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The Baklia Fault Zone – a regional strike-slip zone splitting Prins Karls Foreland (Svalbard

Ziemniak G., Czerny J., Manecki M., Kośmińska K.

Geology, Geophysics and Environment

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2016

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Vol. 42, no. 1

142--143

EN

Prins Karls Foreland (PKF) is a westernmost island of Svalbard Archipelago belonging to the Southwestern Basement Province. The island consists of low-metamorphic facies probably Neoproterozoic metasediments, divided into two, northern and southern parts. Both parts are characterized by similar geological structures but different stratigraphy. New discoveries presented here result from joint, Norwegian Polar Institute and AGH UST Krakow expeditions in 2013 and 2014. Thorough characteristics of the location and character of a strike-slip fault splitting PKF (the Baklia Fault Zone) is presented here for the first time. To date, one succession has been distinguished in the lithostratigraphy of PKF’s basement. The northern part of the island consists of two groups: the Scotiafjellet Group and Grampianfjella Group (Dallmann et al. 2015). They comprise low-metamorphic metasediments (chlorite zone of greenschist facies), mostly slates, metapsamites and carbonates. Stratigraphic units of the southern part represent slightly higher, biotite metamorphic zone, and have been considered to be conformably underlying Scotiafjellet Group. The uppermost Peachflya Group and Geikiebreen Group (mostly phyllites with metavolcanics and carbonates) are in thrust contact with underlying Ferrierpiggen Group, comprising schistose diamictites. The Ferrierpiggen Group is a tectonic unit stratigraphically discontinuous at top and bottom. Isolated klippe of the Ferrierpiggen Group separated from Scotiafjellet Group by tectonic boundary is present in the northern part of PKF (Harland et al. 1979, 1993). These complexes have undergone the Caledonian metamorphism followed by D 1 deformation producing SE directed folding and thrusts. D 2 deformation was coaxial, but not coplanar with D 1. D 2 deformation occurred probably in Mid-Cenozoic and resulted in refolding and thrusting, followed by formation of a dextral shear zone along Scotiadalen (Morris 1989). D 3 deformation is connected with transtensional formation of the Forlandsundet Graben along NNW-SSE faults finishing the West Spitsbergen Orogeny (WSO) (Manby 1986). Distinct difference in the stratigraphy of southern and northern parts of PKF is apparent. The presence of the fault dividing the island was indicated before (Hjelle et al. 1979), but no single fault has been recognized during detailed mapping later on (Harland et al. 1979, Morris 1982, Manby 1986, Morris 1989). Mapping and structural measurements conducted by the authors in the area of Selvågen led to the discovery of the major fault zone (the Baklia Fault Zone – BFZ) dividing PKF into two terrains. The BKF have N-S trend from Haukebukta in the west coast, through the slopes of Alasdairhornet (where it trapped few hundred meters long slab of the Ferrierpiggen Group rocks), to the southern Scotiadalen. Approaching Selvågen, the fault zone bends slightly to the NNE-SSW. The zone is filled with breccias and mixture of different lithologies with slabs of rocks derived from both limbs of the fault zone. The width of the zone measures approximately 100–250 meters. To the east, it is accompanied by at least three narrow subparallel faults. The age of the BFZ is unknown. A brittle character of deformation may suggest that it is Cenozoic in age. En échelon normal faults with a drop to the north, which associate BFZ may be considered as a Riedel shears R 1 formed at the beginning of a strike-slip movement. Structural measurements on slickensides as kinematic indicators revealed that normal faulting was associated with both, dextral and sinistral shear (not simultaneous). A main movement connected with dextral shearing occurred probably earlier, during late stages of the early Cenozoic crustal shortening. The extended width of the fault zone and the presence of a mixture of rock material from both terranes suggest the significant lateral displacement that might reach tens of kilometers. The BFZ cuts through the boundary faults of the Forlandsundet Graben displacing them sinistrally by approximately one kilometer. This suggests that sinistral movement was probably associated with rejuvenation of the fault during late stages or after the Forlandsundet Graben formation. There are several regional implications of BFZ. The stratigraphic relationship of southern and northern terranes is unclear. The presence of BFZ at the boundary of the Scotiafjellet and Peachflya groups does not exclude their stratigraphic succession but makes it impossible to define. The field observations suggest that BFZ may be Cenozoic in age. It has similar tectonic style and orientation to other strike-slip zones present along western Svalbard coast. Strong tectonic deformation suggests displacement of the northern terrain of PKF by tens of kilometers. Even though southern terrain can be directly correlated with Oscar II Land, more research is needed to correlate more exotic northern terrain of PKF with the basement rocks in the southern parts of Spitsbergen. Ongoing research towards dating and detail structural characterization of this regional fault zone will allow for reconstruction of pre-Tertiary position of this part of Archipelago.

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HP metamorphism recorded by kyanite-garnet gneisses in the Kafjord Nappe, Northern Norway -preliminary results

Ziemniak G., Majka J., Kośmińska K., Manecki M., Czerny J.

Geology, Geophysics and Environment

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2014

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Vol. 40, no. 1

152--153

EN

Scandinavian Caledonides are Himalaya-type mountain belt consisting of allochthons that are a result of the Ordovician-Silurian collision of Baltica and Laurentia (Gee et al. 2008). The Skibotn Nappe Complex, traditionally ascribed to the Upper Allochthon (but possibly being a part of the Middle Allochthon) is situated in northern Norway. It consists of the Normandsvik, Kafjord and Vaddas nappes (Anderson et al. 1992). The Kafjord Nappe has not been fully examined, so the information about the age and metamorphic conditions are lacking. The main goal of this project is to provide a new data about peak metamorphic conditions to which the Kafjord Nappe has been exposed and to compare them with possible equivalents within the Scandinavian Caledonides. Three samples of kyanite-garnet gneisses from different parts of the Kafjord Nappe have been studied. All of them contain similar mineral assemblage. Progressive paragenesis occurs in lenses and contains garnet, kyanite, quartz, white mica, biotite, plagioclase, rutile and opaque minerals. Retrogressive paragenesis contains similar minerals with additional presence of chlorite. Two generations of garnet, white mica and biotite are present. Garnet I occurs as large poikiloblasts up to 6 mm in diameter with abundant variably sized inclusions, whereas garnet II is smaller (up to 1 mm) with less numerous inclusions. Biotite and white mica appear as flakes conformable with the main foliation and as transversal blasts. Kyanite occurs as transversal blasts up to 5 mm in size, with moderate number of inclusions. All the observations mentioned above suggest that these rocks were probably subjected to at least two metamorphic events, one of which could have happened under high pressure conditions. On the basis of chemical composition of minerals and rocks bulk chemistry, thermodynamical modeling will be performed and peak temperature and pressure as well as the retrogressive paths will be determined. Similarities in lithologies and the inferred grade of metamorphism suggest that, in contrast to the previous correlations, the studied gneisses from the Kafjord Nappe may be an equivalent of the Seve Nappe Complex described by Hacker & Gans (2005).

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

Gołuchowska K., Barker A. K., Majka J., Manecki M., Czerny J., Bazarnik J.

Mineralogia

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2012

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Vol. 43, iss. 3/4

179--197

EN

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 the HFSE and REE are not influenced by metamorphic processes and therefore provide robust records of magmatic processes.

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New evidence for high-pressure metamorphic rocks in Western Svalbard

Kośmińska K., Majka J., Krumbholz M., Klonowska I., Manecki M., Czerny J.

Geology, Geophysics and Environment

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2012

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Vol. 38, no. 4

488--489

EN

During a field expeditions to Nordenskiold Land and Wedel Jarlsberg Land (western Svalbard), previously unrecognised high-grade metamorphic rocks were observed. These rocks are represented by blueschists sensu stricto and blueschist facies metapelites. In Nordeskiold Land, blueschists occur in form of isolated bodies/tectonic lenses of different size enclosed within metasediments. The rocks in question are dark green, consist mainly of reddish garnet porphyroblasts and greenish and bluish amphiboles (including ferroglaucophane). They also contain chlorite, epidote, phengite, biotite, pumpellyite, quartz and albite. Garnet forms euhedral to subhedral poikiloblasts containing voluminous inclusions of epidote, albite, quartz, amphibole and titanite. Garnet shows chemical compositional variation from Alm49Pyr1Grs33Spss17 in the cores to Alm63Pyr2Grs32Spss3 in the rims. Gradual changes in chemical zoning as well as bell-shaped Spss content profiles suggest one-step, progressive garnet growth. P-T estimates based on thermodynamic modeling (using Perple_X'O7) in the NCKFMMnASHT system suggest peak pressure conditions of ca. 20 kbar and 480°C. P-T estimates are based on garnet and phengite compositional isopleths and stability field of the paragenetic assemblage (Chl-Ph-Ampl-Amp2-Grt-Spn). Tectonically, the whole area is characterized by a moderate, 50°-dipping of SO and SI (the main metamorphic foliation) to the north. Deviations from this direction are small and occur only locally. They are mostly caused by the presence of rigid metamafic bodies, around which the common orientation of the bedding and the metamorphic foliation is disturbed. The observed stretching lineations plunge towards the N-NNE and are therefore in very good agreement with the orientation of SO and SI. Moreover, shear sense indicators such as commonly observed sigma elasts clearly indicate a transport direction from the north to the south. The structural observations are in good agreement with those collected south of the Nordenskiold Land, in the northern part of Wedel Jarlsberg Land (Antoniabreen area), where high grade augen gneisses and metapelites thrusted onto typical low-grade rocks of SW Svalbard occur. The metapelites contain mainly garnet, muscovite, biotite, chlorite and quartz. Most of the garnet porphyroblasts show two distinct growth zones. Garnet-I (Alm64Pyr6Grs9Spss21) represents the inner growth zone, forming inclusion-rich garnet core and garnet-II (Alm52Pyr2Grs30Spss16) builds the outer growth zone, forming euhedral garnet rims. Some of the smaller garnet porphyroblasts show only a single growth zone (representing grt-II). Preliminary P-T estimates based on thermodynamic modeling in the NCKFMMnASHT system indicate the growth of garnet-I at ca. 550°C and relatively low pressure (ca. 5 kbar), whereas garnet-II grew at ca. 500°C and 12 kbar. The P-T estimates for garnet-I are based on garnet, biotite and plagioclase compositional isopleths and stability field of the paragenetic assemblage (Bt-Chl-Pl-Ms-Grt), whereas for garnet-II on the garnet and muscovite isopleths and stability field of the assemblage (Bio-Chl-Ms-Grt-Ab). We suggest that the growth of garnet-I is connected to the Late Neoproterozoic Torellian event, while garnet-II has been growing under blueschist facies conditions, hence most probably during the Caledonian orogeny. Tectonic observations and P-T conditions are similar in both studied areas. It suggest that vast parts of the Caledonian basement of Nordeskiold Land and northern Wedel Jarlsberg Land were metamorphosed under high pressure conditions. These blueschist facies rocks may be an equivalent of the high pressure unit known from Oskar II Land (Motalafjella region), occurring to the north from the research area. Further, detailed petrological and geochronological studies to verify this hypothesis are in progress.

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Metavolcanics of Nordenskiold Land from SW Svalbard as an example of New Ocean Crust

Gołuchowska K., Barker A. K., Manecki M., Majka J., Czerny J.

Geology, Geophysics and Environment

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2012

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Vol. 38, no. 4

473

EN

This study concerns late Neoproterozoic metavolcanics from southwestern Svalbard in an investigation to trace the evolution of oceans plate rifting. A number of outcrops of these rocks are connected with the regional Torellian unconformity, which is associated with a Late Neoproterozoic orogenesis event - post 640 Ma. This unconformity divides the younger metasediments of the Sofiebogen Group from older metasedimentary sequence of the Deilegga Group. Samples have been collected from Nordenskiold Land belonging to the Sofiebogen Group, which is situated between Bellsund and Isfjorden, to the north of Wedel Jarlsberg Land. Field observation reveals that these metavolcanics very often occur as a pillow lavas and lavas. They contain mineral assemblages typical for greenschist facies metamorphism such as: actinolite, chlorite, epidote, albite, but some of them contain garnets and glaucophane, which is typical for blueschist facies conditions. Based on a total alkali silica diagram they are classified as tholeitic basalts. Spider diagram shows patterns similar to MORB, where the REE are flat. The LILE except Sr are depleted, but this depletion is caused probably by metamorphism. However, the metavolcanics of Nordenskiold Land are also relative depleted in HFSE (Th/Yb = 0.2-0.31 and Nb/Yb = 2.9-4.4) and LREE (Lan/Smn = 1.0-1.5). Trace elements like Nd, Th, Yb and La show trends that could be associated with fractional crystallization. The geochemical character of metavolcanics from Nordenskiold Land, as well as, their forms (pillow lavas) suggests that they created beneath the sea level, as new ocean crust.

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Przeobrażenia amfiboli w porfirach ryodacytowych z Zalasu koło Krakowa

Marszałek M., Czerny J.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2009

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T. 35, z. 2/1

159-166

EN

The study was aimed at alteration of amphibole phenocrysts in the porphyries from Zalas. The alteration processes took place at the magmatic stage: development of orthopyroxenes and biotitization, and at the postmagmatic one: chloritization followed by argillitization and formation of feldspars, carbonate minerals, quartz, ilmenite, magnetite and hematite. Post-magmatic alteration resulted from hydrothermal processes of the metasomatic character.