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The Kosaka mine consists of the Motoyama, Uchinotai, and Uwamuki Kuroko ore deposits. Using the Uchinotai and parts of the Uwamuki deposits, this paper shows that a thorough investigation of the morphology of the deposits through cross sectional analyses can demonstrate that the orebodies have undergone a considerable degree of deformation since their creation.

The causes of deformation include doming of underlying rhyolites, which occurred prior to and continued after the ore-forming episode, and the intrusion of dacite sheets into previously formed orebodies. Doming caused the ore, lying between the rhyolite and overlying sediments, to move by gravity slumping down the flanks of the rhyolite. The intrusion of dacite sheets caused the ore to be laterally transported or to undergo folding.

By compensating for the effects of deformation, the original configurations of the ore can be inferred. Such a reconstruction indicates that the ore initially formed on flat sea floor as a layered structure with a nearly horizontal upper surface.

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