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Alto Metals defines 6km gold-arsenic anomaly at Sandstone

Updated: Mar 25


Alto Metals says it is rediscovering an entire goldfield at Sandstone. Credit: File

Alto Metals has defined a 6km gold-arsenic anomaly at its Sandstone gold project in Western Australia above old workings that previously threw up drill results including 15m at 9.1g/t gold from 82m, including 3m going 32.1g/t gold.


The company says the mineralisation remains open along strike and down plunge at its significant north-trending and largely-unexplored target. The revelation comes after management interpreted results from its recent fine-fraction soil geochemical sampling program, with low-level gold and multi-element analysis combined with structural assessment of high-resolution aeromagnetic data and reviews of historic local exploration data.


The program involved the collection of 1678 samples at 40m intervals on east-west lines 400m apart and produced an anomaly that perfectly straddles the north-south trending axis of the Sandstone syncline – a trough-shaped geological fold structure. It comprises a 2.5km-long anomalous zone where values exceed 5 parts per billion gold, fully-contained within a 6km-long anomaly where values exceed 10ppb arsenic.


Our low-cost regional soils program has identified what appears to be a very large, structurally controlled gold target extending over six kilometres at Sandstone North. The gold anomaly is coherent with elevated levels of arsenic and lead – key gold pathfinder elements for structurally hosted gold mineralisation – that have also been identified over the six kilometres of strike. Alto Metals managing director Matthew Bowles

Bowles said the style of gold mineralisation at the project is different to other parts of the Sandstone greenstone belt. He said the mineralisation hosted within sulphidic quartz veins in sediments is similar to Gold Fields’ high-grade Waroonga deposit at its Agnew mine near the WA town of Leinster.


The company has already started preparing for an initial air-core (AC) drilling campaign of about 5000m for early next quarter in a bid to prove up a “significant, structurally-hosted gold prospect”.


Arsenic and gold are commonly associated in some styles of gold mineralisation – and in this case, the association is classically complementary. Arsenic is usually the more mobile element and spreads further from the source and is often a useful geochemical pathfinder element for gold.


Management says its soil anomaly confirms previous third-party lag sampling results and geological mapping. It notes that gold coincides not only with arsenic, but also elevated levels of copper and lead and that the suite are typical pathfinder elements associated with orogenic gold mineralisation.


While the area along the anomaly is relatively untested, high-grade gold mineralisation has been intersected in previous drilling, mostly by Western Mining Company (WMC). It was confined to testing peak values in a small number of gold-in-lag soil anomalies directly beneath the main historical workings, which are within a sedimentary unit close to a contact with ultramafic rocks and limited to a strike length of 300m within the overall 6km anomalous zone.


Elsewhere within the 6km strike length, little drilling has been carried out other than that directed to test the peaks of a small number of specific gold-in-lag targets.


Alto’s 100 per cent-owned Sandstone gold project is situated in WA’s Gascoyne-Murchison region, about 160km east of the town of Mt. Magnet. The company’s Sandstone North target area lies about 6km north of the town of Sandstone and is a priority area outside the company’s principal deposit – the Alpha Domain, which hosts 832,000-gold-ounce pit-constrained mineral resource.


The latest geochemistry highlights the under-explored potential of the Sandstone project, which encloses an area of more than 740 square kilometres at the historically-productive, but still vastly underexplored Sandstone greenstone belt.


Alto says it plans to test all of the 6km-long anomalous zone with broad-spaced reconnaissance drilling and will trial the “detectOre” field portable geochemical testing system that provides low-level gold assays.


With all of this going on, Alto still intends to stay focused on the development of its Alpha Domain resource. But it will also continue to evaluate its multiple, advanced prospects, with a view to establishing a stand-alone operation at is Sandstone gold project.


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