Photos by R. Norman Matheny: Emperor penguins and a killer whale share Antarctica's coastal area; US flag (far right) marks the geographic pole; flags of Antarctica Treaty members fly nearby; Scientists put explosive in glacier crevice for seismic test; Found at 1,500-foot depth, 81-pound cod is weighed, tagged, and released by US scientist Lisa Crockett

At first glance Antarctica, the seventh continent, is but a huge block of ice. But it has become a giant chessboard of high-stakes diplomacy.

Frozen, desolate, and windy, it is a land larger than China. It is home only to a few species of animals and, for temporary stays, a few hundred scientists and tourists.

For nearly six months a year it lies in total darkness. Explorers call it ``an awful place.''

Yet it is coming under an international spotlight every day. A colossal treasure chest of resources is believed to be buried under Antarctica's thick ice-cap. Scientific evidence points at deposits of platinum, nickel, copper, chromium, zinc, cobalt, gold, tin, and the largest coal field in the world.

Who owns these minerals?

At present, 16 nations are negotiating a legal framework for mining Antartica's wealth. It is presumed they would allocate the profits among themselves. They include Australia, New Zealand, Chile, Argentina, Britain, Norway, United States, Soviet Union, South Africa, Japan, France, Belgium, Poland, Brazil, India, and West Germany.

Twelve of the 16 nations signed the original Antarctica Treaty in 1959. Four more -- Poland, Brazil, India, West Germany -- later joined this ``club,'' known as the Antarctica Treaty Consultative Parties.

The group meets about twice a year, with the next meeting being held in Brazil this month. Meanwhile, other nations are challenging the claims on Antarctica, which they consider to be ``the common heritage of mankind.'' At the United Nations, Malaysia has taken the lead and managed to inscribe ``the question of Antarctica'' on next fall's UN agenda.

An Asian diplomat says, ``Many of us remember that the Russians sold Alaska to the US in 1867 for $7.2 million. The Czar did not expect Alaska to become a major source of energy for America. We are not about to sell our right to share Antarctica's wealth for a plate of lentils.''

Treaty members do not want the treaty altered. ``It has worked well,'' says one diplomat from a member nation. ``It has kept nuclear weapons out of Antarctica. It has demilitarized it. It has promoted international scientific cooperation in Antarctica.''

Indeed scientific teams have engaged in research in such areas as cartography, geology, seismics, mag-netics, glaciology, and metrology.

There is plenty to explore. The continent covers one-tenth of the earth's land surface, or approximately 5.1 million square miles. Its permanent ice cap covers 98 percent of the land and contains nearly three-quarters of the world's store of fresh water. The ice averages 7,090 feet in thickness, but at some points is more than 15,000 feet deep.

The weight of the ice has depressed the land some 200 feet on average, putting one-third of the land mass below sea level. The continent, nevertheless, has the highest average elevation of all the continents: 5,900 feet.

Oddly enough, the amount of sunlight at the South Pole nearly equals that at the equator. Still, the world's record lowest temperature -- minus 89.6 degrees F. -- was measured in Antarctica in July 1983 at New Zealand's Vanda Station.

A workshop recently held under US auspices at the Beardmore Glacier Remote Field Camp in Antarctica allowed representatives of 30 countries to get the facts about various scientific programs carried out in Antarctica, often in collaboration.

The question of who owns Antarctica is far from settled by the treaty. Its legal status remains murky. The treaty doesn't acknowledge or reject territorial claims -- including some overlapping. The United States and the Soviet Union reject all existing claims but reserve the right to make claims. The US wants an ``open door'' policy allowing free access to the continent's wealth. ``First come, first served,'' says one US diplomat privately.

``The 1959 Antarctica Treaty has no legal value. It reminds one of the 1884 Berlin Treaty through which seven European powers carved up colonial empires in Africa for themselves,'' says one African ambassador.

A diplomatic race has begun between those treaty members who believe that the only way to keep Antarctica under the ``club's'' jurisdiction is to democratize it, to accommodate the interest of others, to coopt large nations such as Mexico, Nigeria, China, and those who push toward the adoption of an Antarctica convention somewhat similar to the Law of the Sea Treaty, one analyst says.

But hard-liners (the US, USSR, and Chile among them) inside the ``club'' are opposed to any concessions and savor stalling tactics, according to reliable sources. On the side of the treaty's opponents, the cheerleaders favor a gradual, nonconfrontational approach: ``the salami slicing tactic,'' as one treaty member diplomat calls it.

Another 16 countries adhere to the treaty but are not allowed to sit in on the group's meetings. They are: Bulgaria, China, Czechoslovakia, Denmark, Finland, East Germany, Hungary, Italy, the Netherlands, Papua New Guinea, Romania, Spain, Uruguay, Peru, Cuba, and Sweden.

``One must not underestimate the treaty members: countries such as the US, USSR, France, Britain, India have a good deal of influence and can stem the challenge of the `have-nots.' When the US and the Soviet Union stand shoulder-to-shoulder, there is not much that the rest of the world can do,'' a European expert says.