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Lower Miocene plutons exposed in the Western Cordillera of Colombia record the reinitiation of continental arc magmatism in the Northern Andes after a period of magmatic quiescence between the Late Eocene and Early Miocene. Petrography, U-Pb zircon geochronology, whole-rock geochemistry, mineral chemistry, and zircon Hf isotope data from these plutons are used to reconstruct the Miocene magmatic evolution in the Colombian Andes and understand its relation with the major plate-tectonic reorganization experienced by the NW South American continental margin during the Lower Miocene. We examined a suite of gabbros, granodiorites and tonalites from Danubio, Pance and Tatamá plutons, formed between 21 Ma and 15 Ma. Gabbros present highly positive εHf values (+13.5 and + 11.5) with low Th/La and La/Yb ratios, and granodiorites and tonalites present lower εHf values (+14.3 to + 6.4). The results of this contribution show a major asthenospheric source with absent or minor melting of subducted sediments, and contribution of oxidized aqueous fluids. The compositional diversification of these magmas was controlled by fractional crystallization and, in the Tatamá pluton, also by local assimilation of continental crust at lower crustal levels of the upper plate. Subsequently, these magmas were emplaced in the Cretaceous to Palaeogene volcanic and sedimentary rocks in the uppermost crust. The renewed magmatic activity recorded by the studied plutons suggests a normal to step subduction of the elder Farallon Plate during the Neogene subduction re-organization in the Colombian Andes, as well as the local presence of continental crust fragments in the lower crust of the Western Cordillera of Colombia. [ABSTRACT FROM AUTHOR]

The continental lower crust constitutes a key zone for understanding the mantle–crust magmatic and mechanical transfers, but its study is hampered by the paucity of lower crust samples. Here, we characterise the petrological, geochemical and petrophysical processes structuring the lower crust of the North Patagonian Massif (NPM; Argentina) using a suite of representative mafic granulite and websterite xenoliths. These xenoliths were entrained by alkaline lavas from five volcanic centres that erupted between the Oligocene and Pleistocene. Electron microprobe and Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS) were used to obtain in situ geochemical data on the minerals, while microstructural data were obtained by Electron BackScatter Diffraction (EBSD). Both granulites and websterites display a granoblastic texture and sometimes a weak inherited magmatic layering. Mafic granulite xenoliths show a plagioclase + clinopyroxene ± orthopyroxene assemblage commonly associated with spinel or titanomagnetite. Websterite xenoliths show an association of clinopyroxene + orthopyroxene + spinel, along with accessory plagioclase. Mafic granulites and websterites have SiO2 contents ranging from 44 to 53 wt %, while their Mg# varies from 53 to 79. Clinopyroxenes are characterised by weak convex upward chondrite-normalised Rare Earth Elements - REE patterns (Light-REE  Heavy-REE) which are similar to clinopyroxene phenocrysts and megacrysts from intra-plate basalts. Calculated liquid in equilibrium with clinopyroxene have similar REE patterns to those found in Cenozoic basalts from the NPM, suggesting that the xenolith suite represents evidence for underplating processes, possibly related to one of the magmatic events that have occurred in the NPM since the Permo-Trias. Mafic granulites and websterites show a weak mineral shape preferred orientation and an associated weak Crystal Preferred Orientation (CPO) related to the magmatic layering. Recorded plastic deformation is associated with the activation of both (100)[001] and (001)[100] slip systems in clinopyroxene, (100)[001] in orthopyroxene and (010)[001] in plagioclase. However, the activation of slip systems is generally not correlated with CPO in granulites, suggesting that the lower crust underwent subsolidus equilibration and weak plastic deformation in an inactive tectonic context, thereby preserving an inherited magmatic layering. Two-pyroxene (Fe–Mg) thermometer and pseudosection calculations define P–T conditions of the main paragenesis at 760°C to 1120°C and 7.2 to 10.3 kbar, which allows to define the Cenozoic geotherm of the NPM crust at 30°C/km and to reconsider the petrologic Moho depth at ca. 40 km. [ABSTRACT FROM AUTHOR]

IntroductionMineral chemistry has a significant role in determining the stages of magma evolution. Amphiboles, Biotite, plagioclase, and chlorite are minerals whose chemical composition show the temperature and pressure conditions of magma. These minerals are often used for the petrogenesis of granitoid bodies and record the characteristics and geochemical features as well as tectonic conditions of the producing magma (Abdel-Rahman, 1994; Nachit et al., 2005). The granitoid bodies of west Yazd have wide outcrops with different compositions. These rocks are part of the volcano-plutonic belt of Central Iran (Aftabi and Atapour, 2000) with calc-alkaline nature, meta luminous, and mostly of I-type (Hassanzade et al., 2002). The Hamaneh monzogranite bodies, with light color and dark enclaves, are located in 45 km at E53°48ˊ to E53°58ˊ longitude and N31°50ˊ to N31°56ˊ latitude. This area is part of the Shirkuh Mountain in Yazd with a northeast-southwest trend. Hamaneh monzogranite belongs to the Oligocene magmatic activity. In the present research, the mineral chemistry of amphibole, biotite, plagioclase, and chlorite has been investigated to determine the origin and stages of formation and evolution of the magma.Regional GeologyThe studied area geologically located in the middle part of the Urmia-Dokhtar magmatic zonewith a wide collection of Cenozoic magmatic rocks and is characterized by a length of about 2000 km, and a width of approximately 50 to 150 km, parallel to the metamorphosed zones of Sanandaj-Sirjan and Zagros, has a wide collection of Cenozoic magmatic rocks. This area has witnessed extensive magmatic activity in the Cenozoic, especially in the Eocene, which during the Oligocene-Miocene hosted numerous intrusive masses with different ages and compositions (Hassanzadeh et al., 2002). The oldest formation in the region is the green siltstone shale and sandstone of the Kahar Formation. The dolomitic rocks of the Soltanieh Formation are unconformably on the Kaher Formation with purple and cream-colored sand shale layers. The Permian sediments (Jamal Formation) composed of limestone and dolomite layers and the Mesozoic sediments started with a dark unit of volcanic laterite rocks with the Lower Triassic followed by dolomitic rocks belonging to the Otri Formation. The shale and sandstone of the Shemshak Formation are upper Triassic sediments. Cretaceous sediments are exposed in the form of destructive rocks. Upper Triassic (Sangestan Formation) has a variety of conglomerate and conglomerate sandstones with round to semi-round pieces of sandstone and Shirkuh granite. The Paleogene begins with the Kerman Formation conglomerate. Then, there are alluvial cones, alluvial plains, and alluviums of young rivers.Analytical methodsFor the lithology and chemistry of minerals in Hamaneh monzogranite, 20 thin-section samples were selected for chemical analysis of amphibole, plagioclase, biotite, and chlorite minerals and sent to Oklahoma City University laboratory. Microprobe analyses were performed with the Cameca model SX100 device with an accelerating voltage of 15 KV and current intensity of 15 nA. The results of chemical data of amphibole, biotite, feldspar, and chlorite minerals are given in Tables 1 to 4.Petrography and Minerals ChemistryIt is often fine to medium grain texture, granophyric and perthitic texture. The main minerals are orthoclase, plagioclase, and quartz. Orthoclase with an abundance of 25 to 32% is amorphous to semi-amorphous, and plagioclase is a frequency of 24 to 44% that was often as shaped to semi-shaped with zoning. The quartzes are often amorphous and intergranular, and some have wave extinction and fractures with a frequency of 19 to 31. The minor minerals were amphibole, biotite, sphene, zircon, and opaque minerals. Amphibole is green with an abundance of 2.5 to 4.5%, shaped to semi-shaped with a simple twinning. Biotite crystals with an abundance of 2 to 4%. Mineral chemistry of amphiboles was shown as calcic magmatic amphiboles, ranging from magneiso-hornblende and actinolite. Which formed at 530-890℃ and up to 4.3 kbars. That was shown depth 3 to 5.40 km and fO2 (0.5).

We present a petrologic study of the post-collapse rhyolites from Valles Caldera (New Mexico, USA) to evaluate changes in magmatic storage conditions following the eruption of the Upper Bandelier Tuff (UBT). We assess likely phenocrysts through textures, comparison with experiments, and rhyolite-MELTS outputs, and apply thermobarometers, oxygen barometers, and hygrometers to these minerals. The post-collapse rhyolites have average pre-eruptive temperatures ranging from 742–824 °C, average pre-eruptive oxygen fugacities ranging from –0.1 to +1.3 ΔNNO, and average pre-eruptive H2O contents ranging from 4.4–6.0 wt% H2O. Average storage pressures range from 130–196 MPa for all rhyolites except the youngest, which has a range of 157–376 MPa. The post-collapse rhyolites are more oxidizing than the UBT and have similar pre-eruptive pressures. The change in oxidation state between the rhyolites and UBT, despite similar storage pressures, can be explained if the UBT is generated from a unique, reduced source but accumulated at depths similar to the post-collapse rhyolites.

Experimentally calibrated models to recover pressures and temperatures of magmas are widely used in igneous petrology. However, large errors, especially in barometry, limit the capacity of these models to resolve the architecture of crustal igneous systems. Here, we apply machine learning to a large experimental database to calibrate new regression models that recover P–T of magmas based on melt composition plus associated phase assemblage. The method is applicable to compositions from basalt to rhyolite, pressures from 0.2 to 15 kbar, and temperatures of 675°C to 1400°C. Testing and optimisation of the model with a filter that removes estimates with standard deviation above the 50th percentile show that pressures can be recovered with root-mean-square-error (RMSE) of 1.1 to 1.3 kbar and errors on temperature estimates of 21°C. Our findings demonstrate that, given constraints on the coexisting mineral assemblage, melt chemistry is a reliable recorder of magmatic variables. This is a consequence of the relatively low thermodynamic variance of natural magma compositions despite their relatively large number of constituent oxide components. We apply our model to two contrasting cases with well-constrained geophysical information: Mount St. Helens volcano (USA), and Askja caldera in Iceland. Dacite whole-rocks from Mount St Helens erupted 1980 to 1986, inferred to represent liquids extracted from cpx–hbl–opx–plag–mt–ilm mush, yield melt extraction source pressures of 5.1 to 6.7 kbar in excellent agreement with geophysical constraints. Melt inclusions and matrix glasses record lower pressures (0.7–3.8 kbar), consistent with magma crystallisation within the upper reaches of the imaged geophysical anomaly and during ascent. Magma reservoir depth estimates for historical eruptions from Askja match the location of seismic wave speed anomalies. Vp/Vs anomalies at 5 to 10 km depth correspond to hot (~990°C) rhyolite source regions, while basaltic magmas (~1120°C) were stored at 7 to 17 km depth under the caldera. These examples illustrate how our model can link petrology and geophysics to better constrain the architecture of volcanic feeding systems. Our model (MagMaTaB) is accessible through a user-friendly web application (https://igdrasil.shinyapps.io/MagmaTaBv4/). [ABSTRACT FROM AUTHOR]

Granites are one of the most abundant rock groups formed the continental crust, and are considered for investigating the temperature conditions of their formation and metamorphism. Thus, they are a unique window to magmatism and tectonic evolution of the earth. The S-type granites are considered to be the result of crustal shearing in collision zones in the course of orogenic processes and high degrees of metamorphism (von Huene and Scholl, 1991; Brown, 2013; Hu et al., 2018). The granite might be affected and change into metagranite by further metamorphic deformations in the orogenic zones during or following the magma crystallization and emplacement of granitic melts in the continental crust. The mineralogical and textural characteristics of metagranites have a key role in understanding tectonic events and metamorphic temperature conditions and provide valuable information regarding the geological processes and Paleozoic tectonic events in the northern part of the Central-East Iranian microcontinent (CEIM).The main goal of the present paper is to investigate the high temperature-pressure metamorphism and deformation related to the of closure the Proto-Tethys oceanic crust and the opening of Paleo-Tethys oceanic crust in the north of the Central-EastIranian microcontinent, based on the petrography and mineral chemistry of Airakan metagranite. Geological BackgroundIn late Ediacaran, the Proto-Tethys Ocean between Proto-Gandwana and Proto-Laurasia opened (Raumer et al., 2015; Rossetti et al., 2015). Following several metamorphic events, the Proto-Tethys Ocean closure occurred at late Ordovician to early Carboniferous, and led the Precambrian terrains of Iran to collide and re-joint to form the Gondwana supercontinent (Raumer et al., 2015; Rossetti et al., 2015; Moghadam et al., 2017).Iran is a part of the western lands of the Gondwana supercontinent, moved to Eurasia in the early Permian-Triassic and following the Cimmerian orogeny, and then, with the Alpine-Himalayan orogeny event, until now, it has undergone several complex metamorphic, igneous, and tectonic processes, and various structural and geological zones have emerged in the land of Iran.Central-East Iranian microcontinent is composed of four main Pan-African continental plates, including (from east to west) Lut block, Tabas block, Posht-Badam block, and Yazd block. Airakan granite is a deformed and fractured Ordovician granite, exposed among the Miocene Upper Red Formation to the north of the Khor area in Yazd block (Northeastern Isfahan Province, Central Iran) (Shirdashtzadeh et al., 2018). The overall textural and mineralogical characteristics of the study granite point to its deformed/metamorphosed following the post magmatic metamorphic processes at sub-solidus temperatures (Bagheri and Stampfli, 2008; Shirdashtzadeh et al., 2018). U-Pb zircon dating (Shirdashtzadeh et al., 2018), revealed the Ordovician age (487.6 Ma) for the Airakan granite. The occurrence of Ordovician magmatism has also been reported in the other parts of the Gondwanan continental crust of Iran, Pakistan, and Tibet (e.g., Hu et al., 2015; Moghadam and Stern 2015; Naeem et al., 2016; Moghadam et al., 2018; Khodami et al., 2022; Samadi et al., 2022).Analytical MethodsFollowing the microscopic observations, the selected thin sections were used for electron microprobe analysis of minerals using a JEOL JXA8800R device at an accelerating voltage of 15 kV and a current beam of 15 nanoamperes at Kanazawa University, Japan.Discussion A) High P-T Metamorphism related to Proto-Tethys Ocean closure Thermobarometry data based on the mineral chemistry (and the whole rock composition) indicate that the Airakan S-type granite was a result of greywacke anatectic melting, due to an Ordovician HPT metamorphism. This HPT metamorphism has occurred during the closure of Proto-Tethys ocean. Consequently, collision between the Gondwana and Eurasia supercontinents has resulted in the continental crust thickening and anatectic melting. Similarly, several Ordovician anatectic S-type granites are reported from China (Hu et al., 2015), Pakistan (Naeem et al., 2016), and Central Iran (e.g., Moghadam et al., 2018; Khodami et al., 2022; Samadi et al., 2022).B) Metamorphic deformation related to Paleo-Tethys Ocean Opening A metamorphic deformation caused by the opennig of Paleo-Tethys Ocean in late Ordovician to early Devonian-Carboniferous (Bagheri and Stampfli 2008) has recorded in the Airakan metagranite in the north of CEIM. According to mica crystals orientation, metamorphic deformations of quartz (GBM recrystallization, subgrains formation and elongation, as well as preferential orientation or SSPO of quartz), and feldspars (formation of flame perthite parallel to the maximum stress (σ1), myrmekitization, tartan texture and BLG recrystallization around feldspars), in 382 Ma, the Airakan granite has undergone a metamorphic deformation at ~500 to 700 °C in a shear zone.ConclusionsGeothermobarometry results based on the mineral chemistry as well as the whole rock composition of Airakan metagranite indicate that a high temperature-pressure metamorphism has resulted in an anatexis event (dehydration of mica) at temperature of ~817-850℃. This event is consistent with the continental collision and of ancient continental crust thickening in the north of Yazd block during the closure of the Proto-Tethys Ocean starting from Greece to Iran and the Himalayas and, the Pan-African orogeny, from the Precambrian to the beginning of Ordovician.In addition, petrographic features (e.g., the flame perthite, myrmekite, and recrystallization of quartz and feldspars) show that Airakan granite has undergone an approximately high-grade metamorphic deformation in a deep shear zone at ~ 500-700 ℃. Based on previous geochronological data (382 Ma), it was a consequence of Paleo-Tethys evolution in the active continental margin of the southern Eurasia in Upper Devonian.

Hercynite-rich spinel is a typical mineral of both quartz-bearing and quartz-free metapelitic rocks that form under low-pressure high-temperature conditions in the granulite facies (Sengupta et al., 1991) or upper-amphibolite facies of regional and contact metamorphism (Pattison and Tracy, 1991). Temperature-pressure estimation of metamorphic terrains is necessary to understand how large-scale crust evolution has occurred. High-temperature phase equilibrium cannot be properly evaluated solely based on normal cationic couple geothermobarometers, as ferromagnesian cationic exchange undergoes processes related to retrogression during cooling after peak metamorphism. Instead, key mineral parageneses are preserved and standard petrogenetic grids study based on reaction textures and mineral chemistry can be very helpful in better estimating temperature pressure.Regional GeologyDorbeh's contact aureole is formed in West Azerbaijan province, south of Urmia, north of Oshnavieh, and the Sanandaj-Sirjan zone around Dorbeh diorite. The intrusion is one of the components of the Urmia Plutonic Complex (UPC) which is spread along with granites and alkali syenites/granites at the northwest end of the Sanandaj-Sirjan zone in the south of Urmia. This diorite intruded sedimentary units of shale and carbonate belonging to Permian to Triassic-Jurassic including the Doroud and Ruteh Formations and have metamorphosed them in contact aureole, causing hornfels and calc-silicate to sometimes scarn deposits in the area (Modjarrad and Mohamed, 2015). This intrusion is covered by Miocene units (Ghalamghash, 2009). The observed parageneses in Dorbeh aureole including Cld + Chl, Ctd + And, Alm + Cld, And+Alm, Hc+Alm, Chl + Hc + And + Sil, Alm + And + Sil, Alm + And + Sil + Hc. The peak metamorphism assemblage is Alm + And + Sil + Hc. The reactions responsible for the parageneses productions were introduced in the previous studies (Modjarrad and Mohamed, 2015).Materials and Methods 50 microscopic thin sections were prepared and petrographically examined. A reagent sample with the highest number of parageneses and experienced peak metamorphism was analyzed by JEOL JXA-8200 microprobes electron device for garnet, chlorite, chloritoid, spinel, iron oxide, aluminosilicate, and apatite at the University of Potsdam, Germany. For whole rock chemistry, several metapelite samples were analyzed by XRF at the ALS-Chemex Laboratory of Canada.Discussion and ConclusionsThe main purpose of the present paper is to investigate the parageneses, the mineral chemistry, and the temperature-pressure estimation in the metamorphic contact aureole around Dorbeh intrusive. This intrusion consists of amphibole, plagioclase, and clinopyroxene, is a part of the Urmia Intrusive Complex (UPC), and with dioritic composition was intruded the Upper Cretaceous into the Paleozoic pelitic and limestone sedimentary rocks and metamorphosed them. The metapelite section of the aureole has exhibited interesting parageneses due to the exceptional iron-rich composition of the protolith. The hornfels part of the Dorbeh aureole is dominated by chlorite + chloritoid + garnet + aluminosilicates + spinel + opaque minerals and less quartz in the matrix. Mineral chemistry studies showed that Fe-chlorite between Repidolite to Bronswigite, Fe-chloritoid, Almandine garnet, Hercynitic spinel, and ilmenite are the minerals composition which is in agreement with the Fe-rich content of the parent rock. There was no specific zoning pattern in the metapelites garnet grains. It was also found that there is a reverse relationship between Si content and iron, magnesium, titanium, and chromium in chlorite and aluminosilicate structures. The metamorphic conditions for Dorbeh aureole by the multi-equilibria method by THERMOCALC software have been estimated at 570±7°C, at a pressure of 2.8±0.2 kbar.Detailed investigation of phase relationships of metamorphic rocks can be considered a desirable method along with quantitative data-based methods to evaluate the occurrence of progressive metamorphism. This method is based on direct observation of reaction textures and is more objective in estimating metamorphic conditions by the method of the intersection of equilibrium reactions. Most of the time, secondary cationic exchanges penetrate from the mineral boundary to a considerable stratum and question the accuracy of the temperature and pressure calculated on the cationic couple's geothermometers to a large extent. The contact aureole with higher than normal temperatures specific to the margins of dry mafic intrusives is sometimes associated with the formation of special parageneses such as Grt+Sil+And+Hc. This paragenesis has also been reported from high-temperature (granolithic) regional metamorphic terrains, but its production conditions are more limited in contact aureoles and require a high molar fraction of iron/aluminum or mass dryness and/or aureole. Therefore, the composition of all ferromagnesian minerals is very close to the final iron end member and no specific temperature fluctuation in the aureole is understood from the garnet zoning pattern. Although staurolite has not been seen in the studied sections, the evidence suggests that hercynite in the area was caused by staurolite breakdown. With precision in the composition of analyzed chlorites, it was found that there is a direct relationship between Si and alkaline content in chlorite structure, but titano-ferromagnesian content is in contrast with Si content. An almost similar relationship was observed in the aluminosilicate crystals. The inverse relationship between silica and Fe, Ti, and Cr oxides prevails.

Although the evolution of residual melts in magmatic systems controls their eruptability and ore-forming potential, their compositions are obscured in plutonic rocks by a protracted near-solidus evolution and the absence of interstitial glass. Here, we trace the evolution of residual melt compositions in rocks from the Strontian Intrusive Complex, Scotland, using the trace element chemistry of amphiboles, and titanites which are intergrown with amphibole rims. Laser ablation mapping reveals an abrupt change in certain trace elements in the amphibole rims, with sharp increases in Eu/Eu* and Sr/Y, and decreases in rare earth elements, Ta, Nb, and Ta/Nb ratios. Core-rim variations in these elements in titanite show the same variations as in amphibole, but are more gradual. By reconstructing the crystallisation sequence of the Strontian magmas using textural observations and thermobarometric estimates, we determine that amphibole cores crystallised prior to titanite saturation, but amphibole rims crystallised simultaneously with titanite. Using the trace element composition of the mineral phases and their modal abundance in the rock, with comparison to the whole-rock chemistry, we determine that titanite hosts the majority of the rare earth and high field strength element budget of the rocks. We therefore propose that the onset of titanite crystallisation had a profound effect on the trace element composition of late-stage residual melts at Strontian, which were inherited by the amphibole rims and subsequent titanites. This is supported by Rayleigh fractional crystallisation modelling, which demonstrates that the composition of amphibole rims cannot be explained without the influence of titanite. We therefore show that the saturation of trace element-rich phases in magmas represents a significant geochemical event in the petrogenesis of intermediate to silicic magmas. This has implications for provenance studies that attempt to reconstruct bulk rock compositions from mineral compositions, as the residual melts from which those minerals crystallise can be driven to significantly different compositions from the host magma by late-stage accessory phase crystallisation. [ABSTRACT FROM AUTHOR]

We investigate the geology and petrology of Cumaçay, one of the Plio-Quaternary eruption centers of postcollisional volcanism in Eastern Turkey, using a combination of geochronology, bulk-rock geochemistry, thermobarometry, and thermodynamic simulations. Our new K-Ar ages reveal an age of 3.5-0.97 Ma for the eruptive products, which spread around an area of approximately 1000 km². Mineral-melt equilibria for olivine, orthopyroxene, clinopyroxene, and plagioclase allow estimation of crystallization pressures, and temperatures indicate two separate crustal storage of crystallization at 14-28 km and 5-15 km. The temperature estimation from diverse methods ranges from 954 °C to 1224 °C. Thermodynamic modelings using Magma Chamber Simulator (MCS) at a representative pressure (5 kbar) imply that the assimilation and crustal contamination (AFC) resulted in evolved melts with various SiO2 contents at mid to lower crustal depths. Calculated wide range of temperatures, compositional variety from evolved members, and MCS recharge simulation at a representative pressure (2.5 kbar) reveal that the magma mixing between contrasted melts characterizes the final chemical dispersal of the erupted lavas. [ABSTRACT FROM AUTHOR]

The Seghin metamorphic complex of ophiolitic mélange from the north Soghan, composed of metamorphic suites varying in protolith and metamorphic grade. The rock units of this complex have been metamorphosed under PT conditions of pumpellyite- actinolite, greenschist- Ep amphibolite and blueschist facies enclosed by a serpentinitic mélange. The pumpellyite- actinolite and greenschist- Ep amphibolite facies rocks display overprinted metamorphic evidences of blueschist facies as glaucophane overgrowth around actinolite and magnesiohornblende crystals. The average temperature and pressure calculated by thermocalc software and petrogenetic grids is 6- 7, 290- 350 and 11 Kb, 350 ˚C for pumpellyite- actinolite schist and blueschist samples, respectively. The relations of minerals transformation, thermobarometry calculations and the lawsonite preservation are in accordance with counter- clockwise metamorphic path. Generally, the metamorphic blocks of serpentinitic mélange with counter- clockwise PT path like Seghin complex are characteristics of long- lived subduction systems. During the onset of subduction event and attaining to blueschis facies, metamorphic path of down- going slab has passed through greenschist- Ep amphibolite facies. Then, the prograde metamorphic path extending across Pmp- Act subfacies owing to decreasing of geothermal gradient during maturity of subduction setting. Consequently, hairpin- like PT path is governed that is characteristic of Franciscan- type accretionary prisms.

In the Talesh area (western Alborz), a thick sedimentary- volcanic association formed in a littoral- deltaic environment during the Late Cretaceous. The extrusives comprise volcanoclastics (tuffs), lava flows (pillow and massive) and basic dykes. The lava flows are dominated by basalts. Basalts are petrographically diverse including clinopyroxene- and plagioclase- phyric suites. Clinopyroxene is chemically in the ranges of augite to diopside and plagioclase is labradorite to bytownite. Here, using clinopyroxene chemistry, we performed thermobarometry and hygrometry calculations. Thermometric results of different samples are in the ranges of 1000 to 1200 °C. Moreover, barometric calculations show pressure ranges of

Kareevlei is the first diamond mine to be hosted in a K-richterite- and leucite-bearing Kaapvaal lamproite (formerly termed Group II kimberlite). To constrain the petrogenesis and lithospheric setting of the Kareevlei Kaapvaal lamproites, we present petrography, groundmass mineral compositions, bulk-rock major and trace element concentrations and Sr Nd isotopes for 13 coherent-textured samples, along with garnet indicator mineral compositions and Ni-in-garnet thermobarometry. Two distinct mineralogical varieties of Kaapvaal lamproites are identified: (1) phlogopite-diopside olivine lamproites and (2) leucite-richterite olivine lamproites. Phlogopite macrocryst and microcryst laths have two distinct core populations, interpreted as xenocrysts from phlogopite peridotites and MARIDs, whereas rims represent crystallisation from the magma. The leucite-richterite lamproites are characterised by higher bulk-rock SiO 2 , Al 2 O 3, and Na 2 O, and lower MgO contents compared to the phlogopite-diopside lamproites. The two mineralogical varieties have distinct incompatible trace element concentrations, with the leucite-richterite samples having lower concentrations of light REEs (LREE: La = 656–828; Ce = 518–597; Nd = 234–261 times chondrite) compared to the phlogopite-diopside samples (La = 1125–1391; Ce = 817–1029; Nd = 333–415 times chondrite). Additionally, these two groups exhibit clear separation in trace element ratios, with higher La/Sm and Gd/Yb in the phlogopite-diopside lamproites, which is interpreted to represent formation by lower degrees of partial melting relative to the leucite-richterite lamproites. However, both lamproite varieties have similar 87Sr/86Sr i and 143Nd/144Nd i ratios, suggesting derivation from an isotopically homogeneous source in the SCLM. The indicator mineral suite at Kareevlei comprises, in decreasing abundances, oxides (predominantly ilmenite and chromite), garnet, corundum, and rare clinopyroxene. Garnets are largely eclogitic (59%) with only smaller proportions of peridotitic G9 (19%) and G10 (8%) garnets observed. Peridotitic garnet thermobarometry indicates a paleogeotherm with an estimated surface heat flux of ∼44.3–44.9 mW/m−2 and an estimated lithospheric thickness of ∼187–195 km, which is within error of the nearby highly diamondiferous Finsch Kaapvaal lamproite (cf. 192 ± 6 km). Single mineral garnet thermobarometry suggests that most peridotitic garnets at Kareevlei were sampled by the lamproite at relatively shallow depths above the diamond stability field. The dominance of eclogitic garnet and the absence of peridotitic garnet that equilibrated within diamond stability suggests that the high-value diamonds extracted from Kareevlei are predominantly eclogitic in origin. • Petrology of richterite- and leucite-bearing Kareevlei diamondiferous lamproites • Mineralogical / bulk-rock geochemistry related to variable degrees of partial melting • Indicator minerals suggest LAB at ±188 km • High-value diamonds likely eclogitic in origin [ABSTRACT FROM AUTHOR]

The cratonic basement in the Kabul district is dominated by gneiss, migmatite, schist, and amphibolite and is characterized by extensive outcrops. Orthopyroxene and garnet are the index minerals of some of the gneisse, hence, they are considered as charnockite. Biotite, quartz and feldspar are the rock-forming minerals of the migmatites and their modal abundances vary between melanosome and leucosome. The predominant minerals of the schistic samples are garnet, kyanite, quartz, feldspar, muscovite and biotite. Amphibole (pargasite), garnet and plagioclase are the essential minerals of amphibolitic samples. Based on thermocalc software, petrogenetic grade and conventional thermobarometers the calculated average pressure and temperature for charnockitic, schistic and garnet-amphibolitic samples are 7.03 kbar and 590 ℃, 9.94 kbar and 518 ℃ and 9.24 kbar, 664 ℃ respectively. The mineralogical paragenesis and the geothermal gradient resulted from thermobarometry calculations of metamorphic basement of the Kabul block is in accordance with metamorphic gradient of collisional orogenic belts. The cratonic basement of the Kabul block is possibly representing metamorphic rocks of the deep level of Proterozoic collisional orogenic belts during the formation of Columbia and Rodinia supercontinents.

Phenocrysts in volcanic rocks are recorders of magmatic processes that have occurred at depth before and during a volcanic eruption. Our petrological investigations of stratigraphically controlled tephrite and phonotephrite samples from the latest eruption of Fogo (Cape Verde Islands) aimed to reconstructing magma storage and transport. The dates of sample emplacement have been determined using satellite instrument – derived high resolution thermal infrared maps. All samples are strongly phyric and commonly contain complexly zoned clinopyroxene crystals and cumulate fragments. Clinopyroxenes from all samples exhibit 10–50 μm wide rim zones, inferred to have grown in a few days to weeks during the ongoing eruption as a consequence of H2O loss from the melt. Clinopyroxene-melt thermobarometry using tephrite groundmass compositions suggests that the rims formed at upper mantle pressures of around 600 MPa (21 km depth). This level is interpreted to reflect temporary reduction in magma ascent velocity by near-isobaric movement through a complex storage system. Previously, the tephrite magma had accumulated at a deeper level, possibly between 700 and 900 MPa as indicated by clinopyroxene cores (Mata et al., 2017). The cause for H2O loss initiating rim growth could be degassing after rise of the magma from the deeper level, or CO2 flushing by a carbonic fluid phase released at depth. Corresponding data from phonotephrites indicate last equilibration at around 440 MPa (16 km); the phonotephrite magma is inferred to be a residuum from an earlier magmatic event that was entrained by advancing tephrite. Microthermometry of CO2-dominated fluid inclusions in tephrite clinopyroxenes results in pressures of around 330 MPa (12 km), indicating another short pause in magma ascent in the lowermost crust. Rim zonations of olivine phenocrysts indicate that after leaving this final stalling zone, the magma ascended to the surface in less than half a day. In strong contrast to these petrological equilibration depths, seismic events precursory to the eruption were located at < 5 km below sea level, with only two exceptions at 17 and 21 km depth consistent with our barometry. Our results enhance the understanding of this potentially dangerous volcano, which helps to interpret future pre-eruptive unrest.

The Almogholagh plutonic body with about 10 km2 is located 15 km of West of Hamedan city and on the Sanandaj-Sirjan zone. The Almogholagh pluton consists of diorite and gabbroic diorite, monzodiorite, quartz monzodiorite, monzonite, quartz monzonite, syenite, quartz syenite and alkali granite. Intergranular and granular are common textures of these rocks. The igneous rocks of the Almogholagh pluton were injected in two periods in the Cretaceous (from 138 to 95 Ma). Syenites, Quartz syenites and alkali granites were infused in the second phase and the remaining rocks have developed in the first stage. The igneous rocks of the Almoghlagh pluton have the A-type granitoids creteria. The magma generating the Almogholagh igneous rocks is formed by low degree partial meting (~7%) from depleted mantle with a garnet-spinel lherzolite composition. Results of the amphibole and plagioclase in the quartz syenite and quartz monzonite thermobarometry show that the mean temperature of the Almogholagh pluton formation is ~715 oC and the mean of its pressure is 2.18 Kb. Textural and thermobarometry evidences suggest a shallow-level (~5 km) emplacement for the Almogholagh pluton.

The volcanic rocks of Kojid area (south of Lahijan) crop out in northern Alborz. They show mainly pillow structure with numerous cross-cutting dykes. Based on lithostratigraphic relationships and interpillow pelagic limestones, the volcanics are Late Cretaceous in age. The volcanics of Kojid area are predominantly basic in composition (olivine basalt and basalt) and minor more evolved suites such as trachyandesite and dacite. Olivine phenocrysts display forsterite (Fo) content of 63 to 83%. The phenocrystic and interstitial clinopyroxene crystals are augite to diopside in composition, with Na2O, Al2O3 and TiO2 contents of 0.24- 0.68, 2.3-6.53 and 1-5.1 wt.%, respectively. Furthermore, plagioclase is labradorite (An%= 51-68). The results of various geothermobarometric methods of clinopyroxene, plagioclase and olivine indicate good correlation with each other. Different thermometric calculations yielded temperatures in the range of 1100 to 1250 °C which are compatible with temperatures of basic melts. Moreover, clinopyroxene and plagioclase barometry of the phenocrysts (4 to 8 Kb) and interstitial phases (

In the Hamedan region, migmatitic rocks occur with various structures. In the Simin area (South Hamedan) stromatic and in the Darreh-Omar (Toyserkan) area ophtalmitic structures are abundant. Migmatites have been developed in a poly-metamorphic region. At least one regional metamorphism and two contact metamorphism by mafic and felsic intrusions occurred in the area. It seems that in the Darreh-Omar area contact metamorphism of mafic body leading to migmatization, But in the Simin area previous regional metamorphism and development of shear zones followed by contact metamorphism by felsic body. Therefore, in some areas, such as the Simin area, the migmatization may have occurred in more than one stage. These are consistent with recent geochronological studies of the Alvand plutonic body and surrounding metamorphic rocks. Index minerals of metapelites such as garnet (almandine), biotite (siderophyllite), staurolite, andalusite, sillimanite, kyanite, fibrolite, cordierite, plagioclase (andesine) and spinel (hercynite) are existing in these rocks. Field geology, petrographic and geochemical evidences suggest that different generations of staurolite, biotite and cordierite exist in metamorphic rocks of different grades in the Hamadan area. These minerals sometimes have been formed by progressive reactions and some other times from retrogressive reactions. A number of these phases have been formed at the peak of metamorphism and some others in later time. Based on thermometric cation-exchange method of garnet-biotite pair, using different calibrations, the obtained temperature using first-generation of biotites is 655 °C and temperature range of 529 °C for second-generation biotites. Cordierite-garnet thermometry indicates a temperature of 637 °C for related migmatitic rocks. In barometry with GPBQ system, calculated pressure for first-generation biotite is estimated to be about 3.9 kbar and for the second-generation biotite around 3.6 kbar.

In the central part of the Sanandaj-Sirjan zone, there is an ultramafic rock exposure (hornblendite and pyroxenite) adjacent to Molataleb felsic complex completely located between Azna and Aligoodarz towns. The ultramafic rocks are actually cumulates derived from boninitic magma. During Upper Triassic-Lower Jurassic time the boninitic magma has been originated from mantle wedge as the result of initiation of Neo-Tethys subduction. Later, when subduction was proceeding, the felsic rocks crystallized in Middle Jurassic. Major elements composition of olivine, pyroxene, amphibole and minor plagioclase from the ultramafic rocks reveals crystallization from a sub-alkaline to calc-alkaline magma in a subduction zone setting. Primary minerals have chemical characteristics typical of those derived from a magma with low oxygen fugacity. Different methods for minerals thermobarometry indicate that amphiboles crystallized in relatively low temperature (880°C) but crystallization condition of other minerals corresponds to higher temperatures (1000-1200°c). They were crystallized at pressure condition equal to 5.85 kbar corresponding to the depth of ~17 km. It is not common that a mantle wedge at the depth of ~17 km to be affected by such high thermal gradient during the normal subduction process. Asthenospheric flow around the subducting slab edge during subduction initiation can explain high thermal gradient prevailed the infant mantle wedge. This mechanism corresponds to the boninitic nature of the ultramafic rocks.

An estimate of TiO2 activity (aTiO2s!") is necessary for the application of trace-element thermo-barometry of magmatic systems where melts are typically undersaturated with respect to rutile/anatase. Experiments were performed in the system SiO2-Na2O-TiO2 to develop two independent methods of estimating aîic!t2"sat -- one based on the commonly applied rutile-saturation technique and another utilizing a novel Ti-in-tridymite thermometer. It is demonstrated that the rutile-saturation model can lead to an overestimate of amO^ relative to TiO2 activity calculated using the solubility of Ti in tridymite (SiO2) coexisting with rutile. Overestimation via the rutile-saturation technique is due to variations in the solubility mechanisms of Ti in the melt phase as a function of Ti content. In natural systems, overestimates of aTiO^®" will lead to an underestimation of crystallization temperatures by Ti-based trace-element thermobarometers. Although this study is not directly applicable to natural systems, it lays the groundwork for future research on natural composition magmas to constrain TiO2 activity in melts. [ABSTRACT FROM AUTHOR]

This paper presents the generation of metamorphic sole rocks through the detailed geochemical and petrographical analysis of field work carried out on the Kömürhan ophiolite. The metamorphic sole rocks of Kömürhan ophiolite are defined as amphibolite (Pl+Mg--Hbl+Ttn±Ap) plagioclase--amphibole schist (Pl+Mg--Hbl+Cpx+Ttn±Zrn±Ap), plagioclase--clinopyroxene--amphibole schist (Pl+Di+Mg--Hbl+Ttn±Ap), and epidote-- plagioclase amphibole schist (Ep+Pl+Mg--Hbl+Ttn±Ap±Qtz±Zrn). This research mainly reports comprehensive petrography and mineral chemistry analyses of metamorphic sole rocks of Kömürhan ophiolite of SAOB (Southeast Anatolian Orogenic Belt) together with a goal of presenting geothermobarometric examination and unravelling the mineral systematics. The metamorphic sole rocks have been observed as a thin slice and these rocks are seen at the base of the tectonites, metamorphosed in amphibolites facies throughout the intra--oceanic supra-subduction geodynamic environment. The Kömürhan ophiolite includes from the top to bottom volcanics, sheeted dike complex, isotropic gabbros cumulates, and tectonites and shows a complete oceanic lithospheric fragments. Analyses of mineral chemistry and petrography of metamorphic sole rocks have been used to exhibit the metamorphic processes of these rocks. Mineral chemistry analyses of pyroxene phenocrysts in the metamorphic sole rocks of Kömürhan ophiolite present similarities island arc tholeiite (IAT), proposing that protolith of the sole rocks was related to the supra-subduction geodynamic environment. The amphibolites were occurred by metamorphism of island arc tholeiite--type volcanics that separated from the front of the obducted ophiolite (Kömürhan ophiolite) and after that underplated. [ABSTRACT FROM AUTHOR]

Magma recharge into a differentiated reservoir is one of the main triggering mechanisms for explosive eruptions. Here we describe the petrology of the eruptive products of the last explosive eruption of Tutupaca volcano (southern Peru) in order to constrain the pre-eruptive physical conditions (P-T-XH2O) of the Tutupaca dacitic reservoir. We demonstrate that prior to the paroxysm, magma in the Tutupaca dacitic reservoir was at low temperature and high viscosity (735 ± 23 °C), with a mineral assemblage of plagioclase, low-Al amphibole, biotite, titanite, and Fe-Ti oxides, located at 8.8 ± 1.6 km depth (233 ± 43 MPa). The phenocrysts of the Tutupaca dacites show frequent disequilibrium textures such as reverse zonation, resorption zones, and overgrowth rims. These disequilibrium textures suggest a heating process induced by the recharge of a hotter magma into the dacitic reservoir. As a result, high-Al amphibole and relatively high-Ca plagioclase phenocryst rims and microlites were formed and record high temperatures from just before the eruption (840 ± 45 °C). Based on these data, we propose that the recent eruption of Tutupaca was triggered by the recharge of a hotter magma into a highly crystallized dacitic magma reservoir. As a result, the resident dacitic magma was reheated and remobilized by a self-mixing process. These magmatic processes induced an enhanced phase of dome growth that provoked destabilization of the NE flank, producing a debris avalanche and its accompanying pyroclastic density currents. [ABSTRACT FROM AUTHOR]

We constrain, for the first time, the storage conditions beneath recent (<5 Ma) volcanic edifices in Martinique Island, combining petrography, geochemistry, and thermobarometry. Specifically, we investigate Morne Jacob volcano (5.2–1.5 Ma), Pitons du Carbet complex (998 ka – 322 ka), Trois Îlets Volcanic field (2.35 Ma – 346 ka), and Mt. Conil – Mt. Pelée system (<550 ka). Lava samples range in composition from basalt to dacite, and in age from 4.1 Ma (Morne Jacob) to 1929 CE (Mount Pelée). For the last ∼5 Ma, the volcanoes in Martinique were fed by andesitic to dacitic magma stored in the upper 6 km of the crust, at temperatures between 900 and 1100 °C. These shallow reservoirs were frequently replenished and remobilized by basaltic and basaltic-andesite magmas originating from the lower crust with temperatures as high as 1200 °C. Erupted products contain simple to more complex mineral assemblages, and plagioclase phenocrysts exhibit textures and compositional profiles typical of antecrysts, identified as (1) normal, (2) oscillatory, (3) sieved, (4) resorbed core, and (5) resorbed rim. All complexes also show a crystallization gap in the middle crust (10–18 km). Trois Îlets, a distributed volcanic field, is the only complex that shows continuous crystallization through the entire crust, distinct magma batches and storage regions for each individual volcano. More importantly, we see drastic changes in terms of rock composition, storage conditions, and crystal populations in pre - and post – collapse lavas. Large flank collapse (> 5 km3) can induce decompression as large as 5 MPa in the upper crust and as low as 0.1 MPa down to 10–12 km. Such decompression magnitudes might be sufficient to enhance ascent of basaltic magma from depth, initiate dike intrusions in the mid to upper crust, and remobilize shallow silicic reservoirs. Such events are likely to initiate magma mixing in shallow reservoirs. This noteworthy eruption-triggering mechanism may lead to the incorporation of distinct crystal populations and subsequently contribute to heightened rates of eruption. In summary, the magma storage conditions and plumbing system architecture for the recent volcanoes in Martinique closely resemble those observed in other volcanoes within the Lesser Antilles Island Arc, such as Soufriere Hills Volcano or La Soufriere de Guadeloupe. These newly established correlations offer valuable insights that can aid in the assessment of potential future volcanic eruptions. • First estimates of temperatures and pressures for Martinique Pleistocene volcanoes. • Plagioclase equilibrium temperatures range from 969 to 1072 °C. • Plagioclase water content range from 3.1 to 6.5 H2O wt%. • Pyroxene temperatures and pressures range from 964 to 1175 °C and 0.1–8.2 kbar. • There is limited crystallization in the middle crustal layer under Martinique. [ABSTRACT FROM AUTHOR]

The garnet-amphibolites in Aliabad-Damagh area, occurs as layers and are enveloped by staurolite-schist. They composed predominantly of garnet, hornblende, feldspar (± muscovite and quartz) with titanite, epidote, ilmenite and graphite as accessory minerals. The euhedral garnet porphyroblasts mainly composed of almandine and grossular components, with normal compositional zoning. The hornblende crystals as prophyroblast or in the matrix, are magnesio- and ferro-hornblende (amphibole core) to tchermakitic-hornbelende (amphibole rim) in composition. Muscovites, if present, with minor phengite and paragonite components, are foliated forming minerals. Feldspars vary from pure K-feldspar to sanidine composition in the vicinity of hornblendes and oligoclase in matrix. Epidotes as pure clinozoisite to epidote, form small crystals inside hornblende or in the matrix. Using different thermobarometry methods, T and P estimated as 600-620 (± 25) °C and 5-6 (± 1) kbar, respectively. Calculated P-T-t path, considering core and rim composition of hornblendes, is in accordance with low-pressure (at the beginning of metamorphism) to medium-pressure type (at the end). Considering P-T-t path, metamorphism could occur during Neo-Tethys subduction and collision process in the Mesozoic time

The Ghaleh Yaghmesh plutonic massif is located the westernmost part of Yazd province and in the central part of the Urumieh – Dokhtar magmatic arc (UDMA). This massif with quartzdiorite, tonalite and granodiorite composition is Oligocene in age and intruded the volcanic and pyroclastic rocks including rhyolite, rhyodacite, and andesitic, as well as rhyodacitic and rhyolitic tuff belonging to the Eocene. Tonalite and granodiorite contain mafic microgranular enclaves with quartzdiorite composition. According to mineral chemistry, the plagioclases are oligoclase to labradorite in composition. The amphiboles have high magnesian and are calcic nature (magnesio-hornblende). The biotites from the tonalites are enriched in magnesian. Compositionally, clinopyroxene display augite and augite–diopside in quartz-diorite and enclaves respectively. Thermometery of the clinopyroxene and hornblende– plagioclase show 1100-1125°C and 730-900°C respectively. The pressure of the studied rocks, on the base of chemical data of magnesio-hornblende, ranges from 1.5 to 1.75 kbar, which is equal to the depth of about 5.5-6.5 km. The overall field, petrography and mineral chemistry data support the I-type calc-alkaline nature of the studied granitoid, which formed during high oxygen fugacity and volcanic arc, and subduction is suggested for its formation environment.

The Pliocene-Quaternary volcanics in NE Turkey are mainly hornblende-phyric trachyandesites having a narrow range of SiO2 from 61.88 to 63.00 wt.% and exhibiting adakitic signatures with their Na2O (3.67-4.27 wt.%), Al2O3 (16.19-16.80 wt.%), Y (14.1-16.5 ppm) contents and K2O/Na2O (0.87-1.12), Sr/Y (44.24-54.90), and La/Yb (36.80-43.88) ratios. Plagioclases as the main mineral phases show a wide range of compositions, and weak normal and reverse zoning. Hornblendes are generally edenite and pargasite (Mg#: 0.39-0.74). Clinopyroxenes are augite (Mg#: 0.58-0.76). Biotites have Mg# ranging from 0.45 to 0.66. The textural and compositional variations indicate disequilibrium crystallization possibly arising from magma mixing. The U-Pb zircon dating of the adakitic volcanics yielded 3.4-1.9 Ma. The studied rocks display moderate light rare earth element /heavy rare earth element ratios and enrichment in the lithophile element and depletion in high field strength element, implying that the parental magmas were derived from mantle sources previously enriched by slab-derived fluids and/or subducted sediments. The crystallization temperature and pressure estimations based on the clinopyroxene thermobarometry range from 1144 to 1186°C and from 3.92 to 7.97 kbar, respectively. Hornblende thermobarometry, oxygen fugacity, and hygrometer calculations yielded results as 908-993°C at a pressure of 2.87-5.22 kbar, water content of 4.4-8.4 wt.%, and relative oxygen fugacity (ΔNNO log units) of −0.6 to 0.9, respectively. Biotite thermobarometry suggests relatively higher oxygen fugacity conditions (10-13.33 to 10-17.60) at temperatures of 676-819°C and at pressures from 1.15 to 1.76 kbar. In the light of the obtained data and modelling, it can be concluded that the magmas of the adakitic volcanics were derived from enriched mantle source through relatively higher partial melting and experienced magma mixing with melts at the crustal level. Additionally, the fractional crystallization and assimilation-fractional crystallization processes may have played an important role during the evolution of the studied volcanics. [ABSTRACT FROM AUTHOR]

The chemical and petrological correlation of metamorphic nappes and klippes overlying the Proterozoic sedimentary units in the Kumaun Himalaya is still debated. The Ramgarh and Almora gneisses, not previously distinguished in the Askot Klippe, show distinct field, petrological and chemical signatures markedly similar to the tectonostratigraphic disposition of the Almora Nappe. A negative Eu anomaly in the Ramgarh granitic gneisses indicates lesser plagioclase fractionation while the Eu anomaly in the Almora pelitic gneisses is likely to have been controlled by feldspar crystallization in restites. During the anatexis at > 776°C temperature and >6.6 kbar pressure, the melt moved slightly away to its crystallization sites. The Rb/Sr ratio ∼0.54 and Nb ∼10 ppm is consistent with the granodioritic composition. The negative Sr anomaly in the underlying Ramgarh granitic gneisses indicates a distinct mantle derived source/plagioclase fractionation with a notable correspondence to other late orogenic granites, particularly the basement Ulleri gneisses from the Nepal Himalaya. Ramgarh gneisses plot in the late‐ and post‐COLG field. The Askot ensemble is likely to be the tectonometamorphically reworked basement, viz. the Ramgarh Group along with its metapelitic cover of the Almora Group, together comprising southward thrust remnants of the leading edge of the Indian Plate that collided with Tibet during the Tertiary Himalayan orogeny. [ABSTRACT FROM AUTHOR]

The 2015 eruption of Wolf volcano was one of the largest eruptions in the Galápagos Islands since the onset of routine satellite‐based volcano monitoring. It therefore provides an excellent opportunity to combine geophysical and petrological data, to place detailed constraints on the architecture and dynamics of subvolcanic systems in the western archipelago. We present new geodetic models that show that pre‐eruptive inflation at Wolf was caused by magma accumulation in a shallow flat‐topped reservoir at ~1.1 km, whereas edifice‐scale deformation during the eruption was related to a deflationary source at 6.1–8.8 km. Petrological observations suggest that the erupted material was derived from both a subvolcanic mush and a liquid‐rich magma body. Using a combination of olivine‐plagioclase‐augite‐melt (OPAM) and clinopyroxene‐melt barometry, we show that the majority of magma equilibration, crystallization, and mush entrainment occurred at a depth equal to or greater than the deep geodetic source, with little petrological evidence of material sourced from shallower levels. Hence, our multidisciplinary study does not support a fully transcrustal magmatic system beneath Wolf volcano before the 2015 eruption but instead indicates two discrete storage regions, with a small magma lens at shallow levels and the major zone of magma storage in the lower crust, from which most of the erupted material was sourced. A predominance of lower crustal magma storage has previously been thought typical of subvolcanic systems in the eastern Galápagos Archipelago, but our new data suggest that this may also occur beneath the more active volcanoes of the western archipelago. Key Points: Combined geophysical and petrological constraints provide a detailed picture of the subvolcanic architecture at Wolf volcanoWolf is underlain by two discrete magma storage regions: one within the edifice, the other in the lower crustAlmost all the magma ejected during the 2015 eruption of Wolf was derived from the lower crust [ABSTRACT FROM AUTHOR]

Many continental subduction complexes contain abundant granitic rocks coexisting with minor volumes of eclogite-facies rocks. Characterization of granitic protoliths is crucial to decipher the origin of subducted continental crust, whereas knowledge of its metamorphic evolution is required to constrain the mechanisms of burial and exhumation. In this work we present geochronological and petrological evidence that demonstrate the occurrence of a subducted Proterozoic to Late Triassic granitic basement in the Chuacús complex of central Guatemala. Metagranitoids exposed in this area are interlayered with eclogite and other high-pressure rocks, and their structure is considerably variable due to strain partitioning during deformation. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon data from two ferroan metagranites yield protolith crystallization ages of ca. 1.1 Ga and their trace-element abundances suggest an origin related to intraplate magmatism, while a high-silica, peraluminous metagranite is dated at 1.0 Ga and was probably originated by partial melting of a high-grade continental crust. On the other hand, two megacrystic to augen metagranitoids yield protolith crystallization ages of ca. 224 Ma, which are identical within errors to the protolith age of hosted eclogitic metabasites. Their high incompatible trace element abundances together with the observed spatial-temporal relationships with mafic protoliths suggest that Late Triassic bimodal magmatism in the Chuacús complex was probably originated in a within-plate setting. Regardless of their age or structure, the studied metagranites preserve evidences for high-pressure metamorphic equilibration, such as the occurrence of Ca-rich garnet ( X Ca up to 0.52) in association with phengite (Si contents of up to 3.4 pfu) and rutile. The integration of Zr-in-rutile thermometry and phengite barometry allows the peak metamorphic conditions to be constrained at ~640–680 °C and ~13 kbar. This pressure-temperature estimate indicates that metagranitoids underwent high-pressure metamorphism but equilibrated at significantly lower pressures than associated eclogite-facies rocks, and, therefore, they do not necessarily share a common high-pressure metamorphic evolution. The new data show that the Chuacús complex in the study area represents a Proterozoic (1.1–1.0 Ga) to Late Triassic (220 Ma) continental basement that was subducted, and consequently metamorphosed under high-pressure conditions, during the Cretaceous evolution of the North America-Caribbean plate boundary. [ABSTRACT FROM AUTHOR]

We present the results of physical properties, petrography, bulk chemistry, mineral compositions, phase relations modelling and Noble gases study of the meteorite El Pozo. The petrography and mineral compositions indicate that the meteorite is an L5 chondrite with a low shock stage of S2-S3. Heterogenous weathering was preferentially along shock structures. Thermobarometric calculations indicate thermal equilibrium conditions between 768 °C and 925 °C at ∼4 to 6 kb, which are substantially consistent with the petrological metamorphism type 5. A pseudosection phase diagram is relatively consistent with the mineral assemblage observed and PT conditions calculated. Temperature vs. f O 2 diagram shows that plagioclase compositional stability is very sensitive to Tschermack substitution in orthopyroxene, clinopyroxene and X An plagioclase during the high temperature metamorphic process. Based on noble gases He, Ne, Ar and K contents a cosmogenic exposure age CRE of 1.9 Myr was calculated. The 21 Ne would be totally cosmogenic, with no primordial Ne. The 21 Ne/ 22 Ne value (0.97) is higher than solar value. According to the cosmogenic Ne content, we argue that El Pozo chondrite originally had a pre-atmospheric mass of 9–10 kg, which would have been produced by a later collision after the recognized collision of the L-chondrite parent body ∼470 Ma ago. [ABSTRACT FROM AUTHOR]

A structural and petrochronological study was carried out in the southern part of the Belledonne crystalline massif. A first tectonometamorphic event, Dx, corresponds to the eastward thrusting of the Chamrousse ophiolitic complex characterized by a low-temperature–moderate-pressure metamorphism reaching 0.535 ± 0.045 GPa and 427.5 ± 17.5 °C. A subsequent D 1 deformation is defined by a penetrative S 1 foliation that mostly dips toward the west and displays an E–W- to NE–SW-trending mineral and stretching lineation L 1 . D 1 is associated with a top-to-the east shearing and is responsible for the crustal thickening accommodated by the eastward nappe stacking and the emplacement of the Chamrousse ophiolitic complex upon the Rioupéroux-Livet unit. This event is characterized by an amphibolite facies metamorphism (0.58 GPa ± 0.06; 608 ± 14 °C) that attains partial melting at the base of the nappe pile (0.78 ± 0.07 GPa; 680.5 ± 11.5 °C). LA-ICP-MS U-Pb dating of monazite grains from the mica schists of the Rioupéroux-Livet unit constrain the age of D 1 to 337 ± 7 Ma. The D 2 tectono-metamorphic event is characterized by NE–SW trending, upright to NE-verging synfolial folding. Folding associated with D 2 is pervasively developed in all lithotectonic units with the development of a steeply-dipping S 2 foliation. In particular, D 2 involves the uppermost weakly metamorphosed Taillefer unit. LA-ICP-MS U-Pb dating performed on detrital zircon grains shows that the Taillefer conglomerates was deposited during the Visean. A zircon SIMS U-Pb age of 352 ± 1 Ma from a plagioglase-rich leucocratic sill of the Rioupéroux-Livet unit is interpreted as the age of magmatic emplacement. Our results suggest that the D 2 event took place between 330 Ma and 310 Ma. We propose a new interpretation of the tectonometamorphic evolution of the southern part of the Belledonne massif, focusing on the Middle Carboniferous stages of the Variscan orogeny. [ABSTRACT FROM AUTHOR]

The deep structure and deformation mechanisms of the Longmen Shan thrust belt (Sichuan, China), at the eastern border of the Tibetan plateau, were largely debated after the devastating Mw 7.9 Wenchuan earthquake (2008). Recent geophysical studies and field investigations have been focused on the active motion of the major Beichuan fault, which ruptured during the earthquake. However, the total exhumation across the fault still remains unclear. In the hanging wall of the Beichuan fault, the South China block is exhumed in the Pengguan massif. Close to the Beichuan fault, the rocks of the Pengguan massif underwent greenschist facies metamorphism associated with brittle-ductile deformation. No metamorphism is observed in the footwall of the fault. In this study, we characterize and date the metamorphic history recorded in the hanging wall of the Beichuan fault in order to constrain the depth and timing of exhumation of the rocks of the Pengguan massif along the fault. A high-resolution petrological approach involving chemical analyses and X-ray maps was used to analyze the micrometric metamorphic minerals. The P-T conditions of the greenschist facies metamorphic event were estimated by an inverse multi-equilibrium thermodynamic approach. The results, 280 ± 30 °C and 7 ± 1 kbar, suggest that the rocks of the Pengguan massif were exhumed from ca. 20 km depth. Our results underline the importance of the thrusting component in the long-term behavior of the Beichuan fault and provide a minimal depth at which the fault is rooted. In situ laser ablation 40 Ar/ 39 Ar dating of metamorphic white mica revealed that the greenschist overprint occurred at 135–140 Ma. The Pengguan massif was therefore partially thrusted along the Beichuan fault during the Lower Cretaceous, long before the Eocene-Miocene exhumation phase which is well-constrained by low-temperature thermochronology. Our results provide the first independent depth information for the exhumation history of the Pengguan massif and reveal a previously undocumented Lower Cretaceous tectonic event that marks the onset of the thick-skinned deformation in the external domain of the Longmen Shan (East of the Wenchuan Fault). [ABSTRACT FROM AUTHOR]

The Rio Doce arc, developed between ca. 630 and 580 Ma, is composed of a series of plutonic bodies, which constitute its root (G1 supersuite). These represent a swarm of pre-collisional, calc-alkaline, magnesian, predominantly granodioritic to tonalitic plutons that experienced a prolonged period of anatexis and metamorphism during the transition to the syn-collisional stage (ca. 585 Ma) of the Araçuaí Orogen. The Estrela granitoid (ca. 606 ± 13 Ma) and its associated leucogranite (613 ± 10 Ma), detailed in this work through field, petrographic, lithogeochemical, isotopic, and geochronological data, represents a new contribution for the understanding of the G1 supersuite. The studied rocks exhibit granodioritic to tonalitic (Estrela granitoid) and syenogranitic (leucogranite) composition, emphasizing the character of an expanded calc-alkaline series. The Estrela granitoid exhibits negative εNd (t) (− 7.0 to − 9.2) and εHf (t) (− 4.7 to − 8.7) values, and intermediate ratios of 86Sr/87Sr (0.709473–0.710611), which together with the Mesoproterozoic to Paleoproterozoic T DM Nd model ages (1442–2206 Ma) point to a crustal source with possible contributions from mantle derived magmas. In addition, high values of Ba–Sr are identified in the Estrela granitoid, related to a mantle source previously enriched and/or to the participation of sediments in the source. Therefore, the interaction of a magma derived from the juvenile mantle wedge with basement rocks and possibly sediments carried by subduction is here proposed as the main source for the development of the pluton. This granitoid, as well as the other lithotypes present in the study area, present characteristics compatible with the formation in a subduction environment, being crystallized in intermediate to deep depths of the crust (22–25 km) at about 770 °C and in higher conditions of oxygen fugacity. • There are few works that approach the Estrela granitoid batholith. • Detailed mapping and petrography of the batholith. • Geothermobarometric calculations and physicochemical conditions during magma crystallization. • Unpublished isotopic and geochronological (U–Pb) data for the Estrela granitoid batholith. • Implications and updating of the regional evolutionary model. [ABSTRACT FROM AUTHOR]

The Cão Grande Formation (CGF) on the western plateau of Santo Antão is a sequence of four phonolitic tephras (Canudo Tephra, Cão Grande I Tephra, Cão Grande II Tephra and Furninha Tephra) produced by highly explosive eruptions that alternatingly originated from a basanitic - phonolitic and a nephelinitic - phonolitic magmatic system. Detailed stratigraphy and petrological investigations of each unit are used to demonstrate the unusual situation that two distinct highly evolved magmas differentiated contemporaneously in separate magmatic systems. Chemical thermobarometry suggests that both magmatic systems not only temporally co-existed, but also that their magma chambers resided close to each other at 7 to 16 km depth, beneath the western plateau of Santo Antão. However, the distinct melt and magma compositions indicate that both systems evolved independently. The only interaction between both magmatic systems was an injection of magma from the nephelinitic - phonolitic magmatic system into the Cão Grande II Tephra (CG II) phonolitic reservoir, which is associated to the basanitic - phonolitic magmatic system. Compositional zonations in the tephra deposits indicate that the eruptions of the CGF tapped stratified magma reservoirs that mainly resulted from crystal accumulation generating downward increasing magma density. However, the CG II tephras also show a significant gradient in melt (glass) compositions. Magmas of the Canudo Tephra (CT) and the Cão Grande I Tephra (CG I) were H 2 O-saturated and their eruptions were probably triggered by fluid overpressure in the magma chamber. On the other hand, the CG II magma was H 2 O-undersaturated; we therefore assume that the injection of the hot nephelinitic - phonolitic magma system-type melt/magma triggered the eruption. The zoned deposit of the Furninha Tephra (FT) indicates mafic magma replenishment into a phonolitic reservoir directly prior to the eruption, thus providing a probable triggering mechanism. The new magma chamber models and thermobarometric results for the four CGF units provide constraints for hazard assessments, because similar events may occur in the future considering the longevity of the CGF magma systems. [ABSTRACT FROM AUTHOR]

The lesser and greater Himalayan sequences ( LH and GH) in Sikkim have been studied in detail recently. The LH consists mainly of pelitic lithologies with detrital zircon ages >1800 Ma and εNd(0) of −27.7 to −23.4 (with intercalated calcsilicates, metabasites and a sheared granite gneiss - the Lingtse gneiss). The metamorphic sequence is characterized by (i) a remarkably continuous and systematic metamorphic field gradient (~60-70 °C kbar−1), (ii) peak pressures as well as temperatures of metamorphism increasing at higher metamorphic grades (~5 kbar, 500 °C at the garnet zone to ~8 kbar, 700 °C at the sillimanite-muscovite-zone), (iii) clockwise P- T paths of a tight 'hairpin' shape with a prograde slope of 20-30°C kbar−1, (iv) initiation of garnet growth (Lu-Hf chronometry) at systematically older ages at higher grades (11-10.5 Ma at garnet zone to 16.8 Ma at sillimanite-K-feldspar zone), (v) peak of metamorphism simultaneously at all grades (13-11 Ma), (vi) deformed and folded metapelitic rocks but with little evidence of pervasive shearing and (vii) duration of melt formation and segregation on the order of a few 100,000 years. The degree of melting was low, as indicated by the presence of muscovite all through the sequence. This evidence indicates that the LH behaved as a coherent block, and thermomechanical models quantitatively reproduce many of these features as well as explain the formation of inverted metamorphic sequence in such a coherent block. The greater Himalayan sequence ( GH), also largely metapelitic, has different protoliths (with components as young as 800 Ma) and a different metamorphic history (extensive migmatization at higher grades ~8-12 kbar, 750-850 °C at an older age of largely >20 Ma along a different clockwise P- T path characterized by sharp, isothermal decompression followed by near isobaric cooling). Geochronological data (monazite, zircon, garnet) as well as cooling rate calculations (geospeedometry) reveal that the GH is made up of at least two blocks with distinct, complex and multistage P- T- t histories. Different stages of the high- T cooling were rapid (100's °C Ma−1 to 10's °C Ma−1 at different stages) and at least some of it was unrelated to exhumation; synthesis of these results with low- T thermochronometry allows the detailed multistage cooling and exhumation history of this block to be reconstructed. The reconstructed cooling and exhumation histories show that a number of interlinked processes operating on a hierarchy of timescales leads to the overall evolution. The P- T history with rapid cooling can be reproduced by thermomechanical models that consider conductive as well as advective heat transport and there is no need to invoke additional processes (such as the role of fluids). Metabasic inclusions within both the LH and the GH appear to record a different (? older in part) history. The role of these in the overall evolution, as well as the difference in metamorphic ages of the LH and GH remain open questions that need to be addressed in future research. [ABSTRACT FROM AUTHOR]

Presented here is a suite of new experiments aimed at quantifying the effects of pressure, temperature, bulk composition, and HO content on the stability and composition of amphibole in the Earth's mantle. Experiments have been performed from 2 to 4 GPa and 950 to 1100 °C on fertile and depleted mantle compositions. HO contents of most experiments are 0.65 wt%. In the fertile mantle composition, pargasitic amphibole is stable up to ~3.8 GPa at 1000 °C, approximately 0.5 GPa higher than any previous study. The upper stability limit of amphibole in depleted mantle is 0.7 GPa and 40 °C lower than in fertile mantle. The addition of 3 wt% HO to fertile mantle destabilizes amphibole by 0.5 GPa and 40 °C relative to the 0.65 wt% HO experiments. Compared to existing experiments on amphibole stability, these experiments indicate that pargasitic amphibole may be stable in mantle lithosphere to almost 4 GPa (0.5 GPa higher (15 km deeper) than previously thought). The extremely strong destabilizing effect of HO suggests that deeper portions of the strongly fluid-fluxed mantle wedge may be amphibole-free even at low temperatures near the slab-wedge interface. The molar alkali content of amphibole is shown to be a linear function ( R = 0.98) of pressure and temperature and is relatively insensitive to bulk compositional differences between fertile and depleted mantle. This relationship is used to produce an empirical thermobarometer for pargasite-bearing spinel and garnet lherzolites. Comparison to existing experimental data shows that this thermobarometer has predictive ability over the pressure range of 1-4 GPa. Comparisons with pressure-temperature estimates of garnet + amphibole peridotites further corroborate the applicability of this thermobarometer for natural samples. Pressure estimates are presented for four examples of metasomatized spinel peridotites otherwise lacking pressure information, and future avenues for refinement of the thermobarometer are discussed. [ABSTRACT FROM AUTHOR]

New mineral-melt thermobarometry and mineral chemistry data are presented for basaltic scoriae erupted from the Mbwelesu crater of Ambrym volcano, Vanuatu, during persistent lava lake activity in 2005 and 2007. These data reveal crystallisation conditions and enable the first detailed attempt at reconstruction of the central magma plumbing system of Ambrym volcano. Pressures and temperatures of magma crystallisation at Ambrym are poorly constrained. This study focuses on characterising the magma conditions underlying the quasi-permanent lava lakes at the basaltic central vents, and examines petrological evidence for magma circulation. Mineral-melt equilibria for clinopyroxene, olivine and plagioclase allow estimation of pressures and temperatures of crystallisation, and reveal two major regions of crystallisation, at 24–29 km and 11–18 km depth, in agreement with indications from earthquake data of crustal storage levels at c. 25–29 km and 12–21 km depth. Temperature estimates are ~ 1150–1170 °C for the deeper region, and ~ 1110–1140 °C in the mid-crustal region, with lower temperatures of ~ 1090–1100 °C for late-stage crystallisation. More primitive plagioclase antecrysts are thought to sample a slightly more mafic melt at sub-Moho depths. Resorption textures combined with effectively constant mafic mineral compositions suggest phenocryst convection in a storage region of consistent magma composition. In addition, basalt erupted at Ambrym has predominantly maintained a constant composition throughout the volcanic succession. This, coupled with recurrent periods of elevated central vent activity on the scale of months, suggest frequent magmatic recharge via steady-state melt generation at Ambrym. [ABSTRACT FROM AUTHOR]

Ambrym, a basaltic volcano in the Vanuatu Arc, has displayed variable eruptive behaviour throughout the past century, with major eruptions occurring both on the volcano flanks and at multiple vents within its caldera. These have been interspersed with periods of relative quiescence marked by extensive passive degassing at active, intra-caldera lava lakes, which experience occasional Strombolian explosions. Volcanic rocks from all vents and eruptive styles display similar isotope and incompatible trace element compositions, suggesting that all are derived from the same primary melt by fractional crystallization. Major eruptions are commonly responsible for effusion of the least evolved lavas examined (SiO2~50 wt %; MgO~5 wt %). Although all are geochemically similar, petrological differences discriminate between lavas erupted during flank and intra-caldera eruptions. Phyric basalts with homogeneous mineral compositions are common to flank eruptions, whereas crystal-rich basalts with variable mineral compositions, many not in equilibrium with their host liquid, are a feature of intra-caldera lavas. Lava lake samples are slightly more evolved than those from effusive eruptions (SiO2~51-52 wt %; MgO~4 wt %), as a result of additional crystallization during periods of relative quiescence. The diverse petrology of the intra-caldera lavas can be explained by mixing of replenishment magmas similar to those erupted from the volcano flanks with residual magma from lava lake activity. Flank eruptions exploit dykes that bypass the shallow reservoir involved with lava lake activity, limiting their interaction with this component. [ABSTRACT FROM AUTHOR]

We reconstructed the spatial distribution of eclogites in the cratonic mantle based on thermobarometry for ~ 240 xenoliths in 4 kimberlite pipes from different parts of the Slave craton (Canada). The accuracy of depth estimates is ensured by the use of a recently calibrated thermometer, projection of temperatures onto well-constrained local peridotitic geotherms, petrological screening for unrealistic temperature estimates, and internal consistency of all data. The depth estimates are based on new data on mineral chemistry and petrography of 148 eclogite xenoliths from the Jericho and Muskox kimberlites of the northern Slave craton and previously reported analyses of 95 eclogites from Diavik and Ekati kimberlites (Central Slave). The majority of Northern Slave eclogites of the crustal, subduction origin occurs at 110–170 km, shallower than in the majority of the Central Slave crustal eclogites (120–210 km). The identical geochronological history of these eclogite populations and the absence of steep suture boundaries between the central and northern Slave craton suggest the lateral continuity of the mantle layer relatively rich in eclogites. We explain the distribution of eclogites by partial preservation of an imbricated and plastically dispersed oceanic slab formed by easterly dipping Proterozoic subduction. The depths of eclogite localization do not correlate with geophysically mapped discontinuities. The base of the depleted lithosphere of the Slave craton constrained by thermobarometry of peridotite xenoliths coincides with the base of the thickened lithospheric slab, which supports contribution of the recycled oceanic lithosphere to formation of the cratonic root. Its architecture may have been protected by circum-cratonic subduction and shielding of the shallow Archean lithosphere from the destructive asthenospheric metasomatism. [ABSTRACT FROM AUTHOR]

Tests show that terrestrial mineral+liquid geothermobarometers are not well equipped for use on martian rocks, which tend to have much higher FeO and lower Al2O3. Here, we present new calibrations of thermometers and barometers using experimental data on martian samples from the literature. These new models recover P-T conditions with a greater accuracy compared to models calibrated using terrestrial compositions. We applied these new calibrations to primitive martian mantle-derived melts Yamato 980459 (Y98) and Northwest Africa (NWA) 6234 and several surface basalts (Gusev). Our new models yield similar P-T conditions for NWA and Y98 compositions of 1.4-1.7 GPa and 1500-1550 °C, which are close to estimates by most prior studies. Our models yield somewhat lower P estimates compared to Lee et al. (2009), apparently because our Si-activity model (from Beattie 1993) includes an Al2O3-correction (where lower Al2O3, as in martian samples, leads to lower P estimates). For Gusev basalt compositions, our new models yield P-T estimates of 1.0-1.3 GPa and 1340-1390 °C; furthermore, we also obtain P = 1.03 GPa and T = 1340 °C, for a Gusev composition from Monders et al. (2007), which comes very close to the Monders et al. (2007) estimate for multiple saturation, of 1.0 GPa and 1325 °C, derived from phase saturation relationships. Given the different ages of these meteorites, with Gusev at 3.65 Ga (Greeley et al. 2005) and Y98 at 4.3 Ga (Bouvier et al. 2005, 2008, 2009; Werner et al. 2014), their thermal contrasts may represent secular cooling of Mars. We estimate a mantle potential temperature difference of ~200 °C, with mantle potential temperatures of 1450 ±50 °C for Gusev and 1650 ±50 °C for Y98; this implies a cooling rate of 300 °C/Ga. This would appear to be a much more rapid rate of cooling compared to Earth, as may be expected by Mars' higher surface/volume ratio. [ABSTRACT FROM AUTHOR]

The Delbar metamorphic complex is located 130 km southeast of Shahrood (Biarjmand area) in the northern margin of the Central Iran. This complex consists of four groups include metapelitic, metapsammitic, metacarbonatic and metabasitic compositions. Field evidences indicate the protolith of the complex were shale and sandstone (psammite and graywacke) alternation with carbonate layers in the upper parts. The complex crosscut by numerous diabasic dikes with late Neoprotrozoic- early Cambrian age which evolved to the foliated metabasites such as amphibole schist, amphibolite and garnet amphibolite. The sedimentary sequence in which diabasic dikes intruded subjected by intermediate P-T regional metamorphism (Barrovian type). The results of thermometry based on the varied calibrations of garnet-biotite pair and barometry through GBPQ method demonstrate 468-498 ˚C and 6.4-7.2 Kbar for micaschists and 645-706 ˚C and 8.4-13.2 Kbar for gneisses indicating greenschist for micashists and upper amphibolite facies for gneisses respectively. The increase of temperature and pressure confirms the prograde regional metamorphism event up to acheive the melting point and the partial melting initiation. The diverse migmatite structures generated in the metapelitic and metapsamitic rocks from felsic meltsexposed as the anatectic granites and leucogranites. The results of U-Pb age dating indicate 541±4.7 Ma to 547±9.9 Ma (late Neoprotrozoic- early Cambrian) age range. The regional metamorphism event in the Delbar complex is related to the Pan-African orogeny according to the obtained age data and with comparsion to the other similar metamorphic complexes and granitoids in the Central Iran. [ABSTRACT FROM AUTHOR]

The Ciomadul is the youngest volcano of the Carpathian–Pannonian region, which erupted last time at 32 ka. It produced high-K dacitic lava domes and pumiceous pyroclastic rocks. The dacite is crystal-rich and contains plagioclase, amphibole in addition to biotite, titanite, apatite, zircon and occasionally quartz, K-feldspar as well as olivine, clinopyroxene and orthopyroxene. There are two groups of amphiboles, characterized by low-Al and high-Al, respectively. They occur in the same samples and also as different zones of the same crystals. Thermobarometric calculations suggest that the low-Al amphiboles were formed from a low temperature (< 800 °C) silicic magma, whereas the high-Al amphiboles crystallized at about 950 °C from a more mafic melt. A near-solidus silicic crystal mush body was stored at 7–14 km depth, where an eruptible magma batch was produced by major reheating (about 200 °C temperature increase) due to the intrusion of hot mafic magma into the silicic magma reservoir. A magnetotelluric survey was performed to reveal whether any melt-bearing magma body could presently reside beneath the volcano. Both the 2D and 3D inversion modeling calculations indicate low electric resistivity values in the depth interval of 5–25 km, just beneath the volcanic centers. This can be interpreted as implying a partially melted zone, i.e. a crystal mush body containing about 5–15% melt fraction. In addition, the 2D modeling calculation indicates also a deeper low resistivity anomaly at 30–40 km depth. The consistent petrologic and magnetotelluric constrains on the magma storage beneath Ciomadul are corroborated by the recent seismic tomography result, which pointed out a low-velocity anomaly at 8–20 km depth zone. Thus, results of independent models suggest the presence of a melt-bearing crystal mush body beneath the seemingly inactive volcano. Since there are implications for long repose periods during the lifetime of the volcano as well as for effective and rapid remobilization of the low-temperature silicic crystal mush body prior to volcanic eruptions, the present existence of a low melt fraction silicic crystal mush beneath Ciomadul could mean that there is still a potential for a rejuvenation in the future. We suggest for long-dormant or seemingly inactive volcanoes, such as Ciomadul, having melt-bearing magmatic body at depths to term as ‘volcano with potentially active magma storage’ or PAMS volcano. [ABSTRACT FROM AUTHOR]

Highlights: [•] P–T and petrochemical profiles (100–170km dept range) for Kasai Craton. [•] The mineralogy of xenoliths suggesting two stages in thermal regime at least. [•] Aspects of Nb and Ta fractionation in the upper mantle. [•] The first age data for mantle eclogites from the Catoca pipe. [•] Rutiles from hi-MgO eclogites containing up to 11wt.% Nb2O5 (ilmenorutiles) [ABSTRACT FROM AUTHOR]

The northern Cascade arc is an end-member ‘hot’ subduction zone where slab dehydration may be essentially complete prior to reaching sub-arc depths, presenting a potential problem for a flux melting origin for arc basalts. Nevertheless, mafic lavas from the Mt. Baker volcanic field, the most magmatically productive volcano in the northern Cascade arc, record subduction input and compositions typical of calc-alkaline magmas. Relative to normal mid-ocean ridge basalt, the most primitive lavas at Mt. Baker show elevated abundances of large ion lithophile elements (LILE), Pb and light rare earth elements (LREE). High field strength elements (HFSE) and heavy REE (HREE) are depleted relative to LILE. Reconstructed primary magmas define three groups: Group I calc-alkaline basalts (Sulphur Creek, Lake Shannon, Hogback) have lower SiO2, (La/Yb)N and LILE/HFSE, and are olivine- and plagioclase-phyric; Group II high-Mg basaltic andesites (Tarn Plateau, Cathedral Crag) also contain clinopyroxene phenocrysts and have higher H2O, SiO2, (La/Yb)N and LILE/HFSE; Group III low-K olivine tholeiite (Park Butte) has the lowest (La/Yb)N but highest LILE/HFSE. The redox states of all groups lie between QFM (quartz–fayalite–magnetite) and QFM +1·4. Pb, Sr and Nd isotope compositions are similar among all the analysed samples and are consistent with a depleted mantle source modified by input from the subducting slab. Trace element–isotope modeling indicates a subduction component composed predominantly of metabasalt-derived fluid with lesser amounts of sediment melt and metabasalt melt. Group I basalts record the smallest melt fractions (∼5–7%), lowest water contents (1·5–2·1 wt %), and highest temperatures and pressures of mantle segregation (up to 1354°C, 1·5 GPa) from lherzolitic (± spinel) residues. Group II basaltic andesites show the greatest extents of mantle metasomatism, the highest water contents (2·7–3·7 wt %) and partial melt fractions (10–12%), and segregated from harzburgite at ∼1270°C, 1 GPa, consistent with pooling of melts at the Moho. Group III records P–T conditions similar to Group I (∼1·4 GPa, 1326°C) but melt fractions (12%) and mantle residues (harzburgite) are more similar to Group II, and H2O contents (∼2·1 wt %) are intermediate. Melting beneath Mt. Baker was initiated by dehydration melting of amphibole peridotite at ∼95 km and 1020°C, within the stability field of garnet lherzolite. Initial melt fractions were small (∼1–2%) and near water-saturation. Phase equilibria and trace element modeling show no evidence for garnet-bearing mantle residues, indicating that progressive melting during ascent of diapirs through the hot core of the convecting mantle wedge reduced H2O contents and erased any residual garnet signature. Because fluid release from the slab is restricted to the forearc, mantle hydrated at shallow depths in the serpentine and/or chlorite stability fields must be down-dragged to the region of amphibole stability to initiate dehydration melting. [ABSTRACT FROM PUBLISHER]

Abstract: Following a fumarolic episode that started six months earlier, the most recent eruptive activity of the Ubinas volcano (south Peru) began on 27 March 2006, intensified between April and October 2006 and slowly declined until December 2009. The chronology of the explosive episode and the extent and composition of the erupted material are documented with an emphasis on ballistic ejecta. A petrological study of the juvenile products allows us to infer the magmatic processes related to the 2006–2009 eruptions of the andesitic Ubinas volcano. The juvenile magma erupted during the 2006 activity shows a homogeneous bulk-rock andesitic composition (56.7–57.6wt.% SiO2), which belongs to a medium- to high-K calc-alkaline series. The mineral assemblage of the ballistic blocks and tephra consists of plagioclase>two-pyroxenes>Fe–Ti oxide and rare olivine and amphibole set in a groundmass of the same minerals with a dacitic composition (66–67wt.% SiO2). Thermo-barometric data, based on two-pyroxene and amphibole stability, records a magma temperature of 998±14°C and a pressure of 476±36MPa. Widespread mineralogical and textural features point to a disequilibrium process in the erupted andesite magma. These features include inversely zoned “sieve textures” in plagioclase, inversely zoned clinopyroxene, and olivine crystals with reaction and thin overgrowth rims. They indicate that the pre-eruptive magmatic processes were dominated by recharge of a hotter mafic magma into a shallow reservoir, where magma mingling occurred and triggered the eruption. Prior to 2006, a probable recharge of a mafic magma produced strong convection and partial homogenization in the reservoir, as well as a pressure increase and higher magma ascent rate after four years of fumarolic activity. Mafic magmas do not prevail in the Ubinas pre-historical lavas and tephras. However, mafic andesites have been erupted during historical times (e.g. AD 1667 and 2006–2009 vulcanian eruptions). Hence, the most recent episode indicates that a resupply of mafic magmas has probably occurred at depth under Ubinas. [Copyright &y& Elsevier]