scholarly journals The Skuggliberga unit of the Oppdal area, central Scandinavian Caledonides: calc-alkaline pyroclastic volcanism in a fluvial to shallow-marine basin following a mid-Ordovician orogenic event

2021 ◽  
Author(s):  
Bjørgunn H. Dalslåen ◽  
Deta Gasser ◽  
Tor Grenne ◽  
Morgan Ganerød ◽  
Arild Andresen
Keyword(s):  
Calc Alkaline ◽  
Shallow Marine ◽  
Scandinavian Caledonides ◽  
Marine Basin

Deciphering the Vássačorru Igneous Complex within the Seve Nappe Complex, Scandinavian Caledonides 

2021 ◽  
Author(s):  
Sabine Rousku ◽  
Erika Nääs ◽  
Christopher Barnes ◽  
Abigail Barker ◽  
Jarosław Majka
Keyword(s):  
Active Continental Margin ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
Igneous Complex ◽  
Dolerite Dyke ◽  
Scandinavian Caledonides ◽  
Nappe Complex ◽  
Seve Nappe Complex ◽  
Metaigneous Rocks

<p>The Seve Nappe Complex (SNC) of the Scandinavian Caledonides comprises Neoproterozoic sedimentary and igneous rocks that experienced high-pressure metamorphism and deformation during subduction and exhumation. Fieldwork was conducted in the Kebnekaise region in northern Sweden, focusing on the Aurek metagabbro and the Vistas metaigneous rocks within the Vássačorru Igneous Complex (VIC), hosted within SNC metasediments. Field observations show that the Aurek metagabbro is locally sheared with well-defined foliation and lineation. In contrast, the Vistas metaigneous rocks, consisting of both granite and gabbro bodies, are only locally foliated. Furthermore, the granite is intruded by ENE-WSW striking dolerite and rhyolite dykes that parallel the local foliation, and are weakly deformed, whereas a NNE-SSW striking syenite dyke is observed in a portion of undeformed gabbro.</p><p>The Aurek metagabbro mineral assemblages consist of garnet, amphibole, plagioclase, biotite, chlorite, and pyroxene. The Vistas gabbro and dolerite dyke both consist of plagioclase, pyroxene, and amphibole. The Vistas granites and rhyolite dyke include quartz, feldspar, biotite, muscovite, ± garnet, and the syenite dyke contains feldspar, plagioclase, pyroxene, amphibole, quartz, and biotite. The Vistas metaigneous rocks generally show primary igneous assemblages.</p><p>Bulk rock chemistry shows that the Aurek and Vistas gabbros, and the Vistas dolerite dyke, are classified as tholeiites. For the Aurek gabbros, Th/Yb of 0.06-1.86 and Nb/Yb of 0.11-5.14 indicate that they have N-MORB to E-MORB compositions, with possible crustal input. The Vistas gabbro (Th/Yb of 0.09 and Nb/Yb of 1.15) and the dolerite dyke (Th/Yb of 0.12 and Nb/Yb of 0.66) also suggest such trend. The Vistas granites, rhyolite, and syenite dyke all have calc-alkaline composition. Trace elements confirm volcanic arc affinity for the granites and the syenite dyke (Nb: 3.1-5.9 ppm, Rb: 116.5-177.5 ppm, Y: 12.9-18.0 ppm, Ta: 0.3-0.4 ppm, Yb: 2.04-3.19 ppm), whereas the rhyolite dyke (Nb: 38.2 ppm, Rb: 247.8 ppm, Y: 72.6 ppm, Ta: 2.8 ppm and Yb: 12.62 ppm) reflects a within plate setting.</p><p>Combining the field relationship with geochemistry of the studied metaigneous rocks, we tentatively propose that the VIC is composed of three pulses of magmatism: (1) mafic MORB magmatism represented by the gabbros, emplaced in an extensional regime; (2) felsic calc-alkaline magmatism represented by granites and syenite, emplaced in an active continental margin environment; and (3) bimodal within-plate magmatism or crustal assimilation in a volcanic arc represented by dolerite and rhyolite dykes. However, the only existing age is from U-Pb zircon dating of the Vistas granite, which yielded 845±14 Ma (Paulsson & Andreasson, 2002). Further zircon U-Pb geochronology will be conducted to obtain ages of the various lithologies of the VIC to better understand temporal relationships and to link the VIC with tectonic events in the Scandinavian Caledonides.</p><p>This study was supported by the National Science Centre (Poland) grant no. 2019/33/B/ST10/01728 to J. Majka.</p><p>References</p><p>Paulsson, O., Andreasson, P.-G., 2002. Attempted break-up of Rodinia at 850 Ma: Geochronological evidence from the Seve-Kalak Superterrane, Scandinavian Caledonides. J. Geol. Soc. 159, 751–761. https://doi.org/10.1144/0016-764901-156</p>

END PERMIAN SALINITY AND OXYGENATION CHANGES IN A SHALLOW MARINE BASIN IN EAST GREENLAND

2016 ◽  
Author(s):  
Wolfram M. Kuerschner ◽  
◽  
Elsbeth E. van Soelen ◽  
Richard J. Twitchett
Keyword(s):  
Shallow Marine ◽  
East Greenland ◽  
Marine Basin

scholarly journals Geochemistry of the cretaceous-tertiary boundary (Fish Clay) at Stevns Klint (Denmark): Ir, Ni and Zn in kerogen

2006 ◽  
Vol 71 (7) ◽  
pp. 793-806 ◽  
Author(s):  
Pavle Premovic ◽  
Milena Krsmanovic ◽  
Bratislav Todorovic ◽  
Mirjana Pavlovic ◽  
Nikola Nikolic ◽  
...  
Keyword(s):  
Trace Metals ◽  
Surface Waters ◽  
Shallow Marine ◽  
Asteroid Impact ◽  
Impact Ejecta ◽  
Previous Hypothesis ◽  
Geochemical Analyses ◽  
The Impact ◽  
Fish Clay ◽  
Marine Basin

Geochemical analyses of trace metals (Ir, Ni and Zn) in the kerogen of the black marl of the Cretaceous-Tertiary boundary succession (Fish Clay) at Stevns Klint (H?jerup Church) were undertaken. The data for this kerogen were in accordance with a previous hypothesis that this (insoluble) geoorganic polymer was derived from humic substances (mainly humic acids) of a nearshore soil. Substantial proportions of Ir, Ni and Zn within the kerogen structure were probably contained in these substances arriving at the sedimentary site. It is proposed that these humics were probably transported by acid surface waters (induced by the KT asteroid impact) into the shallow marine basin of Stevns Klint. It is also suggested that local leaching/weathering of the asteroidal impact fallout on the land near these waters played an important role in providing Ir, Ni and Zn for these substances. Apparently, Ir, Ni and Zn of the kerogen were created by the chondritic component of the impact ejecta fallout.

Sign in / Sign up

Export Citation Format

Share Document