Palaeomagnetism of the Rogaland precambrian (southwestern Norway)

Poorter, R.P.E.

doi:10.1016/0031-9201(72)90086-6

Cited by 53 publications

(19 citation statements)

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“…As has characteristic NRM of the amphibolite and hyperbeen argued by Poorter (1972), the latter age is in ite rocks from the Bamble and Kongsberg areas and better agreement with the palaeomagnetic evidence. from SW Sweden originated during the post.SvecoThe two hyperite dikes sampled for this study are cutnorwegian period of uplift and cooling.…”

Section: Zha Down!) \ 1°a~\ /supporting

confidence: 69%

“…Previous palaeomagnetic investigations of rocks O'Nions and Heier (1972) carried out a reconnaisfrom the Sveconorwegian zone have been carried out sance geochronological study on rocks from the Kongson basement rocks and dolerite dikes of Rogaland, berg area and determined a metamorphic event at SW Norway (Storetvedt, 1965;Storetvedt and Gidske-1,260-106 year; the authors considered this to be haug, 1968; Hargraves and Fish, 1971;Poorter, 1972), coeval, within the analytical error, with the thermal on a dolerite dike in SW Sweden (Abrahamsen, 1974) maximum of the Sveconorwegian metamorphic epiand on hyperite dikes within the schistosity zone of sode in the Bamble area. S Sweden (Priem et al, 1968;Mulder, 1971).…”

Section: Introductionmentioning

confidence: 99%

“…McElhinny (1973), presuming a The sampling and measuring techniques have been direct relation between the susceptibility anisotropy described previously (Poorter, 1972). For most speciand the deflection of the remanent magnetization, mens the astatic magnetometer was used, but a numcalculated a maximum deflection of 2.7°for 10% As (1967).…”

Section: Introductionmentioning

confidence: 99%

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Palaeomagnetism of Precambrian rocks from Southeast Norway and South Sweden

Poorter

1975

Physics of the Earth and Planetary Interiors

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Precambrian amphibolite and hyperite rocks from the Bamble and Kongsberg areas in SE Norway, and amphibolite rocks from SW Sweden were investigated for evidence of remagnetization by the Sveconorwegian metamorphic episode. The similarity of the characteristic natural remanent magnetization directions, shown by the various rocks from the Bamble and Kongsberg areas, indeed supports the idea of remagnetization on a regional scale. Therefore the average pole position at 3°S, 15 3°W,determined from six sites in these areas, is considered to reflect the average virtual pole position for the post-Sveconorwegian period of uplift and cooling (1,120-975) 106 year ago. The pole positions determined from the characteristic natural remanent magnetization directions of amphibolite rocks in SW Sweden are indicative of being somewhat younger.In addition, two hyperite dikes were studied near Karlshamn in SE Sweden. Their characteristic natural remanent magnetization is consistent with that of the hyperite dikes in central south Sweden (Mulder, 1971).The Precambrian apparent polar wandering path for Europe is reconstructed on the basis of twenty-three pole positions from the Baltic Shield and three pole positions from Great Britain. This pole path requires an average angular rate of apparent polar wandering of 0.2-0.3°per 106 year.

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Section: Zha Down!) \ 1°a~\ /supporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

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Palaeomagnetism of Precambrian rocks from Southeast Norway and South Sweden

Poorter

1975

Physics of the Earth and Planetary Interiors

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“…Cumulus plagioclase grains are strained or recrystallized to shape-oriented polygonal aggregates, while prismatic Ca-poor pyroxenes are commonly kinked or bent. Uniform paleomagnetic vectors in different parts of the intrusion (Poorter, 1972) suggest that the deformation and development of the synformal disposition of the layering took place at temperatures in excess of the Curie point (550-650°C). Michot and Michot (1970) and others have attempted to relate the deformation to a late expression of the Sveconorwegian Orogeny.…”

Section: The Form Of the Bjerkreim-sokndal Intrusionmentioning

confidence: 99%

The Bjerkreim-Sokndal Layered Intrusion, Southwest Norway

Wilson

Robins

Nielsen

et al. 1996

Developments in Petrology

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The Bjerkreim-Sokndal Layered Intrusion is a large (~230 km 2 ), discordant, Late Protero-zoic, post-orogenic pluton in the Egersund-Farsund Igneous Province. The intrusion was em-placed shortly after massif-type anorthosite plutons and is cut by jotunite dykes. It contains a >7000 m thick Layered Series consisting of rocks belonging to the anorthosite kindred: andes-ine anorthosite, leuconorite, troctolite, norite, gabbronorite, mangerite, and quartz mangerite. Cumulates in the Layered Series are organized in 6 megacyclic units (MCU 0 to IV), individually up to 1800 m thick, but varying considerably in thickness and development along strike. The highest-temperature cumulates are troctolites containing plagioclase of ~An 54 and olivine of ~Fo 77 · Phase contacts in the macrocyclic units reflect crystallization of the silicate minerals in the order plagioclase (± olivine), orthopyroxene, Ca-rich pyroxene, pigeonite. Il-menite crystallized early and apatite appeared as a cumulus mineral at about the same time as Ca-rich pyroxene. Cumulus magnetite followed orthopyroxene and preceded Ca-rich pyroxene in MCU III and ΓV, but crystallized after Ca-rich pyroxene in MCU IB. MCUs 0, IA and II do not contain cumulates with cumulus magnetite or Ca-rich pyroxene. Olivine (~Fo 50 ) reappears in the uppermost part of the Layered Series where there is a rapid stratigraphic transition to mangerite and quartz mangerite. The basal parts of MCUs III and ΓV are characterized by thin sequences of plagioclase, plagioclaseorthopyroxene-ilmenite and orthopyroxene-ilmenite cumulates in which there are systematic upward decreases in initial Sr isotope ratios. They are overlain by troctolite (plagioclase-olivine cumulate) and are believed to have crystallized from hybrid magmas. The MCUs, the discordant geometry of phase contacts, the stratigraphic variations in initial 87 Sr/ 86 Sr ratio (0.7049-0.7085), and the abundance of xenoliths suggest crystallization of the cumulates at the base of a periodically-replenished, compositionally-zoned magma chamber that was continually assimilating country rocks. The parent, as indicated by medium-grained jotunite along country-rock contacts, appears to have been an evolved, Ti-rich magma similar to ferrobasalt, but poor in diopside components. Systematic stratigraphic variations in initial 87 Sr/ 86 Sr ratio at the base of MCU IΠ and MCU IV suggest that influx of magma into the chamber was accompanied by mixing with resident, contaminated magma.

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“…The precise age of intrusion is unknown, but the dykes cut all other formations in the area which have ages > 850 Ma (Pasteels and Michot, 1975;Priem, 1980;Wielens et at., 1981). A single K-At age of 663 Ma has been reported for one of the dykes (Versteeve, 1975) and palaeomagnetic data (Storetvedt and Gidskehaug, 1968;Poorter, 1972) support a late Precambrian age.…”

Section: Copyright the Mineralooical Societymentioning

confidence: 98%

Secondary ilvaite in a dolerite dyke from Rogaland, SW Norway

Bartoň

Bergen

1984

Mineral. mag.

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A BST R ACT. llvaite is an alteration product of carbonate, which itself replaced clinopyroxene, in a Precambrian tholeiitic dyke. Additional secondary minerals are ferroactinolite, cummingtonite, chlorite, biotite, prehnite, and epidote. Microprobe analyses demonstrate that the ilvaite is close to the ideal end-member composition [CaFe22" Fe3+Si2Os(OH)] and that only cummingtonites, Mg/(Mg+Fe 2+) 0.77-0.39, and carbonates (solid solutions between calcite and dolomite, dolomite and ankerite, magnesite and siderite) show significant compositional variations. It is estimated that ilvaite formed at temperatures < 470 ~ and at pressures < 2 kbar, probably during a low-grade metamorphic event (or events) associated with the Caledonian orogeny. The fluids involved in the alteration process contained both CO2 and HzO, initial fluids probably being richer in CO2 than later ones. Ilvaite may be more common in hydrothermally altered igneous rocks than previously supposed.

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Palaeomagnetism of the Rogaland precambrian (southwestern Norway)

Cited by 53 publications

References 12 publications

Palaeomagnetism of Precambrian rocks from Southeast Norway and South Sweden

Palaeomagnetism of Precambrian rocks from Southeast Norway and South Sweden

The Bjerkreim-Sokndal Layered Intrusion, Southwest Norway

Secondary ilvaite in a dolerite dyke from Rogaland, SW Norway

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