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Os-187/Os-188 and Highly Siderophile Element Systematics of Apollo 17 Aphanitic Melt RocksIntroduction: Generally chondritic relative abundances and high absolute abundances of the highly siderophile elements (HSE: Ru, Rh, Pd, Re, Os, Ir, Pt, Au) in Earth s upper mantle provide strong evidence that these elements were added to the Earth following the last major interaction between its metallic core and silicate fraction. So called "late accretion" may have added materials comprising as much as 0.8% of the total mass of the Earth and possibly a similar proportion of mass to the Moon. We have begun to study the chemical nature of late accreted materials to the Earth - Moon system by examining the HSE contained in lunar impact-melt rocks. The HSE contained in melt rocks were largely added to the Moon during the period of time from the origin of the lunar highlands crust (4.4- 4.5 Ga) to the end of the late bombardment period (ca. 3.9 Ga). These materials provide the only direct chemical link to the late accretionary period. The chemical fingerprints of the HSE in late accreted materials may enable us to ascertain under what conditions and where in the solar system the late accreted materials formed. The Os-187/Os-188 ratios (reflecting long-term Re/Os), coupled with ratios of other HSE, can be diagnostic for identifying the nature of the impactor. A critical issue, however, will be deconvolving the exogenous from indigenous components.
Document ID
20050173970
Acquisition Source
Headquarters
Document Type
Conference Paper
Authors
Puchtel, I. S.
(Maryland Univ. College Park, MD, United States)
Walker, R. J.
(Maryland Univ. College Park, MD, United States)
James, O. B.
(Geological Survey Reston, VA, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2005
Publication Information
Publication: Lunar and Planetary Science XXXVI, Part 16
Subject Category
Lunar And Planetary Science And Exploration
Funding Number(s)
CONTRACT_GRANT: NNG04GJ49A
CONTRACT_GRANT: NASA Order W-10252
Distribution Limits
Public
Copyright
Public Use Permitted.
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