** Tempest Minerals TEM.AX plunges 20% to A$0.004; set for weakest session since March 24

** Mineral explorer intends to raise A$1 mln ($628,400); Cambrian Limited investing A$250,000

** Placement of up to 200 mln shares at A$0.005 vs TEM's last close of A$0.005 on March 27

** About ~484,000 shares traded, 2x the 30-day avg

** Stock down 20% YTD

($1 = A$1.5913)

(Reporting by Manasi Dasa in Bengaluru)

((Manasi.DasaSundeep@thomsonreuters.com;))