成矿环境中的高密度碳质流体：以阿尔泰南缘为例

High density carbonic fluids in ore-forming environment:Evidences from the Southern Altaides,China

碳质流体(CO2-CH4-N2体系流体)常见于地幔橄榄岩和下地壳麻粒岩中。近期研究表明,阿尔泰南缘晚古生代成矿环境中的碳质流体极为丰富,不仅在造山型金矿中赋存大量与成矿有关的碳质流体,而且在VMS型矿床中也存在同造山期的变质碳质流体。由共生的富CO2包裹体(LCO2-LH2O型)和H2O-CO2包裹体(LH2O-LCO2型)的均一温度推测,造山型金矿的碳质流体捕获温度大于254～394.5℃,压力大于150～320MPa;VMS矿床的变质碳质流体捕获温度大于209～430℃,压力大于180～300MPa,两者具相似的捕获温度压力条件。碳质流体的捕获温度压力条件与变质相带相平衡计算的变质温度、压力范围相当。碳质流体源于区域变质作用,并参与了与造山型金矿有关的构造-变质-流体-成矿作用和对VMS型矿床的变质改造作用。

Carbonic fluids （CO2-CH4-N2 system fluids） were commonly found in mantle lherzolite and low crust granulite. Recent study shows that carbonic fluids are abundant in Late Paleozoic ore-forming environment in Southern Altaides. Not only were the ore-forming related carbonic fluid inclusions found in orogenic gold deposits,but also the coeval orogenic-metamorphic carbonic fluid inclusions were found in VMS deposits. The trapping temperatures of carbonic fluid inclusions may be higher than 254-394.5 ℃,and pressures higher than 150-320 MPa,based on associated CO2-rich （LCO2-LH2O） and H2O-CO2 inclusions （LH2O-LCO2）; while those of metamorphic carbonic fluids in VMS may be higher than 209-430 ℃ and 180-300 MPa,respectively. The trapping temperatures and pressures estimated from carbonic inclusions are approximate to those calculated from phase equilibrium of metamorphic zones in the area. Carbonic fluids were rooted in regional metamorphism,and played a role in the mineralization related to orogenic gold deposits and metamorphic-reconstruction of VMS deposits.