The protolith to the eclogite is believed to be a Fe- and Ti-rich gabbro of Pro-terozoic age. Transformation into eclogite is related to Cale-donian high-pressure metamorphism at ca. 400 Ma. During this process, ilmenite in the gabbro protolith was replaced by rutile. The eclogite body is subdivided into a leuco-eclogite and a ferro-eclogite
The basic blocks represented by the protolith of the eclogites were most likely scraped from the basement of a continental arc by basal erosion during the subduction of the South Tianshan Ocean in Late Paleozoic.
2011-12-01 2019-05-01 2016-12-01 Eclogite. Eclogite: A high P/T metamorphic rock composed of more than 75% vol. garnet (often pyrope or Mg-rich almandine) and omphacite (Na-Ca-Al-Mg clinopyroxene). Both must be present and neither component more than 75% vol. Eclogite never contains plagioclase.
Rutile, kyanite, and quartz are typically present. Immobile trace element contents of Stak eclogites are similar to those of the Permian Panjal Traps and significantly different from those of the Deccan Traps erupted at 73–66 Ma in the northwestern Indian plate, suggesting that the Panjal Traps is the protolith of the Stak eclogites. Major element contents of the eclogite cores are broadly similar to basalts with the exception of the high Na contents, presumably reflecting a seawater-altered oceanic crust protolith . Retrogression from eclogite to blueschist to greenschist is associated with decreasing SiO 2 and Na 2 O but increasing Al 2 O 3 content ( Figs.
4 Aug 2015 The protolith ages of the eclogites within the High-Grade Metamorphic Complex on the north side of the Posada–Asinara Line are Ordovician,
Protolith rocks to the Hallandia gneiss are 1.74 –. 1.66 Ga The intrusive protoliths to orogen that hosts eclogite-bearing tectonic units, as. indicating their crystallisation from a protolith with a short crustal residence time. amphibolite – eclogite source, i.e.
The variability of δ18O in garnet among 41 xenoliths, shows a bi-modal distribution with median values at 3.57 ‰ and 5.68 ‰ and strong correlation (r = 0.96) between garnet and omphacite. The δ18O values and the reconstructed whole-rock trace element compositions indicate an oceanic crustal protolith for mantle eclogite xenoliths.
The protolith to the eclogite is believed to be a Fe- and Ti-rich gabbro of Pro-terozoic age. Transformation into eclogite is related to Cale-donian high-pressure metamorphism at ca. 400 Ma. During this process, ilmenite in the gabbro protolith was replaced by rutile. The eclogite body is subdivided into a leuco-eclogite and a ferro-eclogite Based on compositional zoning in garnet and application of diffusion modelling, we propose that eclogite-facies metamorphism of the mafic protolith and its host lithologies occurred at, or near, UHP conditions. The core garnet (I) formed at 650 °C at 8 Myr in the coesite stability field and was partially resorbed during the onset of exhumation. Examine the sample labeled eclogite, which forms when basalt or gabbro is metamorphosed at very high pressure, such as deep in a subduction zone, 1. Note the bimodal color of this rock.
Geochemistry of eclogite- and blueschist-facies rocks from the bantimala complex, south sulawesi, indonesia: Protolith origin and tectonic setting Citation Maulana, A, Christy, A, IMAI, A et al 2013, 'Geochemistry of eclogite- and blueschist-facies rocks from the bantimala complex, south sulawesi, indonesia: Protolith origin and tectonic setting', The Island Arc, vol. 22, no. 4, pp. 427-452.
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4, pp. 427-452. In order to decipher the origin of eclogite in the high-P/T Sanbagawa metamorphic belt, SHRIMP U–Pb ages of zircons from quartz-bearing eclogite and associated quartz-rich rock (metasandstone) were determined.
High Ni and Cr contents of some orthopyroxene bearing eclogites indicative that olivine and chromium-spinel were present in the protolith.
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The eclogite unit occurs in the LHS below the MCT, and the protolith is considered to be 110–88-Ma-old (cretaceous volcanics in the LHS). The peak metamorphic condition was estimated as P > 15 kb (probably up to 20 kb) for a minimum temperature of 580°C (Groppo et al., 2007).
Retrogression from eclogite to blueschist to greenschist is associated with decreasing SiO 2 and Na 2 O but increasing Al 2 O 3 content ( Figs. 2B, 2D ).
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7 Feb 2015 (1997) Protoliths of the gneisses and mafic rocks in the Hellevik-Flekke area in Sunnfjord, Western. Norway. Norwegian Geological Survey
The original rock that has undergone metamorphism is called the protolith.
Eclogite-rich layers would be intermittent because of low melting points and the temperature-dependency of the relevant phase changes. and the composition of the lower mantle. If one adopts MORB as the protolith of eclogite it will be particularly dense because of its high SiO 2 (stishovite)
Most eclogite facies are eclogites– that is, they are basalts or gabbros which have experienced metamorphism at eclogite facies pressures and temperatures. The kyanite eclogite and one bimineralic eclogite occur with slight positive Eu-anomalies, whereas in the remaining eclogites no indication of plagioclase in the protolith is present. High Ni and Cr contents of some orthopyroxene bearing eclogites indicative that olivine and chromium-spinel were present in the protolith. Amphibolite (/ æ m ˈ f ɪ b ə l aɪ t /) is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase..
Eclogite facies, Vendée, Although derived from the garnet stability field, these rocks have low-pressure cumulate protoliths containing plagioclase, olivine, and clinopyroxene as reflected 18 Mar 2020 Protolith nature and P–T evolution of Variscan metamorphic rocks from associated with blueschists and eclogites, northern New Caledonia.