INTRODUCTION, BASES OF LITHOGENESIS, General information...

INTRODUCTION

Lithology - the science of modern sediments and sedimentary rocks. Its name comes from the Greek words: cast - stone, logo - teaching. Lithology is closely connected with other sciences of the geological cycle - stratigraphy, paleontology, petrography, crystallography, mineralogy, historical geology, oil theory, geochemistry, etc. In recent years, the science of "sedimentology" has been separated from lithology and studying the conditions of modern sedimentation in a variety of physical and geographical conditions. The data of this science allow reconstructing the conditions of sedimentation in past eras.

The manual is intended to study the main regularities of the sedimentary process, favorable for the formation of hydrocarbon deposits, and includes the following sections:

• the foundations of lithogenesis - is devoted to the problems of the theory of rock formation, the identification of general regularities of the sedimentary process, post-sedimentation transformations of sedimentary rocks;

• petrography of sedimentary rocks - problems of classification, composition and genesis of sedimentary rocks are considered;

• Conditions for the formation of sedimentary sequences - a detailed description of continental, marine and transitional facies is given;

• lithology of natural reservoirs - conditions favorable for the formation and location of regional oil and gas bearing complexes, as well as the formation of natural reservoirs and traps of hydrocarbons, reservoir rocks and fluid rocks are considered. At the end of the book, a dictionary of geological terms and a list of literature are included, which includes sources used in compiling the manual, as well as publications that can be used by students for in-depth and independent work.

The author is grateful to L.V. Batretdinova for help in preparing the manual.

FOUNDATIONS OF LITHOGENESIS

General information about sedimentation and rock formation processes

Sedimentary rock is a geological body that emerged from the products of physical and chemical destruction of the lithosphere as a result of chemical deposition and life activity of organisms or both.

The appearance and change of sedimentary rocks is a series of consistent and regular processes, which include a complex of mechanical (physical), chemical and biological transformations.

The process of rock formation is called lithogenesis. The main provisions of the theory of lithogenesis are set forth in the writings of the outstanding scientist, Academician N.M. Strakhova [36].

According to his ideas, in the cycle of formation of sedimentary rocks a number of stages are singled out:

hypergenesis - the origin of the initial products for the formation of sedimentary rocks (the results of mechanical destruction, chemical decomposition of older rocks, life activity of organisms, volcanic activity);

sedimentogenesis - transport and deposition of matter; diagenesis - a set of processes of transformation of loose sediments into sedimentary rocks in the upper zone of the earth's crust.

Sedimentation conditions are determined by the climate, relief and geotectonic regime of the territory. Of these three factors, climate is most important. On the climatic basis of NM. Strakhov identified the following types of lithogenesis:

1) with the climate of humid zones, with positive temperatures for most of the year, with excess of precipitation over evaporation;

2) arid - with the climate of deserts and semi-deserts, with a deficit of moisture;

3) civil , or ice, - with the climate of the polar and highland areas.

According to the source of the initial substance NM. Strakhov singled out the fourth type of lithogenesis - effusive-sedimentary, related to the regions of past and present volcanic activity.

Currently, the concept of lithogenesis includes the stages of transformation of sedimentary rocks (Figure 1):

catagenesis - the stage of the chemical and mineralogical transformation of sedimentary rocks when they are immersed in deeper horizons of the lithosphere;

metagenesis - the stage of deep processing of sedimentary rocks under conditions of increasing pressure and temperature, preceding metamorphism.

Fig. 1. Scheme of the stages of formation and transformation of sedimentary rocks, according to RS. Bezborodov, 1989 [6]

thematic pictures

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