Identifikasi Pola Struktur Geologi Sebagai Pengontrol Sebaran Mineral Radioaktif Berdasarkan Kelurusan Pada Citra Landsat-8 di Mamuju, Sulawesi Barat

Frederikus Dian Indrastomo, I Gde Sukadana, Suharji Suharji

DOI: http://dx.doi.org/10.17146/eksplorium.2017.38.2.3874

Sari


Abstrak

Daerah Mamuju dan sekitarnya tersusun atas batuan gunung api dengan komposisi mineral mengandung unsur radioaktif seperti uranium (U) dan thorium (Th). Konsentrasi unsur radioaktif di daerah ini mencapai 1.529 ppm eU dan 817 ppm eTh. Mineral-mineral radioaktif yang teridentifikasi terdiri dari thorianite, davidite, gummite, dan autunite. Aktivitas tektonika kemunculan gunung api menyebabkan terbentuknya struktur-struktur geologi yang mengontrol pembentukan kompleks gunung api dan mineralisasi U-Th di daerah tersebut. Identifikasi struktur geologi regional dan rinci di lapangan sangat sulit dilakukan karena vegetasi yang lebat dan tingkat pelapukan yang tinggi. Kelurusan hasil interpretasi dari citra Landsat-8 merupakan manifestasi keberadaan struktur geologi yang mengontrol keberadaan U dan Th. Analisis kelurusan punggung bukit menggunakan formula Sastratenaya digunakan untuk mengetahui umur dan kronologi kelurusan yang terbentuk. Pengukuran laju dosis di daerah penelitian menunjukkan kecenderungan arah sebaran anomali radioaktivitas berarah tenggara–baratlaut. Hasil analisis menggunakan formula Sastratenaya menunjukkan bahwa struktur yang terbentuk adalah struktur berumur relatif tua dan memiliki arah dominan tenggara–baratlaut (N 140–150o E). Berdasarkan interpretasi kelurusan, arah dominan memiliki kemiripan dengan arah sebaran gunung api dan sebaran radioaktivitas. Struktur yang mengontrol pembentukan gunung api dan terkait dengan mineralisasi U dan Th secara umum merupakan struktur berarah tenggara–baratlaut dan terbentuk bersamaan dengan proses mineralisasi U dan Th.

 

Abstract

Mamuju area and its surrounding are composed of volcanic rock containing uranium (U) and thorium (Th) elements. Radioelements concentrations in the area reach 1,529 ppm eU and 817 ppm eTh. Radioactive minerals identified in the area are thorianite, davidite, gummite, and autunite. The geological structures were formed by tectonic activities which controlled the creation of volcanic complex and U-Th mineralization in the complex. Identification of geological structure in the field is very difficult due to densely vegetation and higly degree of weathering. The interpreted lineaments from Landsat-8 imagery are the manifestation of geological structures which have controlled the existence of U and Th. Lineaments analysis using Sastratenaya formula is used to obtain the relative age and chronologies of the lineaments. Dose rate measurements in the area show the trend of radioactivitiy anomalies are trending northwest–southeast. The Sastratenaya formula results the formed structures are relatively older and dominantly directing northwest–southeast (N 140o–150o E). Based on the linement interpretation, the dominant direction has similliarity with volcanic and radioactivity distribution. Structures which controlling the volcanic formation and related to U and Th mineralization generally are the northwest–southeast trending structures, which were created along with U and Th mineralization.


Kata Kunci


uranium; thorium; struktur geologi; kelurusan; formula Sastratenaya; landsat-8

Teks Lengkap:

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Referensi


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