Restitic ultramafic rocks in the Early Caledonian collisional system of western Cisbaikalia

Мехоношин, А. С.; Владимиров, А. Г.; Владимиров, В. Г.; Волкова, Н. И.; Колотилина, Т. Б.; Михеев, Е. И.; Травин, А. В.; Yudin, D. S.; Хлестов, В. В.; Хромых, С. В.

doi:10.1016/j.rgg.2013.09.007

Cited by 17 publications

(21 citation statements)

References 13 publications

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“…Характерной особенностью Чернорудской гра-нулитовой зоны является ее насыщенность на со-временном эрозионном срезе многочисленными телами, сложенными габброидами и пироксенита-ми [Mekhonoshin et al, 2001[Mekhonoshin et al, , 2013Fedorovsky et al, 2005Fedorovsky et al, , 2014Khromykh, 2006;Vladimirov et al, 2016a], которых насчитывается более 150 на всем протя-жении зоны (рис. 4).…”

Section: синметаморфические габброиды и пироксенитыunclassified

Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt

Yarmolyuk

Kuzmin

Ernst

2014

Journal of Asian Earth Sciences

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Abstract:In the Chernorud granulite zone in the Olkhon region of West Pribaikalie, we studied gabbro-pyroxenites composing tectonic plates (Chernorud, Tonta) and synmetamorphic intrusive bodies (Ulan-Khargana), as well as numerous disintegrated boudins and inclusions embedded in the metamorphic matrix. Based on the results of comparative analysis of the chemical compositions, the gabbro-pyroxenites are classified into a single island-arc tholeiitic series. The COMAGMAT software was used to simulate this series and to estimate the initial composition of the parent magma (magnesian basalt: SiO2=46.0 wt. %, TiO2=0.8 wt. %, Al2O3=15.3 wt. %, ΣFeO=9.0 wt. %, MnO=0.15 wt. %, MgO=10.5 wt. %, CaO=17.0 wt. %, Na2O=1.0 wt. %, K2O=0.2 wt. %, P2O5=0.05 wt. %, total = 100.0 %, Mg# = 67.5 %). It is concluded that the granulite metamorphism (P=7.7 to 8.6 kbar, T=770 to 820 °C) was due not only to dipping of the initial sedimentary-volcanic series to a depth of 25-28 km, but also to the presence of a deep chamber of magnesian basalt magma. In our estimations, garnet-pyroxenites (i.e. mafic rocks of the top facies in the above-mentioned chamber) originated at P=8.0-8.3 kbar and T=900-930 °C. Considering petrology, the deep mafic chamber under the layer of granulite facies is evidenced by metamorphic magma mingling, as well as pipe-shaped intrusions characterized by the specific morphology, internal structure and bulk rock compositions. Based on the data on the Ulan-Khargana massif and gabbro-pyroxenite bodies involved in the structure of the marble melange, we propose a petrological model showing two stages of mafic injection -Stage 1: hydraulic fracturing of granulite series and the emergence of tubular structures and bodies, which are similar to kimberlite pipes or channels of different shapes; Stage 2: rising of the fluidized residual alkaline melt through the emerging 'pipes' and fractures armored by hardened zones, which is followed by metamorphic magma mingling under viscous deformation conditions. The mafic magmas intruding to the

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Section: синметаморфические габброиды и пироксенитыunclassified

Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt

Yarmolyuk

Kuzmin

Ernst

2014

Journal of Asian Earth Sciences

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“…The latter are dunite or harzburgite, with a minor amount of wehrlite, clinopyroxenite, and spinel-olivine-enstatite rocks. Several bodies are quite large and well exposed, including those described previously [23,24,39].…”

Section: Ultramafic and Mafic Rocks In The Olkhon Terranementioning

confidence: 63%

“…This is valid also for the Olkhon ophiolite. Although the ultramafic rocks were identified as ophiolite-type residual peridotite without much doubt [23], the presence of ophiolitic gabbros, sheeted dike complexes, and volcanics has been overlooked. The age and geodynamic constraints are available for only two complexes of the Krestovsky subterrane, out of countless gabbro bodies and blocks from a few tens of meters to a few km in size: the 500 Ma Birkhin gabbro with distinct suprasubduction fingerprints [25][26][27] and the 470 Ma Ust-Krestovsky complex of subalkaline gabbro which presumably resulted from interaction of a mantle plume with suprasubduction lithospheric mantle [26].…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The terrane consists of sedimentary and igneous complexes which differ in age and in the origin of protoliths [19] metamorphosed to amphibolite and granulite facies [20]. Numerous small ultramafic bodies found within the terrane, mainly dunite and harzburgite [21,22], are often interpreted as residual ophiolitic peridotites [23,24], while the presence of other possible members of an ophiolite suite remains questionable. The terrane also accommodates numerous compositionally diverse gabbros that were metamorphosed during collisional orogeny.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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.

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“…The blastomylonite zones are bounded laterally by detachment and bedding surfaces and the scallop-shaped fringes are seen along the strike direction. The above diagnostic indicators are common in other shear zones of brittle-ductile deformation (Mekhonoshin et al, 2013;Vladimirov et al, 2011).…”

Section: Geology and Strictiral Framework Of The Yenisei Ridge And Stmentioning

confidence: 94%

P-T-t reconstructions of South Yenisei Ridge metamorphic history (Siberian craton): petrological consequences and application to the supercontinental cycles

Лиханов

Ревердатто

Козлов

et al. 2015

Russian Geology and Geophysics

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Studies of gneisses from the Yenisei regional shear zone (YRSZ) provide the first evidence for Mesoproterozoic tectonic events in the geologic history of the South Yenisei Ridge and allowed the recognition of several stages of deformation and metamorphism spanning from Late Paleoproterozoic to Vendian. The first stage (~1.73 Ga), corresponding to the period of granulite-amphibolite metamorphism at P = 5.9 kbar and T = 635 °C, marks the final amalgamation of the Siberian craton to the Paleo-Mesoproterozoic Nuna supercontinent. During the second stage, corresponding to a hypothesized breakup of Nuna as a result of crustal extension, these rocks underwent Mesoproterozoic dynamic metamorphism (P = 7.4 kbar and T = 660 °C) with three peaks at 1.54, 1.38, and 1.25 Ga and the formation of high-pressure blastomylonite rocks in shear zones. Late-stage deformations during the Mesoproterozoic tectonic activity in the region, related to the Grenville-age collision processes and assembly of Rodinia, took place at 1.17-1.03 Ga. The latest pulse of dynamic metamorphism (615-600 Ma) marks the final stage of the Neoproterozoic evolution of the Yenisei Ridge, which is associated with the accretion of island-arc terranes to the western margin of the Siberian craton. The overall duration of identified tectonothermal processes within the South Yenisei Ridge during the Riphean (~650 Ma) is correlated with the duration of geodynamic cycles in the supercontinent evolution. A similar succession and style of tectonothermal events in the history of both the southern and the northern parts of the Yenisei Ridge suggest that they evolved synchronously within a single structure over a prolonged time span (1385-600 Ma). New data on coeavl events identified on the western margin of the Siberian craton contradict the hypothesis of a mantle activity lull (from 1.75 to 0.7 Ga) on the southwestern margins of the Siberian craton during the Precambrian. The synchronous sequence and similar style of tectonic events on the periphery of the large Precambrian Laurentia, Baltica, and Siberia cratons suggest their spatial proximity over a prolonged time span (1550-600 Ma). The above conclusion is consistent with the results of modern paleomagnetic reconstructions suggesting that these cratons represented the cores of Nuna and Rodinia within the above time interval.

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Restitic ultramafic rocks in the Early Caledonian collisional system of western Cisbaikalia

Cited by 17 publications

References 13 publications

Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt

Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt

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

P-T-t reconstructions of South Yenisei Ridge metamorphic history (Siberian craton): petrological consequences and application to the supercontinental cycles

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