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Oct 27, 2009
Initital Drill Results Confirm Gold and Porphyry Copper-Gold Mineralization Potential at American Tunnels
As noted in an August 6, 2009, release, the initial test of 1,200 to 1,500 meters of drilling at American Tunnels was designed to test both gold mineralization and an underlying porphyry copper-gold target. The drilling is focused on an erosional window through ultra-mafic cap rocks, where mineralized intrusives are exposed and where artisanal miners are carrying out near-surface, small-scale gold and copper mining. Holes one to five were drilled within this window which is on the northern limits and beyond the chargeability anomaly, as shown on the location map accompanying this release and available on Mindoro's website. Although the best mineralization is anticipated to be associated with sulphides, and therefore the chargeability anomaly to the immediate south (see accompanying map), initial drilling is focused on the area of exposed intrusives instead. Objectives are to confirm the mineralization models and their significance as a prelude to a more intensive drill program along the rest of six kilometer mineralized trend.
Intrusive-Related Gold Mineralization
Hole three intersected 15 meters of 2.32 grams per tonne (g/t) gold from 9.30 to 24.30 meters. As reported by the company on June 2, 2009, sampling by Mindoro one hundred forty meters to the north in an artisanal underground small-scale mine (Roque Shaft) gave 26 meters (aggregate length) of 1.94 g/t gold from continuous rock chip sampling. Mineralization in both cases is related to dyke and vein swarms and is interpreted as intrusive-related gold mineralization. Hole 4 scissored in the opposite direction hit three unrecorded historical artisanal mine stopes, and therefore did not encounter significant gold grades. Reliable information is not available from the numerous other gold workings in the area due to their inaccessibility.
The drill and underground sample results, combined with the extensive distribution of shallow artisanal gold workings, indicate the area has excellent gold potential. At this time geometry and controls are not well-understood, although a clear relationship has been seen with albite-sulphide alteration and veining, as well as calcite veining. The gold mineralization is thought likely to extend under the adjacent ultra-mafic cap rock and this potential will be tested by later drilling.
Porphyry Copper-Gold Alteration and Mineralization Assemblages
Holes one and two targeted the high-grade copper veins. They were terminated at shallow depths on encountering ultra-mafics following thin intercepts of altered monzonite; hole one intersecting 8.40 meters of 0.22 percent copper and hole two intersecting 23.5 meters of 417 parts per million (ppm) copper. Holes three and four both encountered thick sections of anomalous copper, as well as copper-mineralized veins, both associated with porphyry-style alteration. Copper mineralization is associated with albite-sulphide and quartz-sulphide veins in proximity to dyke swarms. Chalcopyrite occurs as disseminations in country rock and as veins and veinlets. Hole three encountered 44.40 meters of 272 ppm copper. Hole four intersected 83.5 meters of 367 ppm copper, including 1.9 meters of 0.28 percent copper associated with rose quartz veins typical of porphyry systems. Drill results of holes three and four suggest close proximity to a porphyry system related to alkaline intrusions (a diorite-monzonite-syenite complex). Eighty meters to the southeast of hole four, Mindoro has previously reported that small scale miners mined veins of high-grade copper ore grading from 5 to 15 percent copper which was being shipped to China for processing. Drilling is now targeting the projected intrusive source of the dyke and vein swarms.
Hole five (see map) attempted to drill into the large chargeability anomaly to the south. This hole was lost at 188.65 meters, very close to the plotted position of the chargeability anomaly, after passing through 100 meters of ultra-mafics and encountering interpreted basal thrust faults; likely very close to the lower contact with intrusives below. A small man-portable rig is being used, which has performed very well, but which could not handle the heavy ground at this depth. Now that the mineralization model has been confirmed, a larger rig will be used to test the chargeability anomalies beneath the ultra-mafic cap at a later date. Assay results are awaited for hole five. Drilling will continue in the American Tunnels window to test the source of the mineralized vein swarms below the window.
The mineralized veins and dykes are associated with alkaline porphyry alteration assemblages of sodic-calcite type. Petrologic work indicates that in the propylitic zone alteration consists of chlorite-epidote-albite-tremolite-calcite-pyrite (chalcopyrite-gold). Potassic alteration is seen in some dykes and vein swarms where the alteration assemblage is actinolite-albite-biotite-K feldspar-chlorite-epidote-chalcopyrite-gold-magnetite. The potassic alteration assemblage, with associated copper mineralization in places, suggests close proximity to the main body of porphyry mineralization.
These alteration assemblages are characteristic of alkaline porphyry systems, as opposed to the more common calc-alkaline systems in Island Arcs such as the Philippines. Alkaline porphyries are an important class of porphyry mineralization globally, and classic examples are seen in British Columbia, where grades tend to be higher than their calc-alkaline counterparts. The accompanying model shows the interpreted genetic model for the Agata gold and porphyry copper-gold mineralization, as well as the mineralization environments intersected to date by drilling.
GOLD - COPPER MINERALIZATION ON THE AGATA PROJECT
American Tunnels is a small erosional window through ultra-mafic cap rocks within an extensive, six kilometre trend of strong IP chargeability anomalies associated with extensive alteration, geochemical anomalies, and abundant gold and copper-gold showings. There are over 100 shallow artisanal mines and workings within the trend, but mineralization is mostly obscured by ultra-mafic cap rock of variable thickness, and the nature of mineralization has been uncertain until now.
ABOUT AMERICAN TUNNELS
The American Tunnels area has a long and continuing history of small scale, artisanal gold mining, which peaked with about 3000 miners in the mid 1980s. Gold is mined from a honeycombing of shallow (5 to 20 meters) underground workings, estimated to be several hundred meters in extent, within an area of about 200 meters by 225 meters at American Tunnels. Free gold is also present in streams draining ultra-mafic cap rocks several hundred meters north of American Tunnels. There are also dozens of artisanal gold workings within other erosional windows to the south on the Agata Project.
The miners follow narrow high-grade veins, stock-works and fracture-filled zones near the top of an intrusive complex. Small scale miners provided some grade information, of varying degrees of reliability, from more recent workings. Unfortunately, most information has been lost for ever. Recovered gold grades were reportedly in a wide range from 2 g/t gold to as high as plus 1,000 g/t gold. Local mineralization controls are not well-understood.. Supergene enrichment of gold is likely at very near-surface levels, but the presence of significant hypogene (primary) gold has been established.
Porphyry Copper-Gold Target
In the past year small scale miners were actively mining high-grade copper from shallow workings over an area of about 150 m by 50 m at American Tunnels. These were mined by manual methods and ore grading 5 percent to 15 percent copper was sent by local buyers to China for processing. Late in 2008, lower copper prices terminated the copper mining, however, with increasing copper prices, small-scale mining of a high-grade lens of copper mineralization has re-commenced.
American Tunnels is characterized by a chargeability anomaly, extending over 800 meters by 300 meters, with associated resistivity and magnetic anomalies. As reported on November 17, 2008, extensive underground sampling of the copper workings gave high copper values, associated in places with high gold and molybdenum values. Mineralization is at the top of multi-phase intrusives, on the cusp of the chargeability anomaly, and is interpreted as a high-grade, late-stage veins proximal to porphyry copper-gold mineralization. American Tunnels is in the center of a six kilometer trend of chargeability anomalies and at a point where the chargeability is near-surface.
Tony Climie, P.Geol, is the Qualified Person responsible for monitoring the supervision and quality control of Mindoro's programs and who has reviewed and verified the technical information contained in this news release.
Mindoro is a Tier 1 Issuer trading on the TSX Venture Exchange (MIO) and the Frankfurt Stock Exchange (WKN 906167). Mindoro is focused on copper-gold and nickel exploration in the Philippines with a strategy of advancing early stage opportunities to production or joint venture. Mindoro has NI 43-101 resource estimates on its Agata North nickel-cobalt project and on both its Lobo (SWB) and Archangel (Kay Tanda) gold-silver projects. Mindoro has identified 22 porphyry copper-gold prospects and has a Memorandum of Understanding with Avocet Mining and a Memorandum of Agreement with Gold Fields covering its Batangas projects.
Mindoro is well positioned to capitalize on the global demand for gold with plans to drill the Lobo and El Paso copper-gold projects, funded by Gold Fields, and drill the American Tunnels gold /copper-gold project, commencing in August. . Final results are also awaited from due diligence drilling on the Kay Tanda gold project, funded by Avocet. Additional near-term objectives include finalizing one to two joint venture arrangements on Mindoro's porphyry copper-gold prospects at Pan de Azucar and Surigao and identifying a suitable partner to fund development of the significant Agata North nickel resource.
For further information, contact:
Mindoro Head Office
Penny Gould, President
Tel: 780.413.8187 or
Toll Free: 1.877.413.8187
Investor Relations -- Canada
Senergy Communications Inc.
Investor Relations - Europe
This release may contain forward-looking statements including management's assessments of future plans and operations, and expectations of future production. These statements are based on current expectations that involve a number of risks and uncertainties, which could cause actual results to differ materially from those anticipated. These risks include, but are not limited to, the risks associated with the mining and exploration industry (e.g. operational risks in development, exploration and production; delays or changes in plans with respect to exploration or development projects or capital expenditures; the uncertainty of reserve estimates; the uncertainty of estimates and projections relating to production and the uncertainty of the availability of capital). The assumptions used in the preparation of such statements, although considered reasonable at the time of preparation, may prove to be imprecise and, as such, undue reliance should not be placed on forward-looking statements.
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