A supercartel to outdo OPEC? Strategic Materials Shortages: Dealing with Cartels, Embargoes, and Supply Disruptions, by Bohdan O. Szuprowicz. New York: John Wiley & Sons. $23.95.

This book, written by the president of an international market research firm, offers a scary thesis: the formation of a "supercartel" in strategic materials by the Soviet bloc and Marxist governments in southern Africa, including a black-ruled South Africa.

The Soviet Union, writes Mr. Szuprowicz "will soon have the opportunity of the century" of spreading communism throughout the world "by engaging in a resources war in which it enjoys all the advantages. All that is necessary is to gain control of the key High Africa countries that produce and supply most of the free world's strategic materials."

Since the Soviet Union has similar large reserves of major strategic materials, this supercartel would control more than 50 percent of the global output of about 15 of the most strategic materials in the world. "This would give the Soviets sufficient leverage to demand political and economic concessions [from the free world nations] that would be otherwise unwarranted by the free market forces," he theorizes.

The author reckons it is conceivable that the Soviet Union could demand unilateral nuclear disarmament by the West. Mr. Szuprowicz's study offers a good warning and a comprehensive review of this question. It also makes some controversial proposals about how the West can ensure supplies.

But he's far too early in giving up the south African ship to the Soviets. Since he wrote this book, Robert Mugabe, the Marxist President of Zimbabwe, has shown himself much more Western and market-oriented than in the past. Mozambique has been modifying its socialist practices out of economic necessity. And without weapons, it will be some years before the blacks of South Africa can win majority rule.