Regional stratigraphic drilling program to obtain new core samples from the greenfield frontier basement beneath the covered Nullarbor Plain
The Coompana Drilling project forms a major part of, and is funded through, the Far West Discovery Program component of the South Australian Governments $20M PACE Copper initiative. Additional funding for the project comes from Geoscience Australia and the Australian Federal Governments Exploring for the Future initiative.
The primary objective of the Coompana Drilling Project is to obtain high quality drill core samples from the untested basement units beneath the Nullarbor Plain.
Due to the absence of basement outcrop, the newly acquired Coompana airborne magnetic survey and Coompana gravity survey have been used to sub-divide the Coompana Province into a series of domains with distinct geophysical characteristics (Fig. 1; See Wise, et al. (2015) for preliminary domain definitions based on the Coompana magnetic survey). These are interpreted to represent regions with distinct lithologies and geological histories. The aeromagnetic domains are consistent with the crustal blocks recognised in the 13GA-EG1 deep crustal seismic profile (Dutch, et al., 2016b). The SA Coompana Province also hosts a number of intriguing geophysical anomalies including the enigmatic Coompana Magnetic Anomaly (Wise, et al., 2015). This ~50km wide deep seated remanently magnetised anomaly is associated with a low density signature. The cause and significance of this anomaly is currently unknown.
Drill hole locations (Fig. 1) have been planned to intercept as many of the different geophysical domains as possible. These domains include the moderate magnetic intensity, low density domains with a defined NNE trending fabric (Domain 1; Fig 1) which likely represent the oldest protoliths in the region. Domain 2 is characterised by a variable, mottled magnetic signature with both high and low densities which may represent reworked basement by subsequent granitic intrusions (Fig 1). Domain 3 includes the prominent NE trending line of magnetic intrusions that bisects the province (Fig. 1). Finally, there is the main remanently magnetized Coompana Magnetic Anomaly itself and a number of possibly associated smaller satellite intrusions located coincident and adjacent to the main magnetic anomaly, but which are associated with density highs.
Approximately 18 new drill holes were planned as part of this project to intersect the above domains and other structures seen in the geophysical data (Fig. 1). The drill holes are located in the far south-west of South Australia: south of the Trans-Australia Railway, east of the SA/WA border, west of a line ~130.00°E and north of the Eyre Highway (Fig. 2).
Boart Longyear Australia were selected via an open competitive tender process to provide drilling services for the Coompana Drilling Project.
The drilling commenced in early April 2017 with the drilling of the first hole CDP001. A total of eight holes were completed during the program (Fig. 3; CDP001 – CDP008), which concluded in mid-September 2017. At completion we have retrieved more than 1800m of new oriented HQ3 diamond core samples of the cover and crystalline basement from beneath the Nullarbor Plain. As well as the core samples themselves, new downhole gamma and temperature logs were acquired to help constrain the stratigraphy of the overlying sediments and the thermal structure of the Coompana crust.
PACE Copper Coompana Drilling Project: Drillhole CDP001 preliminary field-data report
This report provides the first release of the preliminary data collected on-site during the drilling of drillhole CDP001. This compilation includes well completion information, location and site access data, results of pre-drilling cover geophysics and depth estimates as well as the field geological logs and acquired down-hole geophysical data.
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