Basalt samples recovered from the lowermost 37 m of Leg 105 Hole 647A in the Labrador Sea are fine- to medium-grained, have microphenocrysts of clinopyroxene, and show little evidence of alteration. Chemically, these rocks are low potassium (0.01-0.09 wt % K20), olivine- to quartz-normative tholeiit...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.629.2065 http://www-odp.tamu.edu/publications/105_SR/VOLUME/CHAPTERS/sr105_46.pdf |
| Summary: | Basalt samples recovered from the lowermost 37 m of Leg 105 Hole 647A in the Labrador Sea are fine- to medium-grained, have microphenocrysts of clinopyroxene, and show little evidence of alteration. Chemically, these rocks are low potassium (0.01-0.09 wt % K20), olivine- to quartz-normative tholeiites that are also depleted in other incompatible ele ments. In terms of many of the incompatible trace elements, the Labrador Sea samples are similar both to iV-type mid-ocean ridge basalts (MORBs) and to the terrestrial Paleocene volcanic rocks in the Davis Strait region of Baffin Island and West Greenland. However, significant differences are found in their strontium and neodymium isotope systematics. Hole 647A samples are more depleted in eNd (+ 9.3) and are anomalously rich in 87Sr/86Sr (0.7040) relative to the Davis Strait basalts (eNd +2.54 to + 8.97; mean 87Sr/86Sr, 0.7034). We conclude that the Hole 647A and Davis Strait basalts may have been derived from a similar depleted mantle source composition. In addition, the Davis Strait magmas were generated from mantle of more than one composition. We also suggest that there is no geochemical evidence from the Hole 647A samples to support or to refute the existence of foundered continental crust in the Labrador Sea. |
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