Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland
<p>Modern-style plate tectonics is characterised by the global operation of cold and deep subduction involving blueschist facies and ultrahigh-pressure metamorphism. This has been a common process since the Neoproterozoic, but a couple of studies indicate similar processes were active in the P...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-07-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/35/479/2023/ejm-35-479-2023.pdf |
| _version_ | 1797778327892656128 |
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| author | J. Schönig C. Benner G. Meinhold H. von Eynatten N. K. Lünsdorf |
| author_facet | J. Schönig C. Benner G. Meinhold H. von Eynatten N. K. Lünsdorf |
| author_sort | J. Schönig |
| collection | DOAJ |
| description | <p>Modern-style plate tectonics is characterised by the
global operation of cold and deep subduction involving blueschist facies and
ultrahigh-pressure metamorphism. This has been a common process since the
Neoproterozoic, but a couple of studies indicate similar processes were
active in the Paleoproterozoic, at least on the local scale. Particularly
conspicuous are extreme ultrahigh-pressure conditions of <span class="inline-formula">∼</span> 7 GPa at thermal gradients <span class="inline-formula"><i><</i></span> 150 <span class="inline-formula"><sup>∘</sup></span>C GPa<span class="inline-formula"><sup>−1</sup></span> proposed for
metamorphic rocks of the Nordre Strømfjord shear zone in the western part
of the Paleoproterozoic Nagssugtoqidian Orogen of Greenland. By acquiring a
large dataset of heavy minerals (<span class="inline-formula"><i>n</i></span> <span class="inline-formula">=</span> 52 130) and garnet major-element
composition integrated with mineral inclusion analysis (<span class="inline-formula"><i>n</i>=2669</span>) from
modern sands representing fresh and naturally mixed erosional material from
the metamorphic rocks, we here intensely screened the area for potential
occurrences of ultrahigh-pressure rocks and put constraints on the
metamorphic evolution. Apart from the absence of any indications pointing to
ultrahigh-pressure and low-temperature–high-pressure metamorphism, the
results are well in accordance with a common Paleoproterozoic
subduction–collision metamorphic evolution along a Barrovian-type
intermediate temperature and pressure gradient with a pressure peak at the
amphibolite–granulite–eclogite-facies transition and a temperature peak
at medium- to high-pressure granulite-facies conditions. In addition, we
discuss that all “evidence” for ultrahigh-pressure metamorphism proposed
in the literature for rocks of this area is equivocal. Accordingly, the
Nordre Strømfjord shear zone is not an example of modern-style plate
tectonics in the Paleoproterozoic or of very low thermal gradients and
extreme pressure conditions in general.</p> |
| first_indexed | 2024-03-12T23:15:37Z |
| format | Article |
| id | doaj.art-a4d4d44e14e242e295e963efa0efc5de |
| institution | Directory Open Access Journal |
| issn | 0935-1221 1617-4011 |
| language | English |
| last_indexed | 2024-03-12T23:15:37Z |
| publishDate | 2023-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | European Journal of Mineralogy |
| spelling | doaj.art-a4d4d44e14e242e295e963efa0efc5de2023-07-17T07:16:13ZengCopernicus PublicationsEuropean Journal of Mineralogy0935-12211617-40112023-07-013547949810.5194/ejm-35-479-2023Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western GreenlandJ. Schönig0C. Benner1G. Meinhold2H. von Eynatten3N. K. Lünsdorf4Department of Sedimentology and Environmental Geology, Geoscience Center Göttingen, University of Göttingen, 37077 Göttingen, GermanyDepartment of Sedimentology and Environmental Geology, Geoscience Center Göttingen, University of Göttingen, 37077 Göttingen, GermanyInstitute of Geology, TU Bergakademie Freiberg, 09599 Freiberg, GermanyDepartment of Sedimentology and Environmental Geology, Geoscience Center Göttingen, University of Göttingen, 37077 Göttingen, GermanyDepartment of Sedimentology and Environmental Geology, Geoscience Center Göttingen, University of Göttingen, 37077 Göttingen, Germany<p>Modern-style plate tectonics is characterised by the global operation of cold and deep subduction involving blueschist facies and ultrahigh-pressure metamorphism. This has been a common process since the Neoproterozoic, but a couple of studies indicate similar processes were active in the Paleoproterozoic, at least on the local scale. Particularly conspicuous are extreme ultrahigh-pressure conditions of <span class="inline-formula">∼</span> 7 GPa at thermal gradients <span class="inline-formula"><i><</i></span> 150 <span class="inline-formula"><sup>∘</sup></span>C GPa<span class="inline-formula"><sup>−1</sup></span> proposed for metamorphic rocks of the Nordre Strømfjord shear zone in the western part of the Paleoproterozoic Nagssugtoqidian Orogen of Greenland. By acquiring a large dataset of heavy minerals (<span class="inline-formula"><i>n</i></span> <span class="inline-formula">=</span> 52 130) and garnet major-element composition integrated with mineral inclusion analysis (<span class="inline-formula"><i>n</i>=2669</span>) from modern sands representing fresh and naturally mixed erosional material from the metamorphic rocks, we here intensely screened the area for potential occurrences of ultrahigh-pressure rocks and put constraints on the metamorphic evolution. Apart from the absence of any indications pointing to ultrahigh-pressure and low-temperature–high-pressure metamorphism, the results are well in accordance with a common Paleoproterozoic subduction–collision metamorphic evolution along a Barrovian-type intermediate temperature and pressure gradient with a pressure peak at the amphibolite–granulite–eclogite-facies transition and a temperature peak at medium- to high-pressure granulite-facies conditions. In addition, we discuss that all “evidence” for ultrahigh-pressure metamorphism proposed in the literature for rocks of this area is equivocal. Accordingly, the Nordre Strømfjord shear zone is not an example of modern-style plate tectonics in the Paleoproterozoic or of very low thermal gradients and extreme pressure conditions in general.</p>https://ejm.copernicus.org/articles/35/479/2023/ejm-35-479-2023.pdf |
| spellingShingle | J. Schönig C. Benner G. Meinhold H. von Eynatten N. K. Lünsdorf Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland European Journal of Mineralogy |
| title | Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland |
| title_full | Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland |
| title_fullStr | Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland |
| title_full_unstemmed | Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland |
| title_short | Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland |
| title_sort | detrital garnet petrology challenges paleoproterozoic ultrahigh pressure metamorphism in western greenland |
| url | https://ejm.copernicus.org/articles/35/479/2023/ejm-35-479-2023.pdf |
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