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New zircon reference materials for in situ zircon radiogenic Hf isotope and stable Zr isotopic determinations made by laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) are required due to high data productivity and consequently high reference material consumption rate. This study examines a new natural zircon for Zr isotope ratios by double spike thermal ionisation mass spectrometry (TIMS), and for Hf isotopes by bulk solution nebuliser (SN)‐MC‐ICP‐MS with both Zr and Hf determined by LA‐MC‐ICP‐MS. A total of five zirconium isotope measurements from drilled zircons, determined by TIMS, yield a mean δ94/90ZrIPGP‐Zr value of ‐0.09 ± 0.06‰ (2s). Five and eight hafnium isotope measurements for powders from the drilled zircons and Ban‐1‐4 by SN‐MC‐ICP‐MS, yield mean 176Hf/177Hf ratios of 0.282985 ± 0.000011 (2s) and 0.282982 ± 0.000007 (2s), respectively. The mean δ94/90ZrIPGP‐Zr value and 176Hf/177Hf ratio determined by LA‐MC‐ICP‐MS analyses are ‐0.06 ± 0.09‰ (2s, n = 504) and 0.282985 ± 0.000035 (2s, n = 327), respectively. The isotopic homogeneities suggest that the Ban‐1 zircon is a suitable reference material for microbeam Zr and Hf isotopic measurements. [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]

Graphical abstract Highlights • The Beishan monzogranitic pluton was emplaced at 194.75 ± 0.81 Ma. • Molybdenite Re-Os dating defines an isochron age of 194.0 ± 2.0 Ma. • The Beishan monzogranite was derived from partial melting of juvenile lower crust. • Dongfengbeishan porphyry Mo deposit was related to westward subduction of the paleo-Pacific plate. Abstract The Dongfengbeishan porphyry Mo deposit is located to the southeast of the Lesser Xing'an Range–Zhangguangcai Range metallogenic belt in NE China. LA–ICP–MS zircon U–Pb dating of the Beishan monzogranite yields an age of 194.75 ± 0.81 Ma. Five molybdenite samples define a Re–Os isochron age of 194.0 ± 2.0 Ma, suggesting that mineralization was associated with emplacement of the Beishan monzogranitic pluton. Monzogranite samples are classified as high-K calc-alkaline and are relatively enriched in light rare earth elements, depleted in heavy rare earth elements, Nb, Ba, P, Sr, Ti, and Zr, and yield negative Eu anomalies. These characteristics are interpreted to record fractional crystallization of the parental magmas. Zircon ε Hf (t) values for Beishan monzogranite samples range from +8.2 to +15.9, and two-stage model ages (T DM2) range from 217 to 711 Ma, indicating that the parental magma was produced during partial melting of juvenile lower crust. Combined with previous studies, our data suggest that the Dongfengbeishan porphyry Mo deposit was associated with westward subduction of the paleo-Pacific plate in the Early Jurassic. [ABSTRACT FROM AUTHOR]

U–Pb ages and Hf isotope compositions of zircons from the Chencai complex in Zhejiang Province have been determined to provide constraints on mechanisms of migmatization and tectonic evolution related to the early Palaeozoic orogeny in the Cathaysia Block, South China. Zircons from leucosome samples of migmatites are characterized by nebulous overgrowths enclosing inherited cores or occur as newly formed grains with weak zoning. Five samples gave weighted mean ages ranging from 438±3 Ma to 432±4 Ma, which are interpreted as recording the time of anatexis of a regional tectono-thermal event. Their ε Hf(t) values range from −21.4 to −4.8 (with peak at −11), with corresponding T DM2 ages of 1.73–2.77 Ga (with peak at c. 1.9–2.3 Ga), suggesting that the protoliths formed by reworking of ancient crust evolved from Late Palaeoproterozoic – early Archaean crust–mantle differentiation. The migmatization was spatially and temporally associated with reported 460–435 Ma metamorphism with a clockwise pressure–temperature (P – T) path and was most likely controlled by crustal thickening driven by the early Palaeozoic orogenesis. The T DM2 ages of the Chencai complex are consistent with those of the Wuyi–Yunkai structural belt in the Cathaysia Block, but distinct from those (with peak at 2.7–3.0 Ga) of the Badu complex which lacks early Palaeozoic tectono-thermal records. The data support the suggestion that a postulated geological entity, instead of the east domain (the Badu complex being its main part) of the Cathaysia Block, was probably involved in the early Palaeozoic orogeny. [ABSTRACT FROM AUTHOR]

The eventual docking of an exotic continental mass over the course of a Wilson cycle is marked by intracontinental sites of prograde metamorphism, contractional deformation, and syn- or post-collisional magmatism. This study shows that inherited premagmatic zircon in subsequently emplaced granitoid rocks provides another line of evidence for the collisional orogeny. Following the continental collision between the North and South China Cratons, Jurassic granitoids intruded widely throughout the central Korean Peninsula in association with the subduction of the Paleo-Pacific plate. The latest Early to Middle Jurassic (177–167 Ma) granitoids occur throughout the cratonic Gyeonggi Massif, whereas Early Jurassic (194–184 Ma) granitoids occur locally along the Okcheon Metamorphic Belt to the southeast of the massif. These two spatiotemporal groups differ profoundly in their age patterns and O-Hf isotopic signatures of inherited zircon. The younger group yields a typically North China-like Archean-Paleoproterozoic (mostly 2.5–1.8 Ga) zircon inheritance. In contrast, inherited zircons from the older group exhibit exclusively Neoproterozoic (ca. 0.9–0.7 Ga) and Paleozoic (ca. 0.4 Ga) cluster along with Archean-Paleoproterozoic populations. The exotic feature of the protolith of the older group is further indicated by significantly lower δ 18 O (− 0.9 to + 4.9‰) and positive εHf (+ 3 to + 15) values of the Cryogenian zircon cores. The results of zircon analysis demonstrate that South and North China-like terranes were juxtaposed infracrustally along the southeastern margin of the Gyeonggi Massif during the pre-Jurassic collisional orogeny, and then selectively provided major source material to the older and younger Jurassic granitoids, respectively. [ABSTRACT FROM AUTHOR]

The Anabar shield in northern Siberia is one of the world’s least studied Precambrian areas, and provides a ‘window’ into the crustal basement of the central and northern Siberian craton. We report U-Pb and Hf isotope data for detrital zircons sampled in a profile across its major structural units. They define a U-Pb age range from 1.8 to 3.4 Ga with three main periods: 1.8–2.0 Ga, 2.4–2.8 Ga and 3.0–3.4 Ga. The oldest zircons yield super-chondritic ε Hf (t) implying that the parental magmas of their source rocks were juvenile, i.e. formed from depleted mantle (DM). Thus, the crustal basement of the Anabar shield, and probably the whole central and northern Siberian craton, started to form in the mid-Paleoarchean, and included no recycled crust. Zircons with 2.5–2.7 Ga ages define two ε Hf (t) intervals. One is super-chondritic (+2 to +7) implying juvenile sources, the other is sub-chondritic (−3 to −12) indicative of recycled crust, probably formed at 3.2–3.4 Ga, in magma sources. Nearly all 1.8–2.0 Ga zircons have sub-chondritic ε Hf (t) (−2 to −29) implying derivation from sources dominated by recycled crust formed at ∼2.6 Ga and ∼3.4 Ga and little or no juvenile addition. These events accompanied amalgamation of the entire craton by welding of Archean domains. The Bekelekh unit of the Daldyn series has the highest proportion of ∼2.6 Ga zircons and may be the oldest ‘nucleus’ of the Anabar shield, whereas the Kilegur unit of the same series is essentially Proterozoic (1.95 Ga). The largest amount of 3.1–3.4 Ga zircons, as well as common 2.6–2.7 Ga zircons, occur in the Ambardakh unit of the Upper Anabar series. Our data suggest alternation of areas with dominant ages of 1.95 Ga and ∼2.6 Ga, with the younger zircons coming from granites and granulites, and the older ones from gneisses. They show no evidence for significant ages differences for the Anabar and Olenek provinces. The final amalgamation of the entire Siberian craton by welding of Archean blocks, may have taken place at around 1954 ± 6 Ma. [ABSTRACT FROM AUTHOR]

The Archean-Paleoproterozoic high-grade basement of Yudongzi complex is a key to understanding the early Precambrian crustal evolution of the Yangtze craton. It comprises mainly orthogneiss, paragneiss and amphibolite, whose protoliths are tonalitic-trondhjemitic-granitic (TTG), sedimentary and basic-intermediate volcanic rocks, respectively. The TTG gneiss, amphibole plagiogneiss and biotite plagiogneiss yield magmatic zircon LA-ICP-MS U–Pb ages of 2815 ± 18 Ma (MSWD = 0.92), 2692 ± 26 Ma (MSWD = 0.59) and 2449 ± 4 Ma (MSWD = 0.94), respectively. Metamorphic overgrowths on zircon from amphibolite have an age of 1848 ± 5 Ma (MSWD = 0.71). TTG gneisses show medium Sr/Y and variable high (La/Yb) N ratios with low Y and Yb contents. They are characterized by positive Eu anomaly and distinct depletion of HREE together with negative Nb, Ta and Ti, implying amphibole, garnet and minor rutile as residual phases. Their positive ε Hf (t) values of +2.1 to +8.1 with T DM2 of ca. 2.80–3.10 Ga suggest significant reworking of juvenile crust. Amphibole plagiogneisses display a strong enrichment of LREEs and depletion of Nb, Ta and Ti. Additionally, a relative enrichment of Ba, Rb, Pb and Zr, as well as high Cr and Ni contents and Mg # values, imply a mantle source with the addition of continental crust material. Zircon ε Hf (t) values vary between −0.9 and +3.9, suggesting a proportionally significant input of juvenile material and therefore interaction between the mantle and pre-existing continental crust. Biotite plagiogneisses show negative ε Hf (t) values between −3.4 and −0.1 with a few positive ε Hf (t) values ranging from +0.1 to +1.5. Together with T DM2 ages of ca. 2.80–3.00 Ga, these ε Hf (t) values suggest that these rocks were mainly generated by reworking of ancient crust. Thus, the Yudongzi complex exposed in the northern part of the Yangtze craton has experienced significant reworking of juvenile crust at ca. 2.80 Ga and subsequent crustal growth at ca. 2.70 Ga, followed by a second stage of reworking of ancient crust at ca. 2.45 Ga. During the Late Paleoproterozoic, the Yudongzi complex was probably involved in the amalgamation of the Paleoproterozoic supercontinent Columbia, and affected by a post-collisional metamorphic event at ca.1.85 Ga. [ABSTRACT FROM AUTHOR]

The tectonic setting and geodynamic model of the Greater Khingan Range (GKR) is highly controversial due to the lack of reliable geological, isotopic and geochronological evidence. In the current study, the Hailesitai pluton, located at the west of the suture between the northern and southern GKR in the east of the Central Asian Orogenic Belt, is selected to address this issue. These granites of the high potassium calc-alkaline series belong to the A1-type granites with typical geochemical characteristics including high contents of Al2O3, extremely low contents of Ti, P, enriched LREE, LILE, depleted HFSE, and a medium Eu negative anomaly. Laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) zircon U−Pb dating indicates that the granites can be divided into two stages: c. 152 and c. 161 Ma. The intrusion of A1-type granites at ~161 Ma implies that intra-plate orogenesis of the northern GKR started at c. 161 Ma at latest. The Hailesitai pluton has relatively homogeneous Hf isotope compositions with a εHf (t) value (+6.0 − +9.0), and two-stage depleted mantle model ages of 579−738 Ma show that the original magma is a mixture of juvenile and crustal source rocks. Extensional collapse of the Mongol−Okhotsk belt between the Siberia block and the northern GKR resulted in the formation of late Jurassic A1-type granites in the northern GKR. The Hailesitai pluton formed in response to post-orogenic extensional collapse of the Mongol–Okhotsk belt, coupled with back-arc extension related to Palaeo-Pacific plate subduction. [ABSTRACT FROM AUTHOR]

The Baoshan Cu-polymetallic deposit is a recently discovered skarn deposit in the northern Lesser Xing’an Range, NE China. The orebodies are mainly hosted in the contact zone between granitic intrusions and Lower Cambrian dolomitic crystalline limestones or skarns. We present here zircon U–Pb and molybdenite Re–Os age data, whole-rock geochemistry, and zircon Hf isotopic data to constrain the geodynamic mechanisms of igneous activity and metallogenesis within the Baoshan Cu–polymetallic deposit. LA–ICP–MS zircon U–Pb dating suggests that a hornblende–quartz monzonite and porphyritic biotite granite were emplaced at 252.45 ± 0.70 Ma and 251.10 ± 0.98 Ma, respectively. Molybdenite separated from ore-bearing quartz veins or skarn-type ores yields a weighted mean model age of 250.3 ± 3.4 Ma, which coincide with the emplacement of the igneous rocks. These data suggest that the Late Permian-Early Triassic magmatic and mineralization event led to the formation of the Baoshan Cu–polymetallic deposit. Granitic intrusions are closely associated with this mineralization and have high contents of SiO 2 (60.90–68.98 wt.%), Al 2 O 3 (15.15–16.98 wt.%) and K 2 O (2.77–4.17 wt.%), with A/CNK ratios of 0.86–0.96. These granites are classified as metaluminous and high-K calc-alkaline I-type granites, and are enriched in Rb, Th, U, and K, and depleted in Nb, Ta, P, and Ti. Moreover, Moreover, the hornblende–quartz monzonite and porphyritic biotite granite have geochemical characteristics similar to adakites and island arc calc-alkaline rocks, respectively. In situ zircon Hf isotope data on the hornblende–quartz monzonite samples show ε Hf (t) values from +0.1 to +3.1, and porphyritic biotite granite samples exhibit heterogeneous ε Hf (t) values from −5.4 to +1.1. The geochemical and isotopic data for the Baoshan intrusions indicate that the Late Permian–Early Triassic continental–continental collision caused over thickening and delamination of the lower crust. Partial melting of delaminated lower crust formed the primary adakitic magmas, which may have reacted with surrounding mantle peridotite during ascent. Hornblende–quartz monzonite was formed by the emplacement of the adakitic magmas, whereas the formation of the porphyritic biotite granite was caused by the mixing of adakitic magmas with ancient crustal materials during ascent. Moreover, ore-forming materials were typically derived from the adakitic magmas with high oxygen fugacity, which incorporated significant amounts of ore-forming elements. Based on the regional geological history and the new geochemical and isotopic data from intrusions, we suggest that diagenesis and mineralization of the Baoshan Cu–polymetallic deposit took place in a transitional tectonic setting from collisional orogeny to extension, after collision of the North China Plate and Songnen Block, during the latter stages of the Xingmeng orogeny. [ABSTRACT FROM AUTHOR]

Combined with the previous detrital zircons U-Pb ages of the two Precambrian successions, i.e. the Shilu Group and the Shihuiding Formation in Hainan Island of South China, the in situ Lu-Hf isotopes of detrital zircons were performed to evaluate the growth and reworking of Hainan Island continental crust during Precambrian. The results of 171 Hf-isotopic analyses on zircon grains from the Shihuiding Formation yield 176 Hf/ 177 Hf ratios between 0.280786 and 0.281188, 176 Lu/ 177 Hf ratios between 0.000228 and 0.003388, Hf model ages (T DM C ) between 3.8 Ga and 1.2 Ga, and ε Hf (t) values ranging from −12.5 to +10.6. The analyzed results of 272 Hf-isotopic data on zircon grains from the Shilu Group exhibit a wide range of 176 Hf/ 177 Hf ratios (0.280810–0.282512), 176 Lu/ 177 Hf ratios (0.000062–0.004060), T DM C ages (3.7 Ga–1.1 Ga), and ε Hf (t) values (−20.5 to +12.3). The continental crust of Hainan Island maybe appeared firstly at ca. 4.0–3.8 Ga and then was reworked. The 91.8% of detrital zircon grains from the Shihuiding Formation and 93.8% of the ones from the Shilu Group have crustal incubation time larger than 300 Ma, indicating an involvement of reworked materials into the sedimentation of both the successions. Unambiguously, the crustal basement rocks in Hainan Island were formed mainly through reworking the previous continental components with minor input of juvenile materials. The generation of juvenile curst in Hainan Island predominantly occurred at ca. 2.7 Ga and ca. 1.5–1.0 Ga, which are consistent with that for the assembly of the Kenorland, and the Columbia breakup and subsequent amalgamation of the Rodinia, respectively. The present study further reveals that the crustal growths in Hainan Island are present at 2.7 Ga, 2.3 Ga and 2.1–1.8 Ga, which is more favorable to the episodic growth mode. Moreover, a rough trend of decreasing maximum crustal incubation time of Hainan Island demonstrates that the incubation time of the juvenile crust is shorter when compared with that of the Cathaysia Block in the late Mesoproterozoic. Link to the previously reported geological works, we consider that Hainan Island did not share the same evolution history with the Cathaysia Block of South China during Precambrian. [ABSTRACT FROM AUTHOR]

This paper summarizes the geochronological, geochemical and zircon Hf isotopic data for Mesozoic granitoids within the Erguna Massif, NE China, and discusses the spatial-temporal variation of zircon Hf isotopic compositions, with the aim of constraining the accretion and reworking processes of continental crust within the Erguna Massif, and shedding light on the crustal evolution of the eastern segment of the Central Asian Orogenic Belt. Based on the zircon U-Pb dating results, the Mesozoic granitic magmatisms within the Erguna Massif can be subdivided into five stages: Early-Middle Triassic (249-237 Ma), Late Triassic (229-201 Ma), Early-Middle Jurassic (199-171 Ma), Late Jurassic (155-149 Ma), and Early Cretaceous (145-125 Ma). The Triassic to Early-Middle Jurassic granitoids are mainly I-type granites and minor adakitic rocks, whereas the Late Jurassic to Early Cretaceous granitoids are mainly A-type granites. This change in magmatism is consistent with the southward subduction of the Mongol-Okhotsk oceanic plate and subsequent collision and crustal thickening, followed by post-collision extension. Zircon Hf isotopic data indicate that crustal accretion of the Erguna Massif occurred in the Mesoproterozoic and Neoproterozoic. Zircon ε( t) values increase gradually over time, whereas two-stage model ( T ) ages decrease throughout the Mesozoic. The latter result indicates a change in the source of granitic magmas from the melting of ancient crust to more juvenile crust. Zircon ε( t) values also exhibit spatial variations, with values decreasing northwards, whereas T ages increase. This pattern suggests that, moving from south to north, there is an increasing component of ancient crustal material within the lower continental crust of the Erguna Massif. Even if at the same latitude, the zircon Hf isotopic compositions are also inconsistent. These results reveal lateral and vertical heterogeneities in the lower continental crust of the Erguna Massif during the Mesozoic, which we use as the basis of a structural and tectonic model for this region. [ABSTRACT FROM AUTHOR]

The Carlos Chagas batholith (CCB) is a very large (~ 14,000 km 2 ) S-type granitic body formed during the syn-collisional stage of the Araçuaí orogen (southeastern Brazil). Zircons extracted from the CCB record a wide range of U–Pb ages (from 825 to 490 Ma), indicating a complex history of inheritance, magmatic crystallization and partial melting during the evolution of the orogeny. Magmatic zircons (ca. 578–588 Ma) are marked by similar Hf isotope compositions and REE patterns to those of inherited cores (ca. 825–600 Ma), indicating that these aspects of the chemical signature of the magmatic zircons have likely been inherited from the source. The U–Pb ages and initial 176 Hf/ 177 Hf ratios from anatectic and metamorphic zircon domains are consistent with a two-stage metamorphic evolution marked by contrasting mechanisms of zircon growth and recrystallization during the orogeny. Ti-in-zircon thermometry is consistent with the findings of previous metamorphic work and indicates that the two metamorphic events in the batholith reached granulite facies conditions (> 800 °C) producing two generations of garnet via fluid-absent partial melting reactions. The oldest metamorphic episode (ca. 570–550 Ma) is recorded by development of thin anatectic overgrowths on older cores and by growth of new anatectic zircon crystals. Both domains have higher initial 176 Hf/ 177 Hf values compared to relict cores and display REE patterns typical of zircon that grew contemporaneously with peritectic garnet through biotite-absent fluid partial melting reactions. Hf isotopic and chemical evidences indicate that a second anatectic episode (ca. 535–500 Ma) is only recorded in parts from the CCB. In these rocks, the growth of new anatectic zircon and/or overgrowths is marked by high initial 176 Hf/ 177 Hf values and also by formation of second generation of garnet, as indicated by petrographic observations and REE patterns. In addition, some rocks contain zircon crystals formed by solid-state recrystallization of pre-existing zircon, which exhibit similar Hf isotope composition to those of inherited/magmatic core domains. The first anatectic event is interpreted as result of crustal thickening after the intrusion of the batholith. This introduced the batholith to a depth in excess of 30 km and produced widespread anatexis throughout the batholith. The second event was associated with asthenospheric upwelling during extensional thinning and gravitational collapse of the orogen, this produced anatexis in parts from the CCB that had been re-fertilized for anatexis by retrogression along shear zones following the first granulite facies event. [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]

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]

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]

As a major Precambrian microcontinent in the southernmost Central Asian Orogenic Belt (CAOB), the Central Tianshan block (CTS) in the Chinese Tianshan is essential for understanding the final assembly of the southern CAOB. It experienced multistage Paleozoic magmatism and metamorphism, but the detailed processes are still controversial and far from being completely understood. This paper reports coupled U–Pb and Lu–Hf isotopic data of detrital zircons from late Paleozoic (meta-)sedimentary strata in the South Tianshan belt, which can provide new insight into deciphering the Paleozoic evolution of the eastern segment of the CTS block. Characterized by typical oscillatory zoning and high Th/U ratios (> 0.2), detrital zircons in the Permian sedimentary samples yield dominant age populations at ca. 505–490 Ma, 475–440 Ma, 430–400 Ma and 340–250 Ma, pinpointing the development of four episodes of magmatism in the eastern CTS block. Particularly, Ordovician–Silurian (475–440 Ma) zircons, possessing low negative ε Hf (t) values, predominate in sedimentary strata in and surrounding the CTS block, indicating that the 475–440 Ma magmatic rocks probably constitute the main body of the CTS block. The origin of this (early Paleozoic) episode of magmatism was most likely related to the southward subduction of the Junggar Ocean beneath the CTS block. Carboniferous–Triassic (340–250 Ma) zircons have dominantly positive ε Hf (t) values, probably derived from the post-collisional juvenile rocks in the CTS block. Combined with previous studies, our data suggest that the single source terrane for the sampled strata was the CTS block, which had been a topographic high providing substantial detritus to the surrounding areas at least since the Early Permian. In the metasedimentary sample, detrital zircons mostly show partially/fully recrystallized internal textures and low Th/U ratios (< 0.2), probably sourced from the amphibolite- to granulite-facies metamorphosed rocks in the eastern CTS block. The youngest zircons suggest that the sampled metasedimentary strata were Carboniferous (341–305 Ma) in age, rather than Neoproterozoic (or Early Sinian in Chinese literatures) as previously interpreted. Based on U–Pb–Hf isotopes and Ti-in-zircon thermometer of metamorphic zircons in this study, as well as previous investigations, we suggest that the eastern CTS block has experienced (a) a 400–370 Ma collisional event, related to the closure of the eastern segment of the South Tianshan Ocean, and (b) a 360–340 Ma extensional event, as a result of post-collisional mantle upwelling. Therefore, the final assembly of the Eastern Tianshan took place during Late Carboniferous time. [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]

The Shuangqing Fe–Pb–Zn–Cu deposit is located in the Xiangride County of Qinghai Province, China, and is a typical example of skarn deposits in the East Kunlun Mountains. Skarnization and mineralization took place along the contact zone between Carboniferous carbonates and the concealed Triassic plagiogranite. LA–ICP–MS U–Pb dating of zircons from the plagiogranite has yielded ages of 227.2 ± 1.0 and 226.54 ± 0.97 Ma, which are interpreted as the emplacement age of the plagiogranite. Molybdenites separated from ore-bearing quartz-veins yielded a Re–Os isochron age of 226.5 ± 5.1 Ma. These age data confirm that both intrusion and related skarn mineralization initiated at ~ 227 Ma. Re contents of molybdenite, zircon ε Hf (t) and 176 Hf/ 177 Hf values fall into the ranges 3.31 to 6.58 μg/g, − 8.6 to − 0.0, and 0.282403 to 0.28263850, respectively. The timing of the Shuangqing Fe–Pb–Zn–Cu mineralization coincided with a major change in the stress field in East Kunlun from transpression to extension, related to the partial melting of thickening crustal materials in a post-collisional tectonic setting. [ABSTRACT FROM AUTHOR]

The Naruo porphyry copper-gold deposit (hereinafter referred to as the Naruo deposit) in Tibet is a potentially ultra-large, typical gold-rich porphyry copper deposit, which was recently discovered in the Bangongco-Nujiang metallogenic belt. This study analyzed U-Pb chronology and Hf isotopes of the ore-bearing granodiorite porphyry in the Naruo deposit using the LA-ICPMS dating technique. The results show that the weighted average age is 124.03±0.94Ma (MSWD=1.7, n=20), and 206Pb/238U isochron age is 126.2±2.7 Ma (MSWD=1.02, n=20), both of which are within the error. The weighted average age represents the crystallization age of the granodiorite porphyry, which indicates that the ore-bearing porphyry in the Naruo deposit area was formed in the Early Cretaceous and further implies that the Neo-tethys Ocean had not been closed before 124 Ma under a typical island-arc subduction environment. The εHf(t) of zircons from the granodiorite porphyry varies from 2.14 to 9.07, with an average of 5.18, and all zircons have εHf(t) values greater than 0; 176Hf/177Hf ratio is relatively high (0.282725-0.282986). Combined with the zircon age-Hf isotope correlation diagram, the aforementioned data indicate that the source reservoir might be a region that is mixed with depleted mantle and ancient crust, which possibly contains more materials sourced from depleted mantle. Rock-forming ages and ore-forming ages of the Duolong ore concentrate area are 120-124 Ma and 118-119 Ma, respectively, which indicate 124-118 Ma represents the main rock-forming and ore-forming stage within the area. The Naruo deposit is located in the north of the Bangongco-Nujiang suture, and it yielded a zircon LA-ICPMS age of 124.03 Ma. This indicates the Bangongco-Nujiang oceanic basin subducted towards the north at about 124 Ma, and the Neo-tethys Ocean had not been closed before the middle Early Cretaceous. It is possible that the crust-mantle mixing formed the series of large and giant porphyry copper-gold deposits in the Bangongco. [ABSTRACT FROM AUTHOR]

The Dongguashan skarn-porphyry Cu-Au deposit, located in the Tongling district of the Middle-Lower Yangtze River Valley metallogenic belt (MLYB), consists of skarn ore bodies in the upper part and porphyry ore bodies in the lower part, both of which are hosted in quartz diorite and quartz monzodiorite. Zircon U-Pb age and geochemical studies show that the quartz diorite of the Dongguashan intrusion formed at 140.3 ± 2.0 Ma (MSWD = 0.19) and belongs to the high potassium calc-alkaline series. It is enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), depleted in high field-strength elements (HFSE) and heavy rare earth elements (HREE), and has a slightly negative Eu anomaly. 176 Hf/ 177 Hf values of the rims of zircons show a variable range (0.282087–0.282391), corresponding with calculated ε Hf ( t ) values of − 10.72 to − 21.46. Plagioclases in the quartz diorite have unbalanced structure characterized by bright andesine and labradorite (An = 37.0–65.5) cores with higher contents of Fe and Sr and are corroded by dark oligoclase (An = 13.8–27.6) rim. Major elements, trace elements, Hf isotope, and the composition of plagioclases indicate that the parental magma of the Dongguashan intrusion was produced by the mixing of underplating mafic magma and felsic magma formed by remelting of Paleoproterozoic and Neoarchean crustal rocks, Neoproterozoic crust may also provide some material to the felsic magma. Mafic magma played a key role and made the parental magma rich in water, sulfur, metals (Cu, Au) and gave it a high oxygen fugacity. During its magmatic evolution, the parental magma underwent fractional crystallization of hornblende, apatite, sphene and other mafic minerals. Some quartz diorite and quartz monzodiorite samples that show adakitic signatures, may result from injection of mafic magma. Some inherited zircons of the quartz diorite in the Dongguashan intrusion gave ages of 2.40–2.50 Ga, 1.95–2.05 Ga and 0.74–0.81 Ga, coming from ultramafic, mafic and andesitic igneous rocks, and this indicates that there may have been three periods (2.4, 2.0, and 0.8 Ga) of magmatic activity in the Tongling district. [ABSTRACT FROM AUTHOR]

New U–Pb age data and Hf isotope systematics on zircons from Middle Devonian and Lower Carboniferous units from NE China provide evidence for the depositional age of these poorly constrained units as well as for the timing of the collision between the Erguna (Ergun in some references) and Xing’an blocks in the eastern end of Central Asian Orogenic Belt (CAOB). The detrital zircons from the Devonian and Carboniferous sandstones yielded similar age spectra in probability diagrams showing three distinct peaks at ∼450 Ma, ∼500 Ma and ∼540 Ma, respectively, along with Proterozoic and Archean age groups, except for a relatively young age population at ∼360 Ma detected for zircons from the Hongshuiquan Fm. The dating results suggest that the depositional time of the Niqiuhe Fm. should be younger than Late Silurian, as indicated by the youngest 422-Ma detrital zircon from this Fm., and that of the Hongshuiguan Fm. with a youngest detrital age of ca. 338 Ma, is younger than Middle Mississippian (Visean), which is in accordance with those inferred from biostratigraphic data. These dominant age groups are widely found in the Erguna and Xing’an blocks, it is suggested that the sediments of the studied sandstones from Niuqiuhe and Hongshuiquan Fms come mainly from the Erguna and Xing’an blocks. The ε Hf ( t ) value of dated zircons from our sandstones has a wide range (−21 to 16), which shows a mixed signature of that from Paleozoic granitoids in Xing’an block (6–17) and Erguna block (−2 to 6), indicating that Erguna and Xing’an blocks had connected before the Middle Devonian deposition of the Niqiuhe Fm. (422 ± 5 Ma). Combined with the age data, we suggest that the Erguna and Xing’an blocks started to accrete at ∼540 Ma, reached the peak of collision at ∼500 Ma, and went into the post-collision stage from ∼490 to ∼450 Ma. The study provides more evidences and constraints for the early Paleozoic evolutions of the inter-continental block amalgamations and accretions in CAOB. [ABSTRACT FROM AUTHOR]

In-situ zircon U–Pb and Hf isotope analyses were carried out for alkaline silicic magmatic rocks from the Phan Si Pan-Tu Le region in northern Vietnam to constrain their possible sources and to determine their petrogenetic relationship with the Emeishan Large Igneous Province (ELIP), SW China. Nine granites and nine rhyolites yield zircon 206 Pb/ 238 U ages from 262 Ma to 249 Ma, coinciding with the timing of silicic magmatism in the Panxi area of the ELIP. The zircon ε Hf ( t ) values (+14 to +3) of these granites and rhyolites suggest a moderately depleted mantle source and overlap with those of peralkaline and metaluminous granites in the Panxi area [i.e. ε Hf ( t ) = +14 to +4]. The zircon Hf isotope ratios show that the zircons probably record the original source characteristics whereas whole-rock Nd isotope data indicate an evidence for crustal contamination that may have occurred at lower temperatures during magma emplacement. The synchroneity, coupled with petrological and geochemical similarities, indicate that silicic rocks from the Phan Si Pan-Tu Le region are cogenetic with the Panxi silicic plutonic rocks and that they are likely derived by similar petrogenetic processes (i.e. fractionation of mafic magmas or partial melting of mafic rocks). Therefore, we propose that the Phan Si Pan-Tu Le region represents a displaced portion of the ELIP inner zone. [ABSTRACT FROM AUTHOR]

Eight Mesozoic sub-volcanic and intrusive rocks in the Lishui Basin have been selected for zircon U-Pb dating and Lu-Hf isotopic analysis. The Laohutou, Datongshan, Daweizhuang, Yeshanao, Yanwaqiao, Xibeishan, Changshantou and Jianshan porphyrites yield concordant early Cretaceous ages of 130.5 ± 1.6 Ma, 136.0 ± 3.4 Ma, 132.7 ± 2.7 Ma, 127.0 ± 1.9 Ma, 129.4 ± 1.7 Ma, 133.2 ± 2.1 Ma, 131.1 ± 2.3 Ma and 127.4 ± 1.8 Ma, respectively. Zircon ε( t) values for these rocks range from −3.54 to −9.11, mostly between −3.54 and −5.93, suggesting sources similar to those for coeval igneous rocks in other volcanic basins along the middle and lower reaches of Yangtze River. Considering the geochemical characteristics of coeval magmatic rocks in the middle and lower reaches of Yangtze River and its adjacent areas, this paper proposes a model of slab rollback to explain the Mesozoic magmatism in the east-central part of China continent. In the middle-late Jurassic to early Cretaceous (170-135 Ma), the Pacific plate started to subduct beneath the Eurasian continent, producing a compressive tectonic setting, and magmatism progressed from coast to the inland. The magmas of this period were derived mostly from partial melting of ancient crust. After ~135 Ma, the subduction weakened, and the rollback of the subducted Pacific plate produced an extensional environment. This led to the formation of volcanic basins, the partial melting of enriched mantle sources and less ancient crust, and the intrusion of voluminous intermediate-mafic igneous rocks. [ABSTRACT FROM AUTHOR]

Cretaceous granites are widespread in the North Dabie orogen, Central China, but their emplacement sequence and mechanism are poorly known. The Tiantangzhai Complex in the North Dabie Complex is the largest Cretaceous granitic suite consisting of six individual intrusions. In this study, zircon U–Pb ages are used to constrain the crystallization and protolith ages of these intrusions. The Shigujian granite is a syn-tectonic intrusion with an age of 141 Ma. This granite was emplaced under a compressional regime. Oscillatory rims of zircons have yielded two peaks at 137±1 Ma and 125±1 Ma. The 137±1 Ma peak represents the beginning of orogenic extension and tectonic collapse, whereas the 125±1 Ma peak represents widespread granitic magmatism. Zircon cores have yielded concordant ages between 812 and 804 Ma, which indicate a crystallization age for the protolith. The Tiantangzhai granites show relatively high Sr contents and high La/Yb and Sr/Y ratios. The Shigujian granite has positive Eu anomalies resulting from partial melting of a plagioclase-rich source in an over-thickened crust. Correspondingly, in situ Lu–Hf analyses from zircons yield high negative εHf(t) values from −24.8 to −26.6, with two-stage Hf model ages from 2748±34 to 2864±40 Ma, suggesting that the magmas were dominantly derived from partial melting of middle to lower crustal rocks. The Dabie orogen underwent pervasive NW–SE extension at the beginning of the early Cretaceous associated with subduction of the Palaeo-Pacific plate beneath eastern China. [ABSTRACT FROM AUTHOR]

In situ detrital zircons U-Pb and Hf isotope analyses from the Min and Jiulong River of Southeast China were carried out to identify sediment provenance and crustal evolution of the northeast Cathaysia Block. Detrital zircons from both rivers displayed similar spectrum peaks at 236, 155, and 110 Ma, but samples from the Min River displayed a distinct Caledonian peak (ca. 460 Ma) and contained more Precambrian particles (ca. 1.8 Ga), which likely stemmed from the upstream area of the Wuyishan terrain. Interestingly, because Taiwan Island cannot supply Caledonian and Paleoproterozoic detrital materials and because the Ou and Jiulong River also lack components from these two populations, it is highly likely that the sediment in the western Taiwan coast partially originates from the Min River. The sediments from the Min River in Fujian are also considered the most likely source of the beach sands of western Taiwan (Chen et al. 2006). However, we stress that the ~1.8 Ga age source in the western Taiwan sediments was found and recognized. Combining U-Pb dating and Hf-isotope suggests that the northeast Cathaysia Block contains some Neoarchean detrital zircons, which derived from the incorporation of juvenile mantle materials and re-melting of ancient crustal substances. The wide ranges of εHf(t) value in the Paleoproterozoic and Neoproterozoic demonstrate the re-melting of ancient crustal materials with minor juvenile mantle materials. Phanerozoic zircons stemmed from re-melting and recycling of Proterozoic crustal materials with or without the invasion of juvenile mantle-derived 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]

Highlights: [•] Northern Madurai Block represents Neoarchean magmatism and protocontinent formation. [•] Occasional presence of Paleoproterozoic zircon rim may indicate metamorphism. [•] Hf isotopes represents mixing of isotopically heterogeneous crustal sources with variable mantle input. [ABSTRACT FROM AUTHOR]

The Huangtuliang monzonitic granite outcrops on the northern side of the Huangtuliang gold mining district, Chicheng, North Hebei Province. Our predecessors only made isotopic age determination using the K-Ar method. Through LA-MC-ICP-MS zircon U-Pb dating and zircon Hf isotopic composition determination, this study acquired the age of 244.8±2.0 Ma (MSWD=0.57) on the basis of the weighed mean Pb/U ratio, indicating that the Huangtuliang monzonitic granite was formed during the Middle Triassic period, which is the product of Early Indosinian magmatic activities in the region of North Hebei. ɛHf( t) values vary relatively evenly, within the range of −10.65-−14.03, with an average of −12.14. The two-stage evolution model ages, tDM2, vary between 1943 and 2144 Ma, implying that the rock-forming materials of the Huangtiliang monzonitic granite mainly came from the Paleoproterozoic recirculated crustal materials, though a small quantity of enriched-mantle materials would have been involved. [ABSTRACT FROM AUTHOR]

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

Abstract: The evolution of the magmatic arc formed along the Asian margin of Neo-Tethys is a key to understand India–Asia convergence. In contrast to the well studied trans-Himalayan magmatic rocks in Tibet, the southeast extension of the arc is still poorly documented in Myanmar, where it is largely buried by sedimentary rocks. This study investigates the magmatic evolution of the western Myanmar arc and the potential along-strike variation of subduction-related magmatism by analyzing U–Pb and Hf isotopes of detrital zircons from the Chindwin Basin in western Myanmar. Our data indicate that the Western Myanmar Arc (WMA) experienced a long-lasting magmatism since the Early Cretaceous, with a main magmatic stage between 110 and 80Ma and a subordinate magmatic stage at ~70–40Ma. Arc-derived detrital zircons yield positive εHf(t) values and young model ages (0.1–1.2Ga), indicating magma generation from a juvenile source. Such geochronologic and geochemical signatures compare well with those of the Kohistan-Ladakh-Gangdese arc in Tibet, indicating uniform magmatic-arc activity all along the Asian margin of Neo-Tethys. [Copyright &y& Elsevier]

Highlights: [•] Two main episodes of magmatism at ∼225Ma and ∼216Ma occurred in the Yidun terrane. [•] Two major episodes of Mesoproterozoic juvenile crust formed in the Yidun terrane. [•] The adakitic magma and ore fluids were not resulted from a common magmatic chamber. [•] The Mesozoic magmatism and Cu mineralization was related to orogenic collapse. [Copyright &y& Elsevier]

The Camamu basin is related to the breakup of Gondwana and belongs to the group of sedimentary basins that are part of the eastern Brazilian passive margin. We have determined the provenance of the precursor sediments by investigating the petrography of fluvial and eolian units from the early-rift Brotas Group and syn-rift Almada Group, coupled to in situ laser ablation MC-ICPMS U–Pb and Lu–Hf isotopic analyses of the detrital zircon grains. Detrital zircon grains from the Sergi Formation, Brotas Group, have a main population of U–Pb ages of 480–600Ma with smaller populations of ages of 900–1000Ma, 1900–2100Ma, 2500–2800Ma and 3000–3200Ma. The Almada Group zircon grains are characterized by a distribution of ages predominantly in the Paleoproterozoic and Archean. The Hf TDM model ages of the Brotas and Almada Group zircon grains range from ca. 1.1 to 4.0Ga, and the εHf(t) values vary from −31.4 to +9.6, providing evidence that some detrital zircon grains in the Camamu Basin were derived from juvenile sources but that the majority have reworked crustal sources or formed from juvenile magmatic rocks that were contaminated by older crustal material. Whole rock Sm–Nd isotope data collected previously are largely consistent with the new U–Pb, Lu–Hf zircon data but do suggest that zircon-poor detritus from the Neoproterozoic to Eopaleozoic Brasiliano Araçuaí-West Congo Belt contributed to particularly the Brotas Group sediments more than would be indicated by the zircon data alone. Thus, integrated petrographic, U–Pb, Lu–Hf zircon and Sm–Nd whole rock studies provide very important clues to the provenance history of the initial sedimentation on Camamu basin passive margin, where the early-rift phase is marked by the input of detritus from the Araçuaí-West Congo belt situated south of the basin, whereas syn-rift sedimentation received major contributions from Paleoproterozoic (Transmazonian cycle) to Archean (Jequié cycle) São Francisco craton units, located to the west. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Xingshan porphyry Mo deposit formed in the Middle Jurassic. [•] The ore-bearing rocks was sourced from the Meso-Neoproterozoic juvenile crust. [•] Its formation was related to the subduction of Paleo-Pacific Ocean. [•] The Jurassic porphyry Mo mineralization regularity in NE China was compared. [ABSTRACT FROM AUTHOR]

Abstract: The late Permian granitoids exposed in the Phan Si Pan zone of northwestern Vietnam consist mainly of the Ye Yen Sun metaluminous granites and the Nam Xe–Tam Duong peralkaline granites. Laser ablation inductively coupled plasma mass spectrometry U–Pb zircon analysis reveals that both the granite suites were emplaced from 253Ma to 251Ma. They have a distinctive A-type geochemistry of high 10,000×Ga/Al ratios of 3.0–5.7 and are also characterized by elevated contents of high field strength elements, A/CNK values of 0.85–1.58, negative Eu-anomalies. Magmatic zircons from the granitoids exhibit positive initial ɛ Hf values ranging from 6.4 to 15.9 and yield single-stage depleted mantle Hf model ages of 257–663Ma. This Hf isotopic feature implies significant contribution of juvenile mantle material to the magmas of the spatially and temporally associated Ye Yen Sun metaluminous and Nam Xe–Tam Duong peralkaline granites. [Copyright &y& Elsevier]

LA-ICPMS zircon U-Pb dating of intrusive rocks from the Shizishan ore field, Tongling, Anhui Province shows that the crystallization ages of Baimangshan pyroxene diorite, Shizishan and Dongguashan quartz diorite are 139±1.9, 138.0±1.7, and 138.4±1.7 Ma, respectively. These three intrusions are high-potassium, alkali-rich, meta-aluminous, and are characterized by enrichment of light rare earth elements and large-ion lithophile elements, depletion of heavy rare-earth elements (HREE) and high field strength elements, and slightly negative Eu anomalies. In-situ Hf analysis of zircon for these three intrusions shows large ranges of Hf isotope compositions: the ɛ( t) values are ɛ( t)= ∼3.3 to ∼14.4 for Baimangshan, ∼14.1 to ∼23.9 Dongguashan, and ∼14.7 to ∼26.9 for Shizishan. The ɛ( t) values of both the Dongguashan and Shizishan quartz diorites are significantly lower than those of Baimangshan pyroxene diorite. Elemental geochemistry and in-situ zircon Hf isotope analyses indicate that the three intrusions were formed through mixing of granitic magma formed by partial melting of the lower crust and water-rich basic magma derived from the enriched lithospheric mantle. The Dongguashan and Shizishan quartz diorites involved greater crustal components than Baimangshan pyroxene diorite. The Dongguashan and Shizishan quartz diorites have geochemical features similar to the adakite, such as high Sr, low Y, and high Sr/Y ratios. Such geochemical features can be attributed to some fractional crystallization of apatite and sphene, and insignificant plagioclase fractional crystallization after magma mixing. These three intrusions are the products of complex crust-mantle interaction during the regional tectonic regime transition from compression to extension. [ABSTRACT FROM AUTHOR]

Abstract: The Dunhuang block, in the easternmost segment of the Tarim craton, exposes Precambrian mafic granulite and felsic gneiss. To better understand the poorly known formation and evolution of the Tarim craton, we carried out detailed field-based petrological and geochronological investigations on the major lithologies of the Dunhuang block. U–Pb dating and Hf isotopic analyses on the mafic granulite and felsic gneiss (TTG gneiss) of the Dunhuang block reveal two distinct age populations: the Latest Neoarchaean (∼2.5Ga) and the Late Palaeoproterozoic (1.82–1.85Ga). The zircon magmatic cores and metamorphic rims of tonalitic gneisses yield similar ages of ∼2.5Ga, supporting the existence of Archean rocks in the Dunhuang block. The short time interval between Latest Neoarchean magmatism and high-grade metamorphism suggests that they were related to the same Latest Neoarchean tectonothermal event. The ∼2.5Ga zircons show Hf-depleted mantle model ages between 2.55Ga and 2.8Ga with a peak at ∼2.7Ga, suggesting that ∼2.7Ga juvenile crust of the Dunhuang block was reworked during a 200–300m.y. period at the end of the Neoarchean. The age of ∼1.85Ga obtained from the mafic granulites and felsic gneisses is interpreted as the age of high-pressure granulite facies metamorphism. Combined with the Hf isotopic data, these data suggest that the Dunhuang block experienced ∼2.7Ga crustal growth, a ∼2.5Ga magmatic–metamorphic event and a 1.82–1.85Ga (HP) granulite facies metamorphic event. This sequence of events is very similar to that of the North China Craton, implying that the evolutionary history of the Dunhuang block was consistent with that of the North China Craton from the Neoarchean to Paleoproterozoic. [Copyright &y& Elsevier]

Abstract: A combined whole-rock geochemical and zircon U–Pb and Lu–Hf isotope study on two Precambrian lithotectonic units in the Songshan area, south-central North China Craton (NCC), was performed to constrain the tectonic evolution of the Trans-North China Orogen (TNCO) during collision between the Eastern and Western Blocks of the NCC. The metamorphic unit at Shipaihe consists of dioritic gneiss with minor amphibolitic enclave, whereas the magmatic unit at Shicheng is composed of granite. Zircon U–Pb dating demonstrate that the dioritic gneiss and enclave amphibolite were originally emplaced contemporaneously at ca. 2.5Ga. The magmatic zircons exhibit ɛ Hf(t) values of 2.2–7.8 and Hf model ages of 2.52–2.73Ga, suggesting that the dioritic gneiss was produced by reworking of the juvenile crust. The magmatic zircons of amphibolite have ɛ Hf(t) values of 0.7–8.1 and Hf model ages of 2.51–2.79Ga. The granite primarily gave zircon U–Pb ages of ca. 1.78Ga, with inherited zircons in ca. 1.87Ga. Zircon Lu–Hf isotopic analyses yield negative ɛ Hf(t) values of −16.7 to −1.8 and Hf model ages of 2.55–3.47Ga, indicating that the granite was mainly derived from reworking of ancient Archean crust. The Neoarchean dioritic gneiss and amphibolite show enrichment of LREE and LILE but depletion of HREE and HFSE, suggesting their derivation from anatexis of juvenile arc-type crust and enriched lithospheric mantle, respectively. The dioritic gneiss also has highly fractionated REE patterns and negligible negative Eu anomalies, implying anatexis at high pressures, where garnet and possibly amphibole as residual phases. The Paleoproterozoic granite has high K2O+Na2O and Zr, high ratios of total FeO/MgO and Ga/Al, and low contents of CaO, Al2O3, Ba, Sr and Eu/Eu* values, consistent with the characteristics of A-type granites. The negative Eu, Ba and Sr anomalies suggest that plagioclase acted as a residual phase during partial melting at relatively low pressures. Taken together, the Songshan metamorphic complex would originally derive from the reworking of juvenile arc-type crust and coeval partial melting of juvenile, enriched lithospheric mantle. Thus, an active continental margin was present in the late Neoarchean in south-central NCC, generating arc-type magmatism between the Eastern and Western Blocks. During the collisional orogeny, the arc-type crust in southern NCC underwent intensive metamorphism that followed by post-collisional extension at ca. 1.78Ga, and the reworking of the old continent in the southern TNCO yield Shicheng A-type granite. [Copyright &y& Elsevier]

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

The Alxa Block is considered part of the North China Craton, but the unambiguous Archean basement has not been reported. In this study, we present the first evidence of the Neoarchean rocks in the Beidashan area of the western Alxa Block. The petrographic and geochemical data show that these rocks are granodiorite with TTG (tonalite-trondhjemite-granodiorite) characteristics. Zircon U-Pb dating gave an age of 2522±30 Ma for the magmatic core and 2496±11 Ma for the metamorphic recrystallized rim. The near-identical age between the Latest Neoarchean magmatism and the high-grade metamorphism shows that these features were related to the same Latest Neoarchean-Earliest Paleoproterozoic tectonothermal event. The age-corrected ɛ( t) value is mainly between 0.4 and 4.9. The two-stage zircon Hf model age ranges from 2.7 to 3.0 Ga, suggesting that the Mesoarchean-Neoarchean (2.7-3.0 Ga) juvenile crust was reworked at the end of the Neoarchean in the western Alxa Block. These data suggest that the western Alxa Block experienced a Mesoarchean-Neoarchean crust growth and Latest Neoarchean-Earliest Paleoproterozoic tectonothermal event similar to the North China Craton. [ABSTRACT FROM AUTHOR]

Zircon U-Pb ages (SHRIMP and LA-ICPMS) and Lu-Hf isotope data (LA-ICPMS) are presented for two granite and two quartzite pebbles from the basal conglomerates of the Sijizhuang Formation in the Hutuo Group from the Wutai Mountains area in the North China Craton. These two granite pebbles give zircon Pb/Pb ages of 2513±8 Ma and 2527±8 Ma respectively, which are consistent with the emplacement ages of the Wangjiahui grey granite and Guangmingsi or Shifo granite in the Wutai Mountains. Detrital zircons from those two quartzite pebbles are mostly 2550-2490 Ma old with lesser number of 2800-2550 Ma grains, which is similar to the ages of detrital zircons from quartzites in the Gaofan Subgroup of the Neoarchean Wutai Group. Thus, the pebbles in the Hutuo Group basal conglomerates were derived locally from Wutai Mountains Neoarchean sources. Zircons from the Sijizhuang Formation conglomerate granite and quartzite pebbles mostly have positive ɛ( t) values, a minority with ɛ( t) values like model depleted mantle (DM) of the same age, but with most showing DM model ages 200-100 Ma. This indicates that most of the source materials were derived from the mantle within the previous 200 million years, whereas some are derived from 2550-2510 Ma juvenile crustal additions. This additional evidence suggests that in the North China Craton there was important initial polycyclic crustal formation and cratonization in the late Neoarchaean, prior to superimposed Palaeoproterozoic orogenic cycles. [ABSTRACT FROM AUTHOR]

The composition of single-grain detrital zircons is an effective provenance indicator of loess, and sheds new light on dust formation and transportation. Here we review the features of detrital zircons and their use as a provenance indicator, including internal structure, trace element, U-Pb age spectrum and Hf isotopic compositions, and present a case study from the Horqin sandy land and its surrounding loess. The loess samples have detrital zircon age peaks in range of 2600-2300, 2100-1600, and 600-100 Ma, of which the 2600-2300 Ma zircon grains mainly have positive ɛ( t) values (−3.4-8.7), the 2100-1600 Ma zircon grains mainly have negative ɛ( t) values (−10.1-6.8), and the 600-100 Ma zircon grains have a variable ɛ( t) values ranging from −21 to 15.9. The detrital zircon signatures of the loess are similar to the Horqin sandy land, but clearly different from the Chinese Loess Plateau and central-western deserts, implying that the loess is transported mainly from the Horqin sandy land in the Last Glacial period. Comparing these with neighboring tectonic units, we found that zircon populations at 2600-2300, 2100-1600, and 600-100 Ma with negative ɛ( t) values may come from the northeast North China Craton (NCC), and those at 600-100 Ma with positive ɛ( t) values may come from the east Central Asian Orogenic Belt (CAOB). It is estimated that the two sources contribute equally to the Horqin sandy land and the surrounding loess. [ABSTRACT FROM AUTHOR]

Abstract: The Luxi and Xiazhuang granitic plutons are parts of the Guidong granite belt in northern Guangdong Province, China. They occur next to each other and have similar crystallization ages. However, the Xiazhuang pluton hosts several important uranium (U) ore deposits, whereas the Luxi pluton does not. This study compares the two plutons using whole-rock geochemistry, biotite compositions, zircon U–Pb ages by LA-ICPMS, and in situ zircon Hf isotope data by LA-MC-ICPMS, to understand the fundamental controls. Results show that the two plutons have similar ages, 237Ma for the Luxi pluton and 234Ma for the Xiazhuang pluton. They also have similar geochemical features that are characteristic of S-type granites. Zircons from both plutons have negative εHf(t) values (−9 to −12) and a Paleoproterozoic two-stage Hf model age (TDM2 =1838Ma to 2025Ma), suggesting that their parental magmas were all derived from Paleoproterozoic metasedimentary rocks. The geochemical and petrological data suggest that these two plutons crystallized from magmas derived from the same parent at different stages, the parental magma of the Xiazhuang pluton is more evolved than that of the Luxi pluton. This factor, plus different physical–chemical conditions (such as temperature, volatile components and oxidation state) resulted in higher U content and favorable U-bearing species in the Xiazhuang magmatic hydrothermal system. U occurs mainly as uraninite in the Xiazhuang pluton, which facilitates U transfer from granite into CO2-rich hydrothermal fluid to form U ore deposits. In contrast, U occurs mainly as REE-bearing minerals in the Luxi magmatic system, preventing U transfer to associated hydrothermal fluids. As a result, the Xiazhuang pluton hosts several important uranium ore deposits, whereas the Luxi pluton is ore-barren. [Copyright &y& Elsevier]

Abstract: Mesozoic magmatism is extensively developed in eastern China along the eastern Asian continental margin, but the geochronological framework is not well understood for each area. In this study, seventy-eight samples were collected from the Mesozoic igneous rocks in south Anhui Province, east-central China, in order to precisely constrain their formation ages and contributions to crustal growth. Zircon U–Pb age determination using ion probe and laser ablation techniques indicate that magmatism in the area can be divided into two separate stages: at 150–136 and 136–120Ma, respectively. The first stage of granitic rocks, not documented in other areas of eastern China, is mostly composed of hornblende-bearing I-type granodiorite and monzogranite, and is considered to be formed by slab-tearing during Pacific subduction. The second stage of magmatism, coeval to that in other areas of eastern China, is characterized by the occurrence of A-type granite and syenite, and their volcanic counterparts, although I-type granitic rocks are also developed locally. These rocks are mostly distributed around and within the fault-controlled volcanic basins, and some are closely related to detachment shearing, indicating their formation in an extensional setting. Zircon Hf isotopic analyses indicate that Archean material might be present in the area, but that the main episode of crustal growth took place during the Mesoproterozoic, with very little juvenile material in the Mesozoic. [Copyright &y& Elsevier]

Abstract: Considerable progress has recently been made regarding temporal and spatial distribution of magmatism in the Lhasa Terrane. However the eastward and southeastward correlation of these Tibetan magmatic suites in western Yunnan and Burma remains poorly constrained. This paper reports zircon U–Pb dating and Hf isotopic compositions of granites in the Gaoligong–Tengliang–Yingjiang area, west Yunnan. It reveals three episodes of plutonism, and more importantly a southwestward magmatic migration. The Gaoligong batholiths in the northeast were mainly emplaced during early Cretaceous (126–121Ma) and comprised predominantly S-type granites with negative zircon εHf values (εHf =−2∼−12). The Tengliang granites, situated southwest of the Gaoligong belt, were emplaced in late Cretaceous (68–76Ma) and also displayed a strong peraluminous affinity and negative εHf (−5∼−14), indicating a provenance from a Proterozoic sedimentary source with little mantle contribution. The youngest phase of magmatism (52–66Ma) occurred in Yingjiang, southwestmost of the study area. It is composed of S-type granites (εHf=−2∼−12) in east Yingjiang and I-type granites (εHf =−4∼+6) in west Yingjiang, near the China–Burma border. The late Cretaceous–early Cenozoic plutons in the Tengliang and Yingjiang area are thus considered as the northern continuation of the late Cretaceous magmatic arc (west), which comprises I-type granites and andesitic rocks, and of the belt of predominant S-type granites (east) in Burma, Thailand and Malaysia. Such a chemical polarity of the dual I-type and S-type granites is strongly reminiscent of the northern American Cordillera, indicating a Cordilleran-style continental margin during the late Cretaceous–early Cenozoic. While the magmatic arc was related to eastward subduction of the Neo-Tethys beneath the Asian continent, the S-type granites represented the melting products of thickened crust in the hinterland, in response to subduction-induced decrease in lithospheric strength and compressive plate-convergence forces and to a less degree to the collision between Burma and Sundaland blocks. The Gaoligong early Cretaceous granites, which bear strong similarities in lithology, geochemistry and emplacement age to those in the northern magmatic belt in the Lhasa Terrane, are also the magmatic expression of crustal thickening. This crustal thickening may have stemmed from the collision between the Lhasa Block and the Qiangtang Block in late Jurassic and Early Cretaceous. The magmatism in western Yunnan thus recorded a long-term subduction of the Neo-Tethyan plate, enhanced by continental collisions at different time. [Copyright &y& Elsevier]

Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district (Cretaceous basin) of the middle-lower Yangtze River polymetallic ore belt, East China. Two types of Late Mesozoic magmatic rocks are exposed: one is dioritic rocks closely related to iron mineralization as the hosted rock, and the other one is granodioritic (-granitic) rocks that cut the ore bodies. To understand the age of the iron mineralization and the ore-forming event, detailed zircon U-Pb dating and Hf isotope measurement were performed on granodioritic stocks in the Washan, Gaocun-Nanshan, Dongshan and Heshangqiao iron deposits in the basin. Four emplacement and crystallization (typically for zircons) ages of granodioritic rocks were measured as 126.1±0.5 Ma, 126.8±0.5 Ma, 127.3±0.5 Ma and 126.3±0.4 Ma, respectively in these four deposits, with the LA-MC-ICP-MS zircon U-Pb method. Based on the above results combined with previous dating, it is inferred that the iron deposits in the Ningwu Cretaceous basin occurred in a very short period of 131-127 Ma. In situ zircon Hf compositions of εHf( t) of the granodiorite are mainly from -3 to -8 and their corresponding 176Hf/177Hf ratio are from 0.28245 to 0.28265, indicating similar characteristics of dioritic rocks in the basin. We infer that granodioritic rocks occurring in the Ningwu ore district have an original relationship with dioritic rocks. These new results provide significant evidence for further study of this ore district so as to understand the ore-forming event in the study area. [ABSTRACT FROM AUTHOR]

Abstract: The Tarim large igneous province (TLIP) in northwestern China, covering an area of ca. 250,000km2, includes large volumes of basalts, basic dyke swarms, mafic-ultramafic intrusion and minor picrite. Here we report systematic Hf isotope data from basalt, diabase, olivine pyroxenite and syenitic porphyry from the TLIP and address the source components and magma evolution. The subdivision of the Tarim basalts shows that the Group 1 and Group 2 basalts are clearly differentiated based on different Nb/Y values, with two subgroups (Group 1a, Group 1b) identified based on distinct P2O5 vs. Mg# trends. The 176Hf/177Hf isotopic composition of the basalts ranges from 0.282584 to 0.282837. The εHf(t) of the basalts belonging to the Group 1a, Group 1b and Group 2 are −0.4–4.4, 0.5–2.1, and 1.9–3.1, respectively, and those of the intrusive suite of olivine pyroxenite, diabase and syenitic porphyry show a range of 6.0–6.5, 4.5–5.7, and 6.5–8.3, respectively. The TLIP basalts generally show a good positive correlation between 176Hf/177Hf and 143Nd/144Nd, and fall in the field of the oceanic island basalts (OIBs) with low 176Hf/177Hf and 143Nd/144Nd, comparable to the basaltic lavas of the Pitcairn hotspot. These features, together with the enriched signature of the Tarim basalts might reflect the incorporation of partial melting of lithospheric mantle source in the early stages of the plume activity. The TLIP basalts show low εNd(t) and moderate εHf(t) OIB-like source. The 176Hf/177Hf-143Nd/144Nd values of the Group 1a and Group 1b basalts of the TLIP basalts are comparable to those from the Karoo high-Ti basalts, and those of the Group 2 basalts are comparable to the features of the Karoo low-Ti basalts and diabases. The Group 1a and Group 1b basalts fall in the same Hf–Nd array, whereas the Group 2 basalts fall in a different array with much higher εNd(t). The olivine pyroxenite, diabase and syenitic porphyry fall in the higher εNd(t) and εHf(t) field, with the olivine pyroxenite and diabase having features close to OIB-like source. Our new Hf isotopic results suggest distinct sources for the Tarim basalts (285–290Ma) and the intrusive rocks (274–284Ma). Furthermore, the εHf(t) vs. εNd(t) plots show that the basalts and intrusive rocks might correspond to two different periods of magmatic activity in the Tarim Basin during the Early Permian, being comparable to the temporal evolution of different rock units in the TLIP. The εHf(t) and εNd(t) combined with other evidences address that the basalts could be explained by being derived from the asthenospheric (or plume) mantle and having interaction with lithospheric mantle source by mainly lower degree of partial melting in the early stage before the eruption, and should be much less proportion of crustal contamination during the period of 285–290Ma, and the intrusive rocks might be derived from the primary magma and/or OIB-like mantle sources and underwent a magma process mainly by fractional crystallization and/or cumulation during the period of 274–284Ma. [Copyright &y& Elsevier]

Abstract: Paleozoic intermediate-acidic volcanic rocks exposed in the northwestern Chinese Altai mainly consist of two different lithologic suites: rhyolite suite (RS) and dacite–rhyolite suite (DRS), which were both assigned to the late Ordovician Dongxileke Formation. Zircon U–Pb dating results demonstrate that the RS suite was formed in the late Ordovician (443±2 and 445±2Ma), while the DRS suite yielded much younger ages (411±4Ma) that are consistent with the early Devonian Kangbutiebao Formation of the Chinese Altai. Zircons from the two suites all have high ε Hf(t) values (mostly +2 to +9), indicating a source dominated by juvenile crustal materials. Rhyolites from the two suites are strongly peraluminous and have high SiO2 (70.53–76.94wt.%) and ε Nd(t) values between −1.7 and −0.6, similar to those of the Paleozoic granitoids (>300Ma) but higher than the Early Paleozoic Habahe sediments, suggesting an origin by partial melting of a juvenile crustal source dominated by meta-igneous rocks. Dacite samples from the DRS suite possess high SiO2 contents (64.71–67.77wt.%) and Mg# values (∼52). They have ε Nd(t) values similar to those of the Habahe sediments, which, in combination with their relative high Th/Yb (>3.5) and low Ba/La (<40) ratios, suggests the dacite was originated from sediment-derived melts modified by depleted mantle peridotite. The Mg-rich dacite formed in a critical period (around 410Ma), during which voluminous granitic intrusions and rhyolite were produced. Extensive partial melting of subducting sediments in the early Devonian is in agreement with a high geothermal gradient in the Chinese Altai. A hot subduction regime is proposed to interpret the early Devonian tectonic evolution of the Chinese Altai. [Copyright &y& Elsevier]

Abstract: Paleozoic granitoid magmatism played an important role in the tectonic evolution of the Chinese Altai, and zircon U–Pb and Hf isotopic compositions have been determined for samples from eleven granitic plutons/batholiths. The Jiadengyu gneissic granitic pluton yielded a zircon U–Pb age of 479Ma, and thus it does not represent Precambrian basement as suggested previously. Our results and published data demonstrate that voluminous granitoids were continuously emplaced over more than 30% area of the Chinese Altai during the period from 447Ma to 368Ma with a climax at ca. 400Ma. Ages for zircon overgrowth rims demonstrate additional thermal events at ca. 360 and 280Ma, respectively. Positive ε Hf(t) values (0 to +9) of normal magmatic zircons suggest that the granitoid magmas were derived from juvenile sources. Xenocrystic zircon cores are 543–421Ma old and also give positive ε Hf(t) values (+2.5 to +12), suggesting their origin as early crystallized minerals in the magma chambers or as inherited cores from newly-accreted meterials. The strong magmatism at ca. 400Ma significantly changed the Hf isotopic composition of the magma source by substantial input of juvenile material in a relatively short period. Geophysical, geological and geochemical data support that ridge subduction was a possible mechanism for the strong magmatism ca. 400Ma and the above mentioned change of Hf isotopic composition in the magma source. [Copyright &y& Elsevier]

Abstract: Porphyry Cu–Mo deposits, related to the Miocene adakitic porphyries from the Gangdese porphyry copper belt in the southern Tibet, formed in a post-collisional setting. Here, we present the new zircon U–Pb ages, whole-rock chemical, and Sr–Nd and zircon Hf isotopic data for the ore-bearing adakitic porphyries from Gangdese porphyry copper belt. LA-ICP-MS zircon dating for six samples yielded ages ranging from 19Ma to 14Ma, indicating they formed in the Miocene. The ore-bearing adakitic porphyries show SiO2 of 61.47–71.67%, K2O of 3.29–4.74%, and high Sr content (394–1106ppm), high Sr/Y ratios (63–158), and low Y (6.12–10.3ppm) and heavy rare earth element contents (e.g. Yb=0.52–0.91ppm). They show steep fractionated REE and flat HREE patterns, and strong enrichment in large ion lithophile elements (Cs, Rb, Ba, Th, and U) and depletion of high field strength elements (Nb), with positive Sr and negative Ti anomalies. There are no linear variations of Ba, La, Sr/Y, Dy/Yb, (87Sr/86Sr)i, and εNd(t) with increasing SiO2 content. Combined with the zircon positive εHf(t) values, and wide range of (87Sr/86Sr)i (0.70559 to 0.70908) and of εNd(t) (−6.8 to 0) values for all the adakitic samples, they were likely derived from the melting of garnet-bearing amphibolite in the juvenile arc mafic lower crust. Additionally, the adakitic porphyries with low Th/Nb ratios have lower initial 87Sr/86Sr, and higher εNd(t) and εHf(t) values, and those with high Th/Nb show higher initial 87Sr/86Sr, and lower εNd(t) and εHf(t) values. This indicates that the juvenile arc lower crust is derived from the melting of the mantle wedge that was metasomatized by slab fluid or sediment melt during the Neotethyan ocean subduction. Significantly, the juvenile arc lower crust possibly inherited the arc magma characteristics of abundant in F, Cl, and Cu and high oxidation state, which contributed to the porphyry Cu–Mo deposits in the Gangdese porphyry copper belt. [Copyright &y& Elsevier]

Abstract: Kimberlite, a deep-sourced ultramafic potassic rock, carries not only diamond, but also invaluable mantle xenoliths and/or xenocrysts, which are important for tracking the evolution of subcontinental lithospheric mantle (SCLM). However, it is challenging to accurately determine the emplacement age of kimberlite and its compositions of primary magma because of modifications by crustal and/or mantle contamination and post-emplacement alteration. This paper reports emplacement ages of diamondiferous kimberlites in Mengyin and Fuxian of the North China Craton (NCC) using three different dating methods. For Mengyin kimberlite, single-grain phlogopite Rb–Sr dating yields an isochron age of 485±4Ma, U–Th–Pb analyses on perovskite give a 238U–206Pb age of 480.6±2.9Ma and a 232Th–208Pb age of 478.9±3.9Ma, and baddeleyite yields a 207Pb–206Pb age of 480.4±3.9Ma. For Fuxian kimberlite, baddeleyite gives a 207Pb–206Pb age of 479.6±3.9Ma, indicating that the Paleozoic kimberlites in the NCC were emplaced at ~480Ma. Numerous lines of evidence indicate that the studied baddeleyites are xenocrysts from the SCLM, and can be used to constrain Hf isotope compositions (ε Hf(t)~−6) of the SCLM when kimberlite erupted. Combined with data from Mesozoic–Cenozoic mantle-derived rocks and xenoliths, the Hf isotope evolution trend of the SCLM beneath NCC before craton destruction was tentatively constructed, which suggested that the Archean SLCM was enriched by metasomatism at ~1.3Ga. Further Hf isotope investigations on additional SCLM-derived materials could be used to compare with the constructed Hf isotope evolution trend before craton destruction to determine when lithospheric thinning occurred. [Copyright &y& Elsevier]