Abstract

The Pilok area, situated along the Thai-Burmese border, is one of the most productive tin-tungsten primary deposits in Thailand. The ore deposits occur predominantly as vein systems as well as localized carbonate replacement skarn. The environment of the deposit is post-tectonic within the plutonic arc-fold belt. The ore is closely and spatially associated with multiphased intrusions of 2-mica megacrystic granite, foliated granite, 2-mica equigranular non-foliated granite, 2-mica tourmaline-sulphide ore bearing fine-grained granite as well as aplites and greisenized granite. The age of the oldest intrusive phase (2-mica megacrystic foliated granite) is 93 ± 4 Ma with an initial 87Sr/86Sr ration of 0.738. The granites intruded discordantly into schist and quartzite of Middle Paleozoic age.

Ore deposits are mostly concentrated at the cusps and the contact zones between the granites and country rocks as well as along fault zones. Tin and tungsten commonly occur together in the vein system, whereas the stockworks and swarms of ore-bearing quartz veinlets contain mostly tin. Pyrite, pyrrhotite, molybdenite and fluorite sometimes are associated with tin-tungsten in the fault zone and contact skarn ores. Scheelite and molybdenite occasionally occur in the quartz-veins within the country rocks, whereas the tin-tungsten ore-bearing veins are limited to the granite along the contact zone.

 

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