Initial returns of a two-day referendum ending today showed a turnout overwhelmingly in favor of a new constitution that will formally vest supreme powers in Ayatollah Ruhollah Khomeini.

Meanwhile, it was learned that new Foreign Minister Sadegh Ghotbzadeh has lost his influential job as head of the government-controlled radio and television.

The referendum on the constitution has been pointed to by independent observers as a potential watershed in the 4-week-old crisis over the 50 Americans being held hostage here. The taking of the hostages and the accompanying anti-American fervor have greatly benefited Khomeini's revolutionary leadership and have been used to build support for the constitution. Now that the voting is over, there has been speculation that the Iranians might become more accommodating in attempting to work out a solution to the hostage situation.

As expected, the initial referendum returns showed that voting was running 60 to 1 in favor of the new constitution. Iranian authorities did not immediately reveal, however the extent of participation in the referendum, which was boycotted by a variety of ethnic and political groups. These critics charged that the constitution gives dictatorial power to the clergy under Khomeini and does not meet demands for regional autonomy.

The Iranians who did participate largely obeyed the ruling clergy's directives to vote "yes" in the open balloting. Moslem clergymen sat in front of ballot boxes at several locations and instructed voters to deposit the green cards, the color representing Islam and signifing a vote for the constitution, rather than the red cards, which signified a "no" vote.

The National Iranian Radio and television network also repeatedly exhorted Iranians throughout the day tovote in favor of the new charter.

It was not clear whether the Revolutionary Council's decision to dismiss the controversial Ghotbzadeh as head of the network was related to the referendum. The council reached the decision at a meeting last night, but had yet to announce it more than 24 hours later.

Observers suggested that the council may have wanted to limited Ghotbzadeh to one job. That was the ostensible motive last week when the council relieved Abol Hassan Bani-Sadr as foreign minister but left him in charge of the finance and other economic posts.

The 43-year-old Ghotbzadeh told friends earlier today that he was considering abandoning the communications post he had held since soon after the February revolution because of "the strain of holding two jobs."

For the time being, the National Iranian Radio and Televsion network will be managed by a committee, it was learned.

During his tenure as Iran's media chief, Ghotbzadeh alienated many segments of Iranians society, ranging from leftists thrown out of radio-television jobs to apolitical Iranians furious at the banning of all American programs, polular music and light entertainment.

The last protest against his stewardship occurred only last night, when, according to Iranian press reports, a crowd of 20,000 demonstrated in front of the radio-television office in the northwestern city of Tabriz to protest "censorship" and broadcasting of "false news."

The crowd reportedly was incensed by the official radio and television news claiming that people in Tabriz and surrounding Azerbaijan province were giving an enthusiastic reception to the constitutional referendum.

In fact, tens of thousands of Tarizis marched two nights ago to underline their decision to boycott the referendum, and reports suggest voting was only moderate throughout the province.

Most Azerbaijanis, Kurds, Baluchis and Turkomans -- who together make up roughly half of Iran's population -- apparently followed their leaders' abstention orders. This dimmed Ayatollah Ruhollah Khomeini's hopes of winning a massive "yes" vote for his controversial consititution, which effectively confers full powers on the 79-year-old religious leader.

In another sign of tension, the majority Kurdistan Democratic Party announced today it would end its unilateral cease-fire in the western province on Dec. 19 unless the government amended the constitution to meet its demands. o

The Kurds are demanding regional autonomy and thus a federal constitution in place of the unitary draft proposed for national approval.

However, in an attempt to get out the vote, Khomeini promised that amendments to the constitutin could be made even after its formal adoption.

Indicative of government worries about the sluggish turnout was the decision to keep the polls open beyond the normal 6 p.m. closing time in the vote, which began yesterday.