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Article

Dismembered Ophiolite of the Olkhon Composite Terrane (Baikal, Russia): Petrology and Emplacement

1
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, 128 Lermontov st., 664033 Irkutsk, Russia
2
School of Engineering, Far East Federal University, 8 Sukhanov st., 690091 Vladivostok, Russia
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V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 Akad. Koptyuga st., 630090 Novosibirsk, Russia
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Department of Geology and Geophysics, Novosibirsk State University, 2 Pirogov st., 630090 Novosibirsk, Russia
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Geological Institute, Russian Academy of Sciences, Pyzhevsky per. 6, 119017 Moscow, Russia
6
A.N. Zavaritsky Institute of Geology and Geochemistry, Uralian Branch of the Russian Academy of Sciences, Akad. Vonsovsky st., 620016 Ekaterinburg, Russia
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(4), 305; https://doi.org/10.3390/min10040305
Received: 3 March 2020 / Revised: 27 March 2020 / Accepted: 28 March 2020 / Published: 30 March 2020
(This article belongs to the Special Issue Geology and Petrology of Ophiolites)
Dismembered ophiolites in the Early Paleozoic Olkhon terrane, a part of the Baikal collisional belt in the southern periphery of the Siberian craton, occur as fault-bounded blocks of ultramafic and mafic rocks from a few meters to hundreds of meters in size. The ultramafic rocks are mainly dunite–harzburgite peridotites with gradual transitions between the lithologies, as well as moderate amounts of enstatitite, wehrlite, and clinopyroxenite, but no lherzolite. Most peridotites have strongly depleted chemistry and a mineralogy corresponding to the harzburgite type usual for ophiolites of suprasubduction zones (SSZ). The mafic rocks are leuco- to melanocratic gabbros with different relative percentages of clinopyroxene, olivine, and plagioclase, which enclose thin layers and lenses of clinopyroxenite and anorthosite. They bear back-arc basin geochemical signatures, a setting inferred for the Neoproterozoic southern Siberian craton. The gabbroic rocks are of two geochemical groups; most of their trace-element patterns show Ta-Nb minimums and Sr maximums common to suprasubduction zone ophiolites. Judging by the Ol + Opx + Chl + Chr mineral assemblages, the Olkhon peridotites underwent low amphibolite and amphibolite regional metamorphism at 500–650 °C. The occurrence of the ultramafic and mafic bodies is consistent with formation in an accretionary wedge metamorphosed during a collisional orogeny. The mantle and crustal parts of the Olkhon ophiolite suite apparently were incorporated into the terrane during the frontal collision of perio-oceanic structures with the Siberian craton. Then, in a later oblique collision event, they became dismembered by strike-slip faulting into relatively small bodies and fault blocks exposed in the present erosional surface. View Full-Text
Keywords: ophiolite; ultramafic rocks; gabbro; amphibolite; petrology; CAOB; Olkhon terrane; collisional orogeny ophiolite; ultramafic rocks; gabbro; amphibolite; petrology; CAOB; Olkhon terrane; collisional orogeny
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MDPI and ACS Style

Sklyarov, E.V.; Lavrenchuk, A.V.; Fedorovsky, V.S.; Pushkarev, E.V.; Semenova, D.V.; Starikova, A.E. Dismembered Ophiolite of the Olkhon Composite Terrane (Baikal, Russia): Petrology and Emplacement. Minerals 2020, 10, 305. https://doi.org/10.3390/min10040305

AMA Style

Sklyarov EV, Lavrenchuk AV, Fedorovsky VS, Pushkarev EV, Semenova DV, Starikova AE. Dismembered Ophiolite of the Olkhon Composite Terrane (Baikal, Russia): Petrology and Emplacement. Minerals. 2020; 10(4):305. https://doi.org/10.3390/min10040305

Chicago/Turabian Style

Sklyarov, Eugene V., Angrey V. Lavrenchuk, Valentine S. Fedorovsky, Evgenii V. Pushkarev, Dina V. Semenova, and Anastasia E. Starikova 2020. "Dismembered Ophiolite of the Olkhon Composite Terrane (Baikal, Russia): Petrology and Emplacement" Minerals 10, no. 4: 305. https://doi.org/10.3390/min10040305

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