Microscopic deformation of the Neoarchean oceanic lithospheric mantle: evidence from the Zunhua Neoarchean ophiolitic melange, North China Craton  

Microscopic deformation of the Neoarchean oceanic lithospheric mantle: evidence from the Zunhua Neoarchean ophiolitic mélange,North China Craton

作　　者：HUANG Xiongnan , LI Jianghai, NIU Xianglong and FENG Jun(The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China) 

出　　处：《Progress in Natural Science:Materials International》2003年第8期607-614,共8页自然科学进展·国际材料（英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos.40242014;49832030) and Peking University (Project 985)

摘　　要：The microstructures of the mantle tectonites in the Zunhua Neoarchean ophiolitic melange are mainly coarse-mosaicstructures with locally interstitial impregnated melts. Olivine and orthopyroxene occur as residual porphyroclastic blasts, dynamic recrys-tallization neobtasts or elongated to be tabular. The podiform chromitites are mostly strongly deformed with the development of pull-apart structure. These microstructures are typical high-temperature plastic deformation in oceanic upper mantle resulting from ocean-floor spreading. Besides the high-temperature plastic deformation, undeformed magmatic intrusions such as undeformed podiform chromitite, dunite and pyroxenite intrusions are also preserved in the mantle tectonite. Structures of high-temperature plastic deformation and intensive magmatic activity prove that the Zunhua ophiolite was formed under fast spreading oceanic ridge, similar to the Oman ophiolite. And the microstructures of country rocks, such as quartz ribbon, core and mantle structure, dynamic recrystallization and mica-fish stucture, etc., were formed during the uplift of ophiolitic melange from the mid-crust to the upper-crust associated with continental collision.The microstructures of the mande tectonites in the Zunhua Neosrchean ophiolitic melange are mainly coarse-mosaic structures with locally interstitial impregnated melts. Olivine and orthopyroxene occur as residual porphyroclastic blasts, dynamic recrys-tallization neoblasts or elongated to be tabular. The podiform chromitites are mostly strcmgly deformed with the devdopmmt of pull-apart structure.These microstructures are typical high-temperature plastic deformation in oceanic upper mande resulting from ocean-floor spreading. Besides the high-temperature plastic deformation, undeformed magmatic intrusions such as undeformed podiform chromitite,dunite and pyroxenite intnmons are also preserved in the mantle tectonite. Structures of high-temperature plastic deformation and intensive magmatic activity prove that the Zunhua ophiolite was formed under fast spreading oceanic ridge, similar to the Oman ophiolite. And the of country rocks, such as quartz ribbon, core and mantle structure, dynamic recrystallization and mica-fish stucture, etc.,were formed during the uplift of ophiolitic melange from the mid-crust to the upper-crust associated with continental collision.

关 键 词：NEOARCHEAN ophiolitic melange microstructures oceanic upper-mantle structural deformation. 

分 类 号：P736[天文地球—海洋地质]