Journal article
Geodynamic evolution of a forearc rift in the southernmost Mariana Arc: Geodynamic evolution of SEMFR
Island Arc, Vol.22(4), pp.453-476
2013
DOI: 10.1111/iar.12039
Abstract
The southernmost Mariana forearc stretched to accommodate opening of the Mariana Trough backarc basin in late Neogene time, erupting basalts at 3.7–2.7 Ma that are now exposed in the Southeast Mariana Forearc Rift (SEMFR). Today, SEMFR is a broad zone of extension that formed on hydrated, forearc lithosphere and overlies the shallow subducting slab (slab depth ≤ 30–50 km). It comprises NW–SE trending subparallel deeps, 3–16 km wide, that can be traced ≥ ∼30 km from the trench almost to the backarc spreading center, the Malaguana-Gadao Ridge (MGR). While forearcs are usually underlain by serpentinized harzburgites too cold to melt, SEMFR crust is mostly composed of Pliocene, low-K basaltic to basaltic andesite lavas that are compositionally similar to arc lavas and backarc basin (BAB) lavas, and thus defines a forearc region that recently witnessed abundant igneous activity in the form of seafloor spreading. SEMFR igneous rocks have low Na8, Ti8, and Fe8, consistent with extensive melting, at ∼23 ± 6.6 km depth and 1239 ± 40°C, by adiabatic decompression of depleted asthenospheric mantle metasomatized by slab-derived fluids. Stretching of pre-existing forearc lithosphere allowed BAB-like mantle to flow along the SEMFR and melt, forming new oceanic crust. Melts interacted with pre-existing forearc lithosphere during ascent. The SEMFR is no longer magmatically active and post-magmatic tectonic activity dominates the rift.
Details
- Title: Subtitle
- Geodynamic evolution of a forearc rift in the southernmost Mariana Arc: Geodynamic evolution of SEMFR
- Creators
- Julia M. Ribeiro - The University of Texas at DallasRobert J. Stern - The University of Texas at DallasFernando Martinez - University of Hawaiʻi at MānoaOsamu Ishizuka - Japan Agency for Marine-Earth Science and TechnologySusan G. Merle - Oregon State UniversityKatherine Kelley - University of Rhode IslandElizabeth Y. Anthony - The University of Texas at El PasoMinghua Ren - The University of Texas at El PasoYasuhiko Ohara - Japan Agency for Marine-Earth Science and TechnologyMark Reagan - University of IowaGuillaume Girard - University of IowaSherman Bloomer - Oregon State University
- Resource Type
- Journal article
- Publication Details
- Island Arc, Vol.22(4), pp.453-476
- DOI
- 10.1111/iar.12039
- ISSN
- 1038-4871
- Language
- English
- Date published
- 2013
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229967502771
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