Publication Type:

Journal Article

Authors:

Lightfoot, P. C.; Hawkesworth, C. J.; Olshefsky, K.; Green, T.; Doherty, W.; Keays, R. R.

Source:

Contributions to Mineralogy and Petrology, Springer International, Heidelberg-New York, International, Volume 128, Number 2-3, p.139-163 (1997)

ISBN:

0010-7999

Keywords:

absolute age, alkaline earth metals, Arctic region, basalts, Cenozoic, chemical composition, copper ores, copper sulfides, crust, dates, Disko Island, economic geology, enrichment, flood basalts, greenland, igneous rocks, Isotopes, Lead, magma contamination, major elements, metal ores, metals, mineral deposits, genesis, mineralization, Nd-144/Nd-143, Nd/Nd, neodymium, nickel ores, ore-forming fluids, Pb-206/Pb-204, picrite, provenance, radioactive isotopes, rare earths, Sr-87/Sr-86, Stable isotopes, strontium, sulfides, Tertiary, tholeiite, ultramafic composition, volcanic rocks, West Greenland

Abstract:

An extensive geochemical and isotopic study of Tertiary ( approximately 68 m.y.) continental flood basalts from Nuussuak and Qeqertarssuaq, W Greenland, is presented. Picrite units are mantle plume-derived and similar to recent Icelandic picrites. Tholeiites show crustal contamination. Two contamination trends are identified: one involving Archaean sediments, and the other Proterozoic (1100 m.y.) meta-igneous material, and affected the Quqertarssuaq and Nuussuak tholeiites, respectively. The contaminated tholeiites are depleted in Cu, Ni (10-50 ppm), and have elevated SiO (sub 2) (50-58 wt.%), La/Sm = 3-7, (super 86) Sr/ (super 87) Sr = 0.70550-0.71224 and (super 141) Nd/ (super 144) Nd = 0.51234-0.51174. Some units also contain native Fe droplets. Depletion in Cu and Ni is attributed to scavenging by magmatic sulphides formed in response to the crustal contamination, triggered by increased SiO (sub 2) , and some addition of crustal S (estimated at approximately 50% of total S). An estimated 230 X 10 (super 6) t of each metal was removed from the lavas. Sulphide formation appears to have occurred at relatively deep levels in the Nuussuak and at relatively shallow levels in the Qeqertarssuaq tholeiites. Intrusions likely to be co-genetic with the lavas in the region were examined, with a view to evaluation as potential exploration targets. A comparison is made with Noril'sk and Talnakh, in which crustal contamination of continental flood basalts has led to the formation of large metal deposits.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2000-042471<br/>Kraulshavn Greenland<br/>Qeqertarssauq