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In-situ SIMS U-Pb dating of Caribbean basalts and lavas

In-situ SIMS U-Pb dating of Caribbean basalts and lavas. Presentation for CAMIRO Project 08E03 ‘Reconstruction of supercontinents back to 2.7 Ga’ Project meeting March 5, 2011 Kevin Chamberlain, University of Wyoming. In-situ SIMS U-Pb dating.

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In-situ SIMS U-Pb dating of Caribbean basalts and lavas

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  1. In-situ SIMS U-Pb dating of Caribbean basalts and lavas Presentation for CAMIRO Project 08E03 ‘Reconstruction of supercontinents back to 2.7 Ga’ Project meeting March 5, 2011 Kevin Chamberlain, University of Wyoming

  2. In-situ SIMS U-Pb dating • U-Pb minerals survive alteration better than many Ar-Ar targets • In-situ can date baddeleyite and zircon grains as small as 3 microns--undateable by other methods • Textural settings preserved • Can resolve both primary and metamorphic dates • Age Precisions of 5% or better

  3. Magmatic z ~130 Ma Def. z 90 Ma

  4. Recent U-Pb dating projects-Leeward Antilles and Tobago Tobago North Coast schist & San Souci fm. Magmatic & metamorphic ages. Pis: Art Snoke, Univ. WY Andrew Kerr & Iain Neill, Cardiff Leeward Antilles Aruba, Curacao, Bonaire, Los Rocas test of Caribbean-Columbia Oceanic Plateau PI: Jim Wright, University of Georgia

  5. Recent U-Pb dating projects-Leeward Antilles and Tobago Tobago North Coast schist & San Souci fm. Magmatic & metamorphic ages. Pis: Art Snoke, Univ. WY Andrew Kerr & Iain Neill, Cardiff Aruba: Bd = 102 Ma Zir = 97 Ma Curacao: Bd = 115 Ma Zir = 80 Ma Bonaire: Bd = 112 Ma Zir = 93 Ma Los Rocas: Zir = 87 Ma Leeward Antilles Aruba, Curacao, Bonaire, Los Rocas test of Caribbean-Columbia Oceanic Plateau PI: Jim Wright, University of Georgia

  6. SIMS baddeleyite and zircon data-produced March 4, 2011-San Souci sample

  7. Cretaceous Oceanic Plateaus – potential U-Pb dating targets Prepared by Andrew Kerr, Cardiff The Shatsky Rise likely formed around Jur-Cret boundary – but only 1 Ar-Ar date - samples from 2009 IODP leg are now available to all workers - There is scope for U-Pb dating given potential links to Tithonian black shales • Drilled Ontong Java • Plateau sections are • poorly dated – only • Ar-Ar from the 1990s • the validity of the 90Ma • Ar-Ar age (site 803) • questioned by many. • given potential links to • anoxia and black shales • at ~122 and 93Ma, • new U-Pb dating is well • worthwhile There are only 3 Ar-Ar dates for the 105-90Ma parts of Kerguelen Plateau (and one has quite a disturbed Ar-Ar plateau) - the volume of magma emplaced in this time period on the KP was of the order of 9 million km3 - so this event could have contributed significantly to global anoxia and consequent black shale formation – more (U-Pb) dating is clearly warranted. Drilled Caribbean plateau see next slide

  8. Proto-Caribbean Oceanic Plateau – U-Pb dating targets These fragments are mid-late Cretaceous but formed within the Caribbean – not in the Pacific like the main CCOP. They are potentially significant in the maturation of hydrocarbon reservoir rocks Margot Fm. basalts ~ 120-100Ma by paleo Duarte Fm. basalts ~90Ma – by Ar-Ar but ages are disputed Sans Souci Fm. basalts & gabbros Being dated by Kevin Expected age 120-100Ma El Copey Fm. basalts with Kevin for assessment for U-Pb dating Expected age 120-100Ma Siquisique Fm. basalts & gabbros with Kevin for assessment for U-Pb dating. Dated by Ar-Ar to 90-95 Ma but spectra quite disturbed. Other nearby exposures have recently been identified and will be mapped and sampled in detail later this year.

  9. Caribbean-Colombian Oceanic Plateau – U-Pb dating targets These fragments of the CCOP are notoriously difficult to date by Ar-Ar (too altered) Western Cordillera of Colombia/Ecuador. Only a handful of Ar-Ar ages (some quite disturbed plateaus) from throughout the entire length of this ~1000km- long sequence. Most are 95-85Ma, but there are younger ~75Ma dates. U-Pb dates from a selected set of samples from the N to the S of the Cordillera (the most extensive continuous sequence in the province) is likely to more rigorously constrain the timing of the CCOP Other Caribbean targets: ROV samples of Beata Ridge Panama Dominican Republic Aruba (in hand-Jim Wright) Curacao (In hand-Jim Wright)

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