* Fed minutes indicate rate hike in 2015; members differ onmonth
* Mylan jumps after offering to buy Perrigo for about $29bln
* Alcoa flat in extended trading after results
* Indexes up: Dow 0.2 pct, S&P 0.3 pct, Nasdaq 0.8 pct (Updates to market close, Alcoa results)
By Ryan Vlastelica
NEW YORK, April 8 (Reuters) - U.S. stocks ended a volatilesession with modest gains on Wednesday after minutes from a U.S.Federal Reserve meeting indicated that the central bank remainedon track for a interest rate hike this year.
Major indexes moved between negative territory and sessionhighs after the news as traders parsed the minutes for clues asto when the first rise could occur. Some Fed participants wenton record saying they expected upcoming economic data wouldwarrant an initial rate increase in June, while othersanticipated a hike later in 2015 due to recent strength in theU.S. dollar.
Market participants had been expecting the first rate hiketo come in September or later, with last week's muchweaker-than-expected March payroll report pointing to slowinggrowth. The central bank has said it would only raise rates whendata suggests the economy is strong enough to withstand it.
"June would come as a surprise," said Alan Gayle, seniorinvestment strategist and director of asset allocation atRidgeWorth Investments in Atlanta, Georgia. "If the Fed movesmonetary policy in an arbitrarily fast manner, that would be adetriment for stocks."
Fed officials acknowledged risks from overseas and a weakstart to the year at their March meeting but remained confidentin the strength of the recovery, the minutes showed.
Markets were supported boosted by merger activity in thehealthcare sector, though the energy sector was weak as crudeoil plunged.
Mylan jumped 14.8 percent to $68.36 after thegeneric drugmaker offered to buy Perrigo Co for about$29 billion in cash and stock. Perrigo jumped 18.4 percent to$195. The two companies were the biggestpercentage gainers on the S&P 500.
U.S. crude futures dropped 6.6 percent to settle at$50.42 a barrel after U.S. Energy Information Administrationdata showed the largest weekly build in oil inventories sinceMarch 2001. The news offset Royal Dutch Shell's $70 billion bid for rival BG Group.
The S&P Energy index fell 1 percent while ExxonMobil lost 2 percent to $84.06 and Chevron Corp shed 1.7 percent to $106.66.
The Dow Jones industrial average rose 27.09 points,or 0.15 percent, to 17,902.51, the S&P 500 gained 5.57points, or 0.27 percent, to 2,081.9 and the Nasdaq Composite added 40.59 points, or 0.83 percent, to 4,950.82.
After the market closed, Alcoa Inc reportedfirst-quarter revenue that was below expectations. The stock,which is viewed as the unofficial kick-off to the earningsseason, was flat in extended trading.
Advancing issues outnumbered declining ones on the NYSE by1,847 to 1,163, for a 1.59-to-1 ratio on the upside; on theNasdaq, 1,739 issues rose and 979 fell for a 1.78-to-1 ratiofavoring advancers.
The benchmark S&P 500 index was posting 12 new 52-week highsand no new lows; the Nasdaq Composite was recording 79 new highsand 29 new lows.
About 5.68 billion shares traded on all U.S. platforms,according to BATS exchange data, below the month-to-date averageof 6.25 billion. (Editing by Meredith Mazzilli)
