why petroleum products, coal, minerals like iron ore, etc. are accumulated only in particular places on earth ?
It requires particular conditions for stuff to be able to form and then continue to be preserved. The right conditions don't exist everywhere.
Because the processes that created them occurred only in limited places. Diamonds are in volcano pipes. Iron can form chemically in bogs (bog iron) and be collected in lumps - no bog, no iron. Peat is organic material fallen in a depression in the ground and kept wet so it slowly rots. Do you have peat near you? I don't. Coal, oil and gas were the result of peat like deposits on a massive scale that were overlaid with sediment and crushed - no massive growth of plants to die, no deposits. Gold, silver, etc., are usually the result of chemical accumulation and conversion.
