Carbonate metasomatism in the lithospheric mantle: Implications for cratonic destruction in North China  

作　　者：Keqing ZONG Yongsheng LIU 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources [2]School of Earth Sciences,China University of Geosciences,Wuhan

出　　处：《Science China Earth Sciences》2018年第6期711-729,共19页中国科学（地球科学英文版）

基　　金：co-supported by the National Key R&D Program of China(Grant No.2016YFC0600103);the National Natural Science Foundation of China(Grant Nos.41473031,41530211);the National Program on Key Basic Research Project(Grant No.2015CB856101);the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Grant No.MSFGPMR01)

摘　　要：The activity of melts and fluids may have played a key role in inducing the destruction of the eastern North China Craton in the early Cretaceous. Carbonate melts are important agents in mantle metasomatism and can significantly modify the physical and chemical properties of the subcontinental lithospheric mantle. Carbonate metasomatism can be identified by specific geochemical indices in clinopyroxene, such as high Ca/Al and low Ti/Eu ratios. This study presents the spatial and temporal variations of carbonate metasomatism in the lithospheric mantle beneath the eastern North China Craton. Three types of carbonate metasomatism are classified based on the geochemical compositions of clinopyroxene in mantle peridotites. Clinopyroxene formed by Type 1 carbonate metasomatism is characterized by very high Ca/Al ratios(15–70) and^(87)Sr/^(86)Sr ratios(0.706–0.713). Clinopyroxene derived from Type 2 carbonate metasomatism shows relatively high Ca/Al ratios(5–18) and^(87)Sr/^(86)Sr ratios(0.703–0.706). However, clinopyroxene resulting from Type 3 carbonate metasomatism has low Ca/Al ratios(5–9) and^(87)Sr/^(86)Sr ratios(0.702–0.704). Deep(garnet-bearing) and shallow(spinel-bearing) lithospheric mantle beneath the Sulu orogen and surrounding areas in the eastern North China Craton were affected by intense Type 1 carbonate metasomatism before the late Triassic. The deep subduction of the South China Block with its accompanying carbonate sediments was the trigger for Type 1 carbonate metasomatism, which reduced strength of the lithospheric mantle and provided a prerequisite for the destruction of the eastern North China Craton in the early Cretaceous. After the destruction of the eastern North China Craton, the ancient relict lithospheric mantle, represented by spinel harzburgite xenoliths hosted in the late Cretaceous to Cenozoic basalts,only recorded Type 2 carbonate metasomatism. This implies that the lithospheric mantle experienced the intense Type 1 carbonate metasomatism was completely destroyed and not prThe activity of melts and fluids may have played a key role in inducing the destruction of the eastern North China Craton in the early Cretaceous. Carbonate melts are important agents in mantle metasomatism and can significantly modify the physical and chemical properties of the subcontinental lithospheric mantle. Carbonate metasomatism can be identified by specific geochemical indices in clinopyroxene, such as high Ca/Al and low Ti/Eu ratios. This study presents the spatial and temporal variations of carbonate metasomatism in the lithospheric mantle beneath the eastern North China Craton. Three types of carbonate metasomatism are classified based on the geochemical compositions of clinopyroxene in mantle peridotites. Clinopyroxene formed by Type 1 carbonate metasomatism is characterized by very high Ca/Al ratios（15–70） and^（87）Sr/^（86）Sr ratios（0.706–0.713）. Clinopyroxene derived from Type 2 carbonate metasomatism shows relatively high Ca/Al ratios（5–18） and^（87）Sr/^（86）Sr ratios（0.703–0.706）. However, clinopyroxene resulting from Type 3 carbonate metasomatism has low Ca/Al ratios（5–9） and^（87）Sr/^（86）Sr ratios（0.702–0.704）. Deep（garnet-bearing） and shallow（spinel-bearing） lithospheric mantle beneath the Sulu orogen and surrounding areas in the eastern North China Craton were affected by intense Type 1 carbonate metasomatism before the late Triassic. The deep subduction of the South China Block with its accompanying carbonate sediments was the trigger for Type 1 carbonate metasomatism, which reduced strength of the lithospheric mantle and provided a prerequisite for the destruction of the eastern North China Craton in the early Cretaceous. After the destruction of the eastern North China Craton, the ancient relict lithospheric mantle, represented by spinel harzburgite xenoliths hosted in the late Cretaceous to Cenozoic basalts,only recorded Type 2 carbonate metasomatism. This implies that the lithospheric mantle experienced the intense Type 1 ca

关 键 词：Cratonic destruction North China Carbonate metasomatism Ca/Al in clinopyroxene Lithospheric mantle 

分 类 号：P542.5[天文地球—构造地质学]