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Mineralogy from three peralkaline granitic plutons of the Late Permian Emeishan large igneous province (SW China); evidence for contrasting magmatic conditions of A-type granitoids

J. Gregory Shellnutt and Yoshiyuki Iizuka
Mineralogy from three peralkaline granitic plutons of the Late Permian Emeishan large igneous province (SW China); evidence for contrasting magmatic conditions of A-type granitoids
European Journal of Mineralogy (January 2011) 23 (1): 45-61

Abstract

The Emeishan large igneous province contains a diverse assemblage of igneous rocks including mildly peralkaline granitic rocks of A-type affinity. The granitic rocks from the Panzhihua, Baima and Taihe plutons are temporally, spatially and chemically associated with layered mafic-ultramafic intrusions. Electron microprobe analyses of the major and accessory minerals along with major and trace element data were used to document the magmatic conditions of the three peralkaline plutons. The amphiboles show magmatic/subsolidus trends and are primarily sodic-calcic in composition (i.e., ferrorichterite or richterite). Sodic (i.e., riebeckite-arfvedsonite) amphiboles are restricted to the Panzhihua and Taihe plutons. The amphiboles from the Panzhihua and Taihe granites are very similar in composition whereas amphiboles from the Baima syenites have higher MgO wt% and lower FeOt wt% and TiO (sub 2) wt%. Whole-rock Zr saturation temperature estimates indicate the initial average magma temperatures were approximately 940+ or -21 degrees C for the Panzhihua pluton, approximately 860+ or -17 degrees C for the Baima pluton, and approximately 897+ or -14 degrees C for the Taihe pluton. The initial F (sub melt) (wt%) values were calculated to be 1.1+ or -0.1, 0.8+ or -0.1 and 1.1+ or -0.1 wt% for the Panzhihua, Baima and Taihe plutons, respectively. The estimated F (sub melt) (wt%) values are higher than what can be accounted for in the Panzhihua and Taihe plutons and indicate that they may have lost F during crystallization. In contrast the F (sub melt) (wt%) value for the Baima pluton can be accounted for. The presence of titanite+magnetite+quartz in the Baima syenites indicates oxidizing fO (sub 2) conditions whereas the presence of aenigmatite and ilmenite in the Panzhihua and Taihe granites indicate that they were relatively reducing. Although the Atype granitoids formed by the same processes (i.e., fractional crystallization of mafic magmas), their differences in major element and mineral chemistry are likely related to a combination of initial bulk magma composition and magmatic oxidation state.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 23
Serial Issue: 1
Title: Mineralogy from three peralkaline granitic plutons of the Late Permian Emeishan large igneous province (SW China); evidence for contrasting magmatic conditions of A-type granitoids
Affiliation: Academia Sinica, Institute of Earth Sciences, Taipei, Taiwan
Pages: 45-61
Published: 201101
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 63
Accession Number: 2011-026557
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables, geol. sketch map
N26°25'40" - N28°00'00", E102°30'00" - E103°00'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201115
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