The Formation of Submarine Baruna Komba Ridge on Northeast Flores Waters in Relation to Low Anomaly of Marine Magnetism

Abstract

There are three submarine ridges found on northeast of Flores waters. One of them is Baruna Komba submarine ridge found on south of Komba (Batutara) Volcano. Two others are Abang and Ibu Komba volcanoes located more to the southeast of the Baruna Komba. The position of the Baruna Komba situated more closely to the active Komba volcano and it is considered that the formation of Baruna Komba ridge is younger than the Abang and Ibu Komba volcanoes. The Baruna Komba also interpreted before as a magmatic volcano. Data from marine magnetism shows that there is a low or negative anomaly on Baruna Komba ridge whereas on Abang and Ibu Komba ridges, they are high and positive anomalies. These data indicate that the Baruna Komba ridge is not a volcanic ridge but it is a submarine ridge formed by a volcanic detritus or non magnetized sedimentation. The low anomaly around these submarine ridges gives northwest to southeast lineation and we interpreted also as a big fault on the west side of these ridges. On the other hand, the Abang and the Ibu Komba ridges are closely related to submarine magmatic volcanoes. 
 
 Keywords : The Baruna Komba, magmatic volcano, volcanic detritus, Northeast Flores Waters. 
 
 
 Di perairan sebelah timur laut pulau Flores ditemukan tiga bukit bawah laut. Salah satunya adalah Baruna Komba sebagai bukit bawah laut yang ditemukan di selatan gunung api Komba. Dua bukit lainnya adalah Abang dan Ibu Komba di sebelah tenggara Baruna Komba. Posisi Baruna Komba terletak lebih dekat dengan gunung api Komba yang masih aktif sehingga ditafsirkan sebagai bukit bawah laut termuda dibandingkan gunung api bawah laut Abang dan Ibu Komba. Baruna Komba ditafsirkan sebelumnya sebagai gunung api juga. Dari data magnetik kelautan menunjukkan bahwa adanya anomali negatif atau rendah di atas Baruna Komba, sedangkan di atas Abang dan Ibu Komba menunjukkan anomali positif atau tinggi. Data magnetik ini menandakan bahwa bukit bawah laut Baruna Komba bukan sebagai gunung api tetapi terbentuk oleh material seperti lava, breksi gunung api dan lahar yang terendapkan sewaktu letusan gunung api Komba. Sebaliknya, bukit bawah laut Abang dan Ibu Komba dapat ditafsirkan sebagai gunung api bawah laut yang bersifat magmatik. 
 
 Kata Kunci : Baruna Komba, gunung api bersifat magmatik, endapan vulkanik, perairan timur laut Flores.

Tectonics of Volcanogenic Massive Sulphide (VMS) Deposits at Flores Back Arc Basin: A Review

“…This fact interpreted that Mount Baruna Komba is composed of volcanic deposits resulting from Komba volcano eruption. Therefore, measurable magnetic anomaly value is not directly related to the activity or magmatism process (Sarmili and Suryoko, 2012). Another opinion is the volcanic material deposits as a result of the Komba caldera collapse triggered by frequent eruptions.…”

“…The marine magnetometer data shows the presence of two ridges showing differences magnetic anomaly value ( Figure 6). High anomaly magnetic value indicates the presence of metal elements rich rocks (Sarmili, L., and Suryoko, M.A., 2012). These rocks are related to the presence of magma source beneath the volcano.…”

“…The Bandamin expedition in the northeastern Flores Sea has mapped a northwest-southeast direction submarine ridge. The ridge depth is less than 3000 m occupied by mountain peaks at 700-300 m below sea level (Sarmili, and Suryoko, 2012). The mountain peaks show submarine hydrothermal activities known as Baruna Komba, located at the northwest end, Abang Komba in the middle, and Ibu Komba at the southeastern end of the ridge (Sarmili, 2003 and2004).…”

“…The cone shape peak of the Baruna Komba volcano is suggesting still active (Halbach, et al, 2003a). The isolated hill forms around the foothills of Baruna Komba at depths of 800-1000 m are likely eruption product of Baruna Komba mountain in 2007 or earlier (Sarmili and Suryoko, 2012) which until now still active to forms volcano cones with an altitude 300m below sea level (Sarmili and Troa, 2014). In contrast, the peaks of the Ibu and Abang Komba mountains are relatively elongated and flat at a depth of 300 m (Abang Komba) and 800-900 m peaks of Ibu Komba.…”

“…The study area is located in the Flores back-arc basin (Karig, 1983;McCaffrey and Nabelek, 1984;Tikku, 2011;Gorsel, 2018 andMagni, 2019), northeast of Flores Island, East Nusa Tenggara Province ( Figure 1). The area is divided into three different submarine ridges, the first ridge is the Komba active volcano island (Batutara island) on the most northern part, 400 meters above sea level (Sarmili, and Suryoko, 2012). Next, the second, to southeastward, those are Baruna, and Abang Komba and third, is Ibu Komba ridge (Sarmili et al, 2003 and2004).…”