Kind of Volcanic Rocks Related to Formation of the Black Ore Deposits, and Migration of Some Elements in the Volcanic Rocks during the Mineralization.

Abstract

The authors studied the volcanic rocks in the region of the Hanaoka Mine by means of microscopical examination and X-ray diffraction, and concluded that the earlier one is dacite and the latter one genetically related to formation of the black ore deposits is rhyolite.
Chemical analyses of the dacites near the Matsumine and Fukazawa ore deposits clearly revealed increase of Mg and K, and decrease of Na from fresh core toward altered periphery in the dacite bodies. Consequently the authors suggest that the addition of Mg and K were performed during the mineralization of the black ore deposits. The phenomena on Mg and K can be seen up to the point about 1, 000 m apart from Fukazawa ore deposits. It seems probable to apply the phenomena to the exploration of the black ore deposits.