An early Paleozoic tectonothermal event in western Mongolia: Implications for regional extension of the Cambrian orogenic belt

The Central Asian Orogenic Belt consists of various terranes amalgamated in several periods from the Late Precambrian/ Early Paleozoic to the Late Mesozoic. Mongolia is situated in the center of this belt. Foliated garnet granite (Grt metagranite) and andalusite-bearing massive leucogranite (Leucogranite) are exposed in the Hanhohiyn region of northwest Mongolia. The results of monazite Th-U-Pb dating of the Grt metagranite and Leucogranite give ages of 508 ± 10 Ma and 496 ± 4 Ma, respectively. Cambrian granite with an age of ~ 500 Ma is also reported from the south-central part of Mongolia. Combined with previously published age data of metamorphic and intrusive rocks, these results show that the Cambrian orogenic belt spans over 800 km, from the northwest to the south-central part of Mongolia.