Stability field of the high-pressure assemblage talc + phengite and two new phengite barometers

Massonne, Hans‐Joachim; Schreyer, Werner

doi:10.1127/ejm/1/3/0391

Cited by 160 publications

(85 citation statements)

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“…The temperature estimate of ~910 ºC is consistent with the hypothesis that the amphibole inclusion in garnet was mantle-derived, and may be stable up to ~900 ºC at upper mantle conditions (Ernst, 1999). Peak UHP stage (II) P-T conditions for the peak UHP metamorphic stage are calculated from the core and rim compositions of minerals of prograde growth zonation, in which reference pressures are produced using the phengite Si barometer of Massone and Schreyer (1989). For rutile eclogite sample B45-a, a nearpeak reference pressure is estimated at ~30 kbar from a low-Si phengite core composition, whereas a peak reference pressure of ~37 kbar is yielded from a high-Si phengite rim composition ( Table 2).…”

Section: Pre-peak Prograde Stage (I)supporting

confidence: 67%

Assemblages and Textural Evolution of UHP Eclogites from the Chinese Continental Scientific Drilling Main Hole

Tong

Jahn

Iizuka

et al. 2007

International Geology Review

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Coesite-bearing eclogite samples from the Chinese Continental Scientific Drilling main hole (100-2000 m) were examined. Three major evolutionary stages are distinguished from mineral assemblages and textural relations.(1) The pre-peak stage is indicated by inclusion assemblages in rutile eclogite such as amphibole and paragonite, with pre-peak P-T conditions of ~13 kbar and 910ºC. (2) The peak ultrahigh-pressure (UHP) metamorphic stage is characterized by the mineral assemblage garnet-omphacite-phengite-rutile-apatite-coesite/quartz pseudomorph ± kyanite; P-T conditions reached ~910ºC and ~37 kbar for rutile eclogite, and ~850ºC and ~35 kbar for phengite eclogite. (3) The retrograde stage produced decompression textures via back reactions, such as thin coronas of amphibole or zoisite on garnet, fine-grained amphibole-plagioclase symplectites on omphacite and biotite-plagioclase, or K-feldspar-albite on phengite, ilmenite or titanite on rutile, at P-T conditions of 530-560ºC and 7-9 kbar. The presence of K-feldspar-albite symplectite on phengite and minor interstitial K-feldspar implies that post-peak decompressional partial melting occurred locally during rapid exhumation of the subducted UHP slab.Two alternative P-T paths may be constructed: (1) the first possesses a different pre-peak stage but similar peak UHP to post-peak decompression cooling for rutile and phengite eclogite; (2) the second shows a consistent evolution from a pre-peak stage via peak UHP stage to a post-peak stage of near-isothermal decompression, followed by near-isobaric cooling for both rutile and phengite eclogite. We prefer the first P-T path, because the inferred paths show a clear increase in pressure and temperature from near-peak to peak UHP stage, and this may be associated with subductionrelated tectonism as a result of continental collision between the North China and Yangtze blocks. Rapid subduction and fast retrograde exhumation is likely responsible for preservation of some pre-peak inclusion assemblages and prograde mineral growth zoning.

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Section: Pre-peak Prograde Stage (I)supporting

confidence: 67%

Assemblages and Textural Evolution of UHP Eclogites from the Chinese Continental Scientific Drilling Main Hole

Tong

Jahn

Iizuka

et al. 2007

International Geology Review

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“…This corresponds to minimum pressure between 6 and 8 kbar at estimated 600°C (cf. Massonne and Schreyer 1989). As to amphibole mineral chemistry, amphibole characterized by high Na in the M4 position (>0.5 pfu) and in the A-position (≥0.75 pfu) is restricted to eclogites.…”

Section: Amphibolite Faciesmentioning

confidence: 99%

Geochronology of fluid-induced eclogite and amphibolite facies metamorphic reactions in a subduction–collision system, Bergen Arcs, Norway

Glodny

Kühn

Austrheim

2007

Contrib Mineral Petrol

117

100

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Rb-Sr multimineral isochron data for metamorphic veins allow to date separate increments of the mineral reaction history of polymetamorphic terranes. Granulite facies rocks of the Lindås nappe, Bergen Arcs, Norway, were subducted and exhumed during the Caledonian orogeny. The rocks show petrographic evidence for two distinct events of local fluid infiltration and vein formation, along fractures and shear zones. The first occurred at eclogite facies (15-21 kbar, 650-750 °C) and a later one at amphibolite facies conditions (8-10 kbar, 600°C). The presence of fluids enabled local metamorphic equilibration only near fluid pathways. In fluid-absent domains, preexisting assemblages were metastably preserved. This resulted in a heterogeneity of metamorphic signatures on m-to µm-scales. Well-preserved granulite facies rocks preserve their Proterozoic Rb-Sr mineral ages, as does the U-Pb system of zircon in most lithologies. Six Rb/Sr multimineral isochron ages for eclogite facies veins and their immediate wallrocks date the fluid-induced eclogitization at 429.9 ± 3.5 Ma (2σ, weighted average, MSWD = 0.39). An eclogite facies vein has yield metamorphic zircon with concordant U-Pb ages of 429 ± 3 Ma, identical to the U-Pb age of 427.4 ± 0.9 Ma for zircon xenocrysts in an amphibolite facies vein. Seven Rb/Sr mineral isochron ages date amphibolite-facies fluid infiltration at 414.2 ± 2.8 Ma (MSWD = 1.5), an age value testifying to residence of the rocks in the deep orogenic crust at temperatures >600°C for nearly 15 Ma. The new data show that Rb-Sr mineral isochron ages effectively date fluid-induced (re)crystallization events rather than stages of cooling. The direct link between isotopic ages and distinct petrographic equilibrium assemblages aids to constrain the evolution of rocks in the P-T-reaction-time space, which is essential for understanding exhumation histories and the internal dynamics of orogens in general.

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“…Massonne determined the Si content of phengite in the pelitic schist of the Makbal Complex to be 3.42 for O = 11 basis [ Fig. 12a of Massonne and Schreyer (1989)]. Based on the phengite geobarometry of the talc + phengite + phlogopite + kyanite + silica mineral assemblage, Massonne and Schreyer (1989) estimated the metamorphic pressure to be 2.5 GPa at 600 °C.…”

Section: Coesite-bearing Pelitic Schists and Quartz Schistsmentioning

confidence: 99%

“…12a of Massonne and Schreyer (1989)]. Based on the phengite geobarometry of the talc + phengite + phlogopite + kyanite + silica mineral assemblage, Massonne and Schreyer (1989) estimated the metamorphic pressure to be 2.5 GPa at 600 °C. However, phengite in our samples (e.g., 1609 -KYR18) is not associated with phlogopite and kyanite.…”

Section: Coesite-bearing Pelitic Schists and Quartz Schistsmentioning

confidence: 99%

Intrusion of UHP metamorphic rocks into the upper crust of Kyrgyzian Tien-Shan: P-T path and metamorphic age of the Makbal Complex

Tagiri

Takiguchi²,

Ishida

et al. 2010

Journal of Mineralogical and Petrological Sciences

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Coesite occurs in garnets from quartz schists and pelitic schists in the Makbal Complex of Kyrgyzian TienShan. The thick quartz schists interbedded with pelitic schists are the transitional facies after coesite schists. Quartz -pseudomorph after coesite also appears widely in pelitic schists and quartz schists, but is rare in eclogitic rocks. The growth zoning of garnets and Na -Ca amphiboles in eclogites and the garnet -omphacite geothermometry indicate that the metamorphic P -T paths of eclogites are different from each. Ultra -high (UHP) pressure metamorphic rocks of the Makbal Complex are mainly composed of pelitic and quartz schists. All eclogite lenses are included in the host UHPM rocks, although most of them do not contain UHP metamorphic (UHPM) evidences. The K -Ar ages of phengite in a host pelitic schist and of paragonite in an eclogite are approximately 500 Ma, while those of biotite and phengite in a biotite -bearing mica schist and of winchite in a winchite schist are approximately 769 -717 Ma and 881 Ma, respectively. The evidence indicates that this complex is a tectonic mélange. These geological relationships suggest that the ascending substances must be pelitic and quartz schists. The UHPM rocks in the ascending material capture many exotic blocks as xenoliths during intrusion into the upper crust.

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Stability field of the high-pressure assemblage talc + phengite and two new phengite barometers

Cited by 160 publications

References 0 publications

Assemblages and Textural Evolution of UHP Eclogites from the Chinese Continental Scientific Drilling Main Hole

Assemblages and Textural Evolution of UHP Eclogites from the Chinese Continental Scientific Drilling Main Hole

Geochronology of fluid-induced eclogite and amphibolite facies metamorphic reactions in a subduction–collision system, Bergen Arcs, Norway

Intrusion of UHP metamorphic rocks into the upper crust of Kyrgyzian Tien-Shan: P-T path and metamorphic age of the Makbal Complex

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