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Metamorphic rocks are formed when existing rock is transformed physically or chemically at elevated temperature, without actually melting to any great degree. The importance of heating in the formation of metamorphic rock was first noted by the pioneering Scottish naturalist, James Hutton , who is often described as the father of modern geology.
Metamorphic rock formed in these settings tends to shown well-developed foliation. [33] Foliation develops when a rock is being shortened along one axis during metamorphism. This causes crystals of platy minerals, such as mica and chlorite , to become rotated such that their short axes are parallel to the direction of shortening.
This diamond is a mineral from within an igneous or metamorphic rock that formed at high temperature and pressure. The rock cycle is a basic concept in geology that describes transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. Each rock type is altered when it is forced out of its ...
For a metapelitic rock containing chlorite, kaolinite, and quartz the petrogenetic grid for metapelites (Figure 1) shows that such a rock can only form at relatively low pressures and temperatures. However, if it had carpholite instead of chlorite, then it would have formed at higher pressures, and if it had pyrophyllite instead of kaolinite ...
Subduction zones host a unique variety of rock types formed by the high-pressure, low-temperature conditions a subducting slab encounters during its descent. [4] The metamorphic conditions the slab passes through in this process generates and alters water bearing (hydrous) mineral phases, releasing water into the mantle.
[54] [55] [1] Before the mid-1970s, geologists utilized the metamorphic facies classification to investigate metamorphic rocks and determined their P-T characteristics. [1] However, little was known about the evolutionary processes of these P-T conditions and how metamorphic rocks reach the surface at that time.
Within the lagoons are living fossils called giant stromatolites, or layered rocks created by algae and minerals such as gypsum and rock salt. The inhospitable environment of the high salt plains ...
Little is known about the history of the oldest exposed rocks in the area due to extensive metamorphism.This somber, gray, almost featureless crystalline complex is composed of originally sedimentary and igneous rocks with large quantities of quartz and feldspar mixed in. [1] The original rocks were transformed to contorted schist and gneiss, making their original parentage almost unrecognizable.