Walker, James Allen, 1952-
M.S. (Master of Science)
Department of Geology and Environmental Geosciences
Basalt--Nicaragua; Magmatism--Nicaragua; Igneous rocks--Inclusions--Nicaragua
The Nejapa-Miraflores and Granada lineaments which cut across the Central American volcanic front (CAVF) host numerous monogenetic vents which have erupted diverse basaltic magmas. As previously shown by whole-rock analysis, the basaltic magmas loosely fall into two groups: high and low titanium (Ti). This study used laser ablation inductively coupled mass spectrometry (LA-ICPMS) to analyze trace elements in olivine-hosted melt inclusions from the Nejapa-Miraflores and Granada volcanic lineaments. Low-Ti inclusions tend to have higher values of U/La and Th/Nb ratios when compared to high-Ti inclusions. Varying degrees of crustal contamination, fractional crystallization, melting of carbonates, or melting of modified oceanic lithosphere do not seem to be viable explanations of producing the high- and low-Ti chemical distinctions. The high values of U/La and Th/Nb ratios in the low-Ti melt inclusions suggest that the mantle wedge source that produces these melts contain a greater slab-derived hemipelagic sediment melt component. Geothermometry using trace elements determine an average slab surface temperature to be about 876°C, temperatures permitting the melting of subducted hemipelagic sediments. What is particularly significant is that the contrasting mafic magma compositions in Nicaragua suggest that contributions from subducting lithosphere and subsequent magma generation in subduction zones can be quite variable and complex on a very localized scale.
Her, Xai, "Interpreting Nicaraguan high and low titanium basalts : insights from melt inclusions" (2016). Graduate Research Theses & Dissertations. 3624.
iv, 61 pages
Northern Illinois University
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