Toro Geology
Southern White Gold District/Dawson Range Mineral Belt
The 2008 Underworld “White Gold” discovery challenged the historic mineral deposit models in the northern Dawson Range and Dawson Gold Districts. The “gold in soil” anomalies and mineral assemblages did not match with “epithermal models”, “porphyry models” or “intrusion related gold.” These newly discovered deposits did, however, demonstrate previously unknown affinities to regional N to NE and E-W trending structures and associated Au/As and Au/Sb soil anomalies.
Historic work on the Toro Project has identified numerous gold and base metal anomalies. These anomalies were always interpreted with respect to historic models which targeted copper-molybdenum-gold porphyry deposits occurring along a northwest-trending linear belt that forms the Dawson Range mineral belt. Dawson Gold is working to integrate the historic geological knowledge with these new vectors to define clear targets in exploring the Toro project.
Regional Geology
The region is dominated by metamorphic rocks of the Yukon Tanana Terrane which are intruded by batholiths of Early Jurassic and mid-Cretaceous age. Like most of the porphyry occurrences of the Dawson Range, the Tad porphyry is located immediately southwest of the Big Creek Fault—a prominent structural feature that appears to control the distribution of mineralization in the Dawson Range. A second, north trending fault is thought to exist beneath the Hayes Creek valley. At least four small northeast-trending faults have been recognized cutting the Tad porphyry. Placer gold has been mined periodically from Hayes Creek and its tributaries.
Property Geology and Mineralization
The Tad property (YGS minfile 31 and 32) is centred on a felsic porphyry stock which is approximately 3 by 2 km and intrudes coarse-grained, pink quartz monzonite that hosts pendants of Yukon-Tanana Terrane metamorphic rocks.
Rock outcrops have been oxidized to depths of up to 80 m. Strong manganese staining and limonite is present with higher gold grades. A narrow supergene zone sometimes lies above the hypogene zone.
The best target for gold mineralization is the oxidized breccias, structures and alteration zones in the quartz monzonite porphyry. The underlying hypogene zone may contain gold bearing quartz arsenopyrite veins. Sulphide mineralization consist of up to 10% pyrite disseminated in the granite porphyry and in alteration zones. Narrow quartz sulphide veins in breccias and structures containing sphalerite, galena and aresonpyrite bearing quartz veins are present along shear zones.
Three primary mineralization types are recognized:
1. Sericite/Limonite Breccia
2. Shear hosted and Mesothermal Quartz Veins
3. Porphyry Cu-Mo
A radiometric survey over the Tad property indicates that it has a large area with a low Th/K ratio. This signature is similar to, although larger and slightly less intense than, the Casino copper-molybdenum-gold deposit.
Compilation work following the Noranda work produced several coincidental anomalies located upslope of earlier drill holes. New plots of the magentics delineate linear lows that may outline mineralized structures responsible for the high geochemical values.
This work outlined a 750 m soil anomaly (Au-As-Pb-Zn) which is coincidental with several linear magnetic lows and moderate to high chargeability responses. This area was originally drilled in six holes targeting the main Pb-Zn anomaly. Three holes contained gold values greater than 1 gpt. Two other holes intersected breccia with weak gold values. Additional drilling is proposed to test the upslope portion of the main soil s anomaly.
One peak area of Au-As values in the southeast portion of the anomaly was drill tested. Two holes intersected anomalous gold values in the oxide zone in a limonitic and manganese stained breccia to the northeast and downslope of the core of the anomaly. Additional drilling is proposed to test this area.
Diamond drill core (NQ-size) of the Tad porphyry from the oxide zone. Light-coloured phenocrysts are quartz and alkali feldspar; dark specks are altered plagioclase.