Ancient Subsurface Cracks May Point to Mineral Deposits

Gold vein in an old crack

CHINA’S stated intention to restrict vanadium exports may stimulate greater Australian efforts to mine it, so it comes as good timing that geologists are finding prospective areas for vanadium and titanium in the Kimberley.

The work is part of Geological Survey of Western Australia-funded research which is adding to knowledge of the poorly-understood Kimberley Craton, a former tectonic plate now welded to the North Australia and Pilbara Cratons.

Much of the craton is covered by two sedimentary basins, one above the other, known as the Kimberley Basin and below it, the Speewah Basin.

The research involved detecting old sub-surface cracks in the landscape called Hart Dolorites which occurred about 1797 million years ago and was led by University of Tasmania research fellow Karin Orth.

The Hart Dolerites appear to have once acted as conduits for magma forcing its way upwards through weaker sections of the region’s rock strata, Dr Orth says.

The team analysed samples from Hope Creek near the Yampi Peninsula which show vanadium, titanium and iron levels comparable to geologically-similar structures at Speewah Dome in the East Kimberley.

As vanadium and titanium have been found at the Speewah Dome, she says other Hart Dolorite structures should be prospective for those minerals.
Dr Orth discovered the Hart Dolerites by walking transect lines in remote regions and at the same time she collected samples, took measurements and made notes on a tablet computer with a GPS that geolocated the data she entered.

Back in the office she submitted samples for geochemistry analysis and sometimes for dating, overlaying the data with geophysical data and Landsat images.

“In the field we’d also be taking measurements of some of the properties of those rocks that we then would sample,” she says.

“That can then be used to see how it relates to those more regional datasets.”

While larger Hart Dolorite structures occur along the Carr-Boyd Ranges, Bob Black Hills and Leopold Ranges, there are smaller structures in the northern Kimberley, north of the present-day Gibb River Road.

They take the form of eroding rocky outcrops with little vegetation, the eroded material forming black soil plains that are valuable grazing land.

If these structures prove to contain vanadium it would require ready access to roads or wharves to turn them into payable mines.



Note: The above post is reprinted from materials provided by ScienceNetwork WA. The original article was written by Geoff Vivian.