FRACTURE CHARACTERISTICS AND DISTRIBUTION IN BASEMENT ROCK OUTCROP IN TANJUNG REBO-PENGAIL, BANGKA

• Main Author: Kamil Hadi Panguriseng, Abdulhaq
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/24892
• Institution: Institut Teknologi Bandung

Basement exploration requires fully understanding about characteristics of fractures such as fractures orientation, nature of fractal for each fracture attribute, distribution of intensity and density in Fault Damage Zone (FDZ) and controlling factors of naturally fracture. Linear scanline and windows scanline are one of the methods used to understand the characteristics of fracture. The field work was performed in granitic outcrop at Tanjung Rebo and metamorphic outcrop at Tanjung Pengail, Bangka. A total amount of 3832 fractures have been analyzed in granitic rock and 1426 in metamorphic rock. The result from this study show that there are four fracture orientations, N-S and E-NE trending which is the orientation of shear fractures and NE-SW and NW-SE trending for extension fractures. Fault with NE-SW trend in granitic rock with the width of the FDZ is 2.4 km and N-S fault trend in metamorphic rock with the width of its FDZ is 1.2 km. Fracture intensity in granitic rock range between 9.8 – 45.5 / meter and 17.0 – 40.3 / meter in metamorphic rock, while density fracture in granitic rock range between 0.003 – 0.017 / cm2 and 0.006 – 0.012 / cm2 in metamorphic rock. Distribution of naturally fracture intensity and density shows a declining value as it moves away from the fault core and total percentage of quartz and feldspar also affect the value of fracture intensity and density, the higher the total percentage of quartz and feldspar, the higher the fracture intensity and density. Fracture attributes (spacing, length and aperture) follow the power law distribution that form an order along the curve (c). All fracture attributes are fractal with dimension value in granitic rock range between 1 – 1.8 for spacing, 1 – 1.7 for aperture and 1 – 1.4 for length. In metamorphic, c range between 1.09 – 1.45 for spacing, 1.05 – 1.54 for aperture and 1.22 – 1.59 for length. The fracture distribution function is divided into two, which is located inside of FDZ and outside of FDZ. Porosity in granitic rock range between 0.52 – 1.6% and in metamorphic rock range between 0.83 – 4.6%. Permeability in granitic rock can reach to 810 darcy, while in metamorphic rock can reach up to 1900 darcy. Permeability and fracture width shows exponential relationship.