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RADIOGENIC ISOTOPE INVESTIGATION OF SOURCES, TRANSPORT, AND DEPOSITION OF RARE EARTH ELEMENTS IN THE OWENS LAKE DRAINAGE BASIN, EASTERN CALIFORNIA

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Minervini, Joseph Mario (2002) RADIOGENIC ISOTOPE INVESTIGATION OF SOURCES, TRANSPORT, AND DEPOSITION OF RARE EARTH ELEMENTS IN THE OWENS LAKE DRAINAGE BASIN, EASTERN CALIFORNIA. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Owens Lake is situated in a mostly-closed basin fed by water and sediments derived primarily from the eastern Sierra Nevada range. Radiogenic isotope variations in USGS Owens Lake core OL-92 were used in conjunction with major and trace element concentrations in streams draining the eastern Sierras to investigate sediment provenance, the chemical weathering and transport of rare earth elements (REE) in the Owens Lake drainage basin, and possible climate-related shifts in weathering patterns of the eastern Sierras during the last ~30 ka. Filtered (<0.45 μm) stream water samples not influenced by hydrothermal fluids or agriculture fall below world average-normalized values for major cations. Concentrations of Nd in the stream water samples are less than 1 nmol L-1, too dilute for isotopic analysis. Strontium and neodymium isotopic analyses were conducted on the carbonate and silicate fractions of sediment samples representing deposition in Owens Lake from ~30 ka to ~10 ka. The fraction of carbonate in Owens Lake sediments increases from ~7 to 67 % during this period, reflecting the desiccation of the lake. Strontium, samarium, and neodymium are strongly partitioned into Owens Lake chemical sediments. Over the past ~30 ka, epsilon Nd values of clastic sediments in Owens Lake remain relatively constant, near -6.5. Chemical sediments remain approximately one epsilon unit higher than the clastic sediments until ~12 ka ago, at which time they shift to less radiogenic values, matching those of the clastic sediment. Differential mineral weathering of more common mineral phases over REE-enriched accessory phases is the most likely cause of the isotopic shift in Owens Lake chemical sediments at ~12 ka ago. Preferential weathering of hornblende could displace the Nd isotopic composition of Owens Lake chemical sediments away from that of the clastic fraction. Depletion of hornblende could allow the Nd isotopic composition of the two sediment fractions to return to similar values. This study represents the first Nd isotope study of a lacustrine system and suggests Nd isotopes could be a useful paleoclimate proxy. Additional work in older Owens Lake sediments and in other lake systems is clearly warranted.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Minervini, Joseph Mariojoeym@alumni.pitt.edu
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairStewart, Brian Wbstewart@pitt.eduBSTEWART
Committee MemberCapo, Rosemary Crcapo@pitt.eduRCAPO
Committee MemberHarbert, William Pbill@earth.eps.pitt.edu
Date: 11 March 2002
Date Type: Completion
Defense Date: 6 December 2001
Approval Date: 11 March 2002
Submission Date: 19 December 2001
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Planetary Science
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: lacustrine sediments; Owens Lake; paleoclimate; radiogenic isotopes; rare earth elements; Sierra Nevada
Other ID: http://etd.library.pitt.edu:80/ETD/available/etd-12192001-143918/, etd-12192001-143918
Date Deposited: 10 Nov 2011 20:11
Last Modified: 15 Nov 2016 13:54
URI: http://d-scholarship.pitt.edu/id/eprint/10426

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