GDL

Intrusion rock,dacite,andesite, volcanic breccia, tuffs

Subject :
Miocene,Pliocene,the resistivity method (dipole-dipole)

Subject Heading :
Geology,hydrology, meteorology,

Call Number (DDC) :
T 551.88 SUD

Document Source : Tesis Magister Rekayasa Pertambangan Bidang Khusus Eksplorasi Sumberdaya bumi (20061264)

Abstrak :

Batuan intrusi yang terdapat di Cineam adalah batuan dasit, dan tersingkap di sebelah barat G. Lubuk yang diperkirakan berumur Miosen Awal. Sedangkan batuan andesit hornbtenda yang tersingkap di G. Lubuk, G. Karat Bandung, dan S. Ciseel Hilir diperkirakan berumur Pliosen (Supriatna dkk.,1992 dalam Prapto dkk.,1997). Batuan intrusi tersebut menerobos batuan lava andesitik, breksi vulkanik dan tuf yang termasuk dalam Formasi Jampang.

Metoda geomagnet digunakan, karena andesit dan dasit mempunyai harga kerentanan magnet yang lebih besar dari batuan samping (beda kerentanan magnet 0.02). Selanjutnya digunakan pula metoda tahanan jenis dipole-dipole, karena daerah peneiitian merupakan zona ubahan, yang mempunyai harga tahanan jenis rendah.

Hasil penafsiran menunjukan di sekitar Gunung Lubuk batuan andesit tersingkap di permukaan, sedangkan di tempat lain (lintasan 5 dan 6) berada pada kedalaman kurang leblh 50 m sampai dengan 200 m. Dasit terdapat pada sebelah kiri lintasan (A - Al) dengan kedalaman kurang lebih 10 m. Batuan ubahan menempati sebagian besar daerah penetitian.

The intrusion rock located at Cineam area is dacite, that exposed at the western part of Gunung Lubuk, and estimated to be Early Miocene in age, whereas the andesite found at Gunung Lubuk, Gunung Karet Bandung, and S. Ciseel Hilir is Pliocene (Supriatna et.al, 1992 in Prapto et.al, 1997). The mentioned intrusion rocks pierce the andesitic lava, volcanic breccia and tuffs which are included under the Jampang Formation.

Geomagnetic method is conducted due to that andesite and dacite have a higher magnetic susceptibility value than the surrounding rocks (with difference 0.02). However, the resistivity method (dipole-dipole) is used because the research area is situated in the alteration zone which has a low resistivity value.

The interpretation results indicate that the andesitic rock crops out around Gunung Lubuk, whereas at other places it is found at about 50 m up to 200 m in depth. Dacite is found at the left side of the profile (A - Al) around 10 m in depth. However, the surrounding rocks which experienced alteration caused by andesite intrusion are found to be widespread in the research area.

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