湖南铲子坪金矿的矿物标型及其地质意义

Typomorphic Characteristics and Geological Implications of Minerals from the Chanziping Gold Deposit, Hunan Province

矿床位于白马山花岗岩外接触带附近，成矿阶段单一，矿物组份较复杂．金矿物颗粒细小，杂质少，成色高，硬度较高，与硫化物密切共生．石英以充填于构造空间的乳白色石英和交代构造岩的烟灰色、灰白色石英两种形式产出．二者同期共生，普遍发生塑性变形，含大量气液包裹体，气相成分以Ｈ２Ｏ和ＣＯ２为主，Ｈ２Ｏ＞＞ＣＯ２，贫Ｎ２，包裹体水的δ１８ＯＨ２ｏ比白马山花岗岩稍低．黄铁矿重结晶和动力变质现象普遍．五角十二面体、八面体黄铁矿的含金性好，立方体的含金性则较差．向深部，立方体黄铁矿减少，五角十二面体及其与立方体的聚形增多．黄铁矿的化学成分复杂，Ｓ／Ｆｅ＝１．９２—２．０２，亏硫；Ｃｏ／Ｎｉ平均为１．１７；Ｓｅ／Ｔｅ＝１２．４；Ｓ／Ｓｅ＝７．８×１０４；δ３４Ｓ分布于＋０．３２‰－７．５８‰的狭窄范围内．其晶胞参数（ａ０）与Ｃｏ、Ｎｉ、Ａｓ、Ｈｇ、Ｓｎ等质元素的含量相关．本矿床与胶东夏甸金矿类似，具有中－浅成中－低温岩浆热浪成因特点．成矿热浪来自白马山花岗岩，矿液由北向南，自西向东迁移．具大型矿床规模．矿床西部和Ⅰ矿脉带的深部有较好的找矿前景．

Lying at the exocontact zone of Baimashan granite in the Xuefengshan ductile nappebelt on the southeastern margin of the Yangtze massif, the gold deposit is an altered rocktype deposit in a structural shatter zone . Three NW-striking ore vein zones lie obliquely onthe eastern side of a SN-trending regional compresso-shear fault. The ore deposit wasformed through silicification, sericitization, pyritization and arsenopyritization of shearteasiletectonite , with the western part dominated by metasomatismand the eastern partcharacterized obviously by filling. The ore-forming epoch might be di vided into quartzpyrite-arsenopyrite stage, sulfide-native gold stage and quarta-carbonate stage .With Ag 0. 65%-26. 39% and small amounts of Fe and Cu , gold minerals are mainlynative gold, argentiferous native gold and, to a lesser amount, electrum. In the form ofxeno-morphic fine crystals, they have fineness of 736-993 (averagely 896) .In the shallow part , pyrite is mainly {100} ; toward the depth , combinations of (210} and {100} increase, and gold becomes richer . S/Fe=1. 92-2. 02, sulfur content is high, Co/Ni ratiosaveragel. 17, Se /Te=12. 4, S/Se=7. 8×104, δ34S values vary in the narrow range of+0. 32‰--7. 58‰, Au/Ag is as high as 12. 58%, as content averages 5816×10-6,similar to features of magmatic-hydrothermal gold deposits in eastern Shandong. Gas-liquidinclusions are numerous in quartz, being from 1μm to 18μm, with gas to liquid ratios5%-15% and homogenization temperatures 180-320℃. Gas phase is dominated by H2Oand CO2, and deficient in N2, H2O, HZO>>CO2, Na+/K+=0. 8-4. 47, CI->F-. Atthe quartz-pyrite-arsenopyrite stage, δ18 OH2o=0. 79‰-7. 14‰, similar to values ofBaimashan granite, and δDH2O=-54. 7‰-91. 2‰, suggesting character of magmatic water.The ore deposit was medium-low temperature magmatic-hydrothermal origin withorebodies formed at medium to shallow depths and hydrothermal solution migrating fromnorth to south and from west to east. It is medium-large sized, and ore-prospecting workis most promising in the western part as well as at depth of NO. I ore vein zone.