Tectonic Generation of Pseudotachylytes and Volcanic Rocks: Deep-Seated Magma Sources of Crust-Mantle Transition in the Baikal Rift System, Southern Siberia

Sergei Rasskazov,Yi-Min Sun,Tatyana Yasnygina,Youseph Ailow,Nikolay Gerasimov,Irina Chuvashova,Elena Saranina

doi:10.3390/min11050487

Abstract

Volcanic rocks from deep-seated sources of the crust-mantle transition (CMT) are geochemically distinguished from those of ocean island basalts (OIB). Here, we report geochemical data on tectonic pseudotachylytes from the Main Sayan Fault (MSF) and volcanic rocks from the Kamar-Stanovoy Zone of Hot Transtension (KSZHT) that represent the deep-seated CMT magmatic sources in the central part of the Baikal Rift System (BRS). The tectonic generation of the KSZHT magmas between 18.1 and 11.7 Ma is compared with present-day seismogenic deformations in the middle-upper crust of the South Baikal Basin and adjacent Tunka Valley, where strong earthquakes are distributed along the Main Sayan and Primorye sutures of the Siberian paleocontinent. From a detail seismic tomography model and geological evidence, we infer that the KSZHT crust–mantle magmatic processes were due to delamination and lamination of a thickened root part of the South Baikal Orogen existed in the Late Cretaceous and Paleogene. In addition, we identify similar deep-seated CMT sources for melts erupted in the past 17 Ma from a delaminated root part of the East Hangay Orogen and adjacent Orkhon-Selenga Saddle in the southwestern BRS. We suggest that both in the central and in the southwestern BRS, the deep-seated CMT magma sources designate cooperative pull-to-axis and convergent effects created in the Japan-Baikal Geodynamic Corridor and in the Indo-Asian interactional region, respectively.

Highlights

In recent decades, intraplate volcanic eruptions were a priori interpreted as associated with deep mantle plumes, alternative causes, such as abrupt lateral changes in stress at structural discontinuities of the lithosphere or the mantle global warming, were advocated to explain the origin of some Large Igneous Provinces [1,2]
Volcanic rocks ofof the initial and final eruption phases inin the Kultuk volcanoes yield common trends with basic pseudotachylytes (Figures and Kultuk volcanoes yield common trends with basic pseudotachylytes (Figures 8–10) that that assumes searching for genetic relationships between the rock sources with a perassumes searching for genetic relationships between the rock sources with a perspective spective of creating a comprehensive model for the development of seismotectonic proof creating a comprehensive model for the development of seismotectonic processes in cesses thesub-crustal crust and sub-crustal mantle of the Slyudyanka paleocollision zone, the crustin and mantle of the Slyudyanka paleocollision zone, inherited byinherthe ited by the South the other hand, clearly is expressed
To recognize genetic links between pseudotachylytes and volcanic rocks from the central Baikal Rift System (BRS), we present data on major oxides and trace elements of pseudotachylytes and host mylonites from the Main Sayan Fault (MSF) and emphasize a magmatic origin of the former

Summary

Introduction

Intraplate volcanic eruptions were a priori interpreted as associated with deep mantle plumes, alternative causes, such as abrupt lateral changes in stress at structural discontinuities of the lithosphere or the mantle global warming, were advocated to explain the origin of some Large Igneous Provinces [1,2]. Less commonly hypothesized were tectonically generated melts as a result of decompression in the shallow lithospheric mantle or crust. Such interpretations were suggested for volcanic rocks from. Volcanic rocks from the Baikal Rift System (BRS) have mainly OIB-like geochemical signatures, consistent with seismic tomography images that show low-velocity anomalies, possibly related to deep-seated magma sources occurring in the upper mantle and transition layer. These could provide migrated volcanic eruptions through the moving lithosphere [18]. Volcanic rocks from the East Hangay Orogen and adjacent

Objectives

Methods

Findings

Discussion

Conclusion