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| | MAIN PROJECTS
 Richard H. Sillitoe Report Click here to view (PDF, 175 kb)
 Chisna Webslides Click here to view (PDF, 326 kb) | | |  Project Summary The Chisna Project targets copper-gold-silver porphyry-style mineralization in late Paleozoic rocks intruded by magmas of the Cretaceous Porphyry Belt; which also hosts the 4.1B tonne Pebble Gold-Copper Porphyry Deposit 600 km to the southwest and the 350M tonne Orange Hill Copper-Molybdenum Porphyry Deposit to the southeast (Figure 1). Results to date show the potential for a major new porphyry discovery by International Tower Hill Mines Ltd ("ITH"). Figure 1. Location of known copper porphyry deposits (Pebble, Orange Hill) and the Chisna project within the Cretaceous Porphyry Belt. Location The target area is a belt 65km long and 15km wide extending from Slate Creek 30km northeast of Paxson to Slana on the Tok Cutoff Highway. Access is via aircraft, or winter roads from the Tok Highway near Slana (Figure 2). Ownership ITH controls 100% of the of 180 State of Alaska claims initially staked in June 2006. This extensive land package covers 294m² of land. The contiguous claim blocks are referred to as Chisna Block, Slana, Chisna SE (Figure 2). Figure 2. ITH's Chisna claims showing highways, winter access roads, and the distribution of copper and gold prospects in red. Property Background The Chisna region has produced approximately 180,000 ounces of gold from historical placer deposits in streams draining the target areas. A large number of gold and copper occurrences are known in the area (Figure 2). However, little modern exploration has been done and the lode potential is considered high. Partial historic data held by ITH indicates that some work was done on the POW prospect in the Chisna block during the 1980's and some work was done in the Chisna SE block during the 1990's. ITH began the initial phase of exploration in the northeastern Chisna Block in 2006, completing regional silt sampling, mapping, and prospecting which detected several strong copper, gold, and silver anomalies. On the basis of these early indications a number of additional claims were staked in November 2006 extending the Chisna Block to the southeast and adding the Slana and Chisna SE blocks. Regional Geology The Chisna target area lies within the Wrangellia accretionary terrane south of the Denali Fault. In this area the Wrangellia Terrane is composed of 340Ma volcanic and sedimentary rocks deposited in an island arc setting. These rocks were intruded by magmas of several ages including 285Ma, 167Ma and 104Ma. It is possible that mineralization could be associated with either the original volcanic events or any of the later intrusive events. However, the main target mineralization is associated with 104-90Ma magmatism which produced the Orange Hill Porphyry Deposit (Figure 1). 2007 Exploration Summary In 2007 surface exploration was conducted in all three of the separate claim blocks. Airborne geophysical surveys were carried out over the Chisna and Chisna SE blocks. Chisna SE Porphyry Copper-Gold Target: Ongoing geological mapping and sampling at Chisna SE has successfully identified several areas of strong, high level porphyry-type alteration indicating the presence of an alkaline type system. The alteration is cut by a series of copper and gold mineralized fractures thought to represent leakage from a significant mineral system at depth. The average assay of all rock samples (246) collected over a 7 square kilometer area in and around the alteration cap was 0.37 g/t gold, 1.4 g/t silver and 0.08% copper (Table 1; Figure 3). At Chisna SE gold and copper mineralization occurs in many different styles -- gold in gossanous faults, gold associated with quartz-pyrite- chalcopyrite veins, trace gold in chalcopyrite breccias (Figure 4), trace gold in stockwork or sheeted veins of quartz-pyrite-chalcopyrite-molybdenite. In addition, there are barren magnetic veins and anomalous bismuth in pyritic stockwork veins. The results of the geochemical sampling program defined a target covering a minimum 3km2 area and still open to the south, east, and northeast. The zone of alteration and highly mineralized fractures is coincident with a strong magnetic feature revealed in the airborne geophysics. The highly anomalous gold and copper values from the 2007 soil survey occur in conjunction with this magnetic feature strongly supporting the potential for a significant porphyry discovery at Chisna SE. ITH is very excited to have this early exploration property. Table 1. Chisna SE target surface sample data.
Figure 3. Gold in soils superimposed on total field magnetic data from the Chisna SE target. Note that the target is open in all directions. Figure 4. Sodic-calcic altered intrusive breccia with chalcopyrite infill and malachite staining from Chisna SE; 0.9% Cu, 6.8g/t Ag, 0.15g/t Au, 3% Na, 0.5% K. Chisna Block Exploration The airborne resistivity and magnetic survey delineated two major magnetic features in the Chisna Block which have been named the Miller Gulch Gabbro and the Powell Creek Diorite (Figure 5). Figure 5. Aeromagnetic map of the Miller Gulch and POW target areas. Red triangles indicate the locations of rock samples with >700ppm copper. Brown circles represent soil samples with >250ppm copper. The topographic contour interval is 20 meters. Miller Creek Gabbro The 2006 silt survey has delineated anomalous Ni in the vicinity of the Miller Gulch Gabbro and platinum minerals have been historically recovered from Miller Gulch placer deposits. Surface mapping in 2007 has shown that the Miller Gulch Gabbro is really a mafic intrusive complex with many distinct phases. Samples were collected for a petrographic and geochemical study on these rocks to assess the potential to find nickel or platinum associated with this complex. POW Target The Powell Creek Diorite is non-magnetic. However, it has produced an alteration halo of magnetite in the surrounding volcanic rocks. The alteration is zoned from magnetite close to the intrusive to maghemite and hematite farther away. Where sediments are present calc-silicate alteration is often developed. Beyond the magnetic alteration there is a broad zone of pyritic alteration (Figure 6). Copper mineralization develops in association with the hematite alteration and veining but there is no gold. However, at the POW Prospect, which is located even farther away from the central intrusive, gold and copper mineralization is developed (Figures 5; 6). At POW a strongly silicified structural zone over one-half kilometer in length is delineated. The rock samples (39) collected in this zone average 1.1 g/t gold, 7.9 g/t silver and 0.3% copper (Table 2, Figure 7). A broad zone of gold mineralization in soils coincides with the location of a rhyodacite pyroclastic unit suggesting that the unit may be selectively mineralized. More detailed rock sampling is planned for 2008 to define the target. Figure 6. POW Prospect -- view looking east. Red area in the foreground coincides with the broad gold anomaly in soils. Rusty areas on ridge beyond reflect narrow mineralized structures and broad pyritic alteration in volcanics. Table 2. POW target surface sample data.
Figure 7. Historic soil survey and geology over the POW prospect. Exploration 2008 Ongoing negotiations with surrounding landholders to secure an Exploration and Mineral Lease Agreement will hopefully expand the Chisna SE property to the northeast and south. The SE target could develop into a significant new porphyry discovery and will be a major focus of the 2008 Chisna exploration program which will include ground geophysics and surface mapping with the objective of defining targets for drill testing in August and September. In the Chisna Block new results at POW have outlined a drill target for 2008 which has large tonnage potential. This highlights the importance of continuing exploration in other parts of the block which have not yet been tested. The 2008 scope of work in the Chisna Block will be dependant on how the program in Chisna SE develops. | | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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