Late Neoproterozoic amphibolite-facies metamorphism of a pre-Caledonian basement block in southwest Wedel Jarlsberg Land, Spitsbergen: new evidence from U–Th–Pb dating of monazite

2008 ◽  
Vol 145 (6) ◽  
pp. 822-830 ◽  
Author(s):  
JAROSLAW MAJKA ◽  
STANISLAW MAZUR ◽  
MACIEJ MANECKI ◽  
JERZY CZERNY ◽  
DANIEL K. HOLM
Keyword(s):  
Amphibolite Facies ◽  
Svalbard Archipelago ◽  
Passive Margins ◽  
Metamorphic History ◽  
Facies Metamorphism ◽  
Late Neoproterozoic ◽  
The Baltic ◽  
New Evidence ◽  
Greenschist Facies Metamorphism

AbstractSouthwest Spitsbergen, Wedel Jarlsberg Land, consists of two Proterozoic crustal blocks with differing metamorphic histories. Both blocks experienced Caledonian greenschist-facies metamorphism, but only the southern block records an earlier pervasive M1 amphibolite-facies metamorphism and strong deformational fabric. In situ EMPA total-Pb monazite geochronology from both matrix and porphyroblast inclusion results indicate that the older M1 metamorphism occurred at 643 ± 9 Ma, consistent with published cooling ages of c. 620 Ma (hornblende) and 580 Ma (mica) obtained from these same rocks. This region thus contains a lithostratigraphic profile and metamorphic history which are unique within the Svalbard Archipelago. Documentation of a pervasive late Neoproterozoic Barrovian metamorphism is difficult to reconcile with a quiescent non-tectonic regime typically inferred for this region, based on the occurrence of rift-drift sequences on the Baltic and Laurentian passive margins. Instead, our new metamorphic age implies an exotic origin of the pre-Devonian basement exposed in SW Spitsbergen and supports models of terrane assembly postulated for the Svalbard Archipelago.

Microstructures and mineral chemistry in amphibolites from the western Tauern Window (Eastern Alps), and P-T deformation paths of the Alpine greenschist-amphibolite facies metamorphism

1995 ◽  
Vol 59 (397) ◽  
pp. 641-659 ◽  
Author(s):  
Bernhard Schulz ◽  
Claude Triboulet ◽  
Claude Audren
Keyword(s):  
Mineral Chemistry ◽  
Eastern Alps ◽  
Amphibolite Facies ◽  
Tauern Window ◽  
Metamorphic History ◽  
Lithostratigraphic Units ◽  
Facies Metamorphism ◽  
Austroalpine Basement ◽  
T Deformation Paths ◽  
Extension Axis

AbstractAmphibolites in the Mesozoic part of the parautochthonous Lower Schieferhülle (LSH), the allochthonous Upper Schieferhülle (USH) and the overlying Austroalpine basement (AA) in and around the western Tauern Window (Eastern Alps) suffered a progressive Alpine deformation. Lineations and foliations L1-S1, L2-S2 defined by preferentially oriented (Na-Ca) amphiboles as well as F3 folds and further foliations Smyl and S4 in the metabasites are structures of successive deformational stages with a constant W-E main extension axis of strain. The (Na-Ca) amphiboles in assemblages with epidote, chlorite, albite/oligoclase and quartz are zoned with similar continuous zonation trends from early actinolite in the cores to magnesio-hornblende and tschermakitic hornblende, and from magnesio-hornblende to late actinolite in the rims in the three lithostratigraphic units. Geothermobarometry involving tremolite-edenite and (pargasite-hastingsite)-tremolite end-member equilibria in amphiboles allowed us to reconstruct prograde-retrograde P-T paths for the Alpine greenschist-amphibolite facies event. The paths passed P/Tmax at 6–7 kbar/600°C. Similar shapes of the paths in AA, USH and Mesozoic LSH indicate a common metamorphic history and a stacking of these units prior to or during the pre-Pmax evolution. Moderate P-T ratios are characteristic for the temperature-dominated compression paths and indicate continental collisional rather than subduction zone metamorphism. The middle to late Alpine greenschist-amphibolite facies event appears as an independent metamorphism along a complete P-T loop which may have followed an earlier and poorly documented high-pressure/low-temperature event.

scholarly journals Thermochronological evidence for late Proterozoic (Vendian) cooling in southwest Wedel Jarlsberg Land, Spitsbergen

1998 ◽  
Vol 135 (1) ◽  
pp. 63-69 ◽  
Author(s):  
M. MANECKI ◽  
D. K. HOLM ◽  
J. CZERNY ◽  
D. LUX
Keyword(s):  
Geological Mapping ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Variable Intensity ◽  
Late Proterozoic ◽  
Facies Metamorphism ◽  
History Of ◽  
Greenschist Facies Metamorphism

Two Proterozoic terranes with different metamorphic histories are distinguished from geological mapping in southwestern Wedel Jarlsberg Land: a northern greenschist facies terrane and a southern amphibolite facies terrane which has been overprinted by greenschist facies metamorphism. To better characterize the tectonothermal history of these terranes we have obtained new 40Ar/39Ar mineral dates from this area. A muscovite separate from the northern terrane yielded a Caledonian plateau age of 432±7 Ma. The southern terrane yielded significantly older 40Ar/39Ar ages with three muscovite plateau dates of 584±14 Ma, 575±15 Ma, and 459±9 Ma, a 484±5 Ma biotite plateau date, and a 616±17 Ma hornblende plateau date. The oldest thermochronological dates are over 300 Ma younger than the age of amphibolite facies metamorphism and therefore probably do not represent uplift-related cooling. Instead, the Vendian dates correlate well with a regionally widespread magmatic and metamorphic/thermal resetting event recognized within Caledonian complexes of northwestern Spitsbergen and Nordaustlandet. The apparent Ordovician dates are interpreted to represent partial resetting, suggesting that late Caledonian greenschist facies overprinting of the southern terrane was of variable intensity.

Bio-signatures in metabasaltic glass of a Caledonian ophiolite, West Norway

2002 ◽  
Vol 139 (6) ◽  
pp. 601-608 ◽  
Author(s):  
HARALD FURNES ◽  
KARLIS MUEHLENBACHS ◽  
TERJE TORSVIK ◽  
OLE TUMYR ◽  
LANG SHI
Keyword(s):  
Organic Matter ◽  
Early Stage ◽  
Volcanic Rocks ◽  
Present Evidence ◽  
X Ray ◽  
Basaltic Rocks ◽  
Facies Metamorphism ◽  
Reducing Bacteria ◽  
Greenschist Facies Metamorphism

Evidence of bioalteration of natural basaltic rocks, presently receiving much attention, has so far been restricted to in situ oceanic crust and ophiolites in which fresh glass is still present. Here we present evidence of preserved bio-signatures in the chilled margin of pillow lavas of an old (443 Ma) ophiolite that has suffered pervasive lower greenschist facies metamorphism and deformation. X-ray mapping of initial alteration zones shows the remains of organic carbon associated with highly-concentrated Fe and S. Bioproduction of CO2 is further reflected in the low δ13C values of calcite extracted from pillow rims, compatible with microbe-induced fractionation during oxidation of organic matter. We attribute these effects to growth of sulphate-reducing bacteria at the early stage of ophiolite formation. During energy metabolism these bacteria reduce sulphate to H2S and oxidize organic matter to CO2 . Hydrogen sulphide will eventually react with iron and form pyrite, and carbon dioxide is precipitated as calcium carbonate. The results of this study may thus trigger the search for bio-signatures in glassy volcanic rocks of any age.

scholarly journals Neoproterozoic pegmatite from Skoddefjellet, Wedel Jarlsberg Land, Spitsbergen: Additional evidence for c. 640 Ma tectonothermal event in the Caledonides of Svalbard

2012 ◽  
Vol 33 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Jarosław Majka ◽  
Alexander Larionov ◽  
David Gee ◽  
Jerzy Czerny ◽  
Jaroslav Pršek
Keyword(s):  
Electron Microprobe ◽  
Regional Metamorphism ◽  
Amphibolite Facies ◽  
The Other ◽  
Clear Distinction ◽  
Metasedimentary Rocks ◽  
Facies Metamorphism ◽  
Shrimp Zircon ◽  
Tectonothermal Event

Neoproterozoic pegmatite from Skoddefjellet, Wedel Jarlsberg Land, Spitsbergen: Additional evidence forc. 640 Ma tectonothermal event in the Caledonides of SvalbardNeoproterozoic (c. 640 Ma) amphibolite facies metamorphism and deformation have been shown recently to have affected the Isbjørnhamna and Eimfjellet Complex of Wedel Jarlsberg Land in southwestern Spitsbergen. New SHRIMP zircon U-Pb andin situelectron microprobe monazite and uraninite U-Th-total Pb ages are presented here on a pegmatite occurring within the Isbjørnhamna metasedimentary rocks. Although the dated zircons are full of inclusions, have high-U contents and are metamict and hence have experienced notable Pb-loss, the new Cryogenian ages are consistent with the age of regional metamorphism of the host metasediments, providing additional evidence for a clear distinction of the Southwestern Province from the other parts of the Svalbard Caledonides.

scholarly journals Contrasted types of metamorphism of basic intrusions in the Precambrian basement of the Tasîussaq area, South Greenland

1968 ◽  
Vol 71 ◽  
pp. 1-47
Author(s):  
P.R Dawes
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Precambrian Basement ◽  
Thermal Front ◽  
Granulite Facies Metamorphism ◽  
North West ◽  
Metamorphic History ◽  
Long Span ◽  
The North ◽  
Facies Metamorphism

Metamorphosed rocks of three distinct episodes of basic intrusion can be recognised in the Precambrian basement of the Tasiussaq area, South Greenland. The oldest intrusions, represented by sills and dykes, are pyriclasites and biotitepyriclasites; the second episode intrusions, in the form of dykes, are pyroxenemetadolerites and the third episode intrusions, represented by dykes and small bodies, are metagabbros, metadolerites, metanorites and amphibolites. The metamorphic nature of the rocks of the three episodes is a reflection of age. Chemical and modal analyses of rocks from the three episodes are presented. Fresh diorite sills and dolerite dykes represent later episodes of Precambrian basic intrusion. The basic rocks depict the varying types of metamorphic conditions which affected the area in Precambrian time, and these are seen to differ from the established metamorphic history in areas to the north-west in South Greenland. The pyriclasites and biotite-pyriclasites have been derived through granulite facies metamorphism; the pyroxene-metadolerites by dipsenic metamorphism under conditions corresponding to the amphibolite facies and the metagabbros, metadolerites, metanorites and amphibolites through amphibolitisation during amphibolite facies metamorphism. It is suggested that the metamorphism producing the pyroxene-metadolerites (Sanerutian in age) was controlled by dipsenic conditions inherited from earlier granulite facies metamorphism (Ketilidian in age). This implies that the Ketilidian and Sanerutian metamorphisms in the Tasiussaq area are not separated by a long span of time and that the break in plutonism marked by the pyroxene-metadolerites cannot be regarded as a significant cratogenic hiatus between two separate plutonisms. The importance of water in controlling trends in the metamorphism of dolerites is stressed. The 1st episode intrusions have undergone severe changes since intrusion and no palimpsest features indicative of primary texture or mineralogy remain. The majority of the 2nd episode intrusions display a granular texture, but some display sub-ophitic and relic sub-ophitic textures. The 3rd episode intrusions display a range from ophitic, sub-ophitic and microporphyritic textures to relic stages of these textures. The 1st episode intrusions were emplaced into a geosynclinal pile of sediments and were probably connected with the volcanicity which occurred at the end of sedimentation. The 2nd and 3rd episode intrusions were emplaced into granitic and metamorphic rocks at a later stage in the same 'geological cycle'. Both the 2nd and 3rd episode intrusions are considered to indicate trends in the crust towards brittle conditions marking temporary partial withdrawals of the thermal front. Their preserved ophitic and sub-ophitic textures are not indicative of emplacement and crystallisation in cratogenic conditions.

Torellian (c. 640 Ma) metamorphic overprint of Tonian (c. 950 Ma) basement in the Caledonides of southwestern Svalbard

2013 ◽  
Vol 151 (4) ◽  
pp. 732-748 ◽  
Author(s):  
JAROSŁAW MAJKA ◽  
YARON BE’ERI-SHLEVIN ◽  
DAVID G. GEE ◽  
JERZY CZERNY ◽  
DIRK FREI ◽  
...  
Keyword(s):  
Igneous Rocks ◽  
Ion Microprobe ◽  
Metamorphic Overprint ◽  
Iapetus Ocean ◽  
Facies Metamorphism ◽  
Thrust Sheets ◽  
Caledonian Orogeny ◽  
Late Neoproterozoic ◽  
New Evidence ◽  
Early Neoproterozoic

AbstractIon microprobe dating in Wedel Jarlsberg Land, southwestern Spitsbergen, provides new evidence of early Neoproterozoic (c. 950 Ma) meta-igneous rocks, the Berzeliuseggene Igneous Suite, and late Neoproterozoic (c. 640 Ma) amphibolite-facies metamorphism. The older ages are similar to those obtained previously in northwestern Spitsbergen and Nordaustlandet where they are related to the Tonian age Nordaustlandet Orogeny. The younger ages complement those obtained recently from elsewhere in Wedel Jarlsberg Land of Torellian deformation and metamorphism at 640 Ma. The Berzeliuseggene Igneous Suite occurs in gently N-dipping, top-to-the-S-directed thrust sheets on the eastern and western sides of Antoniabreen where it is tectonically intercalated with younger Neoproterozoic sedimentary formations, suggesting that it provided a lower Tonian basement on which upper Tonian to Cryogenian sediments (Deilegga Group) were deposited. They were deformed together during the Torellian Orogeny, prior to deposition of Ediacaran successions (Sofiebogen Group) and overlying Cambro-Ordovician shelf carbonates, and subsequent Caledonian and Cenozoic deformation. The regional importance of the late Neoproterozoic Torellian Orogeny in Svalbard's Southwestern Province and its correlation in time with the Timanian Orogeny in the northern Urals as well as tectonostratigraphic similarities between the Timanides and Pearya (northwestern Ellesmere Island) favour connection of these terranes prior to the opening of the Iapetus Ocean and Caledonian Orogeny.

DIVING DEEPER INTO THE PICURIS OROGEN: UPPER AMPHIBOLITE FACIES METAMORPHISM AND BRITTLE DEFORMATION ALONG THE PLOMO SHEAR ZONE

2020 ◽  
Author(s):  
Adrian E. Castro ◽  
◽  
Chloe Bonamici ◽  
Christopher G. Daniel ◽  
Danielle Shannon Sulthaus
Keyword(s):  
Shear Zone ◽  
Amphibolite Facies ◽  
Brittle Deformation ◽  
Facies Metamorphism

Sustainable use of wildlife in western New South Wales: Possibilities and problems.

2000 ◽  
Vol 22 (1) ◽  
pp. 88 ◽  
Author(s):  
DB Croft
Keyword(s):  
Arid Zone ◽  
Sustainable Use ◽  
Ex Situ ◽  
Animal Products ◽  
Wildlife Tourism ◽  
South Wales ◽  
Wild Progenitors ◽  
Ecologically Sustainable ◽  
New Evidence

Sustainable use of wildlife has become equated with exploitation of animal products (meat, skin or feathers) and/or removal of wild progenitors into the pet trade. This consumption of the wildlife is therefore largely ex situ and so removes nutrients and energy from the rangelands. Demand for lethal or a removal action is often driven by the severity of the perceived conflict between the wildlife and other enterprises, especially agriculture, rather than for the resulting products. Such uses also raise community concerns about humane treatment of animals and a valuing of the natural heritage. Wildlife-based tourism, as part of the valuable and growing nature-based or ecotourism industry in Australia, is an in situ use that may be a more ecologically sustainable and economically twble option for use of rangeland wildlife. This paper examines these possibilities and their problems with a focus on the commercial kangaroo industry and the use of arid-zone mammals, birds and reptiles for pets. It provides new evidence that wildlife-tourism based on free-living kangaroos in the rangelands is both feasible and in demand. This industry should be given advocacy in the on-going debate on the management and future of the rangelands. Key words: kangaroos, wildlife management, wildlife tourism, game harvesting

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