Dating seawater alteration in the Shatsky Rise basalts from IODP Expedition 324, using U-Pb isotope geochemistry

Author(s): Romanova, Irina V.; Murphy, David T.
Author Affiliation(s): Primary:
Queensland University of Technology, School of Earth, Environmental and Biological Sciences, Brisbane, Queensl., Australia
Volume Title: 34th international geological congress; abstracts
Source: International Geological Congress [International Geological Congress, Abstracts = Congrès Géologique International, Résumés, Vol.34, p.302; 34th international geological congress, Brisbane, Queensl., Australia, Aug. 5-10, 2012. Publisher:], [location varies], International CODEN: IGABBY
Note: In English. Accessed on June 17, 2014
Summary: Shatsky Rise is a large early-Cretaceous oceanic plateau, situated in the northwestern Pacific. The rise was rapidly emplaced in an active spreading ridge in a relatively short period of time (10 m.y.). The plateau consists of three massifs, Tamu, Ori and Shirshov, showing both size and age progression. During the IODP Expedition 324 five cores were drilled on these three elevated massifs. The recovered igneous material from Shatsky Rise shows slight to complete alteration. Basalts with very high U/Pb are observed in many horizons in Expedition 324 drill cores. This elevated U/Pb reflects U addition during seawater circulation and is enhanced adjacent to sedimentary inter-beds (areas showing high natural gamma radiation (NGR) responses). It is suggested that the intensity of alteration depends on seawater penetration capacity into the igneous rocks. Two of the Expedition 324 drill cores, U1346A (Shirshov massif) and U1349A (Ori massif), show the highest level of alteration and the greatest NGR counts. Both of these cores are situated on the Shatsky summits, where the fluid-rock interaction was more intense. Here we present Pb isotope results of leaching experiments on samples with high U/Pb. This allows for the generation of Pb-Pb isochron ages for alteration. The seawater alteration age can be compared to Ar/Ar isotope ages of alteration. These studies have implications for seawater percolation through oceanic plateaux significantly after cessation of volcanism.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; 07 Marine Geology and Oceanography; Alteration; Basalts; Chronology; Cores; Cretaceous; Expedition 324; IODP Site U1346; IODP Site U1349; Igneous rocks; Integrated Ocean Drilling Program; Isotopes; Lower Cretaceous; Mesozoic; North Pacific; Northwest Pacific; Pacific Ocean; Sea water; Shatsky Rise; Spreading centers; U/Pb; Volcanic rocks; Water-rock interaction; West Pacific
Coordinates: N380024 N380024 E1623843 E1623843
N360657 N360657 E1582730 E1582730
Record ID: 2014083196
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