The Ljugaren granite massif, Dalarna, central Sweden
Titel:
The Ljugaren granite massif, Dalarna, central Sweden
Auteur:
Cruden, Alexander Aaro, Sven
Verschenen in:
GFF
Paginering:
Jaargang 114 (1992) nr. 2 pagina's 209-225
Jaar:
1992
Inhoud:
The circular, 13 km wide, c. 1700 Ma old Ljugaren granite massif intrudes and deforms 1890 to 1850 Ma old gneissose rocks and 1790 to 1740 Ma old late-orogenic granite sheets of the Svecofennian Orogenic Province. It is satellitic to the 1840 to 1680 Ma old Transscandinavian Granite-Porphyry Belt, and is partly overlain unconformably by Ordovician-Silurian sediments which are preserved around the Siljan Ring meteorite impact structure. Aeromagnetic and structural geological studies show that regional country-rock structure swings into concordance with the massif's margins 1-3 km from the contact. Gravity measurements indicate that the intrusion is shaped like an asymmetric funnel. Internally, the Ljugaren granite shows a weak, inwardly dipping, planar magmatic fabric concordant to its margins. Evidence to date indicates that the massif was emplaced into ductile crust as a magmatic diapir after the culmination of the Svecofennian orogeny c. 1700 Ma ago.
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