矿床地质2009，Vol.28Issue(5)：539-557,19.
滇黔桂"金三角"卡林型金矿含砷黄铁矿和毒砂的矿物学研究
Mineralogy of arsenian pyrites and arsenopyrites of Carlin-type gold deposits in Yunnan-Guizhou-Guangxi "golden triangle" area, southwestern China
摘要
Abstract
Petrographic observations and electron-probe micro-analysis (EPMA) of sulfides from different subclasses of typical Carlin-type gold deposits in Yunnan-Guizhou-Guangxi "golden triangle" area show that both arsenian pyrites and arsenopyrites are major gold-bearing minerals. Gold-bearing pyrites are dominated by zoned arsenic pyrites and fine-grained euhedral arsenian pyrites. Zoned arse-nian pyrites are characteristies by As-poor and S, Fe-rich cores manded by later-formed As-rich and S, Fe-poor rims, and there is a positive correlation between Au and As. Pyrites with As-poor cores have complex origin, with sctne being hydrothermal pyrites pre-cipitated in the early metallogenic stage and the others being syngenetie pyrites altered by hydrothermal fluid. Core pyrite and rim pyrite were formed in different metallogenic stages. The correlation between element contents indicates S was replaced by As in rims. The characteristics of multi-rims suggest that the hydrothermal fluid acted pulsatorily and the components of hydrothermal fluid varied eonstantly. Even if Au of some analytical spots from the cores exceeds the detection limit, rims can serve as the primary gold-bearing location. The fine-grained euhedral arsenian pyrites with homogeneous texture are similar to the rims of zoned pyrite with characteris-tics of high As, Au and low S, Fe, indicating that the As-rich mandes of zoned pyrite were probably formed synchronously with the As-rich tiny euhedral arsenian pyrite. The pyrites from the aggregation of pyrite-arsenopyrite are classified into two groups, which are of zoned textttre and homogeneous texture and have the characteristics of the above two types of pyrites respectively. Arsenopyrites are subdivided into three generations, all having homogeneous texture and belonging to hydrothermal precipitation. There are some ana-lytical spots from every generation whose Au exceeds the detection limit and whose contents of Au, As, S, Fe are different insignifi-candy in different generations, indicating they were deposited in the main metaUogenic stage. The arsenopyrites have higher Au abun-dances than pyrites in the aggregation of pyrite-arsenopyrite. The precipitation order of gold-bearing sulfides is as follows: As-poor sedimentary pyrites or early metallogenie stage pyrites → As-rich zoned arsenian pyrites and fine-grained euhedral arsenian pyrites →arsenopyrites. The distribution of Au in all types of pyrites and all generations of arsenopyrites is heterogeneous under the resolution of EPMA microbeam, and the homogeneous texture of Au map from zoned arsenic pyrites is likely to be a pseudomorph. The major modes of occurrence for gold are "invisible" nanometer-size sub-mimic inclusion gold grains, with minor ones being "invisible" lattice gold and "visible" micrometer-size microscopic native gold. The gold-bearing minerals and the gold modes of occurrence have no essential difference in different subclasses of Carlin-type gold deposits in Yurman-Guizhou-Cuangxi "golden triangle" area, suggesting that they had the same ore-forming process and setting.关键词
地质学/含砷黄铁矿/毒砂/金的赋存状态/卡林型金矿/滇黔桂"金三角"Key words
geology/arsenian pyrites/arsenopyrites/gold occurrence/Carlin-type gold deposit/Yunnan-Guizhou-Gnangxi "golden triangle" area分类
天文与地球科学引用本文复制引用
陈懋弘,毛景文,陈振宇,章伟..滇黔桂"金三角"卡林型金矿含砷黄铁矿和毒砂的矿物学研究[J].矿床地质,2009,28(5):539-557,19.基金项目
本文得到"中央级公益性科研院所基本科研业务费专项资金"(K2007-1-2)、"中国博士后科学基金"(20080430456)和"国家重点基础研究发展计划"(973计划)(2007CIMll407)的联合资助 （K2007-1-2）
