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Ocean and Earth Science, National Oceanography Centre Southampton

Research project: Superfast spread crust, deep drilling at IODP Site 1256

Currently Active:
Yes

Scientists within the Geochemistry Group have played a prominent role in the effort to recover a complete in situ section of upper oceanic crust created by superfast seafloor spreading. The project, which has currently spanned 10 years and 4 drilling expeditions is the most ambitious effort yet to understand the nature of upper oceanic crust.Deep drilling at Site 1256 in the Guatemala basin extends more than 1500 metres below the sea floor. It penetrates seafloor sediment, extrusive lavas, sheeted dykes and, for the first time, gabbros.

Location of Site 1256 with the age of basement indicated by isochrons (After Teagle et al., 2011 IODP Prel, Rpt., 335)
Site 1256 Location

Scientific Questions:

Progress is being made by the Geochemistry Group on addressing the key scientific questions of the Superfast Spread Crust project

  1. Formation of the ocean crust:
    • Do the recovered gabbros represent cumulate rocks from which dykes and lavas are sourced?
    • Does crustal accretion occur at deeper levels by intrusion of narrow sills or do accumulated crystal residues in melt lenses subside to form lower crust as the crust (as a whole) spreads?
  2. Ground truthing geophysical observations:
    • Can we correlate and calibrate remote geophysical and magnetic observations of oceanic crust with geological observations?
    • What is the real cause of velocity changes within seismic layer 2 and the layer 2/3 transition?
  3. Magmatic and alteration interactions:
    • Characterizing style and intensity of alteration and its affect on the heat flow throughout the crust and magmatic accretion.
    • How do hydrothermal fluids acquire their black smoker fluid chemistry?
  4. Seawater/Basalt interactions:
    • What are the chemical fluxes between the seafloor and oceans and their affects on global chemical budgets?
    • To what extent does ocean crust take up carbon?
    • What is the nature and extent of microbial activity and to what extent does it affect the composition of the ocean crust?
Stratigraphic summary of Site 1256 and predictive model for the depth to axial low velocity zone (predicited gabbro penetration) vs. spreading rate.
Stratigraphy and depth to gabbros

Key Contacts

Prof. Damon Teagle (Proponent and Principal Investigator)

Dr. Michelle Harris (Post Doctoral Researcher)
Dr. Rosalind Coggon (Post Doctoral Researcher)

Joides Resolution at portcall in Yokohama (Credit: John Beck, IODP/TAMU)
Joides Resolution

PhDs and Other Opportunities

Visit GSNOCS

Associated research themes

Formation and Evolution of the Ocean Crust

Volcanic Processes

Hydrothermal Processes and Mineral Deposits

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