Perpustakaan Digital ITB

Nanggroe Aceh Darussalam Province is located in the Northern part of Sumatera, Indonesia, which occur as a product of subduction between Indo-Australia plate and Eurasian plate. This subduction causing numerous economical prospects, such as Fe-skarn prospect in Lhoong districts, Aceh. Skarn is defined as a lime-bearing silicate derived from nearly pure limestone and dolomite with the large amount of silicon, aluminium, iron and magnesium. The purpose of this research is to define the mineralogical characteristic of Lhoong prospect, using petrography and mineragraphy analysis from the outcrop, float samples that has been collected during the geological mapping. Lhoong prospect was covered by granodiorite Geunteut Formation in the North-Western and Eastern part of Lhoong area. The contact of granodiorite and limestone in the area of study was defined as a Fe-skarn. The area of study was dominated by the intrusive rocks, moderately altered rock, and also consists of metamorphic rocks that occur as a product of contact between ore minerals and carbonaceous rock. From the geological mapping, the mineralization occured as a fracture filling in intrusive rock, but the continuity of vein can’t be observed because of dense vegetation, weathered samples, that has been altered moderately into strongly oxidized. From the mineralogical observation, samples contains copper minerals, such as malachite, azurite, chalcopyrite, pyrite; ferrous minerals such as magnetite, ilmenite and hematite; and calcite, quartz, plagioclase, muscovite, chlorite, epidote, garnet, and pyroxene as gangue minerals. In the other samples, chlorite, rutile and titano-magnetite was defined, as a product of chloritization and propylitization, defined from the altered samples. The metamorphic rock was inter-laminary with thin veinlets that associated with diopside-pyroxene. Magnetite veinlets mostly occur in diorite and granodiorite rocks, and mineralized as filling mineral into intrusive rock. The presence of rutile shows the potential indicator for the metamorphosed metallic ore deposits, and persistent in weathering zone, that occured from samples taken in contact with carbonaceous rocks.