Richardson, Stephen H; Erlank, A J; Duncan, A R; Reid, D L (1982): Rb, Sr, Sm and Nd concentrations and isotopic composition of basalts from DSDP Leg 74 (Table 1) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.711009, Supplement to: Richardson, SH et al. (1982): Correlated Nd, Sr and Pb isotope variation in Walvis Ridge basalts and implications for the evolution of their mantle source. Earth and Planetary Science Letters, 59(2), 327-342, https://doi.org/10.1016/0012-821X(82)90135-2
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Abstract:
Basement intersected in DSDP holes 525A, 528 and 527 on the Walvis Ridge consists of submarine basalt flows and pillows with minor intercalated sediments. These holes are situated on the crest and mid and lower northwest flank of a NNW-SSE-trending ridge block which would have closely paralleled the paleo mid-ocean ridge (Rabinowitz and LaBrecque, 1979 doi:10.1029/JB084iB11p05973, Moore et al. (1983 doi:10.1130/0016-7606(1983)94<907:TWRTDS>2.0.CO;2). The basalts were erupted approximately 70 m.y. ago, an age equivalent to that of immediately adjacent oceanic crust in the Angola Basin and coraistent with formation at the paleo mid-ocean ridge (Moore et al., 1983). The basalt types vary from aphyric quartz tholeiites on the ridge crest to highly plagioclase phyric olivine tholeiites on the ridge flank. These show systematic differences in incompatible trace element and isotopic composition. Many element and isotope ratio pairs form systematic trends with the ridge crest basalts at one end and the highly phyric ridge flank basalts at the other.
The low 143Nd/144Nd (0.51238), 206Pb/204Pb (17.54), 207Pb/204Pb (15.47), 208Pb/204Pb (38.14) and high 87Sr/86Sr (0.70512) ratios of the ridge crest basalts suggest derivation from an old Nd/Sm-, Rb/Sr- and Pb/U-enriched mantle source. This isotopic signature is similar to that of alkaline basalts on Tristan da Cunha but offset to significantly lower Nd and Pb isotopic ratios. The isotopic ratio trends may be extrapolated beyond the ridge flank basalts with higher 143Nd/144Nd (0.51270), 206Pb/204Pb (18.32), 207Pb/204Pb (15.52), 208Pb/204Pb (38.77) and lower 87Sr/86Sr (0.70417) ratios in the direction of increasingly Nd/Sm-, Rb/Sr- and Pb/U-depleted source compositions. These isotopic correlations are equally consistent with mixing of depleted and enriched end member melts or partial melting of an inhomogeneous, variably enriched mantle source. However, observed Zr-Ba-Nb-Y interelement relationships are inconsistent with any simple two-component model of magma mixing, as might result from the rise of a lower mantle plume through the upper mantle. Incompatible element and Pb isotopic systematics also preclude extensive involvement of depleted (N-type) MORB material or its mantle sources. In our preferred petrogenetic model the Walvis Ridge basalts were derived by partial melting of mantle similar to an enriched (E-type) MORB source which had become heterogeneous on a small scale due to the introduction of small-volume melts and metasomatic fluids.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: -28.545667 * Median Longitude: 2.357533 * South-bound Latitude: -29.070700 * West-bound Longitude: 1.763300 * North-bound Latitude: -28.041500 * East-bound Longitude: 2.985300
Date/Time Start: 1980-06-10T00:00:00 * Date/Time End: 1980-07-04T00:00:00
Minimum Elevation: -4428.0 m * Maximum Elevation: -2467.0 m
Event(s):
74-525A * Latitude: -29.070700 * Longitude: 2.985300 * Date/Time: 1980-06-10T00:00:00 * Elevation: -2467.0 m * Penetration: 678.1 m * Recovery: 406.6 m * Location: South Atlantic/CREST * Campaign: Leg74 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 62 cores; 549.7 m cored; 6 m drilled; 74 % recovery
74-527 * Latitude: -28.041500 * Longitude: 1.763300 * Date/Time: 1980-06-28T00:00:00 * Elevation: -4428.0 m * Penetration: 384.5 m * Recovery: 243.4 m * Location: South Atlantic * Campaign: Leg74 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 43 cores; 380 m cored; 4.5 m drilled; 64.1 % recovery
74-528 * Latitude: -28.524800 * Longitude: 2.324000 * Date/Time: 1980-07-04T00:00:00 * Elevation: -3800.0 m * Penetration: 555 m * Recovery: 271.9 m * Location: South Atlantic/RIDGE * Campaign: Leg74 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 47 cores; 441 m cored; 0 m drilled; 61.7 % recovery
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Event label | Event | ||||
| 2 | Sample code/label | Sample label | Richardson, Stephen H | DSDP/ODP/IODP sample designation | ||
| 3 | Sample comment | Sample comment | Richardson, Stephen H | |||
| 4 | Rubidium | Rb | mg/kg | Richardson, Stephen H | X-ray fluorescence (XRF) | precision c. 1% |
| 5 | Strontium | Sr | mg/kg | Richardson, Stephen H | X-ray fluorescence (XRF) | precision c. 0.3% |
| 6 | Rubidium-87/Strontium-86 ratio | 87Rb/86Sr | Richardson, Stephen H | Isotope ratio mass spectrometry | ||
| 7 | Strontium-87/Strontium-86 ratio | 87Sr/86Sr | Richardson, Stephen H | Isotope ratio mass spectrometry | measured, normalized to 0.70800 for Eimer and Amend SrCO3 | |
| 8 | Strontium-87/Strontium-86 ratio | 87Sr/86Sr | Richardson, Stephen H | Calculated | Initial ratios calculated for an age of 70 m.y. using lambda Rb = 1.42 | |
| 9 | Strontium-87/Strontium-86 ratio, error | 87Sr/86Sr e | ± | Richardson, Stephen H | Isotope ratio mass spectrometry | measured |
| 10 | Samarium | Sm | mg/kg | Richardson, Stephen H | X-ray fluorescence (XRF) | precision c. 0.3% |
| 11 | Neodymium | Nd | mg/kg | Richardson, Stephen H | X-ray fluorescence (XRF) | precision c. 0.3% |
| 12 | Samarium-147/Neodymium-144 ratio | 147Sm/144Nd | Richardson, Stephen H | Isotope ratio mass spectrometry | ||
| 13 | Neodymium-143/Neodymium-144 ratio | 143Nd/144Nd | Richardson, Stephen H | Isotope ratio mass spectrometry | measured, values are normalized to 143Nd/144Nd=0.51264 for BCR-I (Dosso and Murthy, 1980, doi:10.1016/0012-821X(80)90190-9, Wasserburg et al., 1981, doi:10.1016/0016-7037(81)90085-5) using 146Nd/144Nd=0.7219 (O´Nions et al., 1977, doi:10.1016/0012-821X(77)90100-5) | |
| 14 | Neodymium-143/Neodymium-144 ratio | 143Nd/144Nd | Richardson, Stephen H | Calculated | Initial ratios calculated for an age of 70 m.y. using lambda Rb = 1.42 | |
| 15 | Neodymium-143/Neodymium-144 ratio, error | 143Nd/144Nd e | ± | Richardson, Stephen H | Isotope ratio mass spectrometry | measured |
| 16 | Lead-206/Lead-204 ratio | 206Pb/204Pb | Richardson, Stephen H | normalized for mass fractionation using that obtained for NBS SRM 981. Reproducibility is better than 0.05% amu**-1. In-run precision is on average an order of magnitude better and not reported | ||
| 17 | Lead-207/Lead-204 ratio | 207Pb/204Pb | Richardson, Stephen H | normalized for mass fractionation using that obtained for NBS SRM 981. Reproducibility is better than 0.05% amu**-1. In-run precision is on average an order of magnitude better and not reported | ||
| 18 | Lead-208/Lead-204 ratio | 208Pb/204Pb | Richardson, Stephen H | normalized for mass fractionation using that obtained for NBS SRM 981. Reproducibility is better than 0.05% amu**-1. In-run precision is on average an order of magnitude better and not reported |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
169 data points