The giddying rise in gold prices came to a crashing halt today as the price of the metal plummeted both in Europe and New York, closing down $143 an ounce here.

The gold collapse came as the Chicago Board of Trade halted all new futures trading in silver for the next three months, a day after New York's Commodity Exchange virtually shut down its entire silver futures operation.

Both exchanges acted because they are afraid there is not enough silver around to satisfy all the customers who might demand delivery of the precious metal when their futures contracts expire -- during February in Chicago and during March in New York.

The price of silver fell $10 today, closing at $34 an ounce in the very limited trading that was still permitted.

Analysts said the plunge in gold prices was caused in part by a nervous reaction to the restrictions the U.S. metals exchanges put on their silver futures trading.

But traders here say that much of the gold price decline was due to a rumor that a major German bank sold 1 million ounces at this morning's "fixing" in London -- where representatives of Britain's five major gold trading houses get together to establish a consensus price.

Just before the morning fixing -- and after six hours of trading in Hong Kong where the price had fallen only slightly -- gold had been trading at about $812 an ounce in London, down $38 from the Monday afternoon fixing.

But the consensus price was announced at $763, a $49 drop within a matter of moments. The price continued to fall during the rest of the day in London and New York.

By the end of trading in New York, the price had skidded to $683 an ounce from its $826 close Monday.

The decline continued Wednesday in Hong Kong, where gold dropped $166.50 an ounce on the Chinese gold and silver exchange, opening the day at $670.

Vincent Conway of Merrill Lynch, Pierce, Fenner and Smith said there was no way to verify whether a German bank actually offered to sell 1 million ounces of gold. German and Swiss banks have been acting as agents for the nervous Middle East buyers who are thought to have driven the price of gold from about $430 an ounce in early December.

Although there is much "informed" speculation pointing to Arabs as the driving force behind the gold market -- and to a lesser extent the silver market -- the fact is that no one knows for sure who the buyers are.

"You tell me why a nervous Arab who is supposed to be afraid that his regime is going to fall suddenly ups and sells a million ounces. It doesn't make any sense," said one gold trader who asked not to be identified.

Conway said that if such a sizable offering had been made, it would be "logical" for the price to plunge because the "buyers weren't ready for it as they would be for a big U.S. auction."

Treasury Secretary G. William Miller said last week that the U.S. government did not plan to sell any more gold for the foreseeable future -- a statement that helped drive gold prices through the roof. Today, in Washington, Federal Reserve Board Chairman Paul A. Volcker said that if the government sold gold into the market it might help drive the prices down.

Miller, who is thought to have regretted his remark last week, today said that the sharp decline in gold prices shows that the market is "very volatile."

Thomas Donovan, of the Chicago Board of Trade, said the exchange put restrictions on silver trading today to insure that the problems in New York did not "spill our way."

The CBOT not only prohibited any new futures contracts in silver for January, February and March, it also ruled that traders must gradually unwind their positions in February, getting rid of 25 percent of their contracts each week of the month.

The New York and Chicago exchanges are worried that several large buyers of silver are attempting to corner the market by buying up large quantities of contracts requiring them to take delivery, then demanding delivery instead of selling the contracts at a profit.

Although there is plenty of silver floating around in the United States, the contracts on both the Chicago and New York exchanges require that delivery be made in specially-approved silver on deposit in certain warehouses. d

On the Commodity Exchange in New York (Comex), for example, there are about 19,000 contracts outstanding, each for 5,000 ounces of silver, that expire in March. That is about 95 million ounces of silver. For all the future months for which contracts are sold, total silver requirements are nearly 500 million ounces.

There are only about 77 million ounces on deposit in Comex warehouses and about 50 million ounces of that silver is already owned by the very individuals who could demand delivery in March.

Analysts say that big traders such as oil magnate Nelson Bunker Hunt and customers represented by Conti Commodity Services Inc. broker Norton Waltuch are among the prominent speculators involved in squeezing the market.

Hunt, and his brother Herbert, probably own more physical silver than anyone else in the world.

In normal futures trading, there is very little demand for actual delivery of the product. The futures market is usually considered an insurance market in which those who want to "look in" a price for their products sell "short" -- promising to deliver -- to speculators who are "long," or promise to accept delivery at a specified time and price.

If prices rise, the speculator makes a profit. If they fall, the person who's sold short -- such as a silver mine -- keeps the guaranteed price and the speculator loses money.

In either event, both holders of long contracts and short contracts generally sell them without making actual deliveries, making profits or taking losses on the sale of the contract.

Increasingly in recent months, however, speculators have been demanding delivery of metal, buying bigger and bigger positions as the contracts come nearer to expirations and forcing prices higher still.