皖南花山金矿化域蚀变岩体的地质地球化学特征及成因探讨

THE GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS,AND GENESIS OF THE ALTERED GRANITOIDS IN THE HUASHAN GOLD MINERALIZED DOMAIN,SOUTH ANHUI

在皖南花山金矿化域,沿层间断裂及滑脱断层出露大量的中酸性次火山岩,岩体蚀变强烈,岩浆具有快速上升侵位,快速冷却的特点。在岩石地球化学特征上,主元素及其氧化物、大离子半径亲石元素(LILE)含量变化较大,反映了其主矿物的不稳定性,另外风化剥蚀作用也较强,CIA值高达85;然而高场强元素(HFSE)、稀土元素(REE)含量变化较小,反映了其副矿物的相对稳定性及这两类元素的抗蚀变风化作用性,因此代表了蚀变前原岩的特征,岩体是在大陆弧环境下源岩经平衡部分熔融作用形成的同熔型花岗质岩石。

In the Huashan gold mineralized domain, along interlayer faults and decollement faults outcrop a lot of intensely altered medium—acidic subvolcanic rocks,showing that the magma was characterized by rapid upward emplacement and cooling. Geochemically,some host elements and their oxides and LILE vary greatly in content, which shows the instability of their host minerals (i. e,essential minerals). Meanwhile CIA value up to 85 indicates intense weathering and denudation and HFSE,REE with a litte change in content demonstrate the stability of their host minerals (i. e,accessory minerals) and the resistibility of HFSE and REE to weathering,representing the geochemical characteristics of the pre—alteration protolith,syntectic granitoids formed through partial melting of source rocks in a continental arc.