Peridotites and gabbros from the Parece Vela backarc basin: Unique tectonic window in an extinct backarc spreading ridge
Article first published online: 12 JUL 2003
Copyright 2003 by the American Geophysical Union.
Geochemistry, Geophysics, Geosystems
Volume 4, Issue 7, July 2003
How to Cite
2003), Peridotites and gabbros from the Parece Vela backarc basin: Unique tectonic window in an extinct backarc spreading ridge, Geochem. Geophys. Geosyst., 4, 8611, doi:10.1029/2002GC000469, 7., , , and (
- Issue published online: 12 JUL 2003
- Article first published online: 12 JUL 2003
- Manuscript Accepted: 13 MAY 2003
- Manuscript Revised: 6 MAY 2003
- Manuscript Received: 1 NOV 2002
- Backarc basin;
- amagmatic tectonics;
- lithospheric process;
 Peridotite samples from a backarc basin setting will help better understand global mid-oceanic ridge processes. Here we report detailed petrological data of serpentinized peridotite and gabbro from the extinct Parece Vela Basin in the Philippine Sea. Despite its relatively fast spreading rate (8.8–7.0 cm/y full-rate), the Parece Vela Basin spreading ridge (the Parece Vela Rift) has the distinct morpho-tectonic characteristics that indicate a small degree of mantle melting, including the presence of a huge mullion structure (the Godzilla Mullion). Peridotites in the Parece Vela Rift are exposed on the Godzilla Mullion as well as at a segment midpoint. The most notable characteristic of Parece Vela Rift peridotites is small-scale juxtaposition (i.e., a single-dredge-haul scale) of fertile peridotite and depleted peridotite (dunite and plagioclase-bearing peridotite). We interpret that the fertile peridotite (F-type) is the residue of a small degree of mantle melting (∼4% near-fractional melting of a MORB-type mantle), whereas dunite (D-type) and plagioclase-bearing peridotite (P-type) are products of melt-mantle interaction. The associated evolved gabbros may represent the shallow level fractionated melt intruded into P-type. The distinct morpho-tectonic characteristics, peridotite exposure at a segment midpoint, and the presence of fertile peridotite may result from an extreme transform fault effect caused by the ridge-transform geometry of short first-order segments sandwiched by closely spaced fracture zones (“transform sandwich effect”).