Metminco Limited (ASX:MNC) will undertake a pre-drilling program at Tesorito gold target in Colombia after a geological review and re-interpretation of data confirmed the prospect’s appeal.
A field program including extending the soil geochemistry grid, re-logging drill core and a ground magnetics survey will be undertaken to better define target zones.
These programs will allow the company to generate a 3D geologic model which will provide valuable information to design a drill program.
Review of targets
The re-assessment of Tesorito, which is within the company’s Quinchia gold portfolio, stemmed from a geological/target review commissioned by the new Board of Metminco.
Tesorito’s re-assessment was led by Metminco’s consulting geologist Nick Winer, who played a significant role in the discovery of the Nuevo Chaquiro copper-gold porphyry deposit 50 kilometres to the north.
As well as confirming the prospect’s appeal, Winer identified a program of work to advance the target.
Seven previous diamond holes intersected significant widths of gold mineralisation within a multi-phase porphyritic intrusive complex.
Hole TS-DH-02 returned 384 metres at 1.01 g/t gold from 16 metres to the end-of-hole, including 32.5 metres at 1.34 g/t from 48.8 metres and 156.6 metres at 1.28 g/t from 88.3 metres.
TS-DH-07 returned 64 metres at 1.67 g/t from 144 metres within 253.1 metres at 1.01 g/t from 2.9 metres.
Metminco’s managing director Jason Stirbinskis said, “In addition to the impressive drill intercepts, the results in holes 07 and 02 are geologically significant and a major catalyst for the re-assessment.
“Hole TS-DH-07 was the best result at Tesorito and, most interestingly was drilled oblique to all previous holes which has prompted a re-assessment of structures influencing the distribution of mineralisation.
“Hole TS-DH-02 ended in a mineralised zone that included 2.6% copper over 0.7 metres at 390.8 metres implying there could be a copper-rich zone at depth.
“Metminco management is of the belief that the target remains with considerable untested potential for defining continuity of higher-grade zones such as that intersected in TSDH-007 and for evaluation of the copper potential.”
Close to Chuscal
Tesorito is a sub-outcropping mineralised porphyry discovery about 1-kilometre north of Chuscal where the company is drilling.
It is also only several hundred metres from the proposed processing facility described in the Miraflores feasibility study.
Location of major gold targets in the Quinchia gold portfolio.
Previous drill programs at Tesorito assumed that mineralisation was primarily controlled by a regional N-S trending bounding structure.
This interpretation remains valid at a macro level, however detailed assessment of rock chip geochemistry data suggests the gold target and porphyry pulses lie in NW-trending, low-pressure zones within the N-S trending zone.
All holes except TS-DH-07 were drilled sub-parallel to the NW trending target zones.
The NW trend is consistent with known regional controls on mineralisation in other deposits in the region such as Nuevo Chaquiro.
Metminco’s soil sampling geochemistry will close the existing grid spacing from 200 x 50 metres to 100 x 50 metres and extend the grid to better define the target zones.
Drill core will be re-logged with particular attention to rock composition (lithology) and texture using lithogeochemistry and rock thin sections.
The reassessment study identified variations in geochemistry and texture markers that were not apparent in the original core logging exercise and is expected to lead to better targeting.
Similarly, the ground magnetics survey will provide greater resolution than the previous regional programs and is designed to enable 3D modelling which is expected to provide useful targeting.
Stirbinskis added, “Completing the program in the next few months will provide the opportunity to add a validation drilling program to the back-end of the Chuscal drill program.
“The Tesorito target has the potential to provide additional resources to a district-scale mining operation.”