Abstract:The Dagangou granites in the Jinshuikou area of the East Kunlun orogen are mainly composed of medium-coarse grained syenogranites. Their SiO₂ and Al₂O₃ values vary from 68.68% to 71.12% and 14.01% to 15.40%, with a mean value of 69.84% and 14.82%, respectively. The K₂O/Na₂O ratios are high (1.19~1.64, with a mean value of 1.40). The A/CNK values[molar ratio of Al₂O₃/(CaO+Na₂O+K₂O)] are 0.98~1.02, with a mean value of 1.00, indicating the quasi aluminum-weakly peraluminous geochemical characteristics. All the Dagangou granites have high total REE abundances. Moreover, their chondrite-normalized REE patterns all show enrichment of LREE and obviously negative Eu anomalies. On the primitive mantle-normalized trace element diagrams, the samples have similar distribution patterns with enrichment of U, Th, and depletion of HFSEs (Ti, P, Nb, Ta) and Ba, Sr, indicating the geochemical characteristics of A-type granite. The εNd(t) values of -5.6~-7.3 and t_DM values from 1.54 Ga to 2.27 Ga suggest that the source might have mainly been derived Proterozoic materials (Jinshuikou Group). Zircon εHf(t)=2.2~2.6, significantly different from the earth's crust magmatic Hf isotopic compositions, showing that rocks were contaminated by the mantle. The LA-ICP-MS zircon U-Pb indicates that the granites were emplaced at 392±2 Ma (MSWD=1.14). The geochemical characteristics combined with the tectonic evolution of East Kunlun show a pronounced affinity of post-orogenic granites, belonging to the response to the mantle magma upwelling and melting of the crust.

Abstract:The Cuonadong leucogranite is one of the most important parts of North Himalayan leucogranite belt. Geochemical data show that Cuonadong leucogranite is the calcium alkaline and strong peraluminous granite with high silica (SiO₂ is 74.20%~74.52%), poor iron (Fe₂O₃ is 0.04%~0.20%, FeO 0.04%~0.58%), poor magnesium (MgO is 0.06%~0.14%), and calcium alkaline (σ is 2.15~2.32) as well as strong peraluminous nature (A/CNK is 1.11~1.15). Its total rare earth is relatively low (∑REE is 47.24×10^-6~57.59×10^-6), with enrichment of LREE (LREE is 39.85×10^-6~49.23×10^-6), depletion of HREE (HREE is 6.91×10^-6~8.68×10^-6) and obvious negative Eu anomaly (0.49~0.80). It is characterized by an enrichment of some large ion lithophile elements (Rb, Th, U, K) and loss of high field strength elements (Nb, Ta, Zr Ti). Zircon U-Pb dating results show that the Cuonadong leucogranite's formation time is Miocene (21 Ma), which belongs to the peak of the late stage of north Himalayan leucogranite (24~12 Ma). Zircon εHf(t) values are negative with a wide variation (-3.92~-17.64), which shows that its magma source was the crust, mostly from the metapelite, with the probable mixing of many kinds of materials in its source. The petrogenesis of Cuonadong leucogranite is that the high Himalayan crystalline rock series experienced decompression melting during the rapid pull-back of the plate in the post-collision tectonic setting, with the initial magma crystallization temperature being 675~702℃.

Abstract:The Buerkesitai granite where the Adayi gold ore deposit occurs is composed of host rocks, diorite microgranular enclaves and intermediate dyke swarms. The relative composition of geochemistry is one of the most effective means for determining the mixture of magma, whereas the concentrations of gold and copper geochemical prospecting samples from different areas of the host rock can identify the relationship between gold and copper ore potential and the mixture of magma. The patterns of REE and trace elements are similar to those of the host rock, diorite microgranular enclaves and intermediate dyke swarms. Harker diagrams, ratio diagrams in the same denominator, correlation diagrams and ratio diagrams of trace elements in the same denominator of the host rock, diorite microgranular enclaves and intermediate dyke swarms all have the same linear trends, which means that significant element migration and transfer of component once occurred. The host rock has high gold and copper concentrations and their regularities of distribution are similar. The fact that the gold and copper anomalies are scattered around areas where abundant diorite microgranular enclaves exist indicates that the mantle-sourced basic end-member represented by diorite microgranular enclaves might have provided the material source for gold and copper mineralization. The association between gold and copper mineralization potential and magma mixture indicates that one of the most important reasons for the enrichment of gold and copper in Darbut tectonic-magmatic belt is the contribution of the mantle-sourced basic end-member to metallogenesis.

Abstract:A suite of amphibolites associated with marble from Chencai Group is exposed at Xiahetu Village in Zhuji County of Zhejiang Province. Detailed geological and geochemical studies were carried out on the Xiahetu amphibolites. The SiO₂ content of the amphibolites ranges from 43.22% to 46.56%, MgO content ranges from 3.23% to 7.87% and TiO₂ content ranges from 1.90% to 2.98%. All these geochemical features are similar to the average value of oceanic island basalt (OIB). Moreover, the major elements characteristics of the amphibolite suggest that it belongs to the alkali basalt series. The total REE values of the amphibolite range from 114.47×10^-6 to 192.39×10^-6, and (La/Yb)_N ratios range from 5.93 to 12.13. The chondrite-normalized REE patterns show right-inclined shape, which suggests the enrichment of LREE. The primitive mantle normalized trace element spider diagram shows obvious uplift, which is also similar to the feature of oceanic island basalt. Some tectonic discrimination diagrams suggest that Xiahetu amphibolites were formed in an oceanic island tectonic environment. Petrogenetic research shows that the protolith of the amphibolite had experienced a little crust contamination during the magmatic events. So the geochemical features of the amphibolite can be used to infer its original mantle features. It is held that the protolith of the Xiahetu amphibolits possibly formed in a marine volcanic geological setting near the subduction zone and sourced from the seamount fragments accretion during the subduction of the oceanic crust. Thus rocks in Chencai Group are probably a suite of subduction-accretionary complexes. U-Pb dating results of zircons in the amphibolite yield a mean age of 420.6±1.8 Ma which represents the metamorphic time of its protolith. In conjunction with other field evidence, the authors consider that the amalgamation between the Yangtze and Cathaysia Blocks was completed in Caledonian.

Abstract:The Xiangtan manganese ore deposit is mainly hosted in Mn-bearing black shale on the bottom of the Datangpo Formation in Neoproterozoic Nanhua system (Cryogenian), with rhodochrosite as the main ore-bearing mineral. The Xiangtan manganese ore deposit is characterized by the low Fe/Mn ratios. The ratios of redox sensitive trace elements such as Th/U, V/(V+Ni) and V/Cr indicate a sub-oxidation to exidation depositional environment, which implying that rhodochrosite was not formed by the direct precipitation of Mn²⁺ and CO₃^2-. The manganese ores are characterized by high total ΣREE content, relative middle REE enrichment compared with the light, heavy REE, and obvious positive Ce anomalies, implying that the element manganese precipitated firstly as Mn oxides or hydroxide. Meanwhile, the carbon isotopes of rhodochrosite ores display depletion of heavier C isotopes, suggesting that the organic carbon was involved in the formation of rhodochrosite. It is thus held that the metallogenic mechanism of the Xiangtan manganese ore deposit includes two processes (precipita_tion and transformation). Mn was buried under the hypoxia _condition after precipitation as Mn oxides or hydroxides from the upper oxide water, and then was reduced and transformed to Mn carbonates through the degradation of organic matter in the anoxic diagenetic environment. This ore-forming mechanism is consistent with that of several other typical Datangpo-type manganese ore deposits.

Abstract:Located in the middle Jiangnan orogenic belt, the Dahutang ore concentration area in northern Jiangxi Province is famous for producing world-class superlarge tungsten ore deposits and large copper ore deposits, thus serving as one of the largest discovered tungsten producing base area in recent years. This study is aimed at investigating the W, Cu and Mo mineralization features and ore-forming age in different rock units of Yanshanian period in the Shimensi ore district. Scheelite mainly occurs in porphyritic granite and the external contact zone of the wall rock with veinlet-disseminated granite. Chalcopyrite and molybdenite are mainly existent in porphyritic granite, fine-grained granite, granite porphyry and the contact zone of wall rock with disseminated granite. Ore chemical composition indicates that the components of sulfides are relatively uniform in three sets of rock units with the following data:chalcopyrite (Cu 34.215%~35.161%, Fe 29.206%~30.721%, S 34.388%~35.520%) and molybdenite (Mo 59.44%~60.54%, S 40.067%~40.370%). The molybdenite Re-Os isotopic model average ages are 143.3 Ma, 145.2 Ma, 144.5 Ma, 143.6 Ma respectively in porphyritic biotite granite, fine-grained biotite granite, biotite granite porphyry and thick-vein quartz, which are basically identical within the error range, indicating that Cu, Mo mineralization were formed in one metallogenic epoch. Therefore the molybdenite Re-Os isotopic isochron age of 145.1±1.0 Ma (MSWD=0.46) could represent the mineralization time of Cu, Mo. Combined with the previous study of granites in Dahutang, the authors hold that the mineralization of scheelite and Cu, Mo took place in two metallogenic epochs in the Shimensi ore district. The former was closely related to the porphyritic granite and the latter probably had metallogenic relationship with the granite porphyry of late Yanshanian period. The ore-forming materials were delivered from granite porphyry to other rock units to cause mineralization gradually.

Abstract:The Kuhai Group is the oldest metamorphosed basement in southern East Kunlun Terrane (SEKT) which is exposed around Kuhai-Wenquan area. This study presents in situ zircon U-Pb analyses (LA-ICP-MS) of 67 zircons from two paragneisses in the Kuhai Group in SEKT. The results suggest that the Kuhai Group was deposited in Early Neoproterozoic and underwent a metamorphic event in Silurian (423 Ma). Compared with the zircon U-Pb dating of the Jinshuikou Group in northern East Kunlun Terrane (NEKT), the ages of their source materials all have the records of 1550~1650 Ma, 1900~2100 Ma and 2350~2?550 Ma, suggesting that they might have had similar sources; peak ages of the youngest member in the age spectrum with magmatic origin are 750~800 Ma and 900~1250 Ma respectively, suggesting that their earliest sedimentary ages are Early Neoproterozoic and Late Mesoproterozoic-Early Neoproterozoic respectively; peak ages of the youngest member in the age spectrum with metamorphism origin are 400~450 Ma, indicating that they all underwent the amphibolite facie metamorphism in Silurian. It can therefore be inferred that the oldest metamorphosed basements in SEKT and NEKT had the similar evolution histories during pre-Silurian, and even if the paleo-ocean basin between the SEKT and the NEKT existed in early Paleozoic, the ocean basin must have been a small one.

Abstract:The research on the partial melting systematics of subducting carbonated sediments is a necessary part of the study of deep carbon cycle and is also important for investigating the mass cycle, the genesis of magma and the mantle heterogeneity. The partial melting of carbonated pelites under the condition of 6.0 GPa and 800~1600℃ was investigated using the multi-anvil apparatus. The experimental products include garnet, clinopyroxene, coesite, kyanite, carbonates, phengite and melts. The carbonate minerals are calcite and magnesite, which exist at the subsolidus experiments of 6.0 GPa. The experimental bulk composition of this study has the lowest melting temperature for all carbonated lithologies at 6.0 GPa. The partial melts are silicate melts, and their proportions increase with increasing temperature; in addition, their compositions change with increasing temperature.

Abstract:Located in southwestern Guizhou Province, the Nibao gold deposit discovered recently is an important Carlin-type gold deposit. Pyrite is the major gold-bearing mineral in the deposit. Petrographic observations and electron microprobe analysis (EPMA) of sulfides from the Nibao gold deposit show that arsenic pyrites is the major gold-bearing mineral. A combined detailed field work, ore petrographic investigation and EPMA studies revealed three kinds of arsenic pyrites, i.e., zoned arsenic pyrite (PyⅠ), colloidal arsenic pyrite (PyⅡ), and bioclastic arsenic pyrite (PyⅢ). The EPMA and LA-ICP-MS analyses indicate that PyⅠ is mainly composed of pyrite core and arsenic pyrite zones, formed in different metallogenic stages. Pyrite core is characterized by high S, Fe concentrations and low Au, As, Ag and Cu, indicating a sedimentary-diagenetic origin or precipitation in the early metallogenic stage. Zoned arsenic pyrite, growing along pyrite core, is characterized by high Au, As, Ag, and Cu concentrations, indicating a main mineralization hydrothermal origin. The colloidal and bioclastic arsenic pyrites with homogeneous texture are similar to the rims of zoned pyrite with characteristics of high Au, As, Ag, Cu and low S, Fe, indicating that PyⅡ and PyⅢ were probably formed synchronously with the arsenic pyrite zones of PyⅠ. Arsenopyrite mainly occurs as overgrowths on arsenic pyrite and has rich As and poor Au, Ag, and Cu concentrations, suggesting that arsenopyrite was probably formed in the post-mineralization stage. The precipitation order of gold-bearing sulfides is as follows:As-poor sedimentary pyrites or early metallogenic stage pyrites→arsenic pyrites→arsenopyrite. Textures, paragenesis and trace element geochemistry of pyrite indicate that As-poor pyrite core mainly deposited during sedimentation, while most of economic metals (Au, Ag, As, and Cu) were introduced through the Late Yanshanian subsequent hydrothermal superimposition. The compositions of the gold-bearing pyrites support a magmatic hydrothermal model for the origin of gold-sulfide mineralization.

Abstract:The Taohe mafic rock is located in Langao County of Daba Mountain. The types of Taohe mafic rock are consistent with those of regional mafic rocks, mainly consisting of diabase, gabbro, gabbro diabase and kaersutite-rich diorite, with the adjacent mafic rocks showing a gradual transition state, indicating the same period of magmatism. The amphibole inside the diorite is kaersutite, characterized by long stripe and needle megacrystal, particle size of 1~3 cm, obvious euhedral crystal, and significant high aluminum (Al=1.93~2.06) and high titanium (TiO₂=4.54%~5.50%). The temperature is 1062~1129℃, the formation depth is 19.11~22.64 km, and the oxygen fugacity ranges from NNO=-0.36 to NNO=-0.01. The magma was derived from deeper source and intruded rapidly. The presence of kaersutite shows an apparent mantle metasomatism before the partial melting, and mantle metasomatism and formation of mafic rock had a necessarily close connection with subduction. Obvious deep source characteristics and subduction-related and crustal contamination characteristics indicate that the Taohe mafic rocks were formed in an extensional environment related to subduction.

Abstract:Located in the west of the Beishan metallogenic belt in Xinjiang, the Xiaochangshan iron deposit is hosted in gabbro and the contact zone of the gabbro and marble. Parts of the orebodies are hosted in the contact zone of the granodiorite and the marble. Previous researchers hold that the age of gabbro in the mining area is (276±1.2) Ma, similar to the age of gabbro in the Pobei copper-nickel-sulfide orebodies, so they both belong to Early Permian. The magma injection is an obvious phenomenon in the Xiaochangshan iron deposit. The orebodies occur as lenses, lumps, veins and thin layers. Metal minerals are mainly magnetite, with very little limonite and pyrite. The country rock alteration in the Xiaochangshan iron deposit is weak, comprising mainly garnetization, epidotization and marbleization. The electron microprobe analyses of magnetite show that the content of FeO_T in different iron ores has a large distribution range, and the content of Al₂O₃ is relatively higher. The ternary plot of TiO₂-Al₂O₃-(MgO+MnO) and TiO₂-Al₂O₃-MgO suggest that the formation of the Xiaochangshan iron deposit was associated with hydrothermal metasomatism of magmatic-hydrothermal fluid. The electron microprobe analyses of garnet show that the garnets from the Xiaochangshan iron deposit belong to andradite-grossular solid solution series, somewhat different fromthings of the typical skarn deposits. Combining the geological characteristics of the Xiaochangshan iron deposit with the study of the electron microprobe analyses, the authors believe that the Xiaochangshan iron deposit belongs to the polygenetic and compound deposit with magnetic and hydrothermal genesis, with the latter factor probably playing the major role.

Abstract:Limonite is an important ore of the gossan-type gold deposit and the iron deposit; nevertheless, the microstructure of limonite has not been investigated in detail. For the purpose of probing into morphological characteristics and microstructures of limonite ore, the authors investigated 70 samples from the Xinqiao sulfide iron deposit using X-Ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM). The limonite ore can be divided into two groups based upon the components and microstructures. Limonite (Ⅰ) with honeycomb structure was mainly sourced from the weathering of pyrite ore. The major minerals identified are represented by goethite with a minor amount of hematite and quartz. The particle sizes of goethite is in the range of 500 nm~2 μm with a higher ratio of length/diameter. Limonite (Ⅱ) with kidney structure was derived from the weathering of siderite ore. Goethite is also the major mineral, and the secondary minerals include manganite, hematite and illite. The length of goethite is less than 500 nm, with a lower ratio of length/width. The information on the mineralogy and microstructure of limonite not only can be used to infer the type of the primary minera but also is of important indicating signicance in search for gold deposits in gossans.

Abstract:Field sampling, chemical analysis, electron microprobe analysis (EPMA) and X-ray diffraction (XRD) analysis were conducted to study the chemical composition, material composition, trace elements and rare earth elements characteristics of black shale in Zhijin, Guizhou Province. The chemical composition of the ore sample was given priority to SiO₂ and Al₂O₃, which also had the characteristics of high K and low Na. The results of electron microprobe and X-ray diffraction analysis show that quartz, clay mineral, dolomite and pyrite are the main mineral composition. Pb, Ni, U, V, Cr and other metallic elements exist in the black shale of Zhijin with different degrees of enrichment. The amount of rare earth elements in black shale is 153.2×10^-6~224.89×10^-6, suggesting a LREE enrichment type. The authors also systematically discussed some problems such as resource utilization of black shale from polymetallic layers, shale gas, extraction of potassium from potassium-rich shale, and the phosphorus uranium resources near the bottom of the black shale. Black shale polymetallic layers contain Mo, V, Ni, Ag, U and other metal elements with utilization value. The content of organic carbon in the black shale is more than 2%, reaching geological conditions for shale gas development. Potassium can be extracted from illite in black shale for the preparation of potassium fertilizer. Phosphorus uranium deposit, mainly colloidal phosphorus uranium, is produced on the bottom of black shale and the contact zone phosphate layer, and hence the contact zone can serve as the uranium prospecting marker bed.

Abstract:The study of armoring effect is helpful to understanding the mechanism of acid mine drainage (AMD) releasing from limestone-rich metal sulfide tailings (limestone tailings). By performing static experiments of AMD immersing limestone particle materials, the authors studied the formation of secondary armor under acid water saturation condition, similar to the circumstances in acidified tailings. The results show that Fe content in AMD may be one of the main factors affecting the armoring effect of limestone. In high Fe concentration AMD (1029~1033 mg/L), the order of secondary precipitants is Al-rich phase→gypsum→lepidocrocite (adsorbing Zn, Cu and As) on the surface of limestone particles, and the precipitants make the limestone armored/passivated, causing the solution to maintain acidity. By contrast, in low Fe concentration AMD (6.71~74.8 mg/L), the secondary armor may not form, therefore limestone can be dissolved and release a large amount of CO₃^2-, which fully neutralizes H⁺ in solution, so that the solution can reach neutral circumstances. Based on this study, the authors hold that the limestone tailings with high Fe sulfide content (e.g. Fe 10.62%, S 5.70%) could have a higher risk of releasing AMD (and heavy metals), because the tailings could produce the acid water with high Fe content through oxidation and the armoring effect of limestone could occur easily.