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Ultra-high pressure minerals in the Luobusa Ophiolite, Tibet, and their tectonic implications

By
Paul T. Robinson
Paul T. Robinson
1
Department of Earth Sciences. The University of Hong Kong Pokfulam Road, Hong Kong, China probins@hkucc.hku.hk
2
Laboratory of Continental Dynamics, Institute of Geology, Chinese Academy of Geological Sciences Beijing, 100037, China
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Wen-Ji Bai
Wen-Ji Bai
2
Laboratory of Continental Dynamics, Institute of Geology, Chinese Academy of Geological Sciences Beijing, 100037, China
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John Malpas
John Malpas
1
Department of Earth Sciences. The University of Hong Kong Pokfulam Road, Hong Kong, China probins@hkucc.hku.hk
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Jing-Sui Yang
Jing-Sui Yang
2
Laboratory of Continental Dynamics, Institute of Geology, Chinese Academy of Geological Sciences Beijing, 100037, China
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Mei-Fu Zhou
Mei-Fu Zhou
1
Department of Earth Sciences. The University of Hong Kong Pokfulam Road, Hong Kong, China probins@hkucc.hku.hk
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Qing-Song Fang
Qing-Song Fang
2
Laboratory of Continental Dynamics, Institute of Geology, Chinese Academy of Geological Sciences Beijing, 100037, China
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Xu-Feng Hu
Xu-Feng Hu
3
Department of Chemistry, Dalhousie University Halifax, Nova Scotia, Canada
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Stanley Cameron
Stanley Cameron
4
Department of Earth Sciences, Dalhousie University Halifax, Nova Scotia, Canada B3H 3J5
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Hubert Staudigel
Hubert Staudigel
5
Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0225, USA
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Published:
January 01, 2004

Abstract

Numerous ultra-high-pressure minerals have been recovered from podiform chromities in the Luobusa ophiolite, Tibet. Recovered minerals include diamond, moissanite, Fe-silicides, wüstite, Ni–Fe–Cr–C alloys, PGE alloys and octahedral Mg–Fe silicates. These are accompanied by a variety of native elements, including Si, Fe, Ni, Cr and graphite. All of the minerals were hand-picked from heavy-mineral separates of the chromitites and care was taken to prevent natural or anthropogenic contamination of the samples. Many of the minerals and alloys are either enclosed in, or attached to, chromite grains, leaving no doubt as to their provenance. The ophiolite formed originally at a mid-ocean ridge (MOR) spreading centre at 177±33 Ma, and was later modified by suprasubduction zone magmatism at about 126 Ma. The chromitites were formed in the suprasubduction zone environment from boninitic melts reacting with the host peridotites. The UHP minerals are believed to have been transported from the lower mantle by a plume and incorporated in the ophiolite during seafloor spreading at 176 Ma. Blocks of the mantle containing the UHP minerals were presumably picked up by the later boninitic melts, transported to shallow depth and incorporated in the chromitites during crystallization.

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Contents

Geological Society, London, Special Publications

Aspects of the Tectonic Evolution of China

J. Malpas
J. Malpas
The University of Hong Kong, Hong Kong
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C. J. N. Fletcher
C. J. N. Fletcher
The University of Hong Kong, Hong Kong
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J. R. Ali
J. R. Ali
The University of Hong Kong, Hong Kong
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J. C. Aitchison
J. C. Aitchison
The University of Hong Kong, Hong Kong
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Geological Society of London
Volume
226
ISBN electronic:
9781862394742
Publication date:
January 01, 2004

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