The FTSE 100 looked set to register its third straight decline by Tuesday lunchtime, extending heavy losses made the day before as mining stocks were hammered by slowing growth in China. While miners were doing their best to rebound this morning, 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 bombs at the finishing line, though the White House has said that the incident would be handled as an "act of terror".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. Stock futures on Wall Street were pointing to a positive start when the opening bell rings in the next hours despite the tragic events in nearby Boston. Bellwether Citigroup yesterday beat forecasts with its first-quarter results, following in the footsteps of Wells Fargo and JPMorgan last week. Investment banking peer Goldman is now in focus and is due to release its earnings figures before markets open Stateside. The firm is expected to report earnings per share of $3.90, similar to the $3.92 the year before, according to FactSet. Revenues are forecast to fall from $9.95bn to $9.66bn.Disappointing first-quarter growth figures from China caused gold prices to plummet on Monday to a two-year low. Reports that Cyprus is selling part of its bullion holdings to raise money and speculation that the Federal Reserve could scale back quantitative easing were also a factor. Commodity prices tumbled across the board, with silver, copper and crude oil all taking a hit. The 9.1% one-day slump in the price of gold was the steepest fall in 30 years. The price of the precious metal had recovered by as much as 2.0% this morning.FTSE 100: Miners rebound after heavy sell-offMetal producers were doing their best to recover this morning as traders saw yesterday's heavy falls as potential buying opportunities. Fresnillo, ENRC and Randgold were making decent gains.However, Xstrata and Glencore were standout performers on market chatter that their proposed multi-billion-pound merger has received the all-clear from Chinese officials.Rio Tinto was also higher after reporting record first-quarter iron-ore production, whilePolymetal edged higher after saying that the flotation concentrator at its Mayskoye mine has been started up, producing its first dry gold concentrate.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".Meanwhile, investors were taking profits at supermarket giant Tesco with shares down ahead of the company's 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 attempt to recover lost ground. Lonmin, Centamin, Bumi, Hochschild Mining, Petropavlovsk and Kazakhmys were all making moderate gains.FTSE 100 - RisersXstrata (XTA) 1,020.00p +5.56%Randgold Resources Ltd. (RRS) 4,784.00p +5.26%Glencore International (GLEN) 335.70p +4.55%Fresnillo (FRES) 1,123.00p +3.98%Eurasian Natural Resources Corp. (ENRC) 247.20p +3.82%Vedanta Resources (VED) 1,129.00p +2.08%Anglo American (AAL) 1,598.00p +1.46%BHP Billiton (BLT) 1,843.50p +1.04%Antofagasta (ANTO) 946.00p +0.96%WPP (WPP) 1,049.00p +0.87%FTSE 100 - FallersARM Holdings (ARM) 855.50p -4.57%Weir Group (WEIR) 2,200.00p -3.08%IMI (IMI) 1,196.00p -2.37%Prudential (PRU) 1,037.00p -2.35%Associated British Foods (ABF) 1,821.00p -2.31%Evraz (EVR) 168.20p -2.15%Meggitt (MGGT) 471.20p -1.96%Amec (AMEC) 1,009.00p -1.85%Smith & Nephew (SN.) 749.50p -1.83%International Consolidated Airlines Group SA (CDI) (IAG) 246.00p -1.76%FTSE 250 - RisersLonmin (LMI) 274.00p +6.78%Centamin (DI) (CEY) 39.52p +4.47%Petropavlovsk (POG) 148.00p +4.37%Bumi (BUMI) 259.00p +3.81%Hochschild Mining (HOC) 247.70p +2.82%African Barrick Gold (ABG) 177.50p +2.36%Ophir Energy (OPHR) 409.20p +2.15%Kazakhmys (KAZ) 347.70p +2.02%JPMorgan Indian Inv Trust (JII) 373.90p +1.47%Intu Properties (INTU) 340.00p +1.19%FTSE 250 - FallersMichael Page International (MPI) 372.00p -6.37%Renishaw (RSW) 1,632.00p -4.51%Ashtead Group (AHT) 588.50p -4.31%SIG (SHI) 149.10p -3.74%RPS Group (RPS) 250.30p -3.47%Petra Diamonds Ltd.(DI) (PDL) 106.60p -3.27%International Personal Finance (IPF) 424.00p -3.22%IP Group (IPO) 146.20p -3.18%Cable & Wireless Communications (CWC) 41.18p -3.06%SVG Capital (SVI) 392.90p -2.92%BC