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

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.

Olivine as an indicator of polygenic assemblage of inclusions from Late Cenozoic volcanic rocks in the Tunka Valley, Baikal Rift Zone

“…На Витимском плоскогорье ассоциация глубинных включений из среднемиоценовых пикробазальтов характеризовалась геотермой на 50-100°С ниже геотермы ассоциации глубинных включений из четвертичных базанитов (Ащепков, 1991). Микроэлементные характеристики и изотопные отношения Nd, Sr и Pb свидетельствуют о резких различиях источников четвертичных базанитов Витимского плоскогорья и более ранних базальтов и базанитов миоценового и плиоценового возраста Чувашова и др., 2017;Rasskazov et al, 2020). Между тем Sm-Nd изотопные определения по гранат-клинопироксенсеновым парам дают оценки возраста глубинных пород от 50 млн лет и моложе , поэтому очевидно, что гранатовые парагенезисы глубинных включений были непосредственно связаны с образованием расплавной аномалии в мантии под Витимским плоскогорьем и находятся в родственных отношениях с вмещающими вулканитами.…”