Zions Bancorp., the Salt Lake-based holding company for Zions First National Bank and other financial subsidiaries, said Tuesday it will enter the Colorado market through the acquisition of Aspen Bancshares, based in Aspen, Colo.

The merger is valued at some $75 million or about $19.25 per share of Aspen's stock - some 5 percent more than Aspen's closing price Tuesday of $18.75 per share, down 25 cents.Aspen also gave Zions options to purchase 19.9 percent of Aspen's shares if the deal should fall through or a competing offer is made by another company.

The merger is structured to be a tax-free exchange of shares and will be accounted for as a pooling-of-interests, Zions said.

Zions shares closed Tuesday at $90.25, up $1.25. Zions said the rate of the stock exchange in the purchase applies as long as Zion shares range between $83 and $93.

The deal is subject to approval of Aspen shareholders and banking regulators. Zions said it is expected to close in March or April of next year.

Harris H. Simmons, president and chief executive officer of Zions, said Aspen's management will be "largely retained."

"We believe this is a great opportunity for both banking companies which will enable Zions to expand its franchise into the vibrant western Colorado market while providing Aspen customers the financial strength of a larger, high-performing financial services company," said Simmons.

He said Aspen president Charles Israel "has distinguished himself as the nation's pre-eminent private banker, and I am very pleased that he and other members of Aspen's management have decided to join our team."

Israel agreed that Aspen's competitive position will be enhanced by the merger.

With assets of approximately $450 million, Aspen Bancshares is the largest banking company based in western Colorado with 11 offices in the state and one in Farmington, N.M. Its banking units are Pitkin County Bank and Trust, Centennial Savings Bank and Valley National Bank of Cortez.

With assets of $6.8 billion, Zions Bancorp. operates throughout Utah, Arizona, and Nevada through its Zions First National Bank, National Bank of Arizona, and Nevada State Bank subsidiaries.

Bloomberg Business News contributed to this report.