摘要
邦布金矿位于青藏高原雅鲁藏布江结合带东段的南侧,矿体受大型脆-韧性剪切带的次级断裂控制,是目前西藏境内已发现的为数不多的大型原生金矿之一。系统的显微测温和激光拉曼测定显示邦布金矿矿石中存在三类流体包裹体:(Ⅰ)纯液相水溶液包裹体;(Ⅱ)含CO2盐水溶液包裹体,此类包裹体又分为两相(Ⅱa)和三相(Ⅱb)两个小类;(Ⅲ)纯气相碳氢化合物包裹体。邦布金矿床中流体包裹体显微测温结果如下:含CO2盐水溶液包裹体的盐度范围为2.20%NaCleqv～9.45%NaCleqv,峰值在6.0%NaCleqv～7.0%NaCleqv,平均值为6.25%NaCleqv;均一温度的范围在166.7～335.8℃,峰值在210～250℃,平均值为235.4℃。相对应的密度范围在0.63～0.96g.cm-3,峰值为0.85～0.95g.cm-3,平均值为0.87g.cm-3。以含CO2盐水溶液包裹体为代表的邦布金矿床成矿流体具有富含CO2、低盐度、低密度、中低温度的特征,与造山型金矿成矿流体相似。同位素测定显示成矿流体的氢氧同位素组成分别为δDH2O=-44.4‰～-105.3‰,δ18OH2O=4.7‰～9.0‰,说明成矿流体主要为变质水,但有地幔流体的加入。综合成矿地质特征和成矿流体的证据,提出邦布金矿为喜马拉雅期陆陆碰撞造山型金矿。
Bangbu gold deposit is located to the south of the east section of the Yarlung Zangbo tectonic suture zone in the southern Tibet. The gold ore bodies are controlled by the secondary fractures in the large-scale brittle-ductile shear zone. It is a proved large-scale primary gold deposit in Tibet. Microthermometric measurements and Laser Raman analysis show that auriferous quartz veins of the Bangbu gold deposit contain three types of fluid inclusions:liquid aqueous inclusions (type I); CO2-bearing brine inclusions (type II),which can be subdivided into two-phase (type IIa) and three-phase (type IIb) inclusions; pure gaseous hydrocarbon inclusions (type III). The CO2-bearing brine inclusions have salinity values of 2.20% NaCleqv^9.45% NaCleqv,with a peak of 6.0% NaCleqv^7.0% NaCleqv and an average of 6.25% NaCleqv,homogenization temperature values of 166.7~335.8℃,with a peak of 210~250℃and an average of 235.4℃,and density values of 0.63~0.96g/cm3,with a peak of 0.85~0.95g/cm3 and an average of 0.87g/cm3,suggesting that the ore-forming fluids of the Bangbu gold deposit is characteristics by high content of CO2,low salinity,low to moderate homogenization temperature and low density,which are similar to those of typical orogenic gold deposits. Oxygen and hydrogen isotopic analyses show that δD and δ18O of the ore-forming fluids in the Bangbu gold deposit are-44.4‰^-105.3‰ and 4.7‰~9.0‰,respectively,indicating that the ore-forming fluids is composed mainly of metamorphic fluid,with addition of mantle-derived fluid. Geologic and geochemical features show that the Bangbu gold deposit may be a Cenozoic orogenic gold deposit formed under continental collisional background.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第6期1672-1684,共13页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划("973")项目(2009CB421006
2002CB412610)
国家自然科学基金(40830425
40873034
40673045)
中央高校基本科研业务费专项基金
高等学校博士学科点专项科研基金(200805580031)资助
关键词
流体包裹体
氢氧同位素组成
邦布金矿
藏南
碰撞造山型金矿
Fluid inclusion
H-O isotopic composition
Bangbu gold deposit
Southern Tibet
Orogenic gold deposit
