Petrography and Alteration of Pemali Region, Bangka District.

Abstract

The objective of this reasearch is to study the petrographic and alteration characteristic of the granitoid, metamorphic and sedimentary rocks of the Pemali area and to study the process of granite formation associated with primary tin deposits. This was done because no detailed petrographic and alteration analysis had been carried out in the Pemali area and the genesis of tin granite carriers in the Pemali area had not been concluded.The methodology used in this research are mineralogy and rock texture analysis. For the analysis, we can conclude that the rocks of the Pemali area consist of seven types of granitoid i.e. granodiorite, monzonite, quartz monzonite, granite, deformed granite, milonite granite, quartz veins + alkali feldspar +sulphide minerals, and one metamorphic rock in the form of phyllite and one sedimentary rock in the form of altered shale. Pemali granite has a granite character that is mixed between types I and S. Type I granite is characterized by the presence of hornblend, biotite, and titanite, while S type granite is characterized by the presence of biotite, muscovite and monazite with Sn-W element associations. Based on the secondary texture, the Pemali granitoid has been deformed twice with evidence of deformation including; mortar texture, milonite texture and fault breccia. The alteration process by hydrothermal solution produces an alteration zone in the form of a endogreisen, endoskarn, potassium , propylitic, argillic and advanced argilic. Based on Smirnov (1977) the types of primary tin deposits include cassiterite sulfide, quartz-cassiterite vein and sulphide cassiterite – skarn. Other metal deposits in the form of sulfide minerals, iron minerals, and REE such as xenotime.