Back to Search Start Over

Cambrian–Ordovician magmatism of the Ikh-Mongol Arc System exemplified by the Khantaishir Magmatic Complex (Lake Zone, south–central Mongolia)

Cambrian–Ordovician magmatism of the Ikh-Mongol Arc System exemplified by the Khantaishir Magmatic Complex (Lake Zone, south–central Mongolia)

Authors :
Vojtěch Janoušek
Karel Schulmann
Yingde Jiang
Igor Soejono
Vojtěch Erban
Jan Košler
Battushig Altanbaatar
Ondrej Lexa
Turbat Ganchuluun
Alfred Kröner
David Buriánek
Pavel Hanžl
Dynamique de la lithosphère et des bassins sédimentaires (IPGS) (IPGS-Dylbas)
Institut de physique du globe de Strasbourg (IPGS)
Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)
Institut für Geowissenschaften [Mainz]
Johannes Gutenberg - Universität Mainz (JGU)
Institute of Petrology and Structural geology
Charles University [Prague] (CU)
Source :
Gondwana Research, Gondwana Research, Elsevier, 2018, 54, pp.122-149. ⟨10.1016/j.gr.2017.10.003⟩
Publication Year :
2018
Publisher :
HAL CCSD, 2018.

Abstract

The Khantaishir Magmatic Complex (KMC) (south–central Mongolia) exposes a section of a magmatic system consisting of deep crustal, ultramafic cumulates (coarse-grained Amp gabbros and hornblendites; c. 0.35–0.5 GPa) to shallower crustal levels dominated by Amp–Bt tonalites ( c. 0.1–0.2 GPa). The magmatic rocks were emplaced during most of the Cambrian ( c. 538–495 Ma) and are mostly geochemically primitive (Mg# ~ 50), Na-rich and metaluminous. The (normal-) calc-alkaline signature and characteristic trace-element enrichment in hydrous-fluid mobile large-ion lithophile elements (LILE) relative to high-field strength elements (HFSE) suggest an origin within a magmatic arc. Multiple intrusions of basic magma derived from a subduction-modified depleted mantle developed by fractional crystallization and/or accumulation of (Ol, Cpx) Amp + Bt, later joined by Pl. Magma mixing with, or without, exchange of xenocrysts between compositionally dissimilar melt batches was also important. Over time, partial melting of older, lower crustal metabasic rocks became increasingly significant, again with a strong subduction signature. The lack of zircon inheritance in the magmatic products and rather high zircon e Hf t values (all >+3, but for most samples > +8) as well as whole-rock Sr–Nd isotopic compositions imply that the arc was not founded on mature continental crust. It was probably located at the margin of the Baydrag microcontinent, dominated by accreted metabasic rocks of an older (early Tonian?) island arc covered by a thin layer of subordinate metasediments containing detrital zircons with Tonian and ill-defined Palaeoproterozoic ages. The KMC represents a small vestige of an extensive Cambrian–Ordovician subduction system (termed here the Ikh-Mongol Arc System), bordering the western margin of a chain of Precambrian microcontinents (Tuva-Mongolia, Zabkhan and Baydrag) that, together with accreted Neoproterozoic marginal basins (the Lake Zone), defines the external part of the Mongolian orocline.

Details

Language :
English
ISSN :
1342937X
Database :
OpenAIRE
Journal :
Gondwana Research, Gondwana Research, Elsevier, 2018, 54, pp.122-149. ⟨10.1016/j.gr.2017.10.003⟩
Accession number :
edsair.doi.dedup.....bcbd4b1d482f252d19d8c483b1aecf05
Full Text :
https://doi.org/10.1016/j.gr.2017.10.003⟩