Thesis
Lead isotope compositions of subducting sediments around the Pacific
Washington State University
Master of Science (MS), Washington State University
2005
Handle:
https://hdl.handle.net/2376/406
Abstract
Pb isotope compositions were analyzed for 79 DSDP (Deep Sea Drilling Project) sediment samples from nine active trench systems around the Pacific to constrain the Pb isotopic character of subducting sediments. One striking feature of these results is that these sediments lie along narrow, positively correlated arrays on the Pb isotopic composition plots, ranging from unradiogenic compositions, similar to Pacific mid-ocean ridge basalts (MORBs), represented by the Philippine and Ryukyu sites, to highly radiogenic compositions, represented by the Nicobar and Astoria fan sites. There are predictable negative correlations between Pb isotope ratios and EHf and ENd, clearly related to the input of continental sediments of varying age and crustal history. Most of the sediments analyzed plot along broad, negatively correlated Hf-Pb and Nd-Pb, and positively correlated Hf-Nd, isotopic arrays. Some pelagic sediments plot distinctly above the terrestrial Hf-Nd isotopic array. Their distinctive behavior on the Hf-Pb and Nd-Pb plots cast light on the mechanisms that cause the deviation from the terrestrial Hf-Nd isotopic array: the decoupled Hf and Nd Sources account for the anomalous Hf-Nd character in these pelagic sediments (Vervoort, 2002). The Pb isotope compositions can also help in discriminating the sediment provenance. Sediments from DSDP site 174 on the Astoria Fan off the Washington-Oregon coast lie along highly linear Pb isotopic trends, which fit well in a simple binary mixing model. Their Pb isotope compositions verify that the radiogenic end member comes from Proterozoic source regions far inland from the coast of North America, probably the Belt Supergroup (Prytulak, 2004).
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Details
- Title
- Lead isotope compositions of subducting sediments around the Pacific
- Creators
- Chunjiang Yu
- Contributors
- Jeffrey D. Vervoort (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525106701842
- Language
- English
- Resource Type
- Thesis