Stable Isotopes, Minor Elements and Diagenetic Alteration Associated with Tono Sandstone-Type Uranium Deposits in Japan

Abstract

Sandstone-type uranium deposits are the most important uranium producers among various types of uranium deposits. Geologic setting and diagenetic alteration mineralogy of this type of deposits have been well documented. The genesis of sandstone-type uranium deposits have been argued based on geologic and mineralogic studies (Nash et al., 1981). However, it is essentially important to estimate chemical features (Eh, pH) and isotopic compositions of fluids responsible for uranium mineralization and associated diagenetic alteration in order to elucidate genesis of the uranium deposits and diagenetic alteration mechanism. A few such geochemical studies on the sandstone-type deposits have been carried out. In this study, the geochemical features of the diagenetic alteration in the Tone mine area are used to provide constraints on the relationship between uranium mineralization and diagenetic alteration process and the estimation of chemical environments responsible for uranium mineralization.