宁芜南段钟姑矿田的深部矿浆-热液系统

钟姑矿田作为宁芜盆地南部重要的矿集区,发育一系列以姑山矿浆熔离型和白象山高温气液型为代表的大型玢岩铁矿,这些铁矿均主要产于闪长玢岩岩体和沉积围岩的接触带。根据野外观察和地球化学研究,文中认为,闪长玢岩岩体和沉积围岩均不是铁质的主要来源,富铁矿体的成因主要来自矿田深部的矿浆-热液系统,姑山式铁矿的铁质主要是液态不混溶作用形成的铁矿浆,白象山式铁矿的铁质主要来源于深部残浆分离出的Na-Fe-Cl络合物。在对铁质和岩体估算的基础上,提出形成铁矿的原始母岩浆很可能是富铁的玄武质岩浆,形成于大规模的岩石圈减薄、软流圈上涌的构造背景下,由变质洋壳(榴辉岩)和软流圈地幔(橄榄岩)反应后的橄榄岩部分熔融形成,其在上升的过程中发生了AFC过程。

Deep ore magma-hydrothermal system of Zhonggu ore field in southern part of Ningwu Basin

The Zhonggu ore field,as an important ore-cluster in the southern part of the Ningwu volcanic basin,hosts series of iron deposits which are represented by Gushan and Baixiangshan and usually occurred at the contact zone between the dioritic porphyry and sedimentary rocks.Our investigation shows that neither the dioritic porphyry nor the sedimentary rock is the source of iron ores,and that the source of most iron-rich orebodies is the ore magma-hydrothermal system in the deep chamber.Ore magma which was formed by liquid immiscibility is the main source of Gushan deposit,and the residual iron-rich hydrothermal fluids which occurred as Na-Fe-Cl complex is the main source of Baixiangshan deposit.According to the quantitative estimation of iron ores and porphyry intrusion,the primary magma is probably the ferrobasalt,which formed in the environment of large-scale thinning of lithosphere and upwelling of the asthenosphere and by the reaction between metamorphic oceanic crust (eclogite) and asthenosphere (peridotite),and AFC process occurred enroute.