Gold explorer Tesoro Resources (ASX: TSO) has confirmed that assays received for four drill holes at the high-grade Ternera prospect within its El Zorro gold project in Chile have further extended the mineralised zone.
The first two holes were designed as step-outs to test mineralisation from drill holes in August which assayed 231m at 0.83 grams per tonne gold including 25m at 3.36g/t and demonstrated the zone’s continuity of grade and width.
The step-outs also tested the northern part of the Ternera GAIP (gradient array induced polarisation) chargeability anomaly identified during geophysical surveying in August, extending the mineralised zone by approximately 140m.
The remaining two holes were infills designed to provide additional information for modelling and resource estimation.
They successfully delineated shallow mineralisation, with further drilling required to test down dip and along strike.
All holes intersected multiple gold zones and best results were 111.5m at 1.25g/t gold from 124m, including 58m at 2.04g/t from 124m, 27.5m at 3.57g/t from 154m, 13m at 5.32g/t from 159m and 4.5m at 3.07g/t from 231m.
Other results were 19m at 0.46g/t gold from 91m from 91m, including 4m at 1.48g/t from 104m; and 1m at 8.75g/t from 280m.
Ternera is the first of five targets identified at El Zorro and the assays are expected to add to the large-scale potential of the project.
Tesoro managing director Zeff Reeves said holes drilled to date have delivered quality gold results for the company.
“The Ternera deposit has been drilled over a strike length of more than 750m, a width of up to 600m and is open at depth,” he said.
“We are yet to find the edges of the mineralisation and every hole adds additional scale [which] indicates to us that we have a significant discovery at El Zorro.”
He said a wide, high-grade zone emerging to the south was continuous for over 300m and up to 100m wide and open in all directions, with new extensions providing additional infill drill targets.
Tesoro is operating two diamond drill rigs around the clock at the Ternera deposit, with drilling expected to continue through December as the mineralised footprint expands.
Screen fire assaying
A program of screen fire assaying has begun at Ternera to assess the grade effect of coarse or nuggety gold within the deposit.
The technique involves screening a large, pulverised sample (typically weighing 1 kilogram) at 75 microns.
The entire oversize (including the disposable screen) is fire assayed as this contains the coarse gold and a duplicate determination is made on the ‘minus’ 75-micron fraction.
A calculation is then made to determine the total weight of gold in the sample.
Tesoro said the procedure would be equivalent to assaying a large sample to extinction and averaging the results.
A surface mapping and detailed trench sampling campaign has kicked-off at the Toro Gordo prospect, also within El Zorro.
The campaign will aim to further define surface gold mineralisation associated with extensive quartz veining and alteration delineated in May.
It will take four weeks to complete, with assay results from sampling expected in early 2021.