Argentina's stock exchange has included aluminum producer Aluar Aluminio Argentino (ALUA.BA) in its main Merval index for the third quarter, and has dropped Banco Patagonia (BPAT.BA).

The changes take effect Wednesday, the exchange said late Tuesday in a statement.

The Merval was one of the best performing indexes in the second quarter, rising 41%, largely driven by the impact of a 41% increase in oil prices on the two major stocks, Tenaris (TS) and the supplemental listing of Brazilian oil giant Petroleo Brasileiro (PBR), or Petrobras.

Aluar is the smallest component of the new Merval index, accounting for 1.7% of the total, the exchange said. Earlier this month, the Aluar board voted to issue 500 million new shares, to raise about $346 million.

Steel tube maker Tenaris, owned by Argentine-based conglomerate Techint but incorporated in Luxembourg, remains the heavyweight, accounting for 47.6% of the index, while Petrobras accounts for 13.6%.

Other components include: Grupo Galicia (GGAL), which accounts for 8.1%, Petrobras' local Argentine unit Petrobras Energia (PBE) accounts for 5.3%, Telecom Argentina (TECO2.BA) 5.2%, Pampa Holdings (PAMP.BA) 5.2%, Banco Macro SA (BMA) 4.6%, Siderar (ERAR.BA) 3.4%, BBV Banco Frances (FRAN) 2.6% and Edenor (EDN) 2.6%.

-By Matthew Cowley, Dow Jones Newswires; +54 11 4103 6740;