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Carman, M F; Dietrich, Volker; Sommerauer, J (1984): Geochemistry at DSDP Leg 73 Holes [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.811032, Supplement to: Carman, MF et al. (1984): Petrography and mineral chemistry of basalts from Holes 519A, 520, 522B, and 524 - Leg 73 (South Atlantic) of the Deep Sea Drilling Project. In: Hsü, KJ; LaBrecque, JL; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 73, 545-577, https://doi.org/10.2973/dsdp.proc.73.120.1984

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Abstract:
Basalt was encountered under sediments in four holes (519A, 520, 522B, and 524) on Leg 73. The rocks in three holes (519A, 520, and 522B) are typical somewhat evolved mid-ocean-ridge basalt (MORB) tholeiites that occur as pillows, flows, and sills. In Hole 524 there occur (1) an upper alkalic sequence of pillows and a sill enclosed in Cretaceous volcaniclastic sedimentary rocks and (2) a lower, moderately evolved, slightly alkalic tholeiite in a multiple sill, also injected into Cretaceous volcaniclastic rocks.
The tholeiites of Holes 519A, 520, and 522B display chemical, mineralogical, and petrographic features that are characteristic of MORB found elsewhere. The chilled margins of flows and pillows display a sequence of quench textures, and the interiors of the thicker flows and sills have the intersertal, intergranular, subophitic, and ophitic textures normally found in such rocks. The rocks are finely microphyric, with pre-emptive Plagioclase and sparse olivine microphenocrysts. Only pillows were encountered in Hole 520, and the rocks of that hole are distinctive in that they show a variolitic structure not seen in any of the other holes of Leg 73.
The tholeiites of Hole 524 are petrographically similar to those of Holes 519A to 522B, but they are more strongly microphyric, with all major silicate phases (olivine, Plagioclase, and clinopyroxene) present as abundant to common microphenocrysts. The alkalic rocks of Hole 524 are distinctive in that (1) Fe-Ti oxides are present as pre-eruptive microphenocrysts in addition to the silicate phases, (2) the Plagioclase grains are epitaxially mantled by alkalic feldspar, and (3) biotite and magnesioriebeckite occur as late-stage accessories.
The mineral phases have compositions well within the ranges of typical MORB from many locations: Plagioclase microphenocrysts average An76-80, olivine Fo81-87, clinopyroxene microphenocrysts are close to En46Fs12Wo44 and zoned toward modest ferrosilite enrichment, titanomagnetites have average 64.4 mol.% ulvospinel, and ilmenites average 8.2 mol.% hematite. Trace elements are likewise well within the ranges reported from other oceanic sites.
Clinopyroxenes from the tholeiitic multiple sill display an unusual compositional zoning in which M1 cations (Fe, Mg, Mn, Ti, and Cr) show sympathetic variations from core to rim. There is a distinct drop in iron, manganese, and titanium and a concomitant increase in magnesium and chromium from inner core to outer core and then a strong reversal of these trends in the rims. The temporary reversal of the normal differentiation pattern from inner core to outer core in clinopyroxene occurs in both the early and late phases of the multiple sill and is not explained, although it may be related to variations in oxygen fugacity or the crystallization pattern of the Fe-Ti oxide minerals.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: -27.609288 * Median Longitude: -4.271934 * South-bound Latitude: -29.484200 * West-bound Longitude: -11.666200 * North-bound Latitude: -25.523300 * East-bound Longitude: 3.512300
Date/Time Start: 1980-04-22T00:00:00 * Date/Time End: 1980-05-21T00:00:00
Event(s):
73-519A * Latitude: -26.136700 * Longitude: -11.666200 * Date/Time: 1980-04-22T00:00:00 * Elevation: -3769.0 m * Penetration: 180 m * Recovery: 61.4 m * Location: South Atlantic/RIDGE * Campaign: Leg73 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 9 cores; 84.5 m cored; 0 m drilled; 72.7 % recovery
73-520 * Latitude: -25.523300 * Longitude: -11.185700 * Date/Time: 1980-04-28T00:00:00 * Elevation: -4207.0 m * Penetration: 456.5 m * Recovery: 69 m * Location: South Atlantic/VALLEY * Campaign: Leg73 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 29 cores; 249 m cored; 15.5 m drilled; 27.7 % recovery
73-522B * Latitude: -26.114000 * Longitude: -5.129700 * Date/Time: 1980-05-06T00:00:00 * Elevation: -4441.0 m * Penetration: 170.4 m * Recovery: 26 m * Location: South Atlantic/PLATEAU * Campaign: Leg73 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 6 cores; 40.5 m cored; 0 m drilled; 64.2 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
8 datasets

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Datasets listed in this publication series

  1. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 7) Geochemistry of spinel at DSDP Hole 73-519A. https://doi.org/10.1594/PANGAEA.811029
  2. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 8) Geochemistry of biotite at DSDP Hole 73-524. https://doi.org/10.1594/PANGAEA.811030
  3. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 5) Geochemistry of clinopyroxenes at DSDP Leg 73 Holes. https://doi.org/10.1594/PANGAEA.811026
  4. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 6A) Geochemistry of Fe-Ti oxides at DSDP Leg 73 Holes. https://doi.org/10.1594/PANGAEA.811028
  5. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 4) Geochemistry of feldspars at DSDP Leg 73 Holes. https://doi.org/10.1594/PANGAEA.811025
  6. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 3) Geochemistry of olivine at DSDP Leg 73 Holes. https://doi.org/10.1594/PANGAEA.811024
  7. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 11) Fe-Ti oxide geothermometry at DSDP Holes 73-519A and 73-524. https://doi.org/10.1594/PANGAEA.811031
  8. Carman, MF; Dietrich, V; Sommerauer, J (1984): (Table 2) Minerals of modal analyses at DSDP Leg 73 Holes. https://doi.org/10.1594/PANGAEA.811023