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标题：High-temperature granulites and supercontinents
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作者：J.L.R. Touret ; J.L.R. Touret ; M. Santosh 等
期刊名称：Geoscience Frontiers
印刷版ISSN：1674-9871
出版年度：2016
卷号：7
期号：1
页码：101-113
DOI：10.1016/j.gsf.2015.09.001
语种：English
出版社：Elsevier
摘要：Abstract 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 sub-continental lithospheric mantle, leads to the disruption of supercontinents. Thus, the fragmentation of a supercontinent is already programmed at the time of its amalgamation. Graphical abstract Display Omitted Highlights • The lower crust acts as a temporarily storage for mantle-derived brines and CO2. • Mantle heating and accumulation of fluids in the lower crust cause supercontinent breakup. • Lower crustal fluids may reach the surface after supercontinent disruption.
关键词：Continents; Supercontinents; Magmatism and metamorphism; Fluids; Tectonics;