Dating tectonic activity in the Lepontine Dome and Rhone-Simplon Fault regions through hydrothermal monazite-(Ce)

• Verfasst von: Bergemann, Christian A. [VerfasserIn]
• Titel: Dating tectonic activity in the Lepontine Dome and Rhone-Simplon Fault regions through hydrothermal monazite-(Ce)
• Verf.angabe: Christian A. Bergemann, Edwin Gnos, Alfons Berger, Emilie Janots, and Martin J. Whitehouse
• E-Jahr: 2020
• Jahr: 21 February 2020
• Umfang: 24 S.
• Teil: volume:11
• Teil: year:2020
• Teil: number:1
• Teil: pages:199-222
• Teil: extent:24
• Fussnoten: Gesehen am 31.03.2020
• Titel Quelle: Enthalten in: Solid earth
• Ort Quelle: Göttingen : Copernicus Publ., 2010
• Jahr Quelle: 2020
• Band/Heft Quelle: 11(2020), 1, Seite 199-222
• ISSN Quelle: 1869-9529
• DOI: doi:10.5194/se-11-199-2020
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1693625199

Abstract

<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&thinsp;<span class="inline-formula">Ma</span>, with individual grains recording age ranges of 2 to 7.5&thinsp;<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&thinsp;<span class="inline-formula">Ma</span>, respectively, while crystallization of monazite-(Ce) in the eastern Lepontine Dome started later, at 15-10&thinsp;<span class="inline-formula">Ma</span>. Fissure monazite-(Ce) along the western limit of the dome reports younger ages of 13-7&thinsp;<span class="inline-formula">Ma</span>. A younger age group around 8-5&thinsp;<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>