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Victoria University Antarctic Research Expedition Science and Logistics Reports 2000-01: VUWAE 45

Notes for Hydrocarbon Sampling of Frozen Core

Notes for Hydrocarbon Sampling of Frozen Core.

At Scott Base during the field preparation period in early November we cored frozen volcanic sediments and bedrock to test the drilling equipment using chilled compressed air and diamond drill bits. This was carried out in the road area adjacent to the Pump House and WetLab in an area which was expected to have some possible hydrocarbon contamination. The coring operation went very well with complete core recovery of a few centimetres of sediment on top of vesicular basaltic bedrock. The total core recovered was in excess of 1.0 metre. Vesicles and fractures in the bedrock were filled with ice that was recovered intact. At the time of core recovery a hydrocarbon smell was noted on several occasions but this disappeared after a few hours and the ice content also ablated away even though the cores were kept frozen. It was not clear if the hydrocarbon smell was associated with the ice content but this could be possible at shallow depths were flowing water and hydrocarbons may be present during the high summer melt page break period. The relationship between ice content and the volatile hydrocarbons may indicate how fluids move in the subsurface and at the permafrost interface.

We recommend that compressed air coring should be carried out with Ambient air temperatures not greater than −10°C to prevent downhole melting. Samples of core should be taken immediately on recovery of the core, stored in airtight containers to preserve both volatile and residual hydrocarbons and kept frozen −18°C. Containers where the headspace can be drawn off with a syringe for gas chromatograph analysis would be advantageous.