Geochemistry of the Igneous Oceanic Crust

Approximately 60% of the Earth’s surface consists of oceanic crust (Cogley, 1984). New ocean crust is created at divergent plate boundaries called ocean ridges or spreading centers (Figure 1). Once created, the oceanic crust is transported off-axis to each side of the spreading center, accumulating sediment as it ages, and is ultimately consumed at subduction zones and returned in a modified form to the mantle (see Chapters 7.01, 2.11, 3.15, and 3.17). The oceanic crust plays a key role in the ongoing processes that modify the compositions of major earth reservoirs. As the product of mantle melting, the generation of new oceanic crust continuously changes the composition of the upper mantle from which it forms (e.g., Chapter 2.08). In addition, the crust is the primary interface of exchange between fluids of the Earth’s surface and the solid earth below. Hydrothermal circulation of seawater through the ocean crust, for example, is a major factor controlling the chemistry of seawater (see Chapters 3.15 and 6.07). Subduction of hydro-thermally altered oceanic crust is believed to initiate arc volcanism, and the particular composition of the subducting crust affects the compositions of the arc magmas (see Chapter 3.18). The deep subduction of altered ocean crust is also the primary means of recycling material back to the mantle where, convectively mixed with ambient mantle, it may form both the source (Diagram Presented) Figure 1 Schematic map of the global ocean ridge system. region of some hotspots and dispersed chemical heterogeneities (see Chapters 3.17, 3.18, 2.03, and.

Duke Scholars

Author Emily M. Klein Earth and Climate Sciences