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LoginKnowledge about the order and timing of geological events is an essential part of understanding how ore deposits have formed. A robust geological model including the timing of events can aid in the prediction of where other deposits could have formed and for robust resource models. As such, geochronology is an essential tool for geologists at multiple stages of exploration and mining.
Rhenium has two naturally occurring isotopes, 185Re which is stable and 187Re which decays to stable 187Os (Faure, 1977). As rhenium effectively substitutes for Mo in molybdenite but Os is not incorporated into the mineral, the 187Os present in molybdenite is from the decay of 187Re (Stein et al., 2001). Using the concentration of 187Os, 187 Re and the decay constant for 187Re the age of the molybdenite formation can be determined.
Method Re-ISTP01 is offered for molybdenite. Rock or drill core must be received whole as steel jaw crushing will contaminate the sample with Re. Age can only be determined for rocks of >0.5 Ma, and the molybdenite separate must contain >100ppm Re.
| Code | Analyte | Description |
|---|---|---|
| Re-ISTP01 | Re/Os | Specific to molybdenite. Rock or drill core must be received whole as steel jaw crushing will contaminate the sample with Re. Age can only be determined for rocks of >0.5 Ma, and the molybdenite separate must contain >100ppm Re. Price includes mineral separation, solvent extraction, column separation and TIMS analysis. TAT is 70 days. |
The isotope 40Ar is the stable daughter product of 40K decay. Potassium bearing samples are irradiated to change 39K to 39Ar and measured for their 40Ar/ 39Ar composition. As the radiogenic 40Ar is a result of 40K decay, the mineral formation time can be determined based on the 40Ar/ 39Ar and the half-life of 40K (Faure, 1977).
Method Ar-ISTP01 is performed on targeted minerals. Rock and drill core should be submitted intact or crushed only as sample prep is included. Measurement is by irradiation and step heating in a mass spectrometer.
| Code | Analyte | Description |
|---|---|---|
| Ar-ISTP01 | Ar/Ar | Done on targeted minerals. Rock and drill core should be submitted intact or crushed only, as sample prep is included in the price. Measurement by irradiation and step heating in a mass spectrometer. Price includes sample preparation. Turnaround time approximately 12 months. |
Faure, G., 1977. Principles of Isotope Geology. Second Edition. John Wiley and Sons.
Stein, H.J., Markey, R.J., Morgan, J.W., Hannah, J.L., and Schersten, A., 2001. The remarkable Re-Os chronometer in molybdenite: how and why it works. Terra Nova, Vol13, No. 6, pp 479-486.
Some minerals will be identifiable by visual inspection, such as molybdenite and biotite. Others may be predicted based on the chemistry of the whole rock. Rocks that have high concentrations of Zr identified in geochemistry will likely have zircon as this is the mineral that hosts most Zr.
