Cooling history of Atlantis Bank oceanic core complex: Evidence for hydrothermal activity 2.6 Ma off axis
Article first published online: 28 AUG 2009
Copyright 2009 by the American Geophysical Union.
Geochemistry, Geophysics, Geosystems
Volume 10, Issue 8, August 2009
How to Cite
2009), Cooling history of Atlantis Bank oceanic core complex: Evidence for hydrothermal activity 2.6 Ma off axis, Geochem. Geophys. Geosyst., 10, Q08020, doi:10.1029/2009GC002466., , , , and (
- Issue published online: 28 AUG 2009
- Article first published online: 28 AUG 2009
- Manuscript Accepted: 29 JUN 2009
- Manuscript Revised: 22 JUN 2009
- Manuscript Received: 3 MAR 2009
- core complex;
 We report 26 (U-Th)/He zircon ages from Atlantis Bank, Southwest Indian Ridge, which constrain time scales and rates of lower crustal cooling in ultraslow spreading oceanic crust in this setting. Samples from the detachment fault surface indicate that denuded oceanic crust cooled rapidly (<1 Ma), yielding cooling rates >1200°C/Ma, consistent with existing models for the cooling of oceanic crust. (U-Th)/He zircon ages from samples collected along N–S and E–W trending faults scarps record young ages inconsistent with standard cooling models for lower oceanic crust. These samples have a mean (U-Th)/He zircon age 2.6 Ma younger than their corresponding igneous crystallization ages and record cooling through 200°C well outside the rift valley. Similar anomalously young ages are recorded by zircon, sphene, and apatite fission track data from ODP Hole 735B. We interpret these young ages as recording an off-axis thermal/heating event associated with localized high-temperature (>300°C) hydrothermal fluid flow resulting from underplated mafic magmas.