** Shares of Australia's Mammoth Minerals M79.AX rise as much as 3.8% to A$0.082, their biggest intraday pct gain since March 5

** Copper explorer says it will acquire Imperial Gold Mine in Nevada, U.S.

** Near 24,096 shares change hands, vs 30-day average volume of 1.8 million shares

** Stock has fallen 28.7% this year, including session moves

(Reporting by Roshan Thomas in Bengaluru)

((Roshan.Thomas@thomsonreuters.com))