ASAC project 1066 conducted Samarium-Neodymium isochron dating of recrystallised mafic dykes located in the SW perimeter of the Vestfold Hills. These dykes have experienced amphibolite-facies metamorphism, but the timing of this event is uncertain though many workers in the region postulate an age of ~1000 Ma or ~500Ma. Project 1066 provided preliminary data that suggests that this ... amphibolite-facies event in the southwest Vestfold Hills occurred at ~730 Ma.
Further work is underway (project 1248) to confirm and expand on the initial data.
The data are available from the url given below.
The data are mineral isotopic data for Samarium (Sm) and Neodymium (Nd). The samples are from mafic dykes from the southwest region of the Vestfolds Hills which were metamorphosed at upper amphibolite facies. the columns in order from left to right are:
1) Sample number (this refers to the individual mineral separate for each rock sample ie sample 28, 35, 36, 38, 39 are from rock sample 9B), sample 30, 31, 32, 34, 40 are from rock sample 8A)
2) the measured ratio of 147Sm to 144Nd
3) the error on that measurement at 95% confidence limits
4) the measured ratio of 143Nd to 144 Nd
5) the error on that measurement
The comment boxes contain the results of the analysis for each rock sample - ie the age of upper amphibolite metamorphism of the southwest Vestfold hills is 735.8 +/- 9.7 Ma (sample 9B) and 714 +/- 38Ma (sample 8a).
The work was conducted by Dr Jon Woodhead at the School of Earth Science, University of Melbourne.