摘要
驼路沟矿床是容矿于震旦—寒武纪富钠火山_沉积岩系中的钴 (金 )矿床。矿床地质_地球化学特征、矿体的产态、矿石结构构造以及金属矿物的标型表明 ,驼路沟钴 (金 )矿床主要与震旦—寒武纪海底喷气沉积成矿作用有关 ,在加里东和晚华力西—印支碰撞造山过程中 ,喷气沉积型矿体被构造改造 ,并导致金在局部地段进一步富集。元素地球化学研究揭示 ,Au、As、Pb、Cu、Zn、Mo、Co是圈定含矿层的化探异常元素组合 ,而Co_Ni_Au_Pb_Mo_As组合异常可以指示矿体。
The Tuolugou cobalt_gold deposit, located in the central part of the East Kunlun orogen, serves as the first example of exhalative_sedimentary deposits in this region and is now under exploration. Lithologies of Co_ and Au_bearing formation in the Tuolugou ore district include detrital and volcanic rocks of four lithostratigraphic sub_units, which are from bottom to top black shale (Z_DC- a ) , tuff_sandstone (Z_DC- b ) , volcano_sedimentary rocks (Z_DC- c ) and sandstone (Z_DC- d ) . There are no intrusive rocks involved in the Tuolugou ore district. Volcanics in four sub_units are intermediate to acidic and show a chemical affinity of active continental margin or island arc. The cobalt_gold ore bed is hosted by volcano_sedimentary rocks (Z_DC- c ) , whose sequence is mainly composed of metamorphosed pelitic siltstone with interbeds of tuff and exhalite (quartz albitite). U_Pb dating data (570 Ma) obtained from zircon of quartz albitite indicate an age between Sinian and Cambrian. Co_Au orebodies are in stratiform and lenticular forms. They extend conformably in strata, forming an over 7 km_long mineralization zone. Individual orebodies are 100 to 1?000 m long and 0.86 to 4.45 m thick, with average grades of 0.024%～0.108% Co and 0.3～0.78 g/t Au. The ores display laminar, banded, disseminated and massive textures. The gangue minerals include quartz, albite, carbonate (siderite, ankerite and calcite), sericite, chlorite and tourmaline (dravite), whereas the ore minerals are composed of pyrite (>30%), small amounts of arsenopyrite, chalcopyrite, sphalerite pyrrhotite, bornite, and trace cobalt pentlandite, cobalt pyrite, linnaeite, carrollite, cattierite and gold. Cobalt is contained in pyrite in the ore. The multiple orogeny during Caledonian and Late Variscan to Indosinian produced extensive metamorphism and deformation, and led to the development of folds that evolved into thrusts. This caused reformation of exhalative_sedimentary orebodies and partial emplacement of gold orebodies. The complex ore_forming process mentioned above finds expression in variable generations of pyrite in Co_Au ores. Pyrite of early generation is anhedral, fine_grained and fragmented, with quartz, calcite and gold filled in microfractures. Pyrite of early generation is sometimes seen to be elongated into spindle_shaped crystalloblasts. Pyrite of late generation is of a lower proportion relative to early pyrite, and is subhedral to euhedral and coarse_grained in form with no fragmentation. Microprobe analyses show that early pyrite has high average content of Co and Ni, and low Au (2.44% Co, 0.49% Ni and 0.01% Au) relative to late pyrite (0.1% Co, 0.1% Ni and 0.14% Au). All this suggests that early pyrite and late pyrite were formed before regional metamorphism and deformation (exhalative_sedimentary stage) and during metamorphic and deformation stage, respectively, and that cobalt mineralization is mainly related to exhalative_sedimentary mineralization, whereas gold is mainly an epigenetic product related to collisional orogeny.
出处
《矿床地质》
CAS
CSCD
北大核心
2002年第3期213-222,共10页
Mineral Deposits
基金
国土资源部"九五"科技发展计划项目 (95_0 2_0 0 5 )
国家地质调查项目 (K1.1.3 .1及 2 0 0 110 0 0 0 0 0 1)的部分成果
关键词
钴矿床
喷气沉积矿床
金矿床
地球化学
成矿作用
cobalt deposit, exhalative_sedimentary mineralization, Tuolugou, East Kunlun
