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Arai, Shoji (1982): Petrology of basalts from DSDP Hole 66-487 [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.817810, Supplement to: Arai, S (1982): Petrology of basalts from Site 487, Deep Sea Drilling Project Leg 66, Middle America Trench area off Mexico. In: Watkins, JS; Casey Moore, J; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 66, 711-722, https://doi.org/10.2973/dsdp.proc.66.134.1982

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Abstract:
Basaltic rocks recovered at the Middle America Trench area off Mexico are typical plagioclase-olivine phyric abyssal tholeiites containing less than 0.2 wt.% K2O. Phenocrysts of plagioclase and olivine usually make up the aggregate. Plagioclase phenocrysts are Ca-rich and up to An90. Olivine phenocrysts, which are always attached to plagioclase phenocrysts, are magnesian, Fo88 to Fo89, and contain 0.2 to 0.3 wt. % of NiO. Plagioclase phenocrysts contain numerous glass inclusions with the Mg/Mg+Fe atomic ratio of 0.70 to 0.73, which is distinctly higher than the same ratio of the bulk rock (0.62-0.63). Olivine of Fo88 to Fo89 is equilibrated with the liquid with an Mg/Mg+Fe atomic ratio of about 0.7, assuming the KDMg-Fe between liquid and olivine of 0.3. Small droplets of glass within glass inclusions in plagioclase are more enriched in K2O and volatiles than the host glass. This enrichment may have been caused by the extraction of Al2O3 as plagioclase from the trapped liquid and implies its immiscibility.
Aggregates of plagioclase with small amounts of olivine may have been floated from more primitive magma with an Mg/Mg+Fe atomic ratio of about 0.7, judging from the chemical characteristics mentioned above. Flotation must have occurred at relatively high pressure. Large crystals of plagioclase and smaller crystals of olivine are xenocryst rather than phenocryst. Parental magma of Leg 66 basalt was high-MgO olivine tholeiite.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Latitude: 15.853500 * Longitude: -99.175300
Date/Time Start: 1979-03-24T00:00:00 * Date/Time End: 1979-03-24T00:00:00
Event(s):
66-487 * Latitude: 15.853500 * Longitude: -99.175300 * Date/Time: 1979-03-24T00:00:00 * Elevation: -4764.0 m * Penetration: 190.5 m * Recovery: 119.6 m * Location: North Pacific/TRENCH * Campaign: Leg66 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 20 cores; 180.5 m cored; 9.5 m drilled; 66.3 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
7 datasets

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Datasets listed in this publication series

  1. Arai, S (1982): (Table 1) Bulk chemical compositions of basalts at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817803
  2. Arai, S (1982): (Table 8) Chemical composition of clay and related minerals at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817809
  3. Arai, S (1982): (Table 4) Chemical composition of clinopyroxene at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817806
  4. Arai, S (1982): (Table 6) Chemical composition and minerals of glass inclusions in plagioclase at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817808
  5. Arai, S (1982): (Table 3) Chemical composition of olivine at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817805
  6. Arai, S (1982): (Table 2) Chemical composition of plagioclase at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817804
  7. Arai, S (1982): (Table 5) Chemical composition of chromian spinel and titanomagnetite at DSDP Hole 66-487. https://doi.org/10.1594/PANGAEA.817807