Portal de Periódicos da CAPES

Metadolerite geochronology and dolerite geochemistry from East Finnmark, northern Scandinavian Caledonides

2004; Cambridge University Press; Volume: 141; Issue: 3 Linguagem: Inglês

10.1017/s001675680300788x

1469-5081

A. H. N. Rice, Theodoros Ntaflos, R. A. Gayer, R. D. Beckinsale,

Geochemistry and Geologic Mapping

Dolerite dykes in the East Finnmark Scandinavian Caledonides form three geochemical suites: Digermulhalvøya–Magerøya – WNW–ESE-trending, c . 337–332 Ma, possibly also c . 293 Ma, continental within-plate; East Varangerhalvøya – NE–SW and N–S, c . 376 Ma, continental plate-margin; Styret – NE–SW, also c . 376 Ma, chemically intermediate to the other two groups. New K–Ar data from metadolerites on Varangerhalvøya give a 7-point ‘lower envelope’ isochron of 577 ± 14 Ma (MSWD 1.04). This is concordant with a published upper intercept U–Pb zircon age (567 +30 −23 Ma) from an East Varangerhalvøya dolerite, here re-interpreted to reflect Neoproterozoic basement fracturing contemporaneous with the emplacement of the metadolerites. Intrusion of the younger dolerites at c . 376 Ma reactivated this trend, and may be responsible for the published zircon lower intercept age of 392 +25 −36 Ma. Clarification of the intrusion and structural chronology, integrated with extensive new geochemical data, enables a better understanding of the evolution of this part of the Scandinavian Caledonides.