Rockhaven upgrades, grows Klaza resource

Rockhaven Resources Ltd. June 21 published an updated mineral resource estimate for the high-grade Western BRX, Central BRX, Central Klaza, and Western Klaza zones at its Klaza project in southern Yukon with 686,000 ounces of gold in the indicated category and 507,000 oz in the inferred category.

The updated resource incorporates results from roughly 13,300 meters of in-fill and expansion drilling completed since the previous estimate in 2015. Bulk tonnage, low-grade mineralization in the eastern zones on the property require additional sampling, drilling and modeling and is not included in the updated resource estimate.

Klaza now hosts 4.5 million metric tons of indicated resource averaging 4.8 grams per metric ton (686,000 ounces) gold and 98 g/t (14.07 million oz) silver, or 907,000 oz gold-equivalent. Additionally, the project hosts 5.7 million metric tons of inferred resource averaging 2.8 g/t (507,000 oz) gold and 76 g/t (13.9 million oz) silver, or 725,000 gold-equivalent oz.

The tonnage and grades of the near surface, open-pit mineable resource at Klaza increased significantly compared to previous estimates. This pit-constrained portion of the indicated resource now sits at 2.4 million metric tons averaging 5.3 g/t (414,000 oz) gold and 90 g/t (7.1 million oz) silver, for 529,000 oz gold-equivalent. The pit-constrained portion of the inferred resource is at 1.8 million metric tons averaging 2.6 g/t (147,000 oz) gold and 43 g/t (2.4 million oz) silver.

The resource also hosts significant zinc and lead byproducts.

"The Klaza project hosts high-grade gold and silver resources that are near surface, road accessible and located within one of the safest mining jurisdictions in the world," said Rockhaven Resources president and CEO Matt Turner. "(T)he conversion of high-grade resources from underground to open-pittable should have major economic benefits for the project."

The Klaza project hosts a large hydrothermal system that is concentrated within a 4,000- by 3,000-meter structural corridor. Current resource areas have only been systematically explored to about 275 meters below surface, but Rockhaven drilling has tapped well mineralized intersections as deep as 450 meters and models suggest the mineralization could extend to 1,000 meters. Eleven known mineralized zones have been identified within the corridor and all are open for expansion along strike and to depth.

A 2016 preliminary economic assessment for Klaza envisions using a combination of open-pit and underground techniques to mine the 9.42 million metric tons of inferred resource grading 4.48 g/t (1.4 million oz) gold, 89 g/t (27 million oz) silver, 0.75 percent (155.4 million pounds) lead and 0.95 percent (197.8 million lb) zinc.

The 1,500-metric-ton-per-day process plant proposed in the PEA is projected to produce 630,000 oz gold, 11.4 million oz silver, 52.5 million lb zinc and 51.23 million lb lead over an initial 14-year mine life.

Since the completion of the PEA, Rockhaven has focused on further metallurgical work, resource expansion and infill drilling to enhance the economics of mining Klaza.

The PEA identified several opportunities to improve future economics, including: exploring alternate processing methods that could lower overall costs and allow lower-grade mineralization excluded from the PEA to be effectively processed; better definition of near surface mineralization to maximize the open-pit potential of the resource; and infill drilling to confirm grade continuity within the deposit and increase the grade of the known high-grade veins.

Since the PEA, Rockhaven completed 13,291 meters of infill and expansion diamond drilling, within and near to the 2015 Mineral Resources, which demonstrated the continuity of high-grade structures and identified much higher-grade areas within the known vein zones.

The eastern portion of the Klaza vein system (Eastern Zones) comprises multiple, sub-parallel veins and veinlets, and includes the Eastern Klaza, Eastern BRX, Pika, Stroshein, and part of the AEX zones. All of these zones are open to the east, towards the mostly untested Kelly Porphyry. Previously, these zones were assumed to be similar to the discreet high-grade vein zones to the west (Western and Central portions of the BRX and Klaza) and were sampled, targeted and modeled using this assumption. The recent drilling and metallurgical test work have demonstrated that the mineralization is structurally, mineralogically and metallurgically different from the western zones. This area has bulk tonnage potential and requires additional sampling, drilling and modelling before a Mineral Resource estimate can be finalized.

Metallurgical testing completed last year demonstrates that dense media separation is effective in the Central Klaza, Western BRX, and Eastern zones. This test work also showed that the Eastern zones responded well to direct cyanide leaching. The new processing techniques identified by the test work allow for lower cut-off grades to be applied to the current Mineral Resource estimates. The application of pre-concentration should allow for less selective, lower cost mining methods in both underground and open pit workings in future economic studies.

The updated mineral resource and recent metallurgical work have highlighted multiple priority targets for further resource expansion and definition. These include: continue upgrading inferred resources to the higher confidence indicated category; additional drilling to expand and upgrade resources in the Eastern zones; exploration drilling of near-surface mineralized zones that parallel the resource, including high-grade structures identified last year; expansion of inferred resources below the western and central portions of the BRX and Klaza zones; and expansion of the area of fracture-style mineralization surrounding the known Eastern Zones.

–SHANE LASLEY