Dating tectonic activity in the Lepontine Dome and Rhone-Simplon Fault regions through hydrothermal monazite-(Ce)
<p><strong>Abstract.</strong> Zoned hydrothermal monazite-(Ce) from Alpine-type fissures and clefts is used to gain new insights into the tectonic history of the Lepontine Dome in the Central Alps and the timing of deformation along the Rhone-Simplon Fault zone on the dome's w...
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
21 February 2020
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| In: |
Solid earth
Year: 2020, Volume: 11, Issue: 1, Pages: 199-222 |
| ISSN: | 1869-9529 |
| DOI: | 10.5194/se-11-199-2020 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.5194/se-11-199-2020 Verlag, lizenzpflichtig, Volltext: https://www.solid-earth.net/11/199/2020/ 
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| Author Notes: | Christian A. Bergemann, Edwin Gnos, Alfons Berger, Emilie Janots, and Martin J. Whitehouse |
| Summary: | <p><strong>Abstract.</strong> Zoned hydrothermal monazite-(Ce) from Alpine-type fissures and clefts is used to gain new insights into the tectonic history of the Lepontine Dome in the Central Alps and the timing of deformation along the Rhone-Simplon Fault zone on the dome's western end. Hydrothermal monazites-(Ce) (re)crystallization ages directly date deformation that induces changes in physicochemical conditions of the fissure or cleft fluid. A total of 480 secondary ion mass spectrometry (SIMS) spot analyses from 20 individual crystals, including co-type material of the monazite-(Nd) type locality, record ages for the time of <span class="inline-formula">∼19</span> to 2.7 <span class="inline-formula">Ma</span>, with individual grains recording age ranges of 2 to 7.5 <span class="inline-formula">Myr</span>. The combination of these age data with geometric considerations and spatial distribution across the Lepontine region gives a more precise young exhumation history for the area. At the northeastern and southwestern edges of the Lepontine Dome, units underwent hydrothermal monazite-(Ce) growth at 19-12.5 and 16.5-10.5 <span class="inline-formula">Ma</span>, respectively, while crystallization of monazite-(Ce) in the eastern Lepontine Dome started later, at 15-10 <span class="inline-formula">Ma</span>. Fissure monazite-(Ce) along the western limit of the dome reports younger ages of 13-7 <span class="inline-formula">Ma</span>. A younger age group around 8-5 <span class="inline-formula">Ma</span> is limited to fissures and clefts associated with the Simplon normal fault and related strike-slip faults such as the Rhone Fault. The data set shows that the monazite-(Ce) age record directly links the fluid-induced interaction between fissure mineral and host rock to the Lepontine Dome's evolution in space and time. A comparison between hydrothermal monazite-(Ce) and thermochronometric data suggest that hydrothermal monazite-(Ce) dating may allow us to identify areas of slow exhumation or cooling rates during ongoing tectonic activity.</p> |
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| Item Description: | Gesehen am 31.03.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1869-9529 |
| DOI: | 10.5194/se-11-199-2020 |