Melilitites are ultramafic magmas characterized by normative Ca₂SiO₄, larnite, high FeO* and TiO₂. Liquids compositionally close to melilitites were experimentally reproduced from carbonated lherzolites in alkali, Fe and Ti-free model systems at 3.2-3.3 GPa, approx.  1500 °C (Gudfinnsson & Presnall, 2005), at relatively high melt proportions. In complex compositions, MORB-eclogite derived, carbonated, partial melts reacted with a fertile peridotite were proposed at the origin of melilitites (Mallik & Dasgupta, 2013, 2014). The experimental reconstruction of phase relationships along a join olivine melilitite - carbonate revealed that at 3 GPa, clinopyroxene and olivine or garnet are stable on the liquidus (Brey & Ryabchikov, 1994), suggesting that carbonated wehrlites are potential sources for the genesis of melilitites.

Here, we explore phase relationships on the high pressure melting of a model wehrlite, initially composed of a mechanical mixture of San Carlos olivine, diopside, aegirine, dolomite, rutile and kyanite. Starting materials were loaded in graphite capsules, inserted in sealed platinum capsules. Vitreous carbon spheres and synthetic diamond grains were adopted for liquid traps. 

Preliminary experimental results show that at 3 GPa the solidus is located at temperatures lower than 1200 °C. A thick, orthopyroxene-rich layer, with polygonal microstructure, forms at contact with aggregates resulting from quenched liquids, both at 1200 °C and 1400 °C. Estimates of liquid composition are melilititic, with TiO₂ approx. 2.5 wt.% on a volatile free basis.

Currently available experiments suggest that the solidus is controlled by the reaction dolomite + olivine + clinopyroxene = orthopyroxene + liquid, as suggested in Eggler (1976). This is feasible only if the liquid composition is located on the CaO-rich side of the plane diopside-forsterite-dolomite in the model system CaO-MgO-SiO₂-CO₂, i.e. on the normative larnite (akermanite) portion of the tetrahedron.

Brey G.P. & Ryabchikov I.D. (1994). Carbon-dioxide in strongly silica undersaturated melts and origin of kimberlite magmas. Neues Jahrbuch Fur Mineralogie-Monatshefte, (10), 449-463.

Eggler D.H. (1976). Does CO₂ cause partial melting in the low-velocity layer of the mantle?. Geology, 4(2), 69-72

Gudfinnsson G.H. & Presnall D.C. (2005). Continuous gradations among primary carbonatitic, kimberlitic, melilititic, basaltic, picritic, and komatiitic melts in equilibrium with garnet lherzolite at 3–8 GPa. Journal of Petrology, 46(8), 1645-1659.

Mallik A. & Dasgupta R. (2013). Reactive infiltration of MORB-eclogite-derived carbonated silicate melt into fertile peridotite at 3 GPa and genesis of alkalic magmas. Journal of Petrology, 54(11), 2267-2300

How to cite: Poli, S. and Melluso, L.: The origin of melilitites: preliminary results on melting of a carbonated wehrlite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16571, https://doi.org/10.5194/egusphere-egu24-16571, 2024.

Venus and Mars have operated as one-plate planets for some or all of their history and intraplate magmatic activity on Earth has been suggested as an analogue for the observed volcanic activity on these bodies. Flipping the question around, what can we learn about intraplate magmatism on Earth from other planets?

Volcanic features, including extensive lava flows and vast lava plains, cover large portions of the Martian surface. Mars has two large volcanic provinces: Tharsis and Elysium. While the continent-sized region of elevated terrain called the Tharsis rise receives most of the attention, Elysium—the second largest volcanic province on Mars—is larger than the Ontong-Java plateau—the largest LIP on Earth. Activity detected by the InSight seismometer near Cerberus Fossae (located in Elysium Planitia, southeast of the Elysium volcanic province) is consistent with fluid flow at depth. Cerberus Fossae is among the youngest tectonic structures on Mars and large discharges of water and lava have been proposed to explain the geomorphic structures observed at Cerberus Fossae. The regional gravity and topography, volcanic history, and seismic activity at Cerberus Fossae are consistent with a present-day 2,000-km-radius plume head beneath Elysium Planitia. The characteristics of the Elysium Planitia plume are comparable to terrestrial plumes proposed to explain the formation of terrestrial LIPs. Plumes on Mars appear to be spatially stable for long periods of time, reflecting the stabilizing influence of a thick stagnant lid and sluggish mantle convection.

While Venus is nearly the same size as Earth, there is no evidence supporting Earth-like plate tectonics for the past 250-750 Myrs. The similarity in size invites comparison of present-day volcanic activity between the two planets. This is complicated by the presence of plate tectonics where volcanic activity at ridges and subduction zones has no clear analogue on Venus. Expanding intraplate volcanism on Earth suggests as many as 100 active volcanic events per year on Venus. While detecting surface changes is one goal of the upcoming NASA and ESA Venus missions, surface change associated with volcanic activity has already been found in the Magellan image archive. Herrick and Hemsley identified a 2 km² volcanic vent that changed shape in the eight months between two Magellan radar images. While sulfuric acid clouds obscure our view of the surface, those same clouds provide the best evidence for ongoing volcanic activity. Assuming the primary mechanism removing atmospheric SO₂ is a reaction between calcium minerals on the surface and SO₂, an SO₂ residence time of ~2 Myrs is required. This requires an outgassing rate of ~6x10¹⁰ kg SO₂/year—about the same yearly SO₂ outgassing rate measured on Earth over the past decade. Converting this outgassing rate to erupted lava, an eruption rate on Venus of ~1 km³/yr is obtained.

How to cite: King, S., Duncan, M., Euen, G., Murphy, J., Parrish, S., and Weller, M.: Can Venus and Mars Inform Us About Intraplate Magmatism on Earth?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5761, https://doi.org/10.5194/egusphere-egu24-5761, 2024.

The Tibetan lateral mantle flow bears considerable significance in deciphering the material movement mechanisms within global plate convergence zones. However, the front edge of this mantle flow is unclear. Here we conduct petrological, geochronological, mineralogical, geochemical and Sr-Nd-Pb isotopic investigations on Quaternary intracontinental alkali basalts from the southwestern Yunnan (the south of 27°N), to determine the source characteristics and geodynamic mechanisms of the Quaternary alkali basalts in southeastern Tibetan Plateau and to trace the recent Tibetan mantle flow. Alkali basalts in the region are mainly basanite and trachybasalt with eruptions during the Pleistocene epoch. They possess a highly incompatible elemental and radiogenic Sr-Nd-Pb isotopic composition similar to those of the Ocean Island Basalts, consistent with melts derived from asthenospheric mantle with low-degree partial melting. Calculated magma-water contents of regional alkali basalts range from 1.32 ± 0.48 wt.% to 2.23 ± 0.18 wt.%, corresponding to 269 ppm to 3591 ppm water contents of their mantle source, which are significantly higher than that of the normal upper mantle (i.e., 50–250 ppm). Quantitative trace-element modelling and dramatic variations in oceanic crust-sensitive indicators such as Eu/Eu*, Sr/Sr*, Ce/Pb, (Nb/Th)_N-PM and (Ta/U)_N-PM indicate variable contributions of upper and lower oceanic crust to magma sources. Systematic examinations of petrological, geochemical, and geophysical evidence reveal that the temporary small-volume Quaternary volcanism in southeastern Tibetan Plateau is not related to Tibetan southeastward mantle flow but is primarily attributed to stagnant Neo-Tethyan slab in the mantle transition zone.

How to cite: Kang, H., Zhao, Y., Zhang, X., Zhang, L., Zhang, H., and Zou, H.: Quaternary volcanism in southeastern Tibetan Plateau: A record of stagnant oceanic slab in the mantle transitional zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7403, https://doi.org/10.5194/egusphere-egu24-7403, 2024.

The geodynamic regime driving formation of Archean felsic continent crust is still an ongoing debated and unsolved fundamental issue. The episodic Archean TTGs and associated granitoids, with emplacement ages of ca. 2.9, 2.7 and 2.5 Ga, occurred in the Jiaobei Terrane, North China Craton (NCC), provide prolonged continuous records of formation processes of Meso-Neoarchean felsic continental crust. To track patterns of crust-mantle differentiation, crustal reworking and recycling, and accordingly, constrain underlying geodynamic regimes associated with formation of the Meso-Neoarchean felsic continental crust, we present comprehensive zircon U-Pb dating, Hf-O isotopes and whole-rock major- and trace-element geochemical data for the episodic Archean TTGs and associated granitoids. The comprehensive dataset decodes the generation of the episodic Archean TTGs over wide-range pressure conditions from amphibolite to eclogite facies and Meso-Neoarchean coupled crust-mantle differentiation, which was likely driven by episodic hot mantle (plume) upwelling. In addition, the ca. 2.9 and 2.7 Ga TTGs shared identical Mesoarchean juvenile crust source and exhibit consistent mantle-like zircon δ¹⁸O values, whereas the ca. 2.5 Ga TTGs mainly derived from distinctly younger Neoarchean juvenile crust, implying removal and replacement of the Mesoarchean juvenile lower crust. Importantly, some ca. 2.5 Ga TTGs, granitic gneisses and sanukitoids exhibit significantly higher zircon δ¹⁸O values than mantle δ¹⁸O values, demonstrating occurrence of Neoarchean supracrustal recycling. Consequently, the combined geochemical dataset with geological evidence allow us to track the geodynamic processes for the formation of the Meso-Neoarchean felsic continent crust in the Jiaobei Terrane, NCC: Episodic hot upwelling mantle (plume)-lithosphere interactions at ca. 2.9, 2.7 and 2.5 Ga resulted in the coupled crust-mantle differentiation over different depths to produce the spatial-temporally coexisted various-pressure-type TTGs, juvenile crust and voluminous dense lower crustal restite, respectively. Subsequently, dense lithospheric delamination triggered by gravitational instability occurred, followed by continental uplifting, subduction of altered oceanic crust, and asthenosphere and mantle-derived mafic melts upwelling, resulting in extensive occurrences of anatexis and metamorphism with anticlockwise P-T paths in the medium-lower crust at ca. 2.5 Ga. Along with large-scale melting and cooling of mantle, thick stable craton lithosphere with strong rigidity and viscosity had likely developed by the end of Neoarchean. The geodynamic processes in Meso-Neoarchean were likely diverse, especially episodic hot upwelling mantle (plume) -lithosphere interaction could be a favored geodynamic regime responsible for formation of Archean felsic continental crust in the Jiaobei Terrane, NCC.

How to cite: Liu, J.: Meso-Neoarchean coupled crust-mantle differentiation followed by gravity-driven lithospheric delamination and subduction initiation in the North China Craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4864, https://doi.org/10.5194/egusphere-egu24-4864, 2024.

A low-velocity layer atop the mantle transition zone has been extensively observed worldwide, which may play an important role in mantle dynamics and Earth habitability. In subduction zones, this layer is widely explained as partial melting triggered by slab subduction on a regional or global scale. However, direct observational evidence is still absent, and the response of the layer to slab subduction is not well known. Here, we image the seismic velocity around the mantle transition zone by matching synthetic and observed triplicated seismic P and sP waveforms in the Indian–Eurasian continental subduction zone. Our observations reveal a laterally varied low-velocity layer atop the mantle transition zone beneath the Hindu Kush, where a subducted slab extends to the mantle transition zone. It is characterized by thickness of 56-94 km and P-wave velocity drop of -2.8~-4.7%. The geometric morphology of the low-velocity layer indicates that it is a partially molten layer induced by the subducted slab on a regional scale. Interestingly, our observations also support that the layer has a low viscosity. The decreased viscosity possibly facilitates slab motion in the deep domain; however, the buoyant continental crust in the shallow domain likely resists downwards movement of the slab. This differential movement is more likely to cause slab stretching, tearing and break-off in the middle region, which may contribute to explaining rare recurring large intermediate-depth earthquakes in an intracontinental setting.

How to cite: Li, G.: Seismic evidence of upper mantle melt caused by a subducted slab in the Indian-Eurasian continental subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7577, https://doi.org/10.5194/egusphere-egu24-7577, 2024.

Based on the analysis of the tectonophysical characteristics of the actual seismofocal zone (SFZ) in the lithosphere of the Kuril-Kamchatka region and adjacent Oceanic areas,  we estimated the boundary conditions necessary for constructing the quantitative models of heat and mass transfer dynamics in compacted heterophase media under active volcanoes located over the mantle and crustal magmatic   sources of the ocean–continent transition regions of the northwestern sector of the Pacific Ocean.

The methodology of obtaining the information  used for developing of the mathematical models of magmatogenic processes includes: 1) the study of individual porphyry deposits associated with active fluid volcanogenic systems; 2) the study of morphological structures using cosmic satellite images (Sharapov et al., 1980); 3) the study of mantle and crust xenoliths of volcanics (Kutyev, Sharapov, 1979; Sharapov et al., 2009, 2017, 2020); 4) parametric tectono-physical analysis of the modern SFZ of the studied region (Sharapov et al., 1984, 1992); 5) experimental modeling of the  processes of deformation   Earth's crust and lithospheric mantle rocks of modern SFZ (Sharapov et al., 1984, 1992); 6) construction of mathematical models of the petrogenesis under volcanoes (Sharapov et al., 2007, 2020)

According to data on the structure of the Earth's crust under the Avacha volcano; (Koulakov et al., 2014), permeable zones are linear fractures 2-4 km wide, which are conductors of melts and magmatogenic fluids coming from magmatic systems (Koloskov et al., 2014).

An analysis of the time characteristics of formation porphyric deposits in the active margins of the Pacific Ocean (Sharapov et al., 2013) showed that more than 70% of the described deposits are formed during the evolution of fluid mantle-crustal ore-magmatic systems. This study analyzes the data on the structure of the modern SFZ of Kamchatka and the Kuril Island arc, used in constructing a model of heat and mass transfer under volcanoes.

Based on the analysis of the tectonophysical characteristics of the actual seismofocal zone (SFZ) in the lithosphere of the Kuril-Kamchatka region and adjacent Oceanic areas,  we estimated the boundary conditions necessary for constructing the quantitative models of heat and mass transfer dynamics in compacted heterophase media under active volcanoes located over the mantle and crustal magmatic   sources of the ocean–continent transition regions of the northwestern sector of the Pacific Ocean.

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An analysis of the time characteristics of formation porphyric deposits in the active margins of the Pacific Ocean (Sharapov et al., 2013) showed that more than 70% of the described deposits are formed during the evolution of fluid mantle-crustal ore-magmatic systems. This study analyzes the data on the structure of the modern SFZ of Kamchatka and the Kuril Island arc, used in constructing a model of heat and mass transfer under volcanoes.

RNF grant  24-27-00411

How to cite: Sharapov, V., Perepechko, Y., Mikheeva, A., Vasilevsky, A., Sorokin, K., Ashchepkov, I., and Kuznetsov, G.: Analyze of the structural conditions of heat and mass transfer under volcanoes of the northwestern sector of the Pacific ocean- Eurasian continent transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4048, https://doi.org/10.5194/egusphere-egu24-4048, 2024.

The problem of the introduction of heterophase magmatic melts into the conducting channels of the lithospheric mantle under the cratons of the Siberian platform has been studied numerically. The analysis of the features of the introduction of melts was carried out on the basis of a hydrodynamic model of the evolution of magmatic and fluid-magmatic systems. The mathematical model describes the two-speed dynamics of the redistribution of hot heterophase melts and magmatogenic fluids in the flow during their movement from the generation zones to the platform cover, as well as the processes of heat and mass transfer between melts and rocks in permeable zones of the lithosphere. The nature of the flow of mixtures of liquid fractions of aluminosilicate, sulfide, native and oxide liquids, in which a sub-liquid solid phase appears during movement and decompression boiling occurs, the features of heat and mass transfer processes determine the type of magmatic and magmatogenic deposits of the trap formation of the Siberian platform. The flow of magmatic melts in a wide temperature range of 300-1200 °C, the viscosity of the melt phases of 101-106 N, as well as the rate of penetration and the degree of stratification of the heterophase magmatic flow were studied.

The figure shows an example of the randomization of an intrusive flow. (a) (b) An example of the development of heterogeneity in the distribution of the concentration of particles of the dispersed phase (a, m-3) and temperature (b, °C) in an initially stratified magmatic flow embedded in the host rocks. The temperature of the introduced flow is 500 °C, in the channel at the initial moment standard thermodynamic conditions; the dynamic viscosity of the melt is 102 P. The work was carried out with the financial support of the Russian Science Foundation, grant No. 24-27-00411.

How to cite: Perepechko, Y., Sorokin, K., and Imomnazarov, S.: Features of the introduction of magmatic melts in permeable zones of the platform cover, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14538, https://doi.org/10.5194/egusphere-egu24-14538, 2024.

The influence of the hot spot for the AVB was assumed by (Kuzmin and Yarmolyuk, 2011). It may be the same hot spot that cause the creation of the kimberlites at 420 Ma at the north of Siberian craton (Sun et al,, 2014; 2018) than in the central part of Yakutian kimberlite province 350- 370 Ma. and transferred to the Prisayanie forming kimberlite fields covered by Carboni ferrous Permian sedimentary sequences in the basins of Tumanshet, Biryusa and Chuna rivers. Than it produced the Ingashi kimberlites - lamproites 310 -300 Ma (Kostrovitsly et al., 2022).