甘肃省文县阳山特大型金矿床地质特征及控矿因素分析

Geological Features and Ore-Controlling Factors of the Yangshan Superlarge Gold Deposit, Gansu Province, China

阳山金矿位于川陕甘交界地带,为近年发现的一特大微细浸染型金矿床。该矿目前已发现4个矿段,均赋存于泥盆系中。矿体在平面上呈舒缓波状,在剖面上为脉状、似层状。矿石中金属矿物主要为黄铁矿和毒砂,金主要以微细粒金(2～3μm)包裹于毒砂、黄铁矿等矿物之中。矿石中As、Sb及有机碳含量较高。矿带受安昌河—观音坝断裂带控制,矿体产于断裂带内的次级断裂中;泥盆系三河口群粉砂质千枚岩渗透性较好,且碳质含量、金丰度值较高,是矿区最有利的赋矿层位;矿体在时间、空间上与侏罗纪早期岩浆活动密切相关,稳定同位素分析也表明成矿作用与岩浆活动有关;所以,该矿为受构造直接控制的、与沉积作用和岩浆活动有成因联系的金矿床。

The Yangshan gold deposit, located in Wenxian County, southern Gansu Province, is a superlarge gold deposit discovered in 1997. Four ore segments were found for the deposit, all occuring in Devonian epimetamor-phosed sandstone, phyllite or limestone. The orebodies are horizontally in a gentle wave form and vertically in a lenticular or veinlike form. Pyrite and arsenopyrite are the main metallic minerals, which usually contain micro-grained native gold (2-3μm). The As, Sb and C contents are high in the ores. The ore belt is controlled by the Anchanghe-Guanyinba fault, and the orebodies found all occur in its secondary faults. With high C and Au contents, the permeable phyllites of the Middle Devonian Sanhekou Group are the most favourite host rock in the deposit. The orebodies are spatially and temporally related to the early Yanshanian plagiogranite. Isotopic analysis also indicates that the ore-forming process is related to magmatic activity. Therefore, the Yangshan gold deposit is a deposit directly controlled by the fault zone and genetically related to the Devonian sedimentation process and Yanshanian magmatic activities.