Document Type

Thesis

Degree

Master of Science (MS)

Department

Geosciences

First Advisor's Name

Andrew Macfarlane

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Rosemary Hickey-Vargas

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Grenville Draper

Third Advisor's Committee Title

Committee member

Keywords

Lead, Isotope, Signatures, Ecuador, Sediment, Geology, Andean, Ore, Downwind, Rrisepac

Date of Defense

7-2-2015

Abstract

Lead isotope ratios of ores and igneous rocks in the Central and Southern Andes show a large-scale geographic pattern related to magmatic source processes. This pattern changes in the Northern Andes for reasons that are not well understood; this study is an investigation of potential causes of this change. Deep ocean sediment samples from the Nazca Plate were analyzed for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, and the data were compared with published data on central Andean ores and ores and igneous rocks from Ecuador. Lead isotopic compositions of the Nazca Plate sediments are quite homogenous and are a close match with Andean ore lead in the coastal arc from central Perú through south-central Chile. However, the lead isotope ratios of the sediment samples are much lower than northern Perú and Ecuador ores. Variations in sediment composition are probably not the source of the northern Andean ore lead isotope pattern.

Identifier

FIDC000098

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