Early Tertiary basalts from the Labrador Sea floor and Davis Strait region

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Clarke, D. B., Cameron, B. I., Muecke, G. K., Bates, J. L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1989
• Subjects: General Earth and Planetary Sciences; Baffin Island; Greenland; Baffin; Davis Strait; Labrador Sea
• Online Access: http://dx.doi.org/10.1139/e89-077; http://www.nrcresearchpress.com/doi/pdf/10.1139/e89-077

Fine- to medium-grained, phyric and aphyric basalt samples from ODP Leg 105, site 647A, in the Labrador Sea show little evidence of alteration. Chemically, these rocks are low-potassium (0.01–0.09 wt.% K 2 O), olivine- to quartz-normative tholeiites that compare closely with the very depleted terrestrial Paleocene volcanic rocks in the Davis Strait region of Baffin Island and West Greenland. However, differences exist in the Sr–Nd isotope systematics of the two suites; the Labrador Sea samples have ε Nd values (+9.3) indicative of a more depleted source, and are higher in 87 Sr/ 86 Sr (0.7040), relative to the Davis Strait basalts (ε Nd +2.54 to +8.97; mean 87 Sr/ 86 Sr 0.7034). The higher 87 Sr/ 86 Sr in the Labrador Sea samples may reflect seawater exchange despite no petrographic evidence for significant alteration. The Labrador Sea and early Davis Strait basalts may have been derived from a similar depleted mantle source composition; however, the later Davis Strait magmas were generated from a different mantle. None of the Baffin Island, West Greenland, or Labrador Sea samples show unequivocal geochemical evidence for contamination with continental crust.