What is the protolith of mylonite?
Mylonites usually have a quartzo-feldspathic protolith (like granite or gneiss) although they may originate from any rock type.
What is the protolith of marble?
Limestone
A protolith is a parent rock in metamorphism; what the rock is before it undergoes metamorphism. Limestone is a protolith for marble.
What is the parent rock of mylonite?
Metamorphic rocks The mylonites can be formed by converting many kinds of rocks, particularly those predominantly composed of quartz, feldspar, calcite, dolomite, sericite, and chlorite. The likely parent rocks are sandstone, granite, granodiorite, diorite, limestone, marble, and dolostone (Fig. 7.7).
What is the texture of mylonite?
They are extremely fine-grained, but mineral fragments of the parent rock can be seen under the microscope. Most mylonites are laminated, the layers formed by different grain sizes of deformed material. These are rocks in which the texture is the result of ductile shearing or mechanical shattering of grains.
What is phyllite rock?
Phyllite is a foliated metamorphic rock rich in tiny sheets of sericite mica. Phyllite is a durable and soft rock and used as decorative aggregates, floor tiles, and as exterior building, or facing stone. The other uses include cemetery markers, commemorative tablets, creative artwork, and writing slates.
What is Corona texture?
Corona texture: several concentric layers of one or more minerals completely encircling an older phase. The layers (which range from one to five in number) represent a sequence of reactions that have taken place (none to completion) to replace the mineral in the core or center of the corona.
What is migmatite parent rock?
A migmatite is a metamorphic rock formed by anatexis that is generally heterogeneous and preserves evidence of partial melting at the microscopic to macroscopic scale. Migmatites represent the transition from metamorphic to igneous rocks in the rock cycle.
What is Migmatic?
migmatite, in geology, rock composed of a metamorphic (altered) host material that is streaked or veined with granite rock; the name means “mixed rock.” Such rocks are usually gneissic (banded) and felsic rather than mafic in composition; they may occur on a regional scale in areas of high-grade metamorphism. migmatite.
What is the protolith of quartzite?
Quartzite is a metamorphic rock from the protolith sandstone. In quartzites, the quartz grains from the original sandstone are enlarged and interlocked by recrystallization.
What is the protolith of phyllite?
The protolith (or parent rock) for phyllite is shale or pelite, or slate, which in turn came from a shale protolith. Its constituent platy minerals are larger than those in slate but are not visible with the naked eye.
What is Symplectite texture?
A symplectite (or symplektite) is a material texture: a micrometre-scale or submicrometre-scale intergrowth of two or more crystals. Symplectites form from the breakdown of unstable phases, and may be composed of minerals, ceramics, or metals.
What is exsolution lamellae?
[¦ek·sə′lü·shən lə′mel·ē] (geology) Layers of sedimentary rock that solidify from solution by either precipitation or secretion.
What is the protolith of migmatite?
Other migmatite hypotheses Such granites derived from sedimentary rock protoliths would be termed S-type granite, are typically potassic, sometimes containing leucite, and would be termed adamellite, granite and syenite. Volcanic equivalents would be rhyolite and rhyodacite.
What type of protolith is found in a mylonite?
Mylonites usually have a quartzo-feldspathic protolith (like granite or gneiss) although they may originate from any rock type. The temperature has to be at least 250-300°C for the mylonitization to take place (for quartzo-feldspathic rock).
What is the difference between mylonitic and protomylonite?
Mylonite. In this way mylonitic rocks resemble gneiss and are distinct from schist, slate, and phyllite which tend to break along the foliation plane. 1 The rock is called protomylonite if the porphyroclasts make up more than half of the rock volume and ultramylonite if almost all the porphyroclasts are gone (less than 10% have survived).
What type of metamorphic rock is mylonite?
Mylonite is a foliated metamorphic rock that is composed of intensely flattened minerals in a fine-grained streaked matrix. Mylonites form deep in the crust where temperature and pressure are high enough for the rocks to deform plastically (ductile deformation).
What is the origin of the word mylonite?
The word mylonite derives from the Greek “μυλων” (a mill) since the original opinion on these rocks was that they formed by brittle milling of the rock (Lapworth 1885). However, present use of the word mylonite refers to rocks dominantly deformed by ductile flow, while brittle deformation may play a minor role.
What is the protolith of a metamorphic rock?
A protolith (from Ancient Greek πρωτο (prōto) ‘first’, and λίθος (líthos) ‘stone’) is the original, unmetamorphosed rock from which a given metamorphic rock is formed. For example, the protolith of a slate is a shale or mudstone.
What rock is the most common protolith of phyllite?
Composition of Phyllite Phyllite is composed mainly of tiny grains of mica minerals such as muscovite, or sericite. Fine-grained quartz and feldspar are often abundant in phyllite.
What is the parent rock of metamorphic phyllite?
Phyllite
| Type | Metamorphic Rock |
|---|---|
| Miscellaneous | Foliation surface has a satiny sheen and crinkled appearance |
| Metamorphic Type | Regional |
| Metamorphic Grade | Low Grade (Higher than Slate) |
| Parent Rock | Shale or Mudstone |
The word comes from the Greek phyllon, meaning “leaf”. The protolith (or parent rock) for phyllite is shale or pelite, or slate, which in turn came from a shale protolith. Its constituent platy minerals are larger than those in slate but are not visible with the naked eye.
How do you find protolith?
In low grade metamorphic rocks, original textures are often preserved allowing one to determine the likely protolith. As the grade of metamorphism increases, original textures are replaced with metamorphic textures and other clues, such as bulk chemical composition of the rock, are used to determine the protolith.
What is the protolith of gneiss?
The protolith of gneiss may be an igneous rock, in this case it is called an orthogneiss. It forms probably because of shear in vicous granitic magma. Paragneiss is a variety with a sedimentary protolith. Even in the latter case, gneissic banding has nothing to do with original layering of sedimentary rocks.
What is the Protolith of Migmatite?
What rocks are protolith?
Protoliths are usually granites, rhyolites, or arkose sandstones and metamorphism results in gneisses containing an abundance of quartz, feldspar, and biotite.