Geology, Prospecting and Exploration for Iron Ore Deposits Apr09

Geology, Prospecting and Exploration for Iron Ore Deposits...

Geology, Prospecting and Exploration for Iron Ore Deposits Iron has been known since antiquity. Iron is ubiquitous in the lithosphere as either a major constituent or in trace amounts. In abundance it ranks fourth behind oxygen, silicon and aluminum. Iron ores have a wide range of formation in geologic time as well as a wide geographic distribution. These ores are found in the oldest known rocks in the crust of the earth, with an age in excess of 2.5 billion years, as well as in rocks formed in various subsequent ages. In fact, iron ores are even forming today in the areas where iron oxides are being precipitated. Several thousands of iron occurrences are known throughout the world. They range in size from a few tons to several hundreds of millions of tons. Iron ore deposits are distributed in different regions of the world under varied geological conditions and in different geological formations. The largest ore concentration is found in banded sedimentary iron formations of Precambrian age. These formations constitute the bulk of iron ore resources of the world. Iron ores occur in a wide variety of geological environments in igneous, metamorphic or sedimentary rocks, or as weathering products of various primary iron bearing materials. Iron ores can be grouped into types of similar geological occurrence, composition and structure. The following is a simplified classification which is based on genesis of the deposits and geological environment. It shows the main modes of occurrence of iron ores as well as it illustrates the varied geology of iron ore deposits. Igneous ores -These iron ore deposits are formed by crystallization from liquid rock materials, either as layered type deposits that possibly are the result of crystals of heavy iron bearing minerals settling as they crystallize to...