JOHANNESBURG (Reuters) - South Africa's rand weakened on Friday after both the current account and trade deficits widened in the third quarter, renewing concerns about the economy. But stocks ended higher, logging their biggest weekly gain in nearly five months with Sibanye Gold in the spotlight after the miner unveiled a $2.2 billion cross-border acquisition. By 1500 GMT the rand had slipped 0.88 percent to 13.7650 per dollar, extending the previous session's losses as the greenback rose to price in a near certain interest rate hike by the Federal Reserve next week. South Africa's current account deficit widened to 4.1 percent of gross domestic product in the third quarter of 2016, while the trade account also showed a shortfall, the central bank said on Friday. "Given the country’s structural income account deficit, we expect that the overall shortfall will remain relatively wide," said Capital Economics Africa economist John Ashbourne. "This is the key reason why we expect that the rand will remain under pressure in 2017 and 2018. The rand backtracked after the data and remained on the back foot for most of the session, near its softest in one week, in low volume trade with most traders wrapping up positions ahead of December holiday period. In fixed income, the yield for the benchmark issue due in 2026 inched lower, cutting 0.5 basis point to 8.89 percent. On the bourse, Sibanye was in focus after the miner said it would buy Stillwater Mining, the sole U.S. platinum miner, for $2.2 billion in cash, an audacious move that takes the company outside its home market and underlines chief executive Neal Froneman's determination to branch out of gold mining. Shares in Sibanye slumped 15.3 percent to 24.01, the biggest percentage fall in their history as investors fret over the acquisition size, which is larger than the company's $1.9 billion market value. The blue-chip JSE Top-40 index was up 0.7 percent at 44,220, bringing gains for the week to about 3 percent - the best week since mid-July. The broader All-share index rose by the same margin to 50,899. Trading volumes were low with more than 241 million shares changing hands compared with last year's daily average of 296 million shares. (Reporting by Mfuneko Toyana and Tiisetso Motsoeneng)