction of the Pacific plate. However, the fluids forming the giant Diyanqin'amu porphyry Mo deposit in the area disagree with the features of collision-type Mo deposits, but accord with those of the subduction- or continental arc-type. The Mo mineralization is hosted in the Late Jurassic volcanic rocks and genetically related to the buried porphyritic granite and aplitic granite. Two porphyritic granite samples yield LA-ICP-MS zircon weighted mean 206 Pb/ 238 U ages of 158.7 ± 0.8 Ma (MSWD = 0.64, 2σ) and 158.0 ± 0.9 Ma (MSWD = 0.38, 2σ), respectively. The aplitic granite yields a zircon U–Pb weighted mean 206 Pb/ 238 U age of 156.9 ± 1.1 Ma (MSWD = 0.48, 2σ), slightly younger than the porphyritic granite. Seven molybdenite samples from the ores yield Re–Os isotope ages of 156.1 ± 2.2 to 158.1 ± 4.3 Ma. These ages constrain that the Diyanqin'amu Mo system was formed in the period of 159–156 Ma. The granites at the deposit have high contents of SiO 2 , K 2 O and Al 2 O 3 , and low contents of TiO 2 , MgO and CaO, showing a peraluminous high-K calc-alkaline affinity. These granites and the host volcanic rocks are characterized by enrichment of K, Rb, U, Pb, Th and LREE, and depletion of Nb, Ta, Ti and HREE, with negative Eu anomaly, which are similar to magmatic rocks in the Andean arc. Zircon grains from the granites show positive ε Hf ( t ) values of 4.2–9.0, with T DM2 (Hf) ages of 0.63–0.94 Ga. These geochemical data imply that the granites at Diyanqin'amu are highly fractionated I-type, formed in a continental arc generated by the southeastward subduction of the Mongol–Okhotsk oceanic plate. [ABSTRACT FROM AUTHOR]

In this article, we document a detailed analytical characterisation of zircon M127, a homogeneous 12.7 carat gemstone from Ratnapura, Sri Lanka. Zircon M127 has TIMS-determined mean U-Pb radiogenic isotopic ratios of 0.084743 ± 0.000027 for 206Pb/238U and 0.67676 ± 0.00023 for 207Pb/235U (weighted means, 2s uncertainties). Its 206Pb/238U age of 524.36 ± 0.16 Ma (95% confidence uncertainty) is concordant within the uncertainties of decay constants. The δ18O value (determined by laser fluorination) is 8.26 ± 0.06႐ VSMOW (2s), and the mean 176Hf/177Hf ratio (determined by solution ICP-MS) is 0.282396 ± 0.000004 (2s). The SIMS-determined δ7Li value is -0.6 ± 0.9႐ (2s), with a mean mass fraction of 1.0 ± 0.1 μg g-1 Li (2s). Zircon M127 contains ~ 923 μg g-1 U. The moderate degree of radiation damage corresponds well with the time-integrated self-irradiation dose of 1.82 × 1018 alpha events per gram. This observation, and the (U-Th)/He age of 426 ± 7 Ma (2s), which is typical of unheated Sri Lankan zircon, enable us to exclude any thermal treatment. Zircon M127 is proposed as a reference material for the determination of zircon U-Pb ages by means of SIMS in combination with hafnium and stable isotope (oxygen and potentially also lithium) determination. [ABSTRACT FROM AUTHOR]

A giant Permian alkaline magmatic belt has recently been identified in southern Inner Mongolia, along the northern margin of the North China Craton (NCC). This belt is mainly composed of syenite, quartz syenite, alkaline granite and mafic microgranular enclaves (MME)-bearing granodiorite. In order to study the petrogenesis and tectonic implications of these rocks, we undertook zircon U–Pb dating and geochemical analysis of two Permian alkaline plutons. The first Guangxingyuan Pluton occurs in the Hexigten area and is composed of MME-bearing tonalite, K-feldspar granite and syenite. The second Durenwuliji Pluton, located in the Xianghuangqi area, comprises syenite, quartz syenite and K-feldspar granite. Zircon U–Pb dating on tonalite, K-feldspar granite, syenite and quartz syenite from the two plutons yielded a tight range of ages from 259 to 267 Ma. The peralkaline-alkaline rocks show high abundance of total alkalis (K 2 O + Na 2 O = 7.9–12.9%) and K 2 O contents (3.9–8.0%), enrichment in large ion lithophile elements (LILE) and light rare earth element (LREE), and depletion of high field strength elements (HFSE). The associated tonalite and MMEs display I-type granitic geochemical affinity, with less total abundance of trace elements than the peralkaline-alkaline rocks. Zircon Hf isotopic analysis of the Guangxingyuan pluton yielded a large range of ε Hf ( t ) values from − 15.5 to + 6.7 and model ages (T DM C ) from 781 to 2012 Ma. By contrast, the Hf isotopic data of the Durenwuliji pluton shows a small range of ε Hf ( t ) from + 6.2 to + 8.9 and T DM C from 667 to 816 Ma. The geochemical and Hf isotopic characteristics indicate that the parental magma was derived from a mixing of metasomatic mantle-derived mafic magma with different amount of crust-derived felsic magma, and followed by fractional crystallization. Considering previous tectonic studies in Inner Mongolia, a Permian post-orogenic extension was proposed to account for these peralkaline-alkaline intrusions following the amalgamation of NCC and its northern blocks in the southeastern part of Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The Yuhai porphyry Cu–Mo deposit is located in the eastern Tianshan orogenic belt of the southern Central Asian Orogen Belt, being an economically important porphyry Cu deposit in NW China. The deposit comprises sixteen buried orebodies that are predominantly associated with dioritic and granodioritic intrusions and are structurally controlled by roughly NE-trending faults. LA-ICP-MS zircon U–Pb dating yielded crystallization ages of 441.6 ± 2.5 Ma (MSWD = 0.03, n = 24) for diorite and 430.4 ± 2.9 Ma (MSWD = 0.04, n = 19) and 430.3 ± 2.6 Ma (MSWD = 0.09, n = 24) for granodiorite. In situ zircon Hf isotope data on a diorite sample show ε Hf (t) values from + 8.7 to + 18.6, and two granodiorite samples exhibit similar ε Hf (t) values from + 12.6 to + 19.6 and + 12.6 to + 18.9, respectively. The dioritic and granodioritic intrusions belong to a low-K tholeiite series and are relatively enriched in large ion lithophile elements (K, Ba, Pb, and Sr) and are depleted in high field strength elements (Th, Nb, Ta, and Ti). Moreover, these intrusions have high SiO 2 , Al 2 O 3 and MgO contents, low Na 2 O, P 2 O 5 and TiO 2 contents, low Nb/Ta ratios, and slightly positive Eu anomalies. Re–Os dating of molybdenite intergrowth with chalcopyrite yielded a well-constrained 187 Re– 187 Os isochron age of 351.7 ± 2.9 Ma (MSWD = 1.5) with a weighted average age of 355.7 ± 2.4 Ma (MSWD = 0.69) Ma, indicating that the Yuhai Cu–Mo deposit is younger than the intrusion of the diorite and granodiorite. Combined with the regional geological history and above-mentioned data, we suggest that the Yuhai intrusions were most likely derived from the partial melting of mantle components that were previously metasomatized by slab melts formed by the northward subduction of the ancient Tianshan ocean plate beneath the Dananhu–Tousuquan island arc during the Silurian to Carboniferous. Under the subduction-related tectonic setting, the metasomatized mantle magma was emplaced into the shallow crust and induced the formation of the Early Carboniferous Yuhai Cu–Mo deposit, and the hydrothermal fluids of enriched sulfides probably played an important role in the Cu–Mo mineralization. [ABSTRACT FROM AUTHOR]

The southern Peninsular India preserves a number of Archean cratonic nuclei among which the Coorg Block is considered to represent a Mesoarchean microcontinent. Here we investigate the southern margin of this block where remnants of rare ultramafic rocks in association with arc magmatic rocks and accreted metasediments occur in the Wynad region. We present petrology, mineral chemistry, whole rock geochemistry and zircon U–Pb and Lu–Hf data from a suite of meta ultramafics and associated diorite, orthopyroxene-bearing felsic charnockite, and quartz-mica schist. The peak P – T conditions of metamorphism of these rocks are estimated at 720–840 °C and 6.5–8.7 kbar. The geochemical features of the ultramafic suite provide evidence for melting and metasomatism of lithospheric mantle in a suprasubduction zone (SSZ) setting with the involvement of both silicate melts and slab-dehydrated fluids. The parent melts were generated at varying depth levels extending from spinel to garnet stability fields. A subduction-modified, LREE replenished, metasomatically enriched mantle source endorses arc-like chemical signatures in the melts that were acquired through interaction between the depleted sub-arc lithospheric mantle and subduction components. We report the common presence of magmatic zircons in the meta ultramafic rocks with crystallization ages of 3.3–3.0 Ga. Some of these rocks also carry another younger group of magmatic zircons with crystallization ages down to ca. 2.5 Ga. Zircons in the orthopyroxene-bearing felsic charnockite also formed at 3.2–3.0 Ga whereas those in the metadiorite crystallized at around 2.6–2.5 Ga. The detrital zircons in the quartz mica schist show upper intercept age of 3.3 Ga, and lower intercept at 2.5 Ga. The Mesoarchean ages from the Wynad suite are consistent with the ages reported from the Coorg Block, whereas the Neoarchean ages correspond with those in the Nilgiri Block to the south. The Lu–Hf data from zircon grains in the various samples show both negative and positive εHf(t) values ranging from −18.23 to 13.98. The data yield Hf depleted mantle model ages (T DM ) of 2562–3837 Ma and Hf crustal residence model ages ( T DM C ) ranging from 2576 Ma to 4009 Ma, indicating magma derivation from both juvenile and reworked components of Neohadean to early-mid Archean age. Our results reveal a suprasubduction zone mantle wedge that has been repeatedly replenished through multiple events of subduction zone magmatism in the Mesoarchean and Neoarchean. [ABSTRACT FROM AUTHOR]

The closure of the Junggar Ocean between the Central Tianshan and Junggar terranes is essential in understanding the final assembly of the southern Central Asian Orogenic Belt. This study presents new whole-rock geochemical, Sr–Nd and zircon U–Pb–Hf isotopic data for mafic–intermediate intrusions from the Central Tianshan block to provide robust constraints on the final closure of the ocean. LA-ICP-MS U–Pb dating on magmatic-type zircons yields weighted mean 206 Pb/ 238 U ages of ca. 310 Ma and ca. 290 Ma, which are interpreted as the crystallization ages of the intrusions. Petrographic and geochemical analyses of the Late Carboniferous mafic–intermediate rocks, characterized by typical subduction-related signatures, low Sm/Yb (< 2.0) but high Lu/Hf (≥ 0.2) ratios and positive ε Nd (t) (+ 1.2 to + 3.1) and zircon ε Hf (t) (+ 4.1 to + 7.8) values, suggest that their parental magmas were most likely generated by the partial melting of a metasomatized lithospheric mantle wedge in the spinel stability field and emplaced in a continental arc setting. This consideration is consistent with the occurrence of Carboniferous ophiolitic and arc-related granitoids in the region, probably as a result of the southward subduction of the Junggar oceanic plate. In contrast, the Early Permian mafic magmatism exhibits typical within-plate basalt affinities, such as high TiO 2 (2.7–3.2 wt.%) contents, elevated Ti/V (86.0–115.1) and Zr/Y (4.9–9.3) ratios, OIB-like trace element patterns and high ε Nd (t) (+ 1.1 to + 4.5) and zircon ε Hf (t) (+ 3.0 to + 9.8) values. In association with previous investigations, we suggest that their protoliths were most probably derived from the partial melting of an asthenospheric mantle source in the garnet stability field, plausibly induced by asthenosphere upwelling during the slab break-off of the Junggar oceanic plate, which agrees well with the linear distributions of Permian mafic–ultramafic rocks in the Eastern Tianshan. Collectively, our data pinpoint a tectonic transition from oceanic subduction to post-collisional extension during Late Carboniferous to Early Permian time, probably triggered by the closure of the Junggar Ocean and subsequent arc–continent collision between the Central Tianshan and Junggar terranes that gave rise to the final assembly of the Eastern Tianshan. [ABSTRACT FROM AUTHOR]

The Triassic Yidun arc belt (YAB) lies between the Jinshajiang suture zone to the west and the Garzê-Litang suture zone to the east, Eastern Tibetan Plateau. To study the YAB can not only help us to better understand the evolutionary history of the Garzê-Litang Ocean but can also provide some important information to constrain the evolution of the eastern Paleo-Tethys. In this paper, the geochronological and geochemical data of the Ganluogou dioritic complex were systematically investigated in order to decipher the geodynamic setting of the complex and to further determine the final closure time of the Garzê-Litang Ocean. The Ganluogou dioritic complex is located in the northern part of the YAB. It consists of ferrodiorite, diorite and a mixing zone between them and is the largest intermediate-mafic pluton in the YAB. The ferrodiorites were emplaced at 213 ± 2 Ma have low SiO 2 and high Fe 2 O 3 * contents, whereas the diorites formed at 209 ± 2 Ma and have relatively higher SiO 2 , Na 2 O + K 2 O, Th, U, Zr, and Hf contents, but lower Al 2 O 3 , MgO, CaO, Co, and Sr contents than the ferrodiorites. Relative to the primitive mantle both the ferrodiorites and diorites are depleted in Nb and Ta. However, the ferrodiorites exhibit strong depletion in Zr and Hf, whereas the diorites contain relatively higher Th and U contents without negative Zr and Hf anomalies. Both rock-types have similar chondrite-normalized rare earth element patterns with (La/Yb) N ratios = 4.4 to 18.2, and show weak Eu anomalies, with Eu/Eu* of 0.47 to 1. They both show narrow ranges in Sr–Nd–Hf isotopic compositions. However, the ferrodiorites contain lower initial 87 Sr/ 86 Sr ratios (0.7052–0.7057) and relatively higher ε Nd ( t ) values (− 3.8 to − 2.4) than the diorites, which record values of 0.7062–0.7066 and − 5.5 to − 5.7, respectively. For the zircon Hf isotopic composition, the ferrodiorites also exhibit higher 176 Hf/ 177 Hf ratios (0.282738–0.282804) and more depleted ε Hf ( t ) values (3.4–5.6) than those of the diorites ( 176 Hf/ 177 Hf ratios of 0.282690–0.282728 and ε Hf ( t ) values of 1.7–2.8). These geochemical and isotopic features suggest that the ferrodiorites and diorites were derived from the different magma sources. We propose that the ferrodiorites were produced by differentiation of mantle-derived tholeiitic arc magma, whereas the diorites were derived either from dehydration melting of meta-basaltic rocks from the Kangding Complex (the basement of the west Yangtze Craton) or young arc volcanic rocks but mixed with a small amount of sediments. Both ferrodiorites and diorites were emplaced at relatively low pressure (3.3–3.9 kbar) but with quite different magma temperature (ferrodiorites: 821–960 °C; diorites: 692–788 °C). The Ganluogou dioritic complex was therefore formed under an extension setting that was associated with the closure of the Garzê-Litang Ocean. Previous studies on Late Triassic magmatism in the area have shown that there was slab-break off event at ~ 216 Ma. Combined with regional geological background, we conclude that the final closure of the Garzê-Litang segment of the Paleo-Tethys Ocean occurred prior to 216 Ma. [ABSTRACT FROM AUTHOR]

The Northern Liaoning Complex in northeastern China constitutes an important component of the Eastern Block in the North China Craton. The major lithologies consist of Archean granitoid gneisses with minor supracrustal rocks occurring as tectonic lenses. This study presents zircon Lu–Hf isotopic data for the first time as well as new SHRIMP zircon U–Pb data of the major lithologies from the Northern Liaoning Complex, in order to elucidate the crustal evolution of the complex and provide new constraints on the Neoarchean crustal evolution of the Eastern Block in the North China Craton. Magmatic zircon U–Pb data from this study show that the protolith magmas of the supracrustal rocks and granitoid gneisses were generated during ∼2.55–2.50 Ga. Metamorphic zircons document consistent metamorphic ages at 2.49–2.48 Ga, suggesting a regional metamorphic event immediately after the magmatism at the end of the Neoarchean in the Northern Liaoning Complex. Inherited/detrital zircons of 2.79–2.60 Ga suggest possible existence of ancient crust in this region. Zircon Lu–Hf isotopic compositions show that the magmatic zircons have variable ɛ Hf ( t ) values from −4.0 to +9.0 with depleted mantle model ages of 3.6–2.5 Ga, of which most ɛ Hf ( t ) values are positive with a model age peak at 2.9–2.7 Ga. These zircon Hf signatures reveal major juvenile crustal growth with additions of older crustal materials during 2.9–2.7 Ga, and a crustal reworking event with minor juvenile additions at 2.6–2.5 Ga in the studied area. Integrated with previous data from other Neoarchean complexes in the Eastern Block, both the major juvenile crustal growth during 2.9–2.7 Ga and the strong crustal reworking at 2.6–2.5 Ga contribute to the extensive Neoarchean crust formation of the Eastern Block in the North China Craton. The North China Craton share similar Neoarchean continental crustal evolution to other cratons in the world, though it is distinctively featured by intensive tectonothermal overprinting at the end of the Neoarchean. [ABSTRACT FROM AUTHOR]

The Southern Granulite Terrain in India is a collage of crustal blocks ranging in age from Archean to Neoproterozoic. This study investigate the tectonic evolution of one of the northernmost block – the Biligiri Rangan Block (BRB) through a multidisciplinary approach involving field investigation, petrographic studies, LA-ICPMS zircon U–Pb geochronology, Hf isotopic analyses, metamorphic P–T phase diagram computations, and crustal thickness modeling. The garnet bearing quartzofeldspathic gneiss from the central BRB preserve Mesoarchean magmatic zircons with ages between 3207 and 2806 Ma and positive ɛHf value (+2.7) which possibly indicates vestiges of a Mesoarchean primitive continental crust. The occurrence of quartzite-iron formation intercalation as well as ultramafic lenses along the western boundary of the BRB is interpreted to indicate that the Kollegal structural lineament is a possible paleo-suture. Phase diagram computation of a metagabbro from the southwestern periphery of the Kollegal suture zone reveals high-pressure (∼18.5 kbar) and medium-temperature (∼840 °C) metamorphism, likely during eastward subduction of the Western Dharwar oceanic crust beneath the Mesoarchean BRB. In the model presented here, slab subduction, melting and underplating processes generated arc magmatism and subsequent charnockitization within the BRB between ca. 2650 Ma and ca. 2498 Ma. These results thus reveal Meso- to Neoarchean tectonic evolution of the BRB. The spatial variation of crustal thickness, derived from flexure inversion technique, provides additional constraints on the tectonic linkage of the BRB with its surrounding terrains. In conjunction with published data, the Moyar and the Kollegal suture zones are considered to mark the trace of ocean closure along which the Nilgiri and Biligiri Rangan Blocks accreted on to the Western Dharwar Craton. [ABSTRACT FROM AUTHOR]

Zircon U–Pb dating, whole-rock geochemistry, Hf isotopic compositions, and regional geological observations of Jurassic intermediate-acidic intrusions in the Xing’an Block, northeastern China, are presented to constrain their petrogenesis and the tectonic evolution of the Paleo-Pacific Ocean. Zircon U–Pb age dating indicates that the intrusions were emplaced in three stages: during the Early Jurassic (180–177 Ma), Middle Jurassic (171–170 Ma), and Late Jurassic (∼151 Ma). Despite the wide range in ages of the intrusions, the magmas of Jurassic acidic intrusions were likely derived from a similar or common source and experienced different degrees of magmatic differentiation, as inferred from their geochemical and Hf isotopic characteristics. The Jurassic acidic intrusions are characterized by high SiO 2 and total Na 2 O + K 2 O, low MgO, and I-type affinities, suggesting that the primary magmas were derived from partial melting of lower crustal material. These findings, combined with their ε Hf ( t ) values and two-stage model ages, indicate the primary magmas originated from partial melting of juvenile crustal material accreted during the Neoproterozoic to Phanerozoic. The Middle Jurassic intermediate-acidic rocks (diorites and granodiorites of the TJ pluton) have SiO 2 contents of 57.96–69.10 wt.%, MgO contents of 4.48–1.81 wt.%, and high Mg numbers (45–54). They are enriched in large ion lithophile elements (e.g., Rb, Ba, Th, U, and K) and light rare earth elements, depleted in high field strength elements (e.g., Nb, Ta, Zr, Hf, and Ti) and heavy rare earth elements, and have ε Hf ( t ) values of +6.5 to +9.1. These data suggest that the magma was derived from partial melting of a depleted mantle wedge that had been metasomatized by subduction-related fluids. According to these findings and previous studies that focused on contemporaneous magmatic–tectonic activity in northeastern China, we conclude that the generation of Jurassic intermediate-acidic intrusions in the Xing’an Block was related to subduction of the Paleo-Pacific oceanic plate. [ABSTRACT FROM AUTHOR]

The Hongshan quartz monzonite porphyry is one of the Yanshanian intrusions in the southern part of the Yudun Arc. Detailed zircon U-Pb data of four samples yielded ages of 78.8-80.7 Ma, indicating that the Hongshan intrusion was emplaced during the late stage of Late Cretaceous. The Hongshan intrusion shows shoshonitic and high-K calc-alkaline, with A/CNK = 0.64-1.14. The rocks show an obvious fractionation between light and heavy rare-earth elements (average [La/Yb]N = 38.85), with negative Eu anomalies (Eu/Eu* = 0.60-0.87), enrichment in large-ion lithophile elements (Rb, Th, U and K) and depletion in high field-strength elements (Nb, Ta and P). Rocks have high Sr and low Y content which are characteristics of adakitic rocks, suggesting magma derivation from thickened lower crust. In order to evaluate the nature of the source region, Hf isotope data of zircons were acquired through LA-MC-ICPMS. The negative and variable εHf(t) values demonstrate that the Hongshan intrusion was derived from ancient crust, without mantle-derived components and is significantly different from the Triassic intrusions in the southern part of the Yudun Arc. The three Yanshanian intrusions in Hongshan, Relin and Tongchangou are remarkably similar in terms of geochronology, geochemistry and Hf isotopes. We therefore infer that these intrusions had the same magmatic source and we correlate the tectonics with northward subduction of Tethys underneath the Asian continent. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We present zircon ages and Hf-in-zircon isotopic data for plutonic rocks and review the evolution of central Inner Mongolia, China, in the early and late Paleozoic. Zircons of a granodiorite yielded a 206 Pb/ 238 U age of 472 ± 3 Ma that reflects the time of early Paleozoic magmatism. Zircon ages were also obtained for a tonalite (329 ± 3 Ma), quartz-diorite (320 ± 3 Ma), and granite vein (297 ± 2 Ma). Our results, in combination with published zircon ages and geochemical data, document distinct magmatic episodes in central Inner Mongolia. The dated samples are mostly granodiorite, tonalite and quartz-diorite in composition with intermediate to high-silica, high Na 2 O (3.08–4.26 wt.%), low K 2 O (0.89–2.86 wt.%), and high Na 2 O/K 2 O and Sr/Y ratios. Their chondrite-normalized REE patterns are characterized by LREE enrichment. In mantle-normalized multi-element variation diagrams they show typical negative Nb and Ta anomalies, and all samples display positive ε Hf ( t ) and ε Nd ( t ) values, and low I Sr . The Ordovician rocks, however, show higher Sr/Y and La/Yb ratios than the Carboniferous samples, implying that the older granitoids represent adakitic granitoids, and the Carboniferous granitoids are typical subduction-related arc granitoids but also with adakite-like compositions. The results are compatible with the view that the Central Asian Orogenic Belt (CAOB) in Inner Mongolia evolved through operation of several subduction systems with different polarities: an early–middle Paleozoic subduction and accretion system along the northern margin of the North China Craton and the southern margin of the Mongolian terrane, and late Paleozoic northward subduction along the northern orogen and exhumation of a high-pressure metamorphic terrane on the northern margin of the North China Craton. [ABSTRACT FROM AUTHOR]

Supposed pre-Mesozoic igneous and metamorphic rocks from northern Chile are reviewed in the light of twenty-one new SHRIMP U–Pb zircon age determinations. Metamorphic rocks from the precordillera upthrust belt mostly show a wide spectrum of zircon ages, indicating derivation from sedimentary protoliths. Youngest detrital zircon ages (i.e., maximum depositional ages) range from c . 850 Ma at Belén to 1000–1100 Ma in Sierra de Moreno and Cordón de Lila. Late Proterozoic provenance throughout the region corresponds to a c . 1 Ga igneous and metamorphic event. The main source region could have been the Proterozoic MARA block or Laurentia to the west. Early Ordovician plutonic rocks (465–485 Ma) correlated with the Famatinian magmatism of NW Argentina are recognised in all three outcrop areas, and contemporaneous volcanic rocks in Cordón de Lila. Hf- and O-isotope data for Ordovician zircon in these rocks, and for c . 1450 detrital zircon in the metasedimentary rocks, are consistent with ultimate derivation from Early Mesoproterozoic to Paleoproterozoic lithosphere. A depositional age younger than 400 Ma is determined for the Quebrada Aroma metamorphic complex, indicating post-Early Silurian metamorphism and folding. Carboniferous igneous and deformational events occur in the Coast Range, where metasedimentary complexes are mostly related to Late Paleozoic subduction–accretion; deformation and metamorphism continued near the present Pacific shore line until Triassic and earliest Jurassic times. The underlying crust of much of Norte Grande is considered to be Proterozoic (Arequipa–Antofalla block or MARA), although there are no igneous rock outcrops of this age. [ABSTRACT FROM AUTHOR]

Suizhou-Zaoyang area is located in the southern Qinling-Tongbai-Dabie Orogen, China. A combined research on U-Pb ages and Lu-Hf isotopes for detrital zircons from three meta-sedimentary rocks in the Wudang Group is reported. The upper Wudang Group has a major age population of ca. 750 Ma and a sub-major of ca. 860 Ma. But the lower part only yields one age peak at ca. 2.03 Ga. In situ Lu-Hf analyses of the young age group of ca. 750 Ma for zircons from the upper Wudang Group yield an average ɛ( t) value of −8.6 and two-stage Hf model ages ( T) from 1837 to 2230 Ma, respectively. However, zircons from the lower Group give an average ɛ( t) value of 4.5 and T of 2220±22 Ma, close to the timing of zircon crystallization. Thus, it is suggested that, in the study area, the continental crust grew during the middle Paleoproterozoic and reworked during the middle Neoproterozoic, which shows the affinity to the Dabie Orogen. In addition, in the lower Wudang Group, two metamorphic zircon ages of 1992±91 Ma and 1999±61 Ma are consistent with that of the middle Paleoproterozoic metamorphism event in the northern Yangtze Block, which may represent the assemblage of the Columbia Supercontinent. On the basis of the U-Pb ages and Hf isotopes, it is proposed that Suizhou-Zaoyang area was involved in the subduction-collision event in the middle Paleoproterozoic and the Yangtze Block was one of the components of the Paleo-Mesoproterozoic supercontinent. [ABSTRACT FROM AUTHOR]

The Nuvvuagittuq Supracrustal Belt (NSB) in northern Quebec, Canada, represents one of the oldest known crustal fragments preserved in the Earth's crust. Its age has, however, been disputed and different authors present crustal formation ages varying from ca. 3.8 Ga to 4.4 Ga (e.g. O'Neil et al., 2012; Guitreau et al., 2013 ). Here we report new high precision U–Pb geochronological and coupled Lu–Hf isotope data from zircons that reveal the age of the NSB and provide new constraints on the source rocks to this piece of early crust. Two rocks have been analysed, a felsic schist, interpreted to represent a volcanite, and a mylonitic tonalite that is intrusive into the NSB. The felsic schist was emplaced at 3771 + 5 / − 3 Ma , dating the formation of the NSB. The Lu–Hf model age indicates that the parental melt to the felsic schist was extracted from the mantle at this age or within a few tens of million years, but no more than 300 m.y., before its extrusion. This mantle extraction age provides an absolute maximum age for the NSB, but the most probable age of its protocrust is ca. 3.8 Ga. The mylonitic tonalite was emplaced at 3667 + 3 / − 1 Ma . Its Lu–Hf isotopic composition reveals the presence of an older crustal component than that of the NSB, requiring that its precursor melt formed from a Hadean source that was older than the NSB. Based on recent models for Archean TTG formation, we propose that this source represents re-melted Hadean hydrated crust that must have been translated below the NSB at ca. 3667 Ma. [ABSTRACT FROM AUTHOR]

Previous studies have suggested that northwest Cathaysia was a passive continental margin during Neoproterozoic time, given the absence of Neoproterozoic magmatism. However, this view has been challenged by recent discoveries of mafic and felsic magmatic rocks with geochemical affinities to continental arc or back-arc volcanic rocks from the 1.0–0.9 Ga Wuyi–Yunkai belt, indicating the development of an early Neoproterozoic continental margin arc and back-arc system in the Cathaysia block. In this paper we present new age data for the Miaohou and Shanhou arc complexes, demonstrating that the active continental margin of the Cathaysia block lasted until ca. 830 Ma. The Miaohou complex is composed of gabbro, diorite, and granite, the Shanhou complex of diorite and granite, and both complexes are bound by the Jiangshao Fault. Twelve samples from the Miaohou and Shanhou complexes give zircon U–Pb ages of ca. 830 Ma, indicating that the magmatism of the Miaohou and Shanhou complexes were coeval. The Miaohou gabbro has high zircon ɛ Hf ( t ) (+2.8 to +9.6) and whole-rock ɛ Nd ( t ) (+3.9) values together with the geochemical features of volcanic arc basalts, while the Miaohou and Shanhou diorites and granites show large variations and high values of zircon ɛ Hf ( t ) and ɛ Nd ( t ) [ ɛ Nd ( t ) (+1.1 to +5.5) and ɛ Hf ( t ) (−6.1 to +12.3) for the diorites, and ɛ Nd ( t ) (+0.3 to +3.1) and ɛ Hf ( t ) (−3.8 to +11.3) for the granites] together with a similar geochemistry to continental arc felsic rocks (e.g., Cordilleran batholiths). The geochemical and isotopic data suggest that the southeastwards subduction of an oceanic plate under the Cathaysia block caused the dehydration of sediments in the subducted slab, leading to the metasomatism of the mantle wedge by subduction-related fluids, partial melting of the mantle wedge, followed by varying degrees of assimilation and fractional crystallization (AFC) as the magmas ascended. These processes provide a reasonable explanation for the Neoproterozoic arc magmatism on the northwestern margin of the Cathaysia block, represented by the Miaohou and Shanhou complexes. [ABSTRACT FROM AUTHOR]

This paper reports LA–ICP–MS zircon U–Pb ages, geochemical data and zircon Hf isotope compositions of gabbroic rocks, plagiogranites, and granite porphyries exposed at the eastern margin of the Jiamusi Massif in the easternmost segment of the Central Asian Orogenic Belt (CAOB). LA–ICP–MS zircon U–Pb age data indicate that these rocks were emplaced at 290–274, 277, and 110 Ma, respectively. The gabbroic rocks have low- and medium-K tholeiitic compositions, with variable MgO (3.92–12.59%) and low K 2 O (0.12–0.77%) and TiO 2 (0.59–1.37%) contents. They are enriched in large ion lithophile elements (e.g., Rb, Sr), depleted in high field-strength elements (e.g., Nb, Ta), and exhibit positive zircon ε Hf (t) values (3.1–13.8). It is inferred that the primary magmas of these rocks were derived from a depleted lithospheric mantle source that was metasomatized by subducted-slab-derived fluids shortly before their generation. In addition, the Dongfanghong gabbroic rocks have low Sr/Y (7.32–26.2) and (La/Yb) N (0.99–3.02) ratios, and high HREEs, Y, and Sc contents, indicating that the partial melting of lithospheric mantle occurred under relatively low-pressure conditions. The Early Cretaceous granite porphyries are metaluminous medium-K calc-alkaline I-type granites, where the primary magma originated from the partial melting of crustal material. Based on the new geochemical data and regional geological investigations, we propose that the Dongfanghong gabbroic complex and granite porphyry were both formed in an active continental margin setting, the former most likely related to westward subduction of the paleo-oceanic plate beneath the Jiamusi Massif, and the latter associated with westward subduction of the Paleo-Pacific plate beneath the Eurasian continent. The gabbros and the granite porphyries clearly represent two subduction-related crustal accretion events in the eastern part of the Jiamusi Massif since the late Paleozoic. [ABSTRACT FROM AUTHOR]

Widespread granitic intrusions in the northeast part of the Wulonggou area were previously thought to be emplaced into the Palaeoproterozoic Jinshuikou Group during the Neoproterozoic. This contribution presents detailed LA-ICP-MS zircon U–Pb geochronology, major and trace element geochemistry, and zircon Hf isotope systematic on the Wulonggou Granodiorite and Xiaoyakou Granite from the Wulonggou area. Three granodiorite samples yielded U–Pb zircon ages of 247 ± 2, 248 ± 1, and 249 ± 1 Ma, and one granite sample yielded U–Pb zircon age of 246 ± 3 Ma. The granodiorite samples are metaluminous with an alumina saturation index of 0.90–0.96, as well as intermediate- to high-alkali contents of 5.49–6.14 wt.%, and low Zr+Nb+Ce+Y contents, and low Fe2O3T/MgO ratios, which suggest an I-type classical island arc magmatic source. The granite samples are peraluminous with an alumina saturation index of 1.02–1.03, Sr content of 305.00–374.00 ppm, Sr/Y ratios of between 17.68 and 28.77, (La/Yb)Nvalues of 16.98–25.07, low HREEs (Yb = 1.10–2.00 ppm), and low Y (13.00–21.10 ppm), which suggest adakite-like rocks. All granodiorite samples have zirconsεHf(t) values ranging from −2.9 to +3.9, and granite samples have zirconεHf(t) values ranging from −7.8 to +3.2. These Hf isotopic data suggest that the Early Triassic granites were derived from the partial melting of a mafic Mesoproterozoic lower crust, although the degree of ancient crustal assimilation may be higher for the Xiaoyakou Granite. It is suggested here that the ca. 246–248 Ma magma was generated during the northward subduction of the Palaeo-Tethys oceanic plate. [ABSTRACT FROM PUBLISHER]

Neoproterozoic granitic rocks in the Dakendaban Group are widely distributed throughout the Xitieshan area as the old basement in North Qaidam, NW China. The granitic rocks are composed predominantly of K-feldspar, plagioclase, quartz, muscovite and biotite, with subordinate zircon, garnet, titanite and sillimanite. Two granitic rock samples yielded ages of 930 ± 6 Ma and 918 ± 6 Ma using LA-ICPMS zircon U–Pb dating, which are interpreted as the protolith formation age of the granitic rocks, and reflecting an important Neoproterozoic magmatic event in the Xitieshan area. Geochemical data suggest that the granitic rocks are characterized by high SiO 2 , K 2 O, and CaO/Na 2 O ratios (0.48–1.04), with LREE enrichment and strong Eu negative anomalies (Eu/Eu* = 0.44–0.51), and negative anomalies of Nb, Ta, Ti, Zr, and Hf. These rocks have consistent Nd isotope compositions with ɛ Nd ( t ) values ranging from −4.83 to −4.27, while the sample 2011ZJ18-3 yielded the negative ɛ Hf ( t ) values ranging from −6.7 to −1.3, and t DM2 (Hf) model ages ranging from 1.9 to 2.2 Ga. These geochemical and zircon Lu–Hf isotopic features suggest that the granitic rocks in the Xitieshan area belong to the S-type granite, which were mainly derived from the partial melting of the Paleoproterozoic continental crust material (1.9–2.2 Ga) that were predominantly composed of metagreywackes and subordinate metapelitic sources. Based on the regional tectonic reconstruction, we propose that the studied rocks occurred as syn-orogeny on an active continental margin in a compressional environment, which resulted from the Neoproterozoic arc-continent collision and subsequently continent–continent collision, leading to the significant continental growth. The Early Neoproterozoic tectonothermal event in North Qaidam shares many affinities with that of the Tarim block and South China block (Yangtze block) that were associated with the final consolidation of block at the Jinning orogeny, showing an agreement with the formation of Rodinia. The Early Neoproterozoic S-type granitic magmatism in NW China, including the Qaidam and adjacent blocks, is an important episode of continental crust reworking. [ABSTRACT FROM AUTHOR]

In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton (NCC). Our study suggests that the pegmatite dyke likely crystallized from a volatile-rich pegmatitic magma. Different from most other pegmatite elsewhere, zircon from this pegmatite dyke does not contain unusually high U and Th concentrations and suffered no evident radioactive damage, therefore we successfully obtained a zircon U-Pb dating using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), which yields an average Pb/Pb age of 1 814±6 Ma, representing the intrusive age of the granitic pegmatite dyke. Zircon ɛ( t) values are between −8.3 and −3.0, corresponding to Hf depleted mantle model ages from 2 649 to 2 991 Ma with an average of 2 881 Ma. These data indicate that this granitic pegmatite dyke may have been derived from partial melting of Meso-Neoarchean metamorphic rocks from the Xiaoqinling basement. Granitic pegmatite magma may have emplaced within the Taihua Group wall rocks during the last stage of the middle to high grade metamorphism. Furthermore, according to the petrographic observation, the 1.81 Ga pegmatite dyke and the 1 800-1 750 Ma Xiong'er Group rocks were not undergone middle to high grade metamorphism, indicating 1.81 Ga as the termination of the latest regional metamorphism in the southern margin of the NCC. [ABSTRACT FROM AUTHOR]

Zircon U–Pb geochronological, geochemical and petrological analyses have been carried out on the Xitian granite emplaced in the middle part of Shi-Hang zone, which is closely related to the economically important Xitian tungsten–tin deposit in Hunan Province, Southeast China. LA-ICP-MS zircon U–Pb dating of two representative samples yielded weighted means 206 Pb/ 238 U age of 151.7 ± 1.2 Ma and 151.8 ± 1.4 Ma. These granites are comprised mainly of K-feldspar, quartz, plagioclase, Fe-rich biotite and minor fluorite, and are characterized by enrichments in Rb, Th, REEs (total REE = 159–351 ppm), and HFSEs (e.g., Zr and Y) but depletions in Ba, Sr, P, Eu and Ti. They are metaluminous to weakly peraluminous and show a clear A-type granite geochemical signature with high SiO 2 (73.44–78.45 wt.%), total alkalis (Na 2 O + K 2 O = 2.89–8.98 wt.%), Fe 2 O 3 ∗ /MgO ratios and low P 2 O 5 , CaO, MgO and TiO 2 contents. In-situ zircon Hf isotope analysis suggests their ε Hf ( t ) values ranging from –7.43 to –14.69. Sr–Nd isotope data show their ε Nd ( t ) values in the range of –9.2 to –7.3, with corresponding T DM2 ages of 1.72–1.56 Ga. These characteristics indicate that the Xitian granite originated from partial melting of metamorphic basement rocks with a certain amount of mantle-derived materials. Combined with previous geochemical and isotopic data, it is derived that mantle–crust interaction was gradually enhanced from the early to late stages of magmatism. The ore-forming materials and fluids of the Xitian W–Sn deposit are mainly produced by the Early Yanshanian granitic magmatism, which is also responsible for the Late Jurassic (ca. 152 Ma) A-type granitic rocks that host the W–Sn polymetallic deposits distributed along the Shi-Hang zone, implying a significant Mesozoic extensional event in Southeast China likely caused by the subduction of the Paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

In situ U–Pb geochronological, Hf isotopic and REE geochemical analyses of detrital zircons from Mesozoic sandstones in central Jiangxi and east Hunan of the South China Block (SCB) are used to provide not only information about crustal evolution process, but more importantly new constraints on sedimentary provenances as well as Mesozoic basin evolutions in central SCB. A total of 417 concordant zircon analyses define five U–Pb age populations at ca. 2.6–2.3 Ga, ca. 2.0–1.7 Ga, ca. 1.0–0.7 Ga, ca. 500–400 Ma and ca. 300–200 Ma. Integrated analyses of zircon U–Pb ages and Hf isotopes of detrital zircons reveal five episodes of juvenile continental crust growth: ca. 2.5 Ga, ca. 1.7 Ga, ca. 850 Ma, ca. 440 Ma and ca. 230 Ma, with all but the ca. 2.5 Ga episode likely represent that of the SCB. None of the three samples from T 3 –J 1 strata showed strong ca. 1850 Ma and ca. 230 Ma peaks suggesting that the T 3 –J 1 sediments probably sourced from the Yangtze Block. In contrast, stronger peaks of ca. 1850 Ma and ca. 250–230 Ma in post-J 1 strata relative to that of T 3 –J 1 strata suggest a dominantly local Cathaysian provenance. In addition, the distinct low εHf(T) values for zircons of ca. 430 Ma from T 3 –J 1 strata in comparison with higher εHf(T) values for that from post-J 1 strata also support aforementioned viewpoint. Such sharp changes between the pre-J 1 and post-J 1 strata coincide with the remarkable change in regional palaeogeography from a broad shallow marine basin in the Late Triassic–Early Jurassic time to a basin-and-range-style province in the Middle Jurassic. The characteristics and time evolution of detrital zircons from the studied area are consistent with the flat-slab subduction model which involves the development of a broad sag basin during the T 3 –J 1 time, and a rapid regional uplift in the Cathaysia Block caused by the reinitiating of normal subduction along the coastal region at ca. 190 Ma. [ABSTRACT FROM AUTHOR]

The diabase dikes intruded the Lower Cretaceous sandstone in the Huicheng Basin are key to understanding the Mesozoic tectonic evolution of the Qinling orogen. LA-ICP-MS zircon U–Pb dating yields a crystallization age of 107 ± 1 Ma for them. The dikes have low contents of SiO 2 (42.46–50.16 wt.%), MgO (3.47–5.59 wt.%) with low Mg # of 49–59, and TiO 2 (1.35–1.63 wt.%), high TFe 2 O 3 (8.15–9.36 wt.%), Al 2 O 3 (14.75–17.23 wt.%) and K 2 O (0.87–3.61 wt.%). Their Ni and Cr contents are in range of 16.8–111 and 45.7–315 ppm, respectively. They are significantly enriched in light rare earth elements and large ion lithophile elements (e.g., Cs, Pb and Ba), and depleted in Rb, K, P, and Ti. The dikes show relatively high whole-rock initial 87 Sr/ 86 Sr ratios (0.7071–0.7079) and negative ε Nd ( t ) values (−1.5 to −4.8) with single-stage Nd model ages of 941–1186 Ma. In addition, they have low zircon ε Hf ( t ) values (−8.6 to +3.5) with single-stage Hf model ages of 674–1117 Ma. Both elemental and isotopic geochemistry suggests that the magma of these dikes has undergone significant crystallization fractionation of olivine and pyroxene but weak crustal contamination during magma evolution. They were derived from partial melting of an enriched lithospheric mantle source. Together with regional geological data, these results suggest that the Qinling orogen experienced an intracontinental extension during the late Early Cretaceous. [ABSTRACT FROM AUTHOR]

Whole-rock geochemical, zircon U-Pb geochronological and Sr-Nd-Hf isotopic data are presented for the Early Cretaceous volcanic rocks from the northern Da Hinggan Mountains. The volcanic rocks generally display high SiO2 (73.19-77.68 wt%) and Na2O+K2O (6.53-8.98 wt%) contents, with enrichment in Rb, Th, U, Pb and LREE, and depletion in Nb, Ta, P and Ti. Three rhyolite samples, one rhyolite porphyry sample, and one volcanic breccia sample yield weighted mean 206pb/238U ages of 135.1±1.2 Ma, 116.5±1.1 Ma, 121.9±1.0 Ma, 118.1±0.9 Ma and 116.9±1.4 Ma, respectively. All these rocks have moderate (87Sr/86Sr)i values of 0.704912 to 0.705896, slightly negative εNd(t) values of -1.4 to -0.1, and positive εHf(t) values of 3.7 to 8. Their zircon Hf and whole-rock Nd isotopic model ages range from 594 to 1024 Ma. These results suggest that the Early Cretaceous volcanic rocks were originated from melting of subducted oceanic crust and associated sediments during the closure of the Mongol-Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

Charnockites (pyroxene-bearing granitoids) of magmatic origin in diverse tectonic settings and ranging in age from Mesoarchean to Cretaceous constitute important components of the continental crust. Here we report charnockites displaying both magnesian and ferroan compositions associated with gabbros from an AMCG (anorthosite–mangerite–charnockite–granite) suite in the North China Craton. The orthopyroxene in the magnesian charnockite is characterized by moderate X Mg of 0.63–0.65 (Wo 1–2 En 62–63 Fs 35–36 ), and low Al 2 O 3 content of 0.59–0.71 wt.%. The magnesian charnockites show medium- to high-K contents, and high Mg# (~ 47–69) similar to that of gabbros, whereas the Mg# of the ferroan charnockites is low (~ 6–28). The ferroan charnockites are alkali-calcic to alkalic, and weakly peralkaline to metaluminous, whereas the magnesian charnockites are calcic to calc-alkalic, and metaluminous. Although magnesian charnockites are in general considered to have formed in subduction setting, the medium- to high-K contents, high Mg# values with a wide range, and the highly negative εHf values of the zircons in these rocks (− 8. 4 to − 13.6), suggest inheritance of the arc signature from the melting of ancient arc-related crustal material. The ferroan charnockites show tholeiitic affinity and define a common differentiation trend with the gabbroic anorthosites and likely represent fractionated end-members with or without crustal interaction in a post-collisional rift setting. We present U–Pb age data from zircon grains on seven samples including two ferroan charnockites, three magnesian charnockites, one gabbroic enclave in magnesian charnockite and one gabbroic anorthosite which show emplacement ages of 1748.8 ± 6.4 Ma, 1747.1 ± 9.5 Ma, 1756.4 ± 7.3 Ma, 1756.7 ± 9.2 Ma, 1731 ± 17 Ma, 1731.6 ± 8.2 Ma and 1746.5 ± 7.3 Ma respectively. The negative εHf values (− 1.2 to − 13.6) of zircon grains from these rocks and the older crustal model ages ranging from Mesoarchean to Paleoproterozoic suggest that the magma sources of these rocks involved the melting of ancient crustal components. The age data suggest that the magmatic suite was emplaced within a relatively short time interval between1.73 and 1.76 Ga, during late Paleoproterozoic, placing the rocks suite in a post-collisional scenario, following the amalgamation between the Eastern and Western Blocks of the North China Craton along the Trans-North China Orogen at ca. 1.85–1.80 Ga. [ABSTRACT FROM AUTHOR]

Large-scale volcanism in the late Mesozoic was a prominent geological event in southeast China. The late Mesozoic volcanic sequences, named the Moshishan Group, are exposed in Zhejiang Province and are predominantly felsic in composition with subordinate mafic magma and rare andesites. To understand the late Mesozoic tectonic evolution of southeast China, we present zircon U–Pb dating, major and trace element analyses, and Hf isotopic compositions from felsic volcanic rocks of the Moshishan Group. Zircon U–Pb dating shows that the Moshishan Group formed between 145 and 129 Ma. The εHf(t) of the analysed zircons ranges from −16.58 to +6.89, and theTDM2age ranges from 753 to 2238 Ma with a major peak at ca. 1870 Ma. Hf isotopic compositions of zircons in Early Cretaceous volcanic rocks are more radiogenic than that of the metamorphic basement rocks, indicating a juvenile component in these magmas. Major element concentrations show that the volcanic rocks mainly belong to the high-K calc-alkaline series. Both zircon saturation temperatures and the εHf(t) values of zircons gradually increased with the evolution of the magma. Trace element data indicates that neither magmatic differentiation of mantle-derived magma nor mixing of magmas from different sources were the predominant magmagenetic processes. Earlier studies suggest that contemporaneous underplating contributed to the heat source that induced crustal melting and to the material origin that inconsistently mixed with the local crustal melts. Magmatic underplating is likely to have occurred because of the southwestward subduction of the Pacific plate with episodic slab rollback. The data obtained in this study suggest that the crust–mantle interaction under the influence of slab rollback played a progressive role in the formation of Early Cretaceous felsic volcanic rocks in southeast China. [ABSTRACT FROM AUTHOR]

Details on processes of the early-middle Paleozoic Wuyi–Yunkai orogeny in South China remain poorly defined. Most Silurian–Devonian granites in South China are S-type or I-type granites, which are suggested to be petrogenetically related to the Wuyi–Yunkai orogeny. This paper firstly reported a systematic study on two Devonian A-type granites in the central Jiangxi Province. LA-ICP-MS zircon U–Pb dating results imply that the Huitong and Epo granites were emplaced at about 415 Ma. Both of the two granites have the petrographic and geochemical characteristics of A-type granites. Interstitial biotites occur along the boundary of euhedral plagioclase and quartz and they formed later than plagioclase and quartz. It implies that the primary magma could have been anhydrous. Biotites from the two granites are Fe-rich and have high Fe 2 + /(Fe 2 + + Mg 2 + ) ratios (0.60–0.74). The magmatic temperatures estimated from zircon saturation thermometer are 802–920 °C for the two granites, higher than common I-type and S-type granites. The two granites show high contents of total alkalis (Na 2 O + K 2 O = 6.96–9.39 wt.%), high field strength elements (e.g. Zr = 181–437 ppm, Y = 22.1–39.7 ppm, Nb = 18.6–30.3 ppm and Zr + Nb + Ce + Y = 324–555 ppm), rare earth elements (total REE = 155–312 ppm) as well as high Ga/Al ratios (10,000 × Ga/Al = 2.50–3.44). These geochemical characteristics are similar to those of A-type granites. The Huitong and Epo granites have relatively low ε Nd (t) values of − 10.4 to − 7.7, and low zircon ε Hf (t) values (peak value of − 8.0). Whole-rock two stage Nd isotopic model ages and zircon Hf isotopic model ages mostly vary from 1.78 Ga to 2.00 Ga. According to these data, we suggest that the two granites might have derived from partial melting of pre-Cambrian sedimentary rocks which had been granulitized during an earlier thermal event. The two granites contain abundant contemporaneous mafic microgranular enclaves (MMEs). The MMEs display igneous textures and contain acicular apatites, suggesting quenching of mafic magmas that have co-mingled with the host granites. The MMEs might have derived from the enriched lithospheric mantle source. This study on the Devonian Huitong and Epo A-type granites, together with previous studies on Paleozoic granites in South China, indicated that the Wuyi–Yunkai orogeny in South China had changed from syn-collisional crustal thickening to post-collisional extension at least from 415 Ma. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Luming and Xulaojiugou deposits form a porphyry-skarn metallogenic system. [•] Early Jurassic is an important mineralization epoch in the Lesser Xing’an Range. [•] The primary magmas were derived from melting of a metasomatized depleted mantle. [•] The early Jurassic magmatism were related to subduction of the Paleo-Pacific Plate. [Copyright &y& Elsevier]

Highlights: [•] The granitic gneisses from Wuyi-Yunkai yield zircon U–Pb age of 913–982Ma. [•] The early Neoproterozoic S-type granitic magmatism is identified in Cathaysia. [•] They originated from the metapelitic and metaigneous source with little input of juvenile materials. [•] They are petrogenetically related to the closure of the Wuyi-Yunkai arc-back-arc system. [•] The arc-basin system is finally closed at ∼920Ma and the SCB is placed to the Rodinia margin. [ABSTRACT FROM AUTHOR]

Three distinct S-type peraluminous granitoid types have been identified within the Variscan Montes de Toledo batholith, located in the Central Iberian Zone (SW European Variscides): type-1, extremely high peraluminous restite-rich granitoids; type-2, highly peraluminous restite-bearing granitoids; and type-3, moderately peraluminous granitoids with mafic microgranular enclaves. Type-1 and type-2 granitoids are restricted to the western part of the batholith, whereas type-3 granites are mostly restricted to the eastern segment. There is a sequential youngering of emplacement age from type-1 (late-tectonic) to type-2 and type-3 granitoids (post-tectonic), extending the timing of the batholith formation for about 19Ma between 316 and 297Ma. Although the degree of peraluminousity of the different series could be related to different partial melting conditions or to the variable entrainment of restitic components (including the peritectic mineral assemblage of the melting reactions), whole-rock geochemical signatures and isotope zircon composition of the peraluminous granitoid types suggest contribution of different crustal sources. There is no evidence for the direct mantle-derived material contribution in the genesis of these peraluminous melts. Type-1 and type-2 granitoids contain mostly Archean to Neoproterozoic inherited zircons, whereas type-3 granites show preferentially Neoproterozoic (up to late Cryogenian) and Ordovician inheritance. The wide range of initial Hf isotope composition, ranging to highly radiogenic values (ƐHf up to +10), of Neoproterozoic zircon inheritances in type-1 and type-2 granitoids suggests derivation from heterogeneous Neoproterozoic metasedimentary sources composed of both juveline and recycled crustal materials, similar in composition to the host Schist–Greywacke Complex metasediments. Trace-element modelling clearly suggests the involvement of metasediments similar to those mentioned from the southern part of the Central Iberian Zone. Nevertheless, the highly negative initial Nd isotopic signature measured in some type-1 granitoids (ƐNd300 up to −9.4) also suggests a contribution of more mature metasedimentary sequences, such as those described in the northern Central Iberian Zone. On the contrary, the high Ca, Na and Sr bulk-rock contents in type-3 granitoids, together with the presence of Ordovician magmatic inherited zircons, and the absence of inheritances older than Cryogenian ages, suggest the involvement of a metaigneous protolith. This conclusion is also supported by the similar mean whole-rock ƐNd300 isotopic values, TDM ages, ƐHf isotope zircon composition and trace-element modelling of type-3 granitoids when compared to data from outcropping augen orthogneisses from Central Spain. The estimated crystallisation temperatures for the granitoids from the Montes de Toledo batholith (750°–880°C) suggest that the partial melting of the crustal protoliths could be induced by the own heat generated by the thickening of a highly radiogenic crust, such is that from central Spain. Our results not only indicate that the implication of metasedimentary and/or metaigneous sources contributes to enhance geochemical and isotopic differences in S-type peraluminous granitoid series in intracontinental orogenic settings, but also fractional crystallisation processes are responsible for the geochemical variability through the evolution of these felsic magmas. [ABSTRACT FROM AUTHOR]

The Yangshan gold deposit, Gansu Province, is the largest gold deposit in China and the best representative of the western Qinling gold province. Granite dykes can be observed in the orefield, of which some are spatially associated with the gold orebodies. Gold mineralization was debated between magmatic hydrothermal and metamorphic hydrothermal models in previous studies due to a shortage of precise isotopic ages of the granite dykes in the orefield. In this contribution, we report in-situ zircon LA-ICP-MS U-Pb ages combined with Hf isotope and REE data. The age of granite dykes is constrained to be 220.2 ± 3.1 Ma, coeval with the regional development of Triassic granitoids, which resulted from the northward subduction of the Mian-Lue oceanic plate. The εHf(t) values of inherited and new zircon grains from the granite dykes show that the granite dykes have a complex source dominated by sediments which were sourced from the North China Craton, Yangtze Craton and Qinling Orogen, and accumulated in a fore-arc setting. The granite dykes were derived from partial melting of the fore-arc sediment prism induced by the fluids sourced from metamorphic devolatilizaiton of the underthrust Mian-Lue oceanic plate. The Yangshan gold deposit was formed at about 190 Ma, some 30 Myr later than the intrusion of the granite dykes, ruling out the possibility that gold mineralization was caused by Triassic granitic magmatism. The Yangshan gold deposit is a transitional system between Carlin- and orogenic-types that resulted from continental collision orogeny, metallogeny and fluid flow. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The Acasta Gneiss Complex (AGC) is a remnant Hadean–Eoarchean terrane composed of strongly deformed polyphase mafic to felsic gneisses which preserve a multi-stage history of magmatic emplacement, inheritance, and subsequent tectono-thermal modifications. The complexities encountered in such an old terrane fragment have been documented in previous geochronological studies of the AGC (e.g. zircon U–Pb, 147Sm–143Nd), and are evident also in its Lu–Hf isotope systematics. Here, we report new Lu–Hf isotope whole-rock measurements which show that some AGC gneisses were severely disturbed by migmatization and associated mineral segregation, while others preserve their Lu–Hf isotope systematics relatively intact with mostly near- to sub-chondritic initial 176Hf/177Hf ratios. Results reveal identifiable Eoarchean and later (Paleoarchean) magmatic events at around 3960Ma and again at 3600Ma, with a major metamorphism of the complex at 3750Ma. The oldest and least disturbed gneisses have a Lu–Hf regression age of 3946±87Ma, in good agreement with U–Pb zircon geochronology. A role of yet older crust (4000–4200Ma) in the formation of the AGC is also evident, but seems not to have influenced to first order the Lu–Hf isotope systematics of the 3960Ma group. The ca. 3960Ma group is proposed to be representative of its mantle source based on the absence of correlation between ε Hf(t) and Ce/Pb. It is further suggested that these two parameters show that the ca. 3600Ma gneisses were sourced in part from a mafic lithology belonging to the 3960Ma group, and that multiple sources (mantle and crust) were involved in AGC formation. The identification of preserved Lu–Hf isotope systematics in AGC gneisses means that complementary geochemical and isotopic studies bearing on the petrogenesis of pre-3900Ma rocks are possible. Despite its history of strong deformation and alteration, carefully selected domains within the AGC carry surviving information about the evolution of the mantle–crust system at the Eoarchean–Hadean boundary. [Copyright &y& Elsevier]

Abstract: Mesozoic intermediate–felsic intrusions are widely distributed in the southern Qiangtang terrane, central Tibet. Zircon U–Pb dating shows that these intrusions formed in two periods in the Jurassic (169–150Ma) and Cretaceous (127–113Ma). They mostly belong to the high-K calc-alkaline series, and show strong enrichments in large ion lithophile elements (e.g., Cs, Rb, and K), depletions in Nb, Ta, and Ti, and negative Ba anomalies on primitive mantle-normalized diagrams. P2O5 contents decrease with increasing SiO2 content, and Th contents increase with increasing Rb content, consistent with the evolution trend of I-type magmas. These intrusions show a wide range of zircon εHf(t) values from −19.4 to 11.2, including in rocks with similar SiO2 contents, suggesting variable contributions from mantle and Qiangtang crustal sources. Fine-grained mafic to intermediate igneous enclaves in Jurassic intrusions have similar zircon U–Pb ages and similar or slightly higher zircon εHf(t) values to the host rocks, suggesting that the enclave magmas were derived from mixed magmas at depth and injected into more evolved magmas in upper crustal magma chambers. Magma mixing is also supported by the wide range of zircon Hf isotopic compositions (εHf(t)=−19.4 to 2.5) from within individual Jurassic and Cretaceous intrusions, and Jurassic enclaves. The Jurassic–Cretaceous magmas likely formed in a continental arc setting during subduction of the Bangong–Nujiang ocean between 170 and 110Ma, and evolved in the upper plate crust by MASH processes. [Copyright &y& Elsevier]