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Probing crustal thickness evolution and geodynamic processes in the past from magma records; an integrated approach

J. Ganne, Wouter P. Schellart, G. Rosenbaum, X. Feng and V. De Andrade
Probing crustal thickness evolution and geodynamic processes in the past from magma records; an integrated approach
Special Paper - Geological Society of America (January 2017) 526: 1-25

Abstract

A new and simple integrated approach is proposed for qualitatively unravelling the crustal thickness of fossil magmatic systems based on the chemical and thermal records in amphibole-bearing magmatic rocks. Statistical analyses applied to a large multidimensional amphibole database show that Ti-rich and Si-poor magmatic amphiboles, which formed at high-temperature (T) conditions (>950 degrees C), were dominantly developed in basaltic to basaltic-andesitic (SiO (sub 2) -poor, i.e., <55 wt%) magma within relatively thin crust (5-10 km). We find that for crustal thicknesses larger than 10 km, the occurrence of high-T amphiboles and basaltic magma decreases with increasing crustal thickness. This is because of mineral filtering in "mature" deep crustal hot zones that occur at the crust-mantle boundary (Moho). Given that subducting plates exert a direct control on the structural evolution (shortening or extension) of the overriding plates, probing crustal thickness in the past provides first-order information on the geodynamic processes that took place at plate margins. Using this approach, we document the progressive buildup of a thick (>40 km) Jurassic to Cretaceous accretionary belt along the circum-Pacific orogenic belts that bounded the Panthalassa Ocean. The destruction of this thick belt started at ca. 125 Ma and was initially recorded by the thinnest magmatic systems hosting amphibole-bearing magma. Thinning of the circum-Pacific orogenic belts became widespread in the northern regions of western America and in the western Pacific after ca. 75 Ma, possibly in response to oceanic plate segmentation, which triggered slab rollback and overriding plate extension.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 526
Title: Probing crustal thickness evolution and geodynamic processes in the past from magma records; an integrated approach
Affiliation: Universite Toulouse III, Institut de Recherche pour le Developpement, Toulouse, France
Pages: 1-25
Published: 20170127
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 114
Accession Number: 2017-020561
Categories: Solid-earth geophysicsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository Item 2017108
Illustration Description: illus. incl. geol. sketch maps
Secondary Affiliation: Monash University, AUS, AustraliaUniversity of Queensland, AUS, AustraliaArgonne National Laboratory, USA, United States
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: 201714
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