Abstract
The Ider Complex of the Tarbagatai Block in northwestern Mongolia is part of a Precambrian microcontinental terrane in the Central Asian Orogen Belt and has experienced a polymetamorphic tectono-metamorphic evolution. We have investigated an enderbitic gneiss, derived from a quartz diorite and a charnockite, derived from a leucogranite, and zircon SHRIMP data reveal late Archaean protolith ages of 2520–2546Ma for these rocks. Metamorphic overgrowth on these zircons as well as newly-formed metamorphic zircons document a high-temperature metamorphic event (T=930–950°C) at about 1855–1860Ma. Nd whole-rock isotopic systematics show these and other gneisses of the Ider Complex straddling the CHUR-line in a Nd isotope evolution diagram, suggesting both crustal reworking and input of some juvenile material, with Nd model ages ranging between ca. 2.5 and 3.1Ga. Hf-in-zircon isotopic data provide a similar pattern and also yielded Archaean Hf crustal model ages. The metamorphic zircons seem to have inherited their Hf isotopic composition from the igneous grains, suggesting a complex process of dissolution, transportation, and re-precipitation involving a fluid phase during high-grade metamorphism. The zircon age patterns do not make it possible to unambiguously assign the Tarbagatai Block to any of the cratons bordering the Central Asian Orogenic Belt, since age peaks at ca. 2520–2550 and ca. 1860Ma are common in the Siberian, North China and Tarim cratons.
Highlights
The Dzabkhan microcontinent was defined by [Mossakovsky et al, 1994] as a cratonic terrane with an early Precambrian basement that combines highgrade metamorphic complexes of the Songino, Dzabkhan, Otgon, Baidarik, Ider and Jargalant Blocks
Moderateand high-Ti basalts of the volcanogenic sequences are comparable to modern N-MORB and E-MORB-OIB oceanic rocks, whereas a differentiated basalt-andesiterhyolite volcanic sequence and associated clastic sediments are interpreted as analogues of modern island arcs and accretionary wedges [Kovach et al, 2013; Yarmolyuk et al, 2015]
The northwestern part of the Dzabkhan block is composed of three zones, which differ in rock associations and their structural-metamorphic evolution [Kozakov et al, 2014]
Summary
The Dzabkhan microcontinent was defined by [Mossakovsky et al, 1994] as a cratonic terrane with an early Precambrian basement that combines highgrade metamorphic complexes of the Songino, Dzabkhan, Otgon, Baidarik, Ider and Jargalant Blocks. For citation: Kovach V.P., Kozakov I.K., Kröner A., Salnikova E.B., Wang K.-L., Lee H.-Y., Chung S.-L., 2017.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
