Actions for Uranium-lead isotope systematics of Mars inferred from the basaltic shergottite QUE 94201 [electronic resource].

Email RIS file
Bookmark
Report an Issue

Uranium-lead isotope systematics of Mars inferred from the basaltic shergottite QUE 94201 [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy, 2006.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
PDF-file: 46 pages; size: 2.5 Mbytes
Additional Creators
Lawrence Berkeley National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
Access Online

Availability

I Want It
I Want It

Finding items...

Restrictions on Access
Free-to-read Unrestricted online access
Summary
Uranium-lead ratios (commonly represented as ²³⁸U/²°⁴Pb = μ) calculated for the sources of martian basalts preserve a record of petrogenetic processes that operated during early planetary differentiation and formation of martian geochemical reservoirs. To better define the range of μ values represented by the source regions of martian basalts, we completed U-Pb elemental and isotopic analyses on whole rock, mineral and leachate fractions from the martian meteorite Queen Alexandra Range 94201 (QUE 94201). The whole rock and silicate mineral fractions have unradiogenic Pb isotopic compositions that define a narrow range (²°⁶Pb/²°⁴Pb = 11.16-11.61). In contrast, the Pb isotopic compositions of weak HCl leachates are more variable and radiogenic. The intersection of the QUE 94201 data array with terrestrial Pb in ²°⁶Pb/²°⁴Pb-²°⁷Pb/²°⁴Pb-²°⁸Pb/²°⁴Pb compositional space is consistent with varying amounts of terrestrial contamination in these fractions. We calculate that only 1-7% contamination is present in the purified silicate mineral and whole rock fractions, whereas the HCl leachates contain up to 86% terrestrial contamination. Despite the contamination, we are able to use the U-Pb data to determine the initial ²°⁶Pb/²°⁴Pb of QUE 94201 (11.086 ± 0.008) and calculate the μ value of the QUE 94201 mantle source to be 1.823 ± 0.008. This is the lowest μ value calculated for any martian basalt source, and, when compared to the highest values determined for martian basalt sources, indicates that μ values in martian source reservoirs vary by at least 100%. The range of source μ values further indicates that the μ value of bulk silicate Mars is approximately three. The amount of variation in the μ values of the mantle sources (μ ≈ 2-4) is greater than can be explained by igneous processes involving silicate phases alone. We suggest the possibility that a small amount of sulfide crystallization may generate large extents of U-Pb fractionation during formation of the mantle sources of martian basalts.
Report Numbers
E 1.99:ucrl-jrnl-226993
ucrl-jrnl-226993
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
12/22/2006.
"ucrl-jrnl-226993"
Geochimica et Cosmochimica Acta, vol. 71, N/A, September 12, 2007, pp. 5016-5031 71 ISSN 0016-7037; GCACAK FT
Connelly, J N; Gaffney, A M; Borg, L E.
Funding Information
W-7405-ENG-48
View MARC record | catkey: 14378637