Metamorphism is the sum of all transformations which cause a rearrangement of the elements of a rock at the atomic scale, leading to a recrystallization in the solid state (with or without a fluid phase), as a result of variations in temperature, pressure or of composition.

There are three categories of rocks- igneous, sedimentary and metamorphic. Igneous rocks have been formed by solidification of hot silicate melts known as magmas, which may be erupted at the Earth's surface as lavas from volcanoes. Sedimentary rocks form by a variety of processes at low temperatures near the surface, including the bottom of the seas and oceans. Metamorphic rocks, the third category, were originally either igneous or sedimentary, but their character has been changed by processes operating below the surface of the Earth. The constituent minerals of the rocks may be changed, or the shapes, sizes and mutual spatial relationships of the crystals may change. There are a variety of processes involved, and they are collectively described by the term metamorphism. <...>

Описаны физико-механические свойства горных пород (скорость распространения упругих воли, плотность, пористость, анизотропность и др.). детально изученные при давлении до 20 кбар и температуре до 300°С. Измерения производились на образцах глубинных магматических и метаморфических пород амфиболитовой, гран\лнтовой и эклогитовой фации метаморфизма, отобранных систематически по отдельным блокам и комплексам восточной части Балтийского щита. Изучены коллекции образцов пород с Анабарского массива, из трубок взрыва на Сибирской платформе И на Памире, из глубоких скважин на Русской платформе. Детально изучались петрохимические, петрографические и структурные особенности пород.

Работа посвящена основным проблемам геологии доальпийского основания зон Главного хребта и южного склона Большого Кавказа. Рассматриваются стратиграфия, вещественный состав, история метаморфизма и тектоническая структура комплексов пород доюрского возраста. Особое внимание уделено вопросам возраста метаморфических толщ  Главного хребта, роли изоклинальной складчатости в их структу-
ре, структурной зональности, а также стратиграфия доюрского комплекса Сванетского антиклинория и проблеме «сквозного» развитии геосинклинали южного склона. Рассматриваются роль альпийских движений в формировании структуры доюрского основания, положение в нем грани-тоидов и общие особенности развития Большого Кавказа на доальпий-ских этапах

Our knowledge of metamorphic and deformational rock fabrics has been acquired largely by studying the products of deformation in ancient fold belts. As such, our understanding of how rock fabrics form has been built up from inferences about, rather than direct observations of, processes that might have operated, and many of those inferences have proved incorrect.

Metamorphism refers lo Ihe inineni logical and structural alteration of rock к in Karth's crust, and excludes alteration at or just beneath ihe surface, such as weathering and early diagencsis. However, diagenetic changes grade into mctamorphic changes in burial meuimorphism. In face* metamor-phism may occur in several geological environments, because assemblages react to changes in temperature (T), pressure (iJ) and activities of mobile chemical components, regardless ol the geological processes responsible for the changes. For example, identical or very similar assemblages can be formed by (1) deuleric alteration in an igneous intrusion 12) wall-rock alteration around a hydro! hernia) orebody. (3) low-tempe rat lire alteration around an igneous intrusion, (4) burial metamorphism of sedimentary/volcanic successions and (5) alteration, both local and regional, in geothermal areas (Vernon. 1976f.

This volume is devoted to the memory of the Russian petrologist D.S. Korzhinskiy. The world community of geoscientists has highly valued his contributions to petrology, particularly the discovery and thermodynamic description of open systems with perfectly mobile components. Korzhinskiy's work reached this community's attention because his book Physicochemical Basis of the Analysis of the Paragenesis of Minerals (1959, Consultants Bureau, New York) was translated into English. However, in the Soviet Union D.S. Korzhinskiy is also highly regarded for his contributions to geology and study of ore deposits as well as to theoretical petrology. Stratigraphy and geology of the Precambrian Aldan shield in Eastern Siberia; origin of lapis lazuli and phlogopite deposits and iron formations; boron mineralization; genesis of skarns and general theory of metasomatic zoning; origin of granites, charnockites and anorthosites; theory of the acid-basic interaction of components in the dry silicate melts: all of these were subjects of his more than 200 papers and books. The papers in the present volume span Korzhinskiy's broad interests. These papers were selected with the aim of illustrating the progress made in physicochemical petrology since Korzhinskiy.

Igneous petrology is the study of melts (magma) and the rocks that crystallize from such melts, encompassing an understanding of the processes involved in melting and subsequent rise, evolution, crystallization, and eruption or emplacement of the eventual rocks. Origin by crystallization from a melt seems a simple enough criterion for considering a rock to be igneous.

Petrology, from the Greek words petra , meaning rock, and logos, meaning knowledge, is the study of rocks and the conditions in which they form. It includes igneous, metamorphic, and sedimentary petrology.

Processes involved in the development of igneous and metamorphic rocks involve some combination of crystal growth, solution, movement and deformation, which is expressed as changes in texture (microstructure). Recent advances in the quantification of aspects of crystalline rock textures, such as crystal size, shape, orientation and position, have opened new avenues of research that extend and complement the more dominant chemical and isotopic studies.