冈底斯东段驱龙-甲玛矿集区新近纪花岗岩类区域岩石学及成矿学意义

Regional Petrology of Neogene Granitoids in the Qulong-Jiama Ore-concentrated Area of the East Gangdese Belt,Tibet and its Metallogenic Significance

对埃达克岩及其与成矿的关系的研究是近几年花岗岩地质研究的重要进展之一。本文通过对驱龙-甲玛矿集区新近纪花岗岩地质和元素、同位素地球化学综合分析,探讨了新近纪花岗岩类的成因及形成的动力机制、成矿意义。结果表明,新近纪花岗岩具有埃达克岩的地球化学特征,其岩浆起源于下地壳,在上升或演化过程中与幔源岩浆发生了混合,该混合作用对成矿具有重要意义。23～10Ma岩石圈伸展导致软流圈上涌并诱发含石榴石镁铁质岩石拆沉,拆沉下地壳部分熔融形成埃达克岩浆。岩浆混合、岩浆流体出溶的地质、矿物学证据以及有利的大地构造背景、深部物质组成、蚀变特征表明驱龙-甲玛矿集区新近纪"似埃达克岩"具非常重要的成矿学意义。

The study of adakites and their roles in mineralization is one of the most important progresses in recent years.On the basis of their geological,chemical and isotope characteristics,this paper studies the genesis and evolution of Neogene granitoids in the Qulong-Jiama ore-concentrated area,and investigates the mechanisms of granitoids and adakites to probe their metallogenic significance.The results show that Neogene granitoids exhibit obvious calc-alkali to adakite evolutional current and adakite feature;diagenetic and ore-forming materials inheriting the features of the island-arc granite;granitoids derive from the lower crust,then mix with EMⅡduring evolution;lithosphere extension which initiated in 23-10Ma caused upwelling of asthenosphere and delamination of garnet-bearing mafic rocks,partial melting of the delaminated lower crust produced adakites.Considerable geological and mineral evidences of magma mixing and fluid exsolved,favorable geotectonic setting and alteration characteristics demonstrate that Neogene ＂ adakite-like ＂ granitoids in the Qulong-Jiama ore-concentrated area have a great metallogenic significance.