** Shares of Australia's Challenger Gold CEL.AX rise as
much as 4.6% to A$0.046, their highest level since Dec. 17
** Stock posts its biggest intraday pct gain since Dec. 23
** Gold and copper explorer enters toll processing agreement
with Austral Gold AGD.AX unit Casposo Argentina Mining
** Under agreement, Casposo to process mineralised material
from CEL's Hualilan project at its plant in Argentina
** Transaction to create new revenue stream for Austral
Gold, including a $3 mln fixed payment - CEL
** CEL stock down 40.5% this year, as of last close
(Reporting by Roshan Thomas in Bengaluru)
((Roshan.Thomas@thomsonreuters.com))