Abstract
Mg, Mn and Fe contents of biotites from the Cretaceous Hiroshima Granite are determined. The Cretaceous Hiroshima Granite is very homogeneous under the microscope. But, Mn/Mg and Mn/Fe ratios of biotite are various. Biotite in granite which was intruded into the palaeozoic formation rich in Mn-ore deposites has higher Mn/Mg (0.14-0.72) and Mn/Fe (0.024-0.052) ratios, on the other hand, biotite in granite which was intruded into the palaeozoic formation poor in Mn-ore has lower Mn/Mg (0.06-0.38) and Mn/Fe (0.013-0.030) ratios. This difference does not be attributed to the crystallization differentiation. There must be a interaction between the granitic magma and the palaeozoic formation. This interaction may not be negligible when we consider the Granite Problem.
