Articles de revues : « Trachybasalts »

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Perinelli, Cristina, Silvio Mollo, Mario Gaeta, Serena De Cristofaro, Danilo Palladino et Piergiorgio Scarlato. « Impulsive Supply of Volatile-Rich Magmas in the Shallow Plumbing System of Mt. Etna Volcano ». Minerals 8, n^o 11 (25 octobre 2018) : 482. http://dx.doi.org/10.3390/min8110482.

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Magma dynamics at Mt. Etna volcano are frequently recognized as the result of complex crystallization regimes that, at shallow crustal levels, unexpectedly change from H2O-undersaturated to H2O-saturated conditions, due to the impulsive and irregular arrival of volatile-rich magmas from mantle depths. On this basis, we have performed hydrous crystallization experiments for a quantitative understanding of the role of H2O in the differentiation of deep-seated trachybasaltic magmas at the key pressure of the Moho transition zone. For H2O = 2.1–3.2 wt %, the original trachybasaltic composition shifts towards phonotephritic magmas never erupted during the entire volcanic activity of Mt. Etna. Conversely, for H2O = 3.8–8.2 wt %, the obtained trachybasalts and basaltic trachyandesites reproduce most of the pre-historic and historic eruptions. The comparison with previous low pressure experimental data and natural compositions from Mt. Etna provides explanation for (1) the abundant release of H2O throughout the plumbing system of the volcano during impulsive ascent of deep-seated magmas; (2) the upward acceleration of magmas feeding gas-dominated, sustained explosive eruptions; (3) the physicochemical changes of gas-fluxed magmas ponding at shallow crustal levels; and (4) the huge gas emissions measured at the summit craters and flank vents which result in a persistent volcanic gas plume.

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Krasnobaev, Artur A., Victor N. Puchkov, Nina D. Sergeeva et Sofia V. Busharina. « Polychronous zircons of volcanics of the Navysh complex of the Lower Riphean Ai Formation (Southern Urals) ». Georesursy 22, n^o 4 (décembre 2020) : 101–12. http://dx.doi.org/10.18599/grs.2020.4.101-112.

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The volcanics of the Navysh complex of the Lower Riphean Ai Formation in the Southern Urals are well studied petrochemically and dated by several methods. In 2013 zircons from a trachybasalt porphyrite (sample 2152) gave a concordant SHRIMP date 1752±11 Ma, which was used as a fundamental for the lower boundary of the Riphean with no special arguments against it. The later attempts to repeat this date for the Navysh volcanics were not successful: the collected zircons were either more ancient (> 2500 Ma), or more young (< 500 Ma). From the beginning, the zircons with such ages were regarded as xenogenic or secondary metasomatic, or belonging to paleozoic dykes intruding the Riphean volcanics. However, the clearly expressed mineralogical properties of the Paleozoic zircons and their frequent presence in volcanics, not dykes, led to a conclusion that the zircons and Navysh volcanics, containing them, and exposed within the area of development of the Ai Formation, are polychronous. To support this conclusion, the authors studied in more detail the zircons of the Navysh trachybasalts, developed in the Ai Formation. The main conclusion, obtained from this new data, was that the volcanics attributed to the Navysh complex, form a polychronous system, including both the Lower Riphean (1750 Ma) and Paleozoic (450 Ma) rocks. The zircons of these age groups differ in their mineralogical and geochemical properties supporting the idea that they belong to different primary sources which may be due to repeating plume processes, which partly reanimated – heated and melted-rocks of the previous cycle and/or created new sources of melts.

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Dabiri, Rahim, Mohamad Emami, Habib Mollaei, Bin Chen, Mansor Abedini, Nematallah Omran et Mitra Ghaffari. « Quaternary post-collision alkaline volcanism NW of Ahar (NW Iran) : geochemical constraints of fractional crystallization process ». Geologica Carpathica 62, n^o 6 (1 décembre 2011) : 547–62. http://dx.doi.org/10.2478/v10096-011-0039-2.

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Quaternary post-collision alkaline volcanism NW of Ahar (NW Iran): geochemical constraints of fractional crystallization process Major and trace elements and Sr-Nd isotopic data are presented for the Quaternary alkaline volcanism NW of Ahar (NW Iran). The exposed rocks mainly consist of alkali basalts, trachybasalts, basaltic trachyandesites and trachyandesites. Alkali basalts and trachybasalts display microlithic porphyritic texture with phenocrysts of olivine, clinopyroxene, and plagioclase in microlithic groundmass. In the more evolved rocks (basaltic trachyandesites and trachyandesites), amphibole and biotite have appeared. Major and trace element abundances vary along continuous trends of decreasing MgO, TiO2, Fe2O3*, CaO, Co, Cr, V and Zn, and increasing K2O, Al2O3, Ba and Th with increasing SiO2. The Sr and Nd isotopic ratios vary from 0.704463 to 0.704921 and from 0.512649 to 0.512774, respectively. Alkali basalts with high 143Nd/144Nd ratio, low 87Sr/86Sr ratio and high MgO, Ni and Cr contents indicate that they were generated from relatively primitive magmas. Ba, Cr and La/Sm ratios versus Rb suggest that fractional crystallization of alkali basalts could have played a significant role in the formation of evolved rocks. Assimilation and fractional crystallization modelling, as well as Rb/Zr, Th/Yb and Ta/Yb ratios clearly indicate that crustal contamination accompanied by the fractional crystallization played an important role in petrogenesis of the trachyandesites. The small compositional differences between magma types, isotopic composition, mineralogy and nonlinear trends on Harker diagrams also indicate that magma mixing was not an essential process in the evolution of the Ahar magmas. Petrogenetic modelling has been used to constrain sources. Trace element ratio plots and REE modelling indicate that the alkali basalts were generated from a spinel-peridotite source via small degrees (~2.5%) of fractional melting.

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Karimov, Vagif M. « Some geological and petrological characteristics of the Eocene trachybasalt-trachyandesite- basalt-phonolite formation of the Talysh zone (Azerbaijan) ». Journal of Geology, Geography and Geoecology 31, n^o 3 (23 septembre 2022) : 484–92. http://dx.doi.org/10.15421/112244.

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This article discusses the stages of crystallization of the Eocene trachybasalt-tra- chyandesitebasalt-phonolith formation of the Talysh zone. Determination of the composi- tion of the primary magma, evolution and melting fraction of the initial melt of the Eocene volcanism of the Talysh zone within Azerbaijan. Eocene volcanism of the trachybasalt-tra-chyandesitebasalt-phonolith formation of the Talysh zone. Petrographic, petrochemical, geochemical studies of rocks, typomorphic features of mineral paragenesis, chemical composition of rocks were carried out by X-ray spectral and X-ray fluorescence analysis. The analyzes of the conducted studies show that the Talysh zone was formed in the Eocene time. Stages of evolution of the original magma and typomorphic features of mineral parageneses have been established. The distributions of microelements in mineral parageneses, which are direct participants in the crystallization processes that took place in intermediate chambers at different depths, have been studied. At present, the question arises of the need to clarify the typomorphic features of igneous complexes, as factors that determine the geodynamic regimes of their formation, and to determine the potential ore content. The petrographic and petrochemical characteristics of the volcanic rocks are given. It was found that if the process of differentiation in the Early-Middle Eocene was more distinct with the initial formation of more magnesian rock varieties (picrite-trachybasalts), and subsequently more ferruginous ones (trachyandesites and trachyandesitebasalts), then such accumulation of iron is not observed in porphyritic trachyandesites. This petrochemical feature is obviously associated with the duration of the break in volcanism, caused by the formation of a thick sedimentary-tuffaceous stratum, accompanied by the initiation and manifestation of an intermediate chamber of medium composition. Volcanism in the Late Eocene was undifferentiated and was not accompanied by the formation of medium differences. The appearance in the late Eocene of leucite phonolites, which represent an alkaline branch, and the absence of transitional varieties indicate the autonomous development of vit- robasalts and leucite phonolites. It is concluded that from the early phases of the manifestation of Eocene volcanism to the later phases, the change in the material composition along the lateral is expressed in the manifestation of more alkaline facies with a significant predominance of K over Na and with a greater correspondence to the differentials of the shoshonite series.

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Holm, Paul Martin, L. E. Pedersen, et B. Højsteen. « Geochemistry and petrology of mafic Proterozoic and Permian dykes on Bornholm, Denmark : Four Episodes of magmatism on the margin of the Baltic Shield ». Bulletin of the Geological Society of Denmark 58 (17 mai 2010) : 35–65. http://dx.doi.org/10.37570/bgsd-2010-58-04.

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More than 250 dykes cut the mid Proterozoic basement gneisses and granites of Bornholm. Most trend between NNW and NNE, whereas a few trend NE and NW. Field, geochemical and petrological evidence suggest that the dyke intrusions occurred as four distinct events at around 1326 Ma (Kelseaa dyke), 1220 Ma (narrow dykes), 950 Ma (Kaas and Listed dykes), and 300 Ma (NW-trending dykes), respectively. The largest dyke at Kelseaa (60 m wide) and some related dykes are primitive olivine tholeiites, one of which has N-type MORB geochemical features; all are crustally contaminated. The Kelseaa type magmas were derived at shallow depth from a fluid-enriched, relatively depleted, mantle source,but some have a component derived from mantle with residual garnet. They are suggested to have formed in a back-arc environment. The more than 200 narrow dykes are olivine tholeiites (some picritic), alkali basalts, trachybasalts, basanites and a few phonotephrites. The magmas evolved by olivine and olivine + clinopyroxene fractionation. They have trace element characteristics which can be described mainly by mixing of two components: one is a typical OIB-magma (La/Nb < 1, Zr/Nb = 4, Sr/Nd = 16) and rather shallowly derived from spinel peridotite; the other is enriched in Sr and has La/Nb = 1.0 - 1.5, Zr/Nb = 9, Sr/Nd = 30 and was derived at greater depth, probably from a pyroxenitic source. Both sources were probably recycled material in a mantle plume. A few of these dykes are much more enriched in incompatible elements and were derived from garnet peridotite by a small degree of partial melting. The Kaas and Listed dykes (20-40 m) and related dykes are evolved trachybasalts to basaltic trachyandesites. They are most likely related to the Blekinge Dalarne Dolerite Group. The few NW-trending dykes are quartz tholeiites, which were generated by large degrees of rather shallow melting of an enriched mantle source more enriched than the source of the older Bornholm dykes. The source of the NW-trending dykes was probably a very hot mantle plume.

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Lipman, Peter W., et Matthew J. Zimmerer. « Magmato-tectonic links : Ignimbrite calderas, regional dike swarms, and the transition from arc to rift in the Southern Rocky Mountains ». Geosphere 15, n^o 6 (30 septembre 2019) : 1893–926. http://dx.doi.org/10.1130/ges02068.1.

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Abstract Radial and linear dike swarms in the eroded roots of volcanoes and along rift zones are sensitive structural indicators of conduit and eruption geometry that can record regional paleostress orientations. Compositionally diverse dikes and larger intrusions that radiate westward from the polycyclic Platoro caldera complex in the Southern Rocky Mountain volcanic field (southwestern United States) merge in structural trend, composition, and age with the enormous but little-studied Dulce swarm of trachybasaltic dikes that continue southwest and south for ∼125 km along the eastern margin of the Colorado Plateau from southern Colorado into northern New Mexico. Some Dulce dikes, though only 1–2 m thick, are traceable for 20 km. More than 200 dikes of the Platoro-Dulce swarm are depicted on regional maps, but only a few compositions and ages have been published previously, and relations to Platoro caldera have not been evaluated. Despite complications from deuteric alteration, bulk compositions of Platoro-Dulce dikes (105 new X-ray fluorescence and inductively coupled plasma mass spectrometry analyses) become more mafic and alkalic with distance from the caldera. Fifty-eight (58) new 40Ar/39Ar ages provide insight into the timing of dike emplacement in relation to evolution of Platoro caldera (source of six regional ignimbrites between 30.3 and 28.8 Ma). The majority of Dulce dikes were emplaced during a brief period (26.5–25.0 Ma) of postcaldera magmatism. Some northeast-trending dikes yield ages as old as 27.5 Ma, and the northernmost north-trending dikes have younger ages (20.1–18.6 Ma). In contrast to high-K lamprophyres farther west on the Colorado Plateau, the Dulce dikes are trachybasalts that contain only anhydrous phenocrysts (clinopyroxene, olivine). Dikes radial to Platoro caldera range from pyroxene- and hornblende-bearing andesite to sanidine dacite, mostly more silicic than trachybasalts of the Dulce swarm. Some distal andesite dikes have ages (31.2–30.4 Ma) similar to those of late precaldera lavas; ages of other proximal dikes (29.2–27.5 Ma) are akin to those of caldera-filling lavas and the oldest Dulce dikes. The largest radial dikes are dacites that have yet younger sanidine 40Ar/39Ar ages (26.5–26.4 Ma), similar to those of the main Dulce swarm. The older andesitic dikes and precaldera lavas record the inception of a long-lived upper-crustal magmatic locus at Platoro. This system peaked in magmatic output during ignimbrite eruptions but remained intermittently active for at least an additional 9 m.y. Platoro magmatism began to decline at ca. 26 Ma, concurrent with initial basaltic volcanism and regional extension along the Rio Grande rift, but no basalt is known to have erupted proximal to Platoro caldera prior to ca. 20 Ma, just as silicic activity terminated at this magmatic locus. The large numbers and lengths of the radial andesitic-dacitic dikes, in comparison to the absence of similar features at other calderas of the San Juan volcanic locus, may reflect location of the Platoro system peripheral to the main upper-crustal San Juan batholith recorded by gravity data, as well as its proximity to the axis of early rifting. Spatial, temporal, and genetic links between Platoro radial dikes and the linear Dulce swarm suggest that they represent an interconnected regional-scale magmatic suite related to prolonged assembly and solidification of an arc-related subcaldera batholith concurrently with a transition to regional extension. Emplacement of such widespread dikes during the late evolution of a subcaldera batholith could generate earthquakes and trigger dispersed small eruptions. Such events would constitute little-appreciated magmato-tectonic hazards near dormant calderas such as Valles, Long Valley, or Yellowstone (western USA).

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Togo, Abondou, Nkouandou Oumarou Faarouk, Zangmo Tefogoum Ghislain, Fagny Mefire Aminatou, Daouda Dawai, Dinamou Appoliaire, Guihdama Dagwai Justin et Adama Haman. « Petrography and geochemical framework of guÃ©bakÃ© dolerites dyke swarms (north Cameroon, central Africa) ». International Journal of Advanced Geosciences 10, n^o 1 (5 avril 2022) : 19–27. http://dx.doi.org/10.14419/ijag.v10i1.31939.

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Dolerites dykes of 4.5 to 25 m wide extend from 200m to 1km, crosscut the GuÃ©bakÃ© granitoids basement in northern Cameroon along EW to N100E directions. Petrographic studies reveal the microlitic porphyritic texture to classical doleritic texture of ophitic to sub-ophitic types. GuÃ©bakÃ© dolerites are mainly composed in various proportions of skeletal plagioclase and feldspar, clinopyxene, amphibole and oxides crystals. ICP-MS and ICP-AES geochemical analyses have distiguished a lava series composed of trachybasalts, basaltic trachyandesites, trachyandesites, trachytes and rhyolites of continentale tholeiites affinity. Lavas have been differenciated trough fractional crystallization process coupled with crustal contamination and metasomatism. GuÃ©bakÃ© dolerites are products of relatively high partial melting rate of E-MORB mantle component. They stand as fingerprints of the post pan African crustal consolidation and precursor of the development of central African rift system at Cretaceous times.Â Â

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Terekhov, E. N., A. B. Makeyev, S. G. Skublov, O. I. Okina et Yu A. Maximova. « Quartz Porphyries of the Outer Islands of the Gulf of Finland ‒ Volcanic Comagmates of the Rapakivi Granites ». Вулканология и сейсмология 17, n^o 6 (1 novembre 2023) : 101–21. http://dx.doi.org/10.31857/s020303062370030x.

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The article presents new petrogeochemical data of rocks from the area of the Outer Islands of the Gulf of Finland. Previously, quartz porphyries of Gogland Island were considered as a standard of volcanic comagmates of Rapakivi granite of the Vyborg massif. There are two effusive tolshas on Sommers Island. The “Southern” is composed of quartz porphyries, with an isotopic age of 1.66 Ga old, so they can be considered as the earliest manifestations of Riphean magmatic activity in this area. In addition to quartz porphyries, trachybasalts, andesibasalts, and dacites are present in the “Northern” strata, and its isotopic age is 1.59‒1.57 Ga old, which does not correspond to the values of the nearby Vyborg massif 1.65‒1.63 Ga old. Therefore, despite the pro-ximity of the compositions of quartz porphyry and rapakivi granites, volcanites are not products of differentiation of the magma initial for granites, but were formed independently of them from the same type of source, but in a slightly different structural environment, allowing their free flow to the Earth’s surface.

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Demonterova, E. I., A. V. Ivanov, S. V. Palessky, V. F. Posokhov, N. S. Karmanov et L. A. Pel’gunova. « Feldspar Megacrysts as a Source of Information on Crustal Contamination of Basaltic Melt ». Геохимия 68, n^o 7 (1 juillet 2023) : 651–68. http://dx.doi.org/10.31857/s0016752523070026.

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The paper discusses data on the elemental composition and 87Sr/86Sr, and δ18O isotopic ratios of feldspar megacrysts collected from lava flows, tuffs, and cinders of three volcanic fields in the Baikal rift system: Iya–Uda, Vitim, and Khamar-Daban, which are located within the early Precambrian, Riphean, and Paleozoic crustal blocks, respectively. Megacrysts are hosted in trachybasalts in the Iya–Uda and Khamar-Daban fields and in basanites in the Vitim field. Megacrysts belong to the following three compositional groups of minerals: (i) plagioclase in lavas of the Iya–Uda field, (ii) anorthoclase in lava flows, tuffs, and cinders of the Khamar-Daban and Vitim fields, and (iii) sanidine in the Vitim field. Elemental and isotope data suggest that megacrysts crystallized in volcanic chambers at different depth levels: anorthoclase crystallized from the most primitive magma with mantle-derived isotopic signatures at subcrustal depth levels, plagioclases were produced in deep crustal chambers during the interaction between mantle-derived magma and crustal rocks, and sanidine was captured from the upper crustal rocks.

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Yu. Fridovsky, Valery, Kyunney Yu Yakovleva, Antonina E. Vernikovskaya, Valery A. Vernikovsky, Nikolay Yu Matushkin, Pavel I. Kadilnikov et Nickolay V. Rodionov. « Geodynamic Emplacement Setting of Late Jurassic Dikes of the Yana–Kolyma Gold Belt, NE Folded Framing of the Siberian Craton : Geochemical, Petrologic, and U–Pb Zircon Data ». Minerals 10, n^o 11 (11 novembre 2020) : 1000. http://dx.doi.org/10.3390/min10111000.

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We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochronological investigations of mafic, intermediate, and felsic igneous rocks from dikes in the Yana–Kolyma gold belt of the Verkhoyansk–Kolyma folded area (northeastern Asia). The dikes of the Vyun deposit and the Shumniy occurrence intruding Mesozoic terrigenous rocks of the Kular–Nera and Polousniy–Debin terranes were examined in detail. The dikes had diverse mineralogical and petrographic compositions including trachybasalts, andesites, trachyandesites, dacites, and granodiorites. The rocks showed significant similarities in distributions of REE, and their concentrations of most HFSEs were close to the intermediate ones between ocean islands basalts and enriched middle ocean ridge basalts. We propose that the subduction that was ongoing during the collision of the Kolyma–Omolon superterrane with Siberia led to melting in the asthenospheric wedge and in the lithosphere, which formed a mixed source for the dike systems from both an enriched and a depleted mantle source. The U–Pb SHRIMP-II dates obtained for the dikes corresponded to the Late Jurassic interval of 151–145 Ma. We present a geodynamic model for the northeastern margin of the Siberian Craton for the Tithonian age of the Late Jurassic.

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Zhu, Yongfeng, et Yoshihide Ogasawara. « Clinopyroxene phenocrysts (with green salite cores) in trachybasalts : implications for two magma chambers under the Kokchetav UHP massif, North Kazakhstan ». Journal of Asian Earth Sciences 22, n^o 5 (janvier 2004) : 517–27. http://dx.doi.org/10.1016/s1367-9120(03)00091-9.

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Naumov, V. B., M. V. Portnyagin, M. L. Tolstykh et V. V. Yarmolyuk. « Chemical composition and crystallization conditions of trachybasalts from the Dzhida field, Southern Baikal volcanic area : Evidence from melt and fluid inclusions ». Geochemistry International 44, n^o 3 (mars 2006) : 286–95. http://dx.doi.org/10.1134/s0016702906030062.

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Osika, Aleksandra, Małgorzata Wistuba et Ireneusz Malik. « Relief evolution of landslide slopes in the Kamienne Mts (Central Sudetes, Poland) – analysis of a high-resolution DEM from airborne LiDAR ». Contemporary Trends in Geoscience 7, n^o 1 (1 juin 2018) : 1–20. http://dx.doi.org/10.2478/ctg-2018-0001.

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Abstract The aim of the study is to reconstruct the development of landslide relief in the Kamienne Mountains (Central Sudetes, SW Poland) based on a DEM from LiDAR data. Analyses of relief and geological maps in ArcGIS 10.5 and of slope cross-sections in Surfer 14 allowed to distinguish different types of landslide relief, developed in latites and trachybasalts lying above claystones and mudstones. The types vary from small, poorly visible landslides to vast landslides with complex relief. They were interpreted as consecutive stages of geomorphic evolution of hillslope-valley topography of the study area. Two main schemes have been established which explain the development of landslide slopes in the Kamienne Mts: (1) upslope, from the base of the slope towards the mountain ridge and (2) downslope, beginning on the top of the mountain ridge. The direction of landslide development depends on the thickness of volcanic rocks in relation to underlying sedimentary rocks. When the latter appear only in the lowest part of the slope, landslides develop upslope. If sedimentary rocks dominate on the slope and volcanic rocks form only its uppermost part, landslides develop downslope. The results show that landsliding leads to significant modifications of relief of the study area, including complete degradation of mountain ridges.

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Peretyazhko, Igor S., et Elena A. Savina. « Chemistry and Crystallization Conditions of Minerals in Metasomatized Oceanic Lithosphere and Basaltic Rocks of Govorov Guyot, Magellan Seamounts, Pacific Ocean ». Minerals 12, n^o 10 (16 octobre 2022) : 1305. http://dx.doi.org/10.3390/min12101305.

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Studies have provided first detailed data on the chemistry of rock-forming, minor, and accessory minerals of Govorov Guyot volcanic rocks (basalts, trachybasalts, basaltic trachyandesites, and trachyandesites). Some basalt samples bear pargasitic amphibole and clinopyroxene xenocrysts, mantle vein fragments in xenoliths, as well as wehrlite xenoliths, which are remnants of metasomatized oceanic lithosphere. Amphiboles make up a continuous series from pargasite –Mg-hastingsite in wehrlite xenoliths and xenocrysts to Mg-hastingsite – kaersutite end-members in phenocrysts and microlites of basaltic rocks. The discussed issues include the trace element chemistry of Ti-amphibole and clinopyroxene phenocrysts; fractionation of OIB melts; and P-T equilibration of minerals during the formation of mantle and basaltic rocks. Pargasitic amphibole may have crystallized at P-T conditions (2.5–0.6 GPa, 1170–980 °C) corresponding to the spinel facies of peridotite at different depths (73–21 km) in hydrous (6.0–4.5 wt % H2O) silicate mafic melts that percolated through peridotites of the oceanic lithosphere. Ti-amphibole in basaltic rocks crystallized at 1.2–0.4 GPa (40–15 km), and 1060–910 °C from melts containing 8.6–2.6 wt % H2O. As the high-temperature (~1100 °C) basaltic magmas reached chambers at the oceanic crust level (7 to 3 km), the Ti-bearing amphiboles of xenocrysts and phenocrysts became replaced by Ti-magnetite- and/or rhönite-bearing mineral assemblages.

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Kim, Cheolhong, Naing Aung Khant, Yongmun Jeon, Heejung Kim et Chungwan Lim. « Geochemical Characterization of Intraplate Magmatism from Quaternary Alkaline Volcanic Rocks on Jeju Island, South Korea ». Applied Sciences 11, n^o 15 (30 juillet 2021) : 7030. http://dx.doi.org/10.3390/app11157030.

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The major and trace elements of Quaternary alkaline volcanic rocks on Jeju Island were analyzed to determine their origin and formation mechanism. The samples included tephrite, trachybasalts, basaltic trachyandesites, tephriphonolites, trachytes, and mantle xenoliths in the host basalt. Although the samples exhibited diversity in SiO2 contents, the relations of Zr vs. Nb and La vs. Nb indicated that the rocks were formed from the fractional crystallization of a single parent magma with slight continental crustal contamination (r: 0–0.3 by AFC modeling), rather than by the mixing of different magma sources. The volcanic rocks had an enriched-mantle-2-like ocean island basalt signature and the basalt was formed by partial melting of the upper mantle, represented by the xenolith samples of our study. The upper mantle of Jeju was affected by arc magmatism, associated with the subduction of the Pacific Plate beneath the Eurasian Plate. Therefore, we inferred that two separate magmatic events occurred on Jeju Island: one associated with the subduction of the Pacific Plate beneath the Eurasian Plate (represented by xenoliths), and another associated with a divergent setting when intraplate magmatism occurred (represented by the host rocks). With AFC modeling, it can be proposed that the Jeju volcanic rocks were formed by the fractional crystallization of the upper mantle combined with assimilation of the continental crust. The xenoliths in this study had different geochemical patterns from previously reported xenoliths, warranting further investigations.

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Silaev, V. I., L. P. Anikin, G. A. Karpov, D. N. Remizov, A. S. Myandin, V. N. Filippov, A. F. Khazov, V. P. Lyutoev et D. V. Kiseleva. « BUBBLING LAVAS OF THE DIAMOND-BEARING TOLBACHIK FISSURE ERUPTION OF 2012-2013 (TTE-50, KAMCHATKA) ». Вестник Пермского университета. Геология 21, n^o 3 (2022) : 193–215. http://dx.doi.org/10.17072/psu.geol.21.3.193.

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The results of comprehensive petrological, geochemical, and mineralogical studies of effusive volcanic rocks from the diamond-bearing Tolbachik fissure eruption of 2012-2013 (TTI-50) are summarized. It is concluded that the eruption was two-phase, which began with a short-term eruption of trachybasalts and continued with the formation of trachyandesite basalts. In comparison with lavas from other Tolbachik eruptions (BTTI, BD), the studied volcanic rocks are characterized by higher alkalinity and high K content (up to shoshonites), but lower Mg content. In terms of geochemical properties, they correspond to riftogenic magmatites formed due to the deep-mantle chamber of picrite magma. The studied volcanic rocks are characterized by widely varying vesicularity up to bubbly lavas, which comprise 80-90% of volcanic glass, and whose degree of recrystallization varies from maximum in basaltic trachyandesite to minimum in trachyandesitebasalt bomb. According to the degree of iron oxidation in the glass phase, volcanics correspond to the products of terrestrial eruptions in an island-arc or continental-rift geodynamic setting. The microlites are dominated by olivine Fo56-84, plagioclases An87±9 Ab9±10 Ort4±2, and spinel solid solutions based on magnetite, magnoferrite, ulvite, and cuprospinel. Individuals of decomposition in phase-heterogeneous grains of magnetite are represented by hemoilmenite and ilmenite. As accessory microminerals, jirite-spionkopite of composition Cu1.7S-Cu1.32S, native iron composed of Fe75Sn4(Cu,Mn,Cr), and native copper of composition Cu7-10(Sn0.9-1.8Fe0.1-0.2)1-2

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Ferlito, C., M. Coltorti, R. Cristofolini et P. P. Giacomoni. « The contemporaneous emission of low-K and high-K trachybasalts and the role of the NE Rift during the 2002 eruptive event, Mt. Etna, Italy ». Bulletin of Volcanology 71, n^o 5 (30 septembre 2008) : 575–87. http://dx.doi.org/10.1007/s00445-008-0243-9.

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Andronikov, A. V., S. F. Foley et B. V. Beliatsky. « Sm-Nd and Rb-Sr isotopic systematics of the East Antarctic Manning Massif alkaline trachybasalts and the development of the mantle beneath the Lambert-Amery rift ». Mineralogy and Petrology 63, n^o 3-4 (1998) : 243–61. http://dx.doi.org/10.1007/bf01164153.

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Koloskov, A. V., M. Yu Puzankov, V. V. Ananiev et D. V. Kovalenko. « BOLSHOI PAYALPAN VOLCANO (SREDINNY RANGE, KAMCHATKA). PROBLEMATIC ASPECTS OF CONVERGENCE OF ISLAND-ARC AND INTRAPLATE PETROLOGICAL AND GEOCHEMICAL SIGNATURES IN THE MAGMATIC SYSTEM ». Tikhookeanskaya Geologiya 41, n^o 2 (2022) : 3–24. http://dx.doi.org/10.30911/0207-4028-2022-41-2-3-24.

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The paper presents the data on age, mineralogy, geochemistry, and isotope composition of rocks from the Bolshoi Payalpan Volcano (Sredinny Range, Kamchatka). We compared these data with those on the Nosichan and Belogolovsky volcanoes, located within the Belogolovsky volcanic center. The basalts of the neck and the upper lava complex of Bolshoi Payalpan are compositionally similar to the intraplate-type trachybasalts of the Belogolovsky Volcano, and the basaltic andesites of the lower lava and the cone complex are similar to the island arc rocks of the Nosichan Volcano. Analysis of the data obtained evidences that spatial and temporal manifestations of intraplate and island-arc volcanism at the Bolshoi Payalpan Volcano are not accidental, but may be a consequence of a change in the degree and depth of melting of the same deep source with the involvement of a mantle diapir. The Belogolovsky volcanic center formed in a setting of the Late Miocene-Early Pliocene rifting. Its evolution, right up to its extinction, proceeded in the same geodynamic setting with an increase in depth of the mantle source and a decrease in the degree of its melting. Rock compositions of the Lower-Middle Pliocene Nosichan Volcano remain of the island-arc type under conditions of rifting, since they are associated with the mantle reservoir located at a shallower depth, which has experienced a higher degree of melting. There is good reason for considering large volcanic centers as spontaneously-developing geological entities. As the endogenous activity dies down, the degree of melting decreases and the depth of melting increases with the replacement of island-arc volcanism by intraplate volcanism. The volcanic center becomes extinct.

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Demko, Rastislav, Marián Putiš, Qiu-Li Li, David Chew, Lukáš Ackerman et Ondrej Nemec. « Miocene Volcanism in the Slovenský Raj Mountains : Magmatic, Space, and Time Relationships in the Western Carpathians ». Minerals 14, n^o 1 (19 décembre 2023) : 9. http://dx.doi.org/10.3390/min14010009.

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The Miocene volcanic-intrusive complex in the Slovenský Raj Mountains, middle Slovakia, comprises a swarm of subalkaline basalts and basaltic andesites with alkaline basalts, trachybasalts and basaltic trachyandesites. Basaltic to doleritic feeder dykes and sporadic hyaloclastite lavas are exposed in contact with the Triassic Bódvaszilas Formation of the Silica Nappe. The primary clinopyroxene, plagioclase, and Fe-Ti oxide assemblage also contains calcite spheroids inferred to represent carbonatitic melt. These spheroids are associated with subsolidus chlorite, actinolite, magnetite, titanite, calcite, and epidote. Micropoikilitic clinopyroxene, albite, and Ti-magnetite formed due to rapid quenching. There was an incorporation of host rock carbonate during the eruption. The erupted products are the result of magmatic differentiation of the parental basaltic tholeiitic magma with a redox of ∆QFM = +1 to +3, affected by varying degrees of 0%–50% fractionation and the assimilation of carbonate material in a shallow magmatic reservoir. REE geochemistry shows N-MORB-like type patterns with both LaN/YbN and LaN/SmN < 1 at near constant Eu/Eu* (~0.9). This is supported by εNd(t=13 Ma) values of +8.0 to +7.4 determined from the basaltic rocks. The REE values can be modeled by 1% fractional melting of garnet peridotite mixed with 7% melting of spinel peridotite of PM composition (1:9 proportions). SIMS and LA-ICP-MS U/Pb analysis of zircons yields a concordant age of 12.69 ± 0.24 Ma and a 13.3 ± 0.16 Ma intercept (Serravallian) age. The Middle Miocene volcanic activity was related to subduction-collision processes along the boundary of the Cenozoic ALCAPA (Alps–Carpathians–Pannonia) microplate and the southern margin of the European plate.

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Nikishin, Anatoliy M., Sergey G. Skolotnev, Gillian R. Foulger, Elizaveta A. Rodina, Kseniya F. Aleshina, Henry W. Posamentier et Andrey A. Chernykh. « CRUSTAL STRUCTURE OF THE MENDELEEV RISE IN THE ARCTIC OCEAN : A SYNTHESIS OF SEISMIC PROFILES AND ROCK SAMPLING DATA ». Ser-5_2023_4, n^o 6_2023 (20 février 2024) : 3–15. http://dx.doi.org/10.55959/msu0579-9406-4-2023-63-6-3-15.

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The Mendeleev Rise is located in the Amerasia Basin of the Arctic Ocean. The work is based on a synthesis of interpretation of regional seismic profiles of the OGT 2D DOM and data from rock sampling using special underwater vehicles on the slopes of seamounts and scarps. The uplift is represented by alternation of highs (horsts) and half-grabens. At the base of the horst sections, bright reflectors are distinguished, which are interpreted as volcanics. Half-graben sections are wedge-shaped in section and are similar in geometry to seaward-dipping reflectors (SDRs) of continental passive volcanic margins. Rock sampling has shown that the horsts are composed of sedimentary rocks of Palaeozoic age, penetrated by intrusions. Aptian-Albian sections with volcanics (basalts, trachybasalts, trachyandesites) were identified on the horsts. U/Pb dating of igneous rocks showed that typical age of rocks is 110-114 Ma. Magmatic Cretaceous rocks contain zircons with ages ranging from pre-Barremian Mesozoic to Palaeozoic and Precambrian. These zircons were captured by basaltic magma during its upward movement. The presence of these ancient zircons indicates that the Mendeleev Rise is composed of continental crust. A model of the crustal structure of the Mendeleev Rise is proposed. The base of the section visible on seismic profiles is dominated by volcanics (on horsts from basalts to trachyandesites, in half-grabens mainly basalts). The upper and lower crust is approximately 20-30% saturated with intrusions of basic composition. At the base of the crust, a high-velocity layer up to 5 km thick is distinguished. It is assumed that its lower part is entirely represented by gabbro-type intrusions, and the upper part is the lowest part of the lower crust, maximally saturated with intrusions.

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Krivolutskaya, Nadezhda, Valery Mikhailov, Bronislav Gongalsky, Dmitry Kuzmin et Natalia Svirskaya. « The Permian-Triassic Riftogen Rocks in the Norilsk Area (NW Siberian Province) : Geochemistry and Their Possible Link with PGE-Cu-Ni Mineralization ». Minerals 12, n^o 10 (24 septembre 2022) : 1203. http://dx.doi.org/10.3390/min12101203.

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The volcanic rocks in the Vologochan syncline, the Khikey River valley, and Mount Sunduk, within the Norilsk area in the NW Siberian large igneous province, have been studied. They belong to the Ivakinsky, Syverminsky, Gudchikhinsky, Khakanchansky, Nadezhdinsky, Tuklonsky, and Morongovsky Formations. These Formations consist of trachybasalts, picritic basalts and tholeiitic basalts with aphyric and porphyritic textures, and intersertal and poikiloofitic structures. For the first time, we demonstrate the variations in the structure and composition of these Formations along the strike, based on 151 analyses of the major and trace elements in the rocks. The thickness of all the Formations, excepting the Morongovsky, reduce dramatically from the Yenisey–Khatanga trough to the Tunguska syneclise, and they pinch out in the east of the Norilsk area and are attributed to riftogen (rift) basalts. The rock compositions also change in this direction, especially in the Gudchikhinsky and Nadezhdinsky Formations. The two subformations of the Gudchikhinsky formation, the lower and upper, disappear in the east, so the Gudchikhinsky consists only of high-Mg rocks, picritic basalts, and picrites. The composition of the Nadezhdinsky formation varies intensely in its (Gd/Yb)n and (Th/Nb) ratios from the Vologochan syncline to the Khikey River valley. These structural and compositional variabilities differ between the rift formations and the platform ones. Two gabbro–dolerite sills from these areas that are close to the Norilsk and Ergalakh intrusive complexes have been studied. The metal contents in volcanic and intrusive rocks are similar and do not differ from the barren rocks of the South Pyasinsky massif comprising the PGE-Cu-Ni deposits. Only the Gudchikhinsky Formation contains elevated Cu and Ni concentrations. These features and the coinciding spatial distribution of the ore-bearing intrusions and picrites of the Gudchikhinsky rocks in the Norilsk–Igarka paleorift suggest their genetic link. It is proposed that the initial sulfides could have been formed in the mantle, as the Gudchikhinsky picrites, transported to the lower crust, and then involved by the trap magmas in the origin of the ore-bodies in the Norilsk deposits.

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Fazliakhmetov, A. M. « Geochemical features and formation conditions of Early-Devonian cherty-argillaceous shales and the underlying basalts in the Ishkildino section (eastern slope of the Southern Urals) ». LITOSFERA, n^o 1 (17 mars 2019) : 30–47. http://dx.doi.org/10.24930/1681-9004-2019-19-1-30-47.

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Research subject.The West Magnitogorsk zone of the Southern Urals in the vicinity of the Ishkildino village features a subaerially exposed basaltic sequence superposed by cherts and siliceous-clay shales. The basalts and the overlying shales are assumed to have formed during the Ordovician and Silurian (?)–Early Devonian (up to the conodont zone excavates inclusive) periods, respectively. The aim of this research was to reconstruct, using geochemical data, the conditions under which the rocks present in this geological location were formed.Materials and methods. Five samples of the basalts (XRD and ICP-MS methods), 27 samples of the siliceous-clay shales and 10 samples of the cherts (XRD and ICP-AES methods) were analyzed.Results.According to the ratio of SiO2, Na2O and K2O, the volcanic rocks from the lower part of the section are represented by basalts and trachybasalts. Their geochemical composition corresponds to the N-MORB and is established to be similar to that of the basalts in the Polyakovskaya formation (the Middle–Upper Ordovician). In terms of main elements, the shales under study consist of quartz and illite with a slight admixture of organic matter, goethite, quartzfeldspar fragments, etc. The degree of the sedimentary material weathering according to the CIA, CIW and ICV index values is shown to be moderate. The values of Strakhov’s and Boström’s moduli correspond to sediments without the admixture of underwater hydrothermal vent products. The values of Cr/Al, V/Al and Zr/Al correspond to those characteristic of deposits in deep-water zones remote from the coasts of passive and active continental margins, basalt islands and areas adjacent to mid-ocean ridges. For most samples, the values of Ni/Co, V/Cr, Mo/Mn are typical of deposits formed under oxidative conditions. However, several samples from the upper part of the section, which is comparable to the kitabicus and excavatus conodont zones, demonstrate the Ni/Co, V/Cr, and Mo/Mn values corresponding to deposits formed under reducing atmospheres. An assumption is made that the existence of these deposits can be associated with the Bazal Zlichov event.Conclusion.The investigated pre-Emsian shales have shown no signs of volcanic activity in the adjacent areas. The studied deposits are established to correspond to the central part of the Ural Paleoocean.

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Guilbaud, Marie-Noëlle, Claus Siebe, Christine Rasoazanamparany, Elisabeth Widom, Sergio Salinas et Renato Castro Govea. « Petrographic, Geochemical and Isotopic (Sr–Nd–Pb–Os) Study of Plio-Quaternary Volcanics and the Tertiary Basement in the Jorullo-Tacámbaro Area, Michoacán-Guanajuato Volcanic Field, Mexico ». Journal of Petrology 60, n^o 12 (1 décembre 2019) : 2317–38. http://dx.doi.org/10.1093/petrology/egaa006.

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Abstract The origin of the large diversity of rock types erupted along the subduction-related Trans-Mexican Volcanic Belt (TMVB) remains highly debated. In particular, several hypotheses have been proposed to explain the contemporary eruption of calc-alkaline and alkaline magmas along the belt. The Michoacán-Guanajuato Volcanic Field (MGVF) is an atypical, vast region of monogenetic activity located in the western-central part of the TMVB. Here we present new petrographic, geochemical, and isotopic (Sr–Nd–Pb–Os) data on recent volcanics in the Jorullo-Tacámbaro area that is the closest to the oceanic trench. TMVB-related volcanics in this area are Plio-Quaternary (<5 Ma) and mainly form a calc-alkaline series from basalts to dacites, with rare (<5 vol. %) alkaline rocks that range from trachybasalts to trachydacites, and transitional samples. Crystal textures are consistent with rapid crystallization at shallow depth and processes of mixing of similar magma batches (magma recharge). All of the samples exhibit an arc-type trace element pattern. Alkaline and transitional magmas have higher Na2O and K2O, lower Al2O3, and higher concentrations in incompatible elements (e.g. Sr, K, Ba, Th, Ce, P) compared to calc-alkaline rocks. Calc-alkaline rocks are similar isotopically to transitional and alkaline samples, except for a few low 87Sr/86Sr samples. Sr, Nd and Pb isotopes do not correlate with MgO or 187Os/188Os, indicating that they were not significantly influenced by crustal contamination. Isotopic and trace-element systematics suggest that the Tacámbaro magmas are produced by melting of a mantle wedge fluxed by fluids derived from a mixture of subducted sediments and altered oceanic crust. Alkaline and transitional magmas can be derived from a lower degree of partial melting of a similar source to that of the calc-alkaline rocks, whereas the few low 87Sr/86Sr calc-alkaline rocks require a lower proportion of fluid derived from oceanic sediments and crust. Volcanism at the trenchward edge of the MGVF was thus driven purely by subduction during the last 5 Ma, hence discarding slab rollback in this sector of the TMVB.

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Babayeva, Gultekin J. « Petrological-mineralogical evolutional transformation of Cretaceous teschenite-tephrite, syenite-trachyte, and essexite-trachybasalt primary meltings (Carpathian, Caucasian and North TransBaikal regions) ». Journal of Geology, Geography and Geoecology 32, n^o 3 (25 septembre 2023) : 450–60. http://dx.doi.org/10.15421/112340.

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This article discusses spatial and time distribution of Cretaceous teschenite-tephrite and essexite-trachybasalt complexes of the Carpathian, Caucasian, North TransBaikal regions. The main aim of the article is a comparative analysis of petrological-mineralogical features of similar complexes located in the Carpathians, North Caucasus and Transbaikal, Georgia in the Khojavand depression in the southeast of the Lesser Caucasus. Rocks of teschenite-tephrite, essexite-trachybasalt complexes were formed in the Cretaceous, early Eocene and Miocene. The differentiates of the considered complexes are localized in graben-like structures. The initial stage of graben formation is associated with the formation of rocks of the essexite-trachybasalt complex. The next stage of this process is associated with the formation of the teschenite-tephrite complex. According to stages of bedding and develop- ment of riftogenic graben structures, the essexite-trachybasalt complex formed first, at a mature stage – teschenite-tephrite one. At the initial stage high titanian olivine subalkaline basaltic melting occurred from the garnet-phlogopite lherzolite substratum. At the second stage – subalkaline picrite melting occurred from this substratum, which is primary for teschenite-tephrite and syenite-trachyte com- plexes. The metasomatized high-titanium phlogopite lherzolite substrate was subjected to melting twice. An earlier stage of melting of the substrate did not exceed 0.1%, from which a high-titanium olivine trachybasalt melt was separated. The second stage of melting of the substrate reached 10-12%. In this case, a subalkaline olivine picrite melt was formed. Evolution of primary meltings occurred in different-depth intermediate foci and intrusive chambers. The main factor in evolution along with controlling geodynamic regime was gravitational-crystallized differentiation. The identified mineral parageneses, starting from the early stage of the evolution of the subalkaline picrite melt to the late one, actually characterize the stages of crystallization of the noted melt in the intrusive chamber and intermediate chambers. The Eocene and Miocene teschenite-tephrite and essexite-trachybasalt complexes are characterized by a smaller areal distribution and petrographic diversity. Obviously, during this period, the intense activation of transverse magma-feeding faults contributed to the rapid uplift of the subalkaline picrite melt into the upper horizons of the earth’s crust.

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MAALOE, S., I. SORENSEN et J. HERTOGEN. « The Trachybasaltic Suite of Jan Mayen ». Journal of Petrology 27, n^o 2 (1 avril 1986) : 439–66. http://dx.doi.org/10.1093/petrology/27.2.439.

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Yea, Nam Hee, Sung-Hyo Yun et Jeong Seon Koh. « Plagioclase Composition of Feldspar Trachybasalt in Jeju Island ». Journal of the Petrological Society of Korea 21, n^o 3 (30 septembre 2012) : 309–33. http://dx.doi.org/10.7854/jpsk.2012.21.3.309.

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Malobela, T., B. Mapani, M. Harris, D. H. Cornell, A. Karlsson, A. K. Jonsson, C. Lundell et M. Kristoffersen. « Age and geological context of the Barby Formation, a key volcanic unit in the Mesoproterozoic Sinclair Supergroup of southern Namibia ». South African Journal of Geology 122, n^o 4 (1 décembre 2019) : 519–40. http://dx.doi.org/10.25131/sajg.122.0038.

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Abstract Volcanic and sedimentary rocks of the Sinclair Supergroup occur in the Konkiep Terrane of Southern Namibia. Three volcanic and sedimentary cycles are recognised. In this work we describe and date volcanic rocks of the Barby Formation, a key unit in the Sinclair area. The coeval Spes Bona Syenite and the Tiras Granite Gneiss are also described and dated. The rock types in the Barby Formation are rhyolites, basaltic trachyandesites, trachybasalts and trachydacites as well as volcanoclastic rocks. The rocks are largely undeformed and partly altered by deuteric and contact metamorphic processes but not regionally metamorphosed. Our samples represent both the calc-alkaline and alkaline trends documented in previous work. U-Pb ion probe and laser ablation inductively coupled plasma (LA-ICP) multicollector mass spectrometer Lu-Hf microbeam analyses were made of zircon and baddeleyite grains from four samples. A felsic tuff sample from the base of the Barby Formation has a 207Pb/206Pb zircon age of 1214 ± 5 Ma (2σ). A rhomb porphyry sample from the top of an 8.5 km-thick stratigraphic section gives a 207Pb/206Pb baddeleyite age of 1217 ± 2 Ma. The Spes Bona Syenite which intrudes the top of the Barby Formation has a 207Pb/206Pb baddeleyite age of 1217 ± 3 Ma and an indistinguishable LA-ICP collision cell mass spectrometer Rb-Sr biotite isochron age of 1238 ± 20 Ma, showing that there was no >350°C regional metamorphic event. Multi-element diagrams for the calc-alkaline samples show a dominant signature of reworked crust which is superimposed on a possible subduction signature. However the alkaline samples contain clear subduction signatures which are not seen in the underlying 1.37 Ga Kumbis rhyolite. The Barby Formation samples and coeval Spes Bona Syenite have Lu-Hf crustal residence ages between 1682 and 1873 Ma, suggesting that both of these units formed from a mixture of juvenile mantle-derived and older crustal material. The Barby Formation is considered to have originated due to a subduction event which took place during the assembly of the Rodinia supercontinent. The duration of the Barby magmatic episode is constrained to a maximum 9 m.y. period between 1219 and 1210 Ma, and during this period the Konkiep Terrane was an active continental margin. The 1204 ± 9 Ma Tiras Granite Gneiss is slightly younger than the Barby Formation and intruded across the Lord Hills Shear Zone, which is the suture between the hardly metamorphosed Konkiep Terrane and the highly metamorphosed Grunau Terrane of the Namaqua-Natal Province. Its intrusion reflects the end of subduction-related volcanism, due to the collision of Namaqua terranes with the Konkiep Terrane.

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Hafidhah Nurul Haq, Mega Fatimah Rosana, Cipta Endyana, Katon Sena Ajie Nugraha et Irpan Alamsyah. « Geochemistry of Igneous Rocks of Citirem Formation and Its Implications for the Tectonic Setting in Ciletuh – Palabuhanratu UNESCO Global Geopark Area ». Journal of Geoscience, Engineering, Environment, and Technology 9, n^o 1 (28 mars 2024) : 58–68. http://dx.doi.org/10.25299/jgeet.2024.9.1.14367.

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The igneous rocks of the Citirem Formation in the Ciletuh – Palabuhanratu UNESCO Global Geopark area petrographically not only consist of basalt, but also andesite, dacite, and gabbro. The characteristics of basalts Citirem Formation are composed of plagioclase 43% – 58% and olivine, mostly have amygdaloidal and aphanitic textures. Andesites are composed of 45% – 65% plagioclase, absence of olivine, mostly aphanitic and trachytic, some have intergranular textures. Dacite comprises 50% plagioclase, 20% quartz, and the absence of olivine, and aphanitic, intersertal textures. Gabbros are composed of 62% plagioclase, 6% – 12% olivine, with phaneritic texture. Based on the plot of the major elements vs SiO2 diagram, MgO, FeOt (Fe2O3+FeO), CaO, and TiO2 show a negative correlation with SiO2. In comparison, Na2O and K2O show a positive correlation with SiO2. The lithology of igneous rocks of Citirem Formation are basalt, trachybasalt, basaltic trachyandesite, trachyandesite, andesite, dacite and gabbro based on a plot of the Na2O+K2O vs SiO2 diagram for volcanic and plutonic rocks. The origin of magma type can be distinguished based on the plot of K2O vs SiO2 diagrams, the igneous rocks of Citirem Formation are divided into low-K, medium-K, high-K, and shoshonite magma series. Dacite STA 2, andesite STA 7, basaltic andesite STA 8, trachyandesite STA 10 and gabbro STA 14 are calc-alkaline based on triangular diagram Th-Hf-Ta-Zr-Nb. Gabbro STA 17 indicates IAT (island arc tholeiite), trachybasalt STA 19, basalt STA 20 and basaltic trachyandesite STA 27 are E-MORB, WPT (within plate tholeiitic), In contrast, trachybasalt STA 28 is WPA (within plate alkali). Primitive mantle long, NMORB-normalized REE patterns and chondrites-normalized show some rocks have distinctive patterns that have similarities with suprasubduction zone ophiolite rocks, MORB of Mirdita ophiolite, and some show similarities with patterns from OIB and E-MORB.

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Wen-Ge, Zhou, Xie Hong-Sen, Zhao Zhi-Dan et Guo Jie. « Garnet Growth in the Early Stage of Trachybasalt-Eclogite Transformation ». Chinese Physics Letters 18, n^o 11 (10 octobre 2001) : 1500–1503. http://dx.doi.org/10.1088/0256-307x/18/11/324.

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Loock, Sébastien, Benjamin van Wyk de Vries et Jean-Marc Hénot. « Clinker formation in basaltic and trachybasaltic lava flows ». Bulletin of Volcanology 72, n^o 7 (10 avril 2010) : 859–70. http://dx.doi.org/10.1007/s00445-010-0362-y.

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Газеев, В. М., А. Г. Гурбанов et И. А. Кондрашов. « Middle Jurassic volcanogenic rocks of the southern margin of the Greater Caucasus and the Abkhazian-Racha zone of the Transcaucasian median massif : geodynamic typification and minerageny ». Геология и геофизика Юга России 13, n^o 3 (26 septembre 2023) : 89–101. http://dx.doi.org/10.46698/vnc.2023.52.78.007.

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Актуальность работы. На южной окраине Большого Кавказа (БК) и смежной с ним Абхазо-Рачинской зоны Закавказского срединного массива распространены среднеюрские вулканиты и ассоциирующие с ними колчеданно–полиметаллические, медно–пирротиновые и свинцово–цинковые рудные объекты. Геохимическое изучение этих вулканитов необходимо для уточнения особенностей развития региона в этот временной период. Целью исследования является получение аналитических данных, уточнение геодинамической позиции и рудной специализации вулканитов. Объектом исследований являлись байосские эффузивные породы «Порфиритовой серии» (ПС), распространенные в Южной Осетии, Абхазии и Краснодарском крае. Методы исследования включали: петрографическое описание пород и их анализы количественными методами XRF, ISP-MS; расчеты геохимических характеристик, анализ дискриминационных диаграмм. Результаты исследования. Установлено, что вулканогенные породы ПС это умеренно- и низкомагнезиальные базальты, трахибазальты, андезибазальты, трахиандезибазальты с калинатровым и натровым типами щелочности. Их исходные расплавы образовались при 1–5% плавлении шпинелевых перидотитов. Производные этих расплавов близки к базальтам Е-MORB типа – Laн/Ybн=1,3–5,4, но от которых, на мультиэлементных диаграммах концентраций несовместимых элементов, они отличаются наличием отрицательных Та, Nb аномалий, положительной аномалией К, а также более высокими концентрациями крупноионных элементов Rb, Ba, Th, U и Sr. На дискриминационных диаграммах фигуративные точки пород группируются в полях пород островных дуг и активных континентальных окраин. Отмечено, что вулканиты ПС, по своим характеристикам близки к породам среднеюрского «Задугового» дайкового пояса БК, но образовались они в более обогащенной флюидными компонентами зоне. Relevance. On the southern margin of the Greater Caucasus (GC) and the adjacent Abkhaz-Racha zone of the Transcaucasian median massif, Middle Jurassic volcanic rocks and associated pyrite-polymetallic, copper-pyrrhotite and lead-zinc ore objects are common. The geochemical study of these volcanites is necessary to clarify the features of the development of the region during this time period. The aim of the study is to obtain analytical data, clarify the geodynamic position and ore specialization of volcanic rocks. The object of research was the Bajocian effusive rocks of the "Porphyrite Series", common in South Ossetia, Abkhazia and the Krasnodar Territory. Research methods included: petrographic description of rocks and their analysis by quantitative methods XRF, ISP-MS; calculations of geochemical characteristics, analysis of discrimination. Results. It has been established that the volcanic rocks of PS are moderately and low magnesian basalts, trachybasalts, andesite basalts, trachyandesite basalts with potassium and sodium types of alkalinity. Their initial melts were formed at 1-5% melting of spinel peridotites. The derivatives of these melts are close to E-MORB type basalts - Laн/Ybн = 1.3–5.4, but from which, on the multi-element diagrams of the concentrations of incompatible elements, they differ in the presence of negative Ta and Nb anomalies, positive K anomalies, as well as higher concentrations of large-ionic elements Rb, Ba, Th, U and Sr. On the discrimination diagrams, figurative rock points are grouped in the rock fields of island arcs and active continental margins. It is noted that PS volcanic rocks are similar in their characteristics to the rocks of the Middle Jurassic "Behind the arc" dike belt GC, but they were formed in a zone more enriched in fluid components.

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Kadyrova, Z. R., I. K. Shokosimov et M. N. Kazakova. « Establishment of the iron-containing phase of the gavasaia porphyrite by the method of mössbauer spectroscopy for obtaining basalt fibers ». NOVYE OGNEUPORY (NEW REFRACTORIES), n^o 6 (30 novembre 2023) : 3–7. http://dx.doi.org/10.17073/1683-4518-2023-6-3-7.

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The results of studies on the determination of the iron-bearing phase of trachybasalt porphyrite of the Karabulak site of the Gavasay deposit of Uzbekistan and their suitability for obtaining basalt fiber by the method of Mössbauer spectroscopy are presented. It has been established that on the basis of this igneous rock it is possible to obtain a continuous basalt fiber without corrective additives for heat-insulating materials.

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Demir, Sinan, Pelin Alaboz, Orhan Dengiz, Hüseyin Şenol, Kamil Yilmaz et Oğuz Başkan. « Physico-chemical and mineralogical changes of lithic xerorthent soils on volcanic rocks under semi-arid ecological conditions ». Earth Sciences Research Journal 26, n^o 4 (28 février 2023) : 291–301. http://dx.doi.org/10.15446/esrj.v26n4.96571.

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This study investigates the mineralogical changes and soil development processes of young soils formed on various bedrocks of volcanic origin under the same land use/land cover and climate conditions. The current study was conducted in Lithic Xerorthent soils formed on tuff, trachybasalt, and trachyandesite bedrock between Sandıklı-Şuhut districts of Afyonkarahisar. The three soil profiles excavated in the study area were classified in Entisols order based on Soil taxonomy. The primary minerals, sanidine and muscovite, and the clay minerals, smectite, kaolinite, and illite, were widely determined in three soil profiles which were named Profile I (PI), Profile II (PII), and Profile III (PIII). According to the chemical alteration index (CIA) values, which indicate weathering, the soils formed on the tuff bedrock were slightly weathered (77.04%). The chemical weathering index (CIW) in the soils' surface horizons formed on the trachybasalt and trachyandesite bedrock are classified as non-weathering rocks with 24.43% and 33.88%. Basic cations are found at high levels in the tuff bedrock. The determination of phillipsite, gismondin and calcite minerals is an indication that the mineral content of the bedrock and the bedrocks have a significant effect on soil formation. The relationship between the bedrock and the soil has been revealed. As a result of the study, it was concluded that there were significant differences in their physico-chemical characteristics, weathering rates, and mineralogical properties. However, they were characterized as young soils since they do not contain any subsurface diagnostic horizons on the volcanic bedrock under the same climatic and land use/land cover conditions.

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Ripa, Magnus, et Michael B. Stephens. « Chapter 9 Continental magmatic arc and siliciclastic sedimentation in the far-field part of a 1.7 Ga accretionary orogen ». Geological Society, London, Memoirs 50, n^o 1 (2020) : 253–68. http://dx.doi.org/10.1144/m50-2017-3.

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AbstractTrachyandesitic to trachybasaltic lavas, interlayered siliciclastic sedimentary rocks and subaerial ignimbrites with a rhyolitic to trachydacitic composition lie unconformably above metamorphic rocks in west-central Sweden. These volcanic rocks erupted at 1711 + 7/−6 to 1691 ± 5 Ma and belong to a high-K, calc-alkaline to shoshonitic suite deposited in a continental arc setting. Positive ɛNd values and Nb/Yb ratios in the trachyandesitic to trachybasaltic rocks indicate an enriched mantle source. Coeval, 1710 ± 11 to 1681 ± 16 Ma plutonic and subvolcanic rocks are mainly granitic or quartz syenitic in composition. Subordinate components include quartz monzonite, quartz monzodiorite and monzogabbro or gabbro. ɛNd values in the range −1.0 to + 1.1 overlap with those in the inferred 1.9–1.8 Ga source rocks. All these rocks belong to the youngest phase of the lithodemic unit referred to as the Transscandinavian Igneous Belt. This magmatic province extends in a roughly NNW direction for at least 900 km, variably deformed and metamorphosed equivalents occurring inside and beneath younger orogenic belts to the south (Sveconorwegian) and north (Caledonian). The part of the province in west-central Sweden addressed here represents a far-field and shallow crustal component in this 1.7 Ga accretionary orogenic system.

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Kadyrova, Z. R., I. K. Shokosimov et M. N. Kazakova. « DETERMINATION OF THE CHEMICAL AND MINERALOGICAL COMPOSITION OF TRACHIBASALTIC PORPHIRITE FROM THE GAVASAY FOR OBTAINING MINERAL FIBER ». Steklo i Keramika, n^o 20 (août 2023) : 56–61. http://dx.doi.org/10.14489/glc.2023.08.pp.056-061.

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The results of studies of the chemical and mineralogical compositions and the main characteristics for determining the suitability of trachybasaltic porphyrite from the Gavasay deposit of Uzbekistan for obtaining heat-insulating material, in particular mineral fiber, are presented. It has been established that this new deposit of igneous rock can be used as the main raw material component for the production of basalt fiber products, a widely demanded and modern material in the construction industry.

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Gomes, Celso De Barros, Ana Maria Castillo Clerici Clerici, Victor Velázquez Fernandez, Angelo De Min et Piero Comin‑Chiaramonti. « The dykes in the western fringe of the Ybytyruzú Hills, central‑eastern Paraguay region ». Geologia USP. Série Científica 17, n^o 2 (1 août 2017) : 131. http://dx.doi.org/10.11606/issn.2316-9095.v17-121977.

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The Cordillera del Ybytyruzú region of central eastern Paraguay is predominantly formed by tholeiitic lava flows from the Early Cretaceous age (130–134 Ma) cut by K alkaline dykes and intrusive bodies aged between 125 and 127 Ma. Petrochemical studies focusing on 14 samples of dykes from the region show an apparent affinity to Roman Province Type rocks and total consistency with the overall petrographic association of the Asunción Sapucai Villarrica (ASV) graben. Two main potassic suites are distinguished: B P (basanite tephrite phonotephrite phonolite) and AB T (alkali basalt trachybasalt trachyandesite trachyphonolite/trachyte).The occurrence of lamproitic rocks in the area has so far not been confirmed.

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Orlando, Andrea D'Orazio, Pietro Armienti et Daniele Borrini. « Experimental determination of plagioclase and clinopyroxene crystal growth rates in an anhydrous trachybasalt from Mt Etna (Italy) ». European Journal of Mineralogy 20, n^o 4 (29 août 2008) : 653–64. http://dx.doi.org/10.1127/0935-1221/2008/0020-1841.

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Leat, P. T., et R. S. Thorpe. « Geochemistry of an ordovician basalt-trachybasalt-subalkaline/peralkaline rhyolite association from the Lleyn Peninsula, North Wales, U.K ». Geological Journal 21, n^o 1 (janvier 1986) : 29–43. http://dx.doi.org/10.1002/gj.3350210103.

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Saputro, Sugeng Purwo, Dwi Ratih Purwaningsih et Bambang Priadi. « Peralihan Rezim Tektonik : Implikasinya pada Konsentrasi Torium di Mamasa dan Tana Toraja, Sulawesi-Indonesia ». EKSPLORIUM 41, n^o 2 (30 novembre 2020) : 87. http://dx.doi.org/10.17146/eksplorium.2020.41.2.6063.

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ABSTRAK Mamasa dan Tana Toraja secara geografis merupakan bagian dari lengan barat Pulau Sulawesi. Batuan-batuan mafik di daerah tersebut dan sekitarnya memiliki nilai laju radiasi tinggi dan anomali kandungan torium (Th). Penelitian ini bertujuan untuk mengetahui mekanisme tataan tektonik yang berperan dalam peningkatan konsentrasi Th. Enam sampel batuan dianalisis menggunakan analisis petrografi dan geokimia (AAS, ICP-MS, NA, dan XRF), dilengkapi dengan pentarikhan umur menggunakan metode 40K-40Ar pada sampel batuan terpilih. Pengamatan petrografi memperlihatkan kehadiran mineral plagioklas, olivin, piroksen, hornblenda, nefelin, dan alanit pada batuan yang diidentifikasi sebagai nefelin-basanit, basalt, trakhibasalt, dan gabro. Sejumlah tekstur yang tampak pada batuan tersebut mengindikasikan kontaminasi dan perubahan kondisi tektonik. Analisis geokimia menunjukkan bahwa nefelin-basanit, basalt, trakhibasalt, dan gabro (absarokit) terbentuk pada batas kontinental aktif (ACM) yang sedang mengalami transisi dari subduksi aktif (penunjaman ke arah barat) menjadi post-subduksi. Perubahan tataan tektonik membuat magma membeku pada kondisi yang sangat ekstrim. Proses pembekuan magma diinterpretasikan terjadi pada umur sekitar 13,10-11,02 Ma. Mekanisme tersebut berperan penting terhadap terjadinya peningkatan konsentrasi torium di Mamasa dan Tana Toraja.ABSTRACT Mamasa and Tana Toraja geographically are part of the western arm of Sulawesi Island. The mafic rocks in these areas and their surroundings have high radiation dose rate and thorium (Th) anomaly content. This research aim is to determine tectonic setting mechanism which play the important role on the increasing of Th concentration. Six rock samples were analysed using petrography and geochemical analyses (AAS, ICP-MS, NA, and XRF) completed with the 40K-40Ar dating on selected rock samples. Petrography observations show plagioclase, olivine, pyroxene, hornblende, nepheline, and allanite minerals presence in the rocks which identified as nepheline-basanite, basalt, trachybasalt, and gabbro. Numbers of texture appearances in the rocks indicate contamination and changes on tectonic setting. Geochemistry analysis shows that nepheline-basanite, basalt, trachybasalt, and gabbro (absarokite) were formed at the active continental margin (ACM), which is undergoing active subduction (westward subduction) to post-subduction transition. The changing of tectonic setting made magma solidify in extreme conditions. The magma solidify process is interpreted to occur at the age of 13.10-11.02 Ma. These mechanisms play an important role for the increase of thorium concentration in Mamasa and Tana Toraja.

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Juvigné, Étienne, et Bruno Bastin. « Téphrostratigraphie et palynologie de tourbes du Boréal et de l’Atlantique dans le massif Central (France) ». Géographie physique et Quaternaire 49, n^o 2 (30 novembre 2007) : 207–16. http://dx.doi.org/10.7202/033037ar.

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RÉSUMÉ La composition chimique des magmas de trois téphras que l'on trouve dans des tourbières en Auvergne a été déterminée. Elle a permis de distinguer la Téphra du Montchal (trachybasalte potassique) de celle du Montcineyre (basanite) qui sont pratiquement synchrones vers 6000 BP. La Téphra de La Taphanei (8500 BP, Boréal) est un trachyte. Deux diagrammes polliniques antérieurs font état de la présence de pollen de Tilia (Atlantique) au niveau de la Téphra de La Taphanei, voire même sous elle. Une nouvelle étude de cinq tourbières démontre : (i) que des grains de pollen isolés de Tilia ne sont pas observés dans plus de 17 % des niveaux d'âge boréal; (ii) que leur présence est plus fréquente au-dessus de la Téphra de La Taphanei; (iii) que la courbe continue de Tilia ne commence que bien au-dessus de la Téphra de La Taphanei, lorsqu'il n'y a pas de lacune dans la séquence.

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Williams-Jones, Glyn, René W. Barendregt, James K. Russell, Yannick Le Moigne, Randolph J. Enkin et Rose Gallo. « The age of the Tseax volcanic eruption, British Columbia, Canada ». Canadian Journal of Earth Sciences 57, n^o 10 (octobre 2020) : 1238–53. http://dx.doi.org/10.1139/cjes-2019-0240.

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A recent volcanic eruption occurred at Tseax volcano that formed a series of tephra cones in northwestern British Columbia, Canada. The explosive to effusive eruption also formed a 32 km long sequence of Fe-rich Mg-poor basanite–trachybasalt lavas covering ∼40 km2. Oral histories of the Nisg_a’a Nation report that the eruption may have caused as many as 2000 fatalities. The actual eruption date and question of whether there was one or multiple eruptive episodes in the 14th and 18th centuries are, as of yet, unresolved. New radiocarbon dating of wood charcoal from immediately beneath vent-proximal tephra deposits and complementary age information suggest an eruption in 1675–1778 CE (95.4% probability) was responsible for the formation of the tephra cone. New paleomagnetic and geochemical data from the tephra cone and lava flows suggest there is, in fact, no statistically significant difference in time between the explosive and effusive deposits and that they formed during a single eruptive episode.

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Mollo, S., J. D. Blundy, G. Iezzi, P. Scarlato et A. Langone. « The partitioning of trace elements between clinopyroxene and trachybasaltic melt during rapid cooling and crystal growth ». Contributions to Mineralogy and Petrology 166, n^o 6 (16 octobre 2013) : 1633–54. http://dx.doi.org/10.1007/s00410-013-0946-6.

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Peretyazhko, I. S., E. A. Savina et S. I. Dril’. « Early Cretaceous trachybasalt-trachyte-trachyrhyolitic volcanism in the Nyalga basin (Central Mongolia) : sources and evolution of continental rift magmas ». Russian Geology and Geophysics 59, n^o 12 (décembre 2018) : 1679–701. http://dx.doi.org/10.1016/j.rgg.2018.12.011.

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Giorgetti, Giovanna, Thomas Monecke, Reinhard Kleeberg et Mark D. Hannington. « Low-temperature hydrothermal alteration of trachybasalt at Conical Seamount, Papua New Guinea : formation of smectite and metastable precursor phases ». Clays and Clay Minerals 57, n^o 6 (1 décembre 2009) : 725–41. http://dx.doi.org/10.1346/ccmn.2009.0570606.

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Zhou, Wenge, Hongsen Xie, Zhidan Zhao, Weiguo Zhu, Jie Guo et Ji’an Xu. « The effect of phase transition on the compressional wave velocity for a trachybasalt at high temperature and high pressure ». Chinese Science Bulletin 44, n^o 15 (août 1999) : 1415–18. http://dx.doi.org/10.1007/bf02885995.

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Moon, Inkyeong, Hyunwoo Lee, Jonguk Kim, Jihye Oh, Donghoon Seoung, Chang Hwan Kim, Chan Hong Park et Insung Lee. « Ti-Magnetite Crystallization in Melt Inclusions of Trachytic Rocks from the Dokdo and Ulleung Islands, South Korea : Implications for Hydrous and Oxidized Magmatism ». Minerals 10, n^o 7 (20 juillet 2020) : 644. http://dx.doi.org/10.3390/min10070644.

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The Dokdo and Ulleung islands (Korea) are volcanic islands in the East Sea (Sea of Japan), formed in the late Cenozoic. These volcanic islands, in the back-arc basin of the Japanese archipelago, provide important information about magma characteristics in the eastern margin of the Eurasian plate. The origin of the Dokdo and Ulleung intraplate volcanism is still controversial, and the role of fluids, especially water, in the magmatism is poorly understood. Here, we comprehensively analyzed the melt inclusions (10–100 m in diameter) hosted in clinopyroxene phenocrysts of trachyte, trachyandesite, and trachybasalt. In particular, we observed Ti-magnetite and amphibole which were crystallized as daughter mineral phases within melt inclusions, suggesting that Ti-magnetite was formed in an oxidized condition due to H2O dissociation and H2 diffusion. The Ti-magnetite exhibited compositional heterogeneities of MgO (average of 8.28 wt %), Al2O3 (average of 8.68 wt %), and TiO2 (average of 8.04 wt %). The positive correlation of TiO2 with Cr2O3 is probably attributed to evolutionary Fe–Ti-rich parent magma. Correspondingly, our results suggested hydrous and oxidized magmatism for the Dokdo and Ulleung volcanic islands.

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Kislov, Evgeniy V., Anna V. Aseeva, Vladislav V. Vanteev, Anton Yurievich Sinyov et Olga A. Eliseeva. « Naryn-Gol Creek Sapphire Placer Deposit, Buryatia, Russia ». Minerals 12, n^o 5 (20 avril 2022) : 509. http://dx.doi.org/10.3390/min12050509.

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A new gem corundum occurrence has been discovered in the Naryn-Gol Creek placer of the Dzhida volcanic field (Russia). In this placer deposit, sapphire associates with large crystals of garnet, spinel, augite, olivine, enstatite, ilmenite, Ti-magnetite, and alkali feldspar. Such a combination of minerals is typical for the placer deposits associated with alkali basalts widely distributed in Southeastern Asia and Australia. We have also found sapphire crystals in phonotephrites of the nearby Cenozoic alkali-basalt paleovolcano Barun Khobol Pravyi, and in basalt sample and trachybasalt from the valley flood basalts. The chemical composition of sapphire is generally typical for ‘basalt’ corundum: it is rich in Fe, and depleted in Ti and Cr. The δ18O SMOW values of corundum and related megacrysts range from 4.6 to 6.8 ‰, thus corresponding to the isotopic signature of igneous rocks. Etched and corroded surfaces of sapphire and other megacrysts indicate that they are in non-equilibrium with their host alkali basalts. Volatile components, CO2 in particular, played a significant role during sapphire formation as gas inclusions reveal.

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Yarmolyuk, V. V., E. A. Kudryashova et A. M. Kozlovsky. « Late stages in the evolution of the late Mesozoic East Mongolian volcanic areal : rock age and composition ». Доклады Академии наук 487, n^o 3 (17 août 2019) : 283–88. http://dx.doi.org/10.31857/s0869-56524873283-288.

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The Mandakh-Madal-Gobi (MMG) zone of alkali basalt magmatism has been delineated in the Late Mesozoic East Mongolian volcanic areal. It comprises clusters of igneous rock bodies and isolated stocks, domes, sills, laccoliths, dikes, and limited fragments of lava flows composed of tephrite, phono-tephrite, and trachybasalt. Two pulses of magmatism in the MMG zone have occurred in the Late Cretaceous (about 85 Ma) and Early Cenozoic (about 50 Ma). Recognition of this zone and deciphering of its formation history demonstrated that the development of the entire East Mongolian volcanic areal had the same regularities as those identified in other major regions of the Late Mesozoic Central Asia magmatic province. This indicates that the areal undoubtedly belongs to the latter. These facts support the conclusion that the correlation observed through the zone’s evolution between reduction in the volume of igneous products and the change in their composition towards the OIB was apparently determined by a decrease in the effect of thermal sublithospheric mantle melts upon a metasomatically enriched lithospheric mantle, leading to its gradual elimination from the magma sources.

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Peretyazhko, I. S., E. A. Savina, N. S. Karmanov et Yu D. Shcherbakov. « Genesis of mugearites and benmoreites of Nemrut Volcano, eastern Turkey : Magma mixing and fractional crystallization of trachybasaltic melt ». Petrology 23, n^o 4 (juillet 2015) : 376–403. http://dx.doi.org/10.1134/s0869591115030042.

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