黑龙江省三矿沟夕卡岩型铁铜矿床矿物学特征及成矿物理化学条件

Mineralogical characteristics and ore-forming physicochemical conditions of the Sankuanggou skarn Fe-Cu deposit,Heilongjiang Province

黑龙江三矿沟铁铜矿床位于大兴安岭北段多宝山矿集区,矿体产于燕山期侵入岩与奥陶系多宝山组大理岩接触带的夕卡岩内。根据矿物共生组合及交代关系,确定热液成矿过程包括夕卡岩阶段、退夕卡岩阶段和石英-硫化物阶段。铁矿化主要发生在退夕卡岩阶段,形成磁铁矿、镜铁矿等铁氧化物,呈浸染状、条带状、块状产于钙铁榴石夕卡岩中。铜矿化主要发生在石英-硫化物阶段,形成黄铜矿、斑铜矿等硫化物,交代早期矿物。电子探针分析等研究表明,三矿沟铁铜矿床发育钙质夕卡岩矿物组合,其石榴子石主要为钙铝榴石和钙铁榴石,辉石为透辉石-钙铁辉石系列,角闪石属于钙角闪石系列,绿泥石属于I型三八面体富铁绿泥石。石榴子石有3种类型:早期自形粗粒的钙铝榴石(Grt-Ia)和钙铁榴石(Grt-Ib),以及晚期呈脉状产出的钙铁榴石(Grt-Ⅱ)。夕卡岩阶段成矿流体具有高温、弱酸性、高氧逸度的特征;退夕卡岩阶段流体温度降低,pH升高,形成大量铁氧化物;石英-硫化物阶段流体温度和氧逸度降低,金属硫化物沉淀。

The Sankuanggou skarn Fe-Cu deposit is located in the Duobaoshan metallogenic belt of the northern Greater Khingan Range,Heilongjiang Province.The ore bodies occur in the garnet skarns of the contact zones between the Yanshanian granodiorite and the Ordovician Duobaoshan Formation marble.As indicated by mineral assemblage and interaction,the hydrothermal ore-forming process included the prograde skarn,retrograde skarn and quartz-sulfide stages.Iron oxides and copper sulfides were mainly formed in the retrograde skarn and quartz-sulfide stages,respectively.Electron microprobe analysis showed that garnets are made of andradite and grossularite;pyroxenes consist of diopside and hedenbergite;amphiboles belong to calciferous amphibole;chlorites are trioctahedral Fe-chlorite;and the mineral assemblage in the Sankuanggou Fe-Cu deposit is a typical calcareous skarn system.Garnets present as early coarse-grained grossularite（Grt-Ia）and andradite（Grt-Ib）,and late fine-grained andradite veins（Grt-Ⅱ）.Skarns formed under high temperature and weak acidic and oxidizing conditions.Retrograde skarnization led to decreased temperature and higher pH resulting in magnetite and specularite deposit,while chalcopyrite and other sulfides precipitated due to decreased oxygen fugacity and temperature following retrograde skarnization.