Abstract:

Based on field investigation and sampling from profile position within the Tongchanggou mine, mineral composition, geochemical characteristics and the ore type have been studied by microscope observation, petrochemical analysis, trace element analysis and scanning electron microscope analysis. The results indicate that there are two types of copper ore, the one is copper-containing sandstone type, and the other is altered structural breccia type. The sandstone-type copper mineralization has stratabound features and is controlled by the Triassic strata of the Feixianguan Formation. The structural breccia type copper ore bodies are controlled by faults extending in SW direction, and the copper grade change from 3.26% to 3.88%. Ore minerals in both types copper ore mainly include bornite, chalcopyrite, chalcocite, malachite, and minor in blue copper, native copper. The major wall-rock alterations include zeolite, barite-oriented, asphalt-based, silicification, chloritization, kaolinization and carbonation.The ratio of SiO₂/Al₂O₃,contents of such components as SiO₂, Na₂O, K₂O and CaO+MgO in the ore-hosting rocks of the sandstone-type copper deposit indicate that the ore-hosting sandstone is of marine origin. While the structural breccia type copper ore is resulted from the tectonic movement.

Key words: sedimentary copper deposit, altered brecciate copper deposit, geochemistry, copper deposit, Tongchanggou deposit in Hezhang area