Gas hydrate accumulation models of Makran accretionary wedge, northern Indian Ocean

The Makran accretionary wedge, located in the northern Indian Ocean, is resulted from the subduction of the Arabian plate under the Eurasian plate at a low dip angle. In the northern part of the accretionary wedge, sedimentation rate is high and sediments are thick, while in the southern part, thrust faults and tight anticlines dominate. The tectonics is characterized by extension in north and compression in south. In vertical direction, however, faulting activities are strong in the deep and weak in the shallow part. It is a complicated active continental margin characterized by an ultralow angle subduction plate in the world and thus has good conditions for hydrate accumulation. So far, different types of hydrate accumulations have been found. The hydrate accumulation of multi-stepped accretionary wedges mainly occur in the Lower-Slope and Deformation Front under the control of imbricate thrust faults, while the hydrate accumulation of mud diapirs and mud volcanoes types mainly occur in the Mid-Slope and Upper-Slope, which are jointly controlled by sediment thickness and the tectonic tension in the north. Vertically, the hydrate accumulations are characterized by so called "Double floor structure". It means that deep accumulations are mainly controlled by thrust faults, while shallow ones are mainly under the control of normal faults. The above-mentioned hydrate accumulation models may owe their origin to the low angle subduction of the Arabian Plate towards the Eurasian Plate.