Gao, Yongjun; Hoefs, Jochen; Przybilla, Reinhold; Snow, Jonathan E (2006): Mineral and oxygen isotopic compositions in a profile through the altered lower oceanic crust, ODP Hole 176-735B [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.706351, Supplement to: Gao, Y et al. (2006): A complete oxygen isotope profile through the lower oceanic crust, ODP Hole 735B. Chemical Geology, 233(3-4), 217-234, https://doi.org/10.1016/j.chemgeo.2006.03.005
Always quote citation above when using data! You can download the citation in several formats below.
Abstract:
ODP Hole 735B located on the Southwest Indian Ridge at 57°E is an in situ sampled long, continuous section of lower oceanic crust. Oxygen isotope compositions of constituent minerals of Leg 176 gabbros have been measured by UV-laser oxygen isotope microprobe. Together with existing data from Leg 118, a complete oxygen isotope profile through the lower oceanic crust has been obtained. Most clinopyroxenes and olivines have normal mantle values of ~5.5 per mil and ~5.2 per mil, respectively, while plagioclases show slight d18O enrichment relative to its mantle value of 6.1per mil.
Down-hole variations of Hole 735B gabbro indicate a downward decreasing d18O profile, with a kink at a depth of about 800 m below sea floor. Above this depth, gabbros are depleted in 18O relative to unaltered basalts, while below ~800 m they show nearly unmodified d18O values. Abundant seawater penetration appears to be limited to the upper part of the lower crust at ODP site 735 (~800 m into the gabbroic layer and ~2-2.5 km into the oceanic crust from the top of pillow basalts). Mass balance calculations show that the lower crust formed under this ultra-slow-spreading ridge has an average d18O value of 5.5 per mil. The whole crust at Site 735 has an overall 18O enrichment with d18O values of 6.0 per mil to 7.8 per mil, depending on the possible variation of the d18O values of the upper pillow basalts and sheeted dykes. The apparent difference in oxygen isotope compositions of ocean crusts formed with different spreading rates has important implications on the buffering of ocean water over geological time, as well as on the oxygen recycling between crust and mantle through subduction. The difference of seawater penetration between fast- and slow-spreading ridges could be related to their particular magmatic-tectonic history during the formation and aging of the crust. However, more analyses on continuous sections through oceanic and ophiolitic crust in different tectonic settings are required to derive any predictive models.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Latitude: -32.723210 * Longitude: 57.266010
Date/Time Start: 1997-10-24T13:45:00 * Date/Time End: 1997-12-01T19:00:00
Event(s):
176-735B * Latitude: -32.723210 * Longitude: 57.266010 * Date/Time Start: 1997-10-24T13:45:00 * Date/Time End: 1997-12-01T19:00:00 * Elevation: -720.6 m * Penetration: 1508 m * Recovery: 865.99 m * Location: Indian Ocean * Campaign: Leg176 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 122 cores; 1003.2 m cored; 504.8 m drilled; 86.3 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
2 datasets
Download Data
Datasets listed in this publication series
- Gao, Y; Hoefs, J; Przybilla, R et al. (2006): (Table 2) Averages of oxygen isotope compositions of minerals from ODP Hole 176-735B gabbros. https://doi.org/10.1594/PANGAEA.706345
- Gao, Y; Hoefs, J; Przybilla, R et al. (2006): (Table AT1) Oxygen isotope compositions of component minerals in ODP Hole ODP 176-735B gabbros. https://doi.org/10.1594/PANGAEA.706348