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The Bayan Obo deposit in the Inner Mongolia, North China Craton, is the largest rare-earth element (REE) resource in the world. The deposit is hosted in Mesoproterozoic sediments of the Bayan Obo Group, the lithological sequence of which has been divided into seventeen units (H 1 –H 17 ). The REE mineralization is mainly concentrated in the H8 dolomite unit, and therefore the depositional age of this unit is important in addressing the debate over the genesis of the REE–Fe–Nb ore deposit. Here we present U–Pb and Hf model ages of zircons from the adjacent H9 slate. Our data suggest that the H9 slate formed at 1505 ± 12 Ma and the H8 dolomite was deposited during the Mesoproterozoic. We also present Ar–Ar ages of riebeckite in veins cutting the H8 dolomite and biotite in the ore bodies which show 389.5 ± 3.0 Ma and 289.1 ± 1.8 Ma, respectively. The U–Pb measurements from overgrowth zircon in H9 slate give an age of 518.8 ± 7.5 Ma. These new age data indicate that the Bayan Obo deposit was disturbed during thermal events at 520 Ma to 390 Ma, generating a second phase of REE–Nb mineralization. The δ 7 Li values of the REE mineralized dolomite are similar to those of carbonatite dykes. Combined with ɛ Nd features, we provide geochemical evidences that REE mineralized dolomite has undergone fluid interaction. Results reveal that the carbonatite magmatism occurred within the Bayan Obo rift at ca. 1.2 Ga, provided the primary source for REE–Nb mineralization or to fertilize the Bayan Obo crust, and the later was remobilized during the Caledonian to generate the second phase of mineralization within a convergent plate margin regime. [ABSTRACT FROM AUTHOR]

To constrain sedimentation age of the Myogok Formation and timing of the last episode of the Daebo orogeny, SHRIMP U-Pb age determination and Hf isotopic studies were carried out for the zircon separates. The detrital zircon U-Pb ages of the Myogok Formation show a wide range from Archean to Cretaceous and yield four main clusters at age intervals of 130-150 Ma, 170-220 Ma, 221-320 Ma and Paleoproterozoic. Such age clusters indicate that the main provenance rock types during the sedimentation were basement rocks of the Yeongnam massif and the Mesozoic granitoids distributed around the Myogok Formation. The concordia age of the youngest population is 138.6 ± 2.1 Ma (n = 7), indicating the possible maximum deposition age for the Myogok Formation. Considering the suggestion of probable deposition of Nakdong Formation during the Barremian (Lee et al., 2012), the Valanginian or Hauterivian seems to be the most appropriate timing for the deposition of the Myogok Formation. The last activity of the Daebo orogeny might be constrained to Hauterivian or Barremian considering some time lag needed for basin closure and deformation that followed. The measured ε(t) values from the detrital zircons of the Myogok Formation vary from −25.7 to 4.8. However, most of the zircons, even those with Mesozoic ages, show negative values except a few, implying dominant influence of old continental crusts in the generation of their igneous protoliths. [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]

Existing geochronological and geochemical data for the Early Carboniferous magmatic rocks in the eastern Tianshan, Xinjiang, have been interpreted in a variety of theories regarding petrogenesis and geodynamic setting. The proposed settings include rift, back-arc basin, passive continental margin, island arc, ridge subduction, and post-collisional environment. To evaluate these possibilities, we present new SHRIMP zircon U–Pb geochronology and geochemical data, whole-rock geochemical, Hf isotope, and S isotope data for tonalitic rocks and ores associated with the Tuwu porphyry copper deposit located in the center of the late Paleozoic Dananhu–Tousuquan arc, eastern Tianshan. SHRIMP zircon U–Pb dating indicates that the magmatic activity and thus associated copper mineralization occurred ca.332 Ma. The tonalitic rocks are calc-alkaline granites with A/CNK values ranging from 1.16 to 1.58; are enriched in K, Rb, Sr, and Ba; and are markedly depleted in Nb, Ta, Ti, and Th. They show geochemical affinities similar to adakites, with high Sr, Al 2 O 3 , and Na 2 O contents and La/Yb ratios; low Y and Yb contents; and slight positive Eu anomalies. In situ Hf isotopic analyses of zircons yielded positive initial ε Hf ( t ) values ranging from 6.9 to 17.2. The δ 34 S values of the ore sulfides range from −3.0‰ to +1.7‰, reflecting a deep sulfur source. Our results indicate that the paleo-Tianshan oceanic slab was being simultaneously subducted northward beneath the Dananhu–Tousuquan arc, and southward beneath the Aqishan–Yamansu arc during the Early Carboniferous. The Tuwu adakitic tonalitic rocks were derived from the partial melting of the subducted paleo-Tianshan oceanic slab, which was subsequently hybridized by mantle wedge peridotites. The slab-derived magmas have considerably high copper contents and are highly oxidized, thus leading to porphyry copper mineralization. Such Early Carboniferous tonalitic rocks that are widespread in the eastern Tianshan define a province with high potential for copper mineralization. [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 Batang Group (BTG) volcanic rocks in the Zhiduo area, with NW-trending outcrops along the northeastern margin of the Qiangtang terrane (northern Tibet), are mainly composed of volcaniclastic rocks, dacite and rhyolite. Major and trace element, Sr and Nd isotope, zircon U-Pb and Hf isotope data are presented for the BTG dacites. Laser ablation inductively coupled plasma mass spectrometry zircon U-Pb dating constrains the timing of volcanic eruption as Late Triassic (221 ± 1 Ma). Major and trace element geochemistry shows that the BTG volcanic rocks are classified as calc-alkaline series. All samples are enriched in large-ion lithophile elements and light rare earth elements with negative-slightly positive Eu anomalies (Eu/Eu* = 0.47-1.15), and depleted in high field strength elements and heavy rare earth elements. In addition, these rocks possess less radiogenic Sr [(Sr/Sr) = 0.7047-0.7078], much radiogenic Nd (ε( t) = −4.2 to −1.3) and Hf (ε( t) = 4.0-6.6) isotopes, suggesting that they probably originated from partial melting of a crustal source containing a mantle-derived juvenile component. The inferred magma was assimilated by crustal materials during ascending and experienced significant fractional crystallization. By combining previously published and the new data, we propose that the BTG volcanic rocks were genetically related to southwestward subduction of the Ganzi-Litang ocean (a branch of Paleo-Tethys) in the northeastern margin of the Qiangtang terrane. Given the coeval arc-affinity magmatic rocks in the region, we envisage that the Ganzi-Litang ocean may extend from the Zhongdian arc through the Yidun terrane to the Zhiduo area, probably even further northwest to the Tuotuohe area. [ABSTRACT FROM AUTHOR]

The geodynamic setting of Mesozoic magmatic rocks and associated mineralization in eastern Tianshan, Northwest China, are attracting increasing attention. The newly discovered giant Donggebi molybdenum deposit (0.508 Mt at 0.115% Mo) is located in the central part of eastern Tianshan, Xinjiang. The molybdenum mineralization was genetically associated with the Donggebi stock, comprised of porphyritic granite and granite porphyry. Secondary ion mass spectrometry (SIMS) zircon U–Pb dating constrains that the porphyritic granite and granite porphyry emplacement occurred at 233.8 ± 2.5 Ma and 231.7 ± 2.6 Ma, respectively. The Re–Os model ages of six molybdenite samples range from 235.2 to 237.0 Ma, with a weighted mean age of 236.1 ± 1.4 Ma, which is roughly consistent within errors with the zircon U–Pb ages, suggesting a Middle Triassic magmatic–mineralization event at Donggebi. Geochemically, the Donggebi granitoids are characterized by high SiO2and K2O contents, with low MgO contents, belonging to high-K calc-alkaline granites. These rocks show pronounced enrichment in K, Rb, U, and Pb, and depletion in Sr, Ba, P, and Ti, with negative Eu anomalies (Eu/Eu* = 0.20–0.38).In situHf isotopic analyses of zircon from the porphyritic granite and granite porphyry yieldedεHf(t) values ranging from +6.6 to +10.5, and from +5.5 to +10.1, respectively. The geochemical and isotopic data imply that the primary magmas of the Donggebi granitoids could have originated by partial melting of a juvenile lower crust that involved some mantle components. Combined with the regional geological history, geochemistry of the Donggebi granitoids, and new isotopic age data, we thus propose that the Donggebi molybdenum deposit was formed in the Middle Triassic, and occurred in an intracontinental extension setting in eastern Tianshan. [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]

The Chalukou porphyry Mo deposit, located in the northern Great Xing'an Range, is the largest Mo deposit in the Xing'an–Mongolia orogenic belt. Its ore bodies are mainly hosted in the intermediate-felsic complex and Jurassic volcanic sedimentary rocks, of which Late Jurassic granite porphyry, quartz porphyry and fine-grained granite are closely associated with Mo mineralization. The Middle Jurassic monzogranite belongs to shoshonite series, with SiO 2 and Al 2 O 3 contents of 69.48 to 74.98% and 12.35 to 14.48%, respectively. The total alkali (K 2 O + Na 2 O) content ranges from 7.67 to 10.42%, with K 2 O/Na 2 O ratios between 1.07 and 2.81. These rocks are strongly enriched in Rb and K but are depleted in Ta, Nb, P and Ti, with negative Eu anomalies and positive ε Hf (t). The Late Jurassic granite porphyry, quartz porphyry and fine-grained granite are shoshonite or high-K calc-alkaline series. Their SiO 2 and Al 2 O 3 contents range from 73.87 to 78.95% and 10.35 to 13.47%, respectively. The total alkali (K 2 O + Na 2 O) contents range from 8.06 to 10.02%, with K 2 O/Na 2 O ratios from 1.03 to 8.20. These rocks are strongly enriched in Rb, K and Th, but are depleted in P, Ti, Ba and Sr, indicating clear negative Eu anomalies and positive ε Hf (t). The Middle–Late Jurassic granitoids in the Chalukou deposit are highly fractionated I-type granitoids, and derived from juvenile lower crust materials that originated from the Neoproterozoic depleted mantle. These granitoids formed in the extension tectonic setting of the post-collision stage of the Mongol–Okhotsk orogenic belt, probably superposed by the back-arc extension related to the subduction of the Paleo-Pacific Plate. [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]

Rodingites occur in serpentine-matrix mélange of the Nagasaki metamorphic rocks in Japan. Two types of rodingites can be distinguished on the basis of their mode of occurrence and mineralogical composition. One occurs as dikes, which contain a mineral assemblage of grossular, vesuvianite, diopside, apatite, titanite, and zircon. The other occurs as a block, which consists of zoisite, clinozoisite, diopside, chlorite, apatite, titanite, and zircon. The former type of rodingites posses two types of zircons: prismatic and porous. The prismatic zircons contain primary fluid inclusions indicating their crystallization in the presence of fluids. The porous zircons have extensive fractures filled by zircon, which are indicative of a hydrothermal origin. Both zircon types were thought to have formed under the influence of fluids. U- Pb ion probe analyses of prismatic zircons from the rodingites yield a weighted mean age of 108-105 Ma, suggesting the Early Cretaceous as the time of rodingitization in the subduction zone. Hafnium isotopic compositions of prismatic zircons are close to or overlap with the mid ocean ridge basalt ( MORB) Hf isotopic ratio. This indicates that the fluid composition may have been reflected by the MORB composition during rodingitization. On the other hand, the low εHf values (11.8-18.9) of porous zircons suggest that they incorporate a small amount of Hf from fluid contaminated by subducted sediments. The rodingites are significantly enriched in Sr and depleted in large ion lithophile elements ( LILE) ( Cs, Rb, Ba). The fluid during rodingitization is able to extracts LILEs from the protolith of rodingites and adds Sr to the protolith of rodingites. The high field strength elements ( HFSE) ( Zr, Th, U, Nb, Ta) concentrations in the rodingites are similar to those of MORB, thus indicate their relatively immobile nature during rodingitization. [ABSTRACT FROM AUTHOR]

The Dagushan BIF-hosted iron deposit in the Anshan-Benxi area of the North China Craton (NCC) has two types of iron ore: quartz-magnetite BIF (Fe2O3T < 57 wt.%) and high-grade iron ore (Fe2O3T > 90 wt.%). Chlorite-quartz schist and amphogneiss border the iron orebodies and are locally present as interlayers with BIFs; chlorite-quartz schist and BIFs are enclosed by amphogneiss in some locations. The quartz-magnetite BIFs are enriched in HREEs (heavy rare earth elements) with positive La, Eu and Y anomalies, indicating their precipitation from marine seawater with a high-temperature hydrothermal component. Moreover, these BIFs have low concentrations of Al2O3, TiO2 and HFSEs (high field strength elements, e.g., Zr, Hf and Ta), suggesting that terrigenous detrital materials contributed insignificantly to the chemical precipitation. The high-grade iron ores exhibit similar geochemical signatures to the quartz-magnetite BIFs (e.g., REE patterns and Y/Ho ratios), implying that they have identical sources of iron. However, these ores have different REE (rare earth element) contents and Eu/Eu* values, and the magnetites contained within them exhibit diverse REE contents and trace element concentrations, indicating that the ores underwent differing formation conditions, and the high-grade ores are most likely the reformed product of the original BIFs. The chlorite-quartz schist and amphogneiss are characterized by high SiO2 and Al2O3 contents and exhibit variable abundances of REEs, enrichment in LREEs (light rare earth elements), negative anomalies in HFSEs (e.g., Nb, Ta, P and Ti) and positive anomalies in LILEs (large ion lithophile elements, e.g., Rb, Ba, U and K). A protolith reconstruction indicates that the protoliths of the chlorite-quartz schist are felsic volcanic rocks. SIMS and LA-ICP-MS zircon U-Pb dating indicate that this schist formed at approximately 3110 to 3101 Ma, which could represent the maximum deposition age of the Dagushan BIF. However, two groups of zircons from the amphogneiss are identified: 3104 to 3089 Ma zircons that are most likely derived from the chlorite-quartz schist and 2997 to 2995 Ma zircons, which are interpreted to represent the time of protolith crystallization. Thus, the Dagushan BIF most likely formed before 2997 to 2995 Ma. The ~ 3.1 Ga zircons yield εHf(t) values of - 8.07 to 5.46, whereas the ~ 3.0 Ga zircons yield εHf(t) values of - 3.96 to 2.09. These geochemical features suggest that the primitive magmas were derived from the depleted mantle with significant contributions of ancient crust. [ABSTRACT FROM AUTHOR]

The Huoqiu iron ore field in northwest Anhui Province is located in the North China Craton (NCC). As a large banded iron formation (BIF) iron ore field, ore bodies occur in a middle-high grade of Neoarchean metamorphic formation, forming a banded silicon-iron series from north to south. The main ore bodies can be divided into two sub-belts from bottom to upper layers, i.e. the A + B ore belt consisting of leptynite-schist-magnetite-quartz formation, and the D ore belt consisting of schist-marble-hematite-quartz formation. Based on a dataset from geological settings, geophysical and geochemical exploration, ore-forming conditions and structural analysis of the iron deposit, we discuss structural types, sedimentary environments, deep tectonic and ore-controlling factors as well as characteristics and distribution of this colossal BIF ore field in the Huoqiu region. Using LA-ICP-MS techniques, we obtained the oldest U-Pb age of ca. 2.7 Ga for plagioclase amphibolite as its original rock, and 1.8 Ga for magmatic granite in the Huoqiu Group. The Hf isotopes of zircon were also determined, resulting in the oldest Hf model age of 3.5 Ga. Geochemical data indicate that the protolithes of amphibolites belong to a series of subalkaline rocks with enrichments of large ion lithophile elements and depletions of high field strength elements, which are typical volcanic arc rocks. The amphibolites have low K2O concentrations with low ratios of Ti/V (22.7 to 25.9 averaging 24.5), similar to island arc tholeiite. This suggests that the iron deposit and BIF are of the Superior type in the Huoqiu region. [ABSTRACT FROM AUTHOR]

Eastern Shandong is one of the important early Precambrian areas in the North China Craton, where extensive 2.5, 2.7 and 2.9 Ga magmatic activities have been identified, followed by very strong late Neoarchean and Paleoproterozoic tectono-thermal events. We carried out SHRIMP zircon dating, Hf-in-zircon isotope analysis and a whole-rock geochemical study on ca. 2.9 Ga Mesoarchean magmatic rocks. These include gneissic diorite, gneissic quartz diorite, gneissic tonalite and gneissic high-Si trondhjemite and were identified in five new areas. All these rocks contain ca. 2.5 Ga metamorphic zircons. The dioritic and tonalitic rocks are enriched in large ion lithosphile (LIL) elements (K, Rb, Ba) and depleted in Nb and P with moderate to highly fractionated REE patterns, similar in chemical compositions to Archean TTG rocks worldwide. The high-Si trondhjemites are characterized by very high SiO 2 and very low FeOt + MgO. The magmatic zircon grains from all these rocks are similar in their Hf isotopic compositions and have ɛ Hf ( t ) values ranging from + 1.3 to +9.9. Combined with previous work, our main conclusions are: (1) eastern Shandong underwent a major magmatic event at ca. 2.9 Ga; (2) diorites and tonalites formed by melting of thickened lower crust or the root of an oceanic plateau, whereas the high-Si trondhjemites were derived from melting of intermediate to felsic rocks; (3) the Mesoarchean (ca. 2.9 Ga) was a major period of juvenile crustal addition from the depleted mantle, earlier than the major crustal growth period at 2.7–2.8 Ga in the North China Craton; (4) the 2.7–2.9 Ga rocks underwent strong metamorphism at ca. 2.5 Ga, probably as a result of magmatic underplating. [ABSTRACT FROM AUTHOR]

The Attappadi area on the south-western flanks of the Archean Dharwar Craton in southern India is located along the E–W trending Bhavani Shear Zone which marks the trace of a Neoarchean suture zone. The dominant rock types in the area include meta-ultramafics, amphibolites, TTG (tonalite–trondhjemite–granodiorite) gneisses, metapelites, and sulphidic banded iron formation (BIF). Here we report the occurrence of felsic volcanic rocks preserving primary textures from the Anaikatti area in eastern Attappadi. The felsic volcanics are interbanded with the BIF, amphibolite, metapelite, metapyroxenite and hornblende gneisses. The felsic volcanics are divided into two types based on their textures. The Type-1 rock is medium grained with gneissic texture and lack unequivocal primary volcanic textures. Type-2 felsic volcanics are thinly laminated, fine grained and at places preserve relict soft-sediment deformation structures. They also contain relict volcanic clasts or lapilli and are interpreted as felsic tuff. Geochemically, the Attappadi felsic volcanics are rhyolitic in composition and have arc-related trace element signatures. They also possess a calc-alkaline volcanic affinity. We report LA-ICPMS U–Pb ages from zircons in four samples of the felsic tuffs which show weighted mean ages of 2567 ± 18 Ma and (MSWD = 1.4), 2499 ± 19 Ma (MSWD = 0.57), 2555 ± 24 Ma (MSWD = 1.7) and 2576 ± 64 Ma (MSWD = 5.8). The late Neoarchean–early Paleoproterozoic ages obtained in our study correlate well with the zircon U–Pb ages reported in recent studies from ophiolites and other suprasubduction suites from Attappadi and surrounding regions. The zircon ε Hf values range from − 11.1 to 7.6 suggesting heterogeneous source material involving both juvenile and older reworked components. We build a tectonic model for the SW margin of the Dharwar Craton with an oceanic realm characterized by island arcs and widespread submarine tholeiitic as well as komatiitic ultramafic and mafic volcanism during the Neoarchean. This predominantly mafic volcanism on the ocean floor is represented by primitive komatiitic lavas, oxide and sulphide facies BIF. The birth of volcanic arc at the convergent margin is marked by felsic volcanism and the deposition of felsic volcanics and volcano-sedimentary successions. In the final stage of ocean closure, the ocean-plate and continental arc assemblages were brought in juxtaposition including the accretion of the ophiolitic fragments. Our study confirms the recent models of arc–arc and arc–continental accretion to the southern margin of the Dharwar Craton and major continental growth at the end of the Archean. [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]

U--Pb dating and Hf isotopic analyses were carried out on xenocrystic zircons from the Cenozoic alkali basalts in the Xilinhot region, NE China, to constrain the nature and evolution of the underlying Songliao terrane, and its role in the assembly of the Central Asian Orogenic Belt. Our data show a wide range of U--Pb age distributions, with Precambrian clusters of ca. 2500 Ma, 2400-2200 Ma, 2000-1700 Ma, 1500 Ma, 1000-800 Ma, 700-500 Ma, and Phanerozoic peaks at 494 Ma, 411 Ma, 312 Ma, 263 Ma, 214 Ma, 140 Ma and 44 Ma. The Phanerozoic age peaks are well-recognized in supracrustal rocks in the Songliao terrane or near the sample location. Although most Phanerozoic zircons have positive ɛHf(t) values, which is consistent with many locations throughout the Central Asian Orogenic Belt, some Phanerozoic ones have negative ɛHf(t) values and Tcrust up to ca. 2.5 Ga, indicating the involvement of old crustal components during the Phanerozoic thermal events. More importantly, zircons with 207Pb/206Pb ages between ca. 2500 Ma and 1700 Ma have Tcrust of 2.5-3.5 Ga, revealing the possible occurrence of unexposed Archean crustal remnants beneath the Songliao terrane, where no known supracrustal rocks are older than Neoproterozoic. Integrating the U--Pb and Hf isotopic results, we interpret the Songliao terrane as ancient in nature and with a complex crustal evolution history, including the addition of juvenile materials at ∼2.5 Ga, reworking of pre-existing crustal components at 2.4-2.2 Ga, 2.0-1.8 Ga, 1.8-1.7 Ga, 1.0 Ga, 0.7-0.6 Ga, and massive crustal growth during the Phanerozoic. Comparing these data with the Precambrian zircon age distributions of other cratons or micro-continents, we suggest the Songliao terrane shows an affinity to both Monglia and NE Gondwana. [ABSTRACT FROM AUTHOR]

Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite (DA) which is located at the northern margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios (0.39-1.35), implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted Pb/U average age of 1818±9 Ma, which is significantly different from former's Neoproterozoic age, and is coincidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE (Gd, Nd, and Ta). The chondrite-normalized REE pattern is slightly to the right form. The average ΣREE is 317.2×10; HREE show moderate fractionation [average LREE/HREE is 14.71, average (La/Yb) is 24.77; average (La/Sm) is 3.85, and average (Gd/Yb) is 3.46]; and the δEu and δCe are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from −6.6 to −4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is suggested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia. [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]

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 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 Outang intrusion was newly found near the South Tan–Lu fault belt (STLF) of the northeastern margin of Yangtze block due to the excavating construction of the Beijing–Shanghai high-speed railway. Observations show that lithology of the Outang intrusion is intermediate rock series, mainly composed of monzodiorite and quartz monzonite. Major and trace elements, zircon U–Pb dating and Hf isotope were analyzed. Two ages of 124.6±2.9Ma (MSWD=0.60, n=29) and 129.2±4.1Ma (MSWD=1.5, n=21) are obtained, showing that the regional igneous activity was in early Cretaceous, being consistent with the massive Yanshanian magmatic events in Eastern China. The quartz monzonite was identified as a high-Mg adakitic rocks, showing geochemical features of high Si, high K, and low Sr, which indicates that the igneous genesis may be results of partial melting of the delaminated lower crust. The negative εHf(t) values with much older t DM2 ages indicate that the original magma may derive from remelting of ancient continental crust. A tectonic model has been proposed to account for the massive subduction of the Pacific Plate beneath eastern China in Jurassic with effect of delamination and thinning, from which we conjecture that the Archean materials could compose the basement of the STLF caused by massive subduction of the Pacific Plate beneath the eastern China continent. [Copyright &y& Elsevier]

Daheishan giant porphyry Mo deposit is located in the Lesser Xing’an–Zhangguangcai Ranges, Jilin Province, NE China. Mineralization is closely related to the Daheishan intrusive complex, which can be divided into Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry. Four stages of mineralization are distinguished, based on the cross-cutting relationships of mineralized veins. LA-ICPMS zircon U-Pb analysis yields206Pb/238U ages of 177.9 ± 2.3 Ma for the Changganglin biotite granodiorite, 169.9 ± 2.3 Ma for the Qiancuoluo biotite granodiorite, and 166.6 ± 4.0 Ma for the Qiancuoluo granodioritic porphyry. Hydrothermal fluids responsible for mineralization evolved from different magmas. Six molybdenite samples yield Re-Os model ages of ~167 Ma. Muscovite from the last mineralization stage gives a40Ar/39Ar plateau age of 163.6 ± 0.9 Ma. Geochronology data indicate that the entire magmatic system lasted for about 10 million years, and the total duration of hydrothermal activity was less than 4 million years. The εHf(t) values of zircons obtained from the Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry range from 4.5 to 9.1, 5.7 to 10.9, and 4.4 to 7.1, respectively, indicating that they were mainly derived from the depleted mantle, although contaminated by crustal materials to a greater or lesser extent. The formation of the Daheishan porphyry Mo deposit was temporally and spatially related to the amalgamation of Jiamusi Massif and Songliao terrane in the Palaeo-Pacific Ocean regime. Regional Hf isotopic compositions of zircon suggest an episode of crustal growth in the Phanerozoic in the Lesser Xing’an–Zhangguangcai Ranges. Regional Mo mineralization ages suggest a peak of porphyry Mo mineralization in the Jurassic in the Lesser Xing’an-Zhangguangcai Ranges. [ABSTRACT FROM AUTHOR]

Abstract: The Late Cretaceous Mengyejing Formation, which contains the only pre-Quaternary potash salt deposit in the Simao Basin, southeastern Tibet, is thought to be genetically related to the Maha Sarakham Formation in the Khorat Basin. The provenance and paleogeography of these two basins have been under debate, although little diagnostic evidence has been previously published. A combined analysis of whole rock geochemistry, zircon U–Pb chronology, and Hf isotopic compositions was performed to characterize the provenance of the Mengyejing Formation. These formation's sandstones are characterized by moderate chemical index of alteration (CIA) values. These values, together with plots of the Th/U–Th ratios, suggest that certain samples have undergone moderate weathering and sedimentary recycling. The major and trace elements (La/Th–Hf, Th/Sc–Zr/Sc, Eu/Eu*–Th/Sc, TiO2–Fe2O3 T +MgO, Al2O3/SiO2–Fe2O3 T +MgO, K2O/Na2O–SiO2) indicate that the sedimentary sources were felsic rocks from an active continental margin or continental arc with a minor amount of recycled sediment from a passive continental margin. The Mengyejing Formation contains detrital zircons primarily with U–Pb ages of 2.45–2.57Ga, 1.8–1.9Ga, 740–880Ma, 410–470Ma, and 215–300Ma. The results reveal that the pre-Devonian zircons are derived from the recycled sediments of the Yangtze block originating in the Qinling Orogenic Belt, and they share this provenance with the coeval sediments in the Khorat Basin. The magmatic rocks of the Ailaoshan and Lincang areas are responsible for supplying the Devonian to Triassic detrital zircons. These provenance data combined with published paleocurrent results suggest that the Simao Basin was situated on the western margin of the Khorat Basin during the Late Cretaceous. The basins were connected when marine incursion occurred. We propose that pre-Devonian materials from the southwestern Sichuan Basin first supplied detritus to the Simao Basin and subsequently to the Khorat Basin. [Copyright &y& Elsevier]

The Daheishan porphyry Mo deposit was recently discovered in the northern segment of the Great Xing'an Range, NE China. Three main types of granitoids are identified in this deposit: granodiorite, fine-grained granite, and porphyritic granite. The orebodies are dominantly hosted within the granodiorite and in the contact zone between the granodiorite and tuff or hornfels, while no mineralization has been found in the fine-grained granite or the porphyritic granite. We present in situ LA-ICP- MS zircon U- Pb dates for the granodiorite, fine-grained granite, and porphyritic granite, which yielded 146.9 ± 1.1 Ma (2σ), 146.6 ± 1.7 Ma (2σ), and 149.7 ± 4.2 Ma (2σ), respectively. Their εHf(t) values range from 3.9 to 12.2, associated with young crustal model ages ( TDM2) ranging from 524 Ma to 849 Ma, indicating that their parental magmas may have been generated by partial melting of the Neoproterozoic- Cambrian crustal components. The formation of the Daheishan deposit was genetically related to the subduction of the Paleo- Pacific Plate. [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]

Geochemical, zircon U-Pb ages and Hf isotopic characteristics of two-feldspar gneiss from Taihua Group in Xiaoqinling area were analyzed. Geochemical results indicate that the protolith is high K calc-alkaline granitic rock with high REE content (229 × 10-6), obvious fractionation (w(La)N/w(Yb)N =45. 39) of LREE and HREE and obvious negative Eu anomaly (0. 43). The primitive mantle-normalized trace element spider diagram shows that it is enriched in LILE (e. g. Rb, Ba, Th and U) and relatively depleted in HFSE (e. g. Nb, Ta, Sr, P and Ti). The results of zircon U-Pb dating indicate that the forming age of protolith is early Paleoproterozoic (2. 47 Ga). The results of zircon Hf isotope indicate that the range of initial N(176Hf)/N(177Hf) is small (0.281 284-0.281 328), ϵHf(t) values are positive (0.93-5.18); the two-stage Hf model ages are 2. 70-2. 89 Ga, and new continental crust (modern island arc volcano) Hf model ages are 2. 54-2. 73 Ga, which are close to the crystal age of zircon (2. 47 Ga), so that new crustal growth is obvious in this period in the southern North China Craton. There are three important tectono-thermal events in early Neoarchean (2. 7-2. 9 Ga), late Neoarcheanearly Paleoproterozoic (2. 2-2. 5 Ga) and middle Palaeoproterozoic (1. 8-2. 1 Ga) in the southern North China Craton. New crustal growth is obvious in early and late Neoarchean (ϵHf(t)>0), and new crustal growth is obvious for magmation in late Neoarchean-early Paleoproterozoic and middle Palaeoproterozoic, accompanying with recirculation and transformation of ancient crustal material (ϵHf(t)>0 or ϵHf(t)<0). [ABSTRACT FROM AUTHOR]

Tongshan intrusion in Chizhou of Anhui is one of the ore-bearing intrusions in the main magmatic belt along the middle-lower Yangtze River, and the formation age and rock genesis are still controversial. The intrusion is mainly composed of quartz diorite, quartz monzonitic porphyry and granodiorite, and has close relationship with the Cu-Au mineralization. Zircon UPb geochronology and Hf isotopic geochemistry of granodiorite in Tongshan skarn Cu (Au) deposit were studied. Results of petrogeochemistry and isotope chronology show that the age of granodiorite intrusion, which forms in Early Cretaceous, is (146. 3 ± 3. 2) Ma; the average of zircon ϵHf(t) is -5. 23, illustrating that Tongshan intrusion has the characteristics of magmatite provenance with crust mantle mixing; distributions of two-phase Hf model ages of zircon are 1 184.51-1 422. 72 Ma, indicating that magma source has significant relationship with the outcropped Mesoproterozoic basement in southern Anbui. Tbe discrimination diagrams sbow tbat Tongsban intrusions belong to tbe island-arc granite (VAG) , and tbe tectonic background of tbe intrusions is same as tbe ore-bearing rocks of Cu-Au deposits along tbe middle-lower Yangtze River, so tbat it is inferred tbat the geotectonic backgrounds form in continental margin magmatic are related to Paleo-Pacific Plate subduction. [ABSTRACT FROM AUTHOR]

Jinchuan Cu-Ni sulfide deposit, which is formed in small Neo-Proterozoic ultra-mafic intrusion, is the largest base of Ni in China. The wall rocks are metamorphic rocks featured by amphibolite facies in Paleoproterozoic Baijiazuizi Formation. The key factors of mineralization are still attracted broad attention. The intruding contact boundary can be found between intrusion and its wall rock by detail geological mapping, Jinchuan intrusion is sill-like, and the top of intrusion is in the southwest and the bottom of intrusion is in the northeast; according to SHRIMP zircon U-Pb geochronology and Hf isotope, the average age of zircon is (840 ± 10) Ma, which is corresponding to the age of (831. 8 ± 0. 6) Ma measured by formers considering error and ϵHf(t) values of zircons are concentrated in -8. 52- -4. 85; Hf model age is more than zircon U-Pb age, so that the magma sources have been contaminated by crustal material or from enriched mantle. Hf-Sr-Nd-Pb-Os isotope analysis indicates that the magma sources forming Jinchuan Cu Ni sulfide deposit helong to I-type enriched mantle ( EM I ) , the petrogenetic and metallogenic setting is connected with continental rift, so that the special tectonic setting and magma sources mayhe significantly contrihute to the mineralization of Jinchuan super-large scale Cu-Ni sulfide deposit. [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]

In situ U-Pb dating and Hf isotopic of detrital zircons from beach sediments of Yalong Bay were analyzed to trace sedimentary provenance and reveal the crustal evolution of Hainan Island in South China. The grain size distribution of the sediments displays a clear single-peak feature, indicating the sediments were formed under the same condition of hydrodynamic force. The detrital zircons had Th/U ratios of greater than 0.1, and REE pattern displayed a positive Ce anomaly and a negative Eu anomaly, indicating that these zircons are predominantly of magmatic origin. The U-Pb spectrum of detrital zircons mainly peaked at the Yanshanian (96-185 Ma), Hercynian-Indosinian (222-345 Ma) and Caledonian (421-477 Ma). A portion of the detrital zircons were of Neoproterozoic origin (728-1,003 Ma), which revealed that the basement in the eastern region of Hainan Island was mainly of Neoproterozoic, with rare Archean materials. The positive ε( t) values (0 to +10.1) of the Neoproterozoic detrital zircons indicated that the juvenile crust grew in the southeastern Hainan Island mainly during the Neoproterozoic period. The Neoproterozoic orogeny in the southeastern part of the island (0.7-1.0 Ga) occurred later than in the northwestern region of the island (1.0-1.4 Ga). Importantly, the Grenvillian orogeny in the southeastern area of Hainan Island shared the same timing with that of the western Cathaysia Block; i.e., both areas concurrently underwent this orogenic event, thereby forming a part of the Rodinia supercontinent. Afterwards, the crust experienced remelting and reworking during the Caledonian Hercynian-Indosinianand Yanshanian accompanied by the growth of a small amount of juvenile crust. [ABSTRACT FROM AUTHOR]

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]

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]

The Central Asian Orogenic Belt (CAOB) consists of many tectonic terranes with distinct origin and complicated evolutionary history. Understanding of individual block is crucial for the reconstruction of the geodynamic history of the gigantic accetionary collage. This study presents zircon U-Pb ages and Hf isotopes for the granitoid rocks in the Russian Altai mountain range (including Gorny Altai, Altai-Mongolian terrane and CTUS suture zone between them), in order to clarify the timing of granitic magmatism, source nature, continental crustal growth and tectonic evolution. Our dating results suggest that granitic magmatism of the Russian Altai mountain range occurred in three major episodes including 445~429 Ma, 410~360 Ma and ~241 Ma. Zircons from these granitoids yield comparable positive εHf(t) values and Neoproterozoic crustal model ages, which favor the interpretation that the juvenile crustal materials produced in the early stage of the CAOB were probably dominant sources for the Paleozoic magmatism in the region. The inference is also supported by widespread occurrence of short-lived juvenile materials including ophiolites, sea-mount relics and arc assemblages in the northern CAOB. Consequently, the Paleozoic massive granitic rocks maybe do not represent continental crustal growth at the time when they were emplaced, but rather record reworking of relatively juvenile Protero-zoic crustal rocks although mantle-derived mafic magma was possibly involved to serve as heat engine during granitic magma generation. The Early Triassic granitic intrusion may be a product in an intra-plate environment, as the case of same type rocks in the adjacent areas. The positive eHf(t) values (1.81~7.47) and corresponding Hf model ages (0.80~1.16 Ga) together with evidence of petrology are consistent with the interpretation that the magma source of the Triassic granitic intrusion was derived from enriched mantle and melted under an usually high temperature condition likely due to basaltic magma that underplated the lower crust. Our data combined with evidence of the regional geology enable us to conclude that the Gorny Altai and Altai-Mongolian terranes possibly have similar tectonic natures, but represent two separate accretionary systems before Devonian collision. The accretion and amalgamation processes resulted in the Paleozoic granitoid magmatism and caused the two terranes to merge as a composite tectonic domain at the Siberian continental margin. [ABSTRACT FROM AUTHOR]

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]

Abstract: Sharang is a low-fluorine, calc-alkaline porphyry Mo deposit hosted mainly in a granite porphyry of a multi-stage plutonic complex in the northern Gangdese metallogenic belt, largely with stockwork and ribbon-textured mineralization. The observed age estimates suggest that the formation of the magmatic host complex (52.9–51.6Ma) and the ore deposit itself (52.3Ma) occurred during the main stage of the India–Asia collision. The host rocks are characterized by lower zircon εHf(t) values than those of the pre-ore and post-ore rocks. This suggests that the Lhasa terrane basement might play an important role in the formation of Sharang ore-forming intrusions. In view of the framework of magmatic–metallogenic events we suggest that slab roll-back may have induced melting of juvenile crust and ancient continental complexes during the India–Asia collision. This proposal focuses exploration for additional molybdenum deposits on the collision zone. [Copyright &y& Elsevier]

The Badu complex and associated Paleoproterozoic granitoids are among the oldest known rocks in the Cathaysia Block in South China. The Paleoproterozoic units of the Badu complex are dominantly composed of metapelitic rocks and meta-greywackes. Here we report LA-SS-ICP-MS (laser ablation-split-stream inductively coupled plasma-mass spectrometry) zircon U–Pb data from a newly discovered garnet-bearing granite which show an emplacement age of 1929±15Ma and metamorphism at 1872±34Ma. We also report U–Pb ages of 1886±16Ma, 1858±7Ma, 1848±11Ma from a gneissic granodiorite, and two charnockites respectively. The garnet-bearing granite is peraluminous with A/CNK range from 1.1 to 1.3. The rock shows relatively high SiO2, K2O and Rb contents, and low total REE, Sr, CaO and ferromagnesian components, typical of leucogranites. The whole rock Nd two-stage model age(TDM2(Nd)) of this rock is ca. 2.7Ga, zircon Hf crustal model ages(TDM C(Hf)) peak at about 2.7Ga, and abundant inherited zircons occur with U–Pb ages in the range of 2044 to 2803Ma. Evidences from zircon U–Pb age and Hf isotope compositions, whole rock Nd isotopes and whole rock major and trace elements suggest a metasedimentary protolith, and that the garnet-bearing granite (leucogranite) was derived by partial melting in a thickened crust at about 1.93Ga. The gneissic granodiorite and charnockites show indistinguishable major and trace element features, as well as zircon Hf and whole rock Nd isotope compositions, indicating that they were generated from the same source rocks. The gneissic granodiorite and charnockites are ferroan, calc-alkalic and metaluminous with A/CNK range from 0.80 to 0.98. They display relatively low SiO2 contents and Ga/Al ratios, suggesting their A-type affinity. Their zircon TDM C(Hf) age-peak is 2.9Ga and whole rock TDM2(Nd) ages range from 2.8 to 2.9Ga. These high temperature rocks were generated possibly through the partial melting of ancient amphibolites (2.9Ga), with heat input from asthenosphere upwelling and magmatic underplating in an extensional setting at about 1.85–1.88Ga. Combined with data from previous studies, we suggest three episodes of major crustal growth in this region at 1.8–1.9Ga, ~2.7Ga and ~2.9Ga. During the 1.8–1.9Ga event, extensive reworking also took place. From the 1.93Ga syn-collision leucogranite (garnet-bearing granite), the 1.88–1.85Ga post-collision A-type granites and charnockites (the granite–charnockite suite), and the1.85–1.77Ga intraplate basaltic rocks (Li 1997 and Xiang et al. 2008) in the region, a Paleoproterozoic orogenic cycle can be deciphered in the Cathaysia Block. The rapid transition of tectonic regime from collision to post-collisional extension can be correlated to the assembly of the supercontinent Columbia. [ABSTRACT FROM AUTHOR]

Clastic sediments and sedimentary rocks are widely used for understanding the formation and evolution of the continental crust. The Tietonggou Formation outcrops in the Xiaoqinling region at the southern margin of the North China Craton (NCC) and has unconformable contacts with the underlying Taihua Complex and overlying Paleoproterozoic Xiong'er Group. It mainly consists of quartzite and its protoliths are mature terrigenous clastic rocks. On the basis of the ages of the youngest detrital zircons from the quartzites and the ages of the Xiong'er Group, the depositional ages of the protoliths of the Tietonggou Formation were well constrained to 1.91-1.80 Ga. The U-Pb isotopic data of detrital zircons from the Formation show a major age peak at ∼2.1 Ga, which is consistent with 2.2-2.0 Ga magmatism in the Trans-North China Orogen of the NCC. Taking into account the texctural and compositional maturity of the Tietonggou Formation quartzite, the ∼2.1 Ga lithologic units in the Trans-North China Orogen are interpreted as the major source of the Tietonggou Formation. The majority of these ∼2.1 Ga detrital zircons mostly have high δO values (>6.5‰) and negative ɛ( t) values (−7.8-0.0), with corresponding Hf model ages significantly older than their crystallization ages, indicating that these zircons formed from the partial melting of ancient continental crust. The majority of the 2.8-2.7 Ga and ∼2.5 Ga detrital zircons from the Tietonggou Formation had positive ɛ( t) values, and mantle-like δO values, suggesting that the NCC has experienced two stages of significant crustal growth in the Neoarchaean at 2.7 and 2.5 Ga, respectively. The Hf isotopic data of detrital zircons from Paleoproterozoic metasedimentary rocks in the Trans-North China Orogen varied mainly toward the reduction of the radiogenic Hf isotope and gradually show a similar trend of the isotope trajectories of crustal evolution. This reveals that the NCC probably has not developed a long-lived subduction to complete the final assembly of the NCC. Alternatively, these maybe imply that the tectonic setting of the NCC substantially changed at ∼2.1 Ga, the reduction of the radiogenic Hf isotope could be attributed to the rollback of the subducting slab. [ABSTRACT FROM AUTHOR]

Clastic sediments and sedimentary rocks are widely used for understanding the formation and evolution of the continental crust. The Tietonggou Formation outcrops in the Xiaoqinling region at the southern margin of the North China Craton (NCC) and has unconformable contacts with the underlying Taihua Complex and overlying Paleoproterozoic Xiong’er Group. It mainly consists of quartzite and its protoliths are mature terrigenous clastic rocks. On the basis of the ages of the youngest detrital zircons from the quartzites and the ages of the Xiong’er Group, the depositional ages of the protoliths of the Tietonggou Formation were well constrained to 1.91–1.80 Ga. The U-Pb isotopic data of detrital zircons from the Formation show a major age peak at ∼2.1 Ga, which is consistent with 2.2–2.0 Ga magmatism in the Trans-North China Orogen of the NCC. Taking into account the texctural and compositional maturity of the Tietonggou Formation quartzite, the ∼2.1 Ga lithologic units in the Trans-North China Orogen are interpreted as the major source of the Tietonggou Formation. The majority of these ∼2.1 Ga detrital zircons mostly have high δ18O values (>6.5‰) and negative ɛHf( t) values (−7.8–0.0), with corresponding Hf model ages significantly older than their crystallization ages, indicating that these zircons formed from the partial melting of ancient continental crust. The majority of the 2.8–2.7 Ga and ∼2.5 Ga detrital zircons from the Tietonggou Formation had positive ɛHf( t) values, and mantle-like δ18O values, suggesting that the NCC has experienced two stages of significant crustal growth in the Neoarchaean at 2.7 and 2.5 Ga, respectively. The Hf isotopic data of detrital zircons from Paleoproterozoic metasedimentary rocks in the Trans-North China Orogen varied mainly toward the reduction of the radiogenic Hf isotope and gradually show a similar trend of the isotope trajectories of crustal evolution. This reveals that the NCC probably has not developed a long-lived subduction to complete the final assembly of the NCC. Alternatively, these maybe imply that the tectonic setting of the NCC substantially changed at ∼2.1 Ga, the reduction of the radiogenic Hf isotope could be attributed to the rollback of the subducting slab. [ABSTRACT FROM AUTHOR]

Abstract: The Mt Painter Province of northern South Australia is a site of exceptional suite of Mesoproterozoic high heat producing (HHP) granites and felsic volcanics. These rocks have very high heat production values of >5μWm−3. The HHP granites, including the Mt Neill, Box Bore, Terrapinna, Wattleowie and Yerila granites, form part of a broadly coeval association of mafic and felsic volcanic rocks that also include the Pepegoona Volcanics, lamprophyres and mafic–intermediate dykes. U–Pb LA-ICPMS zircon dating and Hf-in-zircon isotopic data are used to constrain both the timing and source of these magmatic rocks. U–Pb zircon LA-ICPMS crystallization ages range from ~1596 to 1521Ma and imply a protracted sequence of magmatic events. Initial Hf isotopic compositions of these zircons from both dykes and felsic rocks have overlapping compositional ranges, with εHf values mainly from +4 to −2. These Hf values are significantly higher than contemporary crustal values which are likely to have been in the range −4 to −20. These data imply that the magmatic suite has both mantle and crustal sources. [Copyright &y& Elsevier]

Paleozoic sediment provenance of the Permian Basin remains controversial. This study presents new detrital zircon morphology, U Pb ages, and Hf isotope data of eight Paleozoic sandstone samples, and integrates published zircon U Pb data in the basin to illustrate the spatial and temporal changes of sediment provenance. The Cambrian sample has predominantly Mesoproterozoic (1500–1300 Ma) grains because of fluvial transport of basement detritus from the local Texas Arch. The Ordovician shoreface sandstone contains mostly rounded grains of Paleoproterozoic (1800–1600 Ma) age, mostly likely by longshore drift reworking detritus from the Transcontinental Arch. The Pennsylvanian sediment provenance shows heterogeneity. While samples from the Northwestern Shelf have both the Mesoproterozoic and Paleoproterozoic groups and low grain roundness, reflecting sediment delivery from basement rocks in the Ancestral Rocky Mountains, a sample in the Midland Basin contains a broad range of ages, including a major Neoproterozoic (800–500 Ma) group that were primarily from peri-Gondwana terranes. The difference suggests that there was limited sediment mixing in the Permian Basin. The similarity of zircon age distributions between the Midland Basin and Fort Worth Basin confirms synorogenic progradation of detritus from the Fort Worth Basin to the Eastern Shelf during the Pennsylvanian. During the early Permian Cisuralian epoch, the compiled U Pb data show that the southern and eastern basin contains a significant fraction of Gondwanan detritus, and the amount reduced by the latest Cisuralian as the orogenesis waned. The middle Permian Guadalupian samples on the Northwestern Shelf contain well-rounded grains that are of mainly Grenvillian and Paleozoic ages, suggesting sediment recycling from Laurentia by wind and likely by river as well. The change of sediment provenance from the early to the middle Permian suggests that after the continental collision, Laurentian sediments dominated detritus in the Permian Basin. • Early Paleozoic detritus were ultimately derived from the Transcontinental Arch. • Gondwana detritus arrived at the southern and eastern basin by Pennsylvanian time. • ARM detritus dominated the northwestern basin during the Pennsylvanian. • Gondwana detritus increased from Pennsylvanian to Cisuralian time, then decreased. • Appalachian detritus were transported by wind or river during the Guadalupian. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au mineralization and ore-related magmatism occurred in an extensional setting associated with the subduction of the Paleo-Pacific Plate. • The synchronic basic dikes and granites can be regarded as a precursor to the Au mineraliziton in the JMD. • Mantle- and crustal-fluids and metals substantially contributed to the formation of the giant Au mineralization in the JMD. The Jiapigou mining district (JMD) in the northeastern margin of the North China Craton mainly contains quartz vein- and altered rock-type gold deposits that have been prospected and mined for over 200 years. However, the ore-formation mechanism and geodynamic setting are still limited understood. Here we present new geological, mineralogical, gochronological, geochemical and Hf isotopic evidences of the ore-related intrusions from the deposits in the JMD to reveal the tectonic setting and genetic relationship between the Au mineralizitions and synchronic magmatism. The results show the following: (1) zircon U–Pb dating of the ore-related intrusions, such as basic dikes (gabbro and porphyritic gabbro), granites, and acid dikes (granite aplite dike and rhyolite porphyry) bracket their emplacement in the range of 177–171 Ma; (2) The basic dikes are characterized by enrichment in large ion lithophile elements (LILEs; i.e., Rb, Ba, and U), moderately depletion of high field strength elements (HFSEs; i.e., Nb and Ta), and high ε Hf (t) values (–13 to +12.8), whereas granites are characterized by high SiO 2 (73.24–75.12 wt%) and total alkali (K 2 O + Na 2 O = 5.74–8.58 wt%) concentrations, low TFe 2 O 3 (0.78–1.43 wt%) and CaO (0.98–1.36 wt%) concentrations, enrichment of LILEs (i.e., Rb, Ba, Th, and K) and depletion of HFSEs (i.e., Nb, Ta, Ti, and P), and low high ε Hf (t) values (–13.6 to –11.0), which features as well as those of the acid dikes. These results indicate that the ore-related intrusions, such as basic dikes, granites, and acid dikes were emplaced during the Middle Jurassic (177–171 Ma), constrained that the giant Au mineraliziton in the JMD occurred in the Middle Jurassic. And the basic dikes were likely derived from an enriched lithospheric mantle source that has been influenced by fluids expelled from a subducted slab, whereas granites and acid dikes were likely derived from partial melting of Archean crustal materials. Combined with regional geological observations, we conclude that the giant Au mineralization and ore-related magmatism occurred in an extensional setting associated with the subduction of the Paleo-Pacific Plate. The basic dikes and granites can be regarded as a precursor for the Au mineraliziton in the JMD. And mantle- and crustal-fluids and metals substantially contributed to the formation of the giant Au mineralization in the JMD. [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]

The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt. Five banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U-Pb zircon dating, which yielded protolith emplacement ages of 2469 ± 22 Ma, 2479 ± 12 Ma, 2497 ± 21 Ma, 2501 ± 17 Ma and 2509 ± 14 Ma, respectively. An important peak age of ∼2.48 Ga was also obtained for a metasedimentary rock in the same region. These discoveries suggest the occurrence of magmatic activity of 2.51-2.47 Ga at the northern margin of the Yangtze craton. The age-corrected ɛ( t) values obtained from in situ zircon Hf isotopic analysis are mainly between −5.5 and +0.3, and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga. Considering two important periods of ∼3.3-3.2 Ga and ∼2.95-2.90 Ga for the continental crustal growth in the Yangtze craton, we infer that the dioritic-granitic gneisses from the Douling Complex are the products of reworking of Paleo- to Mesoarchean crust at the northern margin of the Yangtze craton at ∼2.5 Ga. In addition, metamorphic ages of 837 ± 8 Ma and 818 ± 10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock, indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic, although its geological meaning remains ambiguous. [ABSTRACT FROM AUTHOR]

Highlights: [•] A back-arc basin developed along the southeastern Yangtze Block at 842–825Ma. [•] Neoproterozoic juvenile crustal growth in the southeastern Yangtze Block. [•] Orogen-parallel motion played a significant role in amalgamation of South China. [ABSTRACT FROM AUTHOR]