Metamorphic rocks tutorial - Carleton Collegedmaxbauer/Metamorphic_rocks... · 2019-09-13 ·...
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METAMORPHIC ROCKS Metamorphic rocks, in the most basic sense, form through the alteration of other rocks (igneous and sedimen- tary). In various settings on Earth, frequently associated with tectonic environments/processes we will talk (some) about, rocks are buried deeply (or not-so deeply) below the Earth’s surface where they are exposed to very high temperatures and pressures. In many cases, fluids are also involved in metamorphic processes - but the important changes occur in the solid state through physical and chemical processes like changes to the mineral’s crystal lattice, atom substitutions, and various types of ‘creep’ processes we won’t talk much about. BUT - one important thing to note is that the temperature and pressures are not associated with melt- ing. If you melt pre-existing rocks you end up back as magma that we think about leading to the formation of igneous rocks. Please use the information below to familiarize yourself with some common metamorphic rocks, minerals, and processes. Rock Name Texture Parent Rock Grain Size Foliated Slate Phyllite Schist Gneiss very fine fine medium to coarse medium to coarse shale mudstone siltstone slate phyllite phyllite granite Non Foliated Marble Quartzite medium to coarse medium to coarse limestone sandstone TABLE 1. CLASSIFICATION OF COMMON METAMORPHIC ROCKS KEY TERMS AND CONCEPTS: Porphyroblast: a large metamorphic mineral in a finer grained matrix of a metamorphic rock. Typical exam- ples of porphyroblastic minerals include garnet, staurolite, and kyanite. Foliation: alignment of mineral grains in a metamorphic rock that give rise to laminations/layers of minerals. In the slate-phyllite-schist example above, foliation develops as mica minerals form through recrystalization of original clay minerals. Slate is an example of a ‘low-grade’ metamorphic rock that begins a sequence of slate -> phyllite -> schist -> gneiss with increasing metamorphic ‘grade’. Gneiss sometimes is the end product of this sequence, but is often simply a ‘high-grade’ metamorphic product of granite or some other igneous rock.
Transcript of Metamorphic rocks tutorial - Carleton Collegedmaxbauer/Metamorphic_rocks... · 2019-09-13 ·...
METAMORPHIC ROCKSMetamorphic rocks, in the most basic sense, form through the alteration of other rocks (igneous and sedimen-tary). In various settings on Earth, frequently associated with tectonic environments/processes we will talk (some) about, rocks are buried deeply (or not-so deeply) below the Earth’s surface where they are exposed to very high temperatures and pressures. In many cases, fluids are also involved in metamorphic processes - but the important changes occur in the solid state through physical and chemical processes like changes to the mineral’s crystal lattice, atom substitutions, and various types of ‘creep’ processes we won’t talk much about. BUT - one important thing to note is that the temperature and pressures are not associated with melt-ing. If you melt pre-existing rocks you end up back as magma that we think about leading to the formation of igneous rocks.
Please use the information below to familiarize yourself with some common metamorphic rocks, minerals, and processes.
Rock Name Texture Parent RockGrain Size
Foliated
Slate
Phyllite
Schist
Gneiss
very fine
fine
medium to coarse
medium to coarse
shalemudstonesiltstone
slate
phyllite
phyllitegranite
NonFoliated
Marble
Quartzite
medium to coarse
medium to coarse
limestone
sandstone
TABLE 1. CLASSIFICATION OF COMMON METAMORPHIC ROCKS
KEY TERMS AND CONCEPTS:Porphyroblast: a large metamorphic mineral in a finer grained matrix of a metamorphic rock. Typical exam-ples of porphyroblastic minerals include garnet, staurolite, and kyanite.
Foliation: alignment of mineral grains in a metamorphic rock that give rise to laminations/layers of minerals. In the slate-phyllite-schist example above, foliation develops as mica minerals form through recrystalization of original clay minerals.
Slate is an example of a ‘low-grade’ metamorphic rock that begins a sequence of slate -> phyllite -> schist -> gneiss with increasing metamorphic ‘grade’. Gneiss sometimes is the end product of this sequence, but is often simply a ‘high-grade’ metamorphic product of granite or some other igneous rock.
