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Fate of Forearc Lithosphere at Arc‐Continent Collision Zones: Evidence From Local Earthquake Tomography of the Sunda‐Banda Arc Transition, Indonesia

2020; American Geophysical Union; Volume: 47; Issue: 6 Linguagem: Inglês

10.1029/2019gl086472

1944-8007

Pepen Supendi, Andri Dian Nugraha, Sri Widiyantoro, Chalid Idham Abdullah, Nicholas Rawlinson, Phil R. Cummins, Cooper W. Harris, N. Roosmawati, Meghan S. Miller,

Geological and Geochemical Analysis

Abstract A new 3‐D seismic P wave velocity model of the Sunda‐Banda Arc Transition from local earthquake tomography reveals (i) northward subduction of oceanic lithosphere, associated with the convergence of Australia and Sundaland, as a high‐velocity zone extending down to ~200 km depth; (ii) two distinct low‐velocity zones, one immediately above the slab, which is likely a zone of partial melt, and one in the 0–40 km depth range, which is probably a magma chamber associated with active volcanoes above; and (iii) a northerly dipping high‐velocity zone that bisects the two low‐velocity anomalies, which we interpret as an underthrust forearc sliver of continental origin. Based on He 3 /He 4 measurements from volcanic outflows, it is possible that the magma supply is contaminated by interaction with this forearc sliver as it ascends from the melt region below.