Composition and evolution of the continental crust: Retrospect and prospect

Touret, J.L.R., Santosh, M., and Huizenga, J.M. (2022) Composition and evolution of the continental crust: Retrospect and prospect. Geoscience Frontiers, 13 (5). 101428.

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Abstract

Until the middle of the 20th century, the continental crust was considered to be dominantly granitic. This hypothesis was revised after the Second World War when several new studies led to the realization that the continental crust is dominantly made of metamorphic rocks. Magmatic rocks were emplaced at peak metamorphic conditions in domains, which can be defined by geophysical discontinuities. Low to medium-grade metamorphic rocks constitute the upper crust, granitic migmatites and intrusive granites occur in the middle crust, and the lower crust, situated between the Conrad and Moho discontinuities, comprises charnockites and granulites. The continental crust acquired its final structure during metamorphic episodes associated with mantle upwelling, which mostly occurred in supercontinents prior to their disruption, during which the base of the crust experienced ultrahigh temperatures (>1000 C, ultrahigh temperature granulite-facies metamorphism). Heat is provided by underplating of mantle-derived mafic magmas, as well as by a massive influx of low H2O activity mantle fluids, i.e. high-density CO2 and high-salinity brines. These fluids are initially stored in ultrahigh temperature domains, and subsequently infiltrate the lower crust, where they generate anhydrous granulite mineral assemblages. The brines can reach upper crustal levels, possibly even the surface, along major shear zones, where granitoids are generated through brine streaming in addition to those formed by dehydration melting in upper crustal levels.

Item ID: 75518
Item Type: Article (Research - C1)
ISSN: 2588-9192
Keywords: Brines, CO2, Continental crust, Granulite, Lower crust
Copyright Information: © 2022 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Date Deposited: 19 Jul 2022 01:45
FoR Codes: 37 EARTH SCIENCES > 3705 Geology > 370503 Igneous and metamorphic petrology @ 100%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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