Precambrian and Caledonian history of Svalbard’s West Ny Friesland Terrane

• Main Author: Hellman, Fredrik
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Department of Geology, Lund University 2000
• Subjects: Geology; Geologi; physical geography; Detrital; Zircon; Svalbard; Caledonides; Spitsbergen; fysisk geografi; Petrology; mineralogy; geochemistry; Petrologi; mineralogi; geokemi; Arctic; Nordaustlandet; Ny Friesland
• Online Access: https://lup.lub.lu.se/record/41090

This thesis deals mainly with age-investigations of metasedimentary and magmatic rocks of Ny Friesland, located in the northeastern Svalbard. However, the provenance of quartz-porphyry clasts in a Devonian conglomerate have also been investigated in northwestern Svalbard. This information is important for reconstructions of plate movements in the high Arctic during the Caledonian orogeny and earlier tectono-thermal events. It is also important for understanding the regional geological processes in the Svalbard Caledonides. The Svalbard Caledonides is composed of three terranes, the Northwestern, Southestern and the Eastern terranes, which are separated by large transcurrent faults. In the Eastern Terrane, the rocks of western Ny Friesland are dominated by a major antiformal thrust-stack, including four nappes. They are thrust together and folded during the Caledonian orogeny. The schists and gneisses are generally metamorphosed in amphibolite facies. Each thrust sheet contains granitic-gneisses of c. 1750 Ma age, which are overlain by metasediments. In this thesis, detrital zircons from metasediments have been dated and show that the metasediments in each nappe contain zircons of equal or younger age than the granitic-gneisses. It is therefore concluded that the metasediments are younger than the granitic gneisses. The detrital zircon ages from all the three upper nappes fall generally in three age groups, 1700-1750, 1850-2050, and 2500-2800 Ma. The lowest nappe contains slightly different age-populations of 1200-1300, 1650-1720 and 2500-2700 Ma. These sediments have probably been deposited in the Neoproterozoic but could be as young as Ordovician. In one of the thrust-sheets a quartz-monzonite have been dated to 2709 ±28 Ma and show that the basement complex also includes some older rocks. The rocks of western Ny Friesland differ greatly from those further to the east in Ny Friesland and on Nordaustlandet, which is dominated by Grenville-age metasediments and granites. The data obtained on western Ny Friesland ...