Avis Budget Group Inc. (Nasdaq: CAR) has agreed to acquire Boston-based car-sharing company Zipcar Inc. (Nasdaq: ZIP) for approximately $500 million in cash, or $12.25 per share (49% premium to Monday’s closing price). www.zipcar.com

ArcelorMittal has agreed to sell a 15% stake in ArcelorMittal Mines Canada for $1.1 billion to an investor group that includes South Korea-listed POSCO and Taiwan-listed China Steel. www.arcelormittal.com

Iberdrola has agreed to sell 32 operating wind farms in France to a consortium that includes GE Energy Financial Services, MEAG and EDF Energies. The deal is valued at €350 million, plus another €50 million in potential earnouts.

Imation Corp. (NYSE: IMN) has acquired Nexsan Corp., a Thousand Oaks, Calif.-based maker of disk-based storage systems, for $105 million in cash and approximately $15 million in stock. Nexsan had raised over $17 million in VC funding since 2003, from firms like VantagePoint Venture Partners, GESFID, RRE Ventures and Beechtree Capital. It also had filed for an IPO in 2008, before later withdrawing registration due to “unfavorable market conditions.” www.nexsan.com

Qatar Telecom has increased its stake in Tunisian telecom operator Tunisiana from 75% to 90%, in a deal valued at $360 million. The Tunisian government will retain the remaining 10% position. www.qtel.qa

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