Geology and Fe-Skarn Mineralization in Lolo Prospect, Solok West Sumatra, Indonesia

The study area is situated in Lolo village, Pantai Cermin district, Solok regency, West Sumatra province, Indonesia. Several mining companies have been operated for skarn-related iron ore type in this area and its vicinity. Although the study area has been explored, the detailed geology and Fe skarn characteristics remain unclear. This paper therefore, is dealing with the geological framework and characteristics of skarn mineralogy employing some laboratory analyses such as petrography, ore microscopy, X-Ray Diffraction, micro-XRF and AMICS, ICP-AES and ICP-MS analyses. The geological framework of the prospect was defined by a surface geological mapping and observation. Skarn alteration of limestone host-rock is typified by the presence of prograde minerals such as garnet, clinopyroxene, and wollastonite. The retrograde mineral is peculiarly not found in the limestone wall-rock, but in altered causative intrusion i.e. granodiorite. The altered granodiorite is composed of some key propylitic minerals such as chlorite, epidote, and a few clay minerals. Fe skarn mineralization is represented in magnetite, hematite, goethite and limonite which are associated with several sulphide minerals such as covellite, pyrite, and chalcopyrite. Mass balance analysis on limestone indicates a mass gain of 0.16%, whereas mass balance analysis on granodiorite indicating mass loss of 3.36%. Ore mineralization and skarn alteration are strongly controlled by NW-SE and NE-SW trending faults and the distribution of limestone. Follow-up subsurface exploration is needed to define the Fe skarn orebody.