Protoliths may be igneous, sedimentary or pre-existing metamorphic rocks. For example, blueschist and eclogite facies rocks form under low to medium

Eclogite is a metamorphic rock formed when mafic igneous rock is subjected to high pressure. "The oldest UHP eclogites of the World: age of UHP metamorphism, nature of protoliths and tectonic implications". Chemical Geology.

Our results suggest that the MORB-like protolith of the xenoliths was metasomatized by a fluid equilibrated with sediment in the fore-arc region of a subduction Lastly, analysis of Sm–Nd isotopes from the protoliths to the high-P rocks at Port Macquarie are used to identify the affinities of the metamorphic precursors. These Typical mineral assemblages of the eclogites are garnet + omphacite + mid- ocean ridge basalt affinities (MORB) with at least one protolith being a cumulate. The mafic rocks preserve partially transitional relationships from protolith gabbro to UHP eclogite, as documented by detailed petrological, geochronological, and. SHRIMP-RG zircon dating shows that the protolith of the eclogites formed within the Yukon-Tanana terrane during early, continental arc activity, between 364 470–450 Ma, the same as host gneiss protolith age), whereas dome‐core eclogite zircon has more scarce preservation of inherited zircon. Possible explanations than an intraplate or OIb setting for the protoliths of the eclogites.

Oxygen isotope compositions are reported for the first time for the Himalayan metabasites of the Kaghan Valley, Pakistan in this study. The highest metamorphic grades are recorded in the north of the valley, near the India-Asia collision boundary, in the form of high-pressure (HP: Group I) and ultrahigh-pressure (UHP: Group II) eclogites. Analyses from zircon cores in one sample yield scattered 433 to 474 Ma ages, reflecting partial overlap on rims, and constrain the minimum age of eclogite protolith crystallization. Inclusions of Th + REE-rich epidote, and zircon REE patterns are consistent with prograde metamorphic growth.

SHRIMP-RG zircon dating shows that the protolith of the eclogites formed within the Yukon-Tanana terrane during early, continental arc activity, between 364

Eclogites consist primarily of green pyroxene (omphacite) and red garnet (pyrope), with small amounts of various other stable minerals—e.g., rutile. They are formed when volcanic Analyses from zircon cores in one sample yield scattered 433 to 474 Ma ages, reflecting partial overlap on rims, and constrain the minimum age of eclogite protolith crystallization. Inclusions of Th + REE-rich epidote, and zircon REE patterns are consistent with prograde metamorphic growth. Contrary to this, we demonstrate that the Gubaoquan eclogite protolith was a Neoproterozoic basic dyke/sill which intruded into Proterozoic continental rocks.

indicating their crystallisation from a protolith with a short crustal residence time. amphibolite – eclogite source, i.e. melting over a range of pressures/depths.

Eclogite forms at pressures greater than those typical of the crust of the Earth. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. 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). Eclogite Eclogite: A high P/T metamorphic rock composed of more than 75% vol.

Eclogite genesis might have been by residue formation associated with the dehydration and partial melting of a protolith consisting of variably mixed, subducted ocean floor basalt and sediment. Kaalvallei Group II eclogite xenoliths are likely to have formed through crystallization of small-volume melts within conduits in old, enriched subcontinental lithosphere.

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 .
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The internal structures of zircons in eclogite from Huangzhen have been studied by cathodoluminescence (CL) microscopy. Two growth stages were distinguished: protolith magmatic cores and metamorphic overgrowth rims. These different domains were analyzed for trace elements using LAM-ICP-MS.

Island Arc, … EVOLUTION OF ECLOGITE FACIES METAMORPHISM IN THE ST. CYR KLIPPE, YUKON-TANANA TERRANE, YUKON, CANADA by Meredith Blair Petrie Ma, while the metatonalite protolith formed at approximately 334 Ma, during the Little Salmon Cycle of the Klinkit phase of Yukon-Tanana arc activity. Eclogite, any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt.

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If one adopts MORB as the protolith of eclogite it will be particularly dense because of its high SiO 2 (stishovite) content compared to other mafic protoliths, such as cumulates, restites, delaminated continental crust and the average composition of oceanic crust.

High-Mg olivine (forsterite with #Mg > 90) is often found in mantle peridotite or is enclosed in micro- and Our data provide new constraints on the timing of eclogite metamorphism within of the age of the magmatic eclogite protolith on Stolbikha Island, Gridino area, 23 Jun 2005 The window is even broader for Si-poor eclogites such as cumulates and many non-MORB protoliths. If the lower mantle is denser than pyrolite ( bimineralic xenoliths, diamond-bearing eclogite, corundum-bearing eclogite eclogite) are considered to derive from a heterogeneous protolith. Eclogite of eclogite and amphibolite do not define a whole rock iferous (Viséan) thrusting of the Teplá (~500 Ma) for the metagabbro protolith in the com- (1990).

Trace element data suggest that the eclogite protoliths include both enriched and normal mid‐oceanic ridge basalt (E‐MORB and N‐MORB) and also gabbroic cumulates. The blueschists show more variation in protoliths, which include N‐MORB, Oceanic Island Basalt (OIB) and Island Arc Basalt (IAB).

The protolith of the Kaalvallei eclogites also experienced Fe enrichment and Ca depletion with increasing alteration. In addition, population A eclogites exhibit Sr and Nd isotopic compositions similar to oceanic tholeiites. tary protolith of the complex is considered to be an eastern margin of the East European platform, which was subducted beneath island arc ( Leech and Ernst, 2000 ).

The eclogites have major element compositions corresponding to quartz-bearing Eclogite.