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Insights on the Process of Two-stage Coronae Formation at Olivine-plagioclase Contact in Mafic Dyke from Palghat Cauvery Shear Zone, southern India
Mineralogy and Petrology
  • Meenakshi Banerjee, Indian Institute of Technology
  • Upama Dutta, Indian Institute of Technology
  • R. Anand, Indian Institute of Technology
  • Zachary D. Atlas, University of South Florida
Document Type
Article
Publication Date
1-1-2019
Keywords
  • Pan-African orogeny,
  • Corona,
  • Mafic,
  • Cauvery,
  • Pseudomorph
Digital Object Identifier (DOI)
https://doi.org/10.1007/s00710-019-00674-y
Disciplines
Abstract

Coronae between olivine and plagioclase are a common replacement texture in mafic rocks by magmatic and metamorphic processes. Mafic dykes from Palghat Cauvery Shear Zone (PCSZ) of the granulite terrane of southern India display such multilayer coronae between olivine (Ol) and plagioclase (Pl), composed of orthopyroxene-magnetite (OM) and amphibole (Prg). Deformation twins, kinking, bending and fractures in plagioclase laths suggest that the rock underwent post-emplacement deformation. However, amphibole in the plagioclase fractures and preservation of delicate coronae texture indicate that the replacement texture grew in a static condition. Field occurrence and textural relations suggest that the coronae developed in two stages: (1) Stage-I: Ol → OM, followed by (2) Stage-II: OM + Pl = Prg during rehydration of the granulite host rock. Balanced chemical reactions and formation of hydrous amphibole at the expense of anhydrous reactants during Stage-II demonstrates that replacement of earlier minerals occurred in a fluid-present open system. Results from the pseudosection and the μMgO–μCaO phase diagram, suggest fluid played a crucial role in the transition from Stage-I to Stage-II corona at a P-T condition of ~650 ± 50 °C and 5.5–6 kbar. The multilayer coronae is likely to have resulted from late Neoproterozoic thermal metamorphism of granulite terrane of southern India during Pan-African orogeny.

Citation / Publisher Attribution

Mineralogy and Petrology, v. 113, p. 625-649

Citation Information
Meenakshi Banerjee, Upama Dutta, R. Anand and Zachary D. Atlas. "Insights on the Process of Two-stage Coronae Formation at Olivine-plagioclase Contact in Mafic Dyke from Palghat Cauvery Shear Zone, southern India" Mineralogy and Petrology Vol. 113 (2019) p. 625 - 649
Available at: http://works.bepress.com/zachary-atlas/14/