EMERGING MARKETS-Oil producers drive Brazil stock index lower

* Petrobras weakens ahead of earnings, report beats estimates * OGX January production numbers disappoint * Brazil Bovespa falls 1.28 pct, Mexico bourse closed By Asher Levine SAO PAULO, Feb 4 (Reuters) - Brazilian stocks slipped on Monday with shares of heavily weighted oil producers Petrobras and OGX falling on concerns over profit and production. Chile's bourse also dropped, for the first session in four, while Mexico's stock market was closed for a holiday. Brazil's