Application of Geophysical Methods to Investigate the Extention of Primary Tin Deposits in the Pemali Open Pit Mine, Bangka, Indonesia
A study on the application of geophysical methods to investigate primary tin deposits at Pemali has been conducted since early 1970 by the Geological Survey of Indonesia. In 1980, an integrated gravity, magnetic, resistivity sounding and induced polarization survey was conducted along profiles across the tin-bearing zone.
Magnetic and resistivity sounding methods fail to show anomalies relating to the tin-bearing zone. Metal pipes and high voltage power lines in the mine area produce noise which masks the low response anomalies. Furthermore, the complicated subsurface structure produces unreliable resistivity sounding results.
Bouguer gravity anomalies show a low value ranging between 2 and 3 mgals stretching from south to north bending toward the northeast. This low gravity anomaly coincides with the alteration zone, along the contact between granite and metased-iment.
Induced polarization shows relatively low apparent resistivity with a high percent frequency effect (PFE) along the alteration zone. The apparent resistivity anomalies ranging between 10 and 500 ohm-m occur in the south, whereas in the north the anomalies range between 100 and 1,100 ohm-m. These anomalies coincide with a PFE of (1–3) % and (2–5) % respectively.
KeywordsContact Zone Magnetic Anomaly Gravity Anomaly Alteration Zone Induce Polarization
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