Dismantling the deep earth : geochemical constraints from hotspot lavas for the origin and lengthscales of mantle heterogeneity
Citable URI
https://hdl.handle.net/1912/2217Location
SamoaDOI
10.1575/1912/2217Keyword
Submarine geology; OphiolitesAbstract
Chapter 1 presents the first published measurements of Sr-isotope variability in olivine-hosted melt inclusions. Melt inclusions in just two Samoan basalt hand samples exhibit most of the total Sr-isotope variability observed in Samoan lavas. Chapter 3 deals with the largest possible scales of mantle heterogeneity, and presents the highest magmatic 3He/4He (33.8 times atmospheric) discovered in Samoa and the southern hemisphere. Along with Samoa, the highest 3He/4He sample from each southern hemisphere high 3He/4He hotspot exhibits lower 143Nd/144Nd ratios than their counterparts in the northern hemisphere. Chapter 2 presents geochemical data for a suite of unusually enriched Samoan lavas. These highly enriched Samoan lavas have the highest 87Sr/86Sr values (0.72163) measured in oceanic hotspot lavas to date, and along with trace element ratios (low Ce/Pb and Nb/U ratios), provide a strong case for ancient recycled sediment in the Samoan mantle. Chapter 4 explores whether the eclogitic and peridotitic portions of ancient subducted oceanic plates can explain the anomalous titanium, tantalum and niobium (TITAN) enrichment in high 3He/4He ocean island basalts (OIBs). The peridotitic portion of ancient subducted plates can contribute high 3He/4He and, after processing in subduction zones, a refractory, rutile-bearing eclogite may contribute the positive TITAN anomalies.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2008
Collections
Suggested Citation
Thesis: Jackson, Matthew G., "Dismantling the deep earth : geochemical constraints from hotspot lavas for the origin and lengthscales of mantle heterogeneity", 2008-02, DOI:10.1575/1912/2217, https://hdl.handle.net/1912/2217Related items
Showing items related by title, author, creator and subject.
-
Internal hydraulic jumps with upstream shear
Ogden, Kelly A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)Internal hydraulic jumps in flows with upstream shear are investigated numerically and theoretically. The role of upstream shear has not previously been thoroughly investigated, although it is important in many oceanographic ... -
Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers
Manning, Cara C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)In this thesis, I use coastal measurements of dissolved O2 and inert gases to provide insight into the chemical, biological, and physical processes that impact the oceanic cycles of carbon and dissolved gases. Dissolved ... -
Coral biomineralization, climate proxies and the sensitivity of coral reefs to CO2-driven climate change
DeCarlo, Thomas M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)Scleractinian corals extract calcium (Ca2+) and carbonate (CO2−3) ions from seawater to construct their calcium carbonate (CaCO3) skeletons. Key to the coral biomineralization process is the active elevation of the CO2−3 ...