PRISE Examples of Applications
A few examples of geochronology and radiogenic isotope studies currently being carried out by PRISE.
Zircon, Titanite (Sphene), Rutile, Baddeleyite, Monazite, Perovskite, Cassiterite
All of the above phases are amenable to U-Pb dating either by SHRIMP or conventional isotope dilution (IDTIMS). The particular phase chosen for analysis depends on the geological problem to be solved.
Direct dating of mineralisation
Many mineralised systems can either be dated directly (e.g. U-Pb on cassiterite or Re-Os on molybdenite) or have phases that can be analysed in situ in the textural equilibrium with the economic phase (e.g. rutile associated with Au). Analysis of such systems in situ enables the timing of mineralisation to be studied and documented.
Tracing Sources with Neodymium (Nd)
Samarium-Neodymium (Sm-Nd) is a very powerful isotopic tool to trace the source(s) of igneous rocks in particular and other rocks in general.
Nd isotopic mapping has far-reaching applications in regional and exploration geology.
Sm-Nd analyses are carried out in conjunction with U-Pb zircon dating. Using the accurate zircon crystallisation ages one can calculate meaningful initial Nd isotopic compositions (eNd) and so gain an insight into the crustal history and source of for example a granite.
Rhenium Osmium (Re-Os)
The siderophile/chalcophile characteristics of Re and Os make this isotopic system appropriate to problems of ore genesis. Re-Os ages of molybdenite, pyrite, chalcopyrite, chromite and gold directly date ore deposits, while the initial Os isotopic ratios are used to trace source(s) of the metals.
Re-Os has important applications in igneous petrogenesis.
Fluorite
Fluorite is a common phase in hydrothermal ore systems. Internal chemical variations of the REE mean that the Sm-Nd method can be used to date the time of hydrothermal activity.
Provenance and Correlation of Sediments
U-Pb dating of detrital minerals enables compilation of a relative probability distribution and so one can examine the provenance of sediments. The data by default place a maximum age for deposition. Such probability patterns can be used to correlate like sediments, a powerful tool in basin analysis.
Carbonates
High precision Sr isotope analyses of seawater carbonate phases can accurately place a sample in the Tertiary Time Scale. This has relevance to continental margins and petroleum exploration. Pb isotopic analyses of carbonates can be used to determine the age of formation.
Databases
Through both collaborative projects and their own research PRISE scientists have developed extensive geochronological and isotopic databases for many parts of the world. Access to these resources can be provided to suit specific requirements.
