Evolution of the Lau Basin; insights from ODP Leg 135

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doi: 10.1029/GM088p0125
Author(s): Hawkins, James W.
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, Geological Research Division, La Jolla, CA, United States
Other:
Rosenstiel School of Marine and Atmospheric Sciences, United States
Volume Title: Active margins and marginal basins of the western Pacific
Volume Author(s): Taylor, Brian, editor; Natland, James
Source: Active margins and marginal basins of the western Pacific, edited by Brian Taylor and James Natland. Geophysical Monograph, Vol.88, p.125-173. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0065-8448. ISBN: 978-1-118-66396-7 CODEN: GPMGAD
Note: In English with English summary. 178 refs.; illus., incl. 4 tables, geol. sketch map
Summary: Subduction at the Tonga Trench gives rise to arc volcanism and plays an active role in forming the Lau (backarc) Basin. Ocean Drilling Program drilling, together with GLORIA imagery, and intensive studies of backarc spreading centers have given us new insight into the evolution of the Lau Basin. Many of the features and processes appear to be common to other western Pacific backarc basins. Among the more significant new findings are recognition that the basin opened in a two-stage process. Initially, crustal extension and rifting formed small sub-basins that were partly filled with basaltic flows and sediments. The second stage of opening involves seafloor spreading from propagating rifts. Although the magma source is in a supra-subduction zone setting, the petrology of the crust indicates that the predominant source of melt has been mantle similar to the MORB-source. Evidence for mixing with melts, on a small scale, shows a contribution from a subduction component (i.e., similar to melts of arc-source mantle). As the basin opened, arc-composition, intrabasin edifices formed alongside the main production of MORB-like crust. A highly heterogeneous source is implied. Isotope data show that two distinct MORB-source mantle components were involved. Older units came from a "Pacific" source, whereas modern basalts come from mantle with an "Indian" source character. Parts of the northern basin carry the isotope signature of OIB source and helium isotope data suggest an influx like that of the Samoan "plume-source".
Year of Publication: 1995
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; 18 Geophysics, Solid-Earth; Alkaline earth metals; Back-arc basins; Basalts; Basins; Cenozoic; Chemical ratios; Crust; East Pacific; Eocene; Evolution; Extension tectonics; GLORIA; He-4/He-3; Helium; Igneous activity; Igneous rocks; Imagery; Island arcs; Isotope ratios; Isotopes; Lau Basin; Leg 135; Major elements; Mantle; Metals; Models; Nd-144/Nd-143; Neodymium; Noble gases; Ocean Drilling Program; Pacific Ocean; Paleogene; Plate convergence; Plate tectonics; Provenance; Rare earths; Rifting; Sea-floor spreading; South Pacific; Southeast Pacific; Sr-87/Sr-86; Stable isotopes; Strontium; Subduction; Tectonics; Tertiary; Tonga Trench; Trace elements; Triple junctions; Volcanic rocks
Coordinates: S232045 S183003 W1751752 W1775145
Record ID: 1995043344
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