内蒙古锡林浩特地区中元古代锡林浩特岩群的厘定及其意义

Redefinition and Significance of Metamorphism Xilinhot Group in Xilinhot Area, Inner Mongolia, China

通过大比例尺填图和剖面研究,将内蒙古锡林浩特地区的"锡林郭勒杂岩"解体分为3大部分:一套表壳岩、晚元古代基性-超基性侵入岩和早古生代酸性侵入岩.在此基础上根据变质岩的岩性组合和变形变质特点,可将其中的表壳岩化分为4个岩性段:黑云(石榴石)斜长片麻岩,间夹多层条纹状斜长角闪岩,在其顶部多见薄层含磁铁石英岩;中粗粒黑云斜长片麻岩和细粒长英质片麻岩;混合岩化条带状黑云(角闪)斜长片麻岩,含石榴石黑云二长片麻岩夹条纹状斜长角闪岩组合;夕线石黑云斜长片麻岩,条纹状黑云斜长片麻岩,间夹含石榴石黑云母石英片岩.通过对比区域内宝音图群、艾勒格庙组、白乃庙群等古老地块的岩石组合,发现在原岩建造、变质级别、沉积环境等特征上均有区别,应将这套表壳岩单独厘定为锡林浩特岩群,它们组成了锡林郭勒微陆块前寒武变质基底岩系,其地质特征的研究对锡林郭勒微陆块基底的形成和演化及华北板块与西伯利亚板块的构造关系演化有重要意义.

Based on large scale geologic mapping and measuring section, the Xilin Gol complex is divided into three parts： su- pracrustal rock, Late Proterozoic basic-ultrabasic rock and Early Paleozoic acid intrusive rocks. According to lithologic associa- tion and characteristics of deformation and metamorphism, biotite （garnet） plagioclase gneiss intercalated with several layers barred amphibolite, with thin layer magnetite quartzite on its top medium-coarse biotite plagioclase gneiss and fine-grained fel- sic gneiss; lithologic association of migmatization banding biotite （hornblende） plagioclase gneiss and garnet monzonitic gneiss intercalated with barred amphibolite; sillimanite biotite plagioclase gneiss, barred biotite plagioclase gneiss, intercalated with garnet bearing biotite quartz schist. Comparison study on the different lithologic association, metamorphic characteristics and depositional environment of Baoyintu Group, Ailegemiao Formatio, Bainaimiao Group and others. This paper proposes to rede- fine these supercrustal rocks named ＂Xilinhot Group＂, which compose the Precambrian metamorphic basement of Xilin Col mi- cro block. It＇s important to study the formation and development of Xilin Col micro block and the evolution of structural rela- tionship between Siberia plate and North China plate.