* Available tin inventories drop by nearly a third
* Strikers at Chilean copper mine block restart attempt at port (Recasts, adds closing prices)
By Maytaal Angel
LONDON, March 17 (Reuters) - Copper rose on Friday and posted its biggest weekly gain since mid-February in response to a weak U.S. dollar and ongoing mine supply concerns, while tin clocked its largest weekly gain in a year.
Three-month copper on the London Metal Exchange ended up 0.4 percent at $5,934 a tonne, charting a weekly gain of 3.5 percent.
The dollar index is down around 1 percent this week after the U.S. Federal Reserve on Wednesday signalled a slower pace of monetary tightening than expected. A weaker dollar boosts the buying power of non-U.S. investors.
Striking workers at Chile’s Escondida, the world’s biggest copper mine, are blocking attempts by owner BHP Billiton to renew operations at a major port nearby as the stoppage enters its sixth week.
“How long do these supply problems go on for? You’re losing 150,000-200,000 tonnes of copper supply every month ... (and) in China, demand for copper concentrate remains strong,” Warren Patterson, commodities strategist at ING, said.
Fixed-asset investment in China, which consumes nearly half the world’s copper, grew 8.9 percent in January and February from a year ago, largely due to strong property and infrastructure construction.
In the U.S., factory output increased for a sixth straight month in February, as rising commodity prices boost demand for machinery and other equipment.
Tin ended up 0.6 percent at $20,275 a tonne, its strongest week since that ended March 4, 2016.
LME inventory data showed 1,000 tonnes of tin was booked for delivery out of warehouses, pushing on-warrant or available stocks down by nearly a third.
“We should keep in mind the underlying tin market looks tight,” an industry source said.
“China’s import of tin concentrates fell sharply in January, possibly pointing to a peak in Myanmar’s mine output. And Peru’s Minsur recently published tin metal production guidance for 2017 well below forecasts.”
Aluminium ended up 0.7 percent at $1,914.
Russian aluminium giant Rusal forecast demand growing by 5 percent this year and a global market deficit widening to 1.1 million tonnes.
Zinc ended up 1.9 percent at $2,882 on expectations the closure and suspensions of big mines will create shortages. ING’s Patterson said there was no sign that mines were planning to reopen.
Lead ended up 2.1 percent at $2,290 while nickel closed up 0.4 percent at $10,260.
Three month LME copper
Most active ShFE copper
Three month LME aluminium
Most active ShFE aluminium
Three month LME zinc
Most active ShFE zinc
Three month LME lead
Most active ShFE lead
Three month LME nickel
Most active ShFE nickel
Three month LME tin
Most active ShFE tin
ARBS ($1 = 6.9026 Chinese yuan renminbi) (Additional reporting by Melanie Burton. Editing by Jane Merriman and Elaine Hardcastle)