George Mason University, celebrating its 9th year as an autonomous, four-year institution, observed University Day this week by breaking ground for a second student union.

The honored guest at the ceremonies Tuesday was Dr. Lorin A. Thompson, first chancellor and president of the university when it became an independent institution in 1972.

Before the state legislature created a separate university, in Northern Virginia, George Mason had been a branch of the University of Virginia. Dr. Edgar F. Shannon Jr., the last University of Virginia president to oversee that joint administration, joined Thompson in the festivities commemorating George Mason's independence.

Shannon described George Mason as "a tribute to the foresight and contributions of the leaders and people of this community and its elected representatives at the local and state levels.

"The people of the community and the faculty of the University of Virginia worked together under Lorin Thompson, who provided remarkable leadership," said Shannon.

Shannon said George Mason is now getting "the recognition it deserves" because of Thompson's guidance during the university's formative years. "He was 64 years old, on the eve of retirement, when he began," Shannon noted. "He stayed on for seven years and what a fortunate seven years they were.

"He did such a remarkable job of keeping all the elements together."

More than 300 people attended the ground-breaking for the new student union, scheduled for completion in 1982 at a cost of $4.9 million. The facility will serve students in two new dormitories now under construction, according to Louanne Wheeler, a university spokeswoman.

"The first student union is already full of offices and doesn't have cafeteria services," she said. "The new building will offer food services to the new dormitories, which don't have kitchens."

Martha Turnage, vice president for public affairs, said the occasion marked "the completing of one era and moving on to another. What you have is a torch passing."

At the groundbreaking, the university also honored several longtime employes, including William M. McFarlane of the Department of Philosophy and Religion. McFarlane was recognized for his 30 years with the University of Virginia and George Mason.