Sulphide Deposits In China Research Articles

Deep Learning for 3-D Magnetic Inversion

The difficulty of 3D magnetic inversion is to use 2D magnetic anomaly data to obtain 3D magnetic susceptibility structure. The contribution of the underground medium to the magnetic anomaly decreases rapidly with the increase of the depth, which leads to the rapid attenuation of the inversion resolution with the depth. In this paper, artificial intelligence (AI) technology is applied to 3D magnetic inversion to predict the susceptibility model corresponding to magnetic anomaly. The inversion network built in this paper uses the method of down-sampling in the encoder to increase the receptive field and realize the feature extraction of magnetic anomaly data. In the decoder, attention fusion modules are added to fuse feature maps from different sources. Finally, we added a 3D refiner behind the decoder. The 3D refiner converts the 2D feature map from the decoder into 3D data. Based on the typical complex medium theory, this paper constructs a diverse sample set of complex 3D susceptibility models. The inversion experiment of synthetic data verifies the feasibility and versatility of the proposed network. Compared with the other methods, the distribution of susceptibility prediction obtained by our method is more accurate and more reliable in determining the magnetic body boundary. In the field example of Jinchuan Copper-nickel sulfide deposit in China, the network constructed in this paper can achieve high-precision 3D underground susceptibility imaging in this area. The susceptibility distribution is in good agreement with the borehole data and the proved deposit distribution.

Lithium isotope traces magmatic fluid in a seafloor hydrothermal system

Lithium isotopic compositions of fluid inclusions and hosted gangue quartz from a giant volcanogenic massive sulfide deposit in China provide robust evidence for inputting of magmatic fluids into a Triassic submarine hydrothermal system. The δ7Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions). These data confirm the temperature-dependent Li isotopic fractionation between hydrothermal quartz and fluid (i.e., Δδ7Liquartz-fluid = –8.9382 × (1000/T) + 22.22(R2 = 0.98; 175 °C–340 °C)), which suggests that the fluid inclusions are in equilibrium with their hosted quartz, thus allowing to determine the composition of the fluids by using δ7Liquartz data. Accordingly, we estimate that the ore-forming fluids have a δ7Li range from −0.7‰ to +18.4‰ at temperatures of 175–340 °C. This δ7Li range, together with Li–O modeling , suggest that magmatic fluid played a significant role in the ore formation. This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.

Classification of Magmatic Sulphide Deposits in China and Mineralization of Small Intrusions

Abstract Many important metal resources, such as Ni (Cu, Co), PGE, exist in magmatic sulfide deposits, are a hot spot in geological research. We divide the magmatic sulphide deposits in China into four types according to their tectonic setting, intruding mode, ore deposit mode, main metallogenic elements. The four types are as follows: (1) Small-intrusion deposits in paleo-continent; (2) Small-intrusion deposits in continental flood basalt; (3) Small-intrusion deposits in orogenic belt; and (4) The deposits associated with ophiolites. On the basis of the classification, we put forward that the main magmatic metallogenic type in China is small-intrusion metallogeny, and describe its characteristics from small intrusions related concept, three geologic settings, three volcanic-intrusive assemblages and metallogenic key factors. According to the experiences of prospecting at home and abroad, we point out that there is big potential in prospecting small-intrusion deposits, which need further study. At last, we indicate that small-intrusion metallogeny not only widely distributes in mafic-ultramafic intrusions, but also has an important economic value and scientific significance in intermediate-acid intrusions.

Genesis of the Jinchuan PGE deposit, China: evidence from fluid inclusions, mineralogy and geochemistry of precious elements

The Jinchuan deposit is a platinum group element (PGE)-rich sulfide deposit in China. Drilling and surface sampling show that three categories of platinum group element (PGE) mineralization occur; type I formed at magmatic temperatures, type II occurs in hydrothermally altered zones of the intrusion, and type III in sheared dunite and lherzolite. All ore types were analyzed for Os, Ir, Ru, Rh, Pd, Pt and Au, as well as for Cu, Ni, Co and S. Type I ore has (Pt + Pd)/(Os + Ir + Ru + Rh) ratios of <7 and relatively flat chondrite-normalized noble metal patterns; the platinum group minerals (PGM) are dominated by sperrylite and moncheite associated with chalcopyrite, pyrrhotite and pentlandite. Type II has (Pt + Pd)/(Os + Ir + Ru + Rh) ratios from 40 to 330 and noble metal distribution patterns with a positive slope; the most common PGM are sperrylite and Pd bismuthotelluride phases concentrated mostly at the margins of base metal sulfides. Type III ores have the highest (Pt + Pd)/(Os + Ir + Ru + Rh) ratios from 240 to 710; the most abundant PGM are sperrylite and phases of the Pt–Pd–Te–Bi–As–Cl system. It is concluded that the Jinchuan deposit formed as a result of primary magmatic crystallization followed by hydrothermal remobilization, transport, and deposition of the PGE.

Main Mineralization Mechanism of Magmatic Sulphide Deposits in China

AbstractBefore intruding, primary magmas have undergone liquation and partial crystallization at depth; as a result the magmas are partitioned into barren magma, ore–bearing magma, ore–rich magma and ore magma, which then ascend and are injected into the present locations once or multiple times, thus forming ore deposits. The above–mentioned mineralizing process is known as deep–seated magmatic liquation–injection mineralization. The volume of the barren magma is generally much larger than those of the ore—bearing magma, ore—rich magma and ore magma. In the ascending process, most of the barren magma intrudes into different locations or outpours onto the ground surface, forming intrusions or lava flows. The rest barren magma, ore–bearing magma, ore–rich magma and ore magma may either multiple times inject into the same space in which rocks and ores are formed or separately inject into different spaces in which rocks and ores are formed. The intrusions containing such deep–seated magmatic liquation–injection deposits have a much smaller volume, greater ore potential and higher ore grade than that of in–situ magmatic liquation deposits. Consequently this mineralizing process results in the formation of large deposits in small intrusions.

A general review of volcanogenic massive sulphide deposits in China

Volcanogenic, massive sulphide deposits in China have, for the past forty years, been an important source of Cu, Zn, Pb and sulphur, and of a number of associated elements such as Au, Ag and Co. The areal distribution of the deposits is determined by the different geological settings in which they occur and which range in time from Archean to Triassic. Host-rock lithologies comprise felsic, mafic and ultramafic metavolcanic rocks, with or without subsidiary, intercalated metasedimentary rocks; four groups of ore associations, based on chemical composition, have been distinguished: Cu, CuZn, CuFe and PbZnCu. Only one deposit of economic significance (Hongtoushan) has been recognised so far in an Archean greenstone belt. This ore is hosted by metafelsic volcanic rocks of a calc-alkaline suite. The Proterozoic was an important period for the formation of two groups of volcanogenic massive sulphide deposits in China. Early Proterozoic CuFe deposits, such as Dahongshan and Lalachang, are predominantly distributed in graben-like depressions within cratons. Late Proterozoic CuZn deposits, e.g., Xiqiu and Liujiaping, occur mainly along the edges of the craton. The ores of all Proterozoic deposits are hosted by quartz keratophyre. The most important metallogenic epoch for this type of ores in China was the Lower Palaeozoic and is represented by a number of deposits situated in the northern Qilian Caledonian orogenic belt. Within this belt, the various groups of deposits can be related to specific plate-tectonic settings. CuZn or PbZnCu ores occur in quartz-keratophyric tuffite, with or without intercalated sediments, of island-arc environments (Houyanshan, Zheyaoshan, Xiaotieshan); Cu ores are hosted by spilite, generated probably in back-arc basin settings (Honggou); while CuZn ores presumably occur in metabasalts of oceanic ridge or off axis settings (Yendonggou). Volcanogenic, massive sulphides are relatively unimportant in the Late Palaeozoic, both with regard to size and numbers, but a rather unusual and important CuZn deposit, hosted by ultramafic rocks (Deerni) is ascribed to this epoch. An important PbZnCu deposit (Gacun) that is comparable with the Kuroko deposits was formed in the Early Mesozoic Yidun orogenic belt, which is considered to represent a mature arc environment. The ores are hosted by rhyolites within calc-alkaline volcanites of dominantly andesitic and rhyolitic composition. The very important sedex-type stratabound and stratiform base-metal deposits in China seem to have occurred mainly at times when the volcanogenic massive sulphide deposits became relatively unimportant. For instance, the Early Proterozoic, Early Palaeozoic and Early Mesozoic, are the main periods for the formation of volcex-type massive sulphides, while the Middle Proterozoic and Middle-Late Palaeozoic are most important for sedex-type, stratiform base-metal sulphides.