* Wall St declines top 1.5 percent* Fed minutes show worry over global economy, strong dollar* Treasuries yields touch recent record lows* Brent oil under $91 a barrel(Adds steepening Wall Street decline, latest prices)By Michael ConnorNEW YORK, Oct 9 (Reuters) - Wall Street slumped on Thursday as anxieties about global economic growth smothered a short-lived, Federal Reserve-sparked rally in equi