Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor Public Deposited

http://ir.library.oregonstate.edu/concern/defaults/2f75r9265

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Within the Australian-Antarctic Discordance (AAD), a boundary exists between isotopically defined “Pacific-type” and “Indian-type” mid-ocean ridge basalt (MORB) erupted along the Southeast Indian Ridge (SEIR). This boundary has migrated westward beneath the easternmost AAD spreading segment at a minimum rate of 25 mm/yr since 4 Ma; however, its long-term history remains a matter of speculation. To determine if Pacific-type upper mantle has migrated westward beneath the eastern Indian Ocean basin as Australia and Antarctica drifted apart during the last 70 m.y., we present new Sr-Nd-Pb isotope data, combined with trace element and 40Ar-39Ar radiometric age determinations, for samples from Legs 28 and 29 of the Deep Sea Drilling Project (DSDP). Basaltic basement at these DSDP sites provides a record of their upper mantle source composition and shows regional variations consistent with upper mantle flow in this region. East of the South Tasman Rise, all DSDP basalts have 87SR/86SR (0.7025-0.7029) and 206Pb/204Pb (18.80-19.48) ratios typical of Pacific-type MORB indicating that Pacific-type upper mantle existed east of the Australian-Antarctic continental margin and beneath the Tasman Sea during the early stages of seafloor spreading in this region. Basalts from DSDP sites west of the AAD have high 87Sr/86Sr (0.7030-0.7035), low 206Pb/204Pb (17.99-18.10) and trace element characteristics typical of present day Indian-type SEIR MORB. Between these two regions, DSDP basalts recovered along the western margin of the South Tasman Rise have isotopic characteristics that are, in one case consistent with Indian-type MORB source (Site 280A) and, in the second case, transitional between Pacific-type and Indian-type mantle sources. The occurrence of seafloor basalts with transitional or Indian-type isotopic characteristics well to the east of the present Indian-Pacific MORB isotopic boundary within the AAD strongly implies that Pacific-type upper mantle has migrated westward into the region since the South Tasman Rise separated from Antarctica circa 40 Ma.
Resource Type
Date Available
Date Issued
Citation
  • Pyle, D.G., Christie, D.M., Mahoney, J.J., and Duncan, R.A., 1995, Geochemistry and Geochronology of ancient southeast Indian and southwest Pacific seafloor. Journal of Geophysical Research, Vol. 100, Pg. 22,261–22,282.
Series
Rights Statement
Funding Statement (additional comments about funding)
Publisher
Language
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2010-04-13T12:52:58Z (GMT) No. of bitstreams: 1 Pyle_et_al_JGR_1995.pdf: 1919817 bytes, checksum: cf880ef4ca992bbeccdbb3583af0c242 (MD5)
  • description.provenance : Made available in DSpace on 2010-04-13T12:52:58Z (GMT). No. of bitstreams: 1 Pyle_et_al_JGR_1995.pdf: 1919817 bytes, checksum: cf880ef4ca992bbeccdbb3583af0c242 (MD5) Previous issue date: 1995-11-10
  • description.provenance : Submitted by Linda Lamb (llamb@coas.oregonstate.edu) on 2010-04-12T23:45:23Z No. of bitstreams: 1 Pyle_et_al_JGR_1995.pdf: 1919817 bytes, checksum: cf880ef4ca992bbeccdbb3583af0c242 (MD5)
ISSN
  • 0148-0227

Relationships

In Administrative Set:
Last modified: 07/21/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items