DRILLING COMPLETED AT DUKE ISLAND, ALASKA
Summary – Best results from the program included .294% copper and .075% nickel over 4.9m and .148% copper and .039% nickel over 13.4 m over two separate intervals in hole DK10-08. Despite drilling to depths of up to 468 m, the targeted basal contact of the mineralized intrusion was not encountered. The drilling determined that zoning within the ultramafic complex is more complex than anticipated and that what had been thought to be the basal contact, as interpreted through several geophysical techniques, was in fact rafts of partially assimilated sedimentary rocks. The combination of high sulphide content and graphite related to the sediments produced strong electromagnetic conductors.
The Company believes that Cu-Ni-PGE enriched magmatic sulphide accumulations along basal contacts or within a feeder zone remains a unique and prospective exploration target at Duke Island, due to the intrusion’s high sulphide content, the magmatic or net-textured nature of the sulphide mineralization and nickel depletion of some of the intrusion’s silicate mineral phases. However, the 2010 drilling has demonstrated that such a target, if it exists, is geophysically masked by overlying zones of conductive pyrrhotite-graphite mineralization. Further study is required to determine if other exploration tools might be applied to direct future drill programs. The Company will evaluate the drill results and its revised interpretation of its geological model before determining its future course of action with regard to the Property.
Project Details – Cu-Ni-PGE sulphide mineralization within the Duke Island Alaska-type zoned ultramafic intrusion in the Alexander Platinum Belt was discovered by Quaterra in 2001. The occurrence is unique due to the high percentage of disseminated and net-textured to massive sulfide mineralization that occurs within certain phases of the ultramafic intrusions. While pyrrhotite is the dominant sulfide, chalcopyrite and minor pentlandite are observed to occur preferentially in a marginal clinopyroxenite phase of the intrusion. Outcrop samples have returned values from less than 10 ppm Cu to 2.8% Cu, from less than 10 ppm Ni to 0.25% Ni and from less than 5 ppb to over 1 ppm PGE from the South Rim of the Marquis prospect. Five of six historical core holes drilled at the South Rim of the Marquis prospect intercepted from 6 m to 90 m of semi-massive to massive sulfide containing anomalous values for Cu (10 to 12,500 ppm), Ni (27 to 4,694 ppm), Pt ((less than)5 to 680 ppb), and Pd ((less than)5 to 548 ppb) and established a north dip to the upper contact of sulfide mineralization.
The 2010 drill holes targeted massive to semi-massive Cu-Ni-PGE sulphide mineralization along the basal contact or within the feeder of the Marquis Zone, where the highest grades of sulphide mineralization were inferred to occur. The drill targets were defined by interpretations based on geological mapping, the results of historical drilling and three-dimensional modeling of a variety of geophysical surveys including magnetics, electromagnetics, induced polarization, magnetotellurics and gravity. The historical drilling did not extend to the depths required to test these targets.
DK10-08, the first hole of the program, was drilled vertically to test the South Rim anomaly at depth. The hole collared in pyroxenite and transitioned into a gabbro at 204 m. The hole remained in variably serpentinized gabbro until a final depth of 467 m. Up to several percent disseminated to net textured pyrrhotite with trace to locally one to three percent chalcopyrite occurred throughout the pyroxenite interval. The best intervals of copper mineralization were from 124.4 m to 137.8 m which returned 1,476 ppm copper and 392 ppm nickel over 13.4 m and from 170.4 m to 175.3 m which returned 2,937 ppm copper and 751 ppm nickel over 4.9m. From 1% to 15% pyrrhotite was encountered in the gabbro from 302 m to 350 m. Assimilated sedimentary country rock with local graphite also occurred within this interval. The pyrrhotite mineralization with graphite could be the cause of the conductor that had been interpreted as possible massive sulphides along the basal contact of the South Rim of the Marquis zone.
Hole DK10-09, drilled at an angle of – 80 degrees and DK10-10, drilled at an angle of – 45 degrees were collared from the same site to test the strong EM conductor identified under cover at the North Rim of the Marquis zone. Both holes collared in gabbro and remained in gabbro until lengths of 380 m and 153 m respectively. Hole DK10-09 intersected from 1% to 15% net textured to semi-massive pyrrhotite and locally from trace to 10% graphite associated with assimilated sedimentary rock from 64 to 124 m. Hole DK10-10 intersected similar pyrrhotite with graphite and assimilated sediments from 10 to 108 m. Trace to 1% chalcopyrite was observed in both holes, but no significant copper or nickel assays were returned from either hole. The strong EM conductor under the North Rim of the Marquis zone is likely explained by the presence of pyrrhotite and graphite related to sedimentary rocks within the gabbro.
Holes DK10-11 and DK10-12 were drilled to test EM conductors and prospective stratigraphy at other areas of the Marquis zone. DK10-11 intersected the prospective pyroxenite horizon from the collar to 150m and then remained in gabbro until a final depth of 387 m. DK10-12 intersected gabbro from the collar to a final length of 225 m. While both holes intersected significant amounts of pyrrhotite in the gabbro, no significant copper or nickel mineralization was returned from either hole.
About Copper Ridge Explorations Inc.
Copper Ridge is committed to exploring in areas of high grade mineral potential with focus on a copper/nickel/platinum project on Duke Island in
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SOURCE Copper Ridge Explorations Inc.