Gao Zhenmin

A kinetic study of the oxidation of arsenopyrite in acidic solutions: implications for the environment

Arsenopyrite is an important component of many ore deposits and dissolves in the O2-rich, acidic surface waters that are commonly found in the vicinity of active mines, releasing As, Fe and S to the environment. However, despite the potentially serious effect of this pollution on the human and animal population, the rate at which such oxidation occurs is poorly known. Kinetic experiments were therefore conducted in a mixed flow reactor to investigate the oxidation of

Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-elementore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element- oredeposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

Silicalites of hydrothermal origin in the Lower Cambrian black rock series of South China

A silicalite bed was found in the hanging wall and foot wall of the sulfide-rich bed of the Lower Cambrian black rock series in South China. Its origin was not described before. On the oxide (SiO2-Al2O3, SiO2-MgO, SiO2-K2O + Na2O) diagrams for discriminating silicalites of chemical, biological and volcanic origins (Liu Xiufeng, 1991), most of the data points of silicalites fall within the areas representing silicalites of chemical and volcanic origins. On the Al-Fe-Mn diagram for discriminating silicalites of hydrothermal and biological origins (Yamamoto, 1987), the data points fall within the areas representing silicalites of hydrothermal and hydrothermal-biological origins. On the SiO2-Al2O3 diagram for discriminating silicalites of hydrothermal and hydrogenous origins (Bonatti, 1975), the data points mostly fall within the hydrothermal area. The ratios of SiO2/Al2O3, SiO2/(K2O+ Na2O), SiO2/MgO, and K2O/ Na2O in the silicalites stand between those of volcanic sediments and of seafloor hydrothermal sediments. The total amount of rare-earth elements in the silicalites is low; the North American Shale-normalized REE patterns decline leftward with obvious negative Ce anomaly. The trace elements Mo, Zn, As, Sb, Se, U, and Ba are higher than those in non-hydrothermal sediments and U/Th ≥1. The present authors think that the silicalites are derived from seafloor hot brines which had attracted elements from igneous rocks.

Na-rich microlite-glass in deep xenoliths, Liuhe, Yunnan: discovery and implications

Abstract Na-rich microlite-glass is discovered in deep-source xenoliths in sodium-rich porphyry, Liuhe village, Heqing County, Yunnan Province. Our study shows that the glass originated from mantle fluid through metasomatism. Based on clinopyroxene geothermometry and geobarometry, coupled with the time lap between the xenoliths and the porphyry host rock, it is considered that mantle metasomatism not only resulted in the enrichment of alkaline and large-ion elements leading to the concentration of ore metals and volatiles but also created a favorable condition for the generation of alkaline magmas which were intruded extensively during the Himalayan orogeny with extensive mineralization. The discovery of microlite-glass provides important evidence for a better understanding of this geologic event.

Super-enrichment of dispersed elements and associated ore deposits

Dispersed elements do not always occur as associated elements in the ore deposits of other elements. Instead, they can constitute independent ore deposits. The focus of this paper is placed on the mechanism of super-enrichment of the four dispersed elements Tl, Ge, Se, and Te under favorable geological conditions, where their enrichment coefficients are so high that their abundances can reach n x 103-n × 104, sometimes even up to n X 106 times (e. g. Te) those of the crust. As a result, they can form their independent ore deposits. Studies have shown that such independent ore deposits are mostly distributed in the southwestern part of China, most of which belong to low-temperature ore deposits, ranging in age from Yanshanian to Himalayan (Cretaceous to Cenozoic), with a significant time gap with the host strata. Moreover, this paper also deals with the existing forms (as independent minerals, occurring isomorphously and being adsorbed) of the dispersed elements in those independent ore deposits. The discovery of independent ore deposits of dispersed elements is a great breakthrough in the study of dispersed element metallogenesis.