Geochemical Investigation of Fluid-Rock Interactions During Chemical Weathering and Subduction ...

• Main Author: Hanna, Heather Dawn
• Format: Thesis
• Language: English
• Published: The University of North Carolina at Chapel Hill University Libraries 2020
• Subjects: Galapagos; Aleutian Island
• Online Access: https://dx.doi.org/10.17615/5w3w-k022; https://cdr.lib.unc.edu/concern/dissertations/cv43p5283

This research examines fluid-rock interactions in two significantly different environments. First, Li isotopic values are evaluated as a potential slab component tracer in Aleutian island arc rocks. The δ7Li values of Aleutian lavas do not exhibit the spatial trends observed in other slab component tracers, nor do they or correlate with these tracers. However, mixing models using 7Li values in conjunction with 143Nd/144Nd ratios suggest most Aleutian samples can be explained by addition of <1-2% sediment-derived aqueous fluid and ≤3% sediment melt to depleted mantle. The study demonstrates that slab signatures may be deciphered via modeling even in arcs where 7Li values do not correlate with slab component indicators, and where sediment and mantle 7Li values overlap.Next the impact of weathering intensity and climate on basalt weathering and pedogenic processes are examined for soil and saprolite samples from San Cristobal island, Galapagos. This research suggests different mineralogical controls ...