内蒙古白乃庙群基底角闪质岩石的研究

Lithological Study of the Amphibole Rocks from the Basement of the BainaimiaoGroup Inner Mongolia

内蒙古温都尔庙群—白乃庙群构成我国大陆早古生代海沟—岛孤体系而引起国内,外学者的瞩目,但是,长期以来,不同学者对出露在温都尔庙群南部和白乃庙群东北部的一套以角闪质岩石为主的岩石组合的特征及其在板块构造中的含义有不同的认识,争议较大.作者通过室内、外工作认为,两地角闪质岩石属同一岩带,是时代早于温都尔庙群蛇绿岩的焊接在大陆边缘的大洋拉斑玄武岩岩块.它组成了白乃庙群岛弧火山—沉积岩系基底.角闪石质岩石经混合岩化作用。形成不同类型的混合质岩石,混合岩化作用条件为PH_2O=3000～5000Pa,t=700～800℃,含水8%。

The Wenduermiao and Bainaimiao areas,Inner Mongolia,constitute one of the early Paleozoic trenchisland-arc systems in Chinese continent. It attracts much attention of the learners at home and abroad.For long time,there exist some different vicars on the features of the amphibole rocks,occuring in the south of Wenduermiao and the northeast of Bainai- miao,and on its significance in plate tectonics.According to plenty of field work and indoor work,the author thinks that the amphibole rocks from the two areas are in fact the ocean tholeiite masses edged the continental margin and belong to the same rock-belt.They constitute the basement of the island-arc volcanic-sedimetary rocks of Bainaimiao Group,and their age isolder than the ophiolite's in the Wenduermiao Group. The amphibolites have subjected to migmatiration,forming different kinds of migmatites.The migmatiration condition is as following:PH_2O; 3000-5000b,T:700-800℃,water content:8%.