滇西叫鸡冠梁子铁多金属矿床成因及成矿流体来源探讨——来自方解石流体包裹体证据

Ore-forming fluid source and genesis analysis of Jiaojiguanliangzi Fe polymetallic deposit in West Yunnan:an evidence from calcite fluid inclusion

叫鸡冠梁子铁多金属矿床位于滇西腾冲市中缅边境附近,矿体主要呈似层状、透镜状产于二叠系空树河组中。选取成矿过程中氧化物阶段和硫化物阶段方解石流体包裹体进行岩相学观察及测温实验,得出四种类型的流体包裹体在氧化物阶段均一温度集中于268℃~337℃,盐度w(NaCleq)=5.26%~8.28%,pH=5.68~5.73;在硫化物阶段均一温度集中于173℃~205℃,盐度w(NaCleq)=1.29%~4.85%,pH=5.63~5.70,两阶段的成矿流体具有中高到低温、中低到低盐度以及弱酸性的变化特征。成矿压力为(411.46~919.49)×10^(5)Pa,相当于深度1.52~3.41 km,暗示该矿床成矿深度较浅,成矿作用在逐渐减压的环境中进行。综上及矽卡岩矿物组构特征,认为该矿床的成矿流体主要来源于岩浆热液,上移过程中与围岩发生了水岩反应,具有近端矽卡岩型矿床成因的特征。

The Jiaojiguanliangzi iron polymetallic deposit is located near the border between China and Myanmar in Tengchong City,West Yunnan,in which the ore body is mainly hosted at the Permian Hollow River Formation in layered and lenticular shape.In this paper,calcite fluid inclusions in the oxide stage and sulfide stage in the mineralization process are selected for petrographic observation and temperature measurement experiment.It is concluded that the uniform temperature of four types of fluid inclusions in the oxide stage is concentrated between 268℃-337℃,salinity w(NaCleq)=5.26%-8.28%,pH=5.68-5.73.The uniform temperature in the sulfide stage is concentrated between 173℃-205℃,salinity w(NaCleq)=1.29%-4.85%,pH=5.63-5.70,the two-stage mineralization fluid has the characteristics of medium to high temperature,medium to low salinity and weak acidity.The metallogenic pressure is(411.46-919.49)×10^(5) Pa,which is equivalent to a depth of 1.52-3.41 km,suggesting that the mineralization depth of the deposit is shallow,and the mineralization is carried out in a gradually depressurized environment.Based on the above and skarn mineral composition characteristics,it is concluded that the mineralization fluid of the deposit is mainly derived from magmatic hydrothermal fluid,and water-rock reaction occurs with the surrounding rock during the upward movement,which has the genesis characteristics of the proximal skarn-type deposit.