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Orocobre shares updated exploration results

Published by , Assistant Editor
Global Mining Review,

Australian mineral resource company Orocobre Ltd (Orocobre) has provided an update on project developments, including recent results received from the brine sampling of diamond core hole CAU18 in the northwest sector of the Cauchari joint venture (JV) property located in Jujuy Province (Argentina).

The exploration programme is being managed by JV partner Advantage Lithium Corp. (Advantage Lithium) who hold 75% of Cauchari. Orocobre owns the remaining 25% of Cauchari and 29% of Advantage Lithium's issued capital.

Managing Director & CEO, Richard Seville commented: "CAU18 in the NW Sector of Cauchari confirms the extension of brine to the northern property boundary with our Olaroz project, intersecting sandy sediments and gravel representing positive extraction characteristics in this area. The Mg/Li ratio is similar to Olaroz, which is very favourable for brine processing. With upcoming results from holes CAU17 and CAU14 the JV will update the project resource estimate, to be followed by a Preliminary Economic Assessment (PEA)."

Northwest Sector - CAU18 Drilling Results

CAU18 was drilled and cased through the upper gravel and sandy gravel units of the Archibarca alluvial fan to a depth of 130 m. CAU18 was continued as a diamond core hole from 130 m to a total depth of 359 m. Sand dominated and halite dominated units were encountered from 130 m - 260 m depth. The interval between 260 m - 359 m intersected mostly clay and silt dominated units.  Brine assays were received from nine bailed samples over a depth range from 165-320 m, returning an average of 476 mg/l Lithium and 3775 mg/l Potassium over this 155-m interval. 

According to the company, the brine mineralisation, shows a positive Mg/Li ratio of 2.5:1, and confirms the extension of elevated lithium concentrations from the northern property boundary with Orocobre (Sales de Jujuy) through to CAU15, where brine mineralisation remains open to the south. CAU18 is located 3.6 km north of CAU07 and 15 km north of CAU15. Results from CAU15 (NW Sector) and CAU11 (in the SE Sector) suggest the brine body continues south of these holes, and this area will be evaluated further following the upcoming resource estimate, providing potential for future resource expansion.

The majority of drainable porosity test results on undisturbed core samples have now been received from the GeoSystems Analysis laboratory in the US and will be used in the upcoming resource estimate. The results have confirmed the favourable drainable porosity characteristics of the sand dominated units and are further supported by the high flow rates reported recently in CAU07 and CAU11 pumping tests.


Southeast Sector – Brine Sampling Activities

Brine chemistry analyses have been received from packer sampling carried out by the company on pumping test wells CAU08, 09, 10 and 11. This discrete interval sampling using a packer and low-flow pump provides information for the resource estimate and confirms the composite brine grades obtained in holes CAU08, 09, and 10 to date from pumping tests, with results from CAU11 pending. 

To date, results have been received from the sampling in the upper parts of these holes confirming good Li grades in the range 619 to 724 mg/l.  In CAU08 results average 619 mg/l Li and 5442 mg/l K from 60-146m; in CAU09 results average 643 mg/l and 6141 mg/l K from 78-171 m and in CAU10 results average 724 mg/l Li and 6319 mg/l K from 60 - 126 m, with deeper sampling yet to be undertaken with packer equipment.

Completion of Phase 2 Drilling and Pumping Programme

Currently diamond drilling is underway on CAU14 site in the SE Sector. Brine chemistry analyses from CAU14 and CAU17 are the last results from the Phase 2 programme to be included in the upcoming resource estimate. 

Upcoming Phase 3 drill programme 

Additional deeper drilling has been planned to depths below 450 m to fully define the extent of the deeper sand unit and the base of the Cauchari salar basin. The phase 3 programme will include additional production well installations and pumping tests in the NW and SE Sectors and will follow on immediately from the Phase 2 programme.

The Phase 3 deep drilling will be supported by a new drill rig (large diameter drilling capacity to beyond 600 m) that will be mobilised to the Project by mid-April. A series of holes will be completed to define the full extent of the lower (deep) sand unit for an additional update to the resource /reserve estimate to be included in the DFS planned for completion in early 2019.

Cauchari JV Development Timeline 

The updated resource estimate, due to be released in 2Q18, will be followed by a Preliminary Economic Assessment planned for completion in June-July. Proposals have been received from internationally recognised engineering companies with lithium experience and the selection process is well advanced to allow engineering studies for the PEA to commence in mid-April 2018.

The PEA will evaluate project development options and establish the preliminary project economics, summarised in a NI 43-101 Technical Report.


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