Dating the growth of oceanic crust at a slow-spreading ridge.
Nineteen uranium-lead zircon ages of lower crustal gabbros from Atlantis Bank, Southwest Indian Ridge, constrain the growth and construction of oceanic crust at this slow-spreading midocean ridge. Approximately 75% of the gabbros accreted within error of the predicted seafloor magnetic age, whereas approximately 25% are significantly older. These anomalously old samples suggest either spatially varying stochastic intrusion at the ridge axis or, more likely, crystallization of older gabbros at depths of approximately 5 to 18 kilometers below the base of crust in the cold, axial lithosphere, which were uplifted and intruded by shallow-level magmas during the creation of Atlantis Bank.
Schwartz
Joshua J
JJ
Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071, USA.
John
Barbara E
BE
Cheadle
Michael J
MJ
Miranda
Elena A
EA
Grimes
Craig B
CB
Wooden
Joseph L
JL
Dick
Henry J B
HJ