BUZZ-Antofagasta: Buys 50 pct stake in Barrick Chilean copper mine
** Copper miner Antofagasta down 1.9 pct after buying a 50 pct stake in Barrick Gold's Zaldivar mine in Chile for $1 bln
** Antofagasta would become the operator of copper mine Zaldivar
** Stock second-largest loser on FTSE 100, hovering near 6-yr lows first seen on Monday, with a third of its 30 day avg volume having gone through in the first hour of trade
** Broader UK mining sector also down 0.69 pct
** Goldman Sachs cut PT on co to 490p from 500p, keep "sell" rating, citing the company's valuation
** Co trades at 22.6x its earnings for the next 12 months, a 50 pct premium to the median of its peers, according to Thomson Reuters data (email@example.com)
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