Osmium isotopic characteristics of mantle-derived rocks

Journal Article · Wed May 01 00:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90318-Y· OSTI ID:6005801

Martin, C E ^[1]

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1. Yale Univ., New Haven, CT (United States)

Osmium isotopic compositions and Re and Os concentrations have been determined on ultramafic and mafic rocks derived from the contemporary mantle. These samples have a large range in measured {sup 187}Os/{sup 186}Os (1.0032 to 1.173). Peridotites from the Southwest Indian Ridge and Zabargad Island (Red Sea) and cumulate chromitites from Zambales ophiolite (Philippines) range in {sup 187}Os/{sup 186}Os from 1.083 to 1.0032. Ocean island basalts (OIBs) from Hawaii and Iceland considered to be representative of a distinct plume-source mantle have {sup 187}Os/{sup 186}Os of about 1.10. Other OIBs which have high {sup 187}Os/{sup 186}Os of {ge}1.151 require involvement of at least one additional component with a different Os isotopic composition in their formation. The observed range in Os isotopic composition is consistent with an average silicate earth {sup 187}Os/{sup 186}Os of 1.10. This value is higher than the value determined by Allegre and Luck (1980) but is within the range observed in meteorites. In this case, all the analyzed suboceanic peridotites as well as subcontinental samples have been affected to varying degrees by Re depletion related to ancient melt extraction events which occurred in some regions of the mantle.

• OSTI ID: 6005801
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 55:5; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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