EXPLORATION 1998 — Mindoro takes aim at gold-copper targets in Myanmar — Junior advances Kyaukkyi and Thida exploration properties

Historically, mineral production in Myanmar (formerly Burma) derived from small-scale gold and gemstone operations, both primary and alluvial. But several Canadian companies are now scanning the country for bigger game.

The 678,500-sq.-km country, which straddles the boundary between the Indian and Asian tectonic plates, is considered to have strong potential for Besshi-type volcanogenic massive sulphide (VMS) deposits. Several junior exploration companies believe the region is also highly prospective for gold.

One of the companies most active in the largely unexplored country is Mindoro Resources (MIO-A), which has received encouraging results from its evaluation of numerous VMS showings on Concession No. 11, a 50-50 joint venture with the Myanmar government.

Pyrite and chalcopyrite, associated with mafic volcanic rocks intercalated with sediments, occur in four separate localities, about 1.5 to 5 km apart, on the concession.

Both the geological setting and the geochemical signature of the mineralization are consistent with the Besshi type of VMS deposit (a well-known example being the Windy Craggy copper-cobalt deposit in British Columbia). Armed with this data, Mindoro is focusing on five primary targets, as described below.

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Kyaukkyi prospect

Among the most advanced gold-copper prospects, the Kyaukkyi has returned high gold and copper values from boulders and from two streams dubbed R-70 and R-72. Previous operator Leeward Capital (lwc-a) had located an extensive pan-concentrate gold anomaly here, grading up to 4.6 grams gold per tonne and 2.3% copper. Gossanous boulders with values of up to 18.3 grams gold, 26 grams silver and 0.72% copper were also found.

Petrography of the boulders found in R-70 has identified native gold, electrum, chalcopyrite and pyrite associated with quartz. An epithermal gold signature is suggested by anomalous values of arsenic and mercury.

Both boulder trains have now been traced to their suspected sources: R-70 boulders appear to be derived from a poorly exposed quartz-sulphide vein system, whereas the R-72 boulders, roughly 200 metres to the north, are derived from a jasperoid-sulphide zone of replacement-style mineralization.

Both prospects are hosted by mafic volcanics.

Mindoro has also located outcrops of dioritic intrusives and defined extensive and strong propylitic alteration (epidote-carbonate-chlorite) over an area measuring at least 1 km by 1 km. Within these perimeters are zones of quartz-sulphide stockworking, the sizes of which are not yet fully defined.

It now appears that the R-70 and R-72 showings are part of a larger, intrusive-related, alteration-mineralization system with possible bulk-tonnage gold potential. Accordingly, plans to drill-test the R-70 and R-72 showings have been deferred while the Kyaukkyi prospect is systematically re-evaluated.

Rock exposure at the prospect, in the form of outcrop and float, is deemed good, and Mindoro is confident it can bring the prospect to a relatively advanced stage through a systematic program of surface exploration.

Work in progress includes geological mapping, prospecting, soil geochemistry, trenching and rock sampling. The company reports that it has now defined a 1,000-by-750-metre area of variably silicified, carbonate, chlorite and hematite-altered mafic to intermediate volcanics, intruded by a series of similar rocks. Within this area, geological mapping and soil geochemistry have confirmed R-72 as a target area; a second prospect known as Kyaukkyi North has also been defined.

* R-72 Area — Seven recent grab samples from R-72 returned assays ranging from under 20 parts per billion (ppb) gold and 324 parts per million (ppm) copper to 5.63 grams gold per tonne and 4,343 ppm copper. The average grade was 1.78 grams gold and 0.27% copper.

A soil geochemical survey has defined an 800-by-100-metre anomaly with values between 127 and 835 ppm copper; gold values range up to 72 ppb. The gossanous boulders in the area have been traced back to this soil anomaly.

Trenching, chip and channel sampling programs are under way to evaluate the significance of the soil anomaly.

* Kyaukkyi North Area — Situated 750 metres northwest of the R-72 area, Kyaukkyi North coincides with a 550-by-600-metre zone of silicified, chloritized and variably carbonatized volcanics enclosed by sedimentary rocks. Kyaukkyi North lies on the northwestern boundary of the volcanics, where they form a prominent series of strongly silicified and hematite-altered ridges.

Six grab samples of altered boulders and outcrop returned values ranging from 0.47 gram gold and 0.5% copper to 16 grams gold and 5% copper. The average grade was 6.08 grams gold and 1.6% copper. The company notes that, because of poor outcrop exposure at Kyaukkyi North, it is not known at this time how representative these samples are; geological mapping, trenching and systematic rock sampling are under way to determine this.

* Dokhta Prospect — A limited, 10-hole program of diamond drilling in 1994 saw six drill holes hit stratabound massive sulphides averaging 1.9% copper over 4 metres (based on a range of 2.1% copper over 0.9 metre to 1.86% copper over 8.7 metres). Sampling by Mindoro indicates insignificant gold values are associated with the copper mineralization.

Economic modelling by Mindoro suggests that for grades of roughly 2% copper, at least 20 million tonnes of open-pit-minable material are required.

However, the company reports that high stripping ratios may preclude any possibility of an open-pit operation. Accordingly, no further work is planned on the prospect.

* Thida Prospect — Previous government work had defined a 900-by-150-metre, copper-in-soil geochemical anomaly, grading more than 143 ppm copper, with areas exceeding 0.1% copper. The program endeavored to evaluate the copper potential of the southern half of the anomaly, and included 10 short drill holes and limited underground exploration; the gold potential was ignored.

Stockwork mineralization was intersected in four drill holes.

Mindoro is focusing on the combined gold-copper potential of the northern half of the soil anomaly that extends over an area measuring 500 by 150 metres. The anomaly is centred over small stocks, or dykes, of diorite intruding mafic to intermediate volcanics, and is associated with multiple phases of brecciation and quartz-carbonate-albite-chlorite alteration with variable sulphide content.

Ten outcrop samples were collected across 400 metres of strike to characterize gold and copper values from strongly altered material. Values ranged from less than 0.02 gram gold and 0.2% copper to 8.54 grams gold and 4.6% copper. The average grade was 1.17 grams gold and 0.86% copper.

Six boulder samples were also collected, returning values ranging from 0.32 gram gold and 0.13% copper to 5.29 grams gold and 0.6% copper; the average was 1.48 grams gold and 0.33% copper.

The prospect is currently being subjected to geological mapping and systematic rock sampling in an effort to evaluate bulk-tonnage potential.

Reconnaissance evaluations are being carried out over an additional 34 targets consisting of aeromagnetic and geochemical anomalies.

Mindoro has determined that

the Dokhta prospect is an exhalative VMS occurrence, whereas Kyaukkyi, Thida and many of the other mineral occurrences within Concession No. 11 are interpreted as epigenetic veins, stockworks and replacements related to magmatic activity within an island-arc assemblage. Most of the concession thus conforms to a classic magmatic arc gold-copper setting.

The junior, which also operates exploration programs in Indonesia, the Philippines and Malaysia, has 13.4 million shares issued and working capital of about $3.1 million.

Recent changes in management include the appointment of Roger Morton to the position of chairman and Michael Grace to vice chairman.