The noble gas and carbon systematics of divergent, convergent and strike-slip plate boundaries: Examples from the Reykjanes Ridge, Central American Arc and North Anatolian Fault Zone

Volatiles have proven to be powerful tools for the understanding of geological processes. This results from their marked differences in isotopic and abundance characteristics between the Earth's mantle, crust, hydrosphere and atmosphere, and the fractionation of these source-specific characteristics during volatile transfer between these geologic reservoirs. In this dissertation I examine the behavior of noble gases and CO2 as mantle-derived volatiles are transferred to the hydrosphere and atmosphere via the different types of plate boundary: the Reykjanes Ridge (divergent), Central American Arc (convergent), and North Anatolian Fault Zone (strike-slip).; Chapter II examines the CO2-He-Ne-Ar isotope and abundance characteristics of basaltic glasses from an 800-km long section along the Reykjanes Ridge in order to resolve the volatile characteristics of mantle sources prior to magmatic degassing. We use relative volatile solubilities to place constraints on the degassing process in order to determine the volatile characteristics in the pre-degassed melt. The understanding of elemental fractionation due to the degassing process allows us to (a) explain why OIB contain overall lower helium contents than MORB, and (b) determine the CO 2/3He value of the Icelandic hotspot prior to degassing.; Chapter III focuses on the He-CO2 isotope and relative abundance characteristics of fumaroles, hot springs, water springs, mud-pots and geothermal wells in El Salvador and Honduras to investigate both along and across-arc controls on the release of CO2 from the subducted slab. We derive the provenance of CO2 in the geothermal fluids and compare this with estimates of the CO2 output flux at the arc-front and behind the arc to constrain the amount and composition of subducted sediments involved in the supply of CO2 to arc magmas.; Chapter IV discusses regional and temporal variations in CO2/ 3He, 3He/4He and delta13C values along the North Anatolian Fault Zone in Turkey (NAFZ). The aim of this study is to (a) characterize variations in volatile systematics along the NAFZ, (b) determine underlying causes of these variations, and (c) ascertain if temporal variations during the three-year monitoring period are linked to seismic events. The ultimate goal of this study is to evaluate if these specific volatile parameters have potential as precursors to seismic activity.