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Ishiwatari, Akira (1992): Geochemistry of Early Cretaceous basaltic rocks from ODP Sites 123-765 and 123-766 [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.760903, Supplement to: Ishiwatari, A (1992): Petrology, geochemistry, and mineralogy of the Early Cretaceous evolved N-MORB from Sites 765 and 766, eastern Indian Ocean. In: Gradstein, FM; Ludden, JN; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 123, 201-213, https://doi.org/10.2973/odp.proc.sr.123.160.1992

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Abstract:
The Early Cretaceous basaltic rocks obtained from Sites 765 and 766 in the eastern Indian Ocean floor were mostly iron-rich normal mid-ocean ridge basalts (N-MORB), which were derived from a depleted mantle source having strongly light rare earth element (LREE)-depleted rare-earth patterns and a high titanium/zirconium (Ti/Zr) ratio. Basaltic rocks in the upper part of the Site 765 basement section include megacrysts and gabbroic fragments of widely varying mineral chemistry. These megacrysts range from An90 plagioclase, including highly magnesian basaltic glass coexisting with augite of Mg# (= 100 Mg/[Fe+Mg]) at 85, to An50 plagioclase coexisting with hypersthene. This varying mineralogy of megacrysts and gabbroic fragments indicates that a considerable degree of fractional crystallization took place in the magma chamber. The unusual negative correlation between incompatible elements (e.g., TiO2) and FeO*/MgO observed among Site 765 basement basalts and fresh volcanic glasses suggest source-mantle heterogeneity in terms of FeO*/MgO. Strontium isotope ratios (87Sr/86Sr) of the basaltic rocks from both sites are between 0.7027 and 0.7033 and are comparable to those of mid-Indian Ocean ridge basalts (MIORB).
The basalt pebbles encountered in the sedimentary section may have been transported from the basement highs nearer the Australian continent and include basaltic compositions ranging from primitive N-MORBs to evolved enriched (E)-MORBs. Their mantle source was not as depleted as that of the basement basalts. These rocks may be the products of earlier volcanism that took place during the rifting of the Australian continent.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: -17.294667 * Median Longitude: 115.201500 * South-bound Latitude: -19.932000 * West-bound Longitude: 110.454100 * North-bound Latitude: -15.976000 * East-bound Longitude: 117.575200
Date/Time Start: 1988-09-07T00:00:00 * Date/Time End: 1988-10-26T00:00:00
Event(s):
123-765 * Latitude: -15.976000 * Longitude: 117.575200 * Date/Time Start: 1988-09-07T00:00:00 * Date/Time End: 1988-10-18T00:00:00 * Elevation: -5728.0 m * Penetration: 2564 m * Recovery: 732.7 m * Location: South Indian Ridge, South Indian Ocean * Campaign: Leg123 * Basis: Joides Resolution * Method/Device: Composite Core (COMPCORE) * Comment: 134 cores; 1265.9 m cored; 0 m drilled; 57.9% recovery
123-765B * Latitude: -15.976000 * Longitude: 117.575200 * Date/Time Start: 1988-09-08T02:30:00 * Date/Time End: 1988-09-11T04:25:00 * Elevation: -5728.0 m * Penetration: 395.6 m * Recovery: 270.92 m * Location: South Indian Ridge, South Indian Ocean * Campaign: Leg123 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 41 core; 395.6 m cored; 0 m drilled; 68.5 % recovery
123-765C * Latitude: -15.976000 * Longitude: 117.575200 * Date/Time Start: 1988-09-11T04:25:00 * Date/Time End: 1988-09-22T10:30:00 * Elevation: -5728.0 m * Penetration: 963.9 m * Recovery: 373.35 m * Location: South Indian Ridge, South Indian Ocean * Campaign: Leg123 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 65 cores; 613.7 m cored; 0 m drilled; 60.8 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
3 datasets

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Datasets listed in this publication series

  1. Ishiwatari, A (1992): (Table 3) Representative pyroxene and spinel chemistry of basaltic rocks from ODP Sites 123-765 and 123-766. https://doi.org/10.1594/PANGAEA.760901
  2. Ishiwatari, A (1992): (Table 2) Major-element chemistry of volcanic glass in pillow margins and of glass inclusions in plagioclase megacrysts of ODP Site 123-765. https://doi.org/10.1594/PANGAEA.760898
  3. Ishiwatari, A (1992): (Table 4) Strontium isotope ratios of ODP Holes 123-765D and 123-766A. https://doi.org/10.1594/PANGAEA.760902