Northeastern Jiangxi Province Research Articles

The Petrogenesis of the Gaohushan A-Type Granite from the Northeastern Jiangxi Province and Its Metallogenic Implication

The Taqian–Zhuxi–Fuchun metallogenic belt in northeastern Jiangxi Province contains significant ore deposits that are closely associated with the Gaohushan granites. The Gaohushan granites predominantly consist of two-mica granites and have been dated using zircon U-Pb isotopic dating to be 129.4 ± 1.9 Ma (MSWD = 3.8). These granites have high SiO2, ranging from 73.79% to 76.04% and low CaO and MgO contents (ranging from 0.24% to 0.59% and from 0.03% to 0.1%, respectively). The Gaohushan granites also exhibit high FeOT/MgO ratios from 9.00 to 27.55 with an average of 17.55. The total alkali contents (Na2O + K2O) range from 7.08% to 8.43%, and the K2O/Na2O ratios range from 1.07 to 2.00 with an average of 1.47. These rocks are peraluminous series with A/CNK ratios (or ASI index) ranging from 1.19 to 1.47 and an average of 1.30. The Gaohushan granites have low rare earth element (REE) contents (∑REE = 2.33~23.50) with strongly negative Eu anomalies (δEu from 0.02 to 0.32) and a distinctive differentiation between heavy rare earth elements (HREEs) and light rare earth elements (LREEs) (LREE/HREE = 1.99~7.79). The normalized distribution pattern of REE in Gaohushan granite exhibits a right-dipping feature classified A-type; these rocks range from 1.06 to 2.71. The spider diagram shows that these rocks are characterized by depletion of Ba, Th, La, Sr, Nd, and Ti and enrichment of Rb, U, Ta, Nb, and P. The Gaohushan granites are classified as A-type granite and were emplaced during an anorogenic extensional event that occurred in the late Yanshannian period, driven by mantle-derived magma underplating. It is these granites or their analogues that have the potential for hosting tungsten, tin, niobium, and tantalum deposits, making them a promising target for mineral exploration.

Identification of Baihesi aluminous A-type granite: Magmatic response to the onset of Cretaceous extension in eastern Jiangnan Massif, South China

The Cretaceous lithospheric extension in South China is very distinct and expressed by systematic extension-related geological records which are concentrated in the coastal terrane, Shi-Hang Rift, and Jiangnan Massif. The Cretaceous extension in the coastal terrane and Shi-Hang Rift began almost simultaneously during 145–140 Ma, while there is a lack of reliable magmatic indication for tectonic extension in the Jiangnan Massif during 145–140 Ma. This paper reports a newly discovered Baihesi granite with a concordant age of 142.52 ± 0.57 Ma (MSWD = 1.2) on the southeast margin of the eastern Jiangnan Massif with evidence from petrology, geochronology, petrochemistry and Hf isotopes. The Baihesi granite is a monzogranite and classified as a peraluminous, high-K calc-alkaline series. The trace element compositions are characterized by relatively flat rare earth element patterns; strong depletion of Eu; slightly enriched light rare earth elements; enrichment of Cs, Rb, Th, U, and Pb; and depletion of Ba, Sr, P, and Ti. Combined with other petrochemistry characteristics, such as high SiO2 content, high differentiation index, low Zr/Hf and Nb/Ta ratios, low ratio between light and heavy REEs, low P2O5 content, and high zirconium saturation temperature, Baihesi granite is proven to be highly evolved aluminous A-type granite. The εHf(t) values of Baihesi granite range from −5.57 to −2.37, with two-stage model ages (TDM2) ranging from 1,551 to 1,345 Ma, suggesting a similar source to Neoproterozoic arc-related magmatic rocks in the Shuangqiaoshan Group. We argue that Baihesi granite has originated mainly from partial melting of a reworked juvenile crust related to Neoproterozoic arc-related magmatism in the Jiangnan Massif, which was controlled by subduction along the South China active continental margin. Furthermore, we constrain the onset of Cretaceous extension in the eastern Jiangnan Massif to be 145–140 Ma and highlight the Early Cretaceous reactivation of the northeastern Jiangxi Province fault zone and the structural inheritance in intraplate tectonics.

Application of principal component analysis and a spectrum-area fractal model to identify geochemical anomalies associated with vanadium mineralization in northeastern Jiangxi Province, South China

The Jiujiang region in northeastern Jiangxi Province is known for hosting many black shale-type vanadium deposits, which are mainly found in the Cambrian Hetang Formation and Sinian Piyuancun Formation. In this paper, based on stream sediment data, principal component analysis (PCA) and spectrum–area (S–A) fractal modelling are used to identify geochemical anomalies associated with vanadium (V) mineralization. First, a dataset containing 957 samples of stream sediments with 39 elements was processed using correlation analysis and cluster analysis to find the closest V-related elements, and Ag and Cd were obtained. Secondly, the raster maps of V, Ag and Cd were created using multifractal inverse distance-weighted interpolation. PCA was then employed to combine the concentration values of V, Ag and Cd into a single variable representing the internal relationships among the three elements. Finally, S–A analysis was used to decompose the first component pattern obtained through PCA and to extract anomalies from the complex background. The results show that the known V deposits are located within highly anomalous areas, which are well corelated with the distribution of black shales of the Hetang and Piyuancun Formations. It is suggested that the northeastern part of Jiangxi Province potentially hosts undiscovered V deposits, and the identified anomalies could be further used to guide mineral exploration.Thematic collection:This article is part of the Applications of Innovations in Geochemical Data Analysis collection available at:https://www.lyellcollection.org/cc/applications-of-innovations-in-geochemical-data-analysis

3D mineral prospectivity modeling based on machine learning: A case study of the Zhuxi tungsten deposit in northeastern Jiangxi Province, South China

The Zhuxi tungsten deposit is the largest tungsten deposit in the world. A mineral prospectivity analysis of the areas surrounding this deposit has the potential to identify further resources, and thus, it is important to conduct such an analysis. Therefore, a mineral prospectivity was performed on the results of completed 3D geological modeling of the area and 3D inversion of gravity, magnetic, magnetotelluric and broadband seismic data. The anomalous density, susceptibility, resistivity, P-wave velocity and lithology derived from geophysical and geological modeling were constructed on consistent grids. Then, based on the locations of known deposits, the features of the ore-bearing and ore-free zones were extracted. Then, three kinds of machine learning algorithms, namely K-nearest neighbour, back-propagation neural network and support vector machine, were trained using the extracted features. Then, prediction was applied to the 3D data for the whole area, and multiple groups of 3D mineral prospectivity modeling were obtained. By a comparison of stage percentage and the analysis of the capture efficiency diagram, the support vector machine model without lithology captures the largest number of known ore-bearing samples (75.69%) with the least voxels (2.07%), which was highly consistent with the actual geological conditions selected for the classification of prospective areas. The results show that this type of machine learning-based mineral prospectivity modeling, which uses Earth models obtained from the 3D inversion of multiple geophysical data sets and 3D geological modeling, can advance 3D mineral prediction, and thus will greatly improve the efficiency in discovering further ore deposits.

In-situ U-Pb geochronology and trace element analysis for the scheelite and apatite from the deep seated stratiform-like W(Cu) ore of the Zhuxi tungsten deposit, northeastern Jiangxi Province

钨和铜由于地球化学行为存在明显差异，导致二者通常很难同时发生大规模的成矿作用。然而，江南钨矿带却出现了以石门寺和朱溪为代表的钨（铜）矿床。本文对朱溪钨（铜）矿床中最为重要的铜矿化作用开展了研究，即对形成于新元古代浅变质岩与古生代碳酸盐岩不整合界面附近的似层状钨（铜）矿体进行了精细的矿物学微区原位测试分析。厘定了朱溪矿床深部似层状钨（铜）矿体中铜矿化的形成时代为150.2±2.4Ma，与朱溪矿床的钨矿化时代及钨矿化相关岩体的成岩时代近于一致；揭示了深部似层状钨（铜）矿体中白钨矿、磷灰石的形成与朱溪矿床成矿相关岩浆高程度结晶分异形成的残余岩浆热液流体相关；结合朱溪矿床高分异残余岩浆（流体）具有高度还原的特征，初步提出朱溪矿床成矿过程中，钨来自于高分异残余岩浆热液流体，而铜来自于岩浆热液流体对基底地层中铜元素的萃取。;Due to the obvious differences in geochemical behavior for tungsten and copper in magmatic systems, it is usually difficult to occurring large-scale Cu- and W-mineralization at the same time. However, tungsten (copper) deposits represented by Shimensi and Zhuxi deposits appear in the Jiangnan tungsten belt. This study focuses on the most important copper mineralization occurred in the Zhuxi W (Cu) deposit, which formed the stratiform-like W(Cu) ore body near the unconformity interface between the Neoproterozoic metamorphic rock and the Paleozoic carbonate rock. In situ micro-zone analysis have been performed on the scheelite and apatite from the stratiform-like W(Cu) ore body. The LA-ICP-MS U-Pb data on the apatite show a Lower intercept age of 150.2±2.4Ma on the Tera-Wasserburg concordia diagrams, which represents the copper mineralization in the stratiform-like W(Cu) ore body and is closely consistent with the tungsten mineralization age and the diagenetic age of the granitic rocks associated with tungsten mineralization. The geochemical characteristics of scheelite and apatite reveal that the formation of scheelite and apatite grains in the stratiform-like W(Cu) ore body is genetically associated with the residual magmatic hydrothermal fluids formed from the highly fractionated magma system that induced the tungsten mineralization of the Zhuxi deposit. In view of the highly fractionated residual magma system of the Zhuxi deposit is characterized by highly reductive features. This study preliminarily proposed that during the mineralization process of the Zhuxi deposit, tungsten is derived from the highly fractionated magmatic system, while copper comes from the extraction of the basement strata by the magmatic hydrothermal fluid.

Fluid inclusion and stable isotope constraints on the genesis of the world-class Zhuxi W(Cu) skarn deposit in South China

Scheelite mineralization accompanied by traces of chalcopyrite occurs in skarn systems in the giant Zhuxi deposit in the Taqian area, Northeastern Jiangxi province, South China. Three paragenetic stages of skarn with ore deposition have been recognized: the prograde skarn, retrograde skarn and hydrothermal quartz-sulfide stages. Microthermometer data showed that the prograde skarn were formed at relatively high temperatures (450–>500 °C) and pressures (0.97–1.38 kbars) and low oxidation to weak reduction conditions. The Raman microprobe data demonstrated that the fluid of the stage was H2O–NaCl/KCl/CaCl2 ± CH4/C2H4 system. The retrograde skarn alteration formed at 1.24 kbars and relatively medium temperatures (280–320 °C), and the ore-forming fluid was H2O–NaCl/KCl/CaCl2 system. During the hydrothermal quartz-sulfide stage, the fluids were methane-bearing aqueous, low-salinity (0.9–8.0 wt% NaCleqv) and low homogeneous temperature (160–240 °C). Correspondingly, the minimum fluid pressures were evaluated between 75 and 252 bars.The H- and O-isotopic values from the prograde and retrograde stages implied that the mineralizing fluids were derived principally from magmatic water. The mineralizing fluids in the quartz-sulfide hydrothermal stages were mingled with magmatic water with some meteoric water as well as minor contributions of wall rocks. The sulfur and lead isotopes indicated that ore-forming materials including sulfur, lead, copper, zinc and iron in the Zhuxi deposit were derived from local magmatic and sedimentary sources. Geological, fluid inclusion and isotopic data supported that the Zhuxi deposit is a typical skarn-type W(Cu) deposit related to ilmenite-series granitic rocks and formed in a compressional tectonic environment.

Muscovite 40Ar−39Ar age and its geological significance in Zhuxi W(Cu) deposit, northeastern Jiangxi

The Zhuxi W(Cu) skarn deposit, the world’s largest tungsten deposit is newly discovered in Jingdezhen city, northeastern Jiangxi province, China. It mainly occurs near the contact zone between the Yanshanian granites and the Late Paleozoic carbonate rocks. Three types of mineralization including skarn type, altered granite type and quartz vein-veinlet type orebodies have been observed. In this study, the 40Ar−39Ar age of hydrothermal muscovite coexisting with copper mineralization in the altered granite type orebody formed near the unconformity interface is determined by step-heating technology using CO2 laser. The plateau age, isochron age, and inverse isochron age of muscovite are (147.39±0.94) Ma, (147.2±1.5) Ma, and (147.1±1.5) Ma, respectively. These ages are almost identical to the ages of ore-related granite and other mineralization types in the Zhuxi W(Cu) deposit, indicating that the Cu mineralizations occurred at the shallow depth and near the unconformity interface are contemporaneous during the Late Jurassic. This further suggested that the acompanied W and Cu mineralization in the Zhuxi W(Cu) deposit which may be controlled by the magma source is enriched in both W and Cu.

Spatiotemporal Variations in Agricultural Flooding in Middle and Lower Reaches of Yangtze River from 1970 to 2018

Agricultural floods in the middle and lower reaches of the Yangtze River, known as the “land of fish and rice” in China, have increased both in areal coverage and frequency over the past 50 years, presenting a grave challenge to sustainable development and food security in the region. Studying the spatiotemporal variation characteristics of agricultural floods in this region is thus important for providing a scientific basis for regional flood control and disaster mitigation. We used variation trend analyses, Mann–Kendall tests, wavelet analyses, and center of gravity modeling to study spatiotemporal changes in agricultural floods in the study area, based on agricultural flood indicators. Changes in agricultural flood frequency showed an overall increasing trend. The frequency of floods changed abruptly in 1990, with the average frequency of floods per station increasing by 0.2086/year from 1991 through 2018, characterized by multiple time-scale changes. The time scale of 17 years had three low–high cycles, that of eight years had six, and that of four years had 13. Agricultural floods in the study area were concentrated in the southern Yangtze River and mainly occurred in northeastern Jiangxi Province and the southeastern Zhejiang Province. The area with high agricultural flood indices increased. Agricultural floods were closely related to the Yangtze River and the direction of the gravity center of agricultural floods was similar to that of the river. Affected by precipitation intensity and frequency, the gravity center fluctuated greatly and generally alternated from southwest to northeast.

A lead isotope study of the fourth century B.C. bronze artifacts excavated from Guozhuang Chu graveyard in Shangcai County, Henan Province, Central China

MC-ICP-MS analysis was conducted on fourteen bronze artifacts of the early Warring States Period (475–376 B.C.), excavated from Guozhuang Chu graveyard in Shangcai County, Henan Province, central China. The lead isotope ratios conform to the characteristics of common lead. Complex lead ore sources suggest Northeastern Jiangxi Province as the main sourcing area, while Southwestern Henan Province may also provide a small amount of lead ore. Some lead ore may also be derived from other countries, such as Ba, Qi, or Yan States. A further study shows that during the Warring States Period, the bronze cultural spheres around Jin, Qin, Chu, Qi, Yan, and Ba kingdoms share a distinctive feature based on lead isotope ratios. In the case of Chu, there were differences between border areas and king city regions, but on the whole, the difference was small. In addition, some raw material exchange may exist between the bronze cultural spheres of Chu, Jin, Qi, and Ba.

Geochronology and geochemistry of the granites from the Zhuxi W-Cu ore deposit in South China: Implication for petrogenesis, geodynamical setting and mineralization

The giant Zhuxi tungsten deposit is located in the Taqian-Fuchun Ore Belt in northeastern Jiangxi province, and genetically associated with the Zhuxi granitic stocks and dykes. Three mineralization-related granites including granite porphyry dykes (GP), biotite granitic stocks (BG), and white granitic dykes (WG), were identified in the Zhuxi deposit. SHRIMP zircon U–Pb analysis for the three granitic rocks present ages ranging from 153.5±1.0Ma to 150.4±1.0Ma. The BG mainly contains quartz, microcline, albite, biotite and muscovite with minor accessory minerals including zircon, apatite, monazite, Ti/Fe oxides, and dolerite. However, the WG is mainly composed of quartz, microcline and albite with minor muscovite and accessory minerals. The GP is a medium-grained porphyritic granite and its phenocrysts include quartz, alkali feldspar, muscovite and plagioclase. All the Zhuxi granites have high SiO2 content (71.97wt%–81.19wt%) and total alkali (3.25wt%–9.42wt%), and their valid aluminum saturation index (ASI) values show a wide range of 1.03 to 2.49. High Rb/Sr ratios, low Sr content (<50ppm) and markedly negative Eu anomalies of GP, WG and BG demonstrated that the Zhuxi granites are highly fractioned and intensive crystal differentiated. Because they display the features of both I- and S-types granites, they were confirmed to be I-S transform-type granites. Whole rock εNd(t) and zircon εHf(t) values fall into the ranges of −6.98 to −11.97, and −3.1 to −11.5, and the Nd (TDM2) and Hf two-stage model ages (TDMc) are 1.51–1.92Ga and 1.42–2.01Ga, respectively. Geochemical and isotopic data suggest that these highly fractionated I–S transform-type granites were originated from magmas which showed affinity with the Proterozoic continent and the Shuangqiaoshan Group and little mantle contribution was involved during the generation of Zhuxi granitic rocks. Extreme fractional crystallization resulted in further enrichment of tungsten in the evolved granitic magma. New data, presented together with previously published data, suggest that the Zhuxi granitic complex was likely to be formed during lithospheric compression setting during the late Jurassic to early Cretaceous. The biotite granite stock predominately contributed to the production of skarn alteration and mineralization, followed by the white granite dyke; the granite porphyry dykes have little effect.

Petrogenesis of Ore‐Related Granodiorite Porphyry in the Jiande Copper Deposit, SE China: Implications for the Tectonic Setting and Mineralization

AbstractAdakitic rocks and related Cu–Au mineralization are widespread along eastern Jiangnan Orogen in South China. Previous studies have mainly concentrated on those in the Dexing area in northeastern Jiangxi Province, but information is lacking on the genesis and setting of those in northwestern Zhejiang Province. The Jiande copper deposit is located in the suture zone between the Yangtze and Cathaysia blocks of South China. This paper presents systematic LA–ICP–MS zircon U–Pb dating and element and Sr–Nd–Hf isotopic data of the Jiande granodiorite porphyry. Zircon dating showed that the Jiande granodiorite porphyry was produced during the Middle Jurassic (ca. 161 Ma). The Jiande granodiorite porphyry is characterized by adakitic geochemical affinities with high Sr/Y and LaN/YbN ratios but low Y and Yb contents. The absence of a negative Eu anomaly, extreme depletion in Y and Yb, relatively low MgO contents, and relatively high 207Pb/204Pb ratios, indicated that the Jiande granodiorite porphyry was likely derived from partial melting of the thickened lower continental crust. In addition, the Jiande granodiorite porphyry shows arc magma geochemical features (e.g., Nb, Ta and Ti depletion), with bulk Earth‐like εNd (t) values (−2.89 to −1.92), εHf (t) values (−0.6 to +2.8), and initial 87Sr/86Sr (0.7078 to 0.7105). However, a non‐arc setting in the Middle Jurassic is indicated by the absence of arc rocks and the presence of rifting‐related igneous rock associations in the interior of South China. Combined with the regional Neoproterozoic Jiangnan Orogeny, it indicates that these arc magma geochemical features are possibly inherited from the Neoproterozoic juvenile continental crust formed by the ancient oceanic crust subduction along the Jiangnan Orogen. The geodynamic environment that is responsible for the development of the Middle Jurassic Jiande granodiorite porphyry is likely a localized intra‐continental extensional environment along the NE‐trending Jiangshan‐Shaoxing Deep Fault as a tectonic response to far‐field stress at the margins of the rigid South China Plate during the early stage of the paleo‐Pacific plate subduction. In terms of Cu mineralization, we suggest that the metal Cu was released from the subducted oceanic slab and reserved in the juvenile crust during Neoproterozoic subduction along the eastern Jiangnan Orogen region. Partial melting of the Cu rich Neoproterozoic juvenile crust during the Middle Jurassic time in the Jiande area caused the formation of adakitic rocks and the Cu deposit.

Tectonic discrimination of chromian spinels, olivines and pyroxenes in the Northeastern Jiangxi Province ophiolite, South China

The peridotites of the Northeastern Jiangxi Province Ophiolite (NJO), including dunite, harzburgite and clinopyroxene-bearing harzburgite, are strongly altered under serpentinization, except for minor aggregations of partially-altered olivines, chromian spinels and pyroxenes. The forsterite content of olivines in dunites (Fo 93.6) is slightly higher than in harzburgites (Fo 91.4). Chromian spinels in harzburgites and dunites are very refractory, with restricted chemical compositions of high-Cr varieties. The unaltered cores of chromian spinels have low Al2O3 and TiO2 content, and display a large range of Mg# (100× [Mg/(Mg + Fe)], 41–64) and Cr# (100× [Cr/(Cr + Al)], 53–83) values, suggesting that the peridotites originated from a highly-depleted mantle. The spinels plotted in “olivine-spinel mantle array” (OSMA) diagram and Cr# versus. Mg# diagram both indicate the peridotite of NJO experienced a >25 % partial melting. The positive correlation between the Cr# and the TiO2 content probably resulted from the reaction between boninitic melt and mantle peridotite, as a consequence of melt-mantle interaction within the arc setting. The oxygen fugacity (ƒO2), calculated using chromian spinel-olivine pairs, indicates that the peridotites in the NJO were formed under relatively low oxidizing conditions quite different from those commonly found in supra-subductions zones (SSZ). This might be explained by the reaction between fore-arc magmas and residual mantle in a back-arc oceanic basin during a rapid subduction process. The Neoproterozoic subduction between the Yangtze and Cathaysia blocks was therefore probably rapid, and the addition of water and other volatiles to the mantle wedge beneath the island arc would have enhanced melting, leading to the production of highly depleted boninitic melts.

Fluid inclusion and H–O–S–Pb isotopic evidence for the Dongxiang Manto-type copper deposit, South China

The Dongxiang copper deposit is located in northeastern Jiangxi Province, South China. Ore bodies in the Zishan Formation of this province are primarily stratoid and lentiform and show a close spatial association with Jurassic intrusive rocks. The current debates generally concentrate on whether the Dongxiang copper deposit is a Carboniferous sedimentary deposit or, alternatively, a Jurassic porphyry–skarn deposit. Three stages of mineralization can be observed in this deposit: the pre-ore, main ore, and post-ore stages. The massive sulfide ore bodies are identified as the main ore stage, whereas the pyrite-quartz veins and barren quartz veins are identified as pre-ore and post-ore stages, respectively. Three fluid inclusion types were recognized: two-phase vapor-rich fluid inclusions (type 1), two-phase liquid-rich fluid inclusions (type 2), and halite-bearing fluid inclusions (type 3). All three of these types of inclusions are present in the main copper mineralization stage, but only type 2 inclusions occur in both the pre-ore and post-ore stages. Type 2 inclusions in the pre-ore stage display homogenization temperatures (Th) of 349–392°C, with salinities of 1.4–8.1wt.% NaCl equivalent. In the main ore stage, types 1 and 3 inclusions show similar Th at 289–346°C and 273–348°C but contrasting salinities of 0.4–4.5 and 29.4–41.9wt.% NaCl equivalent, respectively. In the post-ore stage, type 2 inclusions have Th of 144–228°C and salinities of 0.4–6.0wt.% NaCl equivalent. The coexisting types 1 and 3 inclusions in the main ore stage have similar Th ranges but contrasting salinities, which indicates that fluid boiling occurred. The determined hydrogen and oxygen isotopic values for these fluids (δD from −42‰ to −69‰; δ18OH2O 5.04‰ to 9.01‰), based on analysis of fluid inclusions and host quartz, imply that the inferred ore fluids were principally derived from magmatic water. The lead isotopic compositions of sulfides from the ores and plagioclases from the adjacent porphyry indicate that they share a common origin. The sulfides from the ores show δ34S values of 0.3–3.2‰, also suggests a magmatic source. As the fluid inclusions and isotopic compositions strongly suggest a magmatic origin, this argues against a SEDEX origin for this deposit. In addition, the presence of stratoid and lentiform ore bodies and the absence of skarn alteration minerals suggest that the Dongxiang copper deposit is best described as a Manto-type rather than a porphyry–skarn deposit.

Petrogenesis Significance of Chromian Spinels from Northeastern Jiangxi Province Ophiolite (NEJXO), China: Paleogeodynamic Implications

Petrogenesis Significance of Chromian Spinels from Northeastern Jiangxi Province Ophiolite (NEJXO), China: Paleogeodynamic Implications

The geological significance of a Paleozoic mafic granulite found in the Yiyang area of northeastern Jiangxi Province

A mafic granulite has been found in southern Yiyang county in northeastern Jiangxi Province. This granulite has a mineral assemblage of garnet+plagioclase+hypersthene+biotite+magnetite. Based on the composition variation of minerals and relationships among them, pre-peak metamorphism (M1) and peak metamorphism (M2) are recognized. A petrogenetic grid and geothermobarometry measurements yield pre-peak metamorphic conditions of 830-870℃ and ~1.0 GPa, and peak metamorphic conditions of 850-900℃ and 0.7-0.8 GPa, suggesting a near isothermal decompression clockwise PTt path. LA ICPMS zircon U-Pb dating indicates that granulite facies metamorphism occurred about 436 Ma, and its protolith was possibly formed in the early Neoproterozoic. Coupled with available data, we suggest that early Paleozoic (Caledonian) high-grade metamorphism in the Cathaysia Block is related to collisional orogeny, which probably results from the collision-compression between the Yangtze Block and Eastern Gondwana.

Petrogenesis and magmatic evolution of ∼130 Ma A-type granites in Southeast China

A number of Late Mesozoic (∼130Ma) A-type granitic plutons have been identified in Southeast China. Here we investigate the petrogenesis of one of these granitic plutons in Southeast China, the Sanqingshan–Damaoshan (SD) granites in northeastern Jiangxi Province, using zircon U–Pb geochronology, Hf isotopic analyses, and major and trace element analyses. The SD granites are metaluminous to weakly peraluminous and show typical A-type affinity, which is characterized by high SiO2, Na2O+K2O, rare earth element (REE), high field strength element (HFSE) contents, Ga/Al and Fe# [FeOt/(FeOt+MgO)] values. Zircon grains from the SD granites and some other ∼130Ma A-type granites commonly contain oscillatory zoning “cores” surrounded by unzoned to weakly zoned “rims”. Detailed studies of zircons from the SD granites show that “rims” are enriched in LREE, Th and U compared with “cores”. Chondrite-normalized REE patterns of the “cores” increase steeply from La to Lu and show pronounced Ce and Eu anomalies, while REE patterns of the “rims” display higher REE abundances with flatter LREE patterns and moderate Ce anomalies. Nevertheless, Lu–Hf isotopic analyses and Ti-in zircon thermometer show similar characteristics between “rims” and “cores”, indicating that the “rims” may crystallize under the effect of internal magmatic hydrothermal fluids. U-rich “rims” are more susceptible to Pb loss caused by self-irradiation, which may lead to significant younger U–Pb ages. As a result, U–Pb ages of zircon “cores” (∼130Ma) represent crystallization ages of the SD granites. εHf(t) values of zircon grains from the SD granites are between −6.4 and −0.4 with Mesoproterozoic model ages (T2DM) ranging from 1.22 to 1.59Ga, suggesting that the granites may be formed by partial melting of Proterozoic basement. Compared with other adjacent ∼130Ma A-type granitic plutons in SE China, the SD granites have similar geochemical characteristics and Hf isotopic compositions to those of Xiangshan, Daqiaowu, Yangmeiwan, and Tongshan granites, but different from the Baijuhuajian granite. εHf(t) values of the Baijuhuajian granites are higher than other granites, indicating significant participation of juvenile materials. These ∼130Ma A-type granites indicate a back-arc extension setting due to the roll-back of paleo-Pacific plate, where the crust and lithospheric mantle became progressively thinned. The upwelling of asthenosphere triggered the partial melting of crustal rocks and generated the Sanqingshan–Damaoshan, Tongshan, Daqiaowu and Yangmeiwan granitic plutons. With ongoing back-arc extension and increased subduction angle during the roll-back of subducted paleo-Pacific slab, the back-arc extension gradually intensified, resulting in significant additions of mantle juvenile materials to the crustal magma and the formation of the Baijuhuajian granite.

Magmatic–hydrothermal rare-element mineralization in the Songshugang granite (northeastern Jiangxi, China): Insights from an electron-microprobe study of Nb–Ta–Zr minerals

The Songshugang granite, hidden in the Sinian metasedimentary stratum, is a highly evolved rare-element granite in northeastern Jiangxi province, South China. The samples were systematically taken from the CK-102 drill hole at the depth of 171–423m. Four types of rocks were divided from the bottom upwards: topaz albite granite as the main body, greisen nodules, topaz K-feldspar granite and pegmatite layer. Electron-microprobe study reveals that the rare-element minerals of the Songshugang granite are very different from those of other rare-element granites. Mn# [Mn/(Fe+Mn)] and Ta# [Ta/(Nb+Ta)] of columbite-group minerals and Hf# [Hf/(Zr+Hf)] of zircon are nearly constant within each type of rocks. However, back-scattered electron imaging revealed that Nb–Ta oxides and zircon of the Songshugang granite, especially those of topaz albite granite, topaz K-feldspar granite and greisen, are commonly characterized by a specific two-stage texture on the crystal scale. The early-stage Nb–Ta oxide is simply subhedral-shaped columbite-(Fe) (CGM-I) with low Mn# (0.16–0.37) and Ta# (0.05–0.29). Columbite-(Fe) is penetrated by the later-stage tantalite veinlets (CGM-II) or surrounded by complex Nb–Ta–Sn–W mineral assemblages, including tantalite-(Fe), wodginite (sl), cassiterite, and ferberite. Tantalite has wide range of Mn# values (0.15–0.88) from Fe-dominance to Mn-dominance. Wodginite with Ta>Nb has large variable concentrations of W, Sn and Ti. Cassiterite and ferberite are all enriched in Nb and Ta (Nb2O5+Ta2O5 up to 20.12wt.% and 31.42wt.%, respectively), with high Ta# (>0.5). Similar to Nb–Ta oxides and Nb–Ta–Sn–W mineral assemblages, the early-stage zircon is commonly included by the later-stage zircon with sharply boundary. They have contrasting Hf contents, and HfO2 of the later-stage zircon is up to 28.13wt.%. Petrographic features indicate that the early-stage of columbite and zircon were formed in magmatic environment. However, the later-stage of rare-element minerals were influenced by fluxes-enriched fluids. Tantalite, together with wodginite, cassiterite, and ferberite implies a Ta-dominant media. An interstitial fluid-rich melt enriched in Ta and flux at the magmatic–hydrothermal transitional stage is currently a favored model for explaining the later-stage of rare-element mineralization.

Geochemistry, zircon U–Pb and Lu–Hf isotopes of an Early Cretaceous intrusive suite in northeastern Jiangxi Province, South China Block: Implications for petrogenesis, crust/mantle interactions and geodynamic processes

Abstract The Early Cretaceous Tieshan intrusive suite, in northeastern Jiangxi Province along the northern margin of the Eastern Cathaysia Block, is composed of diabase porphyrites, monzodiorites, syenite porphyries, quartz monzonites, monzogranites and granite porphyries. LA–ICPMS zircon U–Pb isotopic analyses reveal that this intrusive complex was emplaced between 142 Ma and 117 Ma. The ~ 135 Ma diabase porphyrites, monzodiorites, and syenite porphyries are characterized by low to moderate SiO2 and MgO contents, with high K2O and total alkaline contents. These rocks exhibit slightly to strongly fractionated REE patterns and upper crust-like multi-element patterns with depletions of Nb, Ta and Ti, and show strongly negative eHf (t) values of − 9.0 to − 11.8. All these patterns are identical to those of the Caiyuan syenites, Huangtuling gabbros in the east, and Lengshuikeng trachyandesites and quartz syenites in the west. These geochemical and zircon Lu–Hf isotopic features indicate that their magmatic precursors were generated by 0.2%–2% partial melting of a phlogopite-bearing enriched subcontinental lithospheric mantle source that was metasomatized by sediments. The ~ 117 Ma quartz monzonite has slightly higher eHf (t) values (− 5.6 to − 8.7) like those of the Honggong syenites, indicating an interaction between the asthenosphere and the lithosphere. The ~ 142–134 Ma granite porphyries and monzogranites are characterized by high SiO2 levels but low concentrations of refractory elements, and show enrichment of LREEs and LILEs, with variable negative anomalies of Nb, Ta, Ti, Sr, P and Ba in multi-element diagrams normalized by primitive mantle. The monzogranite exhibits strongly negative eHf (t) values of − 10.5 to − 13.3 and TDM2 (Hf) values of 1849–2023 Ma, and the granite porphyries display relatively wide eHf (t) values of − 7.2 to − 13.4 and TDM2 (Hf) values of 1645–2043 Ma, indicating that these monzogranites and granite porphyries are highly fractionated granites derived from partial melting of the Paleoproterozoic basement with involvement of enriched mantle-derived magmas or juvenile components, and the primary magma experienced fractionation of K-feldspar, plagioclase, monazite, allanite and zircon during magma ascent and emplacement. The Tieshan intrusive suite, together with the Caiyuan syenites, Huangtuling gabbros, and Lengshuikeng trachyandesites and quartz syenites, forms a highly enriched shoshonitic rock belt in the northeastern margin of the Cathaysia Block. Integrating with previously published data, we propose that the subducted Paleo-Pacific plate extended into the central South China Block in the Middle Jurassic, and experienced slab rollback during the Early Cretaceous.

Porphyry Cu–Au–Mo–epithermal Ag–Pb–Zn–distal hydrothermal Au deposits in the Dexing area, Jiangxi province, East China—A linked ore system

Based on previous studies and detailed field investigations of the Dexing porphyry copper deposit, the Yinshan Ag-Pb-Zn deposit and the Jinshan shear zone – hosted gold deposit in the Dele Jurassic volcanic basin, in the northeastern Jiangxi province, East China, we propose that the three deposits share spatial, temporal and genetic relationships and belong to the same metallogenic system. Dexing is a typical porphyry Cu–Au–Mo deposit in which both ore-forming fluid and metals are derived from the granite porphyry. The Yinshan deposit consists of a porphyry copper ore located in the cupola of a quartz porphyry stock, in the lower part, and Ag–Pb–Zn ore veins in the upper part. The hydrothermal fluids were mainly derived from the magma in the early stages of the mineralizing event and became mixed with meteoric waters in the late stages. Its ore metals are magma-derived. Both the Jinshan base metal veins and the Hamashi, Dongjie and Naikeng quartz vein-type gold deposit are hosted by brittle–ductile structures, which are distal in relation to the porphyry intrusions and were formed by mixed magmatic fluids and meteoric water, whereas the gold was mainly leached from the country rocks (Mesoproterozoic Shuangqiaoshan Group phyllite and schist). The deposits show a distinct spatial arrangement from porphyry Cu, to epithermal Ag–Pb–Zn and distal Au. We suggest a porphyry–epithermal–distal vein ore system model for this group of genetically related mineral deposits. They were formed in a back-arc setting in a Middle Jurassic active continental margin, with magmas derived from the subducted slab.

The Origin of the Wu Dialect as Seen in Historical Records

The areas in which Wu dialects are currently spoken, i.e. Shanghai, Zhejiang Province, Southern Jiangsu Province, Northeastern Jiangxi Province and neighboring areas, were all territories of the Wu and Yue States in the Pre-Qin Period. However, the present Wu dialects are not directly inherited and derived from the native languages spoken in the ancient Wu and Yue areas, as there has been a significant process of language transfer in this area historically. The source of influence mainly comes from Chu language, which led to the development of Eastern Yangtze River dialect first, and later the establishment of Wu dialects in the Tang Dynasty.