doi:10.2204/iodp.pr.305.2005

Ocean Core Complex Formation, Atlantis Massif 2

Oceanic core complex formation, Atlantis Massif, Mid-Atlantic Ridge: drilling into the footwall and hanging wall of a tectonic exposure of deep, young oceanic lithosphere to study deformation, alteration, and melt generation

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Table of Contents

• TITLE PAGE
• PUBLISHER'S NOTES
• PARTICIPANTS
  • Expedition 304 and 305 Scientific Parties
  • Transocean Officials
  • IODP Shipboard Personnel and Technical Representatives
• ABSTRACT
• INTRODUCTION
• BACKGROUND
• SCIENTIFIC OBJECTIVES
• SITE U1309
• IGNEOUS STRATIGRAPHY
• GEOCHEMISTRY
• HYDROTHERMAL ALTERATION, METAMORPHISM, AND METASOMATISM
• STRUCTURAL RELATIONSHIPS
• GEOPHYSICAL MEASUREMENTS
• MICROBIOLOGY
• SUMMARY
• PRELIMINARY SCIENTIFIC ASSESSMENT
  • Studying the Detachment Fault Zone
  • Core Complex Formation and Evolution
  • Drilling through a Serpentinization Front to Fresh Mantle Rocks
  • Downhole Measurements
  • Accomplished versus Planned Drilling
• OPERATIONS SUMMARY
  • Port Call
  • Transit to Site U1309
  • Site U1309
  • Transit to Ponta Delgada
• REFERENCES
• TABLE
  • Table T1. Operations summary table, Hole U1309.
• FIGURES
  • Figure F1. Tectonic and morphologic setting of Atlantis Massif.
  • Figure F2. Basemap of Atlantis Massif.
  • Figure F3. Seismic profiles of the central dome of Atlantis Massif.
  • Figure F4. Bouguer gravity anomaly map.
  • Figure F5. All holes in upper mantle and lower crustal rocks.
  • Figure F6. Geochemical composition of previously drilled gabbros and peridotites.
  • Figure F7. Pie charts of lithology proportions.
  • Figure F8. Stratigraphic distribution of lithologic proportions.
  • Figure F9. Contact between olivine gabbro and troctolite.
  • Figure F10. Mode of occurrences of dunitic troctolite.
  • Figure F11. Photomicrographs in cross-polarized light.
  • Figure F12. Oxide-rich shear zone.
  • Figure F13. Ni versus Mg#.
  • Figure F14. Downhole variations in Mg#.
  • Figure F15. Total alkalis, Na₂O + K₂O versus SiO₂.
  • Figure F16. Proportions of ranges of alteration.
  • Figure F17. Plot of downhole alteration percent.
  • Figure F18. Serpentinized olivine with kernel texture.
  • Figure F19. Serpentine foliation.
  • Figure F20. Serpentine vein with dusty magnetite in olivine.
  • Figure F21. Metamorphic expansion and serpentinization-induced microfractures.
  • Figure F22. Corona texture in olivine gabbro.
  • Figure F23. Talc, tremolite, and oxides after olivine and chlorite after plagioclase.
  • Figure F24. Dark green amphibole veins crosscutting gabbro.
  • Figure F25. Prehnite vein with zeolite spherules.
  • Figure F26. Downhole variation of vein mineralogy.
  • Figure F27. Downhole plots of structural features.
  • Figure F28. Magmatic foliation.
  • Figure F29. High-temperature plastic deformation foliation.
  • Figure F30. Lower temperature and/or higher strain rate deformation.
  • Figure F31. Fault zones, cataclastic deformation, and veining.
  • Figure F32. Cataclasis of plagioclase.
  • Figure F33. Downhole variation in magnetic properties.
  • Figure F34. Downhole variations in physical properties.
  • Figure F35. Synthetic seismogram model.
  • Figure F36. Temperature recorded by the TAP tool.

Publication date: 16 May 2005

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