VERIFIKASI LITOLOGI TERHADAP NILAI KERENTANAN MAGNETIK DI PERAIRAN BANGKA BELITUNG

Peta anomali magnetik menunjukkan bahwa perairan Bangka Belitung dicirikan oleh pasangan tinggian dan rendahan panjang gelombang anomali dengan amplitudo -200 nTâ€”500nT. Sedangkan dari peta distribusi kerentanan magnetik, tinggian magnetik Belitung dibatasi oleh nilai kerentanan magnetik antara 0,001 cgs unit dan 0,003 cgs unit. Anomali positip rendah dicirikan oleh nilai kerentanan magnetik batuan antara 0,001-0,003 cgs unit merupakan benda intrusif bawah laut yang diduga berupa pluton granitik jenis granit-biotit yang berasosiasi dengan mineral kasiterit. Pluton granitik tersebut sama seperti granit yang berafiliasi dengan endapan timah di daratan Pulau Belitung. Misalnya singkapan granit yang terdapat di sekitar pantai Gembira yang menunjukkan tipe granit biotit porfiritik dengan fenokris ortoklas. Kata Kunci: anomali magnetik, kerentanan magnetik, granit, Bangka Belitung Magnetic anomaly map shows that the Bangka Belitung waters are characterized by a pair of hight and low long-wave amplitude anomalies values of -200 nTâ€”500 nT. While the distribution map of magnetic susceptibility magnetic high of Belitung is limited magnetic susceptibility values of 0.001 cgs units and 0.003 cgs units. Positive anomaly of low magnetic is characterized susceptibility values between 0.001 to 0.003 cgs units suggested as a body of submerged intrusive rock body granitic plutons of granite biotite type associated with casiterite mineral. Granitic plutons are the same as granite affiliated with tin deposits in the mainland island of Belitung. For example there are granite outcrops around the Gembira coast that shows the type of porphyritic biotite granite with phenocrysts ortoclas. Keywords: Magnetic anomaly, magnetic susceptibility, granite, Bangka Belitung

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Magnetic susceptibility anomalies of lithosphere beneath eastern Europe and the Middle East

Geophysics ◽

10.1190/1.1442220 ◽

1986 ◽

Vol 51 (9) ◽

pp. 1711-1724 ◽

Cited By ~ 17

Author(s):

J. Arkani‐Hamed ◽

D. W. Strangway

Keyword(s):

Magnetic Susceptibility ◽

Middle East ◽

Eastern Europe ◽

Magnetic Anomaly ◽

Common Features ◽

Core Field ◽

The Core ◽

Anomaly Map ◽

Susceptibility Contrast ◽

High Magnetic Susceptibility

Standard inversion methods for inverting aeromagnetic anomalies into magnetic susceptibility contrast in the crust are based on the assumption that the core field is constant over the region considered. This assumption, however, does not hold over regions of a few thousand kilometer extent. An inversion technique is developed which takes into account the variations in the core field, both in direction and in intensity. It can also take into account the surface topography of a magnetic layer within the lithosphere. The technique is applied to a scalar magnetic anomaly map of eastern Europe and the Middle East, derived from the magnetometer satellite (MAGSAT) data. The magnetic susceptibility contrast map thus obtained delineates the major tectonic features of the region. Small‐scale Precambrian shields are characterized by high magnetic susceptibility. The Alpine‐Himalayan belt has a distinct magnetic signature. The collision zones are low‐susceptibility regions, whereas the continental plates within the belt have high magnetic susceptibility. The well‐known iron formation of Kursk is delineated by a strong magnetic susceptibility high. The magnetometer satellite has measured the Earth’s magnetic field at two distinct local times, dawn and dusk, and provided two independent magnetic anomaly maps. The scalar magnetic anomaly map is based on the common features of the two maps. A covariance technique is developed which selects these common features on the basis of the correlation spectra of the two maps.

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