En Echelon Volcanic Arc as a Key To Recognize Mantle Diapirs in the Lesser Sunda Arc, Eastern Indonesia

Abstract

Mantle diapirs are a concept led from magma geneses that hydrated mantle above subducting slab comes to be partially fused and lightened, ascending adiabatically and further accelerating the partial fusion. However, it is physically difficult to recognize its presence. The Flores to Alor segment of the Lesser Sunda arc, Indonesia, is characterized by en echelon shaped volcanic islands reflecting the NNW-SSE left-lateral shear stress regime accommodated between north-moving Australian continental accretions in the east and relatively fixed Sundaland in the west. Each element of 'en echelon volcanic islands is a topographically elongated dome that consists of two structures : culmination of anticline of volcanic basement units and clustered young volcanoes. Coexistence of both structures in the same area can be explained when mantle diapirs are assumed : i) Mantle diapir generated clustered young volcanoes and ii) Thinner brittle layer caused by the thermal field above mantle diapirs was deformed by the NNW-SSE left-lateral shear, forming elongated dome.