The Formation of Yanshanian Granitic Magma in Dabie Mountains: Dehydration or Aquifer Melting -with Tiantangzhai and Jiuzihe Granites as Examples

There are large-areas of late Yanshanian granites in the Dabie Orogen, but the formation mode of the relevant granitic magma is still under discussion. Taking the typical Yanshanian granites in the North Dabie Block - The TG and JG as examples, the Writers endeavor to discuss contain aspects of the formation mode of the granitic magma by studying the characteristics of the chemical compositions of biotite and amphibole of the granites and petrological features of enclaves in the intrusions, in the light of recent results of experimental petrology on dehydration melting and aquifer melting. It is suggested that: (1) Some biotites in the Tiantangzhai and the JGs and their enclaves were residual minerals; (2) Some of the amphiboles could be new-born minerals, and others, residual ones. (3) the banded bodies in granites were residuals of anatexis. (4) The TG and JG were formed by aquifer melting, and the South Dabie Block could be the important source region of water.