Strontium,lead and oxygen isotopic investigation of the Skaergard intrusion,East Greenland

New Pb, Sr and O isotopic analyses of rocks from the Skaergard intrusion indicate the following: (1) initial⁸⁷Sr/⁸⁶Sr of the gabbroic magma was less than or equal to 0.7041; (2) limited contamination of magma with crustal Sr and Pb may have occurred in a deep reservoir below the presently exposed parts of the intrusion; (3) marked crustal contamination occurred at high level in marginal border group rocks, but these rocks effectively shielded the main magma body from further interaction with country rock gneisses; (4) subsolidus interaction between Skaergard gabbros and hydrothermal fluids modified δ¹⁸O values but had little effect on Sr and perhaps Pb isotopic ratios; (5) late-stage melanogranophyres may be comagmatic with the Skaergard magma, but silicic granophyres are not; (6) silicic granophyres contain large and varied proportions of crustal Sr and Pb; some may be largely anatectic melts derived from the deep crust whereas others may represent mixing of such anatectic melts with late-stage differentiated liquids of the Skaergard intrusion (e.g. Sydtoppen sill).