High Strain Metamorphic Textures Shallow fault zone • Brittle behavior of rocks • Cataclasis dominating process • Broken, crushed rotated grains dominate in fault breccia Intermediate Depth • Pressure increases • Deformation increases • Cataclasis continues to dominate 17. Metamorphic textures High-strain rock textures High strain rock textures Concentrate on cataclastic > ductile (shallower) k k b d h Break, crack, bend, crush, rotate Slip and shredding of Slip and shredding of phyllosilicates Clasts- broken remnants Porphyroclast- larger remnant in finer crush matrix Mortar texture Ribbons Pseudotachylite Contact metamorphism is the name given to the changes that take place when magma is injected in the surrounding solid rock (country rock). Some fine-grained metamorphic rocks, e.g. The transition between ductile-dominated deformation and brittle fracturing depends on rocks composition, geothermal gradient, bulk strain rate, fluid and metamorphics grade. (2006, 2011), and Jessup et al. Metamorphism occurs when solid rock changes in composition and/or texture without the mineral crystals melting, which is how igneous rock is generated. 78) 79)Uniform high pressure metamorphism of a quartz-rich sediment will generate a foliated rock like slate, phyllite or schist. (A) Antiperthite with K-feldspar (Kfs) exsolution lamellae in two directions from a ~ 1.95 Ga high … (B) Thermal (constructive) processes due to the input of heat. Mylonite is very high-grade, higher grade than Gneiss, (Fossen, 2016). • The texture of a metamorphic rock depends on the metamorphic … A metamorphic rock forms when igneous, sedimentary, or older metamorphic rocks are subjected to heat, pressure, and strain that result in changes of their texture and mineral assemblage. These fold belts Dynamic metamorphism involves high shear stress, high pressure, high strain, high fluid partial pressure and variable temperature. Syn-kinematic crystals Figure 23-40. Source: Redrawn from Passchier and Trouw 1996. Dynamic metamorphism involves high shear stress, high pressure, high strain, high fluid partial pressure and variable temperature. deposits of copper, gold and marble. These form by generally low mountain belts. Marble: Metamorphosed limestone or dolostone. (2006, 2008).Insets show alignment of inverted metamorphic isograds in the MCT zone along the base and … Question 11 of 25 4.0/ 4.0 Points The core of a mountain range that formed during regional metamorphism would contain a _____ metamorphic facies. The temperature has a first-order effect on the rheologic properties of materials. recrystallising and converting to marble as they approach a dolerite / Comprising of equigranular, interlocking, randonly orientated platy, tabular, prismatic or elongate minerals. Bibliography • Bucher, K., & Grapes, R. (2011). Lower Paleozoic, Sierra El Peñón, ArgentinImage Credit: MBG, Subhorizontal shear zones devolped in high-grade amphibolite facies. Ore Geology Reviews, 6 ( 1991 ) 475-483 475 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands The importance of deformation experiments on minerals for the interpretation of metamorphic ore textures Heinrich Siemes, Christa Hennig-Michaeli and Luane Martens Institut f~r Mineralogie und Lagerstiittenlehre R WTH Aachen, Wiillnerstr. The texture arises to minimise surface energy in a rock with elongate crystals and is thus similar to a granoblastic texture. (2003, 2006), Law et al. Deviatoric stress, strain rate and temperature are the most important variables in this type of metamorphism. (1986) J. Metam. Lower Paleozoic, Sierra El Peñón, Argentin, Subhorizontal shear zones devolped in high-grade amphibolite facies. It is sometimes also called cataclastic metamorphism. Note that the width of the shear zone increases with depth as the shear becomes more ductile. https://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/metamorphic.html, https://geomaps.wr.usgs.gov/parks/rxmin/rock3.html, http://serc.carleton.edu/research_education/equilibria/classicalthermobarometry.html, http://csmres.jmu.edu/geollab/Fichter/MetaRx/Barrovian.html, https://opentextbc.ca/geology/chapter/7-3-plate-tectonics-and-metamorphism/, http://www.geo.fu-berlin.de/en/v/geolearning/mountain_building/metamorphism/contact_metamorphism/index.html, https://australianmuseum.net.au/types-of-metamorphism. High-strain metamorphism is typically produced along fault and shear zones in the upper and middle crust. For this reason, most attempts to link regional metamorphism to plate tectonics setting have concentrated on regions where plates converge. 77)High-grade, regional metamorphism produces significant and recognizable changes in the textures and mineral compositions of rocks. 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