泰国西部比洛克(Pilok)锡钨矿流体包裹体研究及矿床成因

Fluid inclusion analysis and origin of the Pilok tin-tungsten deposit in western Thailand

关键词:  钨锡矿  流体包裹体  找矿远景  泰国比洛克  东南亚

Key words:  tin-tungsten deposit  fluid inclusion  prospect  Pilok in Thailand  Southeast Asia

摘要:

对泰缅毗邻区比洛克锡钨矿区含矿石英脉进行了流体包裹体分析。包裹体岩相学研究表明,流体主要为富液相包裹体和H₂ O-CO₂三相包裹体。显微测温分析结果显示,均一温度为200~350℃,盐度(w (NaCl))为0.43%~12.42%,石英脉中H₂ O-CO₂三相包裹体成矿压力为102~350mPa,估算成矿深度在0.34~1.37 km。这些数据表明,石英脉型钨锡矿主要形成于岩浆演化晚期的中高温岩体顶部。结合前人稳定同位素等分析结果,认为比洛克锡钨矿存在4个矿化阶段:(1)早期高温产于细粒花岗岩内的黑钨矿±锡石±黄铁矿矿化;(2)与石英±钾长石脉有关的黑钨矿矿化;(3)叠加在中期钾化和钨矿化上的云英岩型锡矿化;(4)晚期中高温(220~350℃)低盐度(< 5% NaCl_eq.)混合流体为主的石英脉型钨锡矿化。结合研究区的区域构造演化及岩浆演化特征研究,建立了比洛克锡钨矿的找矿模型,并对该区进一步找矿提出建议。

Abstract:

The fluid inclusion analysis is carried out in this study for the ore-bearing quartz veins from the Pilok tin-tungsten deposit in western Thailand. The fluid inclusions herein consist dominantly of liquid-rich inclusions and H₂O-CO₂ three-phase inclusions. The microthermometric analysis indicates that these inclusions have the homogenization temperatures ranging between 200 and 350℃, the salinities between 0.43% and 12.42%, metallogenic pressures between 102 and 350 mPa, and estimated metallogenic depths between 0.34 and 1.37 km. All these data show that the quartz vein-type tin-tungsten deposit was formed in the topmost part of the mesothermal to high-temperature granites during the late stages of magmatic evolution. Referenced to the previous results, the Pilok tin-tungsten deposit has witnessed four stages of mineralization, including:(1) pegmatite-hosted wolframite ±cassiterite ±pyrite mineralization during the earlier high-temperature stage; (2) wolframite mineralization associated with quartz ±K-feldspar veins; (3) greisen-type tin mineralization following K-feldspar alteration and tungsten mineralization during the middle stage, and (4) quartz vein-type tin-tungsten mineralization characterized by mixed fluids with mesothermal to high-temperature (220-350℃) and low salinities (< 5% NaCl_eq.) during the late stage. A metallogenetic model is constructed on the basis of the geology of the Pilok tin-tungsten deposit and regional tectonic evolution. The western Taninthayi Mountains in Myanmar are believed to be highly prospective for the exploration of the quartz vein-type or greisen-type tin-tungsten deposits.