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The Liziyuan gold deposit, situated on the south side of the Shangdan suture zone, West Qinling Orogen, occurs in metamorphic volcanic rocks (greenschist facies) of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite. Orebodies in the Liziyuan gold field are controlled by the ductile‐brittle shear zone, and by thrusting nappe faults related to the Indosinian orogeny. In detail, this paper analyzed the geological characteristics of the Liziyuan gold field, and the Pb isotopes of the Lziyuan host rocks, granitoids (Tianzishan monzogranite and Jiancaowan syenite porphyry), sulfides, and auriferous quartz veins by multiple‐collector inductively coupled plasma mass spectrometry (MC–ICP–MS). In addition, previous data on the sulfur, hydrogen, and oxygen isotopes were employed to discuss the possible sources of the ore‐forming fluids and materials, and to further understand the tectonic setting of the Liziyuan gold deposit. The sulfides and their host rocks (Lziyuan Group), Tianzishan monzogranite and Jiancaowan syenite porphyry, and auriferous quartz veins have similar Pb isotopic compositions. Zartman's plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves. In the Δβ‐Δγ diagram, which genetically classifies the lead isotopes, most of the data fall within the range of the subduction‐zone lead mixed with upper crust and mantle. This indicates that a complex source of the ore lead formed in the orogenic environment. The δ34S values of the sulfides range from 3.90 to 8.50‰ (average 6.80‰), with a pronounced mode at 5.00‰–8.00‰. These values are consistent with that of orogenic gold deposits worldwide, indicating that the sulfur sourced mainly from reduced metamorphic fluids. The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the ore‐forming fluids, with possible mixing of minor magmatic fluids, but the late stage was dominated by meteoric water. The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide. [ABSTRACT FROM AUTHOR]

Abstract: Cretaceous magmatism in southern Lhasa subterrane, Tibetan plateau has been investigated for many years and a series of models have been proposed to illustrate their petrogenesis and geodynamic implications. But rare work has been done on the Cretaceous magmatism in central Lhasa subterrane. Here we report the petrology, zircon in situ U–Pb geochronology, Hf isotopes, trace element, and whole-rock elements and Sr–Nd isotopic geochemical data of the host granodiorites, and gabbroic and dioritic enclaves in Mamba area, central Lhasa subterrane. Zircon U–Pb dating for a Mamba host granodiorite yields a crystallization age of ~84Ma, with in situ Hf isotopic analyses for 18 spots of the same zircons of εHf (t) ranging from −7.5 to −0.3. A dioritic enclave (85.2Ma) is coeval with the host granodiorite and shows similar zircon Hf isotopic compositions (εHf (t)=−4.0 to +0.2). Mamba granodiorites (SiO2 =66.6–67.5wt.%) and dioritic enclaves (SiO2 =53.9–57.6wt.%) are high-K calc-alkaline, and a gabbroic enclave is shoshonitic (K2O=2.81%). All these samples are metaluminous, and enriched in large ion lithophile elements (LILEs, such as Rb, Ba, K, U, Th) and depleted in high field strength elements (HFSEs, e.g., Nb, Ta, Ti, and Zr). The host granodiorites are enriched in light rare earth elements (REEs), depleted in heavy REEs with weakly negative Eu anomalies (δEu=0.86–0.88), with high Al2O3 (15.0–15.7wt.%), high Sr/Y ratio (58.1–68.3) and Sr (680–755ppm), and low Y (10.8–13.0ppm) abundance, suggesting adakitic affinities. Mamba adakitic granodiorites, gabbroic and dioritic enclaves exhibit homogeneous Sr isotopes ((87Sr/86Sr)i =0.7066–0.7067, 0.7073, and 0.7067, respectively) and Nd isotopes (εNd(t)=−5.7 to −4.4, −4.0, and −3.6, respectively). These geochemical features allowed us to conclude that the adakitic host granodiorites and mafic (gabbroic–dioritic) enclaves were derived from magma mixing between ancient thickened lower crust and enriched fluid-metasomatized mantle. The distance between Mamba and the suture zone was more than 200km when the intrusives emplaced at ~85Ma, which implies that these rocks cannot be resulted from the mid-ocean ridge subduction. Combining of the intra-plate environment indicated by the gabbroic enclave of this study, the presence of the coeval bimodal igneous rocks in the similar latitude in central Lhasa subterrane, and other records in late Cretaceous sedimentary basin, the Mamba ~85Ma magmatism were attributed to the back-arc extension of Neo-Tethyan Ocean. [Copyright &y& Elsevier]

Inductively coupled plasma mass spectrometry (ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO acids in high-temperature and high-pressure closed-vessel digestion technique were used to decompose some Chinese reference materials, and thirty seven elements were determined by ICP-MS. Most of the results for Chinese soil reference materials were found to be in reasonable agreement with the reference values, except Cs, Ta, Li, Ge, Zn, Nd, Tb and Ta whose values need to be revised. Their precisions were typically lower than 5% RSD. However, the Precisions of Chinese clay reference materials, especially for GBW03102 and GBW03102a, were significantly different with reference values, probably reflecting the existence of a coarser-grained fraction (>70 μm) in samples, and the formation of fluorides in Al-rich samples during sample decomposition by using the mixture of HF and HNO acids. Moreover, thirty-seven trace elements covering the mass range from Li to U in four Chinese clay reference materials were firstly provided with good precision and accuracy in this study. [ABSTRACT FROM AUTHOR]

Abstract: An integrated study of petrology, zircon U–Pb age, and geochemistry was reported for a Paleoproterozoic granitic pluton from the Kongling terrain in the northern part of the Yangtze Block. The Quanqitang pluton is composed mainly of alkali feldspar, quartz, biotite and plagioclase. Zircon U–Pb dating yields a 207Pb/206Pb age of ca.1.85Ga, which represents its intrusion age. The Quanqitang pluton has high SiO2 (72.6–74.4wt.%), K2O (5.09–5.56wt.%) and Na2O (3.02–3.36wt.%), and low Fe2O3 (2.56–3.19wt.%) and MgO (0.25–0.37wt.%). It is metaluminous (A/CNK=0.93–0.98) and belongs to the high-K calc-alkaline series. On the chondrite-normalized REE diagram, all the samples invariably show a relatively enrichment in light rare earth elements (LREEs) with high (La/Yb)N ratios (10.6–21.7) and strong negative Eu anomalies. Their primitive-mantle normalized spidergrams display negative Ba, Nb, Ta, Sr, P, Eu and Ti anomalies. The calculated zirconium saturation temperatures range from 802 to 861°C with an average of 845°C. Zircons from the granites have ε Hf(t) values ranging from −17.6 to −20.9, corresponding to two-stage Hf modal ages of 3.6 to 3.8Ga. Based on the geochemical features, it is inferred that the granites were generated by the dehydration melting of Archean tonalitic gneisses with a plagioclase-rich residual assemblage. The granites chemically belong to the A2-type granites, and have an intrusion age younger than the possible ca. 2.0Ga collisional event in the Yangtze Block. This suggests that they formed in a post-collisional tectonic setting, and thus a tectonic regime switch from collision to extension might have occurred in the Yangtze Block before ca. 1.85Ga. The occurrence of the A2-type granite indicates that the Kongling microcontinental block became a stabilized craton at ca. 1.85Ga. [Copyright &y& Elsevier]

Abstract: The early history of the Yangtze Block has not been well constrained yet, due to the scarce outcrops of Archean to Paleoproterozoic rocks. In this study, we report an integrated study of zircon U–Pb age, major and trace element data and Sr–Nd–Hf isotope compositions for gray gneisses from the Houhe complex in the northwestern part of the Yangtze Block. Zircon U–Pb dating yields a weighted mean 207Pb/206Pb age of 2081±9Ma for a gneiss. This age is interpreted as the formation age of the Houhe complex and thus the Houhe complex represents the oldest rocks found in the western part of the Yangtze Block. The gray gneisses from the Houhe complex range in SiO2 contents from 58.63% to 68.59% and Na2O from 3.88% to 5.28%, and have relatively high Fe2O3 contents of 2.86–6.69%, Al2O3 of 16.01–18.88%, and MgO of 0.97–2.65%. These rocks show low Sr (149–390ppm), Cr (9.07–45.1ppm) and Ni (4.97–21.3ppm) contents, but high Y (12.9–32.7ppm) and Yb (0.95–2.25ppm). They are characterized by a relative enrichment in LILEs and LREEs, but a depletion in HFSEs. These features are similar to those of calc-alkaline granitoids, suggesting that their formation might be related to a subduction-related process or remelting of preexisted arc rocks. Compiled age spectra of Archean to Paleoproterozoic zircon grains reveal that the western and eastern parts of the Yangtze Block have similar Archean and early Paleoproterozoic age ranges, indicative of the occurrence of an old continental nucleus in both parts. On the other hand, there are large amounts of ca. 2050–2400Ma zircon grains revealed in the western part of the Yangtze Block, implying that there might be a microcontinent with an active-type continental margin during the Paleoproterozoic times in the western part of the Yangtze Block. Because of the poor outcrops of Archean to Paleoproterozoic rocks in the Yangtze Block, it is no possible to establish the exact nature of such an active margin yet. The occurrence of ca. 2.0Ga khondalitic and metasedimentary rocks has been documented in the eastern part of the Yangtze Block, implying that there might be a passive-type continental margin in the eastern part of the Yangtze Block. At ca. 2.0Ga, the collision between the western microcontinent and the eastern part may have resulted in the final arc-continental collision and the amalgamation of the Yangtze Block. [Copyright &y& Elsevier]

Abstract: TTG rocks are commonly assumed to form by partial melting of oceanic crust during slab subduction or anatexis of thickened lower crust. The two models are tested by an integrated study of geochronology and geochemistry for a composite batholith of Neoproterozoic granitoids (mainly TTG-like) from the Yangtze Gorge in South China. Zircon U–Pb dating indicates that all granitoids crystallized in a period of 820 to 800 Ma. Zircon δ 18O values are 4.85 to 6.84‰, suggesting limited contributions from supracrustal materials to magma sources. Zircon ε Hf(t) values for syn-magmatic domains range from −3.6 to −29.7, concordant with whole-rock ε Nd(t) values of −2.1 to −21.3. Correspondingly, zircon Hf model ages are 2.09 to 3.16 Ga, suggesting their derivation from ancient crust of Paleoproterozoic to Archean ages. TTG-like rocks contain inherited zircon cores that yield two groups of U–Pb ages at Paleoproterozoic (1.8 to 2.0 Ga) and Archean (~2.9 Ga), respectively. They show variable ε Hf(t) values from −48.4 to −33.4. Because the Neoproterozoic magmatism leads to variable increases of ε Hf(t) values for some inherited cores, only the lowest ε Hf(t) values for the inherited cores are assumed to represent the original Hf isotopes in source rocks. The screened results are consistent with those for Archean TTG gneiss and migmatite in this region. In addition, the TTG-like rocks have lower ε Nd(t) and ε Hf(t) values, higher Sr/Y and (La/Yb)N ratios and stronger depletion in Nb, Ta and Ti than the other granitoids. Two alternative scenarios are proposed to account for their petrogenesis: (1) anatexis of Archean and Paleoproterozoic mafic crust in the stable depths of garnet and amphibole, respectively; or (2) anatexis of Archean TTG and Paleoproterozoic mafic rocks in amphibole-stable depths. Nevertheless, the second one is preferred because the inherited zircons with Paleoproterozoic to Archean U–Pb ages are preserved in the TTG-like rocks, which is incompatible with high temperatures to generate the primary TTG magmas. Therefore, the Neoproterozoic TTG-like rocks were derived from the anatexis of ancient non-thickened lower crust, with the TTG features inheriting from their source. [Copyright &y& Elsevier]

Abstract: Herein we present new U–Pb zircon ages, whole-rock geochemical data and Nd–Sr–Hf isotopic data for an Early Palaeozoic monzogranite batholith from the Tengchong–Baoshan Block, Western Yunnan Province, China. Mineralogical and geochemical features suggest that this granitoid is a high-K, calc-alkaline, I-type granite. SHRIMP and laser ablation ICP-MS (LA-ICP-MS) analysis of zircon yields ages of between 499±5Ma and 502±5Ma, for three samples from the batholith. The monzogranite is characterised by high initial 87Sr/86Sr (0.7132–0.7144), negative ε Nd(t) (−9.7 to −9.40) and ε Hf(t) (−10 to −13.1), and is interpreted to derive from remelting of pre-existing Palaeoproterozoic, high-K, metabasaltic rocks of the upper crust. The granitoid magma underwent extensive fractional crystallisation of biotite±hornblende, ilmenite, titanite, K-feldspar and plagioclase during emplacement. The crystallisation temperature of the magma lies in the range 633–733°C, however, there is no evidence to suggest crustal assimilation occurred during its ascent. Like the ∼500Ma, I-type granite of this study, there occur numerous granitoid rocks of Early Palaeozoic age (490–470Ma) in adjacent regions across the entire Tengchong–Baoshan Block (). This episode of plutonism is coeval with the widespread granitoid magmatism found throughout the Indian Plate and the Himalayan Orogenic Belt that are both subordinate parts of the ancient, Gondwana supercontinent. We infer, therefore, that the Tengchong–Baoshan Block may also have formed part of Gondwana, and that it separated from this supercontinent along with other crustal blocks during the Late Palaeozoic. Moreover, based on the findings of this study, we document the occurrence of arc-related magmatism in the Tengchong–Baoshan Block during the late Palaeoproterozoic. [Copyright &y& Elsevier]

Abstract: A combined study of zircon U–Pb and Lu–Hf isotopes, mineral O isotopes, whole-rock elements and Sr–Nd isotopes was carried out for Neoproterozoic volcanics and granites from the eastern part of the Jiangnan Orogen in South China. The results are used to test controversial models of petrogenesis (plume-rift, slab-arc and plate-rift) for similar ages of magmatic rocks in South China. Zircon U–Pb dating yields two groups of ages at ∼780 and ∼825Ma, respectively, corresponding to syn-rift and pre-rift magmatic events in response to supercontinental rifting. Both volcanic and granitic rocks show trace element features similar to those of arc-derived igneous rocks, but with more significant enrichment in large ion lithospheric elements relative to oceanic arc basalts. They have positive ɛ Hf(t) values of 3.6–6.3 for zircons, with Hf model ages of 1.12–1.21Ga. This indicates reworking of late Mesoproterozoic juvenile crust for the origin of the Neoproterozoic magmatic rocks. Thus, oceanic arc magmatism would occur in the late Mesoproterozoic, with remarkable production of juvenile crust at the southeastern margin of the Yangtze Block. Because of the tectonic collapse of arc–continent collision orogen in the pre-rift stage, S-type magmatic rocks were generated by burial and anatexis of juvenile arc-derived crust to form the pre-rift episode of granodiorites and volcanics. In the syn-rift stage, the volcanics formed by reworking of arc-derived sedimentary rocks whereas the granite was generated by melting of the pre-rift igneous rocks. Emplacement of evolved felsic magmas along the rift tectonic zone would cause subsolidus high-T meteoric-hydrothermal alteration, resulting in varying δ 18O values for minerals from the volcanic and granitic rocks. Therefore, the plate-rift model is advanced to account for petrogenesis of all Neoproterozoic magmatic rocks in South China, with lithospheric extsension as the driving force of supercontinental rifting. Partial melting due to arc-continent collision, orogenic collapse and supercontinental rifting is also proposed as a mechanism for the chemical differentiation of continental crust towards the felsic composition. [Copyright &y& Elsevier]

Abstract: An integrated study of geochronology and geochemistry was carried out for Neoproterozoic intrusions at Xiaofeng in the Yangtze Gorge. The results are used to provide constraints on their origin, with potential resolution to hotly debated models concerning the source and process of contemporaneous igneous rocks in South China. The Xiaofeng intrusions are composed of felsic–mafic dykes and their wall-rock granitoids in an area of <10km2. They show intrusion relationship to TTG rocks of the Archean Kongling Complex. Zircon U–Pb dating indicates that the dykes and granitoids were crystallized almost contemporaneously at 800±3Ma. They share similar distribution patterns of REE and trace elements, i.e. enrichment in LILE and LREE but depletion in HFSE. The dykes have whole-rock ɛ Nd(t) values of −9.9 to −6.4 and zircon ɛ Hf(t) values of about −12.9 to −9.0, and the granitoids have whole-rock ɛ Nd(t) values of −10.6 to −9.2 and zircon ɛ Hf(t) values of −10.5 to −8.3. Furthermore, their zircon Hf model ages are similar to each other, from 2.8 to 3.2Ga. These results indicate that they both are derived from reworking of Mesoarchean lithosphere, with the difference only in major element composition. Zircon has δ18O values of 5.4–6.8‰ for them, typical for I-type granite. Mineral O isotopes indicate small-scale high-T water–rock interaction during the intrusion of the dykes into the granitoids. No growth of juvenile crust during the middle Neoproterozoic magmatism is identified to occur in the Xiaofeng intrusions. Thus, neither mantle plume nor oceanic arc is responsible for their origin, ruling out the plume-rift and slab-arc models for their petrogenesis. Instead, the Neoproterozoic anatexis of the Archean lithosphere can be explained by the tectonic collapse of a thickened intracontinental orogen that formed by Paleoproterozoic arc-continent collision to the Archean Kongling Complex, but it became molten due to lithospheric extension in response to plate reorganization prior to breakup of the supercontinent Rodinia. This provides a positive test to the plate-rift model for their petrogenesis. [Copyright &y& Elsevier]