Zircon LA-ICP-MS U-Pb age and tectonic significance of the garnet granites from Helin-Liangcheng zone of Central Inner Mongolia

Garnet granites in Helin-Liangchang zone of central Inner Mongolia are strongly peraluminous granites. The age of garnet granites obtained by zircon LA-ICP-MS U-Pb method is 1923-1958 Ma, indicating Paleoproterozoic. The analyses of their geochemical characteristics indicate that the source area was made up of graywackes, and the partial melting temperature was relatively high, suggesting post collision stage magmatite activity characteristics. Considering the regional geological features, the garnet granites should be the product of partial melted graywackes which existed at the bottom of the earth's crust, heated by the basaltic magma with high temperature under the relatively high temperature conditions (above 875℃). The melting happened when Yinshan block and Erduosi block collided in the early Paleoproterozoic and turned from convergence to extension, companied by the underplating of basaltic magma.