Main Aspects of the Epigenesis Problem

Abstract

SUMMARY This paper presents the main trends in epigenetic research in the U.S.S.R. in the last years: Study of epigenetic zonality in thick series of sedimentary rocks of various ages and tectonic regions, (zones of unaltered clay matrix, of altered clay matrix, of quartzitic structures and hydromica‐chloritic cement, and of prick‐like structures and phyllite‐like schists). Principles of stadial analysis and mineral indicators of different epigenetic stages (clay minerals, organic matter, zeolites, feldspars, sulfides). Facies of regional epigenesis connecting the main petrographic families of unaltered terrigenic rocks (quartz sandstones with kaolinitic matrix and the same composition of associated clays, acidic arkoses with hydromicaceous clays, lithoclastic sands with several matrix components and associated clays, and volcanogenic greywackes) with “related” facies of regional metamorphism. Some practical aspects of epigenesis are: for petroleum geology: maximum depth of burial according to porosity, interruption of quartz, feldspar, sphene, epidote, carbonate, biotite, and clay mineral epigenesis by oil migration; and for ore geology: (a) initial epigenesis: ore impregnation (e.g., volkonskoite in wood remains) due to intrastratal solution of heavy minerals and leaching of rock fragments; (b) deep epigenesis: e.g., galena impregnations due to release of trace elements during dissolution of rock forming minerals e.g., feldspars; and (c) metagenesis: “Alpine” veins across and along bedding, filled, e.g., with copper ores.

Clay minerals as an index of the degree of metamorphism of the carbonate and terrigenous rocks in the South Wales coalfield

“…Also, studies have shown that the increase in the grade of metamorphism of the non-organic minerals or rocks is always accompanied by progressive increase in coalrank, and that the stage of anchimetamorphism is usually associated with anthracites (Kisch, , 1969Ammosov, 1970;Kossovskaya & Shutov, 1970;Kaplan, 1971 ;Grechukhin, 1972;Weber, 1972;Bostick, 1974;Castano & Sparks, 1974;Kisch, 1974Kisch, , 1975Castano, 1975;Vassoyevich et al, 1976).…”

Zeolite mineralization of reservoir rocks in the north of Western Siberia: lithological and geophysical aspects and exploitation characteristics

“…приводит к растрескиванию минерала по плоскостям спайности, а иногда и рассыпанию в порошок. В связи с этим подразумевается, что структура порового пространства цеолитизированных коллекторов в пластовых условиях существенно отличается от структуры в экстрагированных образцах, поступающих на лабораторные исследования керна [9,10].…”

On the delimitation of the carbonate burial realm

“…Very low-grade (anchi) metamorphism Low-grade metamorphism Kossovskaja and Shutov (1970) Initial epigenesis…”

“…Choquette and Pray (1970) use the terms ‘eogenesis’ (early), ‘mesogenesis’ (middle) and ‘telegenesis’ (late). The terms ‘epigenesis’, ‘metagenesis’ and ‘catagenesis’ (or katagenesis) were originally used by Russian workers (Kossovskaja & Shutov, 1970; Veselovs, 1967). In their terminology, the term epigenesis is the equivalent of the label diagenesis (Table 1, Figure 1A).…”