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1994 | Buch | 6. Auflage

Petrogenesis of Metamorphic Rocks

Complete Revision of Winkler’s Textbook

verfasst von: Professor Dr. Kurt Bucher, Professor Dr. Martin Frey

Verlag: Springer Berlin Heidelberg

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Über dieses Buch

Metamorphic rocks are one of the three classes of rocks. Seen on a global scale they constitute the dominant material of the Earth. The understanding of the petrogenesis and significance of metamorphic of geological education. rocks is, therefore, a fundamental topic There are, of course, many different possible ways to lecture on this theme. This book addresses rock metamorphism from a relatively pragmatic view point. It has been written for the senior undergrad­ uate or graduate student who needs practical knowledge of how to interpret various groups of minerals found in metamorphic rocks. The book is also of interest for the non-specialist and non-petrolo­ gist professional who is interested in learning more about the geolo­ gical messages that metamorphic mineral assemblages are sending, as well as pressure and temperature conditions of formation. The book is organized into two parts. The first part introduces the different types of metamorphism, defines some names, terms and graphs used to describe metamorphic rocks, and discusses principal aspects of metamorphic processes. Part I introduces the causes of metamorphism on various scales in time and space, and some principles of chemical reactions in rocks that accompany metamorphism, but without treating these principles in detail, and presenting the thermodynamic basis for quantitative analysis of reactions and their equilibria in metamorphism. Part I also presents concepts of metamorphic grade or intensity of metamorphism, such as the metamorphic-facies concept.

Inhaltsverzeichnis

Frontmatter

Basic Principles

Frontmatter
1. Definition, Limits and Types of Metamorphism
Abstract
The definition given below follows that given by the JUGS subcommission on the systematics of metamorphic rocks.
Kurt Bucher, Martin Frey
2. Metamorphic Rocks
Abstract
This chapter deals with the descriptive characterization of metamorphic rocks. Metamorphic rocks are derived from other rocks of igneous, sedimentary or metamorphic origin. The chemical composition of this primary material (= protolith) largely controls the chemical and mineralogical composition of metamorphic rocks. The compositional variation found in the primary material of metamorphic rocks is reviewed in Section 2.1.
Kurt Bucher, Martin Frey
3. Metamorphic Process
Abstract
Rock metamorphism is always associated with processes and changes. Meta-morphism reworks rocks in the Earth's crust and mantle. Typical effects of rock metamorphism include:
  • Minerals and mineral assemblages originally not present in the rock may form, the new mineral assemblages form at the expense of old ones, consequently older minerals may disappear [e.g. a metamorphic rock may originally contain Grt + Qtz + Sil; a metamorphic event transforms this rock into one that contains Crd (cordierite) in addition to the minerals previously present in the rock].
  • The relative abundance of minerals in a rock may systematically change and the new rock may have a different modal composition (metamorphism may increase the amount of Crd present in the rock and decrease the volume proportion of Grt + Qtz + Sil).
  • Metamorphic minerals may systematically change their composition (e.g. the XFe of Grt and Crd may simultaneously increase during metamorphism).
  • The structure of rocks in crust and mantle may be modified (e.g. randomly oriented sillimanite needles may be aligned parallel after the process).
  • The composition of the bulk rock may be altered during metamorphism by adding or removing components to or from the rock from a source/sink outside the volume of the considered rock (e.g. adding K2O dissolved in an aqueous solution to a Grt + Crd + Sill + Qtz rock may result in the formation of biotite).
Kurt Bucher, Martin Frey
4. Metamorphic Grade
Abstract
According to Turner (1981, p. 85), the term metamorphic grade or grade of metamorphism was introduced by Tilley (1924) “to signify the degree or state of metamorphism” (p. 168) and, more specifically, “the particular pressuretemperature conditions under which the rocks have arisen” (p. 167). Since reliable P-T values were not known for metamorphic rocks at that time, and since temperature was generally accepted as the most important factor of metamorphism (cf. Chap. 3), it became current usage to equate grade rather loosely with temperature. As a recent example, Winkler (1979, p. 7) suggested a broad fourfold division of the P-T field of metamorphism primarily based on temperature, which he named very low-, low-, medium-, and high-grade metamorphism. Even though Winkler noted that information on pressure should be stated as well, a subdivision of metamorphic grade with respect to pressure seemed to be less important. This is well understandable because most of his P-T diagrams were limited to P < 12 kbar, whilst the present-day P-T space of metamorphism has to be extended to much higher pressures (Fig. 1.1).
Kurt Bucher, Martin Frey

Metamorphism of Different Rock Compositions

Frontmatter
5. Metamorphism of Ultramafic Rocks
Abstract
The Earth’s mantle consists predominantly of ultramafic rocks. The mantle is, with the exception of some small anomalous regions, in the solid state. The ultramafics undergo continuous recrystallization due to large-scale convection in sub-lithosphere mantle and tectonic processes in the lithosphere and any other processes causing pressure and temperature variations in a given volume of mantle rocks (magmatism, cooling and hydration). The majority of mantle rocks, therefore, qualify as metamorphic rocks. Metamorphic ultramafic rocks build up the largest volume of rocks on a global scale.
Kurt Bucher, Martin Frey
6. Metamorphism of Dolomites and Limestones
Abstract
Sedimentary carbonate rocks consist predominantly of carbonate minerals (as the name suggests). There are two main classes of carbonate rocks, dolomites and limestones. The first one is modally dominated by dolomite [CaMg(CO3)2], the second by calcite (CaCO3). The rocks often also contain variable amounts of quartz (SiO2) in addition to the two carbonates minerals (siliceous dolomites, siliceous limestones).
Kurt Bucher, Martin Frey
7. Metamorphism of Pelitic Rocks (Metapelites)
Abstract
Metapelites are probably the most distinguished family of metamorphic rocks. Typical metapelites include well-known metamorphic rocks such as, for example: chlorite-kyanite-schists, staurolite-garnet micaschists, chloritoid-garnet micaschists, kyanite-staurolite schists, biotite-garnet-cordierite gneisses, sillimanite-biotite gneisses and orthopyroxene-garnet granulites. Many distinct metamorphic minerals are found in metapelitic rocks (e.g. staurolite, chloritoid, kyanite, andalusite, sillimanite and cordierite).
Kurt Bucher, Martin Frey
8. Metamorphism of Marls
Abstract
Marls are carbonate-bearing pelitic sediments covering a large range of comm position between “impure” carbonate rocks and “true” pelites. In the Anglo American literature, this group of sedimentary rocks is better known as argillaceous carbonate rocks, calcareous sediments, calcic pelitic rocks, or calcpelites.
Kurt Bucher, Martin Frey
9. Metamorphism of Mafic Rocks
Abstract
Metamorphic mafic rocks (e.g. mafic schists and gneisses, amphibolites) are derived from mafic igneous rocks, mainly basalts and andesites, and of lesser importance, gabbros (Chap. 2). Metamorphic assemblages found in mafic rocks are used to define the intensity of metamorphism in the metamorphic facies concept (Chap. 4).
Kurt Bucher, Martin Frey
10. Metamorphism of Granitoids
Abstract
Granitoid rocks comprise granites, alkali-feldspar granites, granodiorites and tonalites, and constitute a large portion of the continental crust. Because the main constituents — alkali-feldspar, plagioclase, quartz, biotite, muscovite, hornblende — are found over a wide range of P-T conditions, this rock group is not a very useful indicator of metamorphic grade and is therefore largely neglected in textbooks on metamorphic petrology. Unlike wet sedimentary rocks, granitoid rocks will enter the metamorphic realm in a predominantly dry state. In order to start metamorphic reactions, some hydration is necessary. The access of a water-rich fluid will be facilitated by tectonic activity. Also, in the absence of penetrative deformation, granitoid rocks retain remarkably well their original igneous structures.
Kurt Bucher, Martin Frey
Backmatter
Metadaten
Titel
Petrogenesis of Metamorphic Rocks
verfasst von
Professor Dr. Kurt Bucher
Professor Dr. Martin Frey
Copyright-Jahr
1994
Verlag
Springer Berlin Heidelberg
Electronic ISBN
978-3-662-03000-4
Print ISBN
978-3-540-57567-2
DOI
https://doi.org/10.1007/978-3-662-03000-4