Re-Os isotope systematics and weathering of Precambrian crustal rocks; implications for the marine osmium isotope record

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doi: 10.1016/S0016-7037(98)00227-0
Authors:Peucker-Ehrenbrink, Bernhard; Blum, Joel D.
Author Affiliations:Primary:
Woods Hole Oceanographic Institution, Department Marine Chemistry and Geochemistry, Woods Hole, MA, United States
Dartmouth College, United States
Volume Title:Geochimica et Cosmochimica Acta
Source:Geochimica et Cosmochimica Acta, 62(19-20), p.3193-3203. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037
Publication Date:1998
Note:In English. Woods Hole Oceanogr. Inst., Contrib. No. 9725. 58 refs.; illus., incl. 2 tables
Summary:Re-Os isotope systematics of Precambrian granitic source rocks and their weathering products and behaviour, using a chronosequence of soils developed on glacial moraines in the Wind River Range, Wyoming, USA, are reported. The same samples were previously analysed for mineralogy, Rb-Sr and U-Th-Pb isotopes and major elements. Analyses are presented of 187Os/186Os, 187Os/188Os, 187Re/186Os, and elemental Os and Re of < 2 mm and > 2 mm soil fractions and soil leaches, bedrock samples and mineral separates (biotite, plagioclase and quartz, K-feldspar and magnetite from gneiss). Biotite or a trace inclusion in biotite carries most Os and Re and is the most radiogenic mineral. Re-Os isotope systematics of the samples indicate that rapid oxidation of magnetite mobilizes Os with an isotopic composition similar to that of the bulk soils. It is suggested that glacial scouring and weathering of glacial tills following deglaciation of Precambrian shields around the North Atlantic were responsible for the slightly more radiogenic North Atlantic sea-water compared to other oceans. Os isotope analyses are also given of freshwater Fe-Mn nodules and crusts. [R.K.H.]
Sections:Clay minerals
Subsections:Petrology; weathering; soils
Subjects:Absolute age; Bedrock; Cenozoic; Chronosequences; Clastic sediments; Climate effects; Dates; Deglaciation; Experimental studies; Geochemistry; Glacial environment; Glacial geology; Glaciation; Interglacial environment; Isochrons; Isotope ratios; Isotopes; Leaching; Marine environment; Metals; Moraines; Os-187/Os-186; Osmium; Oxidation; Paleoclimatology; Platinum group; Precambrian; Quaternary; Radioactive isotopes; Re/Os; Rhenium; Sea water; Sediments; Soils; Stable isotopes; Terrestrial environment; Till; Weathering; North America; Rocky Mountains; U. S. Rocky Mountains; United States; Wind River Range; Wyoming; Re-187; Re-187/Os-186
Abstract Numbers:99M/3539
Record ID:1999030778
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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