A general review of volcanogenic massive sulphide deposits in China

Abstract

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.