Qualitative and quantitative petrography of meta - Bachelor

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It is formed in the subduction zone environment with low geothermal gradients (4-14°C km-1) and is characterized by the presence of HP/LT index minerals like glaucophane, lawsonite, aragonite, jadeite, and deerite (Fig.1). Geochemistry of eclogite- and blueschist-facies rocks from the Bantimala Complex, South Sulawesi, Indonesia: Protolith origin and tectonic setting. 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. 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.

Eclogite protolith

Uplift and decompression resulted in the formation of some new minerals, which occurred at 1.89 billion years (late Paleoproterozoic). Specimen owned by James Cheshire. 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. Trends in the Sr^Pb isotopic compositions of the eclogite clinopyroxene show that seawateralteration of the oceanic crust pro- toliths was an important process during protolith formation, and cryptic metasomatism further increased the Pb and Sr isotope values.This metasomatism is probably associated with theJurassic kimberlite magmatism; however, contributionsfrom the Mesoproter- ozoic Mackenzie event cannot be completely excluded. Many investigators believe that eclogite is representative of numerous parts of the upper mantle. In the crust, eclogites generally occur as xenoliths (i.e., foreign inclusions) in igneous rocks and as isolated blocks measuring as much as 100 m (328 feet) across in metamorphic rocks.

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Eclogite (Muenchberg Gneiss Massif; Early Ordovician protolith, about 480 Ma; Late Devonian metamorphism, about 365 Ma; Wissenstein, just south of Stammbach, Frankenwald Forest, Bavaria, southeast-central Germany) 1 (15097930745).jpg 734 × 837; 855 KB. On the contrary, both the Jericho DIs and host eclogite garnets have small negative Eu and Sr anomalies, fractionated HREE patterns ((Lu N /Gd N)~3-5) and pristine mantle-like δ 18 O values of 5.2-6.0‰, indicating that shallow, plagioclase-rich oceanic crust protoliths are unlikely.The eclogitic DI trace-element characteristics require that both garnet and plagioclase were present in the protolith, which likely crystallized in the shallow upper mantle. printing (Fig. 2a). The protolith is low-K basalt in composition and exhibits geochemical characters of normal-type MORB (N-MORB) afﬁnity (Song et al.

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Eclogite xenoliths and eclogitic diamond inclusions from the Slave craton almost exclusively yield c. 2 Ga ages, which are broadly com- CONSTRAINTS ON THE ECLOGITE PROTOLITH The Nunatak eclogites exhibit prominent negative Eu anomalies (Fig. DR2) that point toward plagioclase fractionation in a “shallow” magmatic precursor that, in concert with crustal δ18O signatures in garnet (Fig. 3C), suggests a basaltic oceanic crust protolith (e.g., Jacob, 2004). Eclogite is just one example; various peridotites and magmas differ in intrinsic density by amounts more than can be overcome by normal temperature variations, and should therefore concentrate at various levels. Even the crust and continental lithosphere appear to stratified by intrinsic density.

470 –450 Ma, the same as host gneiss protolith age), whereas 12 Oct 2017 As the eclogite facies boundary has a positive dP/dT, cooling from Protolith composition and the efficiency of metamorphic conversion are Çaml›ca metamorphics preserve an early eclogite-facies mineral assemblage of garnet + omphacite + glaucophane. + rutile ± paragonite, strongly overprinted and constrain the minimum age of eclogite protolith crystallization. Inclusions of Th + REE-rich epidote, and zircon REE patterns are consistent with prograde protolith of the eclogites experienced a matamorphic process from high greenchist facies through amphibolite facies, eclogite facies and amphibolite facies to oceanic rocks (protolith oceanic tholeiitic basalt with MORB composition). Eclogite occurs within a serpentinite matrix, accompanied by mafic rocks resembling a The progressive convergence led to the formation of the eclogite facies assemblages at the retrogressed eclogites indicate protoliths that correspond to. 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.
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1 Feb 2017 Based on the bulk rock composition and isotopic data, the protoliths of the Kaghan and Tso Morari eclogites are interpreted as Permian Panjal 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 ( Interlayered Eclogites, Blueschists and Epidote Amphibolites from NE Oman: a Record of Protolith Compositional Control and Limited Fluid Infiltration. The whole-rock trace element composition is consistent with a pyroxenitic protolith.

[2007] inferred that the 13–14 Ma ages of Rolfo et al. [2005] dated their M3 granulite-facies event, but were unable to provide any direct evidence to support this hypothesis. Liu et al. [2007] dated three The magmatic zircon from both the retrograded eclogite and mafic schist yielded protolith ages of 451 ± 3 Ma, which is consistent with the ages of Early Palaeozoic ophiolitic complexes and ocean island sequences in the CMOB reported in previous studies.
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U-Pb datering av zirkon från migmatitisk gnejs i Delsjöområdet

Amphibolite is a grouping of rocks composed mainly of amphibole and plagioclase feldspar, with little or no quartz.It is typically dark-colored and dense, with a weakly foliated or schistose (flaky) structure. Metamorphic rock - Metamorphic rock - Zeolite facies: In the zeolite facies, sediments and volcanic debris show the first major response to burial.

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For example, blueschist and eclogite facies rocks form under low to medium Petrochemical data suggest that the eclogite protoliths were typical MORB basalts, derived from depleted mantle. SHRIMP U–Pb dating of zircons from the Blueschists And Eclogites Both Form From A Basalt Protolith During Blueschist Eclogite Blue amphibole [Naz) [Mg3Al2] SiO22 (OH)2 Pyroxene Na (AI, Fe) 18 Nov 2013 The protolith may be sedimentary, igneous or another older basalt turns into greenschist, but under high pressures, it turns into eclogite. 2 Jul 2011 Eclogites form when mafic rock encounters temperatures greater than ~400 degrees Celsius and pressures greater than ~12 kbar (or ~1.2 GPa). (2005), who argued that the Tiburon eclogites and associated mafic metamorphic rocks had an island arc basalt protolith, based on slightly low Nd isotopic formed at N14 kbar and ~710 °C in the eclogite facies.

Changes of bulk rock chemistry, mineral assemblages and compositions, as well as microstructures operate in concert both before and during subduction to transmogrify ocean floor basalt into subduction zone eclogite. We present textural and chemical characterizations of suites of 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. 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 (Fig. 2). The major protolith of the soils in this portion of coastal Maine is glacial till.