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A common anticlockwise P-T-t path. Metamorphic rocks with anticlockwise P-T-t paths are commonly associated with a near-isobaric cooling P-T trajectory. [11] Anticlockwise P-T-t path normally consists of two parts: [2] Initial heating and compression until reaching a peak, a low pressure-high temperature peak is often observed.
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.
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith ) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 megapascals (1,000 bar ) or more, causing profound physical or chemical changes.
Metamorphic rocks are created by rocks that have been transformed into another kind of rock, usually by some combination of heat, pressure, and chemical alteration. Sedimentary rocks are created by a variety of processes but usually involving deposition, grain by grain, layer by layer, in water or, in the case of terrestrial sediments, on land ...
Metamorphism of crustal rocks in which peak temperature exceeds 900 °C, recognized either by robust thermobarometry or by the presence of a diagnostic mineral assemblage in an appropriate bulk composition and oxidation state, such as assemblages with orthopyroxene + sillimanite + quartz, sapphirine + quartz or spinel + quartz, generally at pressure conditions of sillimanite stability in ...
The Neoarchean rocks in the Precambrian basement are mainly composed of greenstones, high-grade metamorphic rocks and granitoids. [16] Mineral examinations show an isobaric cooling-type anticlockwise pressure-temperature (P-T) path, indicating there were intrusions and underplating events during the crustal growth in Neoarchean. [17]
Eclogites are high-pressure (HP) to ultrahigh-pressure (UHP) metamorphic rocks that are indicative of subduction zone metamorphism. [10] The eclogites in central Tibet are of Early Mesozoic origin, and they appear to be the result of diachronous collision between the eastern Qiangtang terrane and the western Qiangtang-Lhasa plate, along the ...
For example, a metamorphic rock in the Neil Bay area of northern Saskatchewan underwent high grade (high P/T) metamorphism followed by exhumation (uplift). [36] The porphyroblast of garnet was formed during high grade metamorphism while the porphyroblast of cordierite was formed during subsequent exhumation. Both porphyroblasts contain monazite ...