Geology and Zinc Ore Deposits of Pa-Daeng Area, Maesod District, Thailand

Abstract

The zinc deposits of Pa-daeng area consist of Main Ore Body sitting astride the mountain ridge like a saddle, 12 kilometers east-southeast of Maesod town and other minor outcrops scattered northwestward to an extent of 2, 700 meters. The chief constituent ore minerals of the former are smithsonite, calamine, hydrozincite and clay minerals changing to underlying country rocks at the depth of 10 to 50 meters from the surface, and no sulfide minerals are found. In some of the latter, however, outcrop of ore vein composed of sphalerite and galena was found, or drilling core rich in sphalerite was taken from the depth of several meters though the surface of the outcrop at the collar of the hole is entirely changed to carbonate and silicate of zinc.
The host rock of the deposits are mainly limestone and dolomite, but siliceous sandstone plays an important part in Main Ore Body. The deposits of secondary ore minerals immediately above the sulfides may mostly be oxidation products "in situ" type, but some amount of migration of oxidized ore constituents should have been taken place in the process of oxidation in Main Ore Body.
No igneous intrusives are known in the vicinity of several dozen kilometers, and the existence of zinc-lead deposits seems to be confined to the Mesozoic Kamawkala limestone which fringes the eastern boundary of Maesod basin.