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Mantle underplating, granite tectonics, and metamorphic P-T-t paths

Rosalyn G. Warren and David J. Ellis
Mantle underplating, granite tectonics, and metamorphic P-T-t paths
Geology (Boulder) (July 1996) 24 (7): 663-666

Abstract

Arrival of mantle-derived magma at the base of the continental crust leads to melting, major crustal reworking, and overturn; these processes can form both counterclockwise and high-T clockwise pressure-temperature-time (P-T-t) paths in the same tectonic episode. Regions with low-P, high-T counterclockwise P-T-t paths form where the upper crust moves down to compensate for the upward ascent of granite. High-T shear zones separate these regions from ascending granite plutons and their migmatitic envelopes, where medium- to high-pressure rocks record rapid uplift along a clockwise P-T-t path. The increase in pressure in counterclockwise P-T-t paths does not require tectonic thickening of the crust but results from ensialic, mantle-heat - initiated overturn of the continental crust. Nor does the attenuation of deep-crustal rocks denote extension; instead, it results from lateral migration of low-density melts in the source region of the ascending granites. As the crustal overturn is gravity driven to create isostatic equilibrium, the high-T metamorphic paths end in isobaric cooling. The mantle-derived magma may have its source in a mantle plume, impinging beneath continental crust or, in a back-arc setting, may result from slab pull-back and replacement by hot asthenosphere.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 24
Serial Issue: 7
Title: Mantle underplating, granite tectonics, and metamorphic P-T-t paths
Affiliation: Australian National University, Department of Geology, Canberra, Australia
Pages: 663-666
Published: 199607
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 47
Accession Number: 1996-054298
Categories: Solid-earth geophysicsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Key Cent. Geochem. Evol. and Metallogeny Continents, Publ. No. 53
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199618
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