Mantle Evolution of Asia Inferred from Pb Isotopic Signatures of Sources for Late Phanerozoic Volcanic Rocks

Sergei Rasskazov,Irina Chuvashova,Tatyana Yasnygina,Elena Saranina

doi:10.3390/min10090739

Sergei Rasskazov, Irina Chuvashova + Show 2 more

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https://doi.org/10.3390/min10090739

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Abstract

We present a systematic study of Pb isotope ages obtained from sources of the late Phanerozoic volcanic rocks from unstable Asia and also volcanic rocks and kimberlites from stable regions of the Siberian and Indian paleocontinents. In the mantle sources, we have recorded events of the Early, Middle, and Late epochs of the Earth’s evolution. Evidence on the Early epoch are preserved in sources of the protolithosphere and viscous lower protomantle likely generated from the Hadean magma ocean about 4.51 and 4.44 Ga and in sources of the viscous upper mantle that acquired low µ and elevated µ (LOMU and ELMU) signatures in the early Archean (4.0–3.7 Ga). The Middle and Late epochs are denoted by sources of the viscous upper mantle that was generated, respectively, in the late Archean-Paleoproterozoic (2.9–2.6 Ga and 2.0–1.8 Ga) and in the Neoproterozoic-late Phanerozoic (0.7–0.6 Ga and < 0.25 Ga). Our results show the specific role of the mantle beneath unstable Asia in terms of globally varied µ signatures and the same mantle epochs in sources of the late Phanerozoic volcanic rocks and kimberlites from stable regions of the Siberian and Indian paleocontinents, but with high μ (HIMU) signatures that are distributed worldwide and explained by sulfide sequestration of Pb from the mantle to the core. We refer the LOMU-ELMU mantle sources to the Asian high-velocity lower mantle domain and propose that the HIMU generating processes were focused mainly in the South Pacific and African low-velocity lower mantle domains in the Middle Mantle Epoch of the Earth’s evolution due to influence of the unbalanced solid core.

Highlights

The modern Earth’s mantle is globally heterogeneous
Our results show the specific role of the mantle beneath unstable Asia in terms of globally varied μ signatures and the same mantle epochs in sources of the late Phanerozoic volcanic rocks and kimberlites from stable regions of the Siberian and Indian paleocontinents, but with high μ (HIMU) signatures that are distributed worldwide and explained by sulfide sequestration of Pb from the mantle to the core
The obtained ages of protoliths in mantle sources of volcanic rocks erupted in unstable Asia, are

Summary

Introduction

The modern Earth’s mantle is globally heterogeneous. High-velocity domains were determined in the lower mantle under Asia and North America, whereas low-velocity ones under the southernPacific Ocean and Africa [1]. The global Earth’s heterogeneity was first indicated by high 208 Pb/204 Pb ratios (∆8/4 > 60) in ocean island basalts (OIB) of the 30th degrees south latitude, called the DUPAL (Dupré–Allègre) anomaly [3]. Later, sources of this anomaly were connected with low velocities of seismic waves in the lower mantle [1]. Sources of this anomaly were connected with low velocities of seismic waves in the lower mantle [1] This isotopic signature was defined in basalts from the central part of the high-velocity Asian lower mantle domain as characteristic of the Neoproterozoic Tuva-Mongolian paleomicrocontinent, in contrast to DUPAL-free basalts from the adjacent East Tuva and Dzhida

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