地球物理剖面揭示大兴安岭域壳幔结构及其地质意义

大兴安岭域，包括大兴安岭及其两侧盆地，穿过额尔古纳地块、兴安地块、松嫩地块和辽源地体.本文在东北地区已有的近东西向的全球地学断面（GGT）资料基础上，在大兴安岭两侧补充了2条近南北向的地球物理剖面，组构了综合地球物理栅状图；又结合区域内其他7条经综合解译的地球物理剖面，分析讨论了研究区壳幔结构特征及其地质意义.论文得到如下初步结果：（1）研究区莫霍界面以大兴安岭重力梯级带为分界，西部和东部深度有明显差异；以索伦山-西拉木伦河缝合带为界的南北岩石圈-软流圈界面（LAB）深度、软流圈有明显差异.呈现出地壳东西分带、岩石圈地幔南北分块的特征.（2）额尔古纳-兴安微板块具有较稳定的岩石圈地幔组构，与南部的中朝板块的岩石圈地幔具有较大差别；额尔古纳地块与西伯利亚板块的岩石圈特征更为接近.（3）获得古缝合带位置线索.林西以南的翁牛特下方存在明显的LAB南北向抬升，这是古亚洲洋闭合在岩石圈尺度上留下的遗迹；索伦山缝合带东延至西拉木伦河，是古亚洲洋闭合的场所.（4）大兴安岭域跨过两条板块缝合带，该区域北部与中部岩石圈组构特征相近，但它们的岩石圈地幔基底并不相同，这是在塔源-喜桂图缝合带于早古生代的拼合之后由数亿年的长期壳幔物质横向均衡作用所致.

Crustal and upper mantle structure beneath the Da Hinggan Mountains region interpreted from geophysical profiles and its geological implications

The Da Hinggan Mountains region includes the range itself and basins on its both sides, where three main microcontinents amalgamated named the Ergun block, Xing'an block, Songnen block, and Liaoyuan terrane. Based on three existing nearly EW-trending Global Geoscience Transects (GGT) and two NS geophysical profiles we acquired in the study region, a 2.5D geophysical fence diagram is established. Then combined with other seven reinterpreted geophysical profiles, the crust and upper mantle structure beneath this region is revealed and its geological implications are discussed. The results show that:(1) The depth of the Moho interface differs on the east and west sides of the Da Hinggan Mountains gravitational gradient belt. Similarly, the Lithosphere-Asthenosphere Boundary (LAB) depth and the features of asthenosphere differ in the north and the south of the Solonker-Xar Moron suture; (2) The Ergun-Xing'an block has a relatively stable lithospheric mantle structure, which is quite different from that of North China Craton, while similar to Siberian Craton; (3) There is a clear north-south striking uplift of LAB beneath Wengniute, south of Linxi, which marks the closure of the Paleo-Asian Ocean on the lithosphere scale. The Solonker suture zone extends eastward to the Xar Moron River where the Paleo-Asian ocean finally closed; (4) Two major plate sutures span across the Da Hinggan Mountains region, and the lithospheric structure is similar in its northern and central areas. But their lithospheric mantle basements are not the same, which was caused by a lateral isostasy of crust-mantle material for hundreds of millions of years after Tayuan-Xiguitu suturing in early Paleozoic.