Geology and petrographic analysis of volcanic product in Mandalawangi, Pandeglang Regency, Banten

This research is about geology and petrographic analysis of volcanic product in Mandalawangi, Pandeglang regency at Banten. The study area which is Mandalawangi is surrounding by four different volcanoes which are Mount Aseupan, Mount Pulosari, Mount Parakasak, and Mount Karang. The study area is lies on the caldera, this is the reason why the area consist a lot of volcano. Previous geological map of the study area were found in scale of 1:100,000 by Santosa, (1991 ).Through mapping and observation that has been made for this research, the scale of the map was increase to 1:25,000 and this mapping also has add more detail data of geological information such as geomorphology, lithology, and stratigraphy of the study area. The area of Mandalawangi is mainly covered by volcanic igneous rock which is Andesite unit and Tuff unit. This research also provided new information about the mineralogy and petrology of the study area. The analysis of the volcanic product has been done by petrography study of the thin section of sample to identify the mineralogy of the rock and also by using geochemistry analysis which is X-Ray Fluorescence (XRF) analysis in order to recognise the elemental composition in the sample of rock and to determine the sources of the rock by using TAS diagram. From the result and interpretation of petrographic analysis and geochemistry analysis, all of the samples were classified into Andesite rock unit. This analysis proved that the volcanic products of the study area were coming from the same magma sources and magma series which is calc-alkaline series. The differences of the mineral size occurred due to the different time of eruption.