London midday: Barclays, miners provide a lift in London

- Investors welcome departure of Barclays CEO- Stimulus hopes drive gains for equity markets- Miners track metals prices higherTrade was choppy on Tuesday morning, but the Footsie edged higher on the back of strength in the mining sector. However, the index stayed within a narrow range with just 20 points separating its intraday high and low.Yesterday's disappointing manufacturing data in the US has prompted calls for the Federal Reserve to begin fresh stimulus into the world's largest economy. The ISM reported that the manufacturing sector contracted for the first time since July 2009. According to BNP Paribas, weak employment figures later this week may add to pressure on the Fed. There are also calls for China to cut its reserve requirement ratio (RRR) for its banks in an effort to boost liquidity. The China Securities Journal said that the RRR, currently at 20%, should be reduced again to lower the chance of a liquidity crunch next month. Meanwhile, investors will be looking ahead to policy decisions by the European Central Bank (ECB) and the Bank of England (BoE) on Thursday. The ECB is widely expected to cut interest rates to a new record-low, while the BoE is predicted to ramp up its asset purchase programme.FTSE 100: Bob Diamond resigns as Barclays CEO Making headlines this morning was the news that Bob Diamond has called its quits at Barclays, bowing in to political pressure following last week's news that the bank was involved in Libor manipulation. Marcus Agius, who said yesterday that he would resign as Chairman, is to become a full-time Chairman while the board searches for a new CEO. Shares advanced after this morning's announcement. Sector peer RBS, which was reported yesterday to have sacked numerous traders over alleged Libor-fixing during the last year, headed the other way with shares slightly lower by lunchtime. Prime Minister David Cameron announced yesterday that there would be a parliamentary inquiry into the matter and that the Serious Fraud Office is looking at whether criminal prosecutions are needed.Providing a lift on the blue-chip index were the miners as metals prices firmed on stimulus speculation. Vedanta, Rio Tinto, Kazakhmys, Fresnillo, ENRC and BHP Billiton were all making gains in spite of Deutsche Bank cutting target prices across the sector.Deutsche Bank also reduced its target price for oil titan BP this morning, which was one of the worst performers of the day. In other broker news, hedge fund manager Man Group was hit with a downgrade by Credit Suisse from 'outperform' to 'neutral', with the broker estimating that assets under management have fallen by 12% in the second quarter owing to a "tough" market environment.FTSE 250: Talvivaara plummets after disappointing guidanceResource group Talvivaara was bucking the trend after saying that it is unlikely to hit its nickel production targets this year as a result of flooding, scheduled maintenance and a fatality-related stoppage during its second quarter. Shares were 14% lower by midday.Sector peer Avocet fell after Nomura slashed its target price on the stock by 45% following the recent production downgrade and news of a delayed project expansion.Oil explorer Salamander Energy fell after saying that test results at its dig in the Gulf of Thailand are "conclusive", with analysis showing that water is present in the tested section; in other words the Far East-1 well cannot be used for production. FTSE 100 - RisersVedanta Resources (VED) 946.50p +4.47%Barclays (BARC) 174.05p +3.36%Kazakhmys (KAZ) 747.00p +2.33%Rio Tinto (RIO) 3,126.00p +2.14%Meggitt (MGGT) 395.50p +1.85%Amec (AMEC) 1,045.00p +1.85%Fresnillo (FRES) 1,515.00p +1.68%Aviva (AV.) 287.40p +1.66%Standard Chartered (STAN) 1,442.50p +1.66%Weir Group (WEIR) 1,589.00p +1.66%FTSE 100 - FallersAberdeen Asset Management (ADN) 256.20p -3.21%Kingfisher (KGF) 283.50p -1.90%ITV (ITV) 76.70p -1.41%Severn Trent (SVT) 1,642.00p -1.20%United Utilities Group (UU.) 671.50p -1.18%SSE (SSE) 1,387.00p -1.00%BP (BP.) 428.20p -0.99%GKN (GKN) 179.90p -0.99%Diageo (DGE) 1,642.50p -0.93%Pearson (PSON) 1,251.00p -0.87%FTSE 250 - RisersOcado Group (OCDO) 79.95p +6.60%Centamin (DI) (CEY) 74.40p +5.08%Wood Group (John) (WG.) 729.00p +3.92%Brown (N.) Group (BWNG) 256.80p +3.34%Bumi (BUMI) 319.00p +2.90%Hunting (HTG) 760.00p +2.63%Aquarius Platinum Ltd. (AQP) 49.38p +2.62%African Barrick Gold (ABG) 403.10p +2.52%Barr (A.G.) (BAG) 414.70p +2.40%EnQuest (ENQ) 112.70p +2.36%FTSE 250 - FallersTalvivaara Mining Company (TALV) 145.60p -14.35%Avocet Mining (AVM) 73.75p -4.34%Chemring Group (CHG) 263.60p -3.83%FirstGroup (FGP) 226.30p -3.08%Yule Catto & Co (YULC) 139.40p -2.79%Taylor Wimpey (TW.) 48.63p -2.74%Salamander Energy (SMDR) 167.00p -2.68%Laird (LRD) 186.80p -2.61%Man Group (EMG) 72.60p -2.48%Barratt Developments (BDEV) 141.20p -2.35%BC