On the Genesis of the Sangasho-Type"Kieslager" as Related to Diabases

A Geochemical Study(1)

Abstract

In the Sangasho district, Miyazaki Prefecture, there are a number of diabase sheets or flows in the Paleozoic strata of geosynclinal deposition. These diabases have an areal extention and behave like the country rock of the "Kieslager".
This paper describes the relationships between the mineralization and alteration of the wall rocks, and the distribution of the major chemical elements in the altered diabases, on the basis of distance from the ore bodies. The features of the alteration seem to support the following conclusions.
(1) As a result of autometamorphism of the basaltic diabase in the course of cooling, it became the green rock which is characterized by amphibole, chlorite, zoisite, and albite and later the hematitized chlorite diabase by some hydrothermal solutions.
(2) There is some possibility that the "Kieslager"of the Sangasho-type might have been deposited by a hot spring(containing gas)on the floor of an oceanic basin or geosyncline, just after the submarine eruption of the diabase.