RESEARCH ON THE DENSITY AND SUSCEPTIBILITY OF METAMORPHIC ROCKS IN KARANGSAMBUNG REGION, CENTRAL JAVA, INDONESIA

• Main Author: Jonathan M C D, Raden
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/52165
• Institution: Institut Teknologi Bandung

The Karangsambung Region possesses geological diversity including the presence of metamorphic rocks intermingled with plutonic rocks and shale in the Luk Ulo Melange Complex. The characterization of metamorphic rocks in the complex has been done geologically and geochemically, but it is still lacking from geophysical points of view. This research thesis is intended to determine the physical properties of metamorphic rocks from Luk Ulo, namely the density and frequency-dependent magnetic susceptibility (????????????). Physical property values for certain rock types were obtained from self-measurements of the rock samples in the laboratory, the results of which were then interpreted based on theories foundin literature. Density values were obtained through mathematical calculation of the weight and volume values measured using a technical scale and a caliper. ???????????? values were obtained through measurement using the Bartington MS2 Magnetic Susceptibility Meter. The density of metamorphic rocks was found to be within the range of 2.57-2.66 g/cm3, with the exception of a rock having 2.06 g/cm3. ???????????? values for the rocks were found to be within 0-2%, except for gneiss and marble with values within 2-10%. Based on the density values, it can be assumed that serpentinite was formed through orogenic subduction, while other rocks were formed through orogenic collision in higher temperature and pressure. ???????????? values as low as 0-2% signified that metamorphic rocks only contain small amounts of superparamagnetic (SP) grains, that is < 10%, but that gneiss and marble contain 10-75% SP grains. The high amount of SP grains in gneiss and marble was caused by the high grade of their metamorphism. Compared to the plutonic and sedimentary source rocks in Karangsambung, metamorphic rocks were found to have comparatively lower density but higher frequency-dependent susceptibility. Low density rocks tend towards high magnetic susceptibility, and vice versa. Metamorphism can increase or decrease the amount of magnetic grains within a rock, depending on its grade.