The S&P 500 index Thursday afternoon turned positive amid a broad-based rally in U.S. equity markets, coming as some easing of swirling geopolitical tensions was taking hold. The S&P 500 index SPX, +0.83% was most recently up 1.2% at 2,673, with a break above 2,673.61, its closing value for 2017, pushing the broad-market gauge into positive territory and representing its highest level since about three weeks, according to FactSet data. Meanwhile, the Dow Jones Industrial Average DJIA, +1.21% was up 374 points, or 1.6%, at 24,569 and the Nasdaq Composite Index COMP, +1.01% was advancing 1.3% at 7,161.