Norsk versjon
	THE INDUSTRIAL MINERAL DATABASE
	Occurence 5052 - 302 Leka
	(Object Id: 15073) (Last updated: 09.03.2010)

Mineralization

	Genesis:		Form:
	Main texture:		Min. distribution:

Main grain size:

	Strike/Dip:		Direction:
			Plunge:

Stratigraphic classification of host rock

Era:

Period:

	Province:
	Geotec.unit:
	Tectonic complex:
	Igneous complex:

Group:

Formation:

Bibliography:

From NGU's Reference Archive:

Albrektsen, Bjørn-Atle , 1990

	Geologiske relasjoner og petrogenetisk utvikling i Lauvhatten mantelperidotitt, Leka ofiolittkompleks.

;UiB Geologisk inst. Avd. A;AVHANDLING

Pedersen, Rolf-Birger; Johannesen, Geir Mossige; Boyd, Rognvald , 1993

	Stratiform platinum-group element mineralizations in the ultramafic cumulates of the Leka ophiolite complex, central Norway.

;TIDSSKRIFTARTIKKEL;Economic geology; No.88 (4);782-803 pages

Abstract:

Three types of stratiform platinum-group element (PGE) enrichment have been documented within olivine cummulates of the layered series in the Leka Ophiolite Complex: (1) Os-Ir-Ru enrichments associated with chromite-rich rocks, (2) Pt-dominated enrichments, and (3) Pd-dominated enrichments associated with discrete 10- to 50-cm-thick sulfide-rich horizons. Drill cores across the Pt- and Pd-enriched horizons have yielded 0.5 and 1 m averages of ca. 1 ppm PGE + Au, and hand samples from one of the horizons yielded 3 to 4 ppm PGE. The horizons can be traced laterally for more than 1.5 km. ß autoradiography of core samples shows that the enrichments may be only a few cm thick and that they form well-defined horizons rich in discrete PGE-bearing minerals (mainly alloys of Pt-Fe-Ni and Cu-Au-Pd, tellurides, and antimonides). The PGE enrichments are associated with the bases of macrorythmic units and seem to have formed during, or shortly after, the influx of primitive magma into the chamber. The Pt-Pd-enriched horizons are displaced relatively to chromite horizons, thus explaining why stratiform chromitites in ophiolites, in contrast to many intracratonic layered intrusions, are depleted in Pt and Pd relative to Os, Ir, and Ru. The study demonstrates that ophiolites should not be disregarded as potential sources for Pt and Pd.

Prestvik, T. , 1972

	Alpine-type mafic and ultramafic rocks of Leka, Nord-Trøndelag.

;Norges geologiske undersøkelse;TIDSSKRIFTARTIKKEL;NGU; No.273;23-34 pages

Abstract:

Layered rocks of both ultramafic and gabbroic composition are described. The banding is assumed to be of the flow-layering type typical of alpine-type complexes. The gabbroic rocks are both uralitized and saussuritized. Dunitic ultramafite is more or less serpentinized, whereas the pyroxenite layers are quite fresh. This selective or incomplete alteration may be due to lack of water during metamorphism.

Prestvik, T. , 1980

	The caledonian ophiolite complex of Leka, north central Norway.

;Cyprus Geological Survey Department;ARTIKKEL; FOREDRAG;Extract from Ophiolites, Proceedings International Ophiolite; Symposium, Cyprus 1979.;555-566 pages

Abstract:

A complex of ultramafic rocks, metagabbros and associated volcanic and subvolcanic rocks occupy most of the islands Leka and Madsøya on the coast of north-central Norway. The ultramafic complex includes both nonlayered and layered suquences which are interpreted as tectonite peridotite and ultramafic cumulates respectively. The gabbroic complex is especially in the west layered, but homogenous metagabbros are typically developed towards the east. In this part also basaltic dykes and small plagiogranite lenses occur. The gabbroic complex is followed by a sheeted sill complex and then pillowed greenstones on the easternmost parts of Madsøya. These sequences constitute a nearly completely developed ophiolite complex. Both major and trace element data for all sequences are presented. Clinopyroxenites and metagabbros typically display light REE-depleted patterns. Dykes, sills and greenstones appear to be of ocean floor type. It is concluded that primitive greenstones and fractioned dykes are interrelated by crystal fractionation processes. Furthermore, hornblende and plagioclase fractionation produced slightly enriched light REE patterns in plagiogranite, which is very low in total REE. Finally the regional aspects of the Leka ophiolite is discussed.

Pedersen, Rolf-Birger; Johannesen, Geir Mossige; Boyd, Rognvald , 1993

	Stratiform platinum-group element mineralizations in the ultramafic cumulates of the Leka ophiolite complex, central Norway.

;TIDSSKRIFTARTIKKEL;Economic geology; No.88 (4);782-803 pages

Abstract:

Three types of stratiform platinum-group element (PGE) enrichment have been documented within olivine cummulates of the layered series in the Leka Ophiolite Complex: (1) Os-Ir-Ru enrichments associated with chromite-rich rocks, (2) Pt-dominated enrichments, and (3) Pd-dominated enrichments associated with discrete 10- to 50-cm-thick sulfide-rich horizons. Drill cores across the Pt- and Pd-enriched horizons have yielded 0.5 and 1 m averages of ca. 1 ppm PGE + Au, and hand samples from one of the horizons yielded 3 to 4 ppm PGE. The horizons can be traced laterally for more than 1.5 km. ß autoradiography of core samples shows that the enrichments may be only a few cm thick and that they form well-defined horizons rich in discrete PGE-bearing minerals (mainly alloys of Pt-Fe-Ni and Cu-Au-Pd, tellurides, and antimonides). The PGE enrichments are associated with the bases of macrorythmic units and seem to have formed during, or shortly after, the influx of primitive magma into the chamber. The Pt-Pd-enriched horizons are displaced relatively to chromite horizons, thus explaining why stratiform chromitites in ophiolites, in contrast to many intracratonic layered intrusions, are depleted in Pt and Pd relative to Os, Ir, and Ru. The study demonstrates that ophiolites should not be disregarded as potential sources for Pt and Pd.

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