MINERAL EXPLORATION — Mispec hones skills at Jampang — Cigaru area serves as model for exploration

New exploration programs typically face many difficulties, and these are compounded when the area under consideration is extensive and plagued by heavy overburden. However, while the Jampang property in western Java, Indonesia, is vast (at 20,530 ha) and covered with tropical vegetation, geologists for Mispec Resources (mpe-m) feel they have a handle on the project thanks to work carried out by Dutch colonists in the 1920s.

For a little over a year now, Mispec has been honing its exploration techniques in a small area in the northern portion of the property, the objective being to outline bulk-tonnage epithermal quartz-vein deposits.

Initial efforts are paying off, with resource calculations soon expected for three zones: Lipi, Pasir Keusik and Puteran-Simpang.

Mispec first became involved in Java in late 1995, when it optioned the 7,700-ha Jampang property from its current partner, Hunamas Putra Interbuana, a private Indonesian company. The property is 185 km south of Jakarta.

The partners then increased their holdings to the current amount, which is nearly evenly divided between Jampang and the adjacent Jampang East blocks.

(Combined, the properties are loosely referred to as Jampang). In the former, Mispec holds a 30% interest and has the option of increasing this to 90%. In the latter, it has a 65% interest, which it can increase to 85%. Both increases are dependent on additional exploration expenditures.

Drilling at Jampang began in July 1996. The initial target was the Lipi zone, which was chosen on the basis of available data from old adits and surface work by the Dutch, as well as intermittent programs carried out over the past 30 years by Indonesian interests.

“We started drilling there first because we knew there were a lot of vein systems being mined by locals, and we just wanted to see if these were of potential economic widths and grades,” says Andre Talaska, Mispec’s Indonesian geology manager.

Several hits were made in these initial holes, which led to more than 30,000 metres of reverse-circulation (RC) and diamond drilling out over the next year.

Some of these early results ran as high as 8.5 grams gold over 6 metres and featured widths reaching up to 38 metres grading 2.59 grams gold. More recent drilling has led to the identification of the nearby Pasir Keusik and Puteran-Simpang zones of copper and gold mineralization.

Combined, the three zones comprise an area 1.5 km long by 600 metres wide, known as Cigaru.

Subsequent to the start of drilling, the company initiated a regional airborne magnetic and radiometric survey, consisting of 4,500 line km at 200-metre spacings, along with radar satellite imagery designed to penetrate the forest canopy and overburden. Lineament studies of the remote-sensing confirmed the regional trends highlighted by the magnetic survey. The predominant trend was north-northwest.

While drilling continued, the company concentrated its exploration in the Cigaru area. But before surface work could begin, the company faced the problem of obtaining modern maps. The best ones dated back to 1943, when the U.S. Army had carried out surveys during the Second World War. Aerial photographs were eventually used to develop maps at a scale of 1:10,000.

Mapping and geochemical crews then began the laborious job of unraveling the local geology at Cigaru, while other teams combed the countryside to test other prospective areas.

In the Cigaru area, surface work and drilling demonstrated that mineralization was hosted by hydrothermally altered and silicified volcanics, with gold occurring in epithermal veins and hydrothermal breccias. As well, visual and geochemical analysis of drill core suggested the higher-grade gold values were associated with sulphide minerals in the form of pyrite, chalcopyrite, galena and sphalerite.

The next step involved carrying out a ground geophysical program, involving magnetic and induced-polarization (IP) surveys. The former were carried out at 20-by-5-metre line spacings; the latter at 40-by-5-metre spacings, reaching a depth of 50 metres below surface.

The barren andesitic rocks were found to be magnetic-rich, except in areas where mineralizing fluids passed through the rocks. Also, the quartz and silica-rich zones with associated sulphides were highlighted by resistivity and chargeability anomalies.

“When we are looking for initial targets, priority is given to demagnetized zones plus chargeability anomalies,” says Talaska. “Then we look at other controlling features.”

The surveys also outlined several other prospective targets, some of which are known to be mineralized with gold.

Data from the magnetic survey confirmed the company’s belief that a fault zone cuts off the geology at the Puteran-Simpang zone, thus offering a potential explanation for problems that have arisen in correlating core data between some of the holes drilled there.

At Cigaru, Mispec employs a face-sampling hammer RC drill, which has been widely used in Australia to evaluate shallow, oxidized gold deposits. The technique is considered superior to diamond drilling in that it provides three to four times the sample volume of core drilling.

The company’s technique was recently checked and approved by an independent audit by Snowden Associates of Australia. The geological consulting firm also recommended down-hole surveying of the RC holes.

Soil geochemical results at Cigaru have been mixed. However, no problems have been encountered in the southern area of the property, where deep river valleys have dug deep into the Tertiary-aged volcanics, which are known to host gold mineralization.

Mispec is beginning to apply the information gleaned from Cigaru to other areas identified by preliminary regional exploration. The area currently being tested is the Cipaku area, 8 km to the south.

The company has carried out mapping and abundant stream sediment sampling, which outlined three west-northwest-trending zones of gold mineralization in an area measuring 5 km long by 500 metres wide area. The zone follows the regional trend seen in the aeromagnetic and radar satellite survey.

Sulphide-bearing quartz veins in the zones have returned values ranging from less than 1 gram gold and 1 gram silver to 50 grams gold and 826 grams silver.

Stream sediment sampling has also proved effective, returning anomalous gold, silver, copper, arsenic and mercury values. (It is belived the mercury originates from the tailings of local miners, who use it to liberate gold in their processing techniques.)

Ground magnetic surveys have also proven useful, as much of the Central zone coincides with a 400-metre-wide area of low magnetics, suggesting the existence of a hydrothermal system.

Currently, Mispec is testing the area with a 15-to-20-hole program of RC drilling, results from which are pending.

Several areas between Cipaku and Cigaru have been targeted for follow-up study.