This course is a basic to advance introduction for the post graduate students in petrology. Geology is plagued by the problem of in accessibility; they see only the tiny fraction of the rocks that composes the Earth. During the processes of uplift and the erosion on the surface, but their exact place of origin is vague. As a result, a large proportion of our information about earth is indirectly coming from analysis of subsurface materials, geophysical studies, or experiments conducted at variable temperature and pressure. Metamorphic rocks are the most common rock type on Earth, and their study allows us to put constraints on the pressure, stress and temperature conditions in the crust and mantle, and on the bulk composition in these environments. Metamorphism affects rocks in three ways; it changes their mineralogy, it changes their shape, and it can change their composition.
In this course we will look at the processes behind metamorphism, the description, and classification of metamorphic rocks, and how to extract information from metamorphic rocks and minerals to determine the conditions under which they formed. Metamorphism means change in form. In geology the term is used to refer to a solid-state recrystallization of earlier igneous, sedimentary, or metamorphic rocks. Such study includes description and classification of rocks as well as interpretation of their origin. Petrology is subdivided into three major rock types: Igneous, sedimentary, and metamorphic. Igneous and metamorphic petrology are combined, due to the similarity of approach and principle involved during their formation. As per the syllabus of UGC based on CBCS, I henceforth use the term metamorphic petrology and thermodynamics is to study metamorphic rocks and their processes of formation within one single paper as basic to advance for the post graduate students.
This course deals with the naturally occurring rocks in field as well as laboratory analysis data that provide sufficient information how they occur in the nature. It gives idea of modern petrological theories which are widely accepted for their origin. The course emphasis the petrology which cover the Geology & its Perspective, Career in geology, Structure and classification of the silicate minerals along with Definition of metamorphism, Factors controlling metamorphism, variables / agents and types / kinds of metamorphism – contact, regional, fault zone metamorphism, impact metamorphism. Types and classification based on metamorphic agent. Regional metamorphism and paired metamorphic belts with reference to the theory of plate tectonics. Mineralogical phase rule for closed and open systems, nature of metamorphic reactions, concept and classification of metamorphic facies and facies series, Introduction to ultrahigh temperature and ultrahigh pressure metamorphism. Metamorphic zones, isograde and reaction isograde, Concept of classification of metamorphic facies, facies-series and grade, structure and textures of metamorphic rocks; chemographic projection, graphical representation of metamorphic minerals assemblages; ACF, AKF, AFM and others diagram.
Description of each facies of low, medium to high pressure and very high pressure with special reference to characteristic minerals, subdivision into zones / subfacies, mineral assemblages; Metamorphic reactions and pressure – temperature conditions of metamorphism. Regional metamorphism of pelitic, calcareous, basic, and ultra basic rocks and thermal metamorphism of calcareous and pelitic rocks. Schreinemakers rule and construction of petrogenetic grids, metamorphic differentiation, anatexis and origin of migmatites in the light of experimental studies. Laws of thermodynamics; Gibb’s free energy, entropy, ∆G of metamorphic reactions (solid-solid and dehydration reactions); Geothermobarometry and PT paths. Petrographic details of some important metamorphic rocks such as - slate, phyllite, schists, gneiss, quartzite, marble, charnockite, leptynite, khnodalite etc.
The course definitely provides better understanding to students for the processes and principles involved during the origin and evolution of the metamorphic rocks. The course contains video, text, assignment; quiz, case studies, references etc and I hope it will be useful for the geology students within and outside India. Last but not least, I highly accept any comments, questions, or suggestion for the improvement of this course.