滇黔交界地区玄武岩铜矿同位素地球化学特征

Isotopic Geochemistry of Emeishan Basalt Copper Deposits in Northeastern Yunnan and Western Guizhou

对滇黔交界地区玄武岩铜矿进行了同位素地球化学示踪。铜矿石中沥青δ1 3 CPDB为 - 33.1‰～- 30 .9‰ ,炭质δ1 3 CPDB为 - 2 3.2‰～ - 2 0 .2‰ ;方解石的δ1 3 CPDB一般为 - 1 3.5‰～ - 1 9.4‰ ,δ1 8OSMOW 一般为1 9.0‰～ 2 3.5‰ ;石英流体包裹体水δD为 - 6 9‰～ - 89‰ ,δ1 8O石英_SMOW 为 1 5 .7‰～ 1 7.4‰ ,与其平衡的流体的δ1 8O水_SMOW为 2 .2‰～ 3.9‰ ;各种矿物的铅同位素组成一般为2 0 6Pb/ 2 0 4Pb 1 7.85 5～ 1 8.92 3,2 0 7Pb/ 2 0 4Pb 1 5 .5 0 3～1 5 .6 94 ,2 0 8Pb/ 2 0 4Pb 38.2 93～ 39.0 36 ;辉铜矿δ3 4 SCDT为 1 9.2‰和 2 0 .7‰。这些特征综合显示峨眉山玄武岩铜矿的成矿作用与盆地流体的对流循环及从玄武岩中萃取成矿物质有关 。

This paper has studied isotopic geochemistry of basalt copper deposits in northeast Yunnan Province and west Guizhou Province. δ 13 C V-PDB of bitumen from copper ore in basalts and carbonaceous matter from copper ore in carbonaceous sedimentary rocks are from -33.1‰ to -30.9‰ and from -23.2‰ to -20.2‰, respectively. δ 13 C V-PDB and δ 18 O V-SMOW of calcite from copper ore are generally from -13.5‰ to -19.4‰ and from 19.0‰ to 23.5‰, respectively. δD V-SMOW and δ 18 O V-SMOW of quartz from copper ore are from -69‰ to -89‰ and from 15.7‰ to 17.4‰, respectively, and the δ 18 O H 2O-SMOW of fluids are from 2.2‰ to 3.9‰. 206 Pb/ 204 Pb , 207 Pb/ 204 Pb and 208 Pb/ 204 Pb of minerals from copper deposits are generally from 17.855 to 18.923, from 15.503 to 15.694 and from 38.293 to 39.036, respectively. The δ 34 S V-CDT of chalcocite from copper ore are 19.2 ‰ and 20.7‰. All these data suggest that Emeishan basalt copper deposits are epigenetic hydrothermal ones, and their mineralization is related to the convection of basin fluid and its extraction of copper from basalt as well as to the reduction and adsorption action of organic matters.