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The origin of the Late Quaternary back-arc volcanic rocks from Kamchatka: evidence from the compositions of olivine and olivine-hosted melt inclusions

journal contribution
posted on 2023-05-21, 05:31 authored by Nekrylov, N, Popov, DV, Plechov, PY, Shcherbakov, VD, Leonid Danyushevsky
A quarter of Kamchatka’s Late Quaternary (<50 ka) volcanic deposits is erupted in the back-arc along the Sredinny Range (SR). The eruptions are represented by several dozens of polygenetic volcanoes and hundreds of monogenetic volcanoes located along a SW-NE lineament in the western part of the peninsula. Previous studies explained the generation of magma by (1) fluid induced melting of the mantle due to the input of H2O from the presently subducting slab, (2) decompression-induced melting of the mantle caused by upwelling of the asthenosphere, or (3) delamination and melting of the lower crust of the SR. We present new major and trace elements in olivine and major, trace and volatile (H2O, Cl, F and S) data in quenched olivine-hosted melt inclusions (MI) from three Holocene monogenetic volcanoes that are located in the southern, central and northern volcanic zones of the SR. The reconstructed melts range from basalts to basaltic andesites of medium-K affinity and exhibit trace element signatures that are transitional between island arc magmas (IAM) and enriched mid-ocean ridge basalts (E-MORB). They have high H2O concentrations (from ~ 1.5 to 2.5 wt.%) compared to MORB with similar Nb/Y ratios, which suggests that the H2O played an essential role in their origin. The high H2O/Cl (from ~ 50 to ~ 100) and Ba/Rb (from ~ 20 to ~ 50) ratios and low Cl/K2O (from ~ 0.02 to ~ 0.04) and Cl/F (from ~ 0.2 to ~ 0.5) ratios in these melts indicate that the budget of volatile components was controlled by the breakdown of amphibole. The Fe/Mn ratios and Ni contents in olivine from the studied Holocene volcanoes suggest significant contributions of melts derived from a pyroxenitic source. We propose that the parental magmas of these volcanoes were generated by combined partial melting of a range of delaminating lower crustal lithologies with pyroxene and amphibole and the surrounding peridotites. Their melting was facilitated by the influx of H2O that was released from amphibole breakdown at high pressures. The amount of magma that was erupted along the Sredinny Range during the Late Quaternary can be produced by delamination of at least 7 vol.% of its crust. The proposed mechanism of delamination-induced melting may be involved in magma generation in other back-arc settings with a thick crust, such as back-arc regions of the Andean-type convergent margins and some active intra-oceanic back-arcs.

Funding

Australian Research Council

AMIRA International Ltd

ARC C of E Industry Partner $ to be allocated

Anglo American Exploration Philippines Inc

AngloGold Ashanti Australia Limited

Australian National University

BHP Billiton Ltd

Barrick (Australia Pacific) PTY Limited

CSIRO Earth Science & Resource Engineering

Mineral Resources Tasmania

Minerals Council of Australia

Newcrest Mining Limited

Newmont Australia Ltd

Oz Minerals Australia Limited

Rio Tinto Exploration

St Barbara Limited

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd

History

Publication title

Contributions to Mineralogy and Petrology

Volume

176

Issue

9

Article number

71

Number

71

Pagination

1-20

ISSN

0010-7999

Department/School

School of Natural Sciences

Publisher

Springer-Verlag

Place of publication

175 Fifth Ave, New York, USA, Ny, 10010

Rights statement

© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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