南天山萨恨托亥-大山口一带穆龙套型金矿床地质及地球化学特征

Geology and Geochemistry of the Muruntau Type Gold Deposits in the Sahentuohai-Dashankou Metallogenic Province, South Tianshan Mountains,China

南天山中段萨恨托亥 大山口成矿带内的金矿赋存在浅变质浊积岩系碎屑岩内。本文以该带内 2个典型金矿———大山口金矿和萨恨托亥金矿为例 ,对其成矿特征进行了初步研究。研究表明 ,金矿体受韧 脆性剪切带控制 ,产状稳定 ,矿石类型简单 ,硫化物种类单一且含量较低。成矿可分为糜棱岩阶段和石英脉阶段 ,与控矿的韧 脆性剪切带的发展演化各阶段相对应。成矿发生于中低温条件下弱酸性向中性环境过渡阶段 ,成矿流体是以深源流体 (含岩浆热液 )为主的多源混合热液 (构造热液 )。成矿作用为构造成岩成矿 (韧性剪切带成矿 ) ,矿床成因类型为(构造 )热液型金矿 ,成矿特征与穆龙套金矿类似。

Geological and geochemical characteristics of two typical gold deposits,Dashankuo and Sahentouhai,were studied,and the result shows that the deposits are controlled by the brittle ductile shear zones in northwestern zonal distribution in Dashakou Group.Gold orebodies in steady orientation consists of auriferous quartz veins and auriferous mylonite.Two types of gold ores can be distinguished:one is mylonite type with merely small amounts of sulfides,whereas the other is quartz vein type.The main alterations in the host rock include silicification,sericitization and ferrodolomitization.Two forms of mineralization can be defined,namely hydrothermal infiltration metasomatism and hydrothermal infilling.The formation of gold ores can be divided into two stages,i.e.,Au mylonite stage and Au_quartz vein stage.The ore vein ores contain abundant fluid inclusions which consist mainly of gas_liquid NaCl H 2O.Ore forming fluids are rich in Cl -,SO 2- 4,CO 2,Na + and K +,with w (NaCl eq ) of 0.85 % to 9.9 %.In the mineralizing stage,the density is 0.5611～0.9718 g/cm 3, f O 2 10 -41 ～10 -27 , f S 2 10 -5 ～10 -20 .The ores were formed at the temperature of 170～460 ℃ and under the pressure of 0.94 MPa to 32.2 MPa.According to characteristics of the stable isotopes C,H,O in ore forming solution and the comparison of Pb,S isotopes between gold ores and host rocks,the ore forming fluids consisted of deep-seated source ore solution,magmatic solution and underground water.The gold deposits created and controlled by brittle ductile shear zones in the metallogenic province have a close spatial,temporal and genetic relation to brittle ductile shear zones.They are Muruntau type deposits.