* Fourth consecutive surplus in export-dependent country * Chile growing robustly on domestic demand, investment * Both exports and imports fall from month earlier SANTIAGO, March 7 (Reuters) - Chile posted a trade surplus of $68 million in February, narrower than the three previous monthly surpluses as both exports and imports dipped, the central bank said on Thursday. The economy of the world's No.1 copper producer depends heavily on exports, which also include wood products, wine, fruits and salmon. Booming consumer spending has also buoyed imports. The trade balance figure compares with a $764 million surplus in February 2012, according to central bank data. Export revenue totaled about $5.940 billion in February of this year, the lowest since September, while imports were about $5.872 billion, the lowest since June. Export revenue was also mildly down compared with February 2012, when it clocked $6.320 billion. Imports, on the other hand, came in a whisker higher than February of last year's $5.557 billion. "The moderation of the trade surplus at the margin may exacerbate officials' concerns about Chile's deteriorating current account," Goldman Sachs said in a note to clients. "We note, however, that capital goods imports have grown substantially more than consumption goods imports, largely owing to the acceleration of investment in the tradables sector (mining)," the note added. "Hence, the lower trade surplus today is likely financing the expansion of future exports, reducing the risk of future external imbalances." With unemployment at a six-year low, growth exceeding forecasts and capital pouring in, some analysts have questioned whether the investors' darling economy is at risk of overheating. Domestic risks to Chile's booming economy have become more important in the short term, but have not translated into higher inflationary pressures, central bank head Rodrigo Vergara said on Wednesday. The bank has kept its key interest rate on hold since a surprise cut in January 2012, as it weighs robust local growth against lingering global woes. COPPER EXPORT REVENUE DOWN Chile's copper export revenue was down at $3.192 billion in February, compared with $3.474 billion in January and $3.461 billion in February of last year, the bank added. Copper prices lost more than 4 percent in February.