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The application of Sr isotope stratigraphy is generally limited to carbonate samples for which the Sr seawater curve is well defined.
This is well known for the Cenozoic time-scale but, due to poorer preservation of carbonate sequences in the Mesozoic and earlier, it is not completely understood for older sequences.
Different minerals in a given geologic setting can acquire distinctly different ratios of radiogenic strontium-87 to naturally occurring strontium-86 (Sr as the parent melt.
Thus, assigning age significance to a result requires studying the metasomatic and thermal history of the rock, any metamorphic events, and any evidence of fluid movement.Rb and Sr are relatively mobile alkaline elements and as such are relatively easily moved around by the hot, often carbonated hydrothermal fluids present during metamorphism or magmatism.Conversely, these fluids may metasomatically alter a rock, introducing new Rb and Sr into the rock (generally during potassic alteration or calcic (albitisation) alteration.The slope of the line dictates the age of the sample.Rb-Sr dating relies on correctly measuring the Rb-Sr ratio of a mineral or whole rock sample, plus deriving an accurate One of the major drawbacks (and, conversely, the most important use) of utilizing Rb and Sr to derive a radiometric date is their relative mobility, especially in hydrothermal fluids.