Gold Road Resources (ASX:GOR) has announced the confirmation of a higher grade southerly plunging core to the Gruyere deposit. The new intercepts, which include 87.57m at 1.66g/t Au and 85m at 1.53g/t Au are 30-50% higher than the overal Gruyere resource grade and point to the potential for a large sub-level underground operation below the proposed open pit.
Recently completed deep diamond hole and wedge confirms:
- Consistent higher grade mineralisation across the mineralised width of the porphyry
- Southerly plunge to higher grade mineralisation
- Continuity of internal high grade zone with visible gold in numerous locations
- Internal high‐grade trend >1.5 g/t identified in previous drilling
Gold Road Resources Limited (Gold Road or the Company) is pleased to announce the results of a deep diamond drill hole and up‐dip wedge which successfully tested the extension of the southerly plunging internal high‐grade zone, confirming the interpreted trend. The high‐grade zone in this sense refers to a coherent zone of mineralisation approximately 25 to 30% higher grade than the Gruyere Resource average grade. The parent hole, 16GY0330, intersected 87.57 metres at 1.66 g/t Au from 736.82 metres within a mineralised porphyry intersection of 172.39 metres at 1.27 g/t Au from 652 metres. The wedge, 16GY0330‐W1, drilled up‐dip of the parent hole, intersected 85 metres at 1.53 g/t Au from 699 metres within a mineralised porphyry intersection of 146 metres at 1.38 g/t Au from 638 metres (Figure 1).
The results confirm the southerly plunge of the higher grade mineralisation within the Gruyere Deposit. Holes 16GY0330 and 16GY0330‐W1 intersect the deposit at a similar vertical depth to a previous hole 15GY0107 (123 metres at 1.79 g/t Au from 659 metres (1) ) and have extended the strike of the high‐grade zone by 175 metres to the south. Grade and width is consistent with expectation of this coherent high‐grade shoot which is internal to the main Gruyere Porphyry.
A Conceptual Mining Study was completed in 2015 to assess the potential for underground development of the Gruyere Deposit assuming bulk mining methods. This early stage analysis indicated that the grades and widths observed in this drilling, along with higher grade mineralisation intersected previously, have the potential to support large‐scale, sub‐level cave, mining operations. A high level underground review will be undertaken during the December 2016 quarter to determine if further drilling is warranted to infill and extend the identified higher grade shoot to an Inferred Resource level of detail. If a compelling case is identified, the Company will likely commence the necessary diamond drilling programme during the 2017 calendar year.
Gold Road Executive Director – Exploration & Growth Justin Osborne said: “Hole 16GY0330 and the accompanying wedge, 16GY0330‐W1, successfully confirmed our interpretation of a high‐grade zone at depth. We are excited that our staged drilling programme has again confirmed that there is the real potential to identify a large scale underground Resource which we will be assessing during the remainder of 2016. If we embark on further drilling in 2017, the target would be a resource capable of supporting a bulk underground mine which could significantly add to the profitability and life of the already robust Gruyre Operation in excess of the current 12 years.”
(1) Refer ASX announcement dated 24 June 2015
The mineralisation across the mineralised width of the porphyry in both 16GY0330 and 16GY0330‐W1 returned intersections greater than 200 gram x metre gold accumulation. A coherent high‐grade zone (high‐grade in this sense refers to coherent gold mineralisation significantly (>25%) higher grade than the average Gruyere Resource grade of 1.30 g/t Au) internal to the porphyry is also present in both 16GY0330 and 16GY0330‐W1 (Figures 1 and 2), consistent with previous drilling in this part of the Deposit, with intersections as follows:
- 16GY0330: within a mineralised porphyry intersection of 172.39 metres at 1.27 g/t Au from 652 metres, the high‐grade zone totalled 87.57 metres at 1.66 g/t Au from 736.82 metres and included 61.08 metres at 1.87 g/t Au from 736.82 metres.
- 16GY0330‐W1: within a mineralised porphyry intersection of 146 metres at 1.38 g/t Au from 638 metres, the high‐grade zone totalled 85 metres at 1.53 g/t Au from 699 metres and included 60.70 metres at 1.85 g/t Au from 723.30 metres.
Higher grade gold mineralisation at Gruyere is typically hosted within strongly albite‐altered porphyry with accompanying higher levels of pyrrhotite and arsenopyrite. These strongly altered zones also host a greater density of quartz and chlorite veining. The porphyry intersected in both 16GY0330 and 16GY0330‐W1 displays increased proportions of strongly altered and veined porphyry than is generally observed in the upper zones of the Gruyere Deposit. Several occurrences of visible gold were also observed through the highest grade sections in both holes. This recent drilling, in combination with the 15GY0107 intersection, suggests that the character of the Gruyere Deposit is changing, with increasing alteration, veining intensity and associated grade improvement at depth.
Review of existing drill holes in the vicinity of 16GY0330 and 16GY0330‐W1 identified the same consistent high‐ grade zone internal to the porphyry. These existing intersections have been reported previously (2) and are illustrated in Table 1 and Figure 3 below. The high‐grade zone mineralisation style appears to be very continuous as a coherent shoot within the overall porphyry body, with a distinct southerly plunge confirmed (Figure 3). The dimensions of this main shoot are approximately 400 metres in strike, 500 metres dip extent (which remains open), at an average width of 80 metres.
(2) Refer ASX announcement dated 24 June 2015
Gold Road will conduct an assessment of the viability of underground mining at Gruyere focussing on longitudinal sub‐level caving as the preferred option highlighted by previous conceptual studies. A high level review of the new mineralisation identified in drill holes 16GY0330 and 16GY0330‐W1, and the evolving interpretation of a coherent high‐grade zone, will be the focus of underground assessments during the December 2016 Quarter. If the study supports the previous Conceptual Study, indicating underground mining, it is possible a decision will then be made by the Company on the quantity and timing of additional drilling necessary to define an appropriate Mineral Resource to support a more detailed Scoping Study on underground options.
An additional drilling programme would likely comprise a framework of deep diamond drill holes and accompanying wedges to define the main high‐grade zone to an inferred level of confidence. A target grade would likely be in excess of 1.5 g/t Au. If the initial 2016 assessment proves favourable, then drilling to Inferred Resource would likely to be completed in 2017.