Geology, Ore Deposits and Prospecting of the Tsumo Mine

Abstract

The Tsumo Mine, one of the pyrometasomatic Cu-Pb-Zn deposits, is in the inner zone of the south-western Japan.
In this paper, we report the outline of geology, ore deposits, and the prospecting program and its result.
The geology consists of Palaeozoic sediments, (slate, sandstone, quartzite, limestone and green rocks in ascending order), and late Cretaceous or early Tertiary acidic igneous rocks.
The Palaeozoic formations cover the main part of the area, generally forming an anticlinorium with low angle NE plunge, and with complicated structures, by minor folds and faults.
Main igneous rocks are acidic effusive rocks, spreading over the SE part of the area, and the Masago-granitic complex, intruding into the core of the main anticline or along the fault zones.
A favorable conditions for mineralarization were considered to be the superposition of followings :
1) Presence of calecareous beds (banded or transitional facies).
2) Complicated folding area of the favorable beds (cross fold).
3) High density area of fissure systems.
4) A vicinity of the Masago-granitic complex (especially, fractured acidic dykes).