Research
Interests
Timing of low-temperature mineral formation during exhumation and cooling in the Central Alps, Switzerland
Research
Collaboratores:
Prof. Dr. Kurt Bucher, Institute for Geosciences Freiburg University,
Germany
PD Dr. Meinert Rahn, Eidgenössisches
Nuklearsicherheitsinspektorat ENS, Switzerland
Roelant vn der Lelij & Dr. Richard Spikings, Department of
Mineralogy, Université de Genève, Switzerland
| The
mineral assemblage quartz, laumontite and apophyllite-(KF) occur in a
fissure within the Southern Aar granite located in the Aar Massif
(Switzerland). They were formed during exhumation of the Alpine orogen
and laumontite and apophyllite marks the latest fissure minerals in the
Central Alps. A combined study of 40Ar/39Ar age dating, apatite fission
track (FT) and chemical characterization of tunnel and surface samples
are present to carry out the position of low-temperature water-rock
interaction in respect to the Alpine history. Apatite FT analysis yields an exhumation rate of 0.45 mm a-1, a cooling rate of 13 °C Ma-1 and a geothermal gradient of 28 °C km-1. Combining these with the 40Ar/39Ar plateau age for apophyllite of ∼2 Ma, a minimum formation temperature and depth of 70 °C and 2800 m, respectively can be assumed. Temperature-time evolution of fissures in the Aar Massif and thermodynamic mineral evolution indicate that laumontite were formed between 7 and 2 Ma before present at temperatures between 150 and 70 °C. Elements for laumontite formation derived during dissolution of primary minerals. Changes of laumontite chemistry could be an effect of temperature drop or a change in fluid chemistry that would be supported by later apophyllite formation. Reference: Weisenberger T., Rahn M. van der Lelji R., Spikings R. & Bucher K. Timing of low-temperature mineral formation during exhumation and cooling in the Central Alps, Switzerland. Earth and Planetary Science Letters (accepted). doi: 10.1016/j.epsl.2012.01.007 |
