Search results for " MAntle"
showing 10 items of 75 documents
Fe-periclase reactivity at Earth's lower mantle conditions: Ab-initio geochemical modelling
2017
Intrinsic and extrinsic stability of the (Mg, Fe) O solid mixture in the Fe-Mg-Si-O system at high P, T conditions relevant to the Earth's mantle is investigated by the combination of quantum mechanical calculations (Hartree-26 Fock/DFT hybrid scheme), cluster expansion techniques and statistical thermodynamics. Iron in the (Mg, Fe) O binary mixture is assumed to be either in the low spin (LS) or in the high spin (HS) state. Un-mixing at solid state is observed only for the LS condition in the 23-42 GPa pressure range, whereas HS does not give rise to un-mixing. LS (Mg, Fe) O un-mixings are shown to be able to incorporate iron by subsolidus reactions with a reservoir of a virtual bridgmanit…
Magmatism Along Lateral Slab Edges: Insights From the Diamante-Enotrio-Ovidio Volcanic-Intrusive Complex (Southern Tyrrhenian Sea)
2019
Volcanic‐intrusive complexes often formed along lateral slab edges as a consequence of subduction‐induced mantle flow. We investigate this process in the southern Tyrrhenian Sea by integrating multibeam bathymetry, seismic‐reflection data, regional magnetic anomalies data, and seismological data. The interpretation of the data highlights the presence of magmatic intrusions that locally reach the seafloor forming volcanic edifices. Chimneys, lava flows, and laccoliths are observed beneath and surrounding the volcanoes. The emplacement and cooling of the magma occurred during the Brunhes Chron. The volcanoes are not active even if the hydrothermal activity occurs. The volcanic‐intrusive compl…
New evidence of mantle heterogeneity beneath the Hyblean Plateau (southeast Sicily, Italy) as inferred from noble gases and geochemistry of ultramafi…
2012
Abstract We analyzed major and trace elements, Sr and Nd isotopes in ultramafic xenoliths in Miocenic age Hyblean diatremes, along with noble gases of CO2-rich fluid inclusions hosted in the same products. The xenoliths consist of peridotites and pyroxenites, which are considered to be derived from the upper mantle. Although the mineral assemblage of peridotites and their whole-rock abundance of major elements (e.g., Al2O3 = 0.8–1.5 wt.%, TiO2 = 0.03–0.08 wt.%) suggest a residual character of the mantle, a moderate enrichment in some incompatible elements (e.g., LaN/YbN = 9–14) highlights the presence of cryptic metasomatic events. In this context a deep silicate liquid is considered the me…
Carbonated Inheritance in the Eastern Tibetan Lithospheric Mantle: Petrological Evidences and Geodynamic Implications
2020
International audience; The timing and mechanism of formation of the Tibet Plateau remain elusive, and even the present-day structure of the Tibetan lithosphere is hardly resolved, due to conflicting interpretations of the geophysical data. We show here that significant advances in our understanding of this orogeny could be achieved through a better assessment of the composition and rheological properties of the deepest parts of the Tibetan lithosphere, leading in particular to a reinterpretation of the global tomographic cross sections. We report mantle phlogopite xenocrysts and carbonate-bearing ultramafic cumulates preserved in Eocene potassic rocks from the Eastern Qiangtang terrane, wh…
Ca-rich carbonates associated with ultrabasic-ultramafic melts. Carbonatite or limestone xenoliths? A case study from the late Miocene Morron de Vill…
2016
The volcanic products of the late Miocene Morron de Villamayor volcano (Calatrava Volcanic Field, central Spain) are known for being one of the few outcrops of leucitites in the entire circum-Mediterranean area. These rocks are important because aragonite of mantle origin has been reported as inclusion in olivine macrocrysts. We use petrographic observations, mineral compositions, as well as oxygen and carbon isotope ratios coupled with experimental petrology to understand the origin of carbonate phase in these olivine-phyric rocks. Groundmass and macrocryst olivines range from δ18OVSMOW of +4.8‰, typical of mantle olivine values, to +7.4‰, indicating contamination by sedimentary carbonate.…
Geochemistry, Sr–Nd–Pb isotopes and geochronology of amphibole- and mica-bearing lamprophyres in northwestern Iran: Implications for mantle wedge het…
2015
Highlights • Northwestern Iranian lamprophyres have alkaline and calc-alkaline nature. • Studied lamprophyres are emplaced during Late Cretaceous to Late Miocene time. • Lamprophyres originated from different metasomatised lithospheric mantle. Abstract Lamprophyres of different age showing distinctive mineralogy, geochemistry and isotopic ratios are exposed in northwestern Iran. They can be divided into Late Cretaceous sannaite, Late Oligocene-Early Miocene camptonite (amphibole-bearing) and Late Miocene minette (mica-bearing) and spessartite (amphibole-bearing) lamprophyres. Sannaites have high-Ti amphibole along with high-Ti and Al clinopyroxene, and they are characterised by homogeneous …
Berberido aetnensis-Crataegion laciniatae, new orophilous pre-forestal alliance of the class Rhamno-Prunetea
2011
In this paper the results of a phytosociological study carried out on some aspects of shrub vegetation of forest margins are presented, investigated in the higher belt of the Madonie Mts. (Northern-Central Sicily), referred to the order Prunetalia spinosae (Rhamno-Prunetea). Through comparison with other known coenoses in the central- southern part of the Italian Peninsula and in Sicily – especially, the associations of Berberidion vulgaris and those of Pruno-Rubion ulmifolii – a coenological and phytogeographical autonomy has been made evident and has resulted in the recognition of a new alliance, described under the name Berberido aetnensis-Crataegion laciniatae Gianguzzi et al., all. nov…
The heterogeneity of the Mexican lithospheric mantle: Clues from noble gas and CO2 isotopes in fluid inclusions
2022
The abundance of mantle-derived rocks and lavas, in combination with its tectonic evolution, render Mexico a perfect laboratory to investigate the chemical and the isotopic heterogeneity of the lithospheric mantle. New data on the composition of noble gases and CO2in Mexican mantle xenoliths and lavas is reported. Our samples consist of six ultramafic nodules from the Durango Volcanic Field (DVF) and the San Quintin Volcanic Field (SQVF), monogenetic complexes belonging to the Mexican Basin and Range province; and four lavas from the Sierra Chichinautzin (SCN), a Quaternary monogenetic volcanic field located in the Mexican volcanic arc. Ne and Ar isotopes in fluid inclusions reveal mixing b…
Petrological and noble gas features of Lascar and Lastarria volcanoes (Chile): Inferences on plumbing systems and mantle characteristics
2020
Lascar (5592 m a.s.l.) and Lastarria (5697 m a.s.l.) are Chilean active stratovolcanoes located in the Central Volcanic Zone (CVZ; 16°S to 28°S) that have developed on top of a 71 km thick continental crust. Independently of the similarities in their Plinian/Vulcanian eruptive styles, their complex magmatic feeding structures and the origins of their magmatic fluids still necessitate constraints in order to improve the reliability of geochemical monitoring. Here we investigate the petrography, bulk-rock chemistry, and mineral chemistry in products from the 1986–1993 explosive eruptive cycle at Lascar and from several Holocene eruptive sequences at Lastarria. These data are integrated with m…
3He/4He Ratio in Olivines from Linosa, Ustica, and Pantelleria Islands (Southern Italy)
2011
We report helium isotope data for 0.03–1Ma olivine-bearing basaltic hawaiites from three volcanoes of the southern Italy magmatic province (Ustica, Pantelleria, and Linosa Islands). Homogenous 3He/4He ratios (range: 7.3–7.6 Ra) for the three islands, and their similarity with the ratio of modern volcanic gases on Pantelleria, indicate a common magmatic end-member. In particular, Ustica (7.6 ± 0.2Ra) clearly differs from the nearby Aeolian Islands Arc volcanism, despite its location on the Tyrrhenian side of the plate boundary. Although limited in size, our data set complements the large existing database for helium isotope in southern Italy and adds further constraints upon the spatial exte…