A red bole zircon record of cryptic silicic volcanism in the Deccan Traps, India

Liam O’Connor,Blair Schoene,Kyle M Samperton,Michael P Eddy,Dawid Szymanowski

doi:10.1130/g49613.1

Liam O’Connor, Blair Schoene + Show 3 more

Open Access

https://doi.org/10.1130/g49613.1

Copy DOI

Abstract

Abstract Silicic magmas within large igneous provinces (LIPs) are understudied relative to volumetrically dominant mafic magmas despite their prevalence and possible contribution to LIP-induced environmental degradation. In the 66 Ma Deccan LIP (India), evolved magmatism is documented, but its geographic distribution, duration, and significance remain poorly understood. Zircons deposited in weathered Deccan lava flow tops (“red boles”) offer a means of indirectly studying potentially widespread, silicic, explosive volcanism spanning the entire period of flood basalt eruptions. We explored this record through analysis of trace elements and Hf isotopes in zircon crystals previously dated by U–Pb geochronology. Our results show that zircon populations within individual red boles fingerprint distinct volcanic sources that likely developed in an intraplate setting on cratonic Indian lithosphere. However, our red bole zircon geochemical and isotopic characteristics do not match those from previously studied silicic magmatic centers, indicating that they must derive from yet undiscovered or understudied volcanic centers associated with the Deccan LIP.

Highlights

Silicic (>60% SiO2) igneous rocks are commonly found within dominantly mafic large igneous provinces (LIPs), but their overall relationship to the development of LIPs is poorly understood (Bryan et al, 2002)
We explored the character and extent of explosive silicic volcanism coincident with the emplacement of Deccan Traps (DT) flood basalts by leveraging volcanic zircons deposited throughout the basalt stratigraphy
We present trace element and hafnium (Hf) isotopic compositions of previously dated zircon crystals to provide new constraints on silicic volcanism within the Deccan LIP and for comparison with the limited number of silicic magmatic centers far characterized by U–Pb zircon geochronology and Hf isotopes (Basu et al, 2020a)

Summary

Introduction

Silicic (>60% SiO2) igneous rocks are commonly found within dominantly mafic large igneous provinces (LIPs), but their overall relationship to the development of LIPs is poorly understood (Bryan et al, 2002). We present trace element and hafnium (Hf) isotopic compositions of previously dated zircon crystals to provide new constraints on silicic volcanism within the Deccan LIP and for comparison with the limited number of silicic magmatic centers far characterized by U–Pb zircon geochronology and Hf isotopes (Basu et al, 2020a). Our results are consistent with distinct volcanic origins for the zircons in red bole horizons, though their geochemical characteristics do not match well any of the considered silicic magmatic centers in western India.

Results

Conclusion