ABOUT USE OF STANDARD KIMBERLITE PIPES MODELS

 Zinchuk N.N.

West-Yakutian Scientific Center of RS (Y) AS, Mirny, Russia, nnzinchuk@rambler.ru

 

     Kimberlite pipes of all diamondiferous provinces of the World are characterized by large variety of sizes, morphology, values of hearth location depth, internal structure, specific features of infilling rocks, content and composition of deep-seated (primary) minerals, as well as of the main mass of kimberlites, degree and reprocessing character of the last ones by postmagmatic solutions and in hypergene conditions, by content, morphology and physical properties of diamonds and other features. Some of the listed features of kimberlites are stipulated by occurrence of endogenous factors, and part – of exogenous. In spite of the fact that each kimberlite body represents individual, practically not repeating in nature object, there is much in common between them, which allows creating a unified model of a diamondiferous pipe for each platform. Transition of the vertical diatreme channel into a delivery dyke, specific features of kimberlite bodies with traps, as well as contingency character of the bodies’ system found reflection in the model of the Siberian platform diamondiferous pipe: main pipe – satellite– feeding and pre-pipe dykes. When constructing the model the body of kimberlites (bulging of the kimberlite dyke) has been considered, which was exposed in the section of Cambrian deposits near pipe Udachnaya by open pit, and a bedded body (original “sill”), discovered in the deposits hosting pipe International. Destroyed by erosion upper part of most pipes of Malo-Botuobinsky and Middle-Markhinsky regions (to 300 m) was reconstructed on a summarized model due to the data about poor-eroded pipes of Daldyn-Alakit and other northern regions. Terrigene-carbonate formations of Lower Paleozoic serve as hosting rocks to the explored depth of the pipes. In kimberlite diatremes of the Siberian platform one can distinguish (from down upward): root part – feeding channel in the form of a dyke body; б) volcanic (vertical) channel; в) bellmouth (cone-like expansion), crowned by ring bank in not eroded apparatus. Each of these parts of the pipes is composed by rocks having some definite material and structural-textural features, creating peculiar vertical zonality of primary diamond deposits. Kimberlite pipes on East-European platform (EEP) are characterized by many specific properties, distinguishing them from classic kimberlites of the Siberian and African platforms. The hosting rocks of these pipes – monotonic alternate poorly cemented mudstones, siltstones and sandstones. Majority of kimberlite EEP pipes have isometric, close to rounded shape (some are stretched in north-eastern direction), which is caused by loose character of medium, into which kimberlite magma intruded. On uppermost horizons of poorly eroded pipes within the crater thick layer of volcanogenic-sedimentary rocks of lacustrine type is developed. Rocks of the diatreme are represented by volcanic formations. Productive kimberlites of АDP belong to low-satellite type. Most of kimberlite pipes of the African platform are exposed to the day surface. The upper part of the bellmouth of pipes is often like a mushroom cap in shape, the edges of which transform into ring bank, formed by outbursts of endogenous material proper and rocks, broken through by the kimberlite column. Morphology of kimberlite bodies is diverse: kimberlite bodies and dykes are common, sills are also not rare. Broad complex of sedimentary and eruptive rocks, which affect the morphology of bodies, character of secondary alterations and chemical composition of rocks, serves as hosting rocks of African kimberlites. Most kimberlite pipes are high-satellite and their chemical composition serves as reference for this type of rocks. Carried out comparative study of kimberlites of various world platforms indicated availability of both general and distinctive features, however practically it is expedient to apply the compiled models only for a particular region. There are some general features at the level of groups of pipes, kimberlite fields, mineragenetic zones, subprovinces, allowing creating models of different rank for their effective employment during forecast-prospecting and project works on each definite platform and in their definite diamondiferous regions.