Известия Томского политехнического университета: Инжиниринг георесурсов (Mar 2018)
Glauconite from upper cretaceous formations of Varvarinskoe deposit (Turgay depression, Northern Kazakhstan)
Abstract
Glauconite is the dioctahedral micaceous mineral with a high Fe content and structure of 2:1 layers linked by interlayer K cations. Wide distribution among marine sedimentary deposits and specific structural and chemical features of glauconites attract considerable attention of scientists both for paleogeographic reconstructions and for practical economical applications. The main aim of the study is a detailed investigation of mineralogical and structural-chemical characteristics of glauconite from the Upper Cretaceous formations of the Varvarinskoe deposit to determine origin of glauconite and to obtain initial information about possibilities of its practical applications. The methods: scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, X-ray fluorescence analysis, optical microscopy and petrographic analysis. As a result of this investigation the following main conclusions were obtained. The formation of glauconite-quartz sandstones and sands occurred in coastal facies near the terrigenous input in dysoxic and anoxic conditions. The studied rocks mainly consist of glauconite (9,2...9,4 %) and terrigenous quartz (82,6...86,8 %). Glauconite is characterized by the following chemical composition (%): K2O - 6,73…8,89, SiO2 - 49,61…55,99, Fe2O3(total) - 19,36…26,85, MgO - 3,26…4,91, Al2O3 - 3,90…7,31. The total content of adsorption and crystallization water is 3,46 and 7,12 %, respectively, according to the thermal analysis. Glauconite is evolved and highly evolved by degree of maturity. Glauconite is in situ origin. The glauconitization proceeded along the organic substrate according to the «verdissement» model due to chemical diffusion and transformation of the initial ferrous and ferrous-aluminum smectite, as evidenced by the structural and crystallochemical characteristics of glauconite. The studied structural and chemical characteristics of glauconite of the Varvarinskoe deposit indicate the possibility of its practical applications.
