KATAGENE DISCHARGE ZONES OF SUBSURFACE WATERS OF HYDROCARBON-BEARING BASINS AND SEDIMENTARY ORE GENESIS

Areas of discharge of subsurface waters of hydrocarbon-bearing basins (HCB) are called katagene discharge zones. The volumes of such waters - katagene and sedimentogene, displaced on the way to discharge - are tremendous. The discharge has usually the character of pulsed kicks. The relation of a number of large and rather large sedimentary iron and manganese deposits to zones of the open katagene discharge of subsurface waters of HCB is demonstrated. Differences in metallogeny of these zones are governed mainly by various conditions of upward migration of subsurface waters. Sedimentary iron deposits, often accompanied by low-grade manganese ores, are formed due to the lack of conditions for a significant deposition of epigenetic iron minerals (sulphides and carbonates) in zones of the katagene discharge during migration. Katagene discharge zones are associated, in such cases, with deep penetrating fault structures located predominantly at marginal parts of HCB. With examples of the largest sedimentary manganese deposits of the Southern Ukrainian basin, in the world it is shown that, with the presence of elongated gentle monoclinal slopes in the marginal parts of HCB, the solutions, rising along the permeable levels, may be practically completely relieved of iron because of the formation of the epigenetic impregnation of its minerals. ore-localizing katagene discharge zones are associated in these cases with water saturated erosion junctions of such levels near the day surface. Here, the distance of the lateral migration of ascending solutions outside the HCB borders may constitute the first hundreds of km. Deposits of oolitic iron ores are divided into two groups of different sources of ore-forming solutions and of metal in them: katagene-sedimentary, formed by ascending subsurface waters of HCB (Western Siberian, Kerchensko-Tamanskii, Priaral'skii, etc.), and traditional hypergene, formed by descending surface and ground waters redepositing metal of weathering crusts (Orsko-Khalilovskii, Malkinskii, etc.). Distribution areas and metal reserves of the katagene-sedimentary deposits of oolitic iron ores are many-hundred times greater than those of supergene ones. The only evidence of a relation of ores to the hypergene group may reveal the past development of the lateritic weathering. It is necessary to take into account the factors determining the formation and the location of the katagene discharge zones of subsurface waters during the preparation of genetic models and criteria of exploration and prognosis of deposits of HCB. The localization of mineral deposits in them is not limited by situations of the open subaqual discharge and the formation of sedimentary deposits of iron and manganese.