Mineralized characteristics of Tr Năng initial gold deposit in Lm Đồng Province

Nguyễn Kim Hong, Nguyễn Văn Mai

The geological structure of Tr Năng initial gold deposit is composed of gold ore bodies, which are mainly consist of siltstone, shale alternating little grey, dark grey layers of sandstone and are assigned to the La Nga Formation. They were folded with the fold axis to the NE - sw direction. Gold ore bodies were in the forms of veins, sheeted-veins, network-veins, vein-zones; sometimes: shoots, nests. The dip direction of ore bodies are southeast or northwest with angle of dip are 45-70. The ore mineral associations are mainly presented by pyrite, arsenopyrite; secondary galena, sphalerite, chalcopyrite, occupying 10-15%. Gold exists as native gold (generation I), and electrum (generation II). The most common gangue mineral is quartz (>80%). Ore structure mainly are dissemination, veinlet; ore texture mainly are panautomorphic, half- panautomorphic, leptomorphic, fram, and emulsion. Gold in the ore bodies are distributed not equally with content of Au element varies from 1-2 g/T to 40-50 g/T. The gold metallization genesis is between medium and low-medium temperature hydrothermal, related to Late Mesozoic intrusive magmatic activities. The process of gold mineralization formation consists of 3 stages with 2 main paragenetic mineral association: 1) quartz I - arsenopyrite I - pyrite I - native gold (305-250C; 2) quartz II - pyrite II - galena - sphalerite - chalcopyrite - electrum (26CH-195C). The gold deposit type is vein-shaped gold-quartz-sulphide; mineralisation types are: gold - quart - pyrite - arsenopyrite (main) and gold - quartz - polymetallic sulphide (secondary). On the degree of geological and geochemical denudation of ore, gold mineralization had denuded from ore middle zone to upper part of lower ore zone. Therefore, the Tra Nang initial gold deposit is considered as high promising.

Người bin tập: PGS. TS Nguyễn Quang Luật.