Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets
Understanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study of two high-viscosity dykes (10<sup>6</sup> Pa·s) in the Chachahuén...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-10-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/11/10/1113 |
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| author | Tobias Schmiedel Steffi Burchardt Tobias Mattsson Frank Guldstrand Olivier Galland Joaquín Octavio Palma Henrik Skogby |
| author_facet | Tobias Schmiedel Steffi Burchardt Tobias Mattsson Frank Guldstrand Olivier Galland Joaquín Octavio Palma Henrik Skogby |
| author_sort | Tobias Schmiedel |
| collection | DOAJ |
| description | Understanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study of two high-viscosity dykes (10<sup>6</sup> Pa·s) in the Chachahuén volcano, Argentina, the Great Dyke and the Sosa Dyke. To quantify dyke geometries, magma flow indicators, and magma viscosity, we combine photogrammetry, microstructural analysis, igneous petrology, Fourier-Transform-Infrared-Spectroscopy, and Anisotropy of Magnetic Susceptibility (AMS). Our results show that the dykes consist of 3 to 8 mappable segments up to 2 km long. Segments often end in a bifurcation, and segment tips are predominantly oval, but elliptical tips occur in the outermost segments of the Great Dyke. Furthermore, variations in host rocks have no observable impact on dyke geometry. AMS fabrics and other flow indicators in the Sosa Dyke show lateral magma flow in contrast to the vertical flow suggested by the segment geometries. A comparison with segment geometries of low-viscosity dykes shows that our high-viscosity dykes follow the same geometrical trend. In fact, the data compilation supports that dyke segment and tip geometries reflect different stages in dyke emplacement, questioning the current usage for final sheet geometries as proxies for emplacement mechanism. |
| first_indexed | 2024-03-10T06:21:30Z |
| format | Article |
| id | doaj.art-d3626fe7ddd7429dbce554761489fa0e |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-10T06:21:30Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-d3626fe7ddd7429dbce554761489fa0e2023-11-22T19:17:03ZengMDPI AGMinerals2075-163X2021-10-011110111310.3390/min11101113Emplacement and Segment Geometry of Large, High-Viscosity Magmatic SheetsTobias Schmiedel0Steffi Burchardt1Tobias Mattsson2Frank Guldstrand3Olivier Galland4Joaquín Octavio Palma5Henrik Skogby6Department of Earth Sciences, Uppsala University, 75236 Uppsala, SwedenDepartment of Earth Sciences, Uppsala University, 75236 Uppsala, SwedenSchool of Earth and Environmental Sciences, University of St. Andrews, St. Andrews KY16 9TS, UKThe NJORD Centre, Department of Geosciences, University of Oslo, 0316 Oslo, NorwayThe NJORD Centre, Department of Geosciences, University of Oslo, 0316 Oslo, NorwaySubsecretariat of Mining of the Province of Buenos Aires, La Plata 1900, ArgentinaDepartment of Geosciences, Swedish Museum of Natural History, 10405 Stockholm, SwedenUnderstanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study of two high-viscosity dykes (10<sup>6</sup> Pa·s) in the Chachahuén volcano, Argentina, the Great Dyke and the Sosa Dyke. To quantify dyke geometries, magma flow indicators, and magma viscosity, we combine photogrammetry, microstructural analysis, igneous petrology, Fourier-Transform-Infrared-Spectroscopy, and Anisotropy of Magnetic Susceptibility (AMS). Our results show that the dykes consist of 3 to 8 mappable segments up to 2 km long. Segments often end in a bifurcation, and segment tips are predominantly oval, but elliptical tips occur in the outermost segments of the Great Dyke. Furthermore, variations in host rocks have no observable impact on dyke geometry. AMS fabrics and other flow indicators in the Sosa Dyke show lateral magma flow in contrast to the vertical flow suggested by the segment geometries. A comparison with segment geometries of low-viscosity dykes shows that our high-viscosity dykes follow the same geometrical trend. In fact, the data compilation supports that dyke segment and tip geometries reflect different stages in dyke emplacement, questioning the current usage for final sheet geometries as proxies for emplacement mechanism.https://www.mdpi.com/2075-163X/11/10/1113magma transporthigh-viscosity dykesshallow crustigneoussillsChachahuen volcano |
| spellingShingle | Tobias Schmiedel Steffi Burchardt Tobias Mattsson Frank Guldstrand Olivier Galland Joaquín Octavio Palma Henrik Skogby Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets Minerals magma transport high-viscosity dykes shallow crust igneous sills Chachahuen volcano |
| title | Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets |
| title_full | Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets |
| title_fullStr | Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets |
| title_full_unstemmed | Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets |
| title_short | Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets |
| title_sort | emplacement and segment geometry of large high viscosity magmatic sheets |
| topic | magma transport high-viscosity dykes shallow crust igneous sills Chachahuen volcano |
| url | https://www.mdpi.com/2075-163X/11/10/1113 |
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