The rocks on the surface of the earth have different formation process, beginning with the lava of volcanic activity that flow on the surface of the earth and then cool down forming igneous rocks. Rocks derived by volcanic eruptions contain different types of minerals than those formed by sedimentary or metamorphic processes. The aim of study was to evaluate the relation of magnetic susceptibility with the elemental composition of rock and soil around the Danau Diatas. Magnetic susceptibility was measured using Bartington susceptibility meter MS2B and the element composition has been measured by X-Ray Fluorescence. The values of magnetic susceptibility of low frequency (χlf) obtained for rock are 2332×10−8 m3/Kg, 2161,7×10−8 m3/Kg, and 2791,6×10−8 m3/Kg, while the values of magnetic susceptibility of low frequency (χlf) obtained for soils are 802,4×10−8 m3/Kg, 779,8×10−8 m3/Kg, and 58,4×10−8 m3/Kg. Rock and soil samples contain several elements such as Fe, Mn and Ti, with Fe having the highest concentration and thus the highest potential influence on their magnetic susceptibility.

Volcanic ash is dispersed into the air when an eruption occurs, whilst the magma that reaches the surface of the Earth cools to form igneous rocks before eventually breaking down to form sedimentary rocks. One of the places where the sedimentation of volcanic ash occurs following eruptions are peatlands. This study aims to determine the type of magnetic minerals contained in the peat at Lake Diatas. The identity of the magnetic minerals was determined using the X-Ray Diffraction method. The samples used in this study are taken based on depth of the peat core where a value of magnetic susceptibility had been measured previously. The results of the x-ray diffraction analysis for each sample obtained are the diffraction angle (2θ), distance between fields (dhkl ), diffraction intensity (I) and relative intensity. Data from this measurement are then compared with magnetic mineral data bases in order to identify the identity of the magnetic minerals within the peat. Analysis of the results obtained using X-Ray Diffraction indicate the identity of the magnetic minerals in the peat samples at Lake Diatas. The dominant type of magnetic mineral is magnetite (Fe3O4), along with othermagnetic mineralssuch as hematite. Magnetite diffracts at 18.3773°, 30.9888°, 31.5036°, 53.6169°, 65.7656°, 78.6261°, hematite at 65.9474°, 75.1103°, 78.8619°, while non-magnetic minerals such as quartz diffracts at 28.0575°, 28.2029°, 52.4150°.