The structure and intrusive mechanism of the Kap Edvard Holm layered gabbro complex, East Greenland

Elsdon, R.

doi:10.1017/s0016756800051700

Cited by 19 publications

(11 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Examples of such peripheral deformation are known from mafic intrusions elsewhere, notably in certain instances where the original relations of an intrusion do not seem to have been complicated by subsequent regional deformation (e.g. Bichan 1970;Elsdon 1969;Wads worth 1963). Ramberg (1967) has suggested that large mafic intrusions should show a tendency to subside into less dense surrounding rocks after emplacement, thereby developing contacts that are concave upwards as the result of greater subsidence under the thicker, central portion of the original lens-like intrusion.…”

Section: Discussionmentioning

confidence: 99%

Deformation of the Belhelvie Mass, Aberdeenshire

Boyd

Munro²

1978

SJG

View full text Add to dashboard Cite

SYNOPSISEvidence of shearing and mylonitization has been found to occur widely within and around the body of mafic and ultramafic igneous rocks that forms the Belhelvie intrusion. It is inferred that the original relations of these rocks were greatly disturbed when this deformation occurred and that the igneous mass has been largely detached from the country rocks into which it was emplaced and now has a complex structure. This disruption appears to have mainly occurred within 30 m.y. of the emplacement of the magma, but does not seem to be simply related to the development of the Buchan Anticline, the major, post-magmatic structure that earlier workers envisaged as occurring in this area.

show abstract

Section: Discussionmentioning

confidence: 99%

Deformation of the Belhelvie Mass, Aberdeenshire

Boyd

Munro²

1978

SJG

View full text Add to dashboard Cite

show abstract

“…However, the precise tectonic setting of this oceanic crust prior to obduction has been the subject of animated debate, with possibilities revolving around normal mid-ocean ridge, back-arc basin or 'subduction related' environments (Alabaster, Pearce & Malpas, 1982;Browning, 1984;Casey et al 1985;Ernewein, Pflumio & Whitechurch, 1988). This paper Elsdon (1969) and Deer & Abbott (1965), dotted lines; and the present division LLS-MLS, dash-dot line. (Based on Kempe, Deer & Wager, 1970;Abbott & Deer, 1972;Gleadow & Brooks, 1979;Brooks & Nielsen, 1982.)…”

Section: Introductionmentioning

confidence: 94%

“…Exposure is about 20% because of extensive ice cover. Based on variations in mineral chemistry and in orientation of the layering, the Kap Edvard Holm Layered Series is divided into a Lower Layered Series, a Middle Layered Series and an Upper Layered Series (Deer & Abbott, 1965;Elsdon, 1969). Based on variations in mineral chemistry and in orientation of the layering, the Kap Edvard Holm Layered Series is divided into a Lower Layered Series, a Middle Layered Series and an Upper Layered Series (Deer & Abbott, 1965;Elsdon, 1969).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An ocean-ridge type magma chamber at a passive volcanic, continental margin: the Kap Edvard Holm layered gabbro complex, East Greenland

et al. 1992

View full text Add to dashboard Cite

The gabbros of the Tertiary Kap Edvard Holm Layered Series have a stratigraphic thickness of more than 5000 m. Earlier work has shown that the range in cumulus mineral compositions is restricted (plagioclase An 81 -An 51 ; olivine Fo 85 -Fo 66 ; pyroxenes Ca 4 3Mg 4e Fe n to Ca 43 Mg 3 ,Fe 20 ). Field evidence of magma injections is common, which together with the restricted range in mineral chemistry suggests that the magma chamber was frequently replenished by a less fractionated magma. A detailed study of a 600 m section (900-1500 m) in the Lower Layered Series reveals a period of crystallization when the magma chamber behaved as a closed system (900-1300 m). The rocks formed during this period are well-laminated olivine-gabbros (900-110 m), which evolved to well-laminated oxide-gabbros (1100-1300 m). Compositional trends in the cumulus minerals are towards more evolved compositions (plagioclase An 64 -An 58 , pyroxene Mg# from 80 to 76) with stratigraphic height. From 1300 m to 1500 m, granular olivine-gabbros dominate, with more primitive mineral compositions (plagioclase An 67 -An 7(i , pyroxene Mg# from 78 to 82). The transition olivine-gabbro to oxide-gabbro at 1100m is a consequence of fractional crystallization, and it is shown how changes in activities of FeO and Fe 2 O 3 in the magma are reflected in the total iron content of plagioclases. The transition from oxide-gabbro to olivine-gabbro at 1300 m results from replenishment by less evolved basaltic magma. On the basis of calcic pyroxene chemistry and the mineral crystallization sequence it is concluded that the Kap Edvard Holm Layered Series crystallized from a tholeiitic magma similar to MORB. Melanogabbroic units occur throughout the intrusion as discordant to subconcordant sill-like bodies 0.2-2.0 m thick. The melanogabbroic units consist of Crrich augite-olivine-plagioclase heteradcumulates and contain deformed mica crystals of preemplacement origin. These units crystallized from a wet, MgO-rich magma which was injected into the layered host gabbros after the formation of the cumulus pile, but before the magma was completely solidified.The Kap Edvard Holm Layered Series has several parallels with the plutonic part of ophiolite sequences. These include: cumulus mineral assemblage, compositions of the minerals and the restricted range in compositions with stratigraphic height; field evidence of repeated replenishment of basaltic magma; dyke swarms overlying the roof zone of the magma chamber; and the existence of a late intrusive suite of wet, MgO-rich magma. These parallels suggest that the processes involved in the formation of the Kap Edvard Holm Layered Series were similar to those involved in the formation of the crustal part of many ophiolites and beneath present-day spreading ridges. The Kap Edvard Holm Layered Series is therefore believed to represent a shallow-level magma chamber which acted as a reservoir for basaltic flows at the continental margin during the opening of the North Atlantic Ocean. t Present address: Department of Earth Sc...

show abstract

“…In size, shape, structure and composition, the Kruuse Fjord Gabbro Complex most closely resembles the nearby Kap Edvard Holm Complex (Brooks & Nielsen, 1982;Deer & Abbott, 1965;Elsdon, 1969;Abbott & Deer, 1972;Bernstein et al 1992). Both complexes are dominated by layered gabbroic and troctolitic rocks that formed by repeated magma injections and fractionation in an open-system magma chamber.…”

Section: D Comparison With Other Gabbroic Intrusions In East Greenmentioning

confidence: 81%

Petrology and geochemistry of the Kruuse Fjord Gabbro Complex, East Greenland

Arnason

Bird

Bernstein³

et al. 1997

Geol. Mag.

View full text Add to dashboard Cite

The Kruuse Fjord Gabbro Complex is a composite intrusion of layered gabbro and troctolite with subordinate ultramafic rocks and minor trondhjemitic bodies. It was emplaced into Archaean continental crust of East Greenland during early Tertiary rifting of Greenland from Eurasia. The work to date has identified an outer gabbro series and an inner troctolite series, and these are separated by a narrow zone of trondhjemitic intrusions. In the southeast, the partially crystallized cumulates of the gabbro series were intruded by a lenticular, ultramafic pluton 800 m in thickness. Volumetrically minor, syenite–trachyandesite net-veined dykes and later, diabase dykes cross-cut the plutonic rocks. Structural and topographic features suggest that the layered rocks were affected by synmagmatic subsidence and deformation but not by monoclinal coastal flexure.The gabbro series is composed of a marginal gabbro unit, about 20 m wide, bordering more than a 2 km thickness of layered olivine and magnetite gabbro cumulates. The marginal gabbro is interpreted to be chilled magma. The layered cumulates are the product of repeated injections of magma that fractionated in an open-system magma chamber. Anorthositic and troctolitic layers in the lower part of the sequence may represent inputs of magma and suggest that the order of cumulus mineral crystallization was (1) plagioclase (An39–85), (2) olivine (Fo46–82), (3) augite (Wo28–47En39–58Fs8–18 ) and (4) magnetite. The disappearance of cumulus magnetite and a reversal in mineral compositions at 1.5 km from the base of the succession suggests a major input of magma occurred at this height. In the troctolite series, the composition of cumulus minerals, mineral crystallization sequence and style of emplacement are similar to those in the gabbro series. The ultramafic pluton is composed of coarse-grained wehrlite, olivine melagabbro and troctolite that were formed by at least three injections of magma. The typical mineral crystallization sequence was (1) cumulus chromite and olivine (Fo84–88); (2) poikilitic chrome diopside (Wo29–51En43–63Fs3–13 ); and (3) intercumulus plagioclase (An75–90), phlogopite, apatite and localized disseminated sulphides containing Au and platinum-group elements.Comparison of crystallization sequences and the major and trace element compositions of clinopyroxene suggests that the gabbroic and troctolitic rocks formed from a magma represented by the chilled marginal gabbro, a tholeiitic basalt magma similar to E-MORB, whereas the ultramafic rocks formed from a magma that was relatively enriched in incompatible trace elements and volatiles. The association of these two magma types is an example of bimodal mafic–ultramafic magmatism in a rifting environment.

show abstract

The structure and intrusive mechanism of the Kap Edvard Holm layered gabbro complex, East Greenland

Cited by 19 publications

References 4 publications

Deformation of the Belhelvie Mass, Aberdeenshire

Deformation of the Belhelvie Mass, Aberdeenshire

An ocean-ridge type magma chamber at a passive volcanic, continental margin: the Kap Edvard Holm layered gabbro complex, East Greenland

Petrology and geochemistry of the Kruuse Fjord Gabbro Complex, East Greenland

Contact Info

Product

Resources

About