Geological, Mineralogical and fluid inclusion studies of antimony3gold mineralization at Tambon Chae Sorn, King Amphore Muang Pan, Changwat Lampang

Abstract

The Case Sorn Antimony-Gold mineralization occurs in an old shear zone lying between metasediment unit and clastic nit. The mineralization post-dated shearing. At least four stages of mineralization has been recognized in which the first two stages are preore stage, namely ; minor galena-sphalerite-ferroan dolomite (stage I), and minor arsenopyrite-pyrite-quartz (stage II). The later two stages are stibnite mineralizing episodes, namely ; the early-stibnite-quartz (stage III) and the late stibnite-quartz (stage IV) mineralization. All these four stages are characterized mainly by open space filling texture in the forms of veins and/or veinlets, vug-filling and breccia-filling. Gold in Chae Sorn most probably occurs as fine particle associated with sulfide minerals possibly arsenopyrite of stage II mineralization. Silicification is widely distributed wall rock alteration in Chae Sorn area with inor phyllic alteration. The major silicification was found to accompany the major fracturing and brecciation in the mineralized zone which occurred prior to stage III mineralization. Flid inclusion study from stage I sphalerite and stage IV quartz show that all the primary and pseudosecondary inclusions are simple liquid-rich type with approximately constant liquid/vapor ratio. The filling temperatures of stage I sphalerite vary from 190-250℃. The stage I seems to show somewhat higher temperature than those of the stage IV. These temperature ranges are expected in low temperature epithermal system of meteoric water origin.