广西东兰某地微粒型金矿地质特征和成因分析

GEOLOGICAL CHARACTERISTIC OR ORIGIN ANALYSIS OF A MICRO- FINE GRAIN GOLD ORE DEPOSIT AT DONGLAN OF GUANGXI

东兰金矿产于中三叠世早期板纳组复理石沉积建造层间破碎硅化蚀变带中。矿体呈层状，似层状和脉状。矿石类型为褐铁矿化破碎硅化砂岩、石英细脉和层状复理石韵律矿石。含金矿物主要为褐铁矿、黄铁矿和有机质。具有层间破碎、碎粒、沉积结构构造特征，属典型成岩—后生型层控矿床。矿床成因与生物礁的消失、碎屑流事件、深水火山碎屑泥质上超盆地靠近天峨孤立碳酸盐台地缓坡深水沉积部位、复理石浊积岩相、印支期天峨背斜东南翼层间破碎硅化蚀变带，以及有机质的热解和分异有关。

Donglan gold ore deposit has been found in interstratified fractured silicic alteration belt within flych sedimentary formation of lower Banna formation of midle Triassic. Ore bodies are bedded,bedded-alike, vein. Ore types are limonite fractured silicic sandstone, quartz veinlet and bedded flych rhythm ore. Gold-bearing minerals are mainly limonite, pyrite and organic material. They have the characteristic of interstratified fractured, crashed stone, sedimentary texture and structure feature which show this deposit belonging to the type diagenetic-epigenetic stratabound ore deposit. The deposit origin are close to organic reefs extinct, detritus flood event, deep water volcanic clastic with mud which cover the basin near Tian'e isolated carbonate platform slope, flych turbidite facies, interstratified fractured silicic alteration zone of southeast Tian'e anticline of Indo-Chinese epoch, the thermolysis and differentition of organic material.