Abstract This study investigates the mantle transition zone (MTZ) structure beneath the Eastern Indian craton (EIC) using 666 radial P-receiver functions (PRFs) from 16 broadband seismic stations deployed across the Singhbhum-Odisha craton (SOC). Common conversion point (CCP) stacking reveals average conversion times of 45 ± 1.2 s for the 410 km discontinuity (d410) and 69.7 ± 1.8 s for the 660 km discontinuity (d660), yielding a differential time of 24.7 ± 2.2 s. This corresponds to an MTZ thickness of 235 ± 11 km, statistically indistinguishable from the global cratonic average (242 ± 8 km, p = 0.13) within uncertainty, indicating a slight overall thinning of the MTZ, which is consistent with observations in other cratonic regions worldwide. Negative-polarity arrivals preceding the d410 and d660 conversions are consistent with seismic velocity decreases, potentially indicating that the modelling results highlight a widespread low-velocity layer (LVL) over the d410, potentially linked to hydrous phases in the transition zone. However, alternative explanations including velocity gradients, seismic anisotropy, and CCP stacking artifacts cannot be excluded with the current dataset. If confirmed by complementary geophysical techniques (magnetotellurics, shear-wave receiver functions, anisotropy analysis), the observed velocity structure would suggest MTZ water contents of ~0.1–0.3 wt%, potentially linked to volatile infiltration during Gondwana assembly (~550–500 Ma) or India-Asia collision (ongoing since ~50 Ma). Furthermore, a similar LVL above the d660 suggests the accumulation of ancient, subducted oceanic materials or increased water content, mirroring findings in subduction zones around the Pacific Ring of Fire and Uttarakhand Himalaya. These observations imply complex geological processes, including possible Archean plume activity that has shaped the mantle structure of this cratonic region, influencing its thermal and compositional state. This study provides the first detailed seismological constraints on MTZ structure beneath the EIC and enhances our understanding of lithospheric dynamics and provides insights into the tectonic history of the EIC opening pathways for future integrated geophysical-petrological-geodynamic research into its mantle evolution and its role in shaping Earth’s deep dynamics. Research highlights <UnorderedList Mark="Bullet"> <ItemContent> First CCP stacking of 666 PRFs reveals MTZ thickness of 235 ± 11 km beneath Eastern Indian craton, consistent with global cratons. </ItemContent> <ItemContent> Widespread low-velocity layers atop d410 (348–385 km) and d660 (601–623 km) suggest hydrous phases or subducted remnants. </ItemContent> <ItemContent> LVLs imply MTZ water content 0.1–0.3 wt%, linked to Gondwana tectonics or India-Asia collision. </ItemContent> </UnorderedList>

P-receiver function imaging of mantle transition zone structure and heterogeneity beneath the Eastern Indian craton

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发表日期：

2026年7月22日

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Prantik Mandal

摘要

Abstract

This study investigates the mantle transition zone (MTZ) structure beneath the Eastern Indian craton (EIC) using 666 radial P-receiver functions (PRFs) from 16 broadband seismic stations deployed across the Singhbhum-Odisha craton (SOC). Common conversion point (CCP) stacking reveals average conversion times of 45 ± 1.2 s for the 410 km discontinuity (d410) and 69.7 ± 1.8 s for the 660 km discontinuity (d660), yielding a differential time of 24.7 ± 2.2 s. This corresponds to an MTZ thickness of 235 ± 11 km, statistically indistinguishable from the global cratonic average (242 ± 8 km, p = 0.13) within uncertainty, indicating a slight overall thinning of the MTZ, which is consistent with observations in other cratonic regions worldwide. Negative-polarity arrivals preceding the d410 and d660 conversions are consistent with seismic velocity decreases, potentially indicating that the modelling results highlight a widespread low-velocity layer (LVL) over the d410, potentially linked to hydrous phases in the transition zone. However, alternative explanations including velocity gradients, seismic anisotropy, and CCP stacking artifacts cannot be excluded with the current dataset. If confirmed by complementary geophysical techniques (magnetotellurics, shear-wave receiver functions, anisotropy analysis), the observed velocity structure would suggest MTZ water contents of ~0.1–0.3 wt%, potentially linked to volatile infiltration during Gondwana assembly (~550–500 Ma) or India-Asia collision (ongoing since ~50 Ma). Furthermore, a similar LVL above the d660 suggests the accumulation of ancient, subducted oceanic materials or increased water content, mirroring findings in subduction zones around the Pacific Ring of Fire and Uttarakhand Himalaya. These observations imply complex geological processes, including possible Archean plume activity that has shaped the mantle structure of this cratonic region, influencing its thermal and compositional state. This study provides the first detailed seismological constraints on MTZ structure beneath the EIC and enhances our understanding of lithospheric dynamics and provides insights into the tectonic history of the EIC opening pathways for future integrated geophysical-petrological-geodynamic research into its mantle evolution and its role in shaping Earth’s deep dynamics.

Research highlights

First CCP stacking of 666 PRFs reveals MTZ thickness of 235 ± 11 km beneath Eastern Indian craton, consistent with global cratons.

Widespread low-velocity layers atop d410 (348–385 km) and d660 (601–623 km) suggest hydrous phases or subducted remnants.

LVLs imply MTZ water content 0.1–0.3 wt%, linked to Gondwana tectonics or India-Asia collision.