黔东南金矿形成时代的确定兼论湘黔加里东金矿带

黔东南金矿是赋存在新元古代浅变质岩系中的石英脉型金矿,变质岩的原岩是一套火山-沉积岩,由凝灰岩、凝灰质砂岩、粉砂岩等组成,多具清楚的条纹韵律结构,反映了一种浊流沉积的环境。石英脉的产出受背斜构造和剪切断裂控制,有整合层间脉与断裂破碎带充填脉两种类型。石英脉的组成比较简单,除石英外,主要是硫化物类矿物及捕获的围岩成分。通过对5个矿点的石英中包裹体的Rb-Sr同位素测定和等时线法定年,确定其成矿时代为加里东期,与比邻的湘西同类型金矿的形成时代一致。根据赋矿地层岩性、地质演化历史与构造环境的比较,圈划出了一个湘黔加里东金矿带,对今后的找矿工作会有参考价值。

Determination of the age of gold deposits in southeastern Guizhou: with a discussion of the Caledonian Hunan-Guizhou gold ore belt

Gold deposits in southeastern Guizhou are quartz vein type gold deposits hosted in the Neoproterozoic low-grade metamorphic series. The protoliths of the metamorphic rocks are represented by a volcanic-sedimentary sequence composed of tuff, tuffaceous sandstone and siltstone with a distinct rhythmic ribbon texture, reflecting an environment of turbidite sedimentation. The occurrence of quartz veins is controlled by anticlines and shear faults. Two types of vein may be distinguished: conformable interlayer veins and filling veins in fracture zones. The mineral composition of quartz veins is rather simple, and in addition to quartz, the veins mainly contain sulfide minerals and some minerals captured from wall rocks. Rb-Sr and isochron dating of inclusions in quartz from five gold deposits indicates that their age is Caledonian, which is consistent with the age of gold deposits of the same types of gold deposit in western Hunan adjacent to Guizhou. A Caledonian Hunan-Guizhou gold belt of gold has been delineated according to the lithology of host strata, geological evolution and structural environment, which will be of great reference value for mineral prospecting.