Properties and Occurrences of Rock Coatings in Jeli, Kelantan As A Record of Environmental Processes

Abstract

Rock coatings can be defined as a product material deposition from surroundings. It is resulted from the wide variety of reactions which occur at the interface between the lithosphere and the biosphere. The coatings are biochemically and mineralogically complex and have the potential to record changes in their immediate environment. The changing of the coating gives information about the factors involved during the process which include dissolution and chemical reaction. The range of their activities and their proper significance in the environment as well as their relationship with the microorganisms that inhibit rocks and minerals provide a lot of information of the process involved. Types of coatings that have been identified on the outcrops around Kampung Kalai, Jeli are case hardening, iron film, dust film, rock varnish and lithobiontic coatings. The environmental exposures and inputs to the coatings, determines the coating mineralogy that formed on the parent rock. Scanning Electron Microscope (SEM) was used to analyse the microscopic properties of the coating samples. The presence of iron oxides have been found on the brick orange coating which potentially occurred from chemical weathering such as oxidation and the leaching of iron-bearing minerals. Besides that, geochemical analyses using X-Ray Fluorescence (XRF) on selected samples have shown limited information about the changing elemental composition. Iron, aluminium and silica are the major elements composition in the rock coatings reflecting the similar elemental composition of the existing parent rock.