THE INFLUENCE OF BASALT INTRUSION CONCERNING TO THE LIMESTONE CHEMICAL COMPOSITION AND QUALITY AT BUKIT KARANG PUTIH PT SEMEN PADANG

• Main Author: Prabowo (NIM 221 05 005), Heri
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/6225
• Institution: Institut Teknologi Bandung

Abstract : <br /> <br /> <br /> <br /> <br /> This research was conducted to find out the influence of basalt intrusion to the limestone formation at Bukit karang Putih as the raw materials of PT Semen Padang. Bukit Karang Putih is located at village of Indarung, Lubuk Kilangan district, Padang, West Sumatra province. Its Geography position is 100 28 4 to 100 30 15 East Longitude and -0 57 40 to -0 58 56 South Latitude. Systematic sampling has been done to collect 21 rock samples, every 5 metre. Start is from the contact of the basalt intrution to 30 metre outwards. The samples have been analyzed chemically and petrographically. The basalt intrusion shows dark gray color and porphyritic texture, consist of plagioclase, olivine, and pyroxene. There are chlorite veinlets found in the basalt sample, set in groundmass of plagioclase microliths and glass. The limestone as the country rock shows variation in the chemical composition toward to the contact of the basalt intrusion. The content of the SiO2, MgO and Fe2O3 increase more than 1% in the near of the basalt intrusion (0 - 15 m), on the countrary the CaO content decrased. The limestone also shows the changings in textures and grain sizes. The more closer to the basalt intrusion the more compact the limestone and the more coarser the grain size. The measurement results show that the coarse grains of calcite crystals increase 90% (5 m from intrusion), 81% (10 m from intrusion), 38% (15 m from intrusion), 27% (20 m from intrusion), 4% (25 m from intrusion). The influence of this basalt intrusion was happened degradation of quality the limestone with attendance of silica content exceeding tolerance range, so that the limestone cannot be used for raw material cement portland. The increasing of silica content happened the limestone with distance 15 metre of basalt intrusion, with percentage increase of SiO2 content equal to 8% - 9% and percentage increase of MgO content equal to 1,38% - 2,05%.