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对西昆仑塔什库尔干县城以东出露的矽线石榴黑云片麻岩和石榴角闪片麻岩进行了阴极发光图像、微区原位LA-ICP-MS微量元素分析和U-Pb定年.结果表明,这两种岩石的变质时代为(220±2)和(220±3)Ma,其原岩沉积或形成年龄分别不早于(253±2)和(480±8)Ma.由于这两种岩石与区内已发现的高压基性麻粒岩和泥质高压麻粒岩产于同一位置或其附近,并且,矽线石榴黑云片麻岩的早期矿物组合(石榴子石+矽线石+条纹长石+石英)与泥质高压麻粒岩早期麻粒岩-高角闪岩相退变质矿物组合一致,石榴角闪片麻岩的矿物组合(石榴子石+角闪石+斜长石+石英)与高压基性麻粒岩角闪岩相退变质矿物组合相吻合,因此其定年结果可有效地用来限定这些高压麻粒岩的峰期变质时代应介于(220±2)~(253±2)Ma之间,进而表明古特提斯洋在本区消减、俯冲碰撞形成康西瓦构造带的时代应为印支期.同时,依据新获得的这两种岩石原岩形成年龄分别不早于(253±2)和(480±8)Ma以及前人已发表的锆石U-Pb年代学数据,提出分布在塔什库尔干县城以东地区的矽线石榴片岩-石英岩岩石组合单元应从原划的古元古代“布伦阔勒岩群”中划分出来.
The cathodoluminescence images, LA-ICP-MS trace element analysis and U-Pb dating of silanite gneiss and garnet hornblende gneiss exposed to the east of Taxkorgan County in western Kunlun area were carried out. Results The results show that the metamorphic times of these two rocks are (220 ± 2) and (220 ± 3) Ma, and their original rock formation or formation ages are not earlier than (253 ± 2) and (480 ± 8) Ma, respectively. The petrologic rocks are located at or near the high-pressure basic granulites and argillaceous high-pressure granulites that have been found in the area, and the early mineral assemblages (garnet + silanite Rock + striped feldspar + quartz) is consistent with the metamorphic mineral assemblage of the early granulite-amphibolite facies in the argillaceous high-pressure granulite. The mineral assemblages of garnet hornblende gneiss (garnet + amphibole + The results show that the dating of these rocks can be effectively used to define the peak metamorphic age of these high-pressure granulites should be between (220 ± 2) ~ (253 ± 2) Ma, which indicates that the ancient Tethys Ocean subducted in this area and that the Indosinian period should be formed during the subduction collision to form the Kangxiwa tectonic belt. At the same time, The newly acquired protoliths of these two types of rocks are formed not earlier than (253 ± 2) and (480 ± 8) Ma and previously published zircon U-Pb chronological data, and are proposed to be distributed in areas east of Taxkorgan County The silanite-quartzite assemblage should be separated from the original Paleoproterozoic Burenculal Group.