3. Contact metamorphism zones can be a few centimeters to several kilometers, especially around large plutons. The metamorphic structures are determined by definite mechanical conditions and also by recrystallisation. Foliation in geology refers to repetitive layering in metamorphic rocks. 41 0 obj<>stream
Metamorphic zones • Systematic variations in the mineralogy and often the textures of metamorphic rocks are related to the variations in the degree of metamorphism • Changes in mineralogy occur from regions of low-grade metamorphism to regions of high-grade metamorphism • Certain minerals, index minerals, are good indicators of the metamorphic conditions in which they form • … Sedimentary rocks. In geology this refers to the changes in mineral assemblage and texture that result from subjecting a rock to pressures and temperatures different from those under which the rock originally formed. Rock, in geology, naturally occurring and coherent aggregate of one or more minerals. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. Know: Apply. Compaction 5. cementation. 3. The structures of the metamorphic rocks are: (i) Slaty structure, (ii) Schistose structure, (iii) Gneissose structure, and (iv) Granulose structure. This metamorphic rock forms in two different ways. 0000003550 00000 n
IV Fabrics: grain-scale structure (metamorphic rocks & igneous rocks) A Foliation: preferred alignment of minerals (e.g., mica) parallel to a plane; B Lineation: preferred alignment of minerals parallel to a line; GG 612 February 28, 2008 6. ]>������?�!�KS�^\�P��� ϨN�٬�/�� ��f�'� � }p�����s(���.�b6��� • Suggest possible parents for a given metamorphic rock. There appears to be in certain places a cross-cutting relationship where Highland Series structures cut the Vijayan structures. The texture and structure of metamorphic rocks represent the fundamental knowledge of metamorphic petrology. Chapter PDF Available Geology, Structural, Metamorphic and Mineralization Studies Along the Mandi-Kullu-Manali-Rohtang Section of Himachal Pradesh, NW-India December 2020 Weathering, 2. Metamorphic Rocks Presentation - Free download as Powerpoint Presentation (.ppt / .pptx), PDF File (.pdf), Text File (.txt) or view presentation slides online. Ideas. Foliation in geology refers to repetitive layering in metamorphic rocks. Metamorphic - rock formed when heat and/or pressure deep within the planet changes the mineral composition and grain size of existing rocks. 0000188064 00000 n
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• Facies concept developed by Eskola (Norway, 1915) to compare metamorphic rocks from different areas. Metamorphic rocks that are classified according to texture include slate, phyllite, schist, and gneiss. Most metamorphic processes take place deep underground, inside the earth’s crust. • Look at several protoliths to determine facies. Some rocks, such as limestone are made of minerals that are not flat or elongate. Based on the mineral assemblage present in the rock one can often estimate the approximate bulk chemical composition of the rock. This is the effect of erosion over rocks formed at a depth. ����6UW;}������- |�[�q!Ө��P���9����Ot(�oV9�|�|bu �2�E@���z��l�Q�,o���3�3p4���T��g��S�3?�g��2�Ae"��i?���X�Ŭ�Üw���/������ƥS�(w�V��yܟ��N! Rocks can be classified in to three main groups - igneous, sedimentary and metamorphic. %%EOF
Metapelites are probably the most distinguished family of metamorphic rocks. In that case, you will end up with the entire rock having minerals aligned in a certain direction, all by the breaking of bonds between atoms in a mineral, and reforming (recrystallizing) in the lower pressure areas among the grains or crystals in the rock. A metamorphic rock used to be some other type of rock, but it was changed inside the Earth to become a new type of rock. 0000003246 00000 n
INTRODUCTION 1.1 You might have heard us define structure in rocks as rock geometry on a scale much larger than grains.This is a singularly unilluminating definition, be-cause it doesn't conjure up in the mind of the uninitiated any of the great variety of interesting and significant geometries that get produced by the physical, chemical, In geology this refers to the changes in mineral assemblage and texture that result from subjecting a rock to pressures and temperatures different from those under which the rock originally formed. Metamorphic rock - Metamorphic rock - Structural features: Metamorphic rocks are often intimately related to large-scale (kilometres of tens of kilometres) structural features of Earth. Metamorphic rocks are the third great class of rocks. These agents can act and interact in an almost infinite variety of ways. Metamorphic rock, any rock that results from the alteration of preexisting rocks in response to changing conditions, such as variations in temperature, pressure, and mechanical stress, and the addition or subtraction of chemical components. v��ȕ�����(K� (ͮj�g�Kx G*. 2. C. Metamorphic Rock Names Field names for metamorphic rocks are less logical, simple, and consistent than names for other rock types. Regional means that the metamorphic conditions occur over large geographic areas and include differential (or shearing) stresses, which help to form the layered structure known as foliation. • Facies represent specific temperature - pressure regimes. GG 612 February 28, 2008 7. 0000001037 00000 n
Relict (remnant of the original structure) and crystalloblastic (metamoiphic crystalline structure) structures may exist side by side. In result, pre existing rocks are reformed intonew rocksknownasMetamorphicRocks. Random orientation Of minerals Preferred orientation Of minerals 37. 0000001174 00000 n
A foliated rock holds a parallel alignment of certain minerals that are repetitively layered. Such features include folds, nappes, and faults with a wide variety of geometries. 19 23
[Adobe Acrobat PDF 277 KB] K1. The rocks that are formed will depend on the country rock that the intrusion invades. They occur when sedimentary and igneous rocks become changed, or metamorphosed, by conditions underground. • It leads to formation of Q-M domains. As per Wikipedia, “”Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means “change in form””.The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars), causing profound physical and/or chemical change. a. Gneissose structure • Either a poorly-developed schistosity or segregated into layers by metamorphic processes • Gneissose rocks are generally coarse grained . The rock possessing slaty cleavage has a unique property of splitting into thin sheets. • Look at several protoliths to determine facies. • Distinguish between foliated and non- foliated metamorphic rocks. (*���(%�8H����8c�-��
f�ԉd�9�@6_IjH��9���(3=�D����R�1%? Exposure to these extreme conditions has altered the mineralogy, texture, and chemical compositionof the rocks. A1. This gives the rock a layered or banded appearance called foliation. h�bbd```b``�
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A2. Petrography is a subfield of Petrology. Lineation is one of the most significant fabric elements and it should be included in all complete structure maps. Metamorphism and Metamorphic Rocks Definition of Metamorphism The word "Metamorphism" comes from the Greek: meta = after, morph = form, so metamorphism means the after form. Petrography - The branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. The four main agents that metamorphose rocks are heat, pressure, fluids, and strain. The attitude of a linear structure … endstream
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In this chapter the methods used to draw field sketches of complex structures in metamorphic rocks are described. … structures in rocks, cause the formation of new minerals, and produce the coarsening of texture and layering of minerals. The original rock … Often metamorphic rocks contain complicated folds and cleavages that make them difficult to record in field sketches and to interpret. • Migrate to low shear area, where porphyroblasts form. Metamorphic Differentiation • Rocks are inhomogeneous • So is the deformation in rocks experiencing shear • Separation of High and low shear zones by transition zones. Abstract. )U!���$5�X�3/9�� �(�$5�j�%V*�'��&*���r" (,!��!�0b;�C��Ң2(��ɘ� � I�8/
Typical metapelites include well-known metamorphic rocks such as, for example: chlorite-kyanite-schists, staurolite-garnet micaschists, chlori-toid-garnet micaschists, kyanite-staurolite schists, biotite-garnet-cordierite gneisses, sillimanite-biotite gneisses and orthopyroxene-garnet granulites. Metamorphic Facies: All the rocks that have reached chemical equilibrium under a particular set of physical conditions. 0000000770 00000 n
Burial metamorphism is a special type of low grade metamorphism with low temperatures and pressures. PDF | On Mar 12, 2012, Romain Bousquet and others published Metamorphic structure of the Alps | Find, read and cite all the research you need on ResearchGate Exposure to these extreme conditions has altered the mineralogy, texture, and chemical compositionof the rocks. The phrase chemically reactive refers to the dissolved ions in a fluid phase that may react with minerals in a rock; these ions may take the place of some of the atoms in the mineral’s structure, which may lead to a significant change in the chemical composition of a rock. 428 0 obj
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In the first way, sandstone or chert recrystallizes resulting in a metamorphic rock under the pressures and temperatures of deep burial. lx�}�I��=u1��\��=�VrN!�F��\U��l����Rp��Dۂ���Rh�ÃO�|#����sٯ9�����c��ȃ^l~�3��ة��e;1����2�����q�㒭C�qB�*.�3�����P��-��J=*S�=+����յO�e�ѭD��^�������唁���_ ,�rZ
There are other conditions t hat form metamorphic rocks. b. Phyllite. Metamorphic rocks can be formed from igneous, sedimentary, or previous- ly metamorphosed rocks by recrystallization in the solid state. 0000001586 00000 n
Just like in igneous rocks, minerals can only form if the necessary chemical constituents are present in the rock (i.e. • Identify major minerals contained within a metamorphic rock. • Learn to identify metamorphic rocks by structure and mineralogy. They systematically change their mineralogical composition as a result of tecto-thermal events. Orientation . Primary Sedimentary Structures Major Primary Sedimentary Structures are: 1. i��3�c:L�9�]q[��)2W�e@n���-��>'�;v�,5�q/�{��;��:+��X����g�ۙvp��1���L��=|�t�� O��5&�p�QL䦙4��zZE��e��):K��1V��Q.�E�X-vCD�iqE���̗^�J>)��3�M��|G�2S *K��+;Cy[iS�Pb*T�i�T�����Yf�Ymn3w0]��j������PǓ���=��ܻ�\�.���Y�{Q>����=\�M���X��%��h��C4����i
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�.��5��tH�y�0LI�E1Qi�L1L�����(���D��HatH~�iV8R�:��2���l��#�N�J��s8�vy�m�@!���Q�/4P�Y���!���)M\�{�O�����>���-���b.�5B��9�������;"��S�G���ɅM*ȟ8a��c�<0z��y�9Ç}7;+s���6d��i���ۧwj/gJ��Ą�MU� �z��fd%K�>=��z��{CcQqwC�ʹ�n������a��$�6 ��r5���t-JUe>��~���JV$3p��C�h(� The driving forces for metamorphism are changes in temperature,pressure,and compo- sition of pore fluids. {����.�`U��w�����U���\�X�M����]?��D}����,�BК���a��o@W�8�vޡ�XB�Ȕ���~��{_{���
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• Distinguish between slaty, schistose, and gneissic foliations. Metamorphic rocks are formed by the transformation of pre-existing lithologies under the influence of pressure and temperature. The geological processes that involved in the formation of sedimentary rocks are as under: 1. 0000006780 00000 n
The Vijayan rocks are mainly monotonous-homogeneous quartzofeldspatihic gneisses that suggests an infracrustal metamorphic-plutonic parentage in contrast to the supracrustal meta-sedimentary nature of the Highland Series. The nomenclature of metamorphic rocks is classified according to various criteria, especially texture, composition, and P–T conditions of metamorphism. endstream
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Metamorphic rock classifications include specific rock types based upon crystal size, diagnostic accessory minerals, mineralogical composition in increasing amounts greater than 15 percent, and structure. Metamorphic petrology is the study of the solid-state chemical changes that take place in minerals and rock. The three major classes of rock are igneous, sedimentary, and metamorphic rock. perpendicular to the direction of maximum pressure or stress). Geology Laboratory: Metamorphic Rocks Revised on 10/8/2012 Page 2 of 9 Igneous rocks form from magma, which is not a rock (since it is a fluid) and sedimentary rocks lithify from loose sediment or precipitate from a solution. pencil tectonites). Yet, this empirical rule may be in need of revision. �r��H�yG����� A lithology field in a geoscience database is a place for classification of the constituents used to describe bodies of rock. Sedimentary rocks. STRUCTURES IN METAMORPHIC ROCKS Foliation: when platy, lamellar or flaky minerals (e.g.. sheet silicate minerals the micas: biotite and muscovite, chlorite, talc, and serpentine), occurring in rock orient themselves parallel to one another (i.e. Petrography - The branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. h��W�n�6�>&(RR�HI�"�/ɮ�:�FiS���bs��dH the concept of silica saturation and alumina saturation applies to metamorphic rocks as well). The geological processes that involved in the formation of sedimentary rocks are as under: 1. The main difference is, of course, terminology. ;~��� ]'g���d���D��ky(v[��d(��g�uM��ੌKH+6���O���:E�6�+��[g�F~Nw\�
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Suggest possible parents for a given metamorphic rock under the pressures and temperatures of deep burial structure: the structure.