川滇地区岩石圈温度、化学组分结构研究及对岩石圈减薄过程的认识  

Thermal and compositional lithospheric structure of the Sichuan-Yunnan region and its implication to lithospheric thinning

作　　者：周万里 单斌 熊熊 肖阳 ZHOU WanLi;SHAN Bin;XIONG Xiong;XIAO Yang(Hubei Subsurface Multi-Scale Imaging Key Laboratory,Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学(武汉)地球物理与空间信息学院,地球内部多尺度成像湖北省重点实验室,武汉430074

出　　处：《地球物理学报》2023年第12期4987-5004,共18页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42230309,41674106);国家重点研发计划项目(2022YFF0800703);地质过程与矿产资源国家重点实验室科技部专项经费(MSFGPMR2022-6)联合资助。

摘　　要：川滇地区地处中国大陆西南,对其岩石圈结构的研究是认识该地区构造演化过程的基础.由于不同研究方法存在各自的局限性,导致其所获得的岩石圈结构和可能的构造演化过程仍存在争议.岩石圈温度、化学组分结构是深入认识这些争议性问题的基础.本文基于热动力学模拟和概率密度反演的方法,联合瑞雷面波相速度频散曲线、大地水准面高、地形和地表热流等观测资料,反演了川滇地区岩石圈的温度、化学组分结构.结果表明,川滇地区岩石圈呈现南薄北厚的趋势,其中印支块体岩石圈较薄,为60~80 km,相对起伏较小;川滇菱形块体、江南造山带西缘岩石圈自南(~80 km)向北(~200 km)递增;松潘甘孜块体保持较厚的岩石圈根(~240 km).印支块体与江南造山带西缘岩石圈地幔以过渡型和难熔型的橄榄岩为主,仍存在部分古老难熔的岩石圈地幔物质;而川滇菱形块体内部为饱满型岩石圈地幔,表明古老、难熔的岩石圈地幔被新的地幔物质所取代.根据现今川滇地区岩石圈温度、化学组分结构,我们推测川滇地区南部的印支块体受印度板块与亚欧板块南北向碰撞的影响,导致该区域岩石圈增厚,并发生以拆沉作用为主的减薄过程,但岩石圈地幔仍以古老难熔的地幔物质为主;拆沉作用所导致的热地幔物质上涌使得川滇菱形块体古老难熔的岩石圈地幔物质由南往北逐渐为新的地幔物质所取代,形成了现今饱满型岩石圈地幔,热侵蚀作用在川滇菱形块体岩石圈减薄过程中占主导地位.The Sichuan-Yunnan region is situated in the southwestern part of the Chinese mainland.The investigation of its lithospheric structure is essential for comprehending the tectonic evolution of the area.However,different research schemes have different focuses and limitations,which lead to disputes on the lithospheric structure and tectonic evolution process in the Sichuan-Yunnan region.Lithospheric thermal and compositional structure are key to the settlement of these disputes.Based on thermodynamic simulation and probability density inversion,we studied the lithospheric thermal and compositional structure in the Sichuan-Yunnan region using the observed Rayleigh wave phase velocity dispersion curve,geoid height,topography and surface heat flow.The results show that the lithosphere in the Sichuan-Yunnan region is thinner in the south and thicker in the north.The thinner lithosphere of the IndoChina block is 60~80 km thick,with relatively small fluctuations;the lithosphere thickness in the Sichuan-Yunnan diamond block and the western edge of the Jiangnan orogenic belt increases from south(~80 km)to north(~200 km);the Songpan Garzeblock maintains thicker lithospheric roots(~240 km).The lithospheric mantle of the IndoChina block and the western margin of the Jiangnan orogenic belt is mainly composed of transitional and refractory olivine,indicating the existence of some ancient refractory lithospheric mantle material.The lithospheric mantle of the Sichuan-Yunnan diamond block is mainly composed of fertile peridotite,indicating that the ancient refractory mantle lithospheric material has been replaced by new material.Through the study of the lithospheric thermal and compositional structure in the Sichuan-Yunnan region,this paper proposes that the southern Sichuan-Yunnan region is affected by the collision of the Indian plate and the Eurasian plate,resulting in the thickening and delamination of the lithosphere in this region,with ancient refractory lithospheric mantle materials still present.In the Sichuan-Yunnan diamo

关 键 词：川滇地区 岩石圈温度结构 岩石圈化学组分结构 岩石圈减薄机制 

分 类 号：P315[天文地球—地震学] P313[天文地球—固体地球物理学]