Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps)
<p>The chemical composition of metasediments is a valuable source of paleogeographic information about the protolith's sedimentary environment. Here, we compile major- and trace-element whole-rock data, including B contents, and <span class="inline-formula"><math xmlns=...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-07-01
|
| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/33/401/2021/ejm-33-401-2021.pdf |
| _version_ | 1819103323542781952 |
|---|---|
| author | G. Franz M. Kutzschbach E. J. Berryman A. Meixner A. Loges A. Loges D. Schultze D. Schultze |
| author_facet | G. Franz M. Kutzschbach E. J. Berryman A. Meixner A. Loges A. Loges D. Schultze D. Schultze |
| author_sort | G. Franz |
| collection | DOAJ |
| description | <p>The chemical composition of metasediments is a valuable
source of paleogeographic information about the protolith's sedimentary
environment. Here, we compile major- and trace-element whole-rock data,
including B contents, and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><msup><mi/><mrow><mn mathvariant="normal">10</mn><mo>/</mo><mn mathvariant="normal">11</mn></mrow></msup></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="547c313a8ba5718ee29d24f2c69c09d1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-33-401-2021-ie00001.svg" width="24pt" height="11pt" src="ejm-33-401-2021-ie00001.png"/></svg:svg></span></span>B-isotope ratios from the Permo-Triassic
metasedimentary cover of the Pfitsch–Mörchner basin, overlying the
Variscan basement in the western Tauern Window, Eastern Alps
(Austria and Italy). The basement consists of orthogneiss (“Zentralgneis”,
metamorphosed Variscan granitoids with intrusion ages between 305 and 280 Ma), and the roof pendant consists of granites (amphibolites, paragneiss, and
minor serpentinites). The Zentralgneis is partly hydrothermally altered into
pyrite quartzite with high Al–S contents, low Na–Sr–Ca–Mg contents, and very strong
depletion of the light rare earth elements. Comparison with published
detailed mapping of this and other time-equivalent basins in the western
Tauern Window, with radiometric age data in the literature, and with
unmetamorphosed basins in the South Alpine realm yields a late Permian to
Early Triassic age of sedimentation.</p>
<p>Although during Alpine metamorphism all rocks were strongly deformed, the
whole-rock chemical compositions of the metasediments were not pervasively
changed during deformation. We show that the sediments were deposited in a
small, probably lacustrine–fluviatile, intramontane basin, under arid to
semi-arid climatic conditions. The sequence starts with metaconglomerates,
which can be interpreted as a mixture of the different basement rocks, based
on a combination of major-element ratios Na<span class="inline-formula"><sub>2</sub></span>O <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e653eaf840568ee76bb20ba3bf368ae0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-33-401-2021-ie00002.svg" width="8pt" height="14pt" src="ejm-33-401-2021-ie00002.png"/></svg:svg></span></span> (Na<span class="inline-formula"><sub>2</sub></span>O <span class="inline-formula">+</span> K<span class="inline-formula"><sub>2</sub></span>O)
and MgO <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="36bd7baae116a5efc17e692d563c2b51"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-33-401-2021-ie00003.svg" width="8pt" height="14pt" src="ejm-33-401-2021-ie00003.png"/></svg:svg></span></span> (MgO <span class="inline-formula">+</span> Fe<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>3</sub></span>) with concentrations of trace elements Cr, V,
and Ni. The sequence is overlain by a fining-upwards sequence of clastic
sediments, in which the behavior of K, Rb, and Sr allows the reconstruction
of intense diagenetic K–B metasomatism, which raised the K<span class="inline-formula"><sub>2</sub></span>O contents
up to <span class="inline-formula">∼</span> 10 wt %. The average B content of 218 <span class="inline-formula">µ</span>g g<span class="inline-formula"><sup>−1</sup></span> is
well above the B content of common sediments, and the B-isotope composition
reaches extremely low values of down to <span class="inline-formula">−33</span> ‰ <span class="inline-formula"><i>δ</i><sup>11</sup></span>B. The top of the sequence is a lazulite quartzite, interpreted as a
former conglomeratic phosphatic sandstone, which marks the transition from a
closed Permian basin to an open Triassic basin. Within the clastic sequence,
the presence of hydrothermal tourmalinite veins documents a hydrothermal
event after deposition but before the onset of Alpine metamorphism. A
metamorphosed mafic dike swarm in the orthogneiss indicates a post-Variscan
event of basaltic magmatism, and this event is tentatively correlated with
increased heat flow in the Triassic basin and hydrothermal activity. A
consistent conceptual model of this basin and its diagenetic modifications,
based on a combination of geochemical data with petrographical and field
information, provides the geodynamic context of the European margin at the
onset of the Alpine orogeny.</p> |
| first_indexed | 2024-12-22T01:48:38Z |
| format | Article |
| id | doaj.art-2c331411f3084773bfe3be3f82f208ad |
| institution | Directory Open Access Journal |
| issn | 0935-1221 1617-4011 |
| language | English |
| last_indexed | 2024-12-22T01:48:38Z |
| publishDate | 2021-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | European Journal of Mineralogy |
| spelling | doaj.art-2c331411f3084773bfe3be3f82f208ad2022-12-21T18:42:58ZengCopernicus PublicationsEuropean Journal of Mineralogy0935-12211617-40112021-07-013340142310.5194/ejm-33-401-2021Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps)G. Franz0M. Kutzschbach1E. J. Berryman2A. Meixner3A. Loges4A. Loges5D. Schultze6D. Schultze7Technische Universität Berlin, Chair of Applied Geochemistry, 10587 Berlin, GermanyTechnische Universität Berlin, Chair of Applied Geochemistry, 10587 Berlin, GermanyCanmetMINING, Natural Resources Canada, Ottawa, K1A 0G1, Ontario, CanadaFaculty of Geosciences & MARUM – Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, GermanyTechnische Universität Berlin, Chair of Applied Geochemistry, 10587 Berlin, GermanyFreie Universität Berlin, Chair of Mineralogy, 12249 Berlin, GermanyTechnische Universität Berlin, Chair of Applied Geochemistry, 10587 Berlin, GermanyFreie Universität Berlin, Chair of Mineralogy, 12249 Berlin, Germany<p>The chemical composition of metasediments is a valuable source of paleogeographic information about the protolith's sedimentary environment. Here, we compile major- and trace-element whole-rock data, including B contents, and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><msup><mi/><mrow><mn mathvariant="normal">10</mn><mo>/</mo><mn mathvariant="normal">11</mn></mrow></msup></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="547c313a8ba5718ee29d24f2c69c09d1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-33-401-2021-ie00001.svg" width="24pt" height="11pt" src="ejm-33-401-2021-ie00001.png"/></svg:svg></span></span>B-isotope ratios from the Permo-Triassic metasedimentary cover of the Pfitsch–Mörchner basin, overlying the Variscan basement in the western Tauern Window, Eastern Alps (Austria and Italy). The basement consists of orthogneiss (“Zentralgneis”, metamorphosed Variscan granitoids with intrusion ages between 305 and 280 Ma), and the roof pendant consists of granites (amphibolites, paragneiss, and minor serpentinites). The Zentralgneis is partly hydrothermally altered into pyrite quartzite with high Al–S contents, low Na–Sr–Ca–Mg contents, and very strong depletion of the light rare earth elements. Comparison with published detailed mapping of this and other time-equivalent basins in the western Tauern Window, with radiometric age data in the literature, and with unmetamorphosed basins in the South Alpine realm yields a late Permian to Early Triassic age of sedimentation.</p> <p>Although during Alpine metamorphism all rocks were strongly deformed, the whole-rock chemical compositions of the metasediments were not pervasively changed during deformation. We show that the sediments were deposited in a small, probably lacustrine–fluviatile, intramontane basin, under arid to semi-arid climatic conditions. The sequence starts with metaconglomerates, which can be interpreted as a mixture of the different basement rocks, based on a combination of major-element ratios Na<span class="inline-formula"><sub>2</sub></span>O <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e653eaf840568ee76bb20ba3bf368ae0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-33-401-2021-ie00002.svg" width="8pt" height="14pt" src="ejm-33-401-2021-ie00002.png"/></svg:svg></span></span> (Na<span class="inline-formula"><sub>2</sub></span>O <span class="inline-formula">+</span> K<span class="inline-formula"><sub>2</sub></span>O) and MgO <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="36bd7baae116a5efc17e692d563c2b51"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-33-401-2021-ie00003.svg" width="8pt" height="14pt" src="ejm-33-401-2021-ie00003.png"/></svg:svg></span></span> (MgO <span class="inline-formula">+</span> Fe<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>3</sub></span>) with concentrations of trace elements Cr, V, and Ni. The sequence is overlain by a fining-upwards sequence of clastic sediments, in which the behavior of K, Rb, and Sr allows the reconstruction of intense diagenetic K–B metasomatism, which raised the K<span class="inline-formula"><sub>2</sub></span>O contents up to <span class="inline-formula">∼</span> 10 wt %. The average B content of 218 <span class="inline-formula">µ</span>g g<span class="inline-formula"><sup>−1</sup></span> is well above the B content of common sediments, and the B-isotope composition reaches extremely low values of down to <span class="inline-formula">−33</span> ‰ <span class="inline-formula"><i>δ</i><sup>11</sup></span>B. The top of the sequence is a lazulite quartzite, interpreted as a former conglomeratic phosphatic sandstone, which marks the transition from a closed Permian basin to an open Triassic basin. Within the clastic sequence, the presence of hydrothermal tourmalinite veins documents a hydrothermal event after deposition but before the onset of Alpine metamorphism. A metamorphosed mafic dike swarm in the orthogneiss indicates a post-Variscan event of basaltic magmatism, and this event is tentatively correlated with increased heat flow in the Triassic basin and hydrothermal activity. A consistent conceptual model of this basin and its diagenetic modifications, based on a combination of geochemical data with petrographical and field information, provides the geodynamic context of the European margin at the onset of the Alpine orogeny.</p>https://ejm.copernicus.org/articles/33/401/2021/ejm-33-401-2021.pdf |
| spellingShingle | G. Franz M. Kutzschbach E. J. Berryman A. Meixner A. Loges A. Loges D. Schultze D. Schultze Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps) European Journal of Mineralogy |
| title | Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps) |
| title_full | Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps) |
| title_fullStr | Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps) |
| title_full_unstemmed | Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps) |
| title_short | Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps) |
| title_sort | geochemistry and paleogeographic implications of permo triassic metasedimentary cover from the tauern window eastern alps |
| url | https://ejm.copernicus.org/articles/33/401/2021/ejm-33-401-2021.pdf |
| work_keys_str_mv | AT gfranz geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT mkutzschbach geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT ejberryman geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT ameixner geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT aloges geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT aloges geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT dschultze geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps AT dschultze geochemistryandpaleogeographicimplicationsofpermotriassicmetasedimentarycoverfromthetauernwindoweasternalps |