祁连山造山作用与岩石圈地幔的特型结构构造  

Cenozoic orogenesis of the Qilian Mountain and the lithosphere mantle tectonic framework beneath it

作　　者：赵文津[1] Mechie J 冯梅[3] 史大年[4] 薛光琪 宿和平[4] 宋洋[1] 杨宏伟[1] 刘志伟[1] 

机构地区：[1]中国地质科学院,北京100037 [2]德国地球科学研究中心(GFZ) [3]中国地质科学院地质力学研究所,北京100037 [4]中国地质科学院矿产资源研究所,北京100037

出　　处：《中国地质》2014年第5期1411-1423,共13页Geology in China

基　　金：中国地质调查局项目"青藏高原深部结构探测与地壳活动特征"(1212010511809)及"青藏高原深部过程与资源环境效应研究"(1212011220903)资助

摘　　要：本文探讨了祁连山地壳增厚与造山机制。提出新生代以来,由于印度地块向北推进,其延迟的远程效应使祁连地块内4条断裂再次活动,特别是23 Ma以来,分阶段的活动使上地壳缩短了30%,40 km厚的祁连地壳增加到57km厚;并通过柴达木地块下地壳物质的挤入,使祁连地块地壳厚度增加到现今的60～74 km;地壳质量基本平衡表明其下部地壳物质横向迁移较小,即走滑断裂带走的地壳物质较少。依据INDEPTH-V新的宽频地震调查成果,提出祁连地块下岩石圈地幔的复杂结构,南部来的昆仑岩石圈地幔（双层结构）与北部向南俯冲的阿拉善地块下的亚洲岩石圈地幔在祁连地块深部相碰撞,而柴达木—祁连岩石圈地幔则被保存在昆仑岩石圈与亚洲岩石圈地幔碰撞带之上,共形成一倒三角汇聚区;在柴北缘与中祁连北缘岩石圈地幔各出现一条北倾和南倾的正转换震相,可能是老俯冲带残存岩片的显示;在祁连地块岩石圈地幔的两端地壳底部还出现有“双”莫霍“现象”,地表见有多条榴辉岩带。以上结果构成了高原最具特色的构造区。Based on the DSS （Deep Seismic Sounding） and BB （Broad Band Earthquake seismograms） research along the INDEPTH-IV line accomplished in 2013, the authors investigated the crustal thickening and orogenic mechanism of the Qilian Mountain, and revealed 4 faults in the block which was reactivated by the distant effect induced by the Indo- Asia collision since Cenozoic, especially since 23 Ma. The upper crust was shortened by about 30%, and hence Qilian crest 40km in thickness was thickened to 57 km. The lower crust was thickened by the intrusion of the Qaidam lower crest, which caused the variation of the crust thickness of Qilian Block from 57 km to the present 60 - 74 km. According to the P-wave receiver function （PRF） image, the authors obtained the Lithosphere Mantle （LM） Tectonic Framework beneath the Qilian Block, which comprises four parts： the southern part was from the southern Kunlun Block of 60km thickness with a two-layer structure and subducted northward, whereas the northern one was from Alxa Block with a thickness of 50 km and subducted southward. Both of them collided beneath the Qilian Block at the depth of 120 km. The other two parts are the Qaidam and Qilian blocks, with the relic texture of two old sutures. All of the four lithosphere mantle sections constructed a reverse delta structure. On the two old sutures （north fringe of the Qaidam Block and north fringe of the Middle Qilian Sub-Block）, the authors found “two double phase” phenomenon, and also revealed two ecologite belts at the ground surface along the suture zones.

关 键 词：祁连地块 地壳增厚 岩石圈地幔 “双莫霍” 倒三角结构 

分 类 号：P552[天文地球—构造地质学] P542[天文地球—地质学]