The studies of continental deep subduction and ultrahigh-pressure metamorphism have not only promoted the development of solid earth science in China, but also provided an excellent opportunity to advance the plate te...The studies of continental deep subduction and ultrahigh-pressure metamorphism have not only promoted the development of solid earth science in China, but also provided an excellent opportunity to advance the plate tectonics theory. In view of the nature of subducted crust, two types of subduction and collision have been respectively recognized in nature. On one hand, the crustal subduction occurs due to underflow of either oceanic crust (Pacific type) or continental crust (Alpine type). On the other hand, the continental collision proceeds by arc-continent collision (Himalaya-Tibet type) or continent-continent collision (Dabie-Sulu type). The key issues in the future study of continental dynamics are the chemical changes and differential exhumation in continental deep subduction zones, and the temporal-spatial transition from oceanic subduction to continental subduction.展开更多
A trondhjemitic body occurs in the Aoyougou area,the western part of the North Qilian orogen.It is geochemically characterized by high SiO 2,Na 2 O (high Na/K),elevated Sr/Y and (La/Yb) N,positive Sr anomaly,relativel...A trondhjemitic body occurs in the Aoyougou area,the western part of the North Qilian orogen.It is geochemically characterized by high SiO 2,Na 2 O (high Na/K),elevated Sr/Y and (La/Yb) N,positive Sr anomaly,relatively enriched large ion lithophile elements (LILEs) and light rare earth elements (LREEs),and depleted Nb,Ta,Ti,resembling the high-silica adakite.Zircon U-Pb SHRIMP dating yields a weighted mean age of 438±3 Ma.This age is significantly younger than eclogitization ages of 460-490 Ma in the North Qilian orogen,suggesting that formation of the adakite postdates the subduction of oceanic crust in association with closure of the ancient Qilian Ocean.Whole-rock Sr and Nd isotopic analyses give initial ratios of I Sr =0.7044 0.7047 and Nd (t)=3.0 4.1,indicating that they are derived from partial melting of the juvenile oceanic crust.In view of the tectonic evolution of the North Qilian orogen,the high-silica adakite was probably derived from decompression melting of the exhumed eclogite at the depth of ～60 km.展开更多
地球是太阳系中最独特的行星,以演化出具有大洋和大陆双地壳组成为基本特征.其中大洋地壳分布在低洼地区,具有薄层且均一的玄武质成分;而大陆地壳则普遍分布在相对高海拔地区,厚度大、成分变化大且总体具有安山质成分(Rudnick and Gao,2...地球是太阳系中最独特的行星,以演化出具有大洋和大陆双地壳组成为基本特征.其中大洋地壳分布在低洼地区,具有薄层且均一的玄武质成分;而大陆地壳则普遍分布在相对高海拔地区,厚度大、成分变化大且总体具有安山质成分(Rudnick and Gao,2014).大洋地壳由于密度高导致其重力失稳发生俯冲,因此现有大洋中的洋壳均较年轻(≤200 Ma);大陆地壳占地球表面积约40%,但是占地壳总体积的70%(Taylor and McLennan,1985).由于其密度较小,可以不同程度地保存下来,因此记录了地球不同历史时期的形成演化历史.目前已知最古老的大陆地壳为约40亿年的Acasta片麻岩(Bowring and Williams,1999),最古老的地壳物质为澳大利亚Jack Hill变沉积岩中约44亿年的碎屑锆石(Harrison,2009).如何确定大陆地壳生长和演化过程是地球科学领域根本性的科学问题.展开更多
基金Supported by the Chinese Academy of Sciences (Grant No. kzcx2-yw-131)Ministry of Science and Technology of China (Grant No. 2009CB825000)
文摘The studies of continental deep subduction and ultrahigh-pressure metamorphism have not only promoted the development of solid earth science in China, but also provided an excellent opportunity to advance the plate tectonics theory. In view of the nature of subducted crust, two types of subduction and collision have been respectively recognized in nature. On one hand, the crustal subduction occurs due to underflow of either oceanic crust (Pacific type) or continental crust (Alpine type). On the other hand, the continental collision proceeds by arc-continent collision (Himalaya-Tibet type) or continent-continent collision (Dabie-Sulu type). The key issues in the future study of continental dynamics are the chemical changes and differential exhumation in continental deep subduction zones, and the temporal-spatial transition from oceanic subduction to continental subduction.
基金supported by the National Basic Research Program of China(2009CB825007)the National Natural Science Foundation of China(40825007and40821002)the Chinese Geological Survey Projects(1212011121258)
文摘A trondhjemitic body occurs in the Aoyougou area,the western part of the North Qilian orogen.It is geochemically characterized by high SiO 2,Na 2 O (high Na/K),elevated Sr/Y and (La/Yb) N,positive Sr anomaly,relatively enriched large ion lithophile elements (LILEs) and light rare earth elements (LREEs),and depleted Nb,Ta,Ti,resembling the high-silica adakite.Zircon U-Pb SHRIMP dating yields a weighted mean age of 438±3 Ma.This age is significantly younger than eclogitization ages of 460-490 Ma in the North Qilian orogen,suggesting that formation of the adakite postdates the subduction of oceanic crust in association with closure of the ancient Qilian Ocean.Whole-rock Sr and Nd isotopic analyses give initial ratios of I Sr =0.7044 0.7047 and Nd (t)=3.0 4.1,indicating that they are derived from partial melting of the juvenile oceanic crust.In view of the tectonic evolution of the North Qilian orogen,the high-silica adakite was probably derived from decompression melting of the exhumed eclogite at the depth of ～60 km.
文摘地球是太阳系中最独特的行星,以演化出具有大洋和大陆双地壳组成为基本特征.其中大洋地壳分布在低洼地区,具有薄层且均一的玄武质成分;而大陆地壳则普遍分布在相对高海拔地区,厚度大、成分变化大且总体具有安山质成分(Rudnick and Gao,2014).大洋地壳由于密度高导致其重力失稳发生俯冲,因此现有大洋中的洋壳均较年轻(≤200 Ma);大陆地壳占地球表面积约40%,但是占地壳总体积的70%(Taylor and McLennan,1985).由于其密度较小,可以不同程度地保存下来,因此记录了地球不同历史时期的形成演化历史.目前已知最古老的大陆地壳为约40亿年的Acasta片麻岩(Bowring and Williams,1999),最古老的地壳物质为澳大利亚Jack Hill变沉积岩中约44亿年的碎屑锆石(Harrison,2009).如何确定大陆地壳生长和演化过程是地球科学领域根本性的科学问题.
