The Inter-American Development Bank has approved two loans totaling $60.3 million to help enlarge the Northrn Gas Pipeline in Argentine.

According to the IADB, the goals of the program are to meet the growing demand for natural gas i northern Argentina; to accelerate the replacement of fuel oil with gas, which is in plentiful supply; and to improve petroleum production, which currently is inhibited by the lack of adequate gas pipeline capacity.

The loan was made to an Argentine public corporation to help complete the second stage expansion of the pipeline between campo Duran in the north and Buenos Aires. The bank has approved seven earlier loans totaling $236.4 million for pipeline projects in Argentina.

The current phase of the project is expected to cost $200 million, of which the bank's loans will cover 30.1 percent, the bank said. The loans incude $60 million from the banks inter-regional capital fund for 15 years at a variable interest rate tied to the cost of borrowing, and $300,000 from ordinary capital resources for a 20-year term at an annual interest rate of 4 percent.

*The IADB has announced an offering in the Eurodollar market of $150 million in 10-year, 10.5 percent notes.

The notes, which are not redeemable prior to maturity on Sept. 11, 1995, were placed at their par value.

The net proceeds from the sale of the otes will be incorporated into the bank's ordinary capital resources, the IADB said. Export-Import Bank

*The Export-Import Bank has approved $1.5 million in loans and loan guarantees to a Chilean firm to help finance an engineering feasibility study for a proposed hydroelectric project on the Colorado River 40 miles east of Santiago.

The loan package will assist the firm in purchasing engineering services from an Englewood, Colo., company, PRC Engineering. The Ex-Im Bank will provide a direct loan of $1.3 million and will back $225,000 in private financing.