BUENOS AIRES, March 13 (Reuters) - Argentina's stock, currency and bond market trends on Friday.
* MerVal stocks index .MERV rose for a fourth consecutive session, gaining 1.74 percent to a three-week high of 1,043.33 points.
* Bellwether Tenaris TENA.BA, which makes steel products for the oil industry, gained 3.1 percent to 34.45 pesos in heavy volume despite lower crude prices.
* Stock purchases were not dampened by President Cristina Fernandez's surprise announcement that she would try to move up mid-term elections to preempt political impact of the economic slowdown, even though the move was seen as reinforcing notions that the Argentine government is unpredictable.
* On the broad market volume was tame at $12 million, almost half of which was Tenaris trading. Of active issues 43 advanced, 25 declined and nine were unchanged.
* Traders said the Fernandez electoral move did mute interest in bonds, which are more sensitive to local news and mostly fell in price in over-the-counter trade in Buenos Aires.
* "The news was a bucket of cold water," said Augusto Farina, trader with Amirante Galitis brokerage.
* The 2038 Par bond denominated in dollars fell 2.5 percent ARPARD=RASL to an ask price of 18.90.
* In formal exchange between banks the peso weakened by 0.07 percent to 3.6475/3.6500 per dollar ARS=RASL. The peso has weakened almost daily for months.
* The Central Bank has a managed float policy for the foreign exchange market and has allowed the peso to slowly lose value so that Argentine exports can remain competitive, but injects dollars into the market most days to keep it from sliding too fast. The peso has lost some 5.5 percent of its value against the dollar since the beginning of the year.
* In informal trade between foreign exchange houses, as measured by Reuters, the peso closed flat at 3.7300/3.7350 ARSB=. (Reporting by Walter Bianchi, writing by Fiona Ortiz; Editing by Leslie Adler)