GEOL 212 Study Guide - Quiz Guide: Oxygen-17, Per Mille, Seafloor Spreading
25 Dec 2017
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Document Summary
A major task of geochemists (regardless of where their samples come from) is finding ways to present data on concentrations of elements and their isotopes that make it easy to make comparisons. Previously we discussed one method chondrite normalization in which the concentration of an element in a given sample is expressed in comparison to its concentration in ci carbonaceous chondrites. A second geochemical convention involves expressing proportions of stable isotopes of a particular element. Recall that a given element may have several stable (i. e. non-radioactive) isotopes. Although globally, there are typical ratios of these isotopes, natural processes tend to sort or fractionate them in distinct ways. For example: carbon has two natural stable isotopes, On earth, much carbon is tied up in the biosphere. It gets there by way of photosynthesis, however photosynthesizing organisms have a strong preference for 12c.
