Physics
Scientific paper
Sep 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997gecoa..61.3619c&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 61, Issue 17, p. 3619-3632.
Physics
7
Scientific paper
A detailed TIMS study of (234Uexc/238U), (230Th/232Th), and Th/U ratios have been performed on the outermost margin of ten hydrogenous FeMn crusts from the equatorial Pacific Ocean and west-central Indian Ocean.Th/U concentration ratios generally decrease from the crust's surface down to 0.5-1 mm depth and growth rates estimated by uranium and thorium isotope ratios are significantly different in FeMn crusts from the Peru Basin and the west-central Indian Ocean. FeMn crusts from the same geographical area define a single trend in plots of Ln(234Uexc/238U) vs. Ln(230Th/232Th) and Th/U ratios vs. age of the analysed fractions. Results suggest that (l) hydrogenous FeMn crusts remain closed-systems after formation, and consequently (2) the discrepancy observed between the 230Th and 234U chronometers in FeMn crusts, and the variations of the Th/U ratios through the margin of FeMn crusts, are not due to redistribution of uranium and thorium isotopes after oxyhydroxide precipitation, but rather to temporal variations of both Th/U and initial thorium activity ratios recorded by the FeMn layers. Implications of these observations for determination of FeMn crust growth-rates are discussed. Variations of both Th/U and initial Th activity ratios in FeMn crusts might be related to changes in particle input to seawater and/or changes in ocean circulation during the last 150 ka.
Chabaux François
Cohen Seth A.
Hein James R.
Unions R. K.
No associations
LandOfFree
238U234U230Th disequilibrium in hydrogenous oceanic FeMn crusts: Palaeoceanographic record or diagenetic alteration? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with 238U234U230Th disequilibrium in hydrogenous oceanic FeMn crusts: Palaeoceanographic record or diagenetic alteration?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and 238U234U230Th disequilibrium in hydrogenous oceanic FeMn crusts: Palaeoceanographic record or diagenetic alteration? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1225899