Influence of contact metamorphism and Geofluid on Hirao Limestone

Abstract

Detailed outcrop observation of the Hirao limestone located in Kitakyushu city was conducted. There is clear trend that the grain size of the calcite coarsened by the contact metamorphism becomes larger as it is closer to the Hirao granodiorite which is considered as the heat source. In the northern part of surveyed area, there is a local grain growth region that does not match the surrounding grain size distribution and many veins consisting of coarse calcite are present. In this area, it is thought that local coarsening occurred due to the influence of crustal fluid.