福建省紫金山矿田五子骑龙铜矿床流体包裹体研究

Fluid inclusion study of the Wuziqilong Cu deposit in the Zijinshan ore field,Fujian Province

五子骑龙浆控高温热液型铜矿床位于紫金山矿田北东侧,产于紫金山复式花岗岩内,含矿岩体为燕山早期黑云母二长花岗岩。矿石构造类型主要有脉状和网脉状、浸染状。根据矿物组合与脉体穿插关系,将脉体分为4个阶段。阶段1为绢云母化-迪开石化-硅化蚀变带的石英±钾长石脉;阶段2为被明矾石化-硅化叠加的绢云母化-迪开石-硅化蚀变带的石英-斑铜矿-黄铜矿-蓝辉铜矿-黄铁矿脉±铜蓝;阶段3为石英-铜蓝-黄铁矿脉体;阶段4为明矾石化-硅化蚀变带中的石英±石膏±方解石脉。阶段1发育WV类、C类和少量WL包裹体,阶段2发育WV类、C类和WL类包裹体,阶段3发育WL类和少量WV类包裹体,阶段4只发育WL类包裹体。含子矿物多相包裹体(S型)仅见于隐爆角砾岩体中花岗闪长斑岩的石英斑晶中。阶段1均一温度集中在362～570℃之间,盐度为4%～19.92%NaCleqv,流体体系为NaCl-CO2-H2O体系。阶段2均一温度集中在306～390℃,盐度为0.35%～13.94%NaCleqv,流体沸腾现象显著,CO2等挥发份逸失。阶段3均一温度集中在233～308℃,盐度为0.18%～14.67%NaCleqv。阶段4均一温度降至132～230℃,盐度降至0.88%～6.16%NaCleqv。总体而言,流体从初始的高温NaCl-CO2-H2O体系演化为最终的低温NaCl-H2O体系,期间发生了流体沸腾作用、CO2等挥发份逸失、金属硫化物沉淀、大气降水混入等。

The Wuziqilong intrusion-related hypothermal Cu deposit locates in the northeast of the Zijinshan ore field.It is hosted by Zijinshan complex consisting of mainly Yanshanian biotite monzogranites.Disseminations,veinlets and stockworks are the main ore structures.Four stage veins can be distinguished from their mineralogical paragenesis and crosscutting relationships.The first stage is quartz±feldspar vein system preserved in the sericite-dickite-quartz zone.The second and third are quartz-bornite-chalcopyrite-digenite-pyrite±covellite and quartz-covellite-pyrite polymetallic sulfide stockworks,respectively,observed in sericitization-dickitization-silicification zone which is overprinted by alunitization-silicification.The stage 4 quartz±gypsum±calcite veinlets occur in alunitization-silificication zone.Stage 1 minerals contain CO2-rich and aqueous fluid inclusions with variable vapor/liquid ratios,which are homogenized at 362~570℃,with salinity of 4%~19.92% NaCleqv.In addition to the fluid inclusions observed in stage 1 crystals,daughter mineral-bearing fluid inclusions can be also observed in stage 2 minerals.These fluid inclusions are homogenized at 306~390℃,with salinity of 0.35%~13.94% NaCleqv（daughter minerals are not included in estimation）.Stage 3 minerals have both vapor-rich and liquid-rich two-phase aqueous fluid inclusions that yield homogenization temperature of 233~308℃ and salinity of 0.18%~14.67% NaCleqv.Stage 4 minerals only contain liquid-rich aqueous fluid inclusions homogenized at 132~230℃,with salinity of 0.88%~6.16% NaCleqv.Hence it can be drawn out that the fluids forming the Wuziqilong deposit evolved from initially-magmatic hypothermal NaCl-CO2-H2O system to finally-meteoric epithermal NaCl-H2O system,and that during the evolution fluid boiling occurred,volatiles such as CO2 escaped and metallic sulfides precipitated,followed by input of circulating meteoric water.