Abstract

Erupted compositions at mid ocean ridges reflect a series of incompletely understood processes that influence both magma compositions and crustal construction in predictable ways. Although global variations in MORB compositions are rooted in the underlying mantle, much of what is erupted at ridges has been significantly and systematically modified by processes in the crust, which vary systematically as functions of parameters such as melt supply, magma recharge, hydrothermal cooling rate, and uppermost magma chamber depth. Geochemical studies of individual mid-ocean ridge eruptions provide high spatial and temporal resolution snapshots of these processes, and the diversity of extant conditions in these magmatic systems at any point in time. Short-lived radioisotope tracers indicate that magma generation and transport through the mantle and crust can be quite rapid (decades to centuries), suggesting that steady state conditions are unlikely to exist anywhere on the system for very long, with implications for eruption frequency and the longevity of marine hydrothermal systems.