Bulletin of the Geological Society of Malaysia, Volume 11, Dec, 1979, pp. 267 – 281
Dept. of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
Abstract: The tin-tungsten deposits of the Mae Lama mining district are closely associated with the Late Cretaceous(?) Mae Lama “Granite” (adamellite in composition). The mineralization occurs mainly in a hydrothermal quartz vein system, also in pegmatite and disseminated in the adamellite itself. The ore deposits are found within the contact zone of the adamellite and the adjacent Cambrian-Ordovician sedimentary/metasedimentary rocks which include sandstone, shale, laminated limestone, phyllite, slate and marble. Six productive cassiterite-wolframite-scheelite mines exist.
The alignments of the mineralized quartz veins and pegmatites are controlled mainly by one coherent fracture system striking east-west and north-south. The mineral assemblages include high temperature minerals such as cassiterite, wolframite, scheelite, arsenopyrite, pyrite, pyrrhotite, sphalerite, and chalcopyrite, and also lower temperature hydrothermal minerals such as native bismuth, bismuthinite and fluorite. Geothermometry, using the methods of solid solubility of Mg in calcite, amounts of As in arsenopyrite, and fluid inclusions in quartz, calcite and fluorite, indicates temperatures of mineralization from 100°C to 475°C. Both the adamellite stock and the ore bodies show greisenization.