EARTH221 Lecture Notes - Lecture 9: Geochronology, Exponential Decay, Molybdenite
26 Aug 2016
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Lecture 9: daughter is not taken up into a mineral at the time of formation or, daughter is present in the mineral/rock at time of formation. Known (measured experimentally) and does not change w/time and constant under variable geological conditions (pressure/temp) All sample must be the same age and are co-genetic. If daughter atoms initially present, then all the samples must have the same initial daughter isotope composition. If there is a negative slope at time of formation (samples not same) then an erroneously young age would result. No disturbance to the isotope system (ie. closed system) Good range in present-day concentrations of parent and daughter or isotope ratios. 187 re 187 os: redox sensitive elements, these elements are soluble in water. Mswd =1 good (all of the scatter above regression line come from analysis and not samples, all the assumptions met) Mswd > 1 bad (scattered data points above the regression line, assumptions violated ex.
