孔兹岩系事件与太古宙地壳构造演化

Khondalite event and Archean crust structure evolvement

孔兹岩系是太古宙高级变质岩区中较为常见的变质沉积岩石地层单位 ,它以富铝(含墨 )的矽线榴云片麻岩为特征 ,伴有石英岩、钙硅酸盐岩及富镁大理岩等组合而成的一套岩石地层。内蒙古大青山地区近年来研究工作的重要进展之一 ,是对发育在该区的孔兹岩系进行了系统构造地层学研究 ,提出了由下至上三个岩层单位组成的地层序列 :即榴云片麻岩岩组、含黑榴云片麻岩岩组及大理岩岩组或透辉片麻岩岩组 ,下与兴和岩群的麻粒岩系 ,上与浅变质的古元古代美岱召岩群呈不整合接触。根据侵入孔兹岩系中的单斜辉石斜长角闪岩的Sm Nd同位素年龄 2 80 0Ma(杨振升等 ,另文发表 ) ,确定孔兹岩系时代应属中太古代 ,按区域太古宙地层构造格架 ,在大青山—乌拉山及色尔腾山地区孔兹岩系应位于新太古代色尔腾山群之下。大青山地区所建立的孔兹岩地层层序及其在太古宙地层系统中的位置 ,无疑对相邻地区高级变质区的岩石地层研究有重要借鉴意义。联系到全球太古宙高级变质区中相当于孔兹岩系的组成分布的广泛性与其惊人的相似性 ,作者建议使用孔兹岩系事件一词来表达 350 0～ 2 80 0Ma时期地壳上曾经存在超洲际规模的克拉通大陆 ,这规模巨大的克拉通的富铝 (含黑 )碎屑岩—石英岩—碳酸盐岩 (钙硅酸盐 )的沉积事件 。

Khondalite is a metasediment stratum unit which frequently occurred in Archean high-grade region. The khondalite character with aluminium-rich (graphite) sillimenite garnet-mica gneiss. Its concomitant with quartzite, calcium silicate rocks and magnesium-rich marble, assembled a suit of rock-stratum. A detailed investigation of the khondalite structure and stratum system is one of the signify achievement in Daqingshan of Inner Mongolia in resent years. Three sequence had been put forward from down to up. There are granite-mice gneiss assemblage, biotite-bering granite-mica gneiss assemblage, and marble assemblage and/or calamite gneiss assemblage. They are unconformity with granulite of Xinghe Complex in the bottom, and with slight metamorphosed Meidaizhao Complex of Peleoproterozoic in the top. According to the Sm-Nd isotopic data 2800 Ma of clinoaugite amphibolite, which intruded into khondalite, the age of khondalite should be in Mesoarchean. According to the regional stratotectonic framework of Archean, the khondalite series should be underlaying Neoachean Se'erteng Group in Daqingshan-Wulashan and Se'ertengshan areas. The investigation of the khondalite sequence and its position in the stratum system of Archean in Daqingshan region is very useful to study the high-grade region of adjacent areas. Considered to the universality distribution of the khondalite, and its egregious comparability with the high-grade region of Archean in the world, author suggested that using khondalite event represent the supercontinent craton which had been occurred in 3500-2800 Ma.