甘肃阳山金矿床微量元素及稳定同位素的地球化学研究

甘肃省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 ,均赋存于浅变质的泥盆系地层中。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、黄铁矿及粘土矿物之中。矿床微量元素含量研究表明 ,矿石中Au、Hg、As、Bi、Sb等元素较为富集 ,并且其间呈明显的正相关关系 ,显示阳山金矿的形成与富含Au、Hg、As、Bi、Sb等低温热液元素的成矿流体活动有关 ,向深部这些元素含量趋于降低 ,表明成矿流体活动趋弱。矿石石英的δD值为 - 6 0‰～ - 72‰ ,δ18OH2 O值为 8 0‰～ 10 1‰ ,表明成矿流体主要为岩浆热液 ;矿石黄铁矿的δ3 4 S值为 - 2 2‰～ - 0 7‰ ,不同于泥盆系地层中沉积黄铁矿的δ3 4 S值 (10 9‰ ) ,表明矿石硫为岩浆硫 ,因而阳山金矿床的形成与岩浆热液活动密切相关

GEOLOGICAL AND MICROELEMENT GEOCHEMICAL STUDY OF YANGSHAN GOLD DEPOSIT,GANSU PROVINCE

The Yangshan gold deposit, located in south Gansu Province, is a supper large fine-grained disseminated gold deposit recently found in China. Four discovered ore blocks of the deposit all occur in Devonian epimetamorphised sandstone, phyllite or limestone. The ore belt is controlled by Anchanghe-Guanyinba fault as well as its secondary faults. The orebodies, being in lenticular or veinlike forms, are spatially related to plagiogranite. Pyrite and arsenopyrite are the main metallic minerals and native gold usually occurs in pyrite, arsenopyrite and clay minerals as micrograined inclusions (2～3μm).Enrichment of Au,Hg,As,Bi,Sb in the ore is obvious and such elements show positive correlations with each other, indicating that the forming of the Yangshan gold deposit is associated with the activity of hypothermal ore fluid containing Au,Hg,As,Bi,Sb. The decrease of these elements from the upper part to the lower part of the deposit show that the activity of the ore fluid become weak along with the depth. The δ D value of quartz from the ore ranges from -60‰ to -72‰, and δ ~(18)O (H 2O) value ranges from 8.0‰～10.1‰, indicating the ore fluid is mainly composed of magmatic water. The δ ~(34)S value of pyrite from the ore ranges from -2.2‰ to -0.7‰, which is greatly different from that of pyrite in Devonian phyllite, suggesting the magmatic origin of the sulfur, therefore it is proposed that the Yangshan gold deposit is genetically related to the magmatic thermal activity.