内蒙古巴彦都兰地区侵入岩地球化学特征及构造岩浆演化

Geochemical Characteristics and Tectonic-magmatic Evolutionof the Intrusive Rocks in Bayanduan Area,Inner Mongolia

巴彦都兰地区侵入岩发育,出露有闪长岩、黑云母花岗岩、钾长花岗岩、正长斑岩、石英正长岩等岩体以及石英脉、细粒花岗岩脉、闪长玢岩脉、辉长岩脉、辉绿(玢)岩脉、煌斑岩脉等脉岩。通过对不同侵入岩样品进行岩石地球化学研究,结合前人已有的锆石U-Pb同位素年龄数据,判断该区不同时代侵入岩产出于不同的大地构造环境。早二叠世侵入岩为在汇聚机制下古洋壳向西伯利亚板块东南缘弧下俯冲,诱发成熟陆缘弧下地壳熔融而形成的最早但规模较小的一次岩浆活动;晚二叠世—早三叠世区域上不仅存在洋—陆碰撞造山,而且也发生过陆—陆碰撞造山过程;中三叠世花岗岩类为两大板块碰撞闭合后,转入伸展体制下岩石圈剥离和热软流圈上涌陆壳熔融形成的;晚侏罗纪,在大规模伸展体制下,幔源底侵,地壳部分熔融,幔源分异形成的基性岩浆、陆壳物质部分熔融形成的酸性岩浆以及二者混合形成的中性岩浆沿深大断裂不同层次上侵,形成了系列基性—酸性深成—超浅成岩浆。

The intrusive rocks in Bayandulan area are developed,There are diorite,biotite granite,moyite,orthophyre,quartz-syenite,as well as quartz veins,fine grained granite veins,diorite-porphyrite veins,gabbro veins,diabase-porphyrite veins,lamprophyre veins and so on.By researching in the lithogeochemica characteristics of the samples of different intrusive rocks,combined with the previous zircon U-Pb isotope age data,the authors conclude that the intrusive rocks in different times of this area are produced in different geotectonic environments.The early Permian intrusive rocks are the earliest but smaller magma activities,which formed by the melting of the lower crust of the continental marginal arc that caused by the ancient oceanic crust dived into the arc of the southeast edge of the Siberian plate,under the convergence mechanism.In the late Permian to the early Triassic,there was not only the ocean-land collision orogeny,but also the land-land collision orogenic process.The middle Triassic granite were formed by the fusion of the continental crust with the lithospheric stripping and the hot asthenosphere upwelling in an extensional regime,after the two plates collided and closed.In the late Jurassic,when the mantle source underplating and the crust partial melting under the large-scale extension system,the basic magma that came from differentiation of the mantle source,the acidic magma that came from partial melting of the continental crust and the neutral magma that formed from they mixed invaded along the deep fault at different levels,so formed a series of basic-acid and hypogene-over-hypabyssal magma.