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Autio, Laurie K; Rhodes, J M (1983): Chemiscal composition of basalts from DSDP Legs 69 and 70 Holes [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.816942, Supplement to: Autio, LK; Rhodes, JM (1983): Costa Rica Rift zone basalts: Geochemical and experimental data from a possible example of multistage melting. In: Cann, JR; Langseth, MG; Honnorez, J; Von Herzen, RP; White, SM; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 69, 729-745, https://doi.org/10.2973/dsdp.proc.69.148.1983

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Abstract:
Chemical compositions and 1-atm. phase relations were determined for basalts drilled from Holes 501, 504A, 504B, 505, and 505B on Legs 68, 69, and 70 of the Deep Sea Drilling Project. Chemical, experimental, and petrographic data indicate that these basalts are moderately evolved (Mg' values from 0.60 to 0.70), with olivine plus Plagioclase and often clinopyroxene on the liquidus. Chemical stratigraphy was used to infer that sequential influxes of magma into a differentiating magma chamber or separate flows from different magma chambers or both had occurred.
Two major types of basalt were found to be inter layered: Group M, a rarely occurring type with major element chemistry and magmaphile element abundances within the range of the majority of ocean-floor basalts (TiO2 = 1.3%, Na2O 2.5%, Zr = 103 ppm, Nb = 2.5 ppm, and Y = 31 ppm); and Group D, a highly unusual series of basalt compositions that exhibit much lower magmaphile element abundances (TiO2 = 0.75-1.2%, Na2O = 1.7-2.3%, Zr = 34-60 ppm, Nb = 0.5-1.2 ppm, and Y = 16-27 ppm). The liquidus temperatures of the Group D basalts are high (1230- 1260°C) compared with those of other ocean-floor basalts of similar Mg' values. They have high CaO/Na2O ratios (5-8) and are calculated to be in equilibrium with unusually calcic Plagioclase (An78-84).
The two basalt groups cannot be related by fractionation processes. However, constant Zr/Nb ratios (>40) for the two groups suggest a single mantle source, with differences in magmaphile element abundances and other element ratios (e.g., Zr/Ti, Zr/Y, Ce/Yb) arising through sequential melting of the same source. Magmas similar to Group D, if mixed with more typical mid-ocean-ridge basalt (MORB) magmas in shallow magma chambers, could provide a source for the highly calcic Plagioclase phenocrysts that appear in more common (i.e., less depleted) phyric ocean-floor basalts.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 1.349984 * Median Longitude: -83.742371 * South-bound Latitude: 1.226800 * West-bound Longitude: -83.790000 * North-bound Latitude: 1.920000 * East-bound Longitude: -83.730000
Date/Time Start: 1979-07-08T00:00:00 * Date/Time End: 1979-12-04T00:00:00
Event(s):
68-501 * Latitude: 1.227200 * Longitude: -83.734300 * Date/Time: 1979-07-08T00:00:00 * Elevation: -3457.0 m * Penetration: 337.1 m * Recovery: 70.5 m * Location: North Pacific/FLANK * Campaign: Leg68 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 19 cores; 137.7 m cored; 0.5 m drilled; 51.2 % recovery
69-504A * Latitude: 1.226800 * Longitude: -83.732500 * Date/Time: 1979-09-24T00:00:00 * Elevation: -3458.0 m * Penetration: 277 m * Recovery: 207 m * Campaign: Leg69 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL)
69-504B * Latitude: 1.227200 * Longitude: -83.730200 * Date/Time: 1979-10-07T00:00:00 * Elevation: -3460.0 m * Penetration: 489 m * Recovery: 262 m * Campaign: Leg69 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL)
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. Autio, LK; Rhodes, JM (1983): (Table 2) Chemical composition of basalts from DSDP Hole 69-501. https://doi.org/10.1594/PANGAEA.816940
  2. Autio, LK; Rhodes, JM (1983): (Table 3) Chemical composition of basalt samples from DSDP Holes 69-504A, 69-505A, and 69-505B. https://doi.org/10.1594/PANGAEA.816941
  3. Autio, LK; Rhodes, JM (1983): (Table 1) Chemical composition of basalts from DSDP Hole 69-504B and 70-504B. https://doi.org/10.1594/PANGAEA.816939