Research in Geochemistry - Hess Deep

In collaboration with fellow Duke faculty member Jeff Karson, Emily Klein and graduate students have been studying the variations in composition among dikes, lavas and gabbroic rocks recovered during an Alvin dive program to the Hess Deep Rift in the equatorial Pacific. The Hess Deep Rift is an intra-oceanic rift valley located at the tip of the westward propagating Cocos-Nazca plate boundary. The steep, EW-trending, upper walls of the rift valley expose the upper 2 km of oceanic crust created about 1 m.y. ago at the NS-trending East Pacific Rise. Fault scarps along the rift walls provide a tectonic window into this fast-spread crust. To date, the Hess Deep remains one of the only tectonic windows into fast-spread crust that can be used to infer processes attending the construction of oceanic crust beneath fast spreading centers like the EPR. Our dive program has produced an unprecedented data set in terms of the sample coverage combined with a detailed understanding of the geologic context provided by the structural studies of Jeff Karson's structure group. Our geochemical results provide important on the processes by which the ocean crust is produced. For example, our study of dike compositions revealed that dikes of widely varying compositions are interleaved, suggesting significant along-axis transport of magma from chemically distinct portions of the axial magma chamber. In addition, our our comparison of lava and dike compositions revealed that most dikes do not erupt lavas, and that the magma density of lavas is greater than that of most dikes, suggesting a density filter on magma eruption.

For more infornation, visit the Hess Deep Cruise web site at http://www.nicholas.duke.edu/hessdeep/hessdeep.html

Selected Publications: