念青唐古拉弧背断隆东段始新世花岗岩类成矿意义

Metallogenic Significance of Eocene Granites from the East Sag-uplift of Nyainqenanglha Arc-back

通过对念青唐古拉弧背断隆东段始新世花岗岩类进行岩石学特征研究及全岩地球化学分析,结果表明该套花岗岩类稀土配分模式呈以Eu为界左陡右缓的右倾式特征;花岗岩类形成于碰撞晚期短暂应力松弛、伸展的构造环境,由俯冲消减过程中幔源物质和壳源物质的同熔作用及增厚地壳的硅铝质部分熔融形成,此外俯冲板片上部的深海沉积物也参与了岩浆的形成;围岩是中酸性火山碎屑岩和含粉砂板岩、砂岩、灰岩,大小构造发育,有利于形成与斑岩有关的浅成低温热液矿床、斑岩型矿床及矽卡岩型矿床。

The petrological characteristics of Eocene Granites from the East Sag-uplift of Nyainqenanglha Arc-back study and the whole-rock geochemical analysis on Granitoid rocks showed that the REE patterns of granite presents right decline with Eu as a boundary of left-steep and right-slow style.Granitoid was formed in late stage of collision under tectonic environment of short stress relaxation and stretching.It is generated by the syntexis of the mantle and crustal material during subduction process,and the partial melting of the thickened crust salic.Besides,the deep-sea sediments in upper part of subducted slab also participated in the formation of the magma.Wall rocks consist of the acidic-intermediate volcanic rocks and silty slate stones,sandstone,and limestone.Its structure and growth are in favor of forming the epithermal deposit related porphyry deposit,porphyry-type deposits and skarn deposits.