The deal will see U.S. specialty chemical maker Rockwood Holdings Inc. and China's Chengdu Tianqi Industry Group form a joint venture to share ownership of Australia's Talison Lithium Pty Ltd.
Former King & Wood Mallesons global litigation head Beau Deleuil will join the U.S. firm in April.
The Australian firm has brought aboard a 13-lawyer practice group from rival Herbert Geer.
Peter McDonald was previously a partner at Herbert Smith Freehills.
Rebekah Gay was previously a partner at Sydney boutique firm Shelston IP.
Energy and resources specialist Simon Panegyres was previously a principal at Allion Legal.
The shifting market, a series of departures and leadership changes—in the U.S. as well as Asia—have raised questions about the firm's Asia strategy. But chairman Bradley Butwin insists that O'Melveny's commitment to Asia is as strong as it ever was.