Pumpellyite-bearing Precambrian rocks and post-Svecokarelian regional metamorphism in central Sweden

Abstract

Pumpellyite-bearing mineral assemblages, formed during one or more episodes of non-deformational regional metamorphism, have been found in post-Svecokarelian rocks of central Sweden. Two different sub-greenschist facies have been established: the prehnite-pumpellyite and the pumpellyite-actinolite facies, in Jotnian and sub-Jotnian rocks respectively. It is here suggested that the common overprinting of post-deformational ‘retrograde’ minerals on amphibolite facies assemblages in Svecokarelian rocks of central Sweden could, at least in part, be attributed to the metamorphic episode(s) mentioned above. Furthermore, ‘deuteric’ minerals in granitoids of the same area could have the same origin.

Keywords:

• Pumpellyite
• prehnite
• sub-greenschist facies
• low-grade metamorphism
• prograde metamorphism
• retrograde metamorphism
• burial metamorphism
• Upper Dala
• Formation
• sub-Jotnian
• Jotnian
• Svecokarelian
• Precambrian
• Älvdalen
• Svärdsjö
• Gävle
• Granholmen
• southern Härjedalen
• Dalarna
• central Gästrikland
• southern Västmanland
• central Sweden
• N5922 N6145 E1715 E1225