滇西三江构造带西部腾冲地块内印支期岩浆热事件的发现及其地质意义
Indosinian epoch magmatic event and geological significance in the Tengchong block, western Yunnan Province
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摘要: 西南"三江"(怒江,澜沧江,金沙江)构造带中的澜沧江-昌宁-孟连带及其以东的区域被认为是典型的古特提斯构造域,而构造带西部的腾冲地块则更多的被认为处于雅鲁藏布-密支那/怒江新特提斯的影响之下,在晚古生代-早中生代的时段内一直被认为属于稳定的台地型陆表海环境。然而,本文的研究确证腾冲地块内存在印支期(219~206Ma)的中酸性岩浆岩,表明腾冲地区晚古生代-早中生代时期并不是简单的被动大陆边缘,其内部存在丰富的海西-印支期的岩浆活动的记录。这些岩浆事件与属于同一大地构造单元的拉萨地体腹地和藏东波密地区的同时代岩浆热事件可以对比,说明拉萨地体内新发现的以松多榴辉岩带为代表的印支期造山带的影响范围已向南延伸并直达滇西的腾冲地区。Abstract: Sanjiang Orogenic Belt is located geographically in the area of Nujiang, Lancangjiang and Jinshajiang, SW China. The region east to the Lancangjiang-Changning-Menglian suture is a typical Paleo-Tethyan tectonic domain. But the western Tengchong block is generally thought as Yarlung-Tsangpo-Myitkyina＼Nujiang Neo-Tethys tectonic domain and to be of the stable epi-continental sea setting in Neopaleozoic-Early Mesozoic epoch. However, discovery of Indosinian magmatites(219~206Ma)indicates that the Tengchong block is in fact not of stable passive continental margin in Neopaleozoic-Early Mesozoic epoch, but with many magmatic activities occurred then. Combined with granites of the same ages in the Lhasa and Bomi region, all these magmatites should occurred in a similar tectonic setting, which shows that the newly discovered Indosinian orogenic belt (represented by Sumdo eclogite belt) has extended to the Tengchong area.
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