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Integrated Ocean Drilling Program Schedules Shatsky Rise Expedition for 2009

 

In its newly published schedule for 2009, the Integrated Ocean Drilling Program has scheduled an expedition to core Shatsky Rise, a large oceanic plateau in the northwestern Pacific. The expedition objective is to drill and core a total of ~1 km of igneous rock from 6 sites on the plateau to determine the age, magmatic source, and evolution of this plateau and to test hypotheses of plume and plate origins for oceanic plateaus.

The preliminary schedule for the expedition is 4 September - 4 November, 2009.  Applications to sail as a scientist on board this expedition are being accepted until 9 January 2009. Information about the drilling cruise, including the proposal from which the expedition is being developed, can be found at the IODP Shatsky Rise webpage, and links therein.

Proposed drill sites superimposed on bathymetry and magnetic lineation map.  Red dots show proposed coring sites.  Green symbols denote two DSDP and ODP sites.  Bathymetric contours shown at 500-m intervals with depths shallower than 5000 m in light blue.

 

Proposal 654-Rev2 Abstract

Testing Plume and Plate Models of Ocean Plateau Formation at Shatsky Rise, Northwest Pacific Ocean

One of the most fundamental questions of modern geodynamics is the process of mantle convection and its impact on the Earth’s surface through volcanism. The greatest source of non-ocean-ridge volcanism appears to be massive eruptive episodes that formed oceanic plateaus, volcanic passive margins, and continental flood basalts. A widely accepted hypothesis for such volcanism is that it results from the head of a starting plume, which rises from the deep mantle, spreads out beneath the lithosphere, and melts cataclysmically in a massive outpouring of volcanic activity.

Despite the wide acceptance of this hypothesis, a convincing case for a plume head origin has not been made for any plateau; rather, significant complexities have been revealed by recent drilling of the Kerguelen and Ontong Java plateaus. Indeed, non-plume explanations for non-ridge oceanic volcanism recently have gained favor among some workers, and the very existence of mantle plumes has been questioned.

One great difficulty with research to date is that the original setting, relative to mid-ocean ridges and plate tectonics, is poorly known for most plateaus because they were formed during the mid-Cretaceous when no magnetic reversals formed ridge-parallel anomalies to record ridge locations. Shatsky Rise, located 1500 km east of Japan, is unique in being the only large oceanic plateau formed during a time of magnetic reversals, permitting its tectonic setting to be resolved. Magnetic lineations show that the plateau formed along the trace of a triple junction, intimately related to ridge tectonics.

Existing data demonstrate that several aspects of Shatsky Rise’s history (e.g., massive, rapid initial growth, transition from large to small magma flux, capture of ridges) fit the plume head model. On the other hand, the coincidence of volcanism with the triple junction, ridge jumps, and the lack of isotopic evidence for a hotspot-type mantle source can all be taken as favoring a plate-controlled origin.

Its unique combination of features makes Shatsky Rise the best location on Earth to test plume versus plate-tectonic hypotheses of ocean plateau formation.  We propose a single leg on the non-riser drill ship to core ~1000 m of igneous basement at 6 sites on Shatsky Rise to examine the history, source(s), and evolution of this plateau. From the results, we hope to be able to put to rest the question of whether oceanic plateaus like Shatsky Rise were formed from deep-sourced mantle plumes or interaction of plate boundaries and the lithosphere with the shallow mantle.

For more information, contact Will Sager, co-chief scientist at wwsager@uh.edu

last updated 31st October, 2008

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