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GEOREF RECORD

Clinoenstatite exsolution in diopsidic augite of Dabieshan; garnet peridotite from depth of 300 km

Liu Xiang-Wen, Jin Zhen-Min and Harry W. Green
Clinoenstatite exsolution in diopsidic augite of Dabieshan; garnet peridotite from depth of 300 km
American Mineralogist (April 2007) 92 (4): 546-552

Abstract

Clinoenstatite exsolution lamellae have been discovered in clinopyroxene grains of garnet peridotite from the Bixiling massif of the ultrahigh-pressure metamorphic (UHPM) terrane in the Dabie Mountains, China. Using transmission electron microscopy, we show here that although the lamellae are low clinoenstatite (Lclen) with P2 (sub 1) /c space-group symmetry, they contain nanometer-scale antiphase domains indicating that the originally precipitating phase had C2/c space-group symmetry. The lamellae are oriented parallel to [010] and approximately 18 degrees to [001] of the host--approximately parallel to (401). Both the very cold exhumation path of the Dabie UHPM terrane and the orientation of the lamellae preclude the possibility that the originally precipitating phase could have been high-temperature clinoenstatite (HTclen). We conclude that the lamellae precipitated as high-pressure clinoenstatite (HPclen) and subsequently inverted to Lclen. Analysis of the incomplete high-pressure crystallographic data available for compositions approximating those of the lamellae and host suggests a minimum pressure of precipitation of approximately 9 GPa for Dabie and about 12 GPa for similar exsolution previously observed in the Alpe Arami peridotite, Switzerland. The Bixiling complex is a crustal cumulate, hence this result extends the minimum depth of subduction of continental rocks in the Dabie/SuLu orogen to approximately 300 km (P>9 GPa).


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 92
Serial Issue: 4
Title: Clinoenstatite exsolution in diopsidic augite of Dabieshan; garnet peridotite from depth of 300 km
Affiliation: China University of Geosciences, State Key Laboratory of Geological Processes and Mineral Resources, Wuhan, China
Pages: 546-552
Published: 200704
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 43
Accession Number: 2007-047375
Categories: Igneous and metamorphic petrologyMineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
N30°00'00" - N32°00'00", E114°00'00" - E117°00'00"
Secondary Affiliation: University of California at Riverside, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200725
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