Metamorphic P–T evolution of garnet-staurolite-biotite pelitic schist and amphibolite from Keffi, north-central Nigeria: Geothermobarometry, mineral equilibrium modeling and P-T path

AbstractThe Banchetta-Rognosa tectonic unit (BRU), covering an area of 10 km2 in the upper Chisone valley, consists of two successions referred to a continental margin (Monte Banchetta succession) and a proximal oceanic domain (Punta Rognosa succession) respectively. In both successions, Mesozoic meta-sedimentary covers discordantly lie on their basement. This paper presents new data on the lithostratigraphy and the metamorphic evolution of the continental basement of the Monte Banchetta succession. It comprises two meta-sedimentary sequences with minor meta-intrusive bodies preserving their original lithostratigraphic configuration, despite the intense Alpine deformation and metamorphic re-equilibration. Phase equilibrium modeling points to a metamorphic eclogitic peak (D1 event) of 20–23 kbar and 440–500 °C, consistent among three different samples, analyzed from suitable lithologies. The exhumation P–T path is characterized by a first decompression of at least 10 kbar, leading to the development of the main regional foliation (i.e. tectono-metamorphic event D2). The subsequent exhumation stage (D3 event) is marked by a further decompression of almost 7–8 kbar associated with a significant temperature decrease (cooling down to 350–400 °C), implying a geothermal gradient compatible with a continental collision regime. These data infer for this unit higher peak P–T conditions than previously estimated with conventional thermobarometry. The comparison of our results with the peak P–T conditions registered by other neighboring tectonic units allows to interpret the BRU as one of the westernmost eclogite-facies unit in the Alps.

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METAMORPHIC EVOLUTION OF GARNET–BIOTITE–MUSCOVITE SCHIST FROM BARRU COMPLEX IN SOUTH SULAWESI, INDONESIA

Journal of Applied Geology ◽

10.22146/jag.7219 ◽

2015 ◽

Vol 6 (2) ◽

Author(s):

Nugroho Imam Setiawan ◽

Yasuhito Osanai ◽

Nobuhiko Nakano ◽

Tatsuro Adachi

Keyword(s):

Geothermal Gradient ◽

Metamorphic Rocks ◽

Metamorphic Evolution ◽

First Report ◽

Geothermal Gradients ◽

South Sulawesi ◽

Pelitic Schist ◽

T Path ◽

Tectonic Environments

This paper explains the first report in metamorphic evolution of pelitic schist from Barru Complex in South Sulawesi, Indonesia. Garnet-biotitemuscovite schist was examined petrologically to assess the metamorphic evolution history, which has implications on tectonic condition of this region. The rock mainly composed of garnet, biotite, muscovite, epidote, quartz, rutile, hematite, and plagioclase. Inclusions in the garnet preserve records of prograde stage of this rock, which are epidote, titanite, quartz, and apatite. Garnet, biotite, muscovite, quartz, rutile, and plagioclase are concluded as equilibrium assemblages at peak P-T condition of this rock, which estimated at 501–562 ºC and 0.89–0.97 GPa. The result is still on the ranges of the estimated geothermal gradient P-T path of eclogite from Bantimala Complex. Similar geothermal gradients of metamorphisms might be indicated that these metamorphic rocks were metamorphosed on the similar tectonic environments. Keywords: Pelitic schist, Barru Complex, South Sulawesi, metamorphic evolution.

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Petrology and phase equilibrium modeling of spinel-sapphirine-bearing mafic granulite from Akarui Point, L^|^uuml;tzow-Holm Complex, East Antarctica: Implications for the P-T path

Journal of Mineralogical and Petrological Sciences ◽

10.2465/jmps.130621a ◽

2013 ◽

Vol 108 (6) ◽

pp. 345-350 ◽

Cited By ~ 12

Author(s):

Shunki IWAMURA ◽

Toshiaki TSUNOGAE ◽

Mutsumi KATO ◽

Tatsuya KOIZUMI ◽

Daniel J. DUNKLEY

Keyword(s):

Phase Equilibrium ◽

East Antarctica ◽

Mafic Granulite ◽

Equilibrium Modeling ◽

T Path

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Petrography and phase equilibrium modeling of Paleoproterozoic metapelite in the Kuluktag area of Tarim Craton

10.5194/egusphere-egu21-11000 ◽

2021 ◽

Author(s):

Yu Guo

Keyword(s):

Phase Equilibrium ◽

Chemical System ◽

Equilibrium Modeling ◽

Fine Grained ◽

Metamorphic Basement ◽

Mineral Assemblages ◽

The Matrix ◽

Tarim Craton ◽

T Path ◽

Tectonothermal Event

&#160; The Kuruqtag area, located at the northeastern margin of the Tarim Craton, where the Precambrian metamorphic basement exposed, is ideal for studying the Precambrian geological evolution of the Tarim Craton. Previous zircon U-Pb chronology studies revealed that the metamorphic basement recorded a Paleoproterozoic tectonothermal event and suggested it associates with the Paleoproterozoic Nuna/Columbian supercontinent convergence event. However, the extensive range of metamorphic ages obtained from different studies (ranging from 1750-2000 Ma) and the lack of detailed P-T path corresponding to different metamorphic ages make it difficult to constrain the evolutionary framework of the Tarim craton during the Paleoproterozoic, which in turn affects future comparative regional studies.&#160; To constrain the P-T path, in this study, we performed detailed petrography, mineral chemical, and phase equilibrium modeling of metapelite collected from the khondalite series in the western part of the Kuruqtag (a garnet-sillimanite-cordierite-biotite gneiss with metamorphic age ~1850 Ma) and obtained the following results.&#160; Through petrographic studies, at least three phases of mineral assemblages can be used to invert the P-T path experienced by the metapelite. They are &#160; &#160;M1 (peak metamorphic stage):represented by fine-grained biotite remnant (Bi &#8544;) + fine-grained plagioclase(Pl &#8544;) and quartz+ Ilmenite + , occurring as inclusions within the metamorphic garnet, and equilibrated mineral assemblages is: Grt(core) + Bi &#8544; + Sill + Kfs + Pl &#8544; + Qz + Ilm.&#160;M2 (isothermal depression stage), represented by cordierite occurring in the garnet rim or with spinel in the matrix, inferred equilibrated mineral assemblages is Grt(rim)+Bi &#8544; +Cd+Kfs+Pl &#8544;&#8544;+Ilm+Sp.M3 (isothermal depression stage), is marked by the appearance of new growth of biotite(Bi &#8544;&#8544;) and the conversion of Sill to And.&#160;The P-T conditions for the mineral assemblage evolution (M1 &#8594; M3) are constrained by a P-T pseudosection constructed in the Na2O -CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O- TiO2-O2 chemical system. The resulting P-T path is clockwise from the M1 stage (840&#176;C, 4 Kbar) through the isothermal depression path to M2 (840-850&#176;C,5 Kbar) and then through the near-isobaric cooling path to the M3 stage (650&#176;C, 3.5-4 Kbar).

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Partial melting of zoisite eclogite from the Sanddal area, North-East Greenland Caledonides

European Journal of Mineralogy ◽

10.5194/ejm-32-405-2020 ◽

2020 ◽

Vol 32 (4) ◽

pp. 405-425 ◽

Cited By ~ 2

Author(s):

Wentao Cao ◽

Jane A. Gilotti ◽

Hans-Joachim Massonne

Keyword(s):

Partial Melting ◽

Mineral Assemblage ◽

Peak Pressure ◽

Bulk Rock ◽

East Greenland ◽

Equilibrium Modeling ◽

North East ◽

The North ◽

Area North ◽

T Path

Abstract. Metamorphic textures and a pressure–temperature (P–T) path of zoisite eclogite are presented to better understand the metamorphic evolution of the North-East Greenland eclogite province and this particular type of eclogite. The eclogite contained the mineral assemblage garnet, omphacite, kyanite, phengite, quartz and rutile at peak pressure. Partial melting occurred via breakdown of hydrous phases, paragonite, phengite and zoisite, based on (1) polymineralic inclusions of albite and K-feldspar with cusps into host garnet, (2) small euhedral garnet with straight boundaries against plagioclase, (3) cusps of plagioclase into surrounding phases (such as garnet), and (4) graphic intergrowth of plagioclase and amphibole next to anhedral zoisite grains. Isochemical phase equilibrium modeling of a melt-reintegrated composition, along with XNa-in-omphacite and Si-in-phengite isopleths, yields a peak pressure of 2.4±0.1 GPa at 830±30 ∘C. A peak temperature of 900±50 ∘C at 1.9±0.2 GPa is determined using the rim composition of small euhedral garnet, as predicted by modeling a crystallized melt pocket. Zoisite growth at the expense of kyanite suggests that the P–T path crossed the fields of zoisite growth at ∼1.9 GPa, 800–900 ∘C on the modeled phase diagram of the bulk rock. A point on the exhumation path at ∼1.3 GPa and 750 ∘C is derived from hornblende-plagioclase thermometry and Al-in-hornblende barometry. The study demonstrates that paragonite, phengite and zoisite could contribute to partial melting of eclogite at near-peak P and during exhumation.

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