Integrated Ocean Drilling Program Expedition 324 preliminary report; Testing plume and plate models of ocean plateau formation at Shatsky Rise, Northwest Pacific Ocean; 4 September-4 November 2009

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doi: 10.2204/
Author(s): Sager, William W.; Sano, Takashi; Geldmacher, Jörg; Iturrino, Gerardo; Evans, Helen; Almeev, Renat; Ando, Atsushi; Carvallo, Claire; Delacour, Adélie; Greene, Andrew R.; Harris, Amber C.; Herrmann, Sandra; Heydolph, Ken; Hirano, Naoto; Ishikawa, Akira; Kang, Moo-Hee; Koppers, Anthony A. P.; Li Sanzhong; Littler, Kate; Mahoney, John; Matsubara, Noritaka; Miyoshi, Masaya; Murphy, David T.; Natland, James H.; Ooga, Masahiro; Prytulak, Julie; Shimizu, Kenji; Tominaga, Masako; Widdowson, Mike; Woodard, Stella C.
Integrated Ocean Drilling Program, Expedition 324 Scientists, College Station, TX
Author Affiliation(s): Primary:
Texas A&M University, Department of Oceanography, College Station, TX, United States
National Museum of Nature and Science, Japan
Lamont-Doherty Earth Observatory, United States
University of Hanover, Federal Republic of Germany
Pusan National University, South Korea
Université Pierre et Marie Curie, France
Source: Preliminary Report (Integrated Ocean Drilling Program), Vol.324, 78p. Publisher: IODP Management International, College Station, TX, United States. ISSN: 1932-9423
Note: In English. 117 refs.
Summary: Oceanic plateaus are giant volcanic features whose existence implies an extraordinary flux of magma from mantle to lithosphere. By understanding their formation, these large igneous provinces can be important indicators of fundamental processes of mantle convection and geodynamics. Although it is widely thought that oceanic plateaus arise from massive eruptions resulting from the arrival of a deep mantle plume head at the lithosphere, an alternative explanation is that plateau eruptions are related to decompression melting of unusually fusible mantle beneath fast-spreading ridges. Shatsky Rise was cored during Expedition 324 because it is a unique oceanic plateau, formed during the Late Jurassic and Early Cretaceous at a rapidly spreading triple junction, with characteristics that could be attributed to either model of formation. Shatsky Rise is also a monster volcanic construct whose formation style is poorly understood. The goal of Expedition 324 was to core the igneous rocks of Shatsky Rise and the sediments above to examine the age, physical volcanology, geochemistry, and tectonic evolution of the rise as well as the sedimentation history. Five sites were cored and four were logged, with one site (U1346) on the summit of Shirshov Massif and two sites each on Ori (Sites U1349 and U1350) and Tamu (Sites U1347 and U1348) Massifs. Basaltic lava flows were recovered at four of these sites and complement previous Ocean Drilling Program Site 1213 (south flank of Tamu Massif) in providing a record of lava flow emplacement on Shatsky Rise. Instead of lava flows, cores from Site U1348 recovered a thick sequence (∼120 m) of volcaniclastic sediments topped with shallow-water carbonaceous sandstones. Lavas recovered at Sites U1347 and U1350 are fresh enough to be suitable for high-quality radiometric age dating and planned geochemical/isotopic studies. Although lavas from Site U1346 and U1349 were moderately to highly altered, it is expected that they will provide important age information with suitable treatment and will be useful for most geochemical studies. Even though the volcaniclastic rocks of Site U1348 are highly altered, a single interval containing relatively fresh glass shards will provide valuable contestants on magma source characteristics. Shatsky Rise lava flows occur primarily as packages of pillow basalt and massive inflation units, frequently interbedded with volcaniclastic sediment. The richest massive inflation flows, up to ∼23 m thick, occur on Tamu Massif at Sites 1213 and U1347. They are similar to massive flows cored on Ontong Java Plateau and found in continental flood basalt provinces. At Site U1347, the relationship of pillows and massive flows suggests magmatic cycles that began with the emplacement of massive sheet flows and waned with pillow lavas. Moreover, paleomagnetic inclination trends at both Sites 1213 and U1347 imply that little time passed between the emplacement of individual flows. The implication is that Tamu Massif concluded with massive, high-effusion rate eruptions. Massive flows are also found at Sites U1349 and U1350, on Ori Massif's summit and flank, respectively, but the entire 53 m succession of igneous rocks cored at Site U1346, on the Shirshov Massif summit, consists of pillow lavas. The massive flow units are thinner at Ori Massif than most flows penetrated on Tamu Massif. Moreover, Site U1350 geochemical and paleomagnetic inclination trends imply greater time and more eruptive variability. The simplest conclusion from the observed trends in lava flow style across the three main edifices of Shatsky Rise is that the average eruptions become smaller and less effusive from Tamu to Ori to Shirshov massifs. Recovered basement rocks from the two summit sites (U1346 and U1349) on Shirshov and Ori massifs show the most severe alteration, apparently from both low and moderately higher temperature fluid-rock interaction, the latter especially for Site U1349.
Year of Publication: 2009
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 13 Areal Geology, General; Algae; Alteration; Basalts; Basement; Biostratigraphy; Cores; Crust; Drilling; Expedition 324; Foraminifera; Geochemistry; IODP Site U1346; IODP Site U1347; IODP Site U1348; IODP Site U1349; IODP Site U1350; Igneous rocks; Integrated Ocean Drilling Program; Invertebrata; Large igneous provinces; Magmas; Magmatism; Mantle; Mantle plumes; Marine drilling; Microfossils; Mid-ocean ridge basalts; Nannofossils; North Pacific; Northwest Pacific; Oceanic crust; Pacific Ocean; Paleomagnetism; Phanerozoic; Plantae; Plate tectonics; Protista; Sedimentary rocks; Seismic stratigraphy; Shatsky Rise; Tholeiite; Volcanic rocks; Volcaniclastics; Volcanism; West Pacific
Coordinates: N380000 N380000 E1622300 E1622300
N321800 N321800 E1590800 E1590800
N341500 N341500 E1591400 E1591400
N360400 N360400 E1581700 E1581700
N360200 N360200 E1591000 E1591000
Record ID: 2010018099
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