Columbus Salt Marsh
The Columbus Salt Marsh project is located 45 kilometres northwest of Clayton Valley (Nevada, USA). The Columbus Salt Marsh valley represents a closed basin with extensive Tertiary volcanic deposits in the surrounding hills. USGS open file gravity data indicates that the centre of the valley has subsided up to 3.5km. The valley is fault bounded and several geothermal springs discharge alkali salts onto the lake surface. These alkali deposits have in the past been mined for borax.
Drilling conducted during 2018 (drill hole CBD-01) was designed to investigate a highly conductive zone extending from 600 metres to more than 1,000 meters below surface interpreted in 2-dimensional audio magnetotelluric (2D AMT) survey data (ASX releases 10 January 2018, 02 February 2018 ). A brine located within ash and tuff from a depth of 147 metres to 167 metres was intersected in CBD-01 but the ground was too broken to allow sampling. Six aquifers located within zones of volcanic ash and tuff at depths greater than 400 metres below surface were pump tested and brine samples were collected for assay. While the brines tested have high conductivity the maximum lithium concentration detected was 10 mg/L. This level is not considered by the Company to be high enough to indicate potential for economic recovery of lithium (ASX release 23 April 2018 )
Lithium clay minerals were detected by analysis of hyperspectral data from drill core scans of the core from CBD-01 (ASX release 27 June 2018 ). Assay results for selected CBD-01 core samples range from 20 ppm to 200 ppm lithium and from 10 ppm to 150 ppm boron. These levels are anomalous but not commercial (ASX release 28 August 2018 )