Geochemistry and Origin of the Eastern Sayan Ophiolites, Tuva-Mongolian Microcontinent (Southern Siberia)

Belyaev, V. A.; Wang, Kuo‐Lung; Gornova, M. A.; Dril, S. I.; Karimov, A.A.; Medvedev, A.Ya.; Noskova, Yu. V.

doi:10.5800/gt-2017-8-3-0250

Cited by 6 publications

(8 citation statements)

References 18 publications

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“…The lava and dyke complex chemically resemble the rocks of boninite and island-arc tholeiite series [43]. The presence of boninites is attributed to the Eastern Sayan ophiolites to suprasubduction ophiolites associated with Mariana-type subduction [44,45] and also indicates their proximity to forearc ophiolites, which are quite widespread within CAOB [37,46,47]. The regional metamorphism of the Irkut, Ilchir and Ospin formations corresponds to the conditions of greenschist facies [42].…”

Section: Khara-nur Metaperidotitesmentioning

confidence: 91%

In Situ Geochemical Evaluation of Retrograde Hydration Effects in the Peri-Siberian Forearc Mantle (Khara-Nur and Alag-Khadny Peridotite Complexes)

Karimov,

Gornova,

Belyaev

et al. 2024

Minerals

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In order to assess the geochemical effects of retrograde metamorphic rehydration, fluid metasomatism, and the fluid-mobile elements (FMEs) budget in the case of oceanic and continental subduction, we report the petrography, bulk, and in situ LA-ICP-MS trace-element data for the two poorly studied ophiolites in the northern (Khara-Nur, Eastern Sayan, Russia) and central (Alag-Khadny accretionary wedge, SW Mongolia) parts of the peri-Siberian orogenic framing. Both complexes are relics of the ancient oceanic mantle, which was subjected to processes of partial melting, metasomatism, and retrograde metamorphism. Typical mineral assemblages include olivine + orthopyroxene + chlorite + tremolite ± secondary olivine (640–800 °C), olivine + antigorite ± secondary clinopyroxene (<640 °C), and olivine + chrysotile ± secondary clinopyroxene (<250 °C) and are stable at pressures up to 2 GPa. Hydration and partial serpentinization of mantle peridotites lead to tremolite formation after orthopyroxene, followed by olivine replacement by antigorite. Serpentine-group minerals (antigorite and chrysotile) were distinguished by Raman spectroscopy, and the contents of incompatible elements (mobile and immobile in fluids) in metamorphic minerals (tremolite, antigorite, and chrysotile) were examined in situ by LA-ICP-MS. The behavior of conservative HFSE (Zr, Nb, Ta, and Ti) and—in part—HREE does not distinguish between the two types (oceanic and continental) of subduction environments. Different patterns of FMEs (Cs, Rb, Ba, U, Sb, Pb, Sr, and LREE) enrichment in metaperidotites reflect variations in the slab fluid composition, which was primarily governed by the contrasting nature of subducted lithologies. The affinity of Alag-Khadny to the subduction of a continental margin is recorded by increased FME contents and selective enrichment by some moderately mobile elements, such as U, Th, and LREE, with respect to the oceanic-type subduction environment of Khara-Nur. Distinct patterns of FME enrichment in tremolite and antigorite from two complexes indicate different sequences of fluid-induced replacement, which was controlled by Opx composition. We demonstrate that evaluation of the initial composition of precursor minerals affected by multi-stage melting and melt metasomatism should be considered with care to estimate the differential fluid overprint and associated elemental uptake from subduction fluids.

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Section: Khara-nur Metaperidotitesmentioning

confidence: 91%

In Situ Geochemical Evaluation of Retrograde Hydration Effects in the Peri-Siberian Forearc Mantle (Khara-Nur and Alag-Khadny Peridotite Complexes)

Karimov,

Gornova,

Belyaev

et al. 2024

Minerals

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“…They also preserve an igneous texture. All analyses yield close 206 Pb/ 238 U apparent ages of 829-840 Ma, with a weighted mean age of 833 ± 4.0 Ma (MSWD = 0.006, n = 18, Figure 16), which is interpreted as the crystallization age during the mature island-arc and intra-arc rifting stages [23,27,32].…”

Section: Zircon U-pb Datingmentioning

confidence: 99%

“…The island-arc geochemical affinities correspond to the suprasubduction setting [24,30,31]. Diabase sills and dikes intrude the ophiolite series [24,[30][31][32] covered by sedimentary rocks. They correspond to high-Ti/Fe/P subalkaline tholeiites.…”

Section: Introductionmentioning

confidence: 99%

“…Ediacaran-Cambrian platform sediments unconformably overlie this sequence. Therefore, the Shishkhid ophiolite was thrusted upon the Oka prism before the end of the Neoproterozoic time [32,36,37]. After the oceanic lithosphere of the basin, dividing the Sarkhoi and Shishkhid island arcs had been completely subducted, and the Shishkhid island arc was accreted to the Sarkhoi island arc.…”

Section: Introductionmentioning

confidence: 99%

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Multistage Magmatism in Ophiolites and Associated Metavolcanites of the Ulan-Sar’dag Mélange (East Sayan, Russia)

et al. 2020

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We present new whole-rock major and trace element, mineral chemistry, and U-Pb isotope data for the Ulan-Sar’dag mélange, including different lithostratigraphic units: Ophiolitic, mafic rocks and metavolcanites. The Ulan-Sar’dag mélange comprises of a seafloor and island-arc system of remnants of the Paleo-Asian ocean. Detailed studies on the magmatic rocks led to the discovery of a rock association that possesses differing geochemical signatures within the studied area. The Ulan-Sar’dag mélange includes blocks of mantle peridotite, podiform chromitite, cumulate rocks, deep-water siliceous chert, and metavolcanic rocks of the Ilchir suite. The ophiolitic unit shows overturned pseudostratigraphy. The nappe of mantle tectonites is thrusted over the volcanic-sedimentary sequence of the Ilchir suite. The metavolcanic series consist of basic, intermediate, and alkaline rocks. The mantle peridotite and cumulate rocks formed in a supra-subduction zone environment. The mafic and metavolcanic rocks belong to the following geochemical types: (1) Ensimatic island-arc boninites; (2) island-arc calc-alkaline andesitic basalts, andesites, and dacites; (3) tholeiitic basalts of mid-ocean ridges; and (4) oceanic island basalts. U–Pb dating of zircons from the trachyandesite, belonging to the second geochemical type, yielded a date of 833 ± 4 Ma which is interpreted as the crystallization age during mature island-arc and intra-arc rifting stages. The possible influence of later plume magmatic-hydrothermal activities led to the appearance of moderately alkaline igneous rocks (monzogabbro, trachybasalt, trachyandesite, subalkaline gabbro, and metasomatized peridotites) with a significant subduction geochemical fingerprint.

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“…Generally, geochemical signatures for the magmatic rocks associated with Eastern Sayan ophiolites reveal a wide compositional series: mid-ocean ridge basalt (MORB)-type basalts (tholeiites), boninites, island-arc andesites and dacites, and ocean island basalt (OIB)-type basite rocks. There are numerous isotopic data of the island arc assemblage and ophiolites in a different segment of CAOB, but isotope geochemical data of Proterozoic Eastern Sayan ophiolites are limited [4,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. [35,36].…”

Section: Introductionmentioning

confidence: 99%

Nd-Sr Isotopic Study of Magmatic Rocks and 40Ar/39Ar Dating of the Mafic Dike of the Proterozoic Ulan-Sar’dag Ophiolite Mélange (Southern Siberia, East Sayan, Middle Belt, Russia)

et al. 2022

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We report the first radiogenic Nd-Sr isotope data in the magmatic rocks island-arc ophiolite assemblage from the middle branch of the East Sayan ophiolite complexes to better constrain geodynamic processes in this segment of the CAOB in southern central Siberia. The magmatic rocks belong to the following geochemical types: (1) Ensimatic island-arc boninites; (2) island-arc assemblage; (3) enriched basalts of mid-ocean ridges; and (4) oceanic island-like basalts. The boninites have a positive value εNd (T), which is generated from a depleted mantle source (N-MORB). The island-arc assemblage has negative or slightly positive εNd (T) and was formed from an enriched mantle source due to the subduction of terrigenous rocks. The source of the terrigenous material was most likely the rocks of the Archean TTG (Trondhjemite Tonalite Granodiorite) complex of the Gargan block. Isotopic ratios for E-MOR and OIB-like basalts are characterized by positive or slightly negative values of εNd (T). The mafic dike, which crosscut ophiolite rocks, corresponds to OIB-like basalts. The values of εNd (T), measured 87Sr/86Sr and I (Sr), in the mafic dike correspond to the EM I mantle source. The E-MOR and OIB-like basalts appear to be formed in late-stage asthenospheric mantle melting via the decompression melting processes. The obtained isotope geochemical data for the E-MOR and OIB-like basalts probably indicate the mixing of island-arc melts with asthenospheric melts. We undertook 40Ar/39Ar dating of the mafic dike, which crosscut the ophiolite unit. The mafic dike has a whole-rock 40Ar/39Ar weighted mean plateau age of 799 ± 11 Ma. The dating constrains the minimum age of the ophiolite and island-arc magmatism in the region.

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Geochemistry and Origin of the Eastern Sayan Ophiolites, Tuva-Mongolian Microcontinent (Southern Siberia)

Cited by 6 publications

References 18 publications

In Situ Geochemical Evaluation of Retrograde Hydration Effects in the Peri-Siberian Forearc Mantle (Khara-Nur and Alag-Khadny Peridotite Complexes)

In Situ Geochemical Evaluation of Retrograde Hydration Effects in the Peri-Siberian Forearc Mantle (Khara-Nur and Alag-Khadny Peridotite Complexes)

Multistage Magmatism in Ophiolites and Associated Metavolcanites of the Ulan-Sar’dag Mélange (East Sayan, Russia)

Nd-Sr Isotopic Study of Magmatic Rocks and 40Ar/39Ar Dating of the Mafic Dike of the Proterozoic Ulan-Sar’dag Ophiolite Mélange (Southern Siberia, East Sayan, Middle Belt, Russia)

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