Sutherland, R.; Toy, V.; Townend, J.; Eccles, J.; Prior, D.J.; Norris, R.J.; Mariani, E.; Faulkner, D.R.; de Pascale, G.; Carpenter, B.M.; Boulton, C.; Menzies, C.D.; Cox, S.C.; Little, T.A.; Hasting, M.; Cole-Baker, J.R.; Langridge, R.M.; Scott, H.R.; Lindroos, Z.R.; Fleming, B.; Wing, R. 2013 Operations and well completion report for boreholes DFDP-1A and DFDP-1B, Deep Fault Drilling Project, Alpine Fault, Gaunt Creek, New Zealand. Lower Hutt: GNS Science. GNS Science report 2011/48. 99 p.; doi: 10.21420/G2CP4X
Abstract: The first phase of the Deep Fault Drilling Project (DFDP-1), Alpine Fault, was carried out in January and February 2011 at Gaunt Creek, South Westland, New Zealand. Two boreholes, DFDP-1A and DFDP-1B, were drilled to depths of 101 m and 151 m respectively. DFDP-1A cored a hangingwall mylonite sequence containing cataclasite zones that increase in frequency downward; 20–30 m of cemented and hydrothermally altered cataclasites; a >5 cm-thick principal slip surface of ultracatalasite and gouge at 90 m; and footwall fluvial gravels to a total depth of 100.6 m. DFDP-1B cored a similar hangingwall sequence; encountered a principal slip surface with a thickness of about 20 cm at depth of 128 m; penetrated a footwall sequence of quartz- and feldspar-rich, extensively altered and variably cataclased rock including a significant fault at 130 m; and reached a total depth of 151.4 m. A broad suite of downhole geophysical logs was collected using acoustic televiewer, neutron, full-waveform sonic, density, dipmeter, and electromagnetic flowmeter sondes. A fault zone observatory was installed in the DFDP-1B borehole, consisting of a seismometer near the base; a 25 mm internal diameter alkathene fluid sampling tube (perforated above the seismometer in the footwall); four vibrating-wire piezometers with inbuilt temperature sensors; 20 platinum RTD temperature sensors on two separate strings; and surface infrastructure providing security and housing the power supply and recording equipment. DFDP-1A was cased to 81 m depth and had a seismometer installed at the base of the casing, connected to the observatory equipment mounted above DFDP-1B. (auth)
