Preservation of magmatic signals in metavolcanics from Wedel Jarlsberg Land, SW Svalbard

Abstract

The purpose of this study is to determine the role of metamorphism and thereby identify the preserved magmatic signature in metavolcanics from Wedel Jarlsberg Land in southwestern Svalbard. Samples have been collected from late Precambrian metavolcanics occurring within metasedimentary rocks of the Sofiebogen Group, as well as dikes cutting older metasedimentary rocks of the Deilegga Group. The volcanic rocks were metamorphosed under greenschist facies conditions during the Caledonian Orogeny. To investigate the role of metamorphism, we present petrography, major and trace element geochemistry, and use factor analysis as a tool to identify correlations that correspond to primary magmatic signals.The metavolcanics are classified as subalkaline basalt to basaltic andesite and they contain relicts of primary clinopyroxene and plagioclase. The metamorphic minerals are actinolite, secondary plagioclase, chlorite and minerals belonging to the epidote group. Major element variations are highly scattered with no obvious trends observed. The HFSE and REE show strong trends attributed to fractional crystallization. The LILE, Th and La show elevated contents in some samples.Factor analysis shows that the HFSE and REE are well correlated. The LILE form a separate well correlated group, while the major elements are not correlated, except for Na2O, Fe2O3 and CaO. The lack of correlation for major elements, as well as the lack of observed fractional crystallization trends between these elements suggests that they were modified by metamorphism. The strong correlation of HFSE and REE reflects the original geochemical signal generated by magmatic processes. The correlation of the LILE is consistent with their elevated composition implying the influence of crustal contamination processes, and though some variability is likely superimposed due to metamorphism, the primary magmatic record is not completely destroyed. We conclude that 180 the HFSE and REE are not influenced by metamorphic processes and therefore provide robust records of magmatic processes.

Two garnet growth events in polymetamorphic rocks in southwest Spitsbergen, Norway: insight in the history of Neoproterozoic and early Paleozoic metamorphism in the High Arctic

“…The top of the Deilegga Group is marked by an angular unconformity (Torellian unconformity; Birkenmajer, 1975;Bjørnerud, 1990;Dallmann et al, 1990) the age of which is inferred to post-date 640 Ma (e.g., Mazur et al 2009;Majka et al 2014). The unconformity is overlain by basal conglomerate, locally intercalated with volcanic rocks (e.g., Gołuchowska et al 2012), and succeeding finer-grained sediments of the Sofiebogen Group. Both the…”

Detrital zircon U-Pb geochronology of a metasomatic calc-silicate in the Tsäkkok Lens, Scandinavian Caledonides

“…Considering the presence of pillow basalts that are likely related to rifting and incipient opening of the Iapetus Ocean (Kullerud et al 1990), this time frame is also suitable for deposition of the Tsäkkok Lens. Furthermore, lava flows have been documented within the Sofiebogen Group (Gołuchowska et al 2012), which can possibly be linked to volcanic record preserved in the Tsäkkok Lens. Such link is in agreement with a possible shared Caledonian history with the Vestgötabreen Complex on Svalbard (Barnes et al 2020a).…”

Magmatic and metamorphic events recorded within the Southwestern Basement Province of Svalbard

“…These mafic rocks are commonly referred to as the Jens Erikfjellet Formation [8]. Their geochemical signature indicates a within-plate tholeiitic source [8,17]. In the northern part of Wedel Jarlsberg Land (Chamberlindalen area), a suite of well-preserved alkali cumulates is present [18].…”