Abstract Using field observations, microstructures, and back-scattered electron microscopy in the synplutonic dykes and microgranular enclaves (MEs), this study proposes a schematic model that depicts various stages of mafic and felsic magma interactions during the evolution of Berach granitoids. The synplutonic dykes, which were injected into the crystallizing host granitoid magma, display varied characteristics acquired during a range of interactions at shallow to deep conditions. The chilled margins, brecciation, and back-veining in the MEs are produced by rapid crystallization, disruption due to magmatic pressure, and the reverse crystallization within the host granitoids. The MEs can be classified as fine-grained, equigranular, phenocryst-free, and phenocryst-bearing; the last one typically contains xenocrystic (disequilibrated) phases. The MEs are formed under low crystallinity conditions, and their varied shapes are caused by magmatic strain. Plagioclase micro-phenocrysts record the evidence of mafic and felsic magma mixing. The differences in volume and viscosity of the mafic and felsic magma, however, inhibit complete physical mixing. This study also examines the hybrid origin of Berach granitoids. The deeper derived mafic to hybrid magma was injected, mingled, and undercooled with the shallower crystallizing granitoid magma, and produced various types of MEs at different levels of their interactions. Research highlights <UnorderedList Mark="Bullet"> <ItemContent> Multistage interactions between mafic and felsic magmas is recorded by synplutonic dykes, microgranular enclaves and the host Berach Granitoids in the Aravalli Craton, NW India. </ItemContent> <ItemContent> Mesocopic to microscopic characteristics of the enclaves and host rocks imply mixing and mingling of the mafic to hybrid magmas within a crystallising granitoid magma chamber. </ItemContent> <ItemContent> The disequilibrium texture in plagioclase microphenocrysts in the enclaves and host-granitoid formed during interaction between mafic and felsic magma. </ItemContent> <ItemContent> Continental crust derived Berach Granitoid magma interacted with deeper mantle derived mafic magma in subvolcanic to plutonic conditions. </ItemContent> </UnorderedList>

Field and microstructural evidence of coeval mafic–felsic magma mixing and mingling in the evolution of Neoarchean Berach granitoids, Aravalli craton, NW India

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发表日期：

2025年12月27日

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Bhagirathi Panigrahi,
Ch Narshimha,
Santosh Kumar,
Deepak C Srivastava

摘要

Abstract

Using field observations, microstructures, and back-scattered electron microscopy in the synplutonic dykes and microgranular enclaves (MEs), this study proposes a schematic model that depicts various stages of mafic and felsic magma interactions during the evolution of Berach granitoids. The synplutonic dykes, which were injected into the crystallizing host granitoid magma, display varied characteristics acquired during a range of interactions at shallow to deep conditions. The chilled margins, brecciation, and back-veining in the MEs are produced by rapid crystallization, disruption due to magmatic pressure, and the reverse crystallization within the host granitoids. The MEs can be classified as fine-grained, equigranular, phenocryst-free, and phenocryst-bearing; the last one typically contains xenocrystic (disequilibrated) phases. The MEs are formed under low crystallinity conditions, and their varied shapes are caused by magmatic strain. Plagioclase micro-phenocrysts record the evidence of mafic and felsic magma mixing. The differences in volume and viscosity of the mafic and felsic magma, however, inhibit complete physical mixing. This study also examines the hybrid origin of Berach granitoids. The deeper derived mafic to hybrid magma was injected, mingled, and undercooled with the shallower crystallizing granitoid magma, and produced various types of MEs at different levels of their interactions.

Research highlights

Multistage interactions between mafic and felsic magmas is recorded by synplutonic dykes, microgranular enclaves and the host Berach Granitoids in the Aravalli Craton, NW India.

Mesocopic to microscopic characteristics of the enclaves and host rocks imply mixing and mingling of the mafic to hybrid magmas within a crystallising granitoid magma chamber.

The disequilibrium texture in plagioclase microphenocrysts in the enclaves and host-granitoid formed during interaction between mafic and felsic magma.

Continental crust derived Berach Granitoid magma interacted with deeper mantle derived mafic magma in subvolcanic to plutonic conditions.