THE GENESIS OF THE CHENGMENSHAN AND WUSHAN COPPER DEPOSITS
Huang Enbang, Zhang Naitang and Luo Zhaosheng(Northwest Jiangxi Geological Party, Bureau of Geology and Mineral Resources of Jiangxi Province, Jiujiang, Jiangxi)
The Chengmenshan and Wushan copper deposits are two rather typical "several types in one system" copper deposits in middle and lower reaches of the Yangtze River. Metallization is controlled by deep-source epizonalsuperepizonal intermediate-acid complexes, ore deposits are closely related to intrusive bodies in time and space, and ore-forming elements and mineralizer elements of orebodies assume zonal distribution around the intrusive body; the specialization of chemical composition of rocks and the highly-abundant metallic elements in rock bodies are consistent with ore-forming element associations of the ore deposits. The regional NWW-trending tectomagmatic belt controls the stretching of the orebelt. The intersections of NW-, NE-and NEE-, NNE-trending faults of different grades seem to be the localities of ore fields and ore deposits. The fissure zones within rock bodies, the contact zone between the rock body and the Carboniferous-Triassic limes- tone, and cataclastic zone between the clastic rock of Wutong Formation and the carbonate rock of Huanglong Formation outside the rock body control the production of porphyry type orebodies, sharn type orebodies and stratiform sulfide type orebodies respectively. The stratiform sulfide type copper deposit bears close resemblance to its associated porphyry type and skarn type copper deposits in a series of characteristics such as zoning of ore-forming elements, Co/Ni and S/Se ratios of pyrite, stable isotopes (δ~(34)S, δ~(18)O_(H_2O), δD_(H_2O), ~(206)Pb/~(204)Pb, ~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb) and ore-forming temperatures; nevertheless, these deposits are obviously different from typical sedimentary type, volcanogene sedimentary type and sedimento-metamorphic or hydrothermal superimposed stratabouud deposits. The above characteristics further prove that the three types of copper orebodises are a set of internally-related ore deposits formed when ore fluids entered different structural-wall rock spaces under the action of the same magmatic-hydrothermal action. It is thus uggested that they should be named skarn "three types in one system" metallogenic model in a broad sense.