[S-MP21] Oceanic and Continental Subduction Processes: petrologic and geochemical perspective

[SMP21-P04] Early Neoproterozoic granitoids in the Ereendavaa block, NE Mongolia: A correspondence with Precambrian blocks in the Central Asian Orogenic Belt

*Munkhdelger BOLD¹, Yasuhito OSANAI², Nobuhiko NAKANO², Tatsuro ADACHI², Tatsuki TSUJIMORI^1,3, Otgonbayar DANDAR^4,5, Manzshir BAYARBOLD^4,5, Dolzodmaa BOLDBAATAR⁶ (1.Department of Earth Science, Graduate School of Science, Tohoku University, 2.Division of Earth Sciences, Faculty of Social and Cultural Studies, Kyushu University, 3.Center for Northeast Asian Studies, Tohoku University, 4.Graduate School of Environmental Studies, Tohoku University, 5.Geoscience Center, Mongolian University of Science and Technology, 6.Department of Mineral Processing and Engineering, School of Geology and Mining, Mongolian University of Science and Technology)

Keywords:Precambrian, granitoids, Ereendavaa, CAOB, zircon U–Pb dating

The Central Asian Orogenic Belt (CAOB), situated between the Siberian, North China, and Tarim Cratons, represents a remarkable orogenic belt with a long-lived and well-constrained crustal evolution. However, unraveling its Precambrian history poses challenges due to the scarcity of preserved crustal fragments. Microcontinents in the central to eastern CAOB, notably in Mongolia, have been recognized and studied, revealing their Precambrian basements, metasedimentary rocks, and magmatic intrusions. In particular, microcontinents in central CAOB (western Mongolia) are relatively well-constrained using reliable dating methods. The Ereendavaa block (EDB) in eastern CAOB (NE Mongolia) has recently reported Precambrian metasedimentary rocks, providing valuable insights into its evolution. Yet, understanding its Precambrian magmatic intrusions, crucial for deciphering crustal growth, remains challenging. In this study, therefore, we examine two feasible Precambrian granitic exposures in the EDB mapped as Paleozoic (Cambrian and Carboniferous). Through petrological, geochronological, and geochemical analyses, we determine the age and petrogenesis of these two granitic exposures, aiming to contribute to the understanding of their tectonic affinity during the Precambrian crustal evolution. The first granitic exposure consists of small boulders and is distributed over a relatively wider area compared to the second granitic exposure, which occurs as a lens within a Carboniferous granitic outcrop. The first granitic sample consists of plagioclase, K–feldspar, quartz, biotite, and accessory minerals, whereas the second granitic sample is composed mainly of plagioclase and quartz, with a minor amount of K–feldspar, biotite, and accessory minerals. Age and petrogenesis results reveal that both exposures are early Neoproterozoic granites (~880 Ma) in the EDB, exhibiting collision-related S-type affinity. Comparisons between the EDB and microcontinents in the CAOB highlight similarities in ages and geochemical traits, suggesting solely the possibility of an extension of the Erguna block. The study also suggests a potential proximity between the EDB and the Siberian Craton, rather than the Tarim Craton, based on the presence of similar granite types and coeval ages.