Unformatted text preview: ( FeO(OH)∙4H2O) It is never crystallized into macroscopic crystals, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms Goethite B‐Iron Carbonates • Siderite: It is composed of iron carbonate FeCO3, it is 48% iron and contains no sulfur or phosphorus. Both magnesium and manganese commonly substitute for the iron Limonite C‐Iron Silicates • Chamosite: Fe3Al2Si2O10.3H2O • Greenlite: Fe2SiO3.4H2O • Glauconite: (K,Na,Ca)1.2‐2.0(Fe+3,Al,Fe+2,Mg)4 (Si7‐7.6Al1‐ 0.4O20)(OH)4∙7H2 D‐Iron Sulphides • Pyrite: FeS2 • Marcasite: FeS2 Marcasite 11 Pyrite Glauconite Hematite Chamosite Siderite Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration 5‐Phosphate Rocks Phosphorite, phosphate rock or rock phosphate is a non‐detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of Phosphorite is at least 20% which is a large enrichment over the typical sedimentary rock content of less than 0.2%.The phosphate is present as fluorapatite typically in cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane. The dark brown to black beds has range from few centimeters to several meters in thickness. The layers contain the same textures and structures as fine grained limestones and may represent digenetic replacements of carbonate minerals by phosphates. Mineralogy: • • • • Guano: Guano It is type of phosphate rocks which is the excrement of seabirds, bats, and seals. Guano consists of ammonia, along with uric, phosphoric, oxalic, and carbonic acids, as well as some earth salts and impurities. Guano also has a high concentration of nitrates. 6‐Siliceous Sediments Fluro Apatite: Ca5(PO4)3F Carbon Hydroxyl Fluro Apatite: Ca10(PO4.CO3)6F2 Dahillite: is Carbon Hydroxyl Fluro Apatite with less than 1% Flourine Franolite: is Carbon Hydroxyl Fluro Apatite with more than 1% Flourine Phosphate The siliceous rocks are those which are dominated by silica (SiO2). They commonly form from...
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- Spring '10
- Geology, Volcano, Tephra, Volcanic Ash, Geology & Geophysics, Mahmoud Ahmed Sroor