FORT SIMPSON, CANADA, SEPT. 20 -- Pope John Paul II ended his North American trip today by celebrating mass with northern Canadian Indians and Eskimos in a huge open teepee set up on the river bank of this historic Northwest Territories trading post 380 miles south of the Arctic Circle.

In an address, the pope endorsed the native people's long quest for self-determination and economic control over some of the vast, mineral-rich Canadian north, issues that long have been a matter of contention for the northern natives and the Canadian government.

"Once again I affirm your right to a just and equitable measure of self-government, along with a land base and adequate resources for developing a viable economy for present and future generations," the pope said.

After the visit here, John Paul flew back to Edmonton, Alberta, and then departed for Rome.

The young activists who head the natives' political organizations said they were heartened by the pope's comments, which were not in the prepared text. They were inserted in the pope's speech last night at John Paul's insistence, Vatican officials said. They said they expected the remarks to put pressure on the government of Prime Minister Brian Mulroney to revive negotiations that the government abandoned when talks ended without agreement in March.

The 3 1/2-hour outdoor service was conducted in English, French, Latin and five native languages and incorporated the haunting, rhythmic chanting and drumming rituals of ancient spiritual tradition.

When the pope served communion to 100 native elders, he wore white vestments of caribou hide with colorful embroidery that were made by the women of one of the tribes upriver from Fort Simpson.

Although the pope did not mention it, the gestures seemed to many to be designed to heal old wounds left from the days when some Catholic missionaries had tried to do away with those customs.

"My coming among you looks back to your past in order to proclaim your dignity and support your destiny," he told them.

The estimated 5,000 people who gathered at the banks of the junction of the Mackenzie and Liard rivers had come by boat, by plane, by camper and by chartered bus from settlements in the nearby mountains, the southern plains and hundreds of miles away in the frozen Arctic.

Observers said it was the largest known assembly of people in the north. Young and old alike were in a high state of excitement about the international attention that the trip brought to this largely ignored part of the world.

John Paul tagged on the visit to his U.S. tour to fulfill a promise that he made three years ago when dense fog prevented his airplane from landing here during a 12-day tour of Canada.

The natives who had come here at that time were deeply disappointed, and some tribal elders interpreted the incident as a bad omen that meant there was a curse on the town and on them.

Anxieties rose again this morning when a light, chilly rain began to fall and the skies darkened just hours before the pope was to arrive. But the rain subsided when he appeared, and minutes later the rain stopped, the sun peeked through and a faint rainbow stretched across the sky. Many elderly people, visibly moved by the occasion, reverently kissed the pope's ring when he moved through the crowd to greet them.

Many of the young, including political leaders, are estranged from the church. They charge bitterly that a generation ago children were taken from their parents and villages and placed in residential schools run by Catholic missionaries. They say that they were spanked if they spoke in their native languages and that the drumming rituals of their culture were called pagan and were forbidden.

Indians said today they were proud that the services used and paid respect to those traditions. But they said they were dissatisfied that the pope did not apologize for the past, as he had done with American Indians in Arizona last week, and asserted that the Oblate order of missionaries who first came to the Canadian north in the mid-1850s and their successors had "taught you to love and appreciate the spiritual and cultural treasures of your way of life {and} respected your heritage, languages and customs."

"You just can't wipe that history away," said George Erasmus after the pope's address. "The missionaries did try to change our people from the way we were. That kind of thing has to be recognized. . . . Unless there is an openness in the church and reconciliation or attempt to bridge the church and the Dene spirituality, you'll still have that problem."

Erasmus, 39, one of the founders of the nine-year-old Dene Nation, a political movement that brought together the five tribes of the Mackenzie River Valley -- was one of the native leaders who had a 20-minute audience with the pope before his address today.

He and others said they did not bring up these concerns because they were talking to him about the absence in his prepared remarks of any mention of their struggle for self-government and control of land in the north, which they interpreted with alarm as a retreat from previous statements. The pope assured them that his position had not changed, they said.

When John Paul finished speaking today, they said, he turned to them and asked, "Well, did I address some of the things you wanted?"

Missionaries here say they are trying to find ways to blend native and Christian teachings.

A black bishop, visiting here from Chad, is to meet with local priests to tell how he overhauled the liturgy in his African country and devised new services that reflect the culture there, the Rev. George LaGrange, parish priest here, said.