西藏丁青县扎格拉金矿床地质特征、流体包裹体特征及成因

Geological characteristics and petrogenesis of the Zhagela gold deposit in Dingqing,Tibet

扎格拉金矿位于班公湖一怒江结合带东段及冈底斯一念青唐古拉板片北缘的腾冲一班戈岩浆弧带上,受被动陆缘深海复理石建造、脆一韧性剪切带和深成岩浆活动控制。流体包裹体类型以单相和A型两相盐水溶液包裹体为主,次为B型两相盐水溶液包裹体、富CO_2两相包裹体和含CO_2三相包裹体,成矿流体属中低温和中低盐度H_2O-NaCl-CO_2体系。氢、氧同位素和相对富含K^+、Na^+、Ca^(2+)、Mg^(2+)、Cl^-、SO_4^(2-)的包裹体液相成分,显示成矿流体主要来自长期封存于沉积岩的深循环热(卤)水中,矿床成因类型为浅成中低温地下热(卤)水溶滤型金矿床。其成矿特征和流体性质与穆龙套型金矿床具有诸多相似性,研究该区域对西藏"沙丁板岩系"分布区金铜多金属找矿具有重要意义。

The Zhalage gold deposit is located in the Tengchong-Bange magmatic arc at the northern margin of the Gangdese-Nianqingtanggula terrane,in the eastern part of the Bangong-Nujiang suture.Its occurrence is controlled by a suite of abyssal flysch,brittle-ductile shear zone,and plutonic magma activity.The fluid inclusions are mainly of single-phase or A-type double-phase salt-water systems,and subordinately B-type double-phase or CO2-enriched double-and three-phase salt-water systems.The ore-forming fluid belongs to an epithermal to mesothermal （120 ℃～340 C）H2O-NaCl-CO2 system with low to moderate salinity（6.4%～ 14%）.The hydrogen and oxygen isotopes and the liquid phase composition of the fluid inclusions which are enriched in K^＋,Na^＋,Ca^2＋,Mg^2＋,Cl^-,SO4^2-indicate that the ore-forming fluids were dominantly deep-circulating hot brine water that is chronically stored within the sedimentary rocks.The gold deposit was formed through leaching by hot brine water under hypabyssal epithermal-mesothermal conditions.The Zhalage gold deposit resembles the Muruntau gold deposit in terms of ore-forming geological background,and the characteristics of ore geology and ore-forming fluid.It is likely that a breakthrough can be achieved if more invests can be put for the exploration of the ＂sandin slate＂ gold-copper polymetallic ore in the region.