c. Methodology

Sampling sites were selected for the occurrence of massive relict ice. At each site, a 1.5 square metre pit was dug into the ice free soil or sediment above the relict ice. In some areas ice cemented sediment was above the relict ice. This was sampled by means of a small gasoline powered hammer drill with a diamond or carbide core bit. Once into the relatively sediment-free relict ice, a sipre auger with carbide cutters was used to core to a depth of about one metre.

Ian Graham and co-workers at GNS, Lower Hutt, will carry out the dating method using atmospheric ¹⁰Be. The procedure will be similar to that used in previous studies (Dickinson et al. 2003b; Graham et al. 1995; Graham et al. 2002). To streamline the method, we will only process the >62 micron fraction of sediment which we believe contains most of the Be.

Samples of granite used for fingerprinting will be cut (1-2 cm² slabs) and rough polished. These will be placed in a laser ablate chamber attached to a multi-collector mass spectrometer. Lead isotopes 204,206 and 207 will be measured in the feldspars of each sample. Plots of ²⁰⁷Pb/²⁰⁴Pb vs ²⁰⁶Pb/²⁰⁴Pb will show areas of feldspar genesis which are unique to the magma bodies where granitic rocks crystallize. The Lead isotopic composition of feldspars are incorporated at the time of crystallization and form distinctive signatures which can be used for tracing the origin of the feldspar.