The resource-heavy FTSE 100 finished Tuesday's session in the red despite some big gains in the mining sector, as concerns about global growth and a disappointing reading of German sentiment provided a drag on sentiment.This marks the third consecutive decline for London's benchmark index.Markets on the whole were on the cautious side as investors awoke to the news of fatal explosions at the Boston Marathon last night which left three dead and hundreds injured. It is still unknown who is responsible for the bombs at the finishing line, though the White House has said that the incident would be handled as an "act of terror".Nevertheless, Wall Street benchmarks opened strongly in nearby New York as Goldman Sachs joined a growing list of companies to report better-than-expected earnings. Banking peers Citigroup, Wells Fargo and JPMorgan Chase have all beaten forecasts with their first-quarter results in the past week.Markets this side of the Pond were extending losses seen yesterday when disappointing growth figures from China and concerns over demand sent commodity prices tumbling. Gold, in particular, suffered its worst one-day slump in 30 years, falling 9.1%. Prices have since rebounded slightly.The International Monetary Fund today trimmed its global growth forecast for 2013 from 3.5% to 3.3%, saying that the world is now becoming a "three-speed economy". The UK, US, Eurozone and China all had their growth estimates lowered.Dampening the mood further today were economic sentiment figures from Germany which showed that investors were less confident than expected in April. The ZEW German economic sentiment indicator fell from 48.5 to 36.3 this month, missing the 41 estimate. Data from the UK was more in line with forecasts however, with the consumer price index unchanged at 2.8% in March. FTSE 100: 'Glenstrata' gets the all-clear from ChinaMiners on the whole were making strong gains today as investors viewed yesterday's sell-off as a buying opportunity. However, the big news in the sector was that the multi-billion-pound merger between Xstrata and Glencore has received the all-clear from Chinese regulators. Both stocks were firmly higher.Glencore said in a statement that the new company would have to sell its Las Bambas copper mine in Peru. Meanwhile, Xstrata's Chief Executive Officer Mick Davis has agreed to stand down following completion of the tie-up.Randgold Resources gained after saying that its giant Kibali gold project in the Democratic Republic of Congo (DRC) is "poised to deliver" and is on track to produce its first bar of gold before the end of the year. Fresnilllo, ENRC and Vedanta were also in demand this afternoon.AB Foods, the food ingredients and retail firm, was falling this morning after Credit Suisse downgraded the stock to 'neutral'. Chip designer ARM Holdings was lower after Societe Generale reiterated its bearish 'sell' rating on the stock.GKN also fell after Barclays Capital lowered the engineering firm from 'overweight' to 'equal weight', saying that after a strong run, the stock is "due for a pause".Supermarket giant Tesco was broadly flat ahead of its full-year results tomorrow. The group is expected to reveal its first fall in underlying annual profits in two decades, according to analysts.FTSE 250: Michael Page drops as profits declineRecruitment group Michael Page slumped early on after saying that it expects another challenging quarter ahead after "tough economic conditions and weak market confidence" weighed on its performance at the start of the year. Gross profit fell 6.7% in the first quarter.Oil and gas group Salamander Energy fell despite starting drilling on the Bedug-1 exploration well in the Bontang production sharing contract, in which it has a 100% operated interest.Leading the upside on the second-tier index were the miners as they attempted to recover lost ground. Lonmin, Ferrexpo, African Barrick Gold and Bumi were all making moderate gains. Bumi said this afternoon that its Chief Financial Officer Scott Merrillees is leaving this summer.FTSE 100 - RisersFresnillo (FRES) 1,161.00p +7.50%Eurasian Natural Resources Corp. (ENRC) 246.80p +3.65%Randgold Resources Ltd. (RRS) 4,672.00p +2.79%Xstrata (XTA) 986.00p +2.04%Johnson Matthey (JMAT) 2,377.00p +1.58%Vedanta Resources (VED) 1,123.00p +1.54%Royal Bank of Scotland Group (RBS) 283.80p +1.25%Glencore International (GLEN) 325.10p +1.25%easyJet (EZJ) 1,149.00p +0.97%BHP Billiton (BLT) 1,841.50p +0.93%FTSE 100 - FallersEvraz (EVR) 165.90p -3.49%ARM Holdings (ARM) 868.00p -3.18%Smith & Nephew (SN.) 741.50p -2.88%Amec (AMEC) 1,000.00p -2.72%Weir Group (WEIR) 2,214.00p -2.47%Babcock International Group (BAB) 1,034.00p -2.45%GKN (GKN) 250.80p -1.99%GlaxoSmithKline (GSK) 1,600.00p -1.87%Associated British Foods (ABF) 1,830.00p -1.82%Melrose Industries (MRO) 247.20p -1.79%FTSE 250 - RisersLonmin (LMI) 274.70p +7.05%African Barrick Gold (ABG) 180.60p +4.15%Ferrexpo (FXPO) 173.60p +3.95%Bumi (BUMI) 257.90p +3.37%BH Macro Ltd. EUR Shares (BHME) € 20.91 +2.90%Hochschild Mining (HOC) 247.00p +2.53%Big Yellow Group (BYG) 383.20p +2.51%Centamin (DI) (CEY) 38.60p +2.04%Intu Properties (INTU) 342.60p +1.96%Tullett Prebon (TLPR) 259.40p +1.85%FTSE 250 - FallersMichael Page International (MPI) 377.40p -5.01%SVG Capital (SVI) 386.80p -4.42%Interserve (IRV) 471.10p -3.36%Regus (RGU) 159.00p -3.34%Hunting (HTG) 827.50p -2.99%SIG (SHI) 150.70p -2.71%Ashtead Group (AHT) 598.50p -2.68%RPS Group (RPS) 252.40p -2.66%CSR (CSR) 489.50p -2.59%IP Group (IPO) 147.10p -2.58%BC