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Radiogenic Isotope Laboratory - Denver

Radioactive Isotopes: Rb-Sr System

Rubidium is an alkai metal and strontium is an alkaline earth element linked by radioactive decay. Rubidium and strontium are distributed in a wide variety of rocks and minerals in various concentrations. It is possible to date both igneous and sedimentary rocks by these techniques. Sr-isotope stratigraphy is another dating technique available. Both rubidium and strontium are very useful for tracing geologic processes.

Geochronology and thermal history

Examples of Applications:

• determine emplacement ages or cooling ages of specific minerals
• age of metamorphism

Sr-isotope stratigraphy

Strontium-isotope stratigraphy is a method that uses extremely precise Sr-isotope measurements of marine fossils in conjunction with the changing Sr-isotopic composition of seawater through time to provide an age for the fossil. This technique can also be used to determine ages for other geologic processes, such as dolomitization.

Examples of Applications:

• Correlating and dating of marine carbonates, evaporites and phosphorites
• relative and absolute ages of Quaternary marine terraces
• glacial-interglacial timing
• history of sea level change

Sr as an isotopic tracer

Examples of Applications:

• groundwater flow conditions, circulation and mixing patterns
• identifying isotopic signatures of mass extinction events
• mineral weathering reactions
• chemical modeling of carbonate diagenesis
• diet and grazing patterns of birds, animals, etc.
• studies of ancient ocean chemistry and circulation
• source of dissolved and suspended constituents of rivers
• magma evolution and sources
• identifying metalliferous origins

Information About:

U-Th-Pb

Nd-Sm

More About the Radiogenic Isotope Laboratory

Radiogenic Isotope Laboratory Introduction

Radiogenic Isotopes

Thermal Ionization Mass Spectrometry

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U.S. Department of the Interior | U.S. Geological Survey
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Page Last Modified: Tue 14-Feb-2006 13:02:40 MST