AA, NASDAQAAS) shares slumped more than 16% after it announced it will be acquiring MAG Silver Corp (TSX:MAG) in a deal valued of US$2.1 billion. Per the terms of the deal, MAG shareholders can choose to receive US$20.54 per share in cash, 0.755 common shares of Pan American per MAG share, or a mix of both, with the total cash portion capped at US$500 million. 