The ongoing saga of the huge – and hapless – Ok Tedi mine

The mineral specimens were magnificent — massive magnetite- chalcopyrite, boulder-sized. The geologists had just brought them in from the field, 2000 miles by foot, helicopter and ‘plane.

It was late 1968, spring in the southern hemisphere, and I was visiting Kennecott Copper’s exploration office in Sydney, Australia. Kennecott, my employer, had, some years previously, conceived the idea of porphyry coppers on the mainland of what was then the territories of New Guinea and Papua. Exploration had proved to be extremely difficult, in wild country with no infrastructure, spectacularly sheer mountains and steep valleys, covered in almost impenetrable jungle where, it seemed, it almost never stopped raining. The inhabitants were members of primitive tribes not always well disposed to one another and not averse to settling inter-tribal disputes by breaking a few skulls.

Now the company’s persistence with its systematic and thorough exploration program appeared to have paid off with this discovery in a tributary of the headwaters of the Ok Tedi in the Star Mountains in the extreme west of the country. (the word Ok, I was told, meant river in the local dialect.)

I never visited Ok Tedi for Kennecott but, over the years before and after that day in Sydney, I remained well informed about the project through my colleagues, company reports, official meetings and friendly get-togethers.

The sequence of significant events included locating the skarn (in what was to be named Magnetite Creek, naturally) from which those mineralized boulders that I saw in Sydney had come; the finding of Mount Fubilan, the monzonite porphyry stock encircled by the skarns; and the discovery of the classic porphyry copper deposit within Mount Fubilan; complete with leached cap and supergene enriched zone. Surprising facts

There were surprises, too, such as the age determinations that showed the deposit to be only one million years old, a fact we old Arizona and British Columbia hands had difficulty accepting. Also, the effects of the rapid, deep tropical weathering that played havoc with our established ideas of porphyry copper interpretation from surface outcrops.

There followed a series of administrative and political manoeuvrings; the founding of the independent state of Papua New Guinea; the attempt to get a mining permit with acceptable (to Kennecott) terms; the eventual abandonment of negotiations by the company and the entry of others to continue exploration and development of the deposit; the increase in the price of gold that made the leached capping a great gold orebody and the drop in the price of copper that had the opposite effect on the underlying copper deposit; the more recent disputes between the operating company and the government regarding full development of the deposit, and so on. Quite a fascinating story with which I had been familiar, though second-hand, from the very beginning.

Now, in early 1987, I was visiting the Ok Tedi mine for the first time, on assignment for one of the shareholding companies, almost 20 years since that day in Sydney when I first saw the boulders from Magnetite Creek.

It was the “dry” season in the Star Mountains so, in mid-morning one could see the foothills and there was only broken cloud over Tabubil, the Ok Tedi mining settlement. The landing field was alive with activity, as all flights arrive and depart in the mornings before the clouds and rain move in. Typical tropical town

Tabubil is a newly-constructed, spread-out, pleasant, typical tropical mining town. Yet, it is like much older human settlements elsewhere, each successive civilization building on the remains of what was there before but, of course, compressed in time.

I saw the original Kennecott exploration camp; this was followed by the buildings of successor exploration companies; the next major stage of building was done by the engineering contractor to house its staff; and crowning the archaeological pile, several stages of building by Ok Tedi Mining for the present- day town of Tabubil.

Not that the old has been buried and forgotten; some of the Kennecott camp buildings are being used for such things as drill core storage and “temporary” houses, put up by the engineering contractor, are still being lived in.

From the town, 1,800 ft above sea level, an all-weather road winds its way for 12 miles to the mill site at 5,250 ft above sea level. Here, the new copper mill was in the final stages of completion, with the first copper produced during my visit. (Another bit of mining aside: some of the major items of mill equipment were scavenged from closed copper operations in the southwest United States.) In this type of mountainous terrain, you have to make your own real estate, usually at high cost, and there is very little wasted open space.

The road continues on from the mill to the mine, about two miles away at the top of Mount Fubilan, originally about 6,560 ft above sea level and now at 6,360 ft and decreasing. Hill being mined

One cannot really call it a pit as the whole hill is being cut down from the top.

Here, there is the typical, hectic activity seen in any major open pit mine moving 25,000 tons of ore a day; the large capacity trucks, shovels, blast-hole drill rigs, etc. By mid morning, the brief period of sunshine usually is gone and all this activity is carried out within the clouds.

The leached, oxidized capping has been the ore to date, making Ok Tedi one of the world’s great gold mines; over 600,000 oz in 1986 and about a million ounces projected for 1987, more gold in a year than from any other mine outside South Africa and the Soviet Union.

By the end of this decade, the capping essentially will be gone, but gold will still be a major product contained in the copper concentrate. Published reserves in 1987 list 23 million tons of leached capping ore at 0.064 oz/ton gold, 390 million tons of porphyry copper ore at 0.7%, plus 0.017 oz/ton gold, as well as ore in skarns totalling 32 million tons at 1.25% copper and 0.046 oz/ton gold. International workforce

Extensive training of the local labor force preceded production and ongoing training programs ensure the ever-increasing participation of Papua New Guineans. However, a young nation such as this has limited professional and technical manpower, far below what is is needed for the industrial development that is taking place throughout the country.

Thus, Ok Tedi still resembles a miniature United Nations. The professional mining men, engineers and geologists, come from all over the world and technical expertise, particularly regarding heavy equipment, is strongly Australian. More than 20 nationalities were represented while I was there, the largest foreign contingent being from the Philippines. I ate in the mess where, at mealtimes, the international character of the workforce was most evident. Mind-boggling statistics

The logistics of the Ok Tedi operation boggle the mind. The copper concentrate is piped from the mill site through Tabubil and on to a port facility at Kiunga on the Fly River, a distance of 100 miles. There, the concentrate, after dewatering, is loaded onto barges for a 460-nautical-mile trip to the coast, where it will be transferred to ocean-going vessels for export. All equipment for Ok Tedi takes the reverse trip up the river, being moved by road from Kiunga to Tabubil and the mill and mine up the mountain.

Personnel are moved in and out exclusively by air, with daily flights operated by Ok Tedi Mining and local commercial air carriers. Urgently needed equipment and spare parts also are flown in on the passenger runs. To ensure maximum utilization of passenger flights for this purpose, all passengers and their baggage are weighed to determine the available freight load on each flight.

The bringing into production and the continuing development of this great mineral deposit is indeed a major feat of mining enterprise. Papua New Guinea is rich in mineral resources, including the recent discovery of major oil deposits, and many other large projects are being developed or are in
the planning stage. Many of these will surpass Ok Tedi. However, Ok Tedi was the first of the mega-projects, discovered by explorationists of vision and developed out of the raw jungle into a modern industrial enterprise.003 K. A. Grace is a senior member of Robertson & Associates, consulting geologists and mining engineers in the Coopers & Lybrand Consulting Group.