The Hongkong and Shanghai Banking Corp. will acquire 51 percent of Marine Midland Banks by holding company for the 13th largest U.S. bank in what is believed to be the largest bank combination in history.

The arrangement was detailed Tuesday by the chairmen of the two financial institutions after Marine Midland directors voted unanimously to recommend the deal to shareholders.

The contemplated HSBC investment will pump $200 million into capital-starved Marine Midland in two stages in return for 6.7 million shares of newly issued Marine Midland common stock.

There also will be a cash tender offer by HSBC for about 25 percent of the Buffalo-based bank's currently outstanding 12.5 million shares to give the British-owned Asian bank a total stake of 51 percent.

"It's a partnership" was how HSBC Chairman Michael Sanberg described the arrangements although his bank will clearly have the controlling position. "We intend to work together not as one dominant partner or the other dominant partner but as equals" Sandberg said.

He said Marine Midland will continue to operate autonomously and under its present management, but the two banks may join forces at times in the international arena.

"Where we can together zero in on a project, we will have the strength and ability to do so," he told reporters. "The combined assets of our partnership will create an international financial organization which will rank, I suppose, among the two dozen or so largest in the world."

The Hong Kong bank's assets total $17 billion; Marine Midland's assets exceed $12 billion.

Edward Duffy, the clearly delighted Marine Midland chairman, called the development a "quantum step toward for Marine Midland" and one that will "vastly enhance our bank's competitive ability in the new environment of global banking."

Each bank will get three directorships on the board of the partner bank, according to the arrangement.

The transaction is subject to prior regulatory approval of the Federal Reserve Board and the New York Superintendent of Banks. In addition, shareholders of Marine Midland must approve sale of the newly issued shares. And a special meeting of the company's shareholders will be called for his purpose, though no date has been set.

"We see no difficulty," on regulatory approval, Sandberg said. Duffy, who indicated informal talks with regulators, already have been held, echoed that view.

But the process of getting regulatory clearance could be time-consuming and may take as long as a year, officials indicated.

HSBC also has a California subsidiary, the Hongkong Bank of California. Sandberg said he would leave the question of whether HSBC has to sell the West Coast operation up to the regulators. The Hong Kong Bank reportedly has considered unloading the California branches because state authorities threatened to tax the bank there based on the global earnings of the parent company.

Under the tems of the arrangement, HSBC will purchase a $100 million, 7.75 percent subordinated note of Marine Midland Banks Inc. upon the signing of a definitive agreement. Then, subject to the required regulatory and shareholder approval and upon successful completed cash tender offer for Marine Midland shares at a price not to be exceed $20 a share. HSBC may exchange the subordinated note for $3.3 million shares of newly issued stock at $30 share.

The second stage of transaction will occur on Dec. 31, 1980, unless an earlier date is specified by Marine Midland. At that time, HSBC will purchase an additional 3.33 million new shares at $30 each, for the second $100 million investment.

HSBC has agreed to limit its holdings in Marine Midland to 51 percent for at least five years after the transaction is consummated, and that it may not acquire additional shares unless a majority of the public shareholders at te time votes approval.

Sandberg said HSBC does not intend to get a majority on Marine Midland's board after 1980.

If regulatory approval is not obtained or the first stage of the transaction is not completed before March 31, 1979, either side can call the deal off.

For Marine Midland, the HSBC investment comes at a crucial time because the bank has found it impossible to tap American capital markets to support its growing asset base. The bank has had sharply reduced earnings for the last three years because of loan losses. In 1975, the bank was under surveillance by federal regulators because of its problems, and the subnormal earnings performancce caused it to reduce its dividend to shareholders.

Last year, Marine Midland had operating earnings of $17.4 million, more than double the previous year but still well below its historical performance.

The liaison with HSBC gives it ties to a far more profitable bank, and one with a strong banking presence not only in Asia, where it has 270 offices but also in the Mideast, where HSBC owns the british Bank of the Middle East.

Marine Midland also will get rare financial access to the People's Republic of China, because HSBC has a strong correspondent banking relationshop with the Bank of China, the international arm for the P.R.C.

Sandberg said anxiety about what happens to Hong Kong after the British lease on large parts of the crown colony expire in 1998 was "absolutely not" a factor in his bank's decision to seek the Marine Midland investment. He noted access to the U.S. market and the large deposit base here as well as admiration for the turnaround Marine Midland's management has cccomplished as factors in seeking a stake in this particular U.S. bank.

Marine Midland chairman Duffy confirmed that other foreign banks has approached him about a possible investment, but would not give names.

In Hong Kong, HSBC is known simply as the bank founded 113 years ago by Buccaneer British merchants, it financed the Chinese opium and tea trades in its early days. Last year, the bank earned $113 million on its $17 billion asset base.

The bank is the financial and commercial pivot for Hong Kong, owning Wardley Ltd., a major merchant bank, Cathay Pacific Airways, extensive shipping interests, and controlling interest in Hong Kongs largest English-language newsapaper, the South China Morning Post. Through the Post, it owns a significant share of the Asian Wall Street Journal and prints the Dow Jones paper on its presses.