Ocean Crust Geochemistry: Construction and Hydrothermal Alteration of Oceanic Crust
Project Manager/Lead Scientist: Debra Stakes
The goal of this effort is to examine magmatic, hydrothermal, and tectonic processes involved in the construction of ocean crust. Initial field reconnaissance will supplement traditional marine geological mapping in search of tectonic/geochemical windows into the subcrustal oceanic biosphere.
The following field and geochemical studies of mid-ocean ridge segments will be included: The Cleft and Endeavour Segments of the Juan de Fuca Ridge are well-mapped, bare rock, mid-ocean ridges that span the tectonic, hydrothermal, and magmatic variability of this plate margin. During 2004, geochemical mapping of the Cleft Segment will obtain the required sample coverage to test two competing hypotheses for the origin of this segment. Also miniature temperature recorders will be deployed at high- and low-temperature vents to sample for microbial constituents. We will then build a three-dimensional picture of the ridge segment and its evolution with the incorporation of the MCS data.
Dives to the Endeavour Segment will undertake the first systematic examination of time/composition variations to assess the volcanological evidence for the presence of an axial magma chamber in this important ridge segment.
The highest priority laboratory analysis for 2004 is to complete the mineralogic and isotopic analyses of sulfide-carbonate samples collected in 2003 from the Guaymas Basin during MBARI's Gulf of California expedition. These samples provide an opportunity to systematically track the growth of chimney edifices in a sedimented-ridge environment.