| 1. |
- Romer, RL, et al.
(författare)
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Crystal-chemical and genetic controls of U-Pb systematics of columbite-tantalite
- 1996
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Ingår i: MINERALOGY AND PETROLOGY. - : SPRINGER-VERLAG WIEN. - 0930-0708. ; 57:3-4, s. 243-260
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Columbite-tantalite can accommodate considerable amounts of uranium and excludes lead almost completely. It is thus potentially suited for U-Pb elating. Discordias generally yield closely constrained upper intercept ages. Yet, in a few cases, the U-Pb sys
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| 2. |
- Romer, RL, et al.
(författare)
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U-Pb columbite ages of pegmatites from Sveconorwegian terranes in southwestern Sweden
- 1996
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Ingår i: PRECAMBRIAN RESEARCH. - : ELSEVIER SCIENCE BV. - 0301-9268. ; 76:1-2, s. 15-30
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Post-kinematic and post-metamorphic rare-mineral pegmatites in the Sveconorwegian Province of southwestern Sweden yield U-Pb columbite ages at 1041.4 +/- 1.6 Ma (2 sigma), 1038.7 +/- 3.4 Ma, 1029.7 +/- 1.4 Ma, and 984.3 +/- 6.4 Ma. The contrasting age of
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| 3. |
- Eriksson, Martin
(författare)
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Registrerade romer
- 2013
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Romer, Rolf
(författare)
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Contiguous Laurentia and Baltica before the Grenvillian-Sveconorwegian orogeny?
- 1996
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 8:2, s. 173-181
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Tidskriftsartikel (refereegranskat)abstract
- Close geochronological correspondence of Mesoproterozoic extension-related magmatism and comparable tectonic and geochronological evolution of the Grenville and Svecononvegian orogens suggests that the Laurentian and Baltic Shields could have been joined during the Mesoproterozoic and did not separate until after the Grenvillian-Sveconorwegian orogeny. The combined Grenville-Svecononvegian orogen is here interpreted to have formed during the collision of coherent Laurentia-Baltica with an unknown craton, which is in contrast to earlier explanations that favour a late-Mesoproterozoic rotation between Laurentia and Baltica followed by collision of these two cratons with each other
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| 8. |
- Romer, Rolf
(författare)
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Disturbance of Pb, Sr, and Nd isotope systems related to medium and low grade metamorphism illustrated with data from the polymetamorphic Early Proterozoic (Rombak) - Sjangeli basement window of the Caledonides of Northern Sweden
- 1988
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Sjangeli supracrustal belt forms the easternmost belt of a series approximately N-S striking, steeply dipping Early Proterozoic belts of the Rombak-Sjangeli basement window, which formed in an island arc setting. The volcanic units of the Sjangeli area consist of metatuffs, which contain abundant Cu-mineralizations, metalava flows and pillowed metalavas and are intercalated with banded carbonatesilicate rocks and micaschists, which contain various amounts of volcanic material. The volcanic rocks are basic to ultrabasic and consist predominantly of high-Mg tholeiitic basalts which vary to komatiitic basalts, and minor serpentinites and high-Fe tholeiitic basalts, which probably originated from extensive melting of a depleted mantle source. This is indicated by high contents of MgO Ni, and Cr, the flat REE pattern, and TiO2/P2O5 , Ti/Zr, and platinum group element ratios, and positive δNd values. Rb-Sr whole-rock isotope data from the metalava flows and from a basic metadike yield ages of 2324 ± 15 My and 2252 ± 71 My, respectively. Mixing plots indicate, however, that these data could be too high by 100 to 150 My. The supracrustal rocks became intruded by syenites and granites at c. 1.7 - 1.8 AE, and were subjected to an amphibolite facies metamorphism which, in the basic rocks, resulted in a mineral assemblage consisting of hornblende + andesine + ilmenite + (biotite) ± quartz ± calcite ± epidote + magnetite. This assemblage indicates metamorphic conditions of c. 6 kbar and c. 560°C. Mylonitic zones, which predominantly occur at unit contacts, show retrogradation to a greenschist facies mineral paragenesis consisting of actinolite + albite + quartz + biatite + epidote + chlorite + calcite + titanite which probably formed at c. 4 kbar and c. 480°C. The mylonites represent Proterozoic structures and their retrogradation occurred during the Svecokarelian metamorphism at c. 1.6 - 1.8 AE. The Caledonian overthrust, which followed a phase of deep erosion and discordant sedimentation of Cambrian epiclastic sediments, reached greenschist facies conditions. Rb-Sr whole-rock isotope data from the metatuffs define a mixing line with an apparent age of 488 ± 64 My. Mixing diagrams indicate c. 400 My as time of mixing. The resulting greenschist facies mineral assemblages therefore had formed during two completely different metamorphisms. Both greenschist facies metamorphic events were associated with disturbances of the isotopic systems, which resulted from infiltration of U, Th, and Pb at c. 430 My and at c. 1800 My, and the mobilization of Sr. The isotopic remobilization of the greenschist facies metamorphism resulted in a partial homogenization, causing mineralwhole-rock systems to be in isotopic disequilibrium. The mixing of the Sr whole-rock system and the addition of U, Th, and radiogenic Pb are strongest in the metatuffs which are strongly mylonitized. In the little or non-schistose metalava flows the addition of radiogenic lead is minor and the Rb-Sr system is apparently not disturbed by the metamorphic events. The amphibolites, which are the least deformed unit with the highest grade mineral assemblage, show the least radiogenic lead composition.
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| 9. |
- Romer, Rolf, et al.
(författare)
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Implications of U-Pb ages of columbite-tantalites from granitic pegmatites for the Palaeoproterozoic accretion of 1.90-1.85 Ga magmatic arcs to the Baltic Shield
- 1994
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268 .- 1872-7433. ; 67:1-2, s. 141-158
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Tidskriftsartikel (refereegranskat)abstract
- The Palaeoproterozoic growth of the Baltic Shield involved the accretion of several ~1.90-1.85 Ga old magmatic arcs to the southwest of the Archaean craton and the deformation and migmatization of sedimentary basins located between the arcs. During crustal thickening after the collision of the arcs, the sedimentary basin fill became intruded by peraluminous two-mica granites. Locally, columbite-bearing pegmatites are genetically associated with these granites. Columbites from lithium-cesium-tantalum-type (LCT-type) pegmatites from the Stockholm area (Sormland gneisses) yield U-Pb ages at 1815-1820 Ma, while niobium-yttrium-fluorine-type (MYF-type) pegmatites from the same area are younger (1795±2 Ma, 2σ). Farther to the north, LCT-type pegmatites from the central Bothnian Basin, that correspond geochemically and mineralogically to those of the Stockholm area, yield U-Pb columbite ages at 1795-1800 Ma, while LCT-type pegmatites in the sedimentary basin between Skelleftea and Lulea yield less well constrained U-Pb columbite ages at 1765-1775 Ma. LCT-type pegmatites are mainly associated with crustal melts that form during postcollisional thickening of continental crust. They represent markers for the time when the Palaeoproterozoic Baltic Shield suffered sufficient thickening to yield voluminous anatectic melts. The U-Pb columbite ages from the LCT-type pegmatites indicate that comparable phases of postcollisional crustal thickening of the Svecofennian area of the Baltic Shield occurred later to the north
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| 10. |
- Romer, Rolf, et al.
(författare)
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Interpretation of lead isotope data from the uraniferous Cu-Fe-sulfide mineralizations in the proterozoic Greenstone Belt at Kopparasen, northern Sweden
- 1988
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Ingår i: Mineralium Deposita. - 0026-4598 .- 1432-1866. ; 23:4, s. 256-261
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Tidskriftsartikel (refereegranskat)abstract
- The polymetamorphic Early Proterozoic basic metavolcanites of the Kopparasen greenstone belt, northern Sweden, contain U mineralizations which are confined to Cu-Fe-sulfide mineralizations in mylonitized zones within basic metatuffs and graphite-bearing mica schists. Tracelead isotope data from sulfides indicate contamination of the sulfide lead with two different lead components at ca. 430 Ma. One lead component was leached from rocks with a 232Th/238U ratio of 3.0-3.2, while the other lead component had evolved in a environment with a lower 232Th/238U ratio (0.0-0.05). The source for this latter lead component underwent a U-Th separation, probably in relation to the formation of the U mineralizations. If this lead component was leached from the U mineralizations, these mineralizations have a 207Pb/206Pb model age of ca. 1,780 Ma, which is less than the least radiogenic lead model age of the supracrustal belt (ca. 2,050 Ma). A possible genetic model for the uranium mineralizations includes the transport of U with an oxidized metamorphic fluid, which was channelled into the permeable zones, and the local reduction of the fluid by sulfides, which caused the precipitation of U.
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