A famous rubidium (Rb)-strontium (Sr) isochron work was caried out on the Baltimore gneiss from the USA by Wetherill et al. (1968) ) Write down the "master age equation" for the Rb to 3Sr decay scheme (Sr is conrventionally used as the stable reference isotope of Sr). Hint this ia in the lecture notes, or on page 188 of the Gill textbook, Chapter 10 (equation 10.4.7). b) Draw the whole-rock"Sr*Sr ()versus Rbe(x) isochron and the biotte-whole rock isochrons for the samples which data are given in the Table below (note: you will need two graphs with different scales one for the whole rocks and one for the minerals). c) Infer the emplacement age (whole rock isochron) and the resetting or metamorphic age (mineral isochron) of hese rocks om tese a rota s Rd 1.42 x 1o-n yr') B105 whole rock B20C whole rock: B20 whole rock B20 biotie B41 whole rock B41 biotne B4 whole roc: Rb Sr 2.244 3.642 3.628 16.4 6.59 289 0.2313 0.7380 0.7612 0.7573 .2146 0.7992 1.969 0.7074
