Targets: Copper-gold porphyry intrusions and associated skarns in the Sayan-Altaids arc system
Area: ~82,506 ha, or ~825 km2
Location: Khovd Aimag, western Mongolia
Ownership: 4 tenements (Yol) owned 100% by Altan Rio & 5 tenements (Chandman) owned 100% with a 2.5% NSR
The Chandman-Yol property area is located in mountainous basin and range country in eastern Khovd Aimag, western Mongolia, about 1,050 km west of the capital Ulaanbaatar. It consists of 9 tenements, all of which are 100% owned by Altan Rio, with the 5 Chandman tenements being subject to a 2.5% NSR.
Altan Rio has secured an extensive tenement position focussed on epigenetic, porphyry copper-gold mineralisation, and stratabound skarn copper-gold mineralisation related to Cambrian-aged granitic intrusions, and gold-copper mineralised fault zones. Mineralized zones span a distance of 60+ km across the project area, representing a new large-scale copper-gold district.
Two drilling campaigns consisting of 17 diamond drill holes (5,167.7 m) were completed in 2009 and 2010. Significant gold-copper mineralisation was intersected in 3 of these recently completed drill holes (CH-09, CH-10 and CH-16). The best intersection was in the DDH CH-09 Del target skarn zone:
- 32.13 m @ 1.49 g/t gold, 0.60% copper and 8.07 g/t silver; including 10.39 m averaging 2.71 g/t gold, 0.91% copper and 12.11 g/t silver.
Further gold-copper mineralisation was intersected in DDH CH-10:
- 10.75 m @ 1 g/t gold, 0.65% copper and 4.8 g/t silver.
The geologically significant hole DDH CH-16 was aimed at the upper reaches of a deep-seated IP chargeability feature, forming part of an apparent shell around the porphyry intrusion at depth. The hole was completed to a depth of 524 m, the limit of the man-portable drill.
- A marked structural zone was crossed at 469 m, below which strong potassic alteration and sulphide stockworking became much more abundant. Assays in the 55+ m wide porphyry-style alteration zone ranged up to 0.28% copper and 1.5 g/t gold with elevated arsenic and silver values as well.
It is apparent that the drill just pierced the outer margins of one of the large high-amplitude IP features of the hypothesized “sulfide shell”.
Recently completed soil geochemical surveys carried out by Altan Rio have shown pronounced copper-gold-zinc anomalies centred on and distal to a Cambrian-age porphyry intrusive complex (called the “KY intrusion”) approximately 4 km in diameter. The KY skarn zone southeast of the porphyry intrusive is the locus of strong copper-gold-silver-zinc geochemistry. Complex fault structures located to the west and southwest of the KY skarn zone show gold-copper-molybdenum soil geochemistry.
Detailed IP and ground magnetic surveys have also been carried out since 2007. IP and Resistivity surveys show that a number of strong anomalies are present within the KY intrusion itself, most strongly developed at depth, and within structural zones marginal to the intrusion. The IP chargeability feature at depth in the KY intrusion is a large-scale concentric feature nearly 2 km in diameter and up to 1 km in vertical extent, with a high resistivity core zone – geometry typical of other large, upright, copper-gold porphyry systems.
The ground magnetic data shows a large annulus of pronounced magnetic anomalies surrounding and distal to the KY porphyry stock. The reduced to pole (RTP) magnetic data also shows several linear features, interpreted as major fault structures trending northeast-southwest and northwest-southeast across the southeastern flank of the porphyry intrusive complex.
Encouraged by the 2009-2010 results, the main higher chargeability portions of the anomalies were targeted in the 2011 field-season with a further 13 diamond drill holes (7,814.4 m). All drilling was wide-spaced, testing an area of about 4 x 3 km. The following results were achieved:
- All holes drilled intersected elevated metal values, with frequent 0.5% Cu and 0.5 g/t Au from 1 to 3 m core samples
- Highest gold grade achieved: CH-27, 1 m @ 28.02 g/t in a “sea” of low level Au and Cu
- Reconnaissance hole CH-09 returned an impressive 32.13 m @ 1.49 g/t Au and 0.6% Cu
- CH-28 silverintersections in the KY porphyry intrusion:
- 13.2 m @ 43.12 g/t, including 1 m @ 106.31 g/t and 1 m @ 118.86 g/t
- 39.6 m @ 24.57 g/t, with 2.5 m @ 128.3 g/t and 2.2 m @ 114.26 g/t
2012 Drill Results
The 2010 and 2011 exploration seasons at the Chandman-Yol project produced several new and highly promising targets from a combination of geological mapping, large geochemical survey grids and reconnaissance IP profiles. The two most advanced targets, Ovoot and Takhilt, were drilled in 2012.
Ovoot – Discovered by reconnaissance profiling, this high amplitude IP chargeability anomaly (35+ msec), the strongest anomaly identified on the Chandman Project to date, is at/near surface and of substantial size, with dimensions of 2+ km long, 1 km wide, and possibly 500 to 800 m thick. Copper staining is visible in vertical fractures at surface directly above the IP feature, which provides strong evidence of geochemical leakage from depth.
Two holes were drilled at Ovoot in 2012, 1.8 km apart, to test two concealed but coincident IP and magnetic anomalies. Both holes encountered only low-level gold and copper anomalies. Further drilling is warranted at Ovoot, though of lesser priority than Takhilt, to test areas of coincident geochemical and IP-Magnetic anomalies. The Ovoot structure is large – 2+ km long, 2+ km wide – and cannot be considered adequately tested with only two wide-spaced reconnaissance holes.
Takhilt – An outcropping copper-gold porphyry intrusion with disseminated copper oxide staining named Takhilt was discovered in 2011 by geological mapping in the northern Yol licenses of the project. Follow-up soil geochemical sampling delineated a robust copper soil anomaly about 600 m in diameter. Rock chip sampling locally assayed up to 30 g/t gold and +1% copper. Targeted IP profiles imaged moderate to strong (30+ msec) chargeability responses that extend to about 2 km along strike, and remain open to the east.
Five moderately wide spaced holes were completed at Takhilt in 2012 and several new zones of gold and copper mineralization were intersected, including a shallow intercept beginning at 16.30 m from surface of 8.05 m at 1.77 g/t gold, including 2.5 m @ 5.38 g/t gold. These zones are open down dip and along strike and warrant follow-up drilling along the entire 1.5 km extent of the Takhilt structure.
The project is fully permitted for all exploration activities and enjoys strong support from local government administrations.
The Chandman-Yol area lies within the Khyargas Nuur sub-terrane of the Pre-Cambrian to Early Paleozoic “Lake” Terrane. The structure of the area can be described as NW trending antiform structures expressed by mountain range tops. The geology at Chandman-Yol is dominated by numerous fault slices of Vend-Cambrian metasedimentary rocks (sandstone, siltstone, argillite, limestone) and volcaniclastic units. Intruded into the Vend-Cambrian sequence are numerous island arc type calc-alkalic intrusives dating to the Mid-Cambrian. A specific biotite granite phase is linked to mineralisation (Cu, Au, As, Mo, Ag, Sb, Zn, Pb) and shows broad zones of intense quartz-sericite-pyrite (+chalcopyrite) alteration, thought to represent a high-level near-typical Cu-Au porphyry system with distal iron-rich skarns.