|
| << vorige | volgende >> |
Tijdschrift beschrijving
Alle jaargangen van het bijbehorende tijdschrift
Alle afleveringen van het bijbehorende jaargang
Alle artikelen van de bijbehorende aflevering
Details van artikel 4 van 6 gevonden artikelen
| Titel: |
Emplacement mechanism and thermobarometry of the Sveconorwegian Bohus granite, SW Sweden |
| Auteur: |
Eliasson, Thomas Ahlin, Stellan Petersson, Jesper |
| Verschenen in: |
GFF |
| Paginering: | Jaargang 125 (2003) nr. 3 pagina's 113-130 |
| Jaar: |
2003-09-01 |
| Inhoud: |
The 920 Ma, post-kinematic Sveconorwegian (Grenvillian) Bohus granite of south-western Sweden was principally emplaced along a gently easterly dipping weakness zone at mesozonal brittle crustal depth, in an extensional stress regime. The fusion of the protolith gneisses was facilitated by a Sveconorwegian post-orogenic uplift which accelerated the dehydration melting of biotite. The crystalrich magma surges crystallised predominantly as biotite monzogranites, locally rich in secondary muscovite. Biotite + muscovite assemblage became stable in the late magmatic stage, principally in the pegmatitic-aplitic facies. Amphibolite facies para and orthogneiss xenoliths are very frequent in the northern part of the granite massif, where they are interpreted to represent remnants of a giant, brecciated roof pendant. Contact metamorphic transformation of large paragneiss xenoliths, at a specific locality, Tjarno island, enables garnet-biotite geothermometry and garnet-plagioclase geobarometry studies of physical emplacement conditions during intrusion of the granite. Garnet-bearing Bohus granite samples from four additional localities were also used for the geothermobarometric calculations. Element partitioning in garnet-biotite indicate that the temperature of intrusion was at least 715d`C and the final crystallisation (solidus) temperature 670-680d`C. Garnets in the granite and the granofelsic xenolith are low-calcium almandine-spessartines, in contrast to the generally calcium-rich almandinetype garnets of the metamorphic rocks of SW Sweden. Pressure is determined with the independant approaches of quartz + muscovite + biotite + plagioclase + garnet and garnet-only Gd/Dy geobarometry, supported by evaluation of emplacement features and mineral assemblages. Pressure is found to have been c. 4 kbar or slightly higher during the final crystallisation of the Bohus granite, corresponding to depths of c. 15 km. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 4 van 6 gevonden artikelen
| << vorige | volgende >> |