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喜马拉雅造山带中段的吉隆和聂拉木地区出露一套眼球状片麻岩,其矿物组成为石英、钾长石、斜长石、黑云母和少量的白云母。片麻岩中锆石发育典型的岩浆韵律环带,LA-ICP-MS锆石U-Pb测年显示,2件样品中岩浆锆石的加权平均年龄分别为(488.5±1.1)Ma,(475.1±0.7)Ma和(468.1±2.5)Ma,代表研究区早古生代早期的岩浆作用。现有的早古生代地质记录表明,喜马拉雅地体存在早古生代造山事件,这一事件可与青藏高原南部和东南部的拉萨、羌塘、保山和腾冲地体内同一时代的构造热事件对比,指示区域早古生代造山作用。早古生代早期的造山作用是冈瓦纳大陆聚合之后,原特提斯洋岩石圈沿冈瓦纳大陆北缘俯冲调整的安第斯型造山作用的产物,而非超大陆内部块体拼合过程中陆—陆碰撞为主要特征的泛非造山作用。
In the middle section of the Himalayan orogenic belt, a group of eye-shaped gneiss are exposed in Geelong and Nyalam regions. Its mineral composition is quartz, potash feldspar, plagioclase, biotite and a small amount of muscovite. Zircon U-Pb zircon dating by LA-ICP-MS shows the typical magmatic rhythm zone of gneiss in gneiss. The weighted average ages of magmatic zircon in the two samples are (488.5 ± 1.1) Ma, (475.1 ± 0.7 Ma and (468.1 ± 2.5) Ma, representing the early Paleozoic magmatism in the study area. The existing Early Paleozoic geological records show that there are Early Paleozoic orogeny events in the Himalayan terrain. This event can be compared with the tectonic thermal events of the same era in Lhasa, Qiangtang, Baoshan and Tengchong areas in the southern and southeastern Tibet Plateau, Early Paleozoic orogeny. The early orogenic Paleozoic orogeny was the result of Andean orogenic adjustment of the original Tethyan lithosphere subducted along the northern margin of the Gondwanaland following the convergence of the Gondwanaland but not the land- Continental collision as the main feature of the Pan-African orogenic.