Northwestern Jiangxi Research Articles

Geochemical transition from Cretaceous island arc basalt-like to oceanic island basalt-like basaltic rocks in the Jiurui district of the Yangtze Block, South China

The Cretaceous volcanic-sedimentary succession in the Jiurui district of the Yangtze Block contains basalts that are interlayered with fine clastic rocks, conglomerate and breccia strata. Here, we present data of whole-rock40Ar–39Ar dating, major and trace elements, Sr–Nd–Pb isotopes, zircon U–Pb dating and Hf isotopes, and plagioclasetrace element analyses to constrain the petrogenesis and tectonic background of these basaltic rocks,. Two episodiceruptions (ca. 126 Ma and ca. 91 Ma) are recognized, and the early basaltsdisplay evident enriched source characteristics such as high incompatible and low compatible elements, negative Nb, Ta, and Ti, slightly positive Pb anomaly, negative εNd(t) and εHf(t) values, higher (87Sr/86Sr)i, andhigh incompatible elements in plagioclase,indicating anisland arc basalt-like nature. The younger basalts show low incompatible and high compatible elements, negative Rb, Pb, Nb, and Ta, positive Sr anomaly, positive εNd(t) values, lower (87Sr/86Sr)i, and low incompatible elements in the plagioclase, indicating an oceanic island basalt-like characteristic. The early ca. 126 Ma basalts were probably derived from a deeper and older enriched lithospheric mantleconsisting of rutile-bearing garnet pyroxenite or eclogite, whereas the younger ca. 91 Ma basalts were derived from a shallower and younger depletedasthenospheric mantle constituting peridotite, with limited amounts of enriched lithospheric mantlecomponent. The retreat and rollback of the paleo-Pacific slab and related lithospheric thinning and mantle composition transition processes probably occurred at ca. 126 Maand ca. 91 Ma in this inland region of the Yangtze Block in northwestern Jiangxi province.

Geochemistry and Zircon U–Pb Geochronology of the Wugongshan Granites in the Northwestern Jiangxi Area, China: Implications for the Paleozoic Tectonic Development of South China

The properties of the Caledonian orogeny along the transition belt of the Yangtze and Cathaysia blocks have received much attention in recent years. The widespread Early Paleozoic granites provide critical geological clues for unraveling the tectonic evolution and geodynamic processes of the South China Continent (SCC). Here we present new zircon U–Pb chronology, whole-rock major and trace elements, in situ Hf isotopes for Paleozoic granites, i.e., the Wugongshan granites in the northwest Jiangxi province, and aim to explore the magmatism and properties of the Caledonian orogeny involved in their formation. Our new data show that the Wugongshan granites were emplaced during the Early Silurian Period (442–438 Ma). The Paleozoic Wugongshan granites belong to S-type muscovite-bearing peraluminous granites (MPG) and show a single origin. The Wugongshan granites exhibit negative εHf(t) values (−11.56 to −6.19) and TDM2 model ages of 2148–1809 Ma, indicating their derivation from an ancient crustal source, through partial melting of ancient crustal material. The Wugongshan granitic magmatism is probably being generated in an extensional environment related to an intracontinental orogeny setting. It is inferred that the Paleozoic tectonic–magmatic event in the Wugongshan area was associated with the oceanic–continental convergence of the Paleo-Tethys Ocean. The Wugongshan granites highlight the intracontinental magmatism in the Early Paleozoic orogeny in the SCC.

In situ LA–ICP–MS analyses of muscovite: Constraints on granite-type Li mineralization in northwestern Jiangxi, South China

Giant granite-type lithium (Li) deposits in northern Jiangxi province (South China), such as the Shiziling–Baishuidong (1.1Mt @ 0.3 wt% Li2O) and Yichun #414 (0.6 Mt @ 0.39 wt% Li2O), are tectonically located in the Jiangnan Orogen. The concentration and enrichment mechanism of rare metals (incl. Li) in northern Jiangxi is still unclear. Mica is widely distributed in this Li-ore type and is closely ore-related. Therefore, we used mica geochemistry to determine the mineralization process and mechanism of the Shiziling-Baishuidong and Yichun #414 deposits. At Shiziling-Baishuidong, lithium mineralization is concentrated along the intrusive endo-contact of Early Cretaceous highly-fractionated S-type muscovite granite. Early albite and muscovite (with Li-rich mica) alterations, and late greisen (muscovite and quartz) alterations are common in the Shiziling-Baishuidong and Yichun #414 deposits. The hydrothermal and magmatic muscovite is mostly lepidolite and zinnwaldite, respectively. At Yichun, the biotite- or two-mica granite may have altered by F- and Na-rich magmatic–hydrothermal fluids, leaching the Li-Nb-Ta-W for the subsequent mineralization in the muscovitization and greisenization stages. The re-equilibrated muscovite (M2r), a metasomatic(altered) equilibrated muscovite in the altered granite, has the lowest Li (663 ppm), Nb (15.2 ppm), Ta (16.7 ppm), and W (6.12 ppm) contents. At both Shiziling–Baishuidong and Yichun, the magmatic muscovite has the highest Nb/Ta (mostly > 8) but lower Li/Rb (mostly 1.5), whereas the hydrothermal muscovite has the lowest Nb/Ta (mostly ∼ 4) but higher Li/Rb (mostly > 1.5). The re-equilibrated muscovite has Nb/Ta = 4 to 8 and a wide Li/Rb range (0.1 to 2.0). When lithium was precipitated, the re-equilibrated and hydrothermal muscovite mineralogy and chemistry show that hydrothermal alteration was essential in the granite-type Li ore formation at Shiziling–Baishuidong.

A multi-scale classification method for rocky desertification mapping in the red-bed area of northwestern, Jiangxi, China

Currently, the monitoring of rocky desertification(RD) is concentrated in the karst area, whereas the study in red-bed areas is rare. In this paper, we present a multi-scale classification framework for RD monitoring based on spectral-spatial features. At the pixel scale, we explored several spectral indices based on spectral statistics and separability analysis of land cover samples. The homogeneous land covers were classified by the decision rules from the selected spectral indices (such as NDIOI, NRRI and NDGI); At the patch scale, RD classes were further distinguished by spatial decision rules based on multiple neighborhood features including proximity, linear density, and buffer distance. The method was applied on an OLI image over the red-bed area of northwestern Jiangxi, south central China, and validated using ground-based observations. The experimental results of verification and comparison are satisfactory. This work demonstrates a methodological supplement to the monitoring of red bed RD.

Neoproterozoic tungsten mineralization: Geology, chronology, and genesis of the Huashandong W deposit in northwestern Jiangxi, South China

Neoproterozoic tungsten mineralization: Geology, chronology, and genesis of the Huashandong W deposit in northwestern Jiangxi, South China

Geographic Patterns of the Richness and Density of Wild Orchids in Nature Reserves of Jiangxi, China

Orchids have attracted much attention from researchers, because of their richness of species and their great ornamental and medicinal value. Jiangxi Province, which is located in southeastern China and ringed on three sides by mountains, contains many nature reserves and harbors large number of orchids. Here, we conducted field surveys of orchids in 35 nature reserves in Jiangxi, using sampling lines and plots. We also analyzed the relationship between orchid richness and density with environmental variables and studied the relationship among these nature reserves. We found that the mountainous areas of southwestern, southern, and northeastern Jiangxi have a high richness and density of orchids, while the mountainous areas of central and northwestern Jiangxi have low richness and density. Jiulianshan and Jinggangshan are the two most rich-species reserves, with 58 and 55 orchids, respectively. Eight reserves (22% of those surveyed) had fewer than 10 orchids. Compared with soil, climate, and vegetation, topography was more closely related to the richness and density of orchids. Topographical variables explained 19% and 20% of the total variation in SR and SD, respectively. The result of hierarchical clustering analysis showed that the 35 nature reserves of Jiangxi obviously fall into two main clusters, which are separated by the Ganjiang River–Poyang Lake water system. In conclusion, the geographical patterns of richness and the density of orchids in Jiangxi are uneven and are affected by topography and vegetation, while their distribution is affected by the terrain of Jiangxi. Our work explains the richness and density patterns and the assembly mechanism of the orchids in Jiangxi and also provides new ideas for the protection of orchids in this region.

Spatial‐Temporal Distribution, Geological Characteristics and Ore‐Formation Controlling Factors of Major Types of Rare Metal Mineral Deposits in China

AbstractRare metals including Lithium (Li), Beryllium (Be), Rubidium (Rb), Cesium (Cs), Zirconium (Zr), Hafnium (Hf), Niobium (Nb), Tantalum (Ta), Tungsten (W) and Tin (Sn) are important critical mineral resources. In China, rare metal mineral deposits are spatially distributed mainly in the Altay and Southern Great Xingán Range regions in the Central Asian orogenic belt; in the Middle Qilian, South Qinling and East Qinling mountains regions in the Qilian–Qinling–Dabie orogenic belt; in the Western Sichuan and Bailongshan–Dahongliutan regions in the Kunlun–Songpan–Garze orogenic belt, and in the Northeastern Jiangxi, Northwestern Jiangxi, and Southern Hunan regions in South China. Major ore‐forming epochs include Indosinian (mostly 200–240 Ma, in particular in western China) and the Yanshanian (mostly 120–160 Ma, in particular in South China). In addition, Bayan Obo, Inner Mongolia, northeastern China, with a complex formation history, hosts the largest REE and Nb deposits in China. There are six major rare metal mineral deposit types in China: Highly fractionated granite; Pegmatite; Alkaline granite; Carbonatite and alkaline rock; Volcanic; and Hydrothermal types. Two further types, namely the Leptynite type and Breccia pipe type, have recently been discovered in China, and are represented by the Yushishan Nb–Ta– (Zr–Hf–REE) and the Weilasituo Li–Rb–Sn–W–Zn–Pb deposits. Several most important controlling factors for rare metal mineral deposits are discussed, including geochemical behaviors and sources of the rare metals, highly evolved magmatic fractionation, and structural controls such as the metamorphic core complex setting, with a revised conceptual model for the latter.

Soil fertility characteristics and their influencing factors in tea plantations of Jiangxi Pro-vince, China

To investigate soil fertility status and characteristics of typical tea plantations, we selec-ted 372 typical tea plantations of 21 areas across Jiangxi Province and analyzed the soil nutrient, spatial data, and their correlations with topography, soil type, elevation and plantation age. The results showed that soil pH, organic matter, alkaline nitrogen, available phosphorus, available potassium, total nitrogen, total phosphorus and total potassium of tea plantation in Jiangxi reached 53.9%, 60.1%, 56.1%, 22.9%, 38.5%, 43.7%, 11.1% and 95.5% of indices of high fertility, high efficiency and high yield tea plantation, respectively, with the available phosphorus showing a strong variation. Soil available copper, zinc, iron, manganese and boron reached 76.3%, 74.2%, 96.8%, 73.1% and 0.0% of the first-class standards for soil trace elements, respectively. Tea plantations with highest soil fertility located in central Jiangxi, followed by northeastern and northwestern Jiangxi, and lowest in southern Jiangxi. Soil pH was significantly positively correlated with organic matter, alkaline nitrogen, available phosphorus, available potassium, total nitrogen and total phosphorus but not for total potassium. For different topography, soil fertility was highest in the flat land, followed by the high mountains, and lowest in the mountains and hills. Across different soil types, soil fertility was higher in paddy soil, sandy soil and mountain yellow brown soil, followed by yellow soil, red-yellow soil and purple soil, and lowest in red soil. Soil pH, organic matter and total potassium increased while available phosphorus decreased with altitude. The organic matter, alkaline nitrogen, available phosphorus, total nitrogen and total phosphorus increased, but soil pH decreased with time. In summary, soil fertility of tea plantations in Jiangxi Province was generally good, with high organic matter, total potassium, available copper, zinc, iron and manganese. However, soil was acidic, available phosphorus and total phosphorus content was low, available boron was seriously limited. We suggest increase soil pH and potassium supply in central Jiangxi, increase potassium and nitrogen fertilizer supply in northeastern Jiangxi, increase organic matter and phosphorus fertilizer supply in northwestern Jiangxi, and increase nitrogen, phosphorus and potassium supply combined with organic fertilizers in southern Jiangxi. High mountain tea plantations should enhance available phosphorus and potassium supply. Mountain tea plantations should enhance nitrogen and phosphate supply. Tea plantations with red and yellow soil should increase pH and total potassium supply. Tea plantations with red soil should apply nitrogen, phosphorus and potassium fertilizers combined with organic fertilizers. Tea plantations with yellow soil and mountain yellow brown soil required additional phosphorus supply, and tea plantations with purple soil should increase soil organic matter supply. Tea plantations need to increase dolomite powder, physiological alkaline fertilizers and organic fertilizers to prevent soil acidification.

Protection Status and Development Strategies of Traditional Villages in Northwestern Jiangxi Province

5 traditional villages in northwestern Jiangxi province are taken as the research objects in this paper, it carries on the field investigation and data arrangement on the content of the national traditional village evaluation and identification system, including the site selection and preservation of village pattern; the protection and utilization of traditional buildings; the non-material cultural heritage and its physical space environment. The results show that these traditional villages protection is faced with the problems of lack of integrity protection concept, improper construction management mode and conflict among relevant subjects. Finally, in view of the current situation, the protection and development strategies of traditional villages are put forward from three respects, Human-oriented thought, Development model and Industrial structure.

Biotite in highly evolved granites from the Shimensi W–Cu–Mo polymetallic ore deposit, China: Insights into magma source and evolution

Highly evolved granites are an important type of granitic rock given their close relationship with W–Sn–Nb–Ta and rare-metal mineralization and unusual geochemistry. Compared with typical granites, highly evolved granites experience a more complex magmatic evolution, which is difficult to investigate with whole-rock analyses. In this paper, we present a comprehensive major and trace element (including halogen) dataset for biotites from highly evolved granites in the Shimensi ore deposit, located in northwestern Jiangxi province, South China, which is one of the largest W deposits in the world, to constrain its magma source and evolution.Biotites in the Shimensi granites have a magmatic origin. They are characterized by low Mg# [ = 100 × MgO/(MgO + FeOT), in mol] (29–43, mean = 34), high A/CNK [ = Al2O3/(CaO + Na2O + K2O), in mol] values (1.60–2.91, mean = 1.78), similar to biotite compositions in S-type granites worldwide, suggesting the parental magmas were of meta-sedimentary origin. Biotite trace element data reveal a differentiation trend from fine-grained granite to granite porphyry and porphyritic granite, as indicated by gradually decreasing K/Rb and Nb/Ta ratios and Ba and Ti contents, and increasing Rb, Cs, W, Nb, and Ta contents. Tungsten contents in biotite increase by two orders of magnitude from ∼0.1 ppm in fine-grained granite to ∼30 ppm in porphyritic granite due to progressive fractional crystallization. The log (fH2O/fHF) and log (fHCl/fHF) values inferred from the biotites increase with progressive fractional crystallization, indicating no obvious fluid exsolution before or during biotite crystallization. High degrees of fractional crystallization and late fluid exsolution in the Shimensi granites were favorable for W mineralization. Nb/Ta ratios of the biotites decreased from 24.3 to 4.30 with progressive fractional crystallization. This result, along with the Rayleigh fractional crystallization modeling results for whole-rock Nb and Ta contents, suggest that fractional crystallization of biotite is the major control on decreasing Nb/Ta ratios in the Shimensi granites.

Li–Nb–Ta mineralization in the Jurassic Yifeng granite-aplite intrusion within the Neoproterozoic Jiuling batholith, south China: A fluid-rich and quenching ore-forming process

The Neoproterozoic Jiuling batholith in northwestern Jiangxi Province, south China, is one of the largest batholiths in the Nanling Range, and it is intruded by Mesozoic granitic intrusions associated with mineralization. The Jurassic Yifeng granitic pluton intrudes to the southern part of the Jiuling batholith and comprises Li-rich muscovite (Li-Mus) granite, trilithionite (Tri) granite, and aplite dikes. The granitic rocks are enriched in rare metals (Li–Rb–Cs–Nb–Ta). We conducted whole-rock geochemical analyses, undertook columbite U–Pb dating, and examined the textures and chemistry of feldspars, micas and the accessory minerals montebrasite, columbite-group minerals (CGMs), microlite, cassiterite, and zircon. All three granitic rock types have high Li contents (up to ~6200 ppm), and the δ7Li values of the Li-Mus granite and aplite are −3.55 ± 0.14‰ and −5.34 ± 0.04‰, respectively. The isolated grains of CGMs and cassiterite in the aplite are magmatic products, but intense fluid activity in the later stages and quenching resulted in unique mineral aggregates of cassiterite + CGMs + zircon. The Nb–Ta mineralization of the Li-Mus granite took place at 144 ± 5 Ma according to columbite U–Pb dating, and this age is similar to that of the neighbouring Yichun granitic pluton to the south. Moreover, both the Yifeng and Yichun plutons contain P-rich rare-metal-bearing Li–F granitic rocks that contain P-rich feldspars, montebrasites (amblygonites), Cs-rich lepidolites, CGMs close to the Mn endmember, and Hf-rich zircons. It is inferred that a metallogenic district characterized by Li–Nb–Ta mineralization exists in northwestern Jiangxi Province, thus providing a reliable guide for further exploration.

Difference Analysis of Organic Matter Enrichment Mechanisms in Upper Ordovician-Lower Silurian Shale from the Yangtze Region of Southern China and Its Geological Significance in Shale Gas Exploration

The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The organic matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of organic matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying sedimentary organic matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of sedimentary organic matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich sedimentary organic matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.

Petrogenesis of ore-forming granites with implications for W-mineralization in the super-large Shimensi tungsten-dominated polymetallic deposit in northern Jiangxi Province, South China

The Shimensi deposit is a newly discovered, super-large tungsten (W) polymetallic deposit in northwestern Jiangxi Province, South China. In this paper, we reported new zircon U–Pb ages for the ore-bearing porphyritic biotite granite (151.3 ± 2.8 Ma) and fine-grained granite (150.1 ± 1.2 Ma and 150.7 ± 2.4 Ma), which represent the oldest Mesozoic granitic magmatism reported at Shimensi. Our ore-bearing granite porphyry ages (142.7 ± 2.3 Ma and 143.3 ± 1.5 Ma) have better constrained the timing of the Jurassic-Early Cretaceous ore-forming magmatism. Geochemically, the Shimensi granitoids are strongly peraluminous, with high contents of SiO2 (70.7–78.7 wt%) and K2O (>4.0 wt%), P2O5, Rb, Ta and U, and low contents of Ti, Sr, Ba and HREEs. The rocks also show positive P2O5 vs. SiO2 correlation, suggesting a highly-fractionated S-type affinity. Different from most W-bearing granites in the Jiangxi region, the calculated zircon εHf(t) (−10.0 to −2.4; two-stage model ages: 1350–1824 Ma) and δ18Ozircon values (+6.40 to +8.87‰) of the Shimensi granites suggest that the latter were mainly derived from the partial melting of heterogeneous source rocks, probably with combined contributions from the Neoproterozoic Shuangqiaoshan Group metamorphic rocks and Jiuling granodiorite. The calculated zircon Eu/Eu∗ (0.05–0.58; mean = 0.20) and Ce4+/Ce3+ (3.83–96.49; mean = 20.99) ratios of the granites indicate very low oxygen fugacity (fO2) for the ore-forming magmas, a highly favorable factor for W mineralization. Potentially W and Cu-rich source rocks, and highly-fractionated and reducing granitic magmas, were important factors that triggered super-large W mineralization at Shimensi.

Multiple dating and tectonic setting of the Early Cretaceous Xianglushan W deposit, Jiangxi Province, South China

The Xianglushan W deposit in northwestern Jiangxi Province, South China, is one of numerous large-size W deposits along the northern margin of the Jiangnan Massif. The deposit comprises lenticular and stratiform-like orebodies, mainly along the contact between argillaceous limestone of the Cambrian Yangliugang Formation and a biotite granite pluton. The mineralization is zoned from proximal W greisen within the cupolas of the biotite granite, through W skarn and sulfide-scheelite bands near the pluton, to distal quartz-sulfide ± scheelite veins. The granitic pluton and an aplitic dyke in the mining area contain zircon grains with U–Pb ages of 123.8 ± 0.8 Ma and 117.3 ± 1.7 Ma, respectively. Six molybdenite samples collected from skarn ores yielded a Re–Os weighted mean age of 125.5 ± 0.7 Ma, and muscovite separates from greisen ores yielded a 40Ar/39Ar plateau age of 122.8 ± 0.78 Ma. The molybdenite Re–Os and muscovite Ar–Ar ages are consistent with the zircon U–Pb age of the hosting granite. The Xianglushan deposit is formed by an Early Cretaceous W–dominated polymetallic ore-forming event in the Jiangnan porphyry–skarn W belt. Zircon from biotite granites in the Xianglushan deposit has negative εHf(t) values, generally from − 5.7 to − 3.1, with corresponding two-stage Hf model ages of 1363–1218 Ma, reflecting derivation of magmas from a crustal source. Molybdenite has Re contents from 12.12 to 22.77 ppm, indicative of a mixed crustal-mantle source, but with a dominantly crustal component. A compilation of precise ages for magmatism and mineralization in the Jiangnan porphyry–skarn W belt shows that there are two stages of mineralization at 150–135 Ma and 130–120 Ma, respectively. Integrated with published data, our results suggest that the Xianglushan W deposit formed in an extensional tectonic setting during the Early Cretaceous.

Early Cretaceous tungsten mineralization in Southeastern China: the Wuning example

ABSTRACTThe Wuning tungsten deposits in northwestern Jiangxi are located in the Middle-Lower Yangtze River metallogenic belt of SE China. This article decodes the large tungsten-mineralized ore field by analysing three typical deposits: Shimensi, Dahutang, and Shiwendong. The Shimensi deposit shows three mineralization styles, and the associated hydrothermal alteration mainly includes K-feldspathization, greisenization, chloritization, silicification, and carbonatization. The sulphur isotopic compositions of sulphides in the Dahutang deposit indicate that the sulphur source was homogeneous and closely related to magmatic sulphur. The lead isotopic compositions of sulphides suggest multiple sources that were also closely related to magmatism. The carbon isotopic compositions of calcite indicate that hydrothermal fluids were derived from the granitic magma. Hydrogen and oxygen isotopic compositions of quartz veins indicate that the ore-forming fluids had a magmatic-hydrothermal origin, but mixed with meteoric water. Fluid inclusions from the Shiweidong deposit are low density, indicating medium-high T and low-medium salinity, further suggesting that it was a shallow magmatic-hydrothermal deposit, and the metallogenic hydrotherm mingled with the surface water late in the evolution of the system. Mineralization was related to Early Cretaceous magmatism in eastern China. The subduction of the palaeo-Pacific plate and the subsequent lithospheric delamination reflected transition from a compressional to extensional tectonic regime. The upwelling of the hot asthenosphere triggered partial melting of the Neoproterozoic Shuangqiaoshan Group, with high W background concentrations. The ascent of the magma resulted in the exsolution of the ore-bearing magmatic hydrothermal fluid.

Geology and molybdenite Re–Os age of the Dahutang granite-related veinlets-disseminated tungsten ore field in the Jiangxin Province, China

This is a brief research report about the recently-discovered and currently being explored Dahutang tungsten deposit (or ore field) in northwestern Jiangxi, south-central China. The deposit is located south of the Middle–Lower Yangtze River valley Cu–Au–Mo–Fe porphyry–skarn belt (YRB). The mineralization is genetically associated with Cretaceous porphyritic biotite granite and fine-grained biotite granite and is mainly hosted within a Neoproterozoic biotite granodiorite batholith. The Dahutang ore field comprises veinlets-disseminated (~95% of the total reserve), breccia (~4%) and wolframite–scheelite quartz vein (~1%) ore styles. The mineralization and alteration are close to the pegmatite shell between the Cretaceous porphyritic biotite granite and Neoproterozoic biotite granodiorite and the three styles of ore bodies mentioned above are related to zoned hydrothermal alteration that includes greisenization, K-feldspar alteration, silicification, carbonatization, chloritization and fluoritization arranged in time (early to late) and space (bottom to top).Five samples of molybdenite from the three types of ores have been collected for Re/Os dating. The results show Re/Os model ages ranging from 138.4Ma to 143.8Ma, with an isochron age of 139.18±0.97Ma (MSWD=2.9). The quite low Re content in molybdenite falls between 0.5ppm and 7.8ppm that is indicative of the upper crustal source. This is quite different from molybdenites in the YRB Cu–Au–Mo–Fe porphyry–skarn deposits that contain between 53ppm and 1169ppm Re, indicating a mantle source.The Dahutang tungsten system is sub-parallel with the YRB porphyry–skarn Cu–Au–Mo–Fe system. Both are situated in the north margin of the Yangtze Craton and have a close spatial–temporal relationship. This possibly indicates a comparable tectonic setting but different metal sources. Both systems are related to subduction of the Paleo-Pacific plate beneath the Eurasian continent in Early Cretaceous. The Cu–Au–Mo–Fe porphyry–skarn ores are believed genetically related to granitoids derived from the subducting slab, whereas the porphyry W deposits are associated with S-type granitoids produced by remelting of the upper crust by heat from upwelling asthenoshere.

Zircon SHRIMP U-Pb geochronology of the Neoproterozoic Chengjiang Formation in central Yunnan Province (SW China) and its geological significance

The Chengjiang Formation is the earliest continental clastic deposit after the Jinning Orogeny in central Yunnan Province, and therefore its accurate depositional age is significant for understanding the formation and evolution of the Neoproterozoic rift basins in southern China. However, hampered by accuracy of the dating technique, the existing age data for the Chengjiang Formation are not very reliable. A large number of magmatic zircons were obtained from the tuff interbed in the lower part of the Chengjiang Formation in Jinyang area and the bottom part of the Chengjiang Formation in Dongchuan area, central Yunnan Province, and high-precision SHRIMP U-Pb dating was carried out on these zircons. The results show that the weighted mean 206Pb/238U ages are 797.8±8.2 and 803.1±8.7 Ma respectively. In combination with related geological evidence, it has been demonstrated that the bottom boundary age of the Chengjiang Formation should be 800±5 Ma, whereas the top boundary age could be ca 725 Ma. By synthetically analyzing the latest age data for the relevant strata, it has been confirmed that the Chengjiang Formation should be correlated with the Suxiong Formation and the Kaijianqiao Formation in western Sichuan Province, the Liantuo Formation in the middle and lower Yangtze, the Hongchicun Formation and the Shangshu Formation in northern Zhejiang Province, the Puling Formation in southern Anhui Province, the Luokedong Formation and the Majianqiao Formation in northwestern Jiangxi Province, the Wuqiangxi Formation in northwestern Hunan Province, the Fanzhao Formation and the Qingshuijiang Formation in southeastern Guizhou Province, and the Sanmenjie Formation and the Gongdong Formation in northern Guangxi Province. Sedimentary cycle analysis shows that the sedimentary filling sequence of the Neoproterozoic rift basins in southern China can be divided into four cycles. Among them, Cycle II began at ca. 800 Ma, accompanied by intensive tectonic-thermal events. The zircon U-Pb ages from the bottom of the Chengjiang Formation reported in this paper indicate that the Neoproterozoic Kangdian rift subbasin probably started to develop at ca. 800 Ma and therefore missed Cycle I of the Neoproterozoic sedimentary filling sequence in southern China.

Regional geochemical secondary negative anomalies and their significance

Research involving secondary negative anomalies and their application in regional stream sediment surveys has been scarce. Conventionally, negative anomalous threshold values have been calculated in the same way as positive anomalous threshold values. But the conventional methods all have drawbacks which hinder their application. In this paper, we have chosen to delineate negative (and/or positive) anomalies using contrast values in order to overcome the drawbacks. Regional stream sediment surveys at a scale of 1 : 200 000 have been carried out in western Jungger, Shanxi, Kunlun, northwestern Jiangxi, and other areas in China. The geochemical data were processed using System RESMA. On the basis of the distribution of negative and positive single-element anomalies, three possible arrangements may occur: (1) negative anomalies accompanied by positive anomalies; (2) only positive anomalies occurring with no negative anomaly nearby; (3) only negative anomalies, with no positive anomaly nearby. These situations reflect different geological settings and different mineral forming processes. Basically, two different distribution patterns of regional negative anomalies in relation to the backgrounds — low background (LB) and high background (HB) —may be observed in different geological environments: (1) regional negative anomalies are distributed only around the positive anomalies in the LB area; (2) regional negative anomalies can exist on the periphery of positive anomalies in both LB and HB areas. Two kinds of patterns for regional multi-element negative and positive anomalies reflecting different geological processes have been noted: (1) coincident positive anomalies for one group of elements and negative anomalies for another group of associated elements can be used to uniquely define ore deposition; (2) regional positive multi-element anomalies of some elements (including ore and associated elements) occurring over a deposit are accompanied by negative anomalies on the periphery of the deposits. Two regional models of negative and positive anomalies are established for Au and Cu deposits. Integration of multi-element positive and negative composited geochemical anomalies are much more useful than positive anomalies or positive composited anomalies to delineate regional structures.

The geochemical evolution of the proterozoic continental crust in northwestern Jiangxi and western Zhejiang, China

The petrochemistry and Sm-Nd isotopic compositions and- the geochemical characteristics of REE, U,Th, etc. in the Late Proterozoic and Early Palaeozoic strata in northwestern Jiangxi and western Zhejiang provinces are described in this paper. It seems to be sure that the middle Proterozoic strata of southeastern China are low in the degree of maturation. The strata contain much mantle-derived material. At the end of Late Proterozoic there was an abrupt turn with respect to the crustal geochemical evolution of the eastern part of South China. Since then, the geochemical environment has undergone a change from a simple reducing environment to a complex oxidizing-reducing environment, which would be geochemically beneficial to the formation of Late Sinian to Early Cambrian U-bearing formations.

Un dialecte du nord Jiangxi : Wuning

The dialect of Wuning city is spoken in the Xiu river valley in northwestern Jiangxi. In it, the voiced obstruent initials of Middle Chinese have undergone an unusual type of devoicing: aspirated in a subset of tone B, unaspirated elsewhere, with a difference in tonal treatment between the aspirated and unaspirated sets of reflexes in tone B. The division 3 palatal medials are preserved after Middle Chinese palatal sibilants and retroflex stops ; the old vowel contrasts between rimes ^'^ and Щ , .$ . and /^ , **& and ^- are in part preserved ; the lexicon is also conservative.