Eucla basement project

In Western Australia these basement provinces are the Madura Province and the Forrest Zone of the Coompana Province. They are covered by up to 300 m of younger basin rocks of the Cretaceous Madura Shelf, which is overlain by up to 200 m of Eocene limestone sequences of the Eucla Basin, forming the Nullarbor Plain. The lack of exposure of any Precambrian rocks means the project is totally reliant on geophysical data interpretation and drillcores.

The Eucla basement stratigraphic drilling program, funded through the Exploration Incentive Scheme (EIS), was established to provide high-quality diamond cores of the basement from well-defined geophysical domains. The results of the drilling program were presented at a public workshop in September 2015. Topics included:

• drilling techniques and core acquisition
• lithological and structural features
• sulfides, veins and alteration
• implications for geophysical data interpretations
• geochronology
• geochemistry, isotopes and crustal evolution
• tectonic settings and implications for geodynamics and prospectivity
• geology of the cover sequences.

The presentations are available in the table below. Extended abstracts and Whole-rock major and trace element geochemistry data on diamond drillcore samples from the Madura Province and Forrest Zone (Excel table) are also available. Whole-rock assay data on diamond drillcore altered samples from the Madura Province and Forrest Zone (Excel table) are available here.

The drilling program has provided a wealth of new data and increased our knowledge of the basement provinces that are missing links in understanding Proterozoic Australian geology. Combined with work on existing EIS co-funded and donated company cores, the new drillcores also provide insight into the prospectivity of the vast region that lies beneath the Nullarbor Plain.

The stratigraphic drilling program has also provided valuable experience and knowledge of the challenging ground conditions associated with drilling in the Nullarbor region. Both RC and mud-rotary techniques have been trialled and assessed as alternative techniques for getting through the cover to basement, which was intersected at depths between 250 and 440 m.