Origin of the picrite blocks in the Marginal Border Group of the Skaergaard Intrusion, East Greenland

Kays, M. A.; McBirney, Alexander R.

doi:10.1016/0016-7037(82)90287-3

Cited by 20 publications

(10 citation statements)

References 15 publications

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“…The most primitive olivine composition in the Skaergaard intrusion is found in picrite blocks of the MBS. However, Kays and McBirney (1982) concluded that these picrites were more likely to be xenoliths of ultramafic rock from the Archean sequence than autoliths belonging to the intrusion. The Skaergaard olivine compositions are less magnesian than Fo 74 (Hoover 1989b).…”

Section: Discussionmentioning

confidence: 99%

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Parental magma of the Skaergaard intrusion: constraints from melt inclusions in primitive troctolite blocks and FG-1 dykes

Jakobsen

Tegner

Brooks

et al. 2009

Contrib Mineral Petrol

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Troctolite blocks with compositions akin to the Hidden Zone are exposed in a tholeiitic dyke cutting across the Skaergaard intrusion, East Greenland. Plagioclase in these blocks contains finely crystallised melt inclusions that we have homogenised to constrain the parental magma to 47.4-49.0 wt.% SiO 2 , 13.4-14.9 wt.% Al 2 O 3 and 10.7-14.1 wt.% FeO T . These compositions are lower in FeO T and higher in SiO 2 than previous estimates and have distinct La/Sm N and Dy/Yb N ratios that link them to the lowermost volcanic succession (Milne Land Formation) of the regional East Greenland flood basalt province. New major-and trace element compositions for the FG-1 dyke swarm, previously taken to represent Skaergaard magmas, overlap with the entire range of the regional flood basalt succession and do not form a coherent suite of Skaergaard like melts. These dykes are therefore re-interpreted as feeder dykes throughout the main phase of flood basalt volcanism.

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Section: Discussionmentioning

confidence: 99%

“…The darker shaded area represents compositions in MBS from the Banded Division Rocks and Tranquil Division from Hoover (1989b). Perpendicular feldspar rocks from Hoover (1989b) and picrite blocks from Kays and McBirney (1982). Skaergaard chills E.G.…”

Section: Discussionmentioning

confidence: 99%

Parental magma of the Skaergaard intrusion: constraints from melt inclusions in primitive troctolite blocks and FG-1 dykes

Jakobsen

Tegner

Brooks

et al. 2009

Contrib Mineral Petrol

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“…The plug was first described by Kays and McBirney (1982), who considered it to have been the source of abundant picrite blocks in the Marginal Border Series of the Skaergaard intrusion. Although Kays and McBirney (1982) did not specifically address the age, the intrusion was mapped as Precambrian by McBirney (1989). The plug is extensively covered by glacial till and exposed only in outcrops across an area of 600 × 800 m on a small peninsula that protrudes into Watkins Fjord to the north of the Skaergaard intrusion (Fig.…”

Section: Geological Settingmentioning

confidence: 99%

“…The picrite blocks occupy 35-50 vol% of this zone and are intermixed with less abundant blocks of hercynite-bearing metasediment, gneiss, dolerite, and hornfelsed basalt (Wager and Brown 1968;Irvine et al 1998). Kays and McBirney (1982) suggested that the picrite blocks form a continuous compositional succession with the Watkins Fjord wehrlite and that their more evolved compositions developed through equilibration with the Skaergaard magma. The block-rich zone is followed by the crossbedded belt that defines the transition to the Layered Series.…”

Section: Geological Settingmentioning

confidence: 99%

“…They have recently been uncovered by glacial retreat and may originally have been at the basal margin of the intrusion. The occurrences are near exposures of the Watkins Fjord wehrlite, a small plug-like intrusion that Kays and McBirney (1982) identified as the source for abundant picrite xenoliths in the Skaergaard Marginal Border Series (MBS). Our aim is to describe the occurrences and establish if they represent previously unrecognized mineralization along the Skaergaard margin or whether they formed in relation to the Watkins Fjord wehrlite plug.…”

Section: Introductionmentioning

confidence: 99%

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Platinum-group mineralization at the margin of the Skaergaard intrusion, East Greenland

et al. 2017

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Two occurrences of platinum-group elements (PGEs) along the northern margin of the Skaergaard intrusion include a sulfide-bearing gabbro with slightly less than 1 ppm PGE + Au and a clinopyroxene-actinolite-plagioclase-biotiteilmenite schist with 16 vol% sulfide and 1.8 ppm PGE + Au. Both have assemblages of pyrrhotite, pentlandite, and chalcopyrite typical for orthomagmatic sulfides. Matching platinumgroup mineral assemblages with sperrylite (PtAs 2 ), kotulskite (Pd(Bi,Te) 1-2 ), froodite (PdBi 2 ), michenerite (PdBiTe), and electrum (Au,Ag) suggest a common origin. Petrological and geochemical similarities suggest that the occurrences are related to the Skaergaard intrusion. The Marginal Border Series locally displays Ni depletion consistent with sulfide fractionation, and the PGE fractionation trends of the occurrences are systematically enriched by 10-50 times over the chilled margin. The PGE can be explained by sulfide-silicate immiscibility in the Skaergaard magma with R factors of 110-220. Nickel depletion in olivine suggests that the process occurred within the host cumulate, and the low R factors require little sulfide mobility. The sulfide assemblages are different to the chalcopyrite-bornite-digenite assemblage found in the Skaergaard Layered Series and Platinova Reef. These differences can be explained by the early formation of sulfide melt, while magmatic differentiation or sulfur loss caused the unusual sulfide assemblage within the Layered Series. The PGEs indicate that the sulfides formed from the Skaergaard magma. The sulfides and PGEs could not have formed from the nearby Watkins Fjord wehrlite intrusion, which is nearly barren in sulfide. We suggest that silicate-sulfide immiscibility led to PGE concentration where the Skaergaard magma became contaminated with material from the Archean basement.

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Isotopic studies of processes in mafic magma chambers: II. The Skaergaard Intrusion, East Greenland

Stewart

DePaolo

1990

Contr. Mineral. and Petrol.

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Origin of the picrite blocks in the Marginal Border Group of the Skaergaard Intrusion, East Greenland

Cited by 20 publications

References 15 publications

Parental magma of the Skaergaard intrusion: constraints from melt inclusions in primitive troctolite blocks and FG-1 dykes

Parental magma of the Skaergaard intrusion: constraints from melt inclusions in primitive troctolite blocks and FG-1 dykes

Platinum-group mineralization at the margin of the Skaergaard intrusion, East Greenland

Isotopic studies of processes in mafic magma chambers: II. The Skaergaard Intrusion, East Greenland

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