Nov 10 (Reuters) - Origin Energy Ltd (ORG.AX), Australia's no.2 power producer and energy retailer, backed an A$18.4 billion ($11.8 billion) non-binding buyout offer from a consortium led by Canada's Brookfield Asset Management, the companies said on Thursday. The deal sent Origin's share price soaring nearly 40% in early trade to A$8.14. Origin opened its books to the consortium after it raised its offer to A$9 per share in cash, a near 55% premium to Origin's last close of A$5.81. The bid from Brookfield comes after it was rebuffed earlier this year when it led a $3.5 billion takeover offer for Australia's top power producer, AGL Energy (AGL.AX). Under the indicative proposal submitted on Thursday, Brookfield would acquire Origin's energy markets business, while MidOcean Energy, the other consortium partner, would take control of Origin's integrated gas business, including its 27.5% stake in Australia Pacific LNG (APLNG).

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