Early accretion and prolonged carbonation of the Pacific Ocean's oldest crust

Newly formed oceanic crust is altered by seawater and carbonated at low temperatures over poorly defined periods of time. We applied in situ U-Pb dating to investigate 28 carbonate veins from Ocean Drilling Program Hole 801C, which is situated in the oldest Jurassic-age oceanic crust preserved in the western Pacific Ocean. Our results indicate that Pacific Ocean crust began accreting at 192 +/- 6 Ma, which is -25 m.y. earlier than previously recognized. Carbonation peaked at 171 +/- 5 Ma and continued at a low rate for more than -65 m.y. after accretion. Jurassic carbonation rates varied over -10 m.y. timescales but encompassed a range similar to that observed today. These data suggest that carbonation rates are relatively insensitive to changes in atmospheric CO2, but confirm the longevity of seafloor alteration as a critical control in global volatile cycling.

Automated summary

The newly formed Pacific Ocean crust began to accrete 25 million years earlier than previously recognized. The carbonation process peaked at 171 million years ago and continued at a low rate for over 65 million years. The carbonation rates during the Jurassic period varied but were similar to those observed today. These findings highlight the long-term significance of seafloor alteration in global volatile cycling.