Zircon ages and Nd–Hf isotopes in UHT granulites of the Ider Complex: A cratonic terrane within the Central Asian Orogenic Belt in NW Mongolia
作者： A. Kröner , V.P. Kovach , I.K. Kozakov , T. Kirnozova , P. Azimov
关键词: Gneiss 、 Protolith 、 Leucogranite 、 Zircon 、 Granulite 、 Geochemistry 、 Metamorphism 、 Charnockite 、 Terrane 、 Geology
摘要: Abstract The Ider Complex of the Tarbagatai Block in northwestern Mongolia is part a Precambrian microcontinental terrane Central Asian Orogen Belt and has experienced polymetamorphic tectono-metamorphic evolution. We have investigated an enderbitic gneiss, derived from quartz diorite charnockite, leucogranite, zircon SHRIMP data reveal late Archaean protolith ages 2520–2546 Ma for these rocks. Metamorphic overgrowth on zircons as well newly-formed metamorphic document high-temperature event (T = 930–950 °C) at about 1855–1860 Ma. Nd whole-rock isotopic systematics show other gneisses straddling CHUR-line isotope evolution diagram, suggesting both crustal reworking input some juvenile material, with model ranging between ca. 2.5 3.1 Ga. Hf-in-zircon provide similar pattern also yielded Hf ages. seem to inherited their composition igneous grains, complex process dissolution, transportation, re-precipitation involving fluid phase during high-grade metamorphism. age patterns do not make it possible unambiguously assign any cratons bordering Orogenic Belt, since peaks 2520–2550 1860 Ma are common Siberian, North China Tarim cratons.
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