the tectonic setting for magnesium fe skarns tends to be the continental margin. the host rocks tend to be granodiorite to granite associated with intruding dolomite and dolomitic sedimentary rocks. magnetite is the principal ore in these types of skarn deposits which its grade yields from 40 to 60 %. chalcopyrite, bornite and pyrite are the .
the bushveld igneous complex is a layered mafic intrusion lmi with well-defined ore bodies of stratiform chromitite layers concentrated with the so-called critical zone; these are referred to as reefs. the three main reef deposits are the merensky reef, ug-2 reef, and the platreef.
metasomatism from the greek μετά change and σῶμα body is the chemical alteration of a rock by hydrothermal and other fluids. it is the replacement of one rock by another of different mineralogical and chemical composition. the minerals which compose the rocks are dissolved and new mineral formations are deposited in their place. .
varieties include kidney ore, martite pseudomorphs after magnetite , iron rose and specularite specular hematite . while these forms vary, they all have a rust-red streak. hematite is harder than pure iron, but much more brittle. maghemite is a hematite- and magnetite-related oxide mineral.
occurrence. magnesite occurs as veins in and an alteration product of ultramafic rocks, serpentinite and other magnesium rich rock types in both contact and regional metamorphic terrains. these magnesites are often cryptocrystalline and contain silica in the form of opal or chert.. magnesite is also present within the regolith above ultramafic rocks as a secondary carbonate within soil and .
the intrusion has exercised also a metamorphic influence upon the deposits shown by the abundance of garnet and horneblende that often replace the magnetite almost completely. well-developed titanite crystals of unusual size are found in the contact zone. the analysis taken below from putnams report, gives the composition of the jayville ore. it was made from a sample of 500 tons mined in 1880 .
ore deposits formed by lateral secretion are formed by metamorphic reactions during shearing, which liberate mineral constituents such as quartz, sulfides, gold, carbonates, and oxides from deforming rocks, and focus these constituents into zones of reduced pressure or dilation such as faults. this may occur without much hydrothermal fluid flow .
anorthosite / æ n ˈ ɔːr θ ə s aɪ t / is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar 90–100% , with a minimal mafic component 0–10% . pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.. anorthosites are of enormous geologic interest, because it is still not fully understood how they form.
kursk magnetic anomaly russian: курская магнитная аномалия is a territory rich in iron ores located within the kursk, belgorod, and voronezh oblasts in russia, and constitutes a significant part of the central chernozyom region. the kursk magnetic anomaly is recognized as the largest magnetic anomaly on earth.
in geology, a redox buffer is an assemblage of minerals or compounds that constrains oxygen fugacity as a function of temperature. knowledge of the redox conditions or equivalently, oxygen fugacities at which a rock forms and evolves can be important for interpreting the rock history. iron, sulfur, and manganese are three of the relatively abundant elements in the earth's crust that occur in .
chromite is found as orthocumulate lenses of chromitite in peridotite from the earth's mantle. it also occurs in layered ultramafic intrusive rocks. in addition, it is found in metamorphic rocks such as some serpentinites. ore deposits of chromite form as early magmatic differentiates. it is commonly associated with olivine, magnetite .
chromite is found as orthocumulate lenses of chromitite in peridotite from the earth's mantle.it also occurs in layered ultramafic intrusive rocks. in addition, it is found in metamorphic rocks such as some serpentinites. ore deposits of chromite form as early magmatic differentiates. it is commonly associated with olivine, magnetite, serpentine, and corundum.