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, Yoshiyuki Iizura

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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 witfi 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 tfiree 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 TiO2 wt%. Whole-rock Zr saturation temperature estimates indicate the initial average magma temperatures were ~940 ± 21 °C for the Panzhihua pluton, ~860 ± 17 0C for the Baima pluton, and ~897 ± 14 °C for the Taihe pluton. The initial Fmelt(wt%) values were calculated to be 1.1 ± 0.1,0.8 ± 0.1 and 1.1 ± 0.1 wt% for the Panzhihua, Baima and Taihe plutons, respectively. The estimated Fmelt(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 Fmelt(wt%) value for me Baima pluton can be accounted for. The presence of titanite + magnetite + quartz in the Baima syenites indicates oxidizing-/02 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.

Original languageEnglish
Pages (from-to)45-61
Number of pages17
JournalEuropean Journal of Mineralogy
Volume23
Issue number1
DOIs
Publication statusPublished - 2011 Jan 1

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Amphibole Asbestos
large igneous province
Mineralogy
pluton
Permian
mineralogy
Rocks
Crystallization
Minerals
amphibole
Chemical analysis
Ferrosoferric Oxide
Igneous rocks
Quartz
Accessories
Trace Elements
aenigmatite
peralkaline rock
magma
richterite

Keywords

  • A-type granite
  • Aenigmatite
  • Ferrorichterite
  • Oxygen fugacity
  • Peralkaline
  • Zr saturation thermometry

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

@article{215ffcfb0a234cf498f0bac728f889f8,
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",
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 witfi 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 tfiree 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 TiO2 wt{\%}. Whole-rock Zr saturation temperature estimates indicate the initial average magma temperatures were ~940 ± 21 °C for the Panzhihua pluton, ~860 ± 17 0C for the Baima pluton, and ~897 ± 14 °C for the Taihe pluton. The initial Fmelt(wt{\%}) values were calculated to be 1.1 ± 0.1,0.8 ± 0.1 and 1.1 ± 0.1 wt{\%} for the Panzhihua, Baima and Taihe plutons, respectively. The estimated Fmelt(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 Fmelt(wt{\%}) value for me Baima pluton can be accounted for. The presence of titanite + magnetite + quartz in the Baima syenites indicates oxidizing-/02 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.",
keywords = "A-type granite, Aenigmatite, Ferrorichterite, Oxygen fugacity, Peralkaline, Zr saturation thermometry",
author = "Shellnutt, {J. Gregory} and Yoshiyuki Iizura",
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T1 - Mineralogy from three peralkaline granitic plutons of the Late Permian Emeishan large igneous province (SW China)

T2 - Evidence for contrasting magmatic conditions of A-type granitoids

AU - Shellnutt, J. Gregory

AU - Iizura, Yoshiyuki

PY - 2011/1/1

Y1 - 2011/1/1

N2 - 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 witfi 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 tfiree 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 TiO2 wt%. Whole-rock Zr saturation temperature estimates indicate the initial average magma temperatures were ~940 ± 21 °C for the Panzhihua pluton, ~860 ± 17 0C for the Baima pluton, and ~897 ± 14 °C for the Taihe pluton. The initial Fmelt(wt%) values were calculated to be 1.1 ± 0.1,0.8 ± 0.1 and 1.1 ± 0.1 wt% for the Panzhihua, Baima and Taihe plutons, respectively. The estimated Fmelt(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 Fmelt(wt%) value for me Baima pluton can be accounted for. The presence of titanite + magnetite + quartz in the Baima syenites indicates oxidizing-/02 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.

AB - 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 witfi 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 tfiree 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 TiO2 wt%. Whole-rock Zr saturation temperature estimates indicate the initial average magma temperatures were ~940 ± 21 °C for the Panzhihua pluton, ~860 ± 17 0C for the Baima pluton, and ~897 ± 14 °C for the Taihe pluton. The initial Fmelt(wt%) values were calculated to be 1.1 ± 0.1,0.8 ± 0.1 and 1.1 ± 0.1 wt% for the Panzhihua, Baima and Taihe plutons, respectively. The estimated Fmelt(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 Fmelt(wt%) value for me Baima pluton can be accounted for. The presence of titanite + magnetite + quartz in the Baima syenites indicates oxidizing-/02 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.

KW - A-type granite

KW - Aenigmatite

KW - Ferrorichterite

KW - Oxygen fugacity

KW - Peralkaline

KW - Zr saturation thermometry

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