Journal of Marine Science: Research & Development
Open Access

Abstract

Weh Island is located in Nangroe Aceh Darussalam (NAD) Province, in the city of Sabang, at 95�?° 12â�?�? 00â�?-05�?° 23â�?�? 00â�? longitude and 05�?° 46â�?�? 00â�? - 05�?° 55â�?�? 00â�? latitude. This is one of the most recent volcanic islands in Sunda orogenic belt which span from Andaman Sea to Banda. This is a type C volcano which means the eruption center of the volcano is unknown but it have fumarole field which is a sign of a past volcanic activity. Based on petrographic and geochemistry analysis show that the type of volcanic rocks found are basalt-andesite. The magma type is tholeiitic and the tectonic environment of volcanic rocks is â�?spreading center islandâ�?. This result is compatible with tectono-structural of Great Sumatra strike â�?�?slip fault which is related to active spreading â�?�? arc basin. The structural deformation is a result from Pliosen â�?�? Pleistosen tectonic and volcanic activity which is indicated by discovery of the remnant of ancient volcanoes, lineament of volcanic cone, fault scrap, volcanic depression, and lineament of eruption center and also hydrothermal activity as result of past volcanism.Hydrothermal activity discovered in the sea and land of this area. Research about submarine fumarole have been conducted by the Marine Geological Institute of Indonesia (PPPGL) indicate that there is a large amount of submarine fumarole in this area. In the depth 10 meter, the submarine fumarole originated from joints or fissure with a north â�?�? south bearing, whereas in the depth of 40 â�?�? 50 meter these fumarole mostly formed on top of an undulation which have a similar form as a crater. Based on the location of these fumarole, Semangko strike â�?�?slip fault is assumed to have a significant role in the formation and development of it. The fault made joints and fissures on the seabed which make hydrothermal circulation possible.

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