High-temperature granulites and supercontinents  

作　　者：J.L.R.Touret M.Santosh J.M.Huizenga 

机构地区：[1]Institut de Mineralogie,Physique des Materiaux,Cosmochimie(IMPMC),Sorbonne Universites et UPMC Univ Paris 06,UMR CNRS 7590,Museum National d'Histoire Naturelle,IRD UMR 206,4 Place Jussieu,F-FS005 Paris,France [2]School of the Earth Sciences and Resources,China University of Geosciences(Beijing),29 Xueyuan Road,Beijing 100083,China [3]Economic Geology Research Institute(EGRU),College of Science,Technology and Engineering,James Cook University,Townsville,Queensland,4811,Australia [4]Unit for Environmental Sciences and Management,North-West University,Private Bag X6001,2520,South Africa

出　　处：《Geoscience Frontiers》2016年第1期101-113,共13页地学前缘（英文版）

基　　金：funding received by James Cook University

摘　　要：The formation of continents involves a combination of magmatic and metamorphic processes. These processes become indistinguishable at the crust-mantle interface, where the pressure-temperature（P-T）conditions of（ultra） high-temperature granulites and magmatic rocks are similar. Continents grow laterally, by magmatic activity above oceanic subduction zones（high-pressure metamorphic setting）, and vertically by accumulation of mantle-derived magmas at the base of the crust（high-temperature metamorphic setting）. Both events are separated from each other in time; the vertical accretion postdating lateral growth by several tens of millions of years. Fluid inclusion data indicate that during the high-temperature metamorphic episode the granulite lower crust is invaded by large amounts of low H2O-activity fluids including high-density CO2 and concentrated saline solutions（brines）. These fluids are expelled from the lower crust to higher crustal levels at the end of the high-grade metamorphic event. The final amalgamation of supercontinents corresponds to episodes of ultra-high temperature metamorphism involving large-scale accumulation of these low-water activity fluids in the lower crust.This accumulation causes tectonic instability, which together with the heat input from the subcontinental lithospheric mantle, leads to the disruption of supercontinents. Thus, the fragmentation of a supercontinent is already programmed at the time of its amalgamation.The formation of continents involves a combination of magmatic and metamorphic processes. These processes become indistinguishable at the crust-mantle interface, where the pressure-temperature（P-T）conditions of（ultra） high-temperature granulites and magmatic rocks are similar. Continents grow laterally, by magmatic activity above oceanic subduction zones（high-pressure metamorphic setting）, and vertically by accumulation of mantle-derived magmas at the base of the crust（high-temperature metamorphic setting）. Both events are separated from each other in time; the vertical accretion postdating lateral growth by several tens of millions of years. Fluid inclusion data indicate that during the high-temperature metamorphic episode the granulite lower crust is invaded by large amounts of low H2O-activity fluids including high-density CO2 and concentrated saline solutions（brines）. These fluids are expelled from the lower crust to higher crustal levels at the end of the high-grade metamorphic event. The final amalgamation of supercontinents corresponds to episodes of ultra-high temperature metamorphism involving large-scale accumulation of these low-water activity fluids in the lower crust.This accumulation causes tectonic instability, which together with the heat input from the subcontinental lithospheric mantle, leads to the disruption of supercontinents. Thus, the fragmentation of a supercontinent is already programmed at the time of its amalgamation.

关 键 词：CONTINENTS SUPERCONTINENTS Magmatism and metamorphism Fluids TECTONICS 

分 类 号：P588.3[天文地球—岩石学] P541[天文地球—地质学]