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(a) Garnet composition in terms of almandine, pyrope and grossular end-members. (b) Garnet zoning in sample RR 10 shows a smooth profile, with decreasing spessartine and grossular and increasing pyrope from core to rim. This profile is typical of growth zoning.
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The Raspas Complex (Ecuador) contains one of the few eclogitic bodies in the northern Andes. It consists of metaperidotites, eclogites, and metapelites. The latter display three assemblages: (i) garnet + chloritoid + kyanite, (ii) garnet + chloritoid and (iii) garnet + chlorite, in all cases with quartz and muscovite in addition. The growth of thes...
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... is characterised by a high almandine end- member content, averaging around 65 mol% (Table 3, Fig. 5). The zoning profile (Fig. 5b) shows a decreasing Table 2. Whole-rock chemistry of metapelites from the Raspas Complex. Table 3. Representative electron microprobe analyses and structural formulae of garnet. Estimation of the Fe 3+ content in garnet has been done on the basis of 24 oxygens and 16 cations (e.g. Spear, 1993). End-members ...
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... is characterised by a high almandine end- member content, averaging around 65 mol% (Table 3, Fig. 5). The zoning profile (Fig. 5b) shows a decreasing Table 2. Whole-rock chemistry of metapelites from the Raspas Complex. Table 3. Representative electron microprobe analyses and structural formulae of garnet. Estimation of the Fe 3+ content in garnet has been done on the basis of 24 oxygens and 16 cations (e.g. Spear, 1993). End-members have been calculated according ...
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... of the garnet porphyroblasts. Average variations in core and rim compositions are Alm60-76, Sps1-6, Prp2-9, Grs13-27 and Alm60-73, Sps0.3-1 Prp8-20, Grs15-23, respectively. All samples show a decreasing grossular content from core to rim, but garnet from sample 98RR10 shows a larger varia- tion in grossular content compared to the other samples (Fig. 5a). This behaviour is consistent with the occurrence of titanite inclusions (instead of rutile) in garnet cores from sample 98RR10. The Mg/(Fe+Mg) ratio is higher in the samples 98RR10 and 97Ce3 compared to the sample 97Ce5, i.e. in the Grt+Chl paragenesis compared to the Grt+Cld+Ky ...
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... potentially significant, the effect of MnO is considered minor in the Raspas metapelites because of the observed mineral compositions: the spessartine content in garnet rims does not exceed 1.1 mole per cent (Table 3 and Fig. 5b), and the X Mn in chloritoid is equal or lower to 0.01 (Table ...
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Citations
... Conventional thermobarometry indicates peak metamorphic conditions of 550-650 • C and 1.8-2.0 GPa for eclogites (Feininger, 1980;John et al., 2010), and 550-600 • C and 2.0 GPa for garnet-chloritoidkyanite metapelites (Gabriele et al., 2003). However, the P-T conditions of the blueschists are unclear, with some studies suggesting that they may be related to the retrograde processes of eclogites at 400-500 • C (Feininger, 1980), while others suggest that they experienced metamorphism at similar conditions to the eclogites but at lower pressure (i.e., 550-650 • C and 1.4-1.6 ...
... Las metabasitas del complejo Raspas están constituidas por eclogitas, anfibolitas con granate y esquistos azules, donde se evidencian procesos de metamorfismo retrógrado en la transición de las facies de eclogita a las facies de esquistos azules de alta T, esto es consistente con los análisis petrográficos y geoquímicos realizados en dichos esquistos azules (Gabriele et al., 2003). De acuerdo con Feininger (1982), las rocas prógradas de Raspas incluyen esquistos pelíticos, anfibolitas y eclogitas con cianita, mientras que las rocas retrógradas abarcan principalmente esquistos con glaucofana. ...
... Obtenido de McAleer et al., 2016y Vernon, 1976 Respecto al metamorfismo retrógrado del complejo Raspas, Gabriele (2003) indica que las características petrográficas y químicas de los esquistos azules son consistentes con una etapa de retrometamorfismo de las eclogitas. Desafortunadamente no se tiene acceso a validar información en la tesis de Gabriele et al. (2003). ...
... Obtenido de McAleer et al., 2016y Vernon, 1976 Respecto al metamorfismo retrógrado del complejo Raspas, Gabriele (2003) indica que las características petrográficas y químicas de los esquistos azules son consistentes con una etapa de retrometamorfismo de las eclogitas. Desafortunadamente no se tiene acceso a validar información en la tesis de Gabriele et al. (2003). En la eclogita de esta investigación no se encontró algún mineral índice de otra facies, por lo que el retrometamorfismo se encontraría en la misma facies de eclogita, en cualquier caso, la preservación de la paragénesis de alta presión indicaría una alta tasa de exhumación (Gabriele et al., 2003). ...
TheElOroMetamorphicComplex,locatedinsouthwesternEcuador,consistsofdifferentlow-andhigh-grademetamorphicrocks.Theevidenceofretrogrademetamorphismisstudiedthroughthebibliographicreview,especially,oftheresultsobtainedintheElOroMetamorphicComplex(1990-1993)aspartoftheCordilleraRealProject(1986-1993)andotherrecentpapers.EvidenceofretrogrademetamorphismhasbeenmentionedintheQuebradaPlataUnitfromamphibolitetogreenschistsfaciesandintheRaspasophioliticcomplexfromeclogitetoblueschists.Inaddition,petrographicevidenceofretrogrademetamorphismhasbeenobtainedinaneclogiteblockfromLaChilcaUnit.Also,retrogrademetamorphismisdescribedregardingtheevolutionofthemetamorphiccomplex(QuebradaPlataUnit),theexhumationprocesses,associatedgeologicalstructuresandmineralreactions.
... Las metabasitas del complejo Raspas están constituidas por eclogitas, anfibolitas con granate y esquistos azules, donde se evidencian procesos de metamorfismo retrógrado en la transición de las facies de eclogita a las facies de esquistos azules de alta T, esto es consistente con los análisis petrográficos y geoquímicos realizados en dichos esquistos azules (Gabriele et al., 2003). De acuerdo con Feininger (1982), las rocas prógradas de Raspas incluyen esquistos pelíticos, anfibolitas y eclogitas con cianita, mientras que las rocas retrógradas abarcan principalmente esquistos con glaucofana. ...
... Obtenido de McAleer et al., 2016y Vernon, 1976 Respecto al metamorfismo retrógrado del complejo Raspas, Gabriele (2003) indica que las características petrográficas y químicas de los esquistos azules son consistentes con una etapa de retrometamorfismo de las eclogitas. Desafortunadamente no se tiene acceso a validar información en la tesis de Gabriele et al. (2003). ...
... Obtenido de McAleer et al., 2016y Vernon, 1976 Respecto al metamorfismo retrógrado del complejo Raspas, Gabriele (2003) indica que las características petrográficas y químicas de los esquistos azules son consistentes con una etapa de retrometamorfismo de las eclogitas. Desafortunadamente no se tiene acceso a validar información en la tesis de Gabriele et al. (2003). En la eclogita de esta investigación no se encontró algún mineral índice de otra facies, por lo que el retrometamorfismo se encontraría en la misma facies de eclogita, en cualquier caso, la preservación de la paragénesis de alta presión indicaría una alta tasa de exhumación (Gabriele et al., 2003). ...
Desde los albores de la humanidad, hemos mirado al cielo y nos hemos preguntado qué lugar ocupa nuestra Tierra, qué hay más allá de nuestro sistema solar. Hemos avanzado tecnológicamente, se han crearon telescopios para explorar el universo, recoger señales de radio que vienen de las estrellas con la esperanza de hallar un mensaje de otra civilización, se busca vida microscópica en otros planetas, se construyeron naves para visitar la Luna, se estudia el origen del universo como se estudia el origen de la vida en la Tierra y tenemos una estación espacial permanente patrullando nuestro planeta. Pero aún tenemos mucho por descubrir o redescubrir en el mar que nos atrae con su sabiduría poderosa ya que fue allí donde comenzó la vida, un mar que estamos empeñados en contaminar con nuestras acciones irresponsables. Nuestros bosques que nos atraen, en los que nuestros ancestros vivieron en nidos construidos en los árboles o en cuevas para protegerse de las inclemencias del tiempo y de los predadores. Por último, las estrellas, que siguen apasionando a nuestras sociedades.
... The abundant evidence for sediment involvement in arc volcanics suggests that much of the sedimentary component leaves the interface at sub-arc depths, which correspond to pressures predominantly between 2 and 3 GPa (histograms at the top of Figure 11). The rarity of metasediments in HPLT terrains that record sub-arc pressures-except as thin veneers on fragments of oceanic crust (e.g., Gabriele et al., 2003;Reinecke, 1998;Smye et al., 2010)-may therefore be seen as the counterpart to the presence of sedimentary material in arc volcanic rocks (e.g., Behn et al., 2011;Marschall & Schumacher, 2012). ...
The compositional range of ∼2,000 marine sediments and ∼19,000 oceanic igneous rocks is encapsulated by a set of 12 sedimentary and 10 mafic rock compositions, allowing computation of phase relationships on P‐T paths along subduction interfaces. These are described economically by a partitioning analysis, which connects the mineral assemblages to different parts of the subduction P‐T space and facilitates assessment of prograde dehydration, melting, densification, and rheological systematics. Dehydration and densification occur at shallower depths than in studies that neglect shear heating. Lawsonite stability is limited to interfaces where convergence is slower than 20 mm/yr; such rates also favor transport of volatiles beyond the arc. Terrigenous sediments and mafic rocks reach their solidi close to the top of the wedge‐slab interface; melt fractions are enhanced by fluid from the dehydrating slab interior. Rheological calculations show that the most abundant sediment types have interface capacities of hundreds of meters to kilometers, and that the strengths of mafic rocks comfortably exceed their buoyancy stresses. Above ∼650°C sediments are weak enough to rise as diapirs into the mantle wedge. Carbonate‐ and serpentinite‐rich lithologies are weaker than other interface rocks, and ascend most rapidly at the cessation of subduction. Ascent rates drop abruptly as rocks enter the plate interface, probably leading to retrograde equilibrium at P ∼ 1–1.5 GPa. The seismic‐aseismic transition is expected at about 500°C in mafics, and 400°C in metasediments. Seamounts are weaker than most other interface rocks, and unlikely to form asperities. Slow slip and tremor may be associated with the blueschist‐eclogite transition.
... The Raspas Complex, SW Ecuador, is part of the larger El Oro metamorphic complex and preserves an ophiolitic section of exhumed oceanic lithosphere. The Raspas Complex comprises garnet-chloritoid-kyanite bearing metapelitic assemblages, blueschists, and eclogites (e.g., Feininger, 1980;Gabriele et al., 2004). Peak prograde metamorphic conditions were around 2 GPa and 600 ± 30°C (Gabriele et al., 2004;John et al., 2010). ...
... The Raspas Complex comprises garnet-chloritoid-kyanite bearing metapelitic assemblages, blueschists, and eclogites (e.g., Feininger, 1980;Gabriele et al., 2004). Peak prograde metamorphic conditions were around 2 GPa and 600 ± 30°C (Gabriele et al., 2004;John et al., 2010). Previous Lu-Hf in garnet and phengite Ar-Ar geochronology (Bosch et al., 2002) suggest that the samples experienced peak metamorphism at 130 Ma before rapidly cooling to nearer $400°C around 123 Ma . ...
Fluid release from subducting slabs during recycling of oceanic lithosphere plays an important role in concentrating select elements near the Earth’s surface. Yet the extent to which these fluids are oxidising or reducing (fO2), one of the key characteristics that controls element mobility, remains poorly understood. Additionally, it is unclear whether the fO2 signature of arc fluids is generated deep within the slab during subduction or if it reflects later, shallower subarc crustal processes. Previous experimental work has shown that the extent to which highly incompatible W partitions into aqueous fluids depends on the temperature and fO2 conditions of the fluids. In the subducting slab, W partitions into rutile with a different coordination number to that which it exhibits in fluids, a process which may generate stable W isotopic fractionation. Therefore, if the competition between partitioning into aqueous fluids versus rutile is controlled by the conditions within the subducting slab, the elemental and stable W isotopic systematics of arc lavas may provide a novel tool with which to investigate subduction zones. We present isotopic compositions of a well characterised suite of arc lavas from the central island province of the Mariana arc (W. Pacific), and rutile separates from exhumed fragments of subducted, depleted, mafic oceanic crust from the Raspas Complex, Ecuador. Our data show that lavas from Guguan that exhibit the strongest geochemical signature of subduction zone fluids (e.g., high Ba/Th, Mo/Ce, Pb/Ce), contain the highest abundances of W compared to similarly magmatically incompatible Th, in agreement with anticipated fluid mobile behaviour. These Guguan lavas have distinct, heavy stable W isotopic compositions (δ186/184W = +0.134 to +0.156 ‰) compared to MORB (δ186/184W = +0.078 to +0.099 ‰) and those from sediments-dominated islands like Uracas and Agrigan (δ186/184W = +0.080 to +0.111 ‰). The W isotopic compositions of sediments off-board the Mariana arc are more variable, with the volcaniclastic sediments having δ186/184W values closest to those of the sediment dominated arc lavas. We show that rutile from representative subducting mafic crust incorporates isotopically light W, consistent with a coordination change from tetrahedral in fluids and melts to octahedral in the structure of rutile. We suggest that isotopically heavy fluids, complementary to the residual rutile in the mafic crust, account for the high δ186/184W of the fluid-dominated Guguan lavas, a process previously invoked to control Mo systematics in the same samples. Combining our new elemental and isotopic W data with these existing Mo data, we model the influence of oxygen fugacity on fluid compositions in equilibrium with the mafic crust, and the fraction of such fluids required to be added to the mantle wedge to reproduce the Mo-W systematics of erupted arc lavas. Our models show that more fluid is required (F = 6%) than can be generated internally in the mafic oceanic crust, and that this fluid must be oxidised, perhaps as high as ΔFMQ +5. We suggest that these requirements document the interaction of subducted mafic crust with an external source of oxidising fluids sourced from dehydration of underlying serpentinites.
... We have examined samples from two wellcharacterized metaophiolite complexes (Table 1; Supplementary Table 1). The Raspas Complex, Ecuador, contains metasediments, blueschists, eclogites, and eclogite-facies, serpentinised peridotite, which all experienced similar peak pressure-temperature conditions of~2 GPa and 600 ± 50°C 22,23 . The Cabo Ortegal Complex eclogites record comparable peak metamorphic conditions of 650-670°C, using Zr-in-rutile data from Schmidt et al. 24 in combination with a temperature calibration from Ferry and Watson 25 and pressures > 1.7 GPa 26 . ...
... Fortunately, the temperature and oxygen fugacity (fO 2 ) dependence of solubility of Mo in fluids at appropriate sub-arc conditions have been experimentally calibrated 15 . Since the temperature of rutile equilibration is independently monitored by its Zr concentration 24 or other thermobarometry 22,23 , our data allow us to examine the fO 2 of the fluids that transported Mo from the eclogites. Admittedly, we also need to stipulate residual mineralogy and fluid salinity, but these are sufficiently well constrained for the sensitivity of the calculation to these parameters. ...
Fluids liberated from subducting slabs are critical in global geochemical cycles. We investigate the behaviour of Mo during slab dehydration using two suites of exhumed fragments of subducted, oceanic lithosphere. Our samples display a positive correlation of δ98/95MoNIST 3134 with Mo/Ce, from compositions close to typical mantle (−0.2‰ and 0.03, respectively) to very low values of both δ98/95MoNIST 3134 (−1‰) and Mo/Ce (0.002). Together with new, experimental data, we show that molybdenum isotopic fractionation is driven by preference of heavier Mo isotopes for a fluid phase over rutile, the dominant mineral host of Mo in eclogites. Moreover, the strongly perturbed δ98/95MoNIST 3134 and Mo/Ce of our samples requires that they experienced a large flux of oxidised fluid. This is consistent with channelised, reactive fluid flow through the subducted crust, following dehydration of the underlying, serpentinised slab mantle. The high δ98/95MoNIST 3134 of some arc lavas is the complement to this process.
... Metapelites with the typical mineral assemblage garnet + kyanite + chloritoid + phengite + quartz + rutile are also distributed in other orogenic belts, such as the Eastern Alps (Smye et al., 2010), Carpathians (Negulescu et al., 2009), Western Alps (Zucali et al., 2002), Andes (Gabriele et al., 2003), the Chuacus Massif (Maldonado et al., 2018) and the Bohemian Massif (Konopásek, 2001). Those metapelites usually contain a peak assemblage of g + ky + ctd + ph + q + ru, and most of them yield HP-LT peak conditions of 20.3-26.2 ...
As the products of early Paleozoic continental collision, widespread eclogite facies rocks crop out in the Yuka terrane, western North Qaidam Mountains, NW China. Eclogites commonly reach ultrahigh pressure (UHP) metamorphic conditions. However, whether the associated metapelitic rocks also experience UHP metamorphism has not been thoroughly elucidated to date. In this contribution, we chose two eclogite samples and one metapelite sample to investigate their metamorphic evolution. Combining with petrographic observation and P–T pseudosections, similar clockwise P–T paths with peak stages at 25–34 kbar, 580–633 °C were obtained for eclogites and metapelites. Eclogite ZM871 records a prograde metamorphic condition at 21.6 kbar/552 °C, defined by the assemblage garnet + omphacite + epidote + lawsonite + talc (+quartz + phengite + rutile) and a peak metamorphic condition at 34.0 kbar/633 °C by the assemblage garnet + omphacite + lawsonite + talc (+coesite + phengite + rutile). Eclogite ZM641 records a prograde metamorphic condition at 21.5 kbar/520 °C, defined by the assemblage garnet + omphacite + glaucophane + lawsonite (+quartz + phengite + rutile) and a peak condition at 30 kbar/616 °C by the assemblage garnet + omphacite + lawsonite + talc (+quartz + phengite + rutile). Metapelite ZM8–1 records a prograde metamorphic condition at 18.2 kbar/530 °C defined by the assemblage garnet + chloritoid + chlorite (+quartz + phengite + rutile), a peak condition at 25 kbar/580 °C by the assemblage garnet + kyanite + chloritoid (+quartz + phengite + rutile), and a retrograde condition at 16.2 kbar/595–598 °C by the assemblage garnet + kyanite + chloritoid + chlorite (+quartz + phengite + rutile). Combined with previous data from orthogneiss and impure marble in the Yuka terrane, which also recorded UHP metamorphic conditions, the Yuka eclogite–bearing unit commonly underwent UHP metamorphism, although further investigation is warranted to verify whether the Yuka unit represents a single coherent UHP metamorphic terrane or a collage of different UHP metamorphic slices.
... From south to north, the EOMC has been traditionally subdivided into three independent tectono-metamorphic units (e.g. Gabriele et al., 2003;Riel et al., 2014). ...
The El Oro Metamorphic Complex (EOMC) in SW Ecuador has been the subject of debate for several decades. While previous studies have focused on the metamorphic and deformation history of the complex to determine its geodynamic evolution, the pre-metamorphic history and its association to units in the north-central Andes remains poorly understood. Here we present a U-Pb detrital zircon provenance study to provide insights into the depositional history and the geodynamic setting of the EOMC. Our results imply that the southern portion of the EOMC (the Tahuín division) is composed of an older Palaeozoic (pre-Famatinian) sequence in the south (El Tigre unit; c. 525-510 Ma), and younger Palaeozoic (post-Famatinian) sediments in the central and northern parts of the Tahuín division (La Victoria and La Bocana units; c. 370-360 Ma). The provenance of the sedimentary sequences correlates with autochthonous post-Famatinian units (440–340 Ma) in the Eastern Cordillera of Peru and the southern Cordillera Real of Ecuador. Importantly, our data provide evidence for a genetic link between the northernmost (the Birón Complex) and the southern (La Victoria and La Bocana units) sequences of the EOMC. Post-Famatinian sediments were identified in the Birón Complex (Palenque Mélange division; c. 400-390 Ma) and are derived from the same sedimentary sources as the sediments of the southern EOMC. The depositional range of post-Famatinian sediments in the EOMC is therefore constrained to c. 400-360 Ma. Furthermore, we identified a Middle to Upper Triassic sedimentary sequence in the Birón Complex (Limón Playa unit; c. 240-215 Ma) that likely developed contemporaneously with c. 240–217 Ma syn-rift continental epiclastics of the Mitu Group in Peru. Combined, these new detrital zircon data demonstrate that the existing lithostratigraphic scheme is erroneous and that three temporally distinct sequences are present in the complex, with the oldest units in the south and the youngest in the north. Separation of the southern EOMC (the Tahuín division) from the autochthonous Gondwanan margin of the north-central Andes was likely due to a change in the regional subduction direction from SE to ENE at c. 140Ma, with the southern EOMC rotating in a clockwise direction into its present-day E–W orientation. This rotation also could have been a response to the first accretion of proto-Caribbean terranes, such as the Alao–Quebradagrande terrane at c. 120 Ma, with a maximum age for rotation constrained by the earliest sediments (Early (?) to Middle Albian, c. 113-105 Ma) arriving into the Celica-Lancones Basin, which unconformably overlie the Tahuín Group in the southern EOMC.
... In contrast, the blueschists exhibit seamount-like characteristics, which can be explained by the mixing of a depleted mantle source (MORB-like) with an enriched one (OIB-like) and mantle melting at shallow depths (John et al., 2010b;Halama et al., 2010Halama et al., , 2011. Peak metamorphic conditions in the eclogites and blueschists were similar and all reached $1.8 GPa and $600°C at around 130 Ma, which suggests that they were subducted together as an essentially complete section within the slab (Gabriele et al., 2003;John et al., 2010b). Modal abundances and mineral compositions for the MORB-type eclogites and blueschists were published by John et al. (2010b), Halama et al. (2010Halama et al. ( , 2011 and Herms et al. (2012). ...
Thallium (Tl) isotope compositions of ocean island basalts (OIBs) have been proposed as a novel tracer of subducted oceanic crust and sediments in ocean island basalt sources, which could act as direct confirmation that deep mantle recycling eventually resurfaces through mantle upwelling to form ocean island basalt magmatism. However, it is unknown if oceanic crust that went through an active subduction zone would retain the Tl isotope compositions recorded in hydrothermally altered oceanic crust and authigenic marine sediments. In this study we present Tl isotope and concentration data for samples of subducted oceanic crust from five different locations: Zambezi Belt, Zambia; Cabo Ortegal complex, Iberian Massif, Spain; Raspas Complex, southwest Ecuador; Syros island, Cyclades, Greece; Tian Shan, northwest China. Thallium concentrations in most samples follow strong linear relationships with K, Rb, Cs and Ba, which strongly suggest that the mineral phengite is the primary control of Tl abundances in subducted oceanic crust. This conclusion is consistent with recent Tl data sets for arc lavas that imply residual phengite in the arc lava source regions as a strong control of Tl recycling. We find that Tl isotope compositions vary widely and systematically in each location depending on the protolith, metamorphic and metasomatic history of the samples. Samples from Cabo Ortegal and Raspas Complex reveal Tl isotope compositions similar to their protoliths, which were comprised of low-temperature altered oceanic crust. Tian Shan metamorphic rocks and Zambian eclogites reveal invariant Tl isotope values indistinguishable from average mantle, which is best explained by overprinting by metamorphic fluids that contained high concentrations of Tl and other alkali metals. Samples from Syros reveal a range of Tl isotope compositions from normal mantle towards values for pelagic clay sediments. The sediment-like values in Syros likely arose from fluids released from the surrounding mélange matrix that consists of serpentinite, metagabbros and metasediments. Each of the three Tl isotope ranges observed for subducted oceanic crust samples here are mirrored by individual OIB locations. Cabo Ortegal and Raspas Complex display Tl isotope compositions identical to St. Helena, suggesting that the HIMU component likely comprises subduction modified low-temperature altered oceanic crust. Thallium isotope ratios in Zambia and Tian Shan eclogites and blueschists are identical to lavas from Iceland, whereas Syros metamorphic rocks overlap almost exactly with lavas from Hawaii. Our data, therefore, show that Tl isotope compositions of oceanic crust and sediments can be traced through the subduction process and eventually is expressed largely unmodified in ocean island basalts.
... The chloritoid + kyanite + garnet mineral assemblage is known as indicating eclogitic conditions in a narrow temperature range (550-600 °C between 18 and 25 kbar) (e.g. Stöckhert et al. 1997;Gabriele et al. 2003;Negulescu et al. 2009;Smye et al. 2010;Hoschek et al. 2010;Hoschek 2013), likewise corresponding to subduction zone gradients between 7 and 12 °C/km. This assemblage, identified in HP metapelites, is considered by Smye et al. (2010) as favoured particularly by high Al 2 O 3 :K 2 O ratios of the bulk rock allowing the formation of kyanite in addition to garnet and chloritoid. ...
Chloritoid-bearing micaschist occurs in the matrix of a subduction mélange (Bughea Complex) of the Leaota Massif (South Carpathians) containing blocks of high-pressure rocks such as eclogite and metagabbronorite. Chloritoid is Mg rich and exclusively enclosed together with chlorite, epidote, paragonite, phengite, quartz, and rutile in mm-sized garnet porphyroblasts embedded in a matrix rich in white mica and chlorite. The Mg content of chloritoid inclusions systematically increases outwards from the inner core of garnet porphyroblasts. Modelling using a pressure (P) — temperature (T) pseudosection predicts the growth of chloritoid together with garnet at the expense of chlorite and other Al-rich phases, while following a nearly isothermal P-T path from 13 kbar and 540 °C to 21 kbar and 560 °C. Breakdown of chloritoid occurred along a P-T path characterised by heating and decompression to 600 °C and 15 kbar. The constrained P-T path is compatible with previously determined ones for eclogites in the Bughea Complex, namely burial in a subduction-accretion complex to depths of 70 km, detachment from the subducting slab, tectonic mixing with blocks sampled from different depths, and, thus, exhumation in a subduction channel.
