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Agata Gold and Copper-Gold Prospects
In addition to the nickel laterite mineralization, remarkably, Agata has a cluster of porphyry copper-gold prospects and two epithermal gold prospects which are also being advanced by Mindoro. The two unrelated mineralization types are in totally different geological settings. The gold and copper-gold prospects are summarized below.
Agata Project Copper-Gold Prospects
American Tunnels
Artisanal miners have been mining epithermal gold in the American Tunnels area for several decades (see the map "Agata Project Copper-Gold Prospects" above). Artisanal miners are now mining high-grade copper ore from six shafts and tunnels at Agata. This phenomenon is the result of both the discovery of the high-grade copper mineralization and high copper prices, which can support this small scale mining and transportation of raw ore to China for processing.
Mindoro, working with the Philippine Mines and Geosciences Bureau, encourages local miners to profit from legitimate small-scale mining of shallow ores, providing that this is done in an environmentally and socially acceptable manner. Mindoro is working in several areas to assist in the formation of small-scale mining cooperatives to assist this process. Mindoro sees this as a mutually beneficial operation; with the artisanal miners earning a living and at the same time providing useful information on the potential for large-scale associated deposits at depth. The relatively small loss of ore at these shallow levels is not considered a detriment to potential large scale mining operations by Mindoro.
Photo, above: Close-up of gold recovered. Small ball mills are used
to crush the ore, which is then panned. Recovery is very low from this
kind of operation.
Photo, above: Artisanal miner recovering gold from small scale operation,
American Tunnels, Agata.
The six shafts and tunnels extend over an area of 150 meters by 50 meters. A further eleven workings are being actively mined for epithermal gold (an overprinting shallower event). The copper ore is being mined by manual methods; ore grading 5 percent to 15 percent copper is loaded into 40-kg sacks and sold to local buyers to be sent to China for processing. Mindoro sampled one of the more easily accessible shafts, obtaining the following results from channel samples:
1.1 m vertical channel sample across exposed part of dyke at 7.91% copper, 0.23 g/t gold and 35.70 g/t silver;
1.0 m horizontal channel sample across floor of shaft at 4.89% copper, 0.15 g/t gold and 16.80 g/t silver;
1.9 m vertical channel sample across exposed part of dyke at 7.37% copper, 0.13 g/t gold and 27.80 g/t silver;
1.05 m vertical channel sample across exposed part of dyke at 2.02% copper, 0.07 g/t gold and 7.70 g/t silver.
Photo, above: High-grade copper mineralization (chalcopyrite and bornite)
from artisanal mining, American Tunnels, Agata.
Mapping by Mindoro and petrology work by an independent petrologist, indicate mineralization is associated with multi-phase syenite, quartz monzonite, monzodiorite and diorite intrusives. These occur as dykes, sills, and small stocks intruding ultramafic rocks. Petrographic studies indicate early potassic alteration (secondary biotite, actinolite), plus the copper minerals chalcopyrite, covellite and bornite. This is overprinted by later phyllic (sericite±calcite±actinolite±epidote) and skarn alteration/ mineralization. These features are indicative of a porphyry copper setting. A younger epithermal gold mineralization event cuts the earlier porphyry-related alteration.
The American Tunnels prospect is characterized by a strong IP chargeability anomaly, extending over 800 meters by 300 meters, is capped by a resistivity anomaly and coincident with a magnetic anomaly. Extensive copper, gold and zinc soil anomalies are associated. The IP chargeability anomaly is part of a string of strong chargeability anomalies extending over at least six kilometers of strike through the Agata Project, which are associated with intersections of splays of the Philippine Fault and cross-cutting faults. In a remarkable geological coincidence, extensive nickel laterite mineralization is juxtaposed in close proximity to the porphyry copper-gold prospects, and is itself the subject of intensive economic evaluation and pre-development work by Mindoro.
The American Tunnels prospect is an untested high-priority drill target for both epithermal gold and, especially, for porphyry copper-gold mineralization. The extent of alteration, abundance and strength of copper-gold showings, and of the associated IP anomalies, indicate a source of considerable potential interest.
Assmicor Prospect
During the 1980s, thousands of artisanal miners mined a saprolite (soil) horizon at Assmicor to shallow depths. In 1999, seven of eight drill holes completed by Mindoro intersected better than 0.5 g/t gold near surface in oxidized intrusives and dykes. The two best holes were 1.1 g/t gold over 19 meters and 1.4 g/t gold over 24 meters. The mineralization is open to the north and east.
Limestone Prospect
At the Limestone Prospect, geology consists of silty limestone with strong gold-in-soil anomalies occurring in an area of approximately 600 meters by 500 meters. Artisanal miners previously panned gold from the soils and mined gold from shallow workings in the limestone. Two 1999 holes drilled by Mindoro at the eastern edge of the soil anomalies encountered 2.7 g/t gold and 2.2 g/t gold over seven and eight meters respectively, at shallow depths. Deeper sections of mineralization were also encountered in both holes. Mineralization at the Limestone Prospect resembles important limestone-hosted gold deposits in Nevada, USA.
Assmicor Porphyry Copper-Gold Prospect
Alteration, accompanied by grey quartz-magnetite veins with copper and gold mineralization, characteristic of the margins of a porphyry copper-gold system, are associated with east-dipping dykes and intrusions intersected in 1999 drill-hole 11.
North Porphyry Target
The North Target occurs at the intersection of northeast-southwest faults with a splay of the north-trending Philippine Fault, which is the structural setting of porphyry copper-gold deposits in the Surigao District. The North Target is a very large and strong chargeability anomaly of greater than 28 m/secs covering about 1.2 kilometers by 500 meters. It is coincident with soil copper and gold anomalies, and unusually intense alteration of ultra-mafic rocks (pyrite and magnetite disseminations and silica veining). Recent panning of heavy mineral concentrates taken along creeks draining the North Target yielded significant gold counts of up to 21 grains from 26 kg of raw creek sediment sample draining ultra-mafic rocks. This implies significant mineralization "leakage" from intrusive rocks below, and very possibly a porphyry mineralization source. Several copper showings and intrusive dykes have also been found in the area.
Late in 2005, drilling commenced at the North Target. Considerable operational difficulties were experienced in the intensely fractured broken and gougy ultra-mafic cap rock and three holes were lost at shallow depths. This degree of structural preparation is consistent with that seen associated with a porphyry copper-gold system. At a future date, it is planned to pre-collar drill holes with a reverse circulation rig and then continue with diamond drilling below.
South Porphyry Target
South Target is also a large, 1.5 kilometer by 500 meters, and strong chargeability anomaly of greater than 28 m/secs. It has a large, flanking high resistivity anomaly. Geology consists of limestone, greenschist and ultra-mafics. Small dykes or stocks of altered intrusive, likely the top of a much larger intrusive complex, have been mapped. Zones of structurally controlled phyllic alteration have also been defined. There are historical and ongoing artisanal gold mining operations in this area. Soil geochemical surveys carried out by Mindoro in 1997 partially covered the South Target and defined gold, zinc and copper anomalies. The South Target geological, geochemical and geophysical results strongly point to a porphyry copper-gold system at depth.
In 2006, a single hole was drilled on the South Target. This also encountered operational difficulties and was terminated before target depth. However, in this case it is believed that the target can be drilled from the western side and the difficult ultra-mafic cap rock circumvented.
Mindoro Nickel Laterite Projects in the Surigao District
Agata Nickel Laterite Project
Geology of the Agata Project consists of greenschists, ultramafics, volcanics and multi-phase intrusives. Widespread serpentinized harzburgite and localized lenses of dunite and pyroxenite form an area of conspicuous peneplain (erosional surface) on the Agata hills. The nickel laterite developed on the ultramafics, and trend generally northeast, parallel to geological strike.
The soil profile is intensely ferruginous in this region. The nickel laterite profile consists of the ferruginous cover, limonite zone, saprolite zone, and saprolitic rock. Relic cobbles of highly fractured and serpentinized ultramafic rock are scattered throughout the profiles. The nickel mineral garnierite is common within the lower horizons of the profile.
Agata Project - Nickel Laterite Resources and Exploration Target
The map "Agata Project -- Nickel Laterite Resource" above shows the distribution of nickel laterite mineralization mapped to date on the Agata Project, as well as the SRMI Mine immediately to the south of Agata.
The Agata nickel laterite project is on the Agata MPSA and has been subdivided into two areas: Agata North, which is being advanced by Mindoro, and Agata South, which is a joint venture with Delta Earthmoving, Inc., a private Philippine company.
Agata North - Initial DSO Exploration Target
As reported in March 2007, the initial objective on the Agata North project was to define a NI 43-101-compliant resource adequate, initially, for three to five years of production at a rate of 500,000 to 700,000 wet metric tonnes (WMT) per annum of DSO for the production of nickel pig iron and other ferronickel products in China, India and Korea (i.e., target tonnage from 1,500,000 to 4,900,000 WMT).
During the course of this drilling, Mindoro recognized that the nickel laterite resource on the Agata, and other projects, has the potential to support a much larger scale integrated mining and processing operation, and plans were made to advance the DSO alternative on a short turn basis only, as the opportunity arose, while Mindoro focused on defining the global nickel laterite resource potential, and carried out an evaluation of enhanced value, local processing alternatives.
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