河南省嵩县槐树坪金矿床地质、同位素地球化学特征与成矿作用

Geology,isotopic geochemistry and metallogenesis of Huaishuping gold deposit in Songxian County,Henan Province

河南嵩县槐树坪金矿床是豫西地区近年来通过勘查找矿评价出来的大型金矿床,该矿赋存于中元古界熊耳群火山岩地层,受断裂构造控制,与燕山期酸性岩浆侵入活动密切相关,是典型的构造蚀变岩型金矿床。矿区断裂构造可分为陡倾切层断裂和缓倾层间破碎带2种类型,缓倾层间破碎带是最重要的控矿和容矿构造,也是实现找矿突破的关键。氢、氧同位素分析显示,石英的δ^(18)OV_SMOW值变化于10.1‰~14.4‰,成矿流体δ^(18)OH_2O变化于-1.3‰~7.3‰,δD变化于-95‰^-81‰;矿石硫同位素分析显示,δ^(34)S值变化于-7.7‰^-1.4‰;矿石铅同位素分析显示,206Pb/204Pb变化于16.990~18.761,207Pb/204Pb变化于15.368~15.622,208Pb/204Pb变化于37.471~38.730。研究结果表明,槐树坪金矿床的成矿流体主要由岩浆水和大气降水组成,成矿主阶段以岩浆水为主,晚期有较多大气降水的加入;成矿物质主要来源于(直接或间接)太华群地层。该矿床的成矿过程经历了早期变形、变质作用的预富集,并于中生代后碰撞伸展构造环境下大规模富集成矿。

The Huaishuping gold deposit in Songxian County of Henan Province is a large-size gold deposit found by exploration work in recent years. It is hosted by the Mesoproterozoic Xiong＇er Group and closely related to the Mesozoic magmatism. The orebodies are controlled by faults. It is a typical tectonic altered rock type gold de- posit. The fault in the mining area can be divided into steeply inclined incision faults and gently inclined interfor- mational faults, with the latter being the most important ore-controlling and ore-bearing structure. And this is the key to achieving breakthrough in prospecting. Oxygen and hydrogen isotope data from quartz show that the δ^18Ov_sMOW values range from 10.1‰ to 14.4‰0, δ^18H2O values from - 1.3‰ to 7.3‰0, and δD values between -95‰ and -81‰. The 834S values of sulfides range from -7.7‰ to - 1.4‰. Among Pb isotopes, the ^206pb/^204pb and ^207pb/^204pb ratios of sulfides are in the range of 16. 990 to 18.761 and 15.368 to 15.622, respectively, and ^208pb/^204pb ratios from 37. 471 to 38. 730. The authors revealed that the ore-forming fluids of the Huaishuping gold deposit were composed of magmatic and meteoric water, the ore-forming fluid of main metallogenic stage mainly came from the magma, with the addition of more meteoric water at the late stage. The ore-forming materials were mainly derived from the Taihua Group. The Huaishuping gold deposit under- went preconcentration at the early stage by deformation and metamorphism, and large-scale gold enrichment and mineralization took place in a post-collisional extensional setting in Mesozoic.