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Mantle heating at ca. 2 Ga by continental insulation; evidence from granites and eclogites

R. Tamblyn, D. Hasterok, M. Hand and M. Gard
Mantle heating at ca. 2 Ga by continental insulation; evidence from granites and eclogites
Geology (Boulder) (September 2021) 50 (1): 91-95

Abstract

Igneous and metamorphic rocks contain the mineralogical and geochemical record of thermally driven processes on Earth. The generally accepted thermal budget of the mantle indicates a steady cooling trend since the Archean. The geological record, however, indicates this simple cooling model may not hold true. Subduction-related eclogites substantially emerge in the rock record from 2.1 Ga to 1.8 Ga, indicating that average mantle thermal conditions cooled below a critical threshold for widespread eclogite preservation. Following this period, eclogite disappeared again until ca. 1.1 Ga. Coincident with the transient emergence of eclogite, global granite chemistry recorded a decrease in Sr and Eu and increases in yttrium and heavy rare earth element (HREE) concentrations. These changes are most simply explained by warming of the thermal regime associated with granite genesis. We suggest that warming was caused by increased continental insulation of the mantle at this time. Ultimately, secular cooling of the mantle overcame insulation, allowing the second emergence and preservation of eclogite from ca. 1.1 Ga until present.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 50
Serial Issue: 1
Title: Mantle heating at ca. 2 Ga by continental insulation; evidence from granites and eclogites
Affiliation: University of Adelaide, Department of Earth Sciences, Adelaide, South Aust., Australia
Pages: 91-95
Published: 20210920
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 36
Accession Number: 2021-071945
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202150
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