Computer Science
Scientific paper
Jul 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986e%26psl..78..355d&link_type=abstract
Earth and Planetary Science Letters, Volume 78, Issue 4, p. 355-367.
Computer Science
9
Scientific paper
The Hercynian schists and granites of the Helvetic basement (Aar Massif) in the Central Swiss Alps are overprinted by low-grade Alpine metamorphism and associated deformation. Rb/Sr and K/Ar ages of biotites are systematically reset by the later greenschist facies event. This rejuvenation is apparently controlled by temperature, mineral chemistry and grain size and independent of deformation and exsolution. Thermally activated volume diffusion best explains this behaviour with Ar and Sr having similar activation energies, and diffusion rates for Sr showing a greater dependence on biotite composition. Feldspars and apatite also show increasing equilibration to the Alpine event and together with Alpine equilibria in the micas reveal important changes in the isotopic compositions of exchanging reservoirs. These spatial and temporal variations must be assessed before true mineral ages can be calculated. Generally the higher-grade equilibria show less radiogenic exchange reflecting increased dilution by external fluids of radiogenic components released at the main front of isotopic resetting.
Rb/Sr ages of Alpine muscovites in the granites suggest a maximum possible age of metamorphism of 25 Ma in this low-grade area. This implies significant diachroneity in the timing of peak metamorphism in the Central Alps, with the relatively delayed metamorphism in this area a reflection of the later initial thickening and delayed uplift of the Helvetic basement.
Present address: Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 0QU, U.K.
No associations
LandOfFree
Isotope systematics in minerals: biotite rejuvenation and exchange during Alpine metamorphism does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Isotope systematics in minerals: biotite rejuvenation and exchange during Alpine metamorphism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Isotope systematics in minerals: biotite rejuvenation and exchange during Alpine metamorphism will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1655028