1982 Volume 32 Issue 171 Pages 73-76
Cretaceous granitoids distributed around the Akenobe mine area have received pervasive propylitic alteration at many places. Unaltered granites of the Wadayama and Hikihara plutons, which belong to the ilmenite-series and are considered to be the related granite to the Cu-Sn stage mineralization of the Akenobe tinpolymetallic vein deposits, contain an average of 6.0 ppm Sn: whereas the altered granites have only 1.7 ppm Sn in the average. This result supports the model that the meteoric-water mixing leached out tin from the granitic rocks, and the then-formed ore solution was brought up to the site of the Akenobe ore deposits (ISHIHARA et al., 1981). The magnetite-series granitoids (the Shiso granitic complex) distributed to the southwest of the Akenobe mine are always low in tin. This tendency is observed elsewhere in the magnetite-series granitic terrains in Japan (ISHIHARA and TERASHIMA, 1977). These granitoids should not be considered related to the tin mineralization.
