Accession Number : ADA482075


Title :   Dismantling the Deep Earth: Geochemical Constraints from Hotspot Lavas for the Origin and Lengthscales of Mantle Heterogeneity


Descriptive Note : Doctoral thesis


Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA


Personal Author(s) : Jackson, Matthew G


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a482075.pdf


Report Date : Feb 2008


Pagination or Media Count : 151


Abstract : 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 43Nd/44Nd 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.


Descriptors :   *LAVA , *GEOCHEMISTRY , *HOT SPOTS , *EARTH MANTLE , *HETEROGENEITY , TANTALUM , STRONTIUM , SEDIMENTS , NIOBIUM , BASALT , MELTS , THESES , ANOMALIES , TITANIUM


Subject Categories : Geology, Geochemistry and Mineralogy


Distribution Statement : APPROVED FOR PUBLIC RELEASE