* FTSE 100 index up 0.9 percent
* Miners, energy firms lifted by firmer commodity prices
* Invensys top riser on China rail deal
By Jon Hopkins
LONDON, Sept 17 (Reuters) - Britain's leading shares were higher around midday on Friday, lifted by a rally from heavyweight commodity stocks and banks, with Invensys the top riser after signing a deal with a Chinese rail company.
By 1106 GMT, the FTSE 100 index was 46.99 points higher, or up 0.9 percent, at 5,587.13, having closed down 0.3 percent on Thursday, its second consecutive daily decline.
"There's a lot of strength for the FTSE at the moment with a positive trend having formed, and I think it will keep on going, with the general feeling that is very well-supported," said Phil Gillett, a sales trader at Spreadex.
Energy was the top performing blue chip sector as the crude price moved higher once again, with BG Group up 1.1 percent and Royal Dutch Shell ahead 0.9 percent.
Gas distributor Centrica rose 0.6 percent after it doubled its stake in the North Sea's Statfjord Field in a 144 million pound ($224.6 million) deal that provides the firm with an additional 172 billion cubic feet of oil and gas reserves.
Miners were higher, rallying after recent falls in tandem with metal prices, with Kazakhmys and Antofagasta up 2.9 and 2.3 percent respectively.
Gold surged to a record and silver struck a new 2-1/2-year high, with precious metals miners Randgold Resources and Fresnillo up 1.0 and 0.7 percent respectively.
Banks also pushed higher, having softened in the previous two sessions as risk appetite returned among investors, with Royal Bank of Scotland standing out, 1.3 percent higher.
INVENSYS IN DEMAND
Engineering group Invensys was the top FTSE riser, up 5.5 percent after the firm announced its rail unit had signed a deal with Chinese manufacturer CSR, increasing its exposure to the rapidly growing Asian economy.
"We expect further collaborations to be announced which would logically cover mainline and high speed and this, in turn, underlines the pivotal position Invensys rail is developing for itself," Evolution Securities said in a note.
Aggreko was also a strong blue-chip riser, up 4.3 percent as Credit Suisse started coverage on the temporary power supplier, albeit with a "neutral" stance.
Food retailer Sainsbury, up 3.0 percent was boosted by a UBS upgrade to "buy" from "neutral"
Among the handful of blue chips on the downside, defensives got cold-shouldered as investors' risk appetite returned, with utilities among the worst off led by Severn Trent, down 0.7 percent.
U.S. stock futures pointed to a stronger start on Wall Street on Friday, extending gains made in the previous session, although investors will eye the latest U.S. inflation report ahead of the bell.
August U.S. consumer prices data are due at 1230 GMT,, while the preliminary reading of September Reuters/University of Michigan consumer sentiment is scheduled for release at 1355 GMT.
Britain's top share index is expected to barely rise between now and the end of 2010, but will bounce 8 percent by mid-2011 as support from overseas earnings offsets worries about the economy, a Reuters poll showed.
"We are sticking with our year-end target of 6,000 for the FTSE 100," Richard Hunter, head of UK Equities at Hargreaves Lansdown Stockbrokers, said.
"We've got the third-quarter reporting season coming along and if that exceeds expectations as the first and second did and there is proof of earnings momentum, then we could see a strong end to the year." (Additional reporting by David Brett; Editing by Jon Loades-Carter)