Carbonatite melts, while representing a small fraction of all magmas on Earths, are important features of the deep carbon cycle [1]. These melts are very reactive and quickly evolve during their ascent from a CO2-rich (CO2 higher 40 %) and SiO2 poor (SiO2 around 0 % wt) to compositions including more SiO2 and relatively less CO2 [2,3]. The physical properties of what is known as transitional melts (high CO2 contents and SiO2 content below 15% wt) at high pressure are not well constrained, although they are important for understanding the dynamics of carbonatite melt migration and chemical evolution. In this study we determined one high magnesium carbonatite with a ratio Ca/(Mg+Ca) ≈ 0.2 and one dolomite carbonatite with a ratio Ca/(Mg+Ca) ≈ 0.5. Both compositions have a 12 % SiO2 content and 5 % wt H2O content. We applied the in situ X-ray absorption method in combination with XCT-tomography in a Paris -Edinburgh press at the Psiché beamline of Soleil synchrotron to determine the density of melts [4]. We measured for each composition the melt density between 2 -4 GPa and 1200 K -1900 K and complemented the in situ data with sink/float experiments at 4 GPa and temperature of 1700 K, using B4C and forsterite markers. Both types of experiments showed that dolomite carbonatite melts (high Ca content) with 12 % SiO2 have densities in the range of 2.9 – 3.05 g.cm-3, closer to that of a forsterite than carbonatites with 0 % SiO2 (indicating that even small amounts of SiO2 tend to increase significantly the density compared to pure carbonatite melts [5]. The implications of this results for the mobility of transitional melts in the upper mantle will be discussed.
[1] Jones et al. (2013) Rev. Min. Geochem. 75, 289.
[2] Hammouda & Keshav (2015) Chem. Geol. 418, 171.
[3] Moussallam, et al. (2015) Chem. Geol. 418, 198.
[4] Ritter et al. (2020) EPSL 533, 116043.
[5] Massuyeau et al. (2023) Chem. Geol. 622, 121275.
How to cite: Clesi, V., Perillat, J.-P., Henry, L., Wood, M., Cardon, H., Klemme, S., Rohrbach, A., and Sanchez-Valle, C.: Density of high SiO2 carbonatite liquids in the upper mantle., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18840, https://doi.org/10.5194/egusphere-egu25-18840, 2025.
Abstract
This study presents an experimental simulation of interactions between two distinct lithologies, representing the contact zone between the asthenosphere and subcontinental lithosphere. These compositions were layered in the capsule (sandwich runs) and subjected to pressures and temperatures representative of two subcontinental mantle of 75 and 130 km, corresponding to Phanerozoic lithosphere thicknesses. The temperatures range from 900°C to 1450°C to simulate different metasomatic reactions and fusion processes in normal geothermal environments and anomalous conditions of high potential temperatures. The experiments were performed using a belt-type high-pressure-high-temperature apparatus, using toroidal pressure plates. Compositions were prepared from pure oxides, carbonates, and hydroxides.
The asthenospheric representative layer is a mixture of fertile lherzolite (MPY) enriched with 30% eclogite (GA1) and 0.75 wt.% CO₂. The lithospheric representative layer consists of NHD, a depleted lherzolite metasomatized with 0.8 wt.% H₂O and 0.17 wt.% K₂O. These compositions have been used in previous experimental studies, enabling direct comparison of our results with those from simpler compositional systems.
The results confirm that small amounts of C-O-H volatiles significantly lower the melting point of peridotite. Melting begins at 900°C at 2.5 GPa and at 1050°C at 4.5 GPa. Amphibole stability is observed up to 4.5 GPa, demonstrating the lithosphere's substantial capacity to retain water when interacting with enriched asthenospheric compositions, likely influenced by prior subduction events. Carbon remains dissolved in carbonate minerals at 4.5 GPa up to 1050°C. As the temperature increases, carbon transitions from being dissolved in the melt to the vapor phase. Liquid compositions are basanitic at low melt fractions and evolve to trachyandesitic above 1200°C.
This research focuses on metasomatic reactions involving fluids and melts generated under adiabatic decompression. Insights contribute to understanding magmatic processes at rift systems in supercontinent cycles, where ancient lithospheric plates accumulate volatiles. Additionally, this study advances the understanding of mantle geodynamics by examining water and carbon storage in mineral phases and the dehydration and decarbonation reactions observed experimentally.
Keywords: experimental petrology, mantle metasomatism, volatile geodynamics, high-pressure melts.
How to cite: Dornelles Kern Tolotti, C. and Vieira Conceição, R.: Experimental investigation of C-O-H volatile effects at the subcontinental lithosphere-asthenosphere boundary, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20349, https://doi.org/10.5194/egusphere-egu25-20349, 2025.
Much debate exists concerning mechanisms of crustal material transfer from subducting slab to overlying mantle. Formation of mélange rocks by physical mixing of slab components within subduction plate interface is predicted to transfer their compositional signal to source of arc magmas by ascending as diapirs from slab-top. Despite being supported conceptually and through modeling, existence of these diapirs in global subduction architecture remains inconclusive. plate interface. Here we present a comprehensive study on eclogites with distinct pressure-temperature-protolith histories from a deeply buried mélange “package” in the Atbashi low-temperature (LT)- high-pressure (HP) metamorphic complex, Kyrgyzstan section of the South Tianshan Metamorphic Complex (STMC), southern Altaids. Recent studies in the Chinese section of the STMC disclose massive sediment accretion at ~80 km depth along the subduction interface, suggesting continuous refrigeration, by incoming cold material from the slab, and juxtaposition to the “cold nose” of mantle wedge. In addition, transient thermal excursion was revealed, in region, from strikingly concordant chemical zonation of garnet in coesite-bearing oceanic eclogites, disclosing the potential translation of ultra-high-pressure rocks (UHP) refrigerated slices near to a relatively hotter mantle wedge. In this study, field mapping, bulk-rock geochemistry, metamorphic petrology, Zr-in-rutile & Ti-in-quartz thermobarometers, thermodynamic modeling, rutile & zircon trace elements, and U-Pb chronology analyses have been conducted to provide the first tangible eclogitic rock evidence recording mélange diapir melting signal (MDP) and experiencing substantial thermal excursion in a well-preserved refrigerated subduction plate interface, as confirmed by the pervasive presence of lowtemperature eclogitic rocks. Additional multi-disciplinary data, especially those Late Carboniferous ones, are also compiled from regional various lithologies to fingerprint the temporal-spatial variations of mantle signal and crustal feedback during which the eclogitic mélange rocks contemporaneously formed and their fate during substantial thermal excursion. Available data provide insights into a model of mélange diapir melting in refrigerated subduction plate interface as substantiated in the STMC. Implications for such process with a momentous contribution in transferring crustal volatile from slab surface to arc lava, regulating terrestrial geochemical cycle, are thus discussed.
How to cite: Sang, M.: Implications for mélange diapir melting from HT eclogite in refrigerated subduction plate interface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17317, https://doi.org/10.5194/egusphere-egu25-17317, 2025.
Diffusion-induced nickel isotope fractionation in pyroxenitic xenoliths
Xiao-Yang Hu, Shui-Jiong Wang
State Key Laboratory of Geological Processes and Mineral Resources, China
University of Geosciences (Beijing), Beijing 100083, China.
The bulk silicate earth has a homogenous nickel (Ni) isotopic value of +0.11±0.06‰[1][2]. However, sizable Ni isotope fractionation could occur during mantle metasomatism and melt-rock interaction[1][2][3][4][5]. Here, we analyzed the Ni isotopic composition of a pyroxenitic xenolith (~10cm in length) within Cenozoic intraplate basalts from the Hannuoba region, North China Craton. The host basalts have homogenous δ60Ni value of -0.15±0.09‰, whereas the pyroxenitic xenolith has highly variable δ60Ni value ranging from -0.05‰ to +0.95‰. In detail, the δ60Ni of the pyroxenite exhibit extremely high value at one side of the basalt-pyroxenite boundary, and gradually transitioned to mantle-like δ60Ni towards the other side of the basalt-pyroxenite boundary, leading to an stairs-like pattern instead of a U-pattern. Therefore, interaction of the pyroxenitic xenolith with the host basaltic magma after entrainment cannot account for the large Ni isotopic variation. It is likely that the ancient mantle metasomatism, during which, extensive elemental and isotopic exchange between the metasomatic agent and lithospheric mantle, has produced the diffusion-induced Ni isotope fractionation, and later ascending of the Cenozoic intraplate magmas has captured this metasomatized mantle materials, and erupted to the surface.
References:
[1] Wang et al. (2021), Nat Comms, 12, 294; [2] Klaver et al. (2020), GCA, 268, 405-421; [3] Saunders et al. (2020), GCA, 268, 405-421; [4] Gall et al. (2017), GCA, 199, 196-209; [5] Sheng et al. (2022), JGR-Solid Earth, 127, e2022JB02455.
How to cite: Hu, X. and Wang, S.: Diffusion-induced nickel isotope fractionation in pyroxenitic xenoliths, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3470, https://doi.org/10.5194/egusphere-egu25-3470, 2025.
Decades of studies have shown that the petrogenesis of kimberlite-borne cratonic eclogite and pyroxenite xenoliths reflects the endemics of their crustal protoliths and local lithosphere evolution. Detailed investigations of the origin and metasomatic history of individual eclogite xenolith suites are thus required to understand how cratonic eclogite reservoirs - and their diamond inventory - evolve in the regional tectonomagmatic context. Here, we investigate a little-studied eclogite and pyroxenite xenolith suite from the Balmoral kimberlite in the Kimberley area of the Kaapvaal craton, which, like eclogite suites in neighbouring kimberlites, likely originated as subducted Archaean oceanic crust. Detailed petrographic observations and mineral major- and trace-element analyses, combined with published data for eclogite xenoliths and eclogitic inclusions in diamond, show that this sample suite records at least two distinct episodes of metasomatic overprint: (1) Metasomatism by a kimberlite-like melt caused a decrease in clinopyroxene jadeite component and garnet grossular component and imparted high MgO and Cr2O3 contents, recorded dominantly by pyroxenite xenoliths. Comparison to Kaapvaal kimberlites and lamproites confirms that the geochemical trends cannot be reconciled with bulk kimberlite-eclogite mixing but require precipitation of metasomatic clinopyroxene from the melt instead. This metasomatic style is recognised world-wide, and at Balmoral is notably restricted to the shallow lithosphere (110-150 km). (2) A distinct metasomatic event generated eclogites with extreme Y-HREE enrichment, at Balmoral restricted to the deep lithosphere (150-200 km). We propose that this enrichment style reflects phlogopite formation at the expense of garnet, with the liberation of these garnet-compatible elements to the metasomatic melt. This signature is identified in eclogite xenoliths both from early Cretaceous lamproite (Bellsbank) and late Cretaceous kimberlite (Balmoral, Kimberley) localities, tentatively ascribed to interaction with melts forming the Karoo large igneous province. Balmoral corundum-bearing eclogites derive from depths overlapping eclogites showing a Karoo-type overprint, which significantly diluted the Al2O3 content in the bulk rock and increased silica activity as gauged by the decrease in Al[IV] in clinopyroxene, thereby destabilising corundum.
Craton-wide, preserved corundum-bearing eclogites record diamond-stable ƒO2 and pressure conditions, yet show little compositional overlap with inclusions in eclogitic diamond. This may reflect the low propensity of COH fluids to reach carbon saturation in this lithology. The preserved corundum-bearing eclogites have reconstructed bulk major-element compositions, which, combined with small to absent Eu anomalies, suggest protoliths representing deep oceanic crustal (>0.5 GPa) cumulates of two pyroxenes plus only minor plagioclase that contained a significant melt component. The identification of such deep hybridised crustal rocks may reflect higher mantle potential temperatures and the formation of thicker oceanic crust in the Archaean.
How to cite: Pattnaik, J., Aulbach, S., Viljoen, F., Ueckermann, H., and Mxinwa, T.: The diamond-poor nature of corundum-bearing eclogite and Karoo-type overprint of deep eclogite sources beneath the Kimberley region (Kaapvaal craton), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4945, https://doi.org/10.5194/egusphere-egu25-4945, 2025.
The Cullinan kimberlite, also known as ‘Premier’, is located 40 km northeast of Pretoria on the Archean Kaapvaal craton, in South Africa. Dated at ca 1150 Ma, it provides a unique opportunity to explore the geochemistry and geodynamics of the deep mantle, and its interactions with the lithosphere.
This study integrates geochemistry of whole-rock and kimberlite indicator minerals with geothermobarometric evaluations to unravel the mantle components of the kimberlite magmas, and to disclose the diamond potential of the kimberlitic pulses. Major element thermobarometry on olivine, garnet, and pyroxene reveals pressure and temperature conditions of crystallization along the paleo-geotherm, as well as the correspondent mineral stability fields.
Cullinan consists of several distinct kimberlite types, four of which - Fawn, Pale Piebald, Black Transitional, and Blue - are the focus of this study. Geothermobarometric calculations demonstrates that each of these kimberlite eruptions formed under distinct chemical conditions, with three of the four types intersecting the diamond stability field. We highlight their potential to carry diamonds and we emphasize the influence of varying mantle conditions on their formation.
Preliminary geochemical classification confirms Fawn and Pale Piebald as Group I kimberlites, while Black Transitional and Blue kimberlites show evidence of contamination and metasomatic alteration, suggesting a more complex petrogenetic history. These variations in composition testify to the various mantle processes that contributed to the unicity of the Cullinan kimberlite pipe.
This study represents an advancement into the understanding of how mantle-derived melts evolve as they ascend and interact with the lithosphere. It provides critical insights into the geochemical fingerprints of the mantle and contributes to a better understanding of the dynamic processes that drive diamondiferous kimberlite formation, not only at Cullinan but also at a global scale.
How to cite: du Plessis, C., Lenhardt, N., Milani, L., Delport, J., and Phahla, T.: New Geochemical and Geodynamic Insights into the Cullinan Kimberlite, Kaapvaal Craton: Mantle Processes, Magmatic Heterogeneity, and Diamond Potential., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-596, https://doi.org/10.5194/egusphere-egu25-596, 2025.
The phreatomagmatic Carnian (Upper Triassic) kimberlitic tuff deposit of the Bulkur anticline at the right side of the Lena Mouth has the most high diamond grade in Russia (to 12 crt/t). Comparison of the thermobarometric reconstructions Ashchepkov ea 2001; Grakhanov ea., 2024) and geochemistry of pyropes (Skuzovatov et al., 2022) and presented here set of the EPMA (560), SEM (980) and LA ICP (140) analyses from tuffs at Olenek’s duct at Lena Mouth. Pyropes variations 0<Cr2O3<13% are similar to (Grakhanov et al., 2024) but TiO2 are higher to 2%.
Chromites are Ti - Al rich - varieties, compared to (Biller et al., 2017). Micas from Bulkur refer to reaction of peridotite with K- rich melt (3.5-5 % FeO and Cr2O3 to 3%) similar to range in orangeites or lamproites (Downes ea, 2006). All ilmenites ( MgO < 4%) are not deep-seated. The Cr- diopsides divides to the Cr-Al rich and Fe- enriched types.
The PT diagram show 8 layers and comparing to (Ashchepkov et al., 2017) and (Grakhanov et al., 2024) show straight line P (6.5-2GPa)-Fe# (0.11-0.15) for megacrystic pyropes. The eclogitic inclined P- Fe# trend is less abundant than in previous sets. And Ca -rich layer in middle Eclogite layer 4-5 GPa chromites are Ti to 6% from 6.5-3. GPa
The Geochemistry of almost all pyropes despite on variations in REE from U to S- shaped (dunitic) and HMREE low harzburgitic and rounded lherzolitic varieties almost all show high U-Th-Nb-Ta- levels. There are extreme Zr-Hf types those with elevated Zr-Hf. Even Cr- highest pyropes reveal high HFSE. As well as Cpxs and Amphs with Nb peaks and Chrs – Ta peak. All carbonates in tuffs are magmatic showing high REE gently increasing Yb to La ~ 5000*C1. The mantle column beneath Bulkur was reacted with the HFSE -rich K-rich aillikite melt. The studied phase is late comparing to studied before. Grant RNF 24-27-00411.
Ashchepkov, I. V., Vladykin, N. V., Ivanov, A., Babushkina, S., Vavilov, M., & Medvedev, N. 2021, Ma Problems of mantle structure and compositions of various terranes of Siberian Craton. In Alkaline Rocks, Kimberlites and Carbonatites: Geochemistry and Genesis. pp. 15-48. Cham: Springer International Publishing.
Skuzovatov, S., Shatsky, V. S., Ragozin, A. L., & Smelov, A. P. 2022. The evolution of refertilized lithospheric mantle beneath the northeastern Siberian craton: Links between mantle metasomatism, thermal state and diamond potential. Geoscience Frontiers, 13(6), 101455.
Grakhanov, S. A., Goloburdina, M. N., Ivanov, A. S., & Ashchepkov, I. V. (2024). Mineralogical and petrographic characteristics of diamondiferous formations of the Bulkur anticline, Republic of Sakha (Yakutia). Regional Geology and Metallogeny, (98), 41-63.
How to cite: Ashchepkov, I., Smelov, A., Grakhanov, S., Ivanov, A., and , : Bulkur phreato-magmatic diamond deposits – new incites for origin from the geochemistry and thermobarometry. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2176, 2025.
The 3000 km SSW-NNE mantle transect through all Congo craton (including Angola and Congo DR) was constructed based on EPMA analyses of diamond satellite minerals (DSM) from kimberlites (and placers) using monomineral thermobarometry (Ashchepkov et al., 2017) and Surpher 8 software. It crosses Lucapa corridor from Kunene to Lushinga fields and goes from Mbuji-Mai and to Banalia field in Congo DR. The NWW –SEE transect from Bas Congo to Kundelungu was built also.
The whole SW-NE profile consists of at least of 6 sections Angola part and 3 more in Congo DR part correspondently to the grouping of the kimberlites fields at the ancient mantle sub terranes. There are also heated regions with the higher concentrations of pipes correspondent to the boundaries of the sub terranes where the mantle columns are more heated and homogenized.
Mantle sections show rather contrast layering. It is more evident and thin in P-FO2 diagram and total Fe# and less for ToC and garnets CaO and Fe#.
The section in Angola include several regions with the more dense kimberlite population including Kunene, Cubango, Lubango and long array from Longo to Kamatue including Catoca cluster. The last highly diamondiferous part of mantle differ from other parts by the essential heating of the lower part of section relatively high amount of pyroxenitic and eclogitic material which probably define the high diamond grade. Several mantle clusters show heating and increase in Fe# accompanied by the low oxygen fugacity which corresponds to the high diamond grade In Angola: Cuilo – Liuele- Catoca and Camafuca Kamachia fields and in Congo DR – Mbuji- Mai and Wamba fields.
The relative homogenization beneath Catoca and close regions means more permeable mantle with concentration of proto-kimberlite magma chambers not only near the base of the lithospheric mantle, and also in intermediate and middle pyroxenite levels. The mineralogy suggests presence there and low-oxidized eclogites, dunites, and Mg-rich ilmenite-chromite-bearing metasomatites. Probably on such conditions many diamonds were growing during protokimberlite process in the large magmatic chambers near the lithosphere base where large CLIPPIR type grains as megacrysts were growing.
The uppermost Early Archaean relatively thin plate mantle layers are inclined toward the Catoca- Kamachia cluster in NNE part of Congo where the concentration of eclogites are higher probably due subduction accretion. RNF Grant 24-27-00411.
- Ashchepkov I.V., Zinchenko V.N., Ivanov A.S. Mantle Transects in Africa According to Data of Mantle Xenocrysts and Diamond Inclusions. In: Acta Geologica Sinica‐English Edition. Vol. 95(S1), pp.15-17 (2021).
- Zinchenko V., Ashchepkov I., Ivanov, A. Modelling of the mantle structure beneath the NE part of the Lucapa kimberlite corridor. Angola. In: Journal of science. Lyon, Vol.19. pp. 7-14. (2021).
- Ashchepkov I.V.; Ntaflos T., Logvinova, A.M., Spetsius, Z.V., Downes, H., Vladykin, N.V. Monomineral universal clinopyroxene and garnet barometers for peridotitic, eclogitic and basaltic systems. Geoscience Frontiers. Vol.8, pp.775-795. (2017).
- Ashchepkov I.V., Rotman A.Y., Somov S.V.et al. Composition and thermal structure of the lithospheric mantle beneath kimberlite pipes from the Catoca cluster, Angola. In: Tectonophysics. Vol. 530, pp.128-151 (2012).
RNF grant 24-27-00411.
How to cite: Zinchenko, V., Ashchepkov, I., Ivanov, A., Manuel, B. P., and Felix, J. T.: The 3000 km mantle transect through Angola and Congo based on diamond satellite minerals from kimberlites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4716, https://doi.org/10.5194/egusphere-egu25-4716, 2025.
Triangular diagrams of pyrope compositions for minor elements – Mn, Na, Ti in wt% are proposed to assess the diamond grade of kimberlite pipes.
. Basing on group cluster analysis, diagrams are constructed for pyropes from high-diamondiferous (>1 ct/t) (Fig.1), poor and non-diamondiferous kimberlites (<0.1 ct/t) (Fig.2) of Yakutia and Angola. Oval areas correspond to peridotite, eclogitic, and websterite mantle paragenesis (Sobolev, 1971), the diameter of the analytical point is proportional to the CaO content. In highly diamondiferous kimberlites (Fig. 1), pyropes of peridotite dominating and eclogitic and websterite associations are equally present. Trends in their compositions overlap in the ratios of Na2O, MnO and TiO2 in all CG
Pyropes of diamond-poorly kimberlites (Fig. 2) do not show such overlap, and for each of their CG they are isolated or have a predominance of one paragenesis over another.
Discussion. The presence of pyrope CGs from different deep sources indicates the hybridization of the proto-kimberlite melt, which assimilated the rocks of the peridotite, eclogite, and websterite "layers" of the mantle. This explains the high diamond content of kimberlites, which assimilated diamonds from these three deep sources. In poor diamondiferous kimberlites, pyropes of various paragenesis are extremely unevenly represented, which is due to the weak interaction of the melt with the "layers" of diamondiferous eclogites and websterites. The catalytic role of Ti, Na, and Mn in the process of diamond formation was pointed out by V.A. Milashev (Milashev, 1994) and J. Gurney (Gurney et al., 1994). Pyropes of highly diamondiferous kimberlites are characterized by a short TiO2 trend and a fairly long Na2O trend (Fig. 1). Pyropes of poorly diamondiferous kimberlites, on the contrary, are distinguished by a long or unexpressed TiO2 trend and a limited Na2O (Fig. 2)
Conclusions. The revealed regularities in the distribution of impurity elements in pyropes from kimberlites of different degrees of diamond content are confirmed by diagrams with an MgO-MnO "diamond window", where most of the pyrope grains of highly diamondiferous pipes fall (Figs. 1 and 2). They can be used to assess the diamondiferous potential of kimberlites based on mineralogical and geochemical criteria.
- Dawson J.B., Stephens W.E. Statistical classification of garnets from kimberlites and xenoliths. J. Geol. 1975. Vol. 83. № 5. P. 589-607
- Grifin W.L., Ryan C.G. Trace elements in indicator minerals: Area selection and target evaluation in diamond exploration. J. Geochem. Explor. , Vol. 53, P. 311-357.
- Ivanov A. S. 2015. A New Criterion of Kimberlite Diamond Content. Proceedings of the XII All-Russian (with international participation) Fersman session. KSC RAS, Apatity, pp. 268-270,
- Milashev V.A. 1994. Environment and processes of formation of natural diamonds. "Nedra", St. Petersburg, 142 p.
- Sobolev N.V. 1994. On the mineralogical criteria of diamond content of kimberlites. 1971. №3. – P. 70-80 J. J. Gurney, R. O. Moore. Geochemical correlation between kimberlite minerals and Kalahari Craton diamonds, Journal. Russian Geology and Geophysics, pp. 12 – 24,
How to cite: Ivanov, A., Zinchenko, V., Ashchepkov, I., and Kostrovitsky, S.: Ca, Mn, Na admixtures in pyropes as indicator of the diamond grade in kimberlites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18578, https://doi.org/10.5194/egusphere-egu25-18578, 2025.
Ilmenite is a diamond associate mineral from kimberlites and present in other ultramafic and basic alkaline rocks. In kimberlites ilmenite is common in the form of monomineral nodules-megacrysts, as well as phenocrysts in a fine-grained groundmass. The amount ilmenite-containing rocks from the total mantle xenoliths make up 4-7%, and it can be connected with proto-kimberlite melts. Ilmenite also occurs in a whole group of mantle rocks (called ilmenite hyperbasites), is presented as individual euhedral crystals, rounded grains, is also observed as inclusions in pyroxene, garnet and sometimes forms sideronite structures (intergrowths with silicates) and veinlets in a fine-grained olivine matrix.
In this work, mantle xenoliths were studied from the Mir (Mirny field) and Obnazhennaya (Kuoika field) kimberlite pipes of the Yakutian kimberlite province. These pipes are located in different parts of the Siberian craton and have different ages. The chemical composition of the ilmenite lamellaes and rounded inclusions from two pipes is discussed. A wide range of values is observed for lamellae from both pipes - from 39.7 to 57.6 wt.% TiO2. Rounded inclusions from the Obnazhennaya pipe are distinguished by narrow composition variations - 53-56 wt.% TiO2. At the same time, they are close to megacrystalline and xenogenic (lithospheric) ilmenites from kimberlites. Large variations in the compositions of ilmenite lamellae from pyroxene and garnet crystals suggest that these ilmenites formed as disintegration and exsolution structures during gradual cooling of the initial megacrystals. Their cooling velocity and P-T final crystallization were different to reflect the difference in ilmenite compositions. Diffusion of elements from the host mineral could also affect composition variations, since the sizes of small inclusions are up to 20-40 μm. At the same time, some of the compositions of ilmenite lamellae from Mir pipe xenoliths close into the composition field of late fine-grained ilmenites of the main mass of kimberlites. This fact may indicate deep differentiation of melts enriched in iron and titanium, possibly longer processes of lithospheric mantle evolution under the Mir kimberlite pipe than under the northeast of the craton (Obnazhennaya pipe). Rounded inclusions of ilmenite in garnet and pyroxene from peridotites of the Obnazhennaya pipe have a different genesis. Their chemical compositions on the MgO-TiO2 diagram form a compact group and are close to the region of the original, asthenospheric ilmenites. It was formed from melts, but in terms of formation time they are later than ilmenites from lamellas, which indicates a more complex history of formation and heterogeneity of the lithospheric mantle beneath the Obnazhennaya pipe.
The research was supported by Russian Science Foundation grant № 22-77-10073.
How to cite: Kalashnikova, T., Vorobey, S., and Kostrovitsky, S.: Ilmenite in peridotite and pyroxenite xenoliths from Siberian kimberlite pipes: morphology and genesis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11724, https://doi.org/10.5194/egusphere-egu25-11724, 2025.
This study presents a detailed investigation of the field relationships, geochronology, mineral-whole rock geochemistry, and isotope systematics (Sr-Nd-Pb-Os-C-O) of a newly identified carbonatite-alkaline syenite intrusive system from the Gundlupete area, located near the tectonic boundary between the Western Dharwar Craton (WDC) and the Granulite Terrain of South India. The carbonatite intrudes the syenite and is exposed along an E-W to ENE-WSW trending splay of the Moyar shear zone near the southern margin of the WDC. In-situ U-Pb dating of titanite and monazite provides crystallization ages of 2590 ± 42 Ma and 2474 ± 27 Ma for the syenite and carbonatite, respectively, indicating two distinct magmatic episodes with independent petrogenetic histories. The syenite comprises alkali feldspar (Or93.7-100), albite (Ab98-99), clinopyroxene (Di22.08–65.68 Hd20.04–44.65 Aeg13.91–44.64), biotite (Xmg: 0.54–0.58), titanite (Al: 0.03–0.06 apfu), and quartz. Geochemically, the syenite exhibits shoshonitic characteristics (K₂O/Na₂O: 0.9–2.42), enrichment in LILEs and LREEs, depletion in Mg, Ni, Cr, and HFSEs (Nb, Ta, Ti, Zr, Hf), and crust-like ratios such as high Th/NbPM (avg. 79) and low Nb/U (avg. 2.17). Initial εNd values (-1.4 to 1.0) align with the Mesoarchean Dharwar TTG suite, suggesting a derivation from evolved partial melts of TTG sources, followed by clinopyroxene-biotite dominated fractional crystallization. The carbonatite is coarse-grained and composed predominantly of calcite, apatite, magnetite, monazite, amphibole, and phlogopite. Calcite and apatite are enriched in Sr and REEs, while phlogopite is Fe-Al-rich (Fe/(Fe+Mg)>0.22), and magnetite, containing 0.39–0.81 wt.% TiO₂, follows a typical titano-magnetite evolutionary trend. Geochemically, the carbonatite shows selective enrichment in LILEs (e.g., Ba and Sr) and Th, with lower HFSE concentrations (e.g., Zr, Hf, Ti, Nb, Ta). Isotopically, the carbonatite has a narrow range of Sr (⁸⁷Sr/⁸⁶Sri: 0.70307–0.70321), Nd (εNdi: -3.7 to -2.1), and Pb (²⁰⁶Pb/²⁰⁴Pbi: 13.49–13.85, ²⁰⁷Pb/²⁰⁴Pbi: 14.70, ²⁰⁸Pb/²⁰⁴Pbi: 33.32–34.96), while C-O isotopes range from -10.2‰ to -9.4‰ (δ¹³C) and 7.7‰ to 10.3‰ (δ¹⁸O). These characteristics suggest a primary carbonate melt derived from chondritic to slightly enriched mantle sources, with minor crustal assimilation and extensive crystal fractionation. The syenite’s geochemical signatures, εNdi values, and Nd model ages (2.8–3.0 Ga) support a derivation from Mesoarchean TTG sources. The carbonatite’s low δ¹³C values, higher time-integrated Rb/Sr ratios, and lower Sm/Nd and U/Pb ratios reflect the influence of recycled subducted components. Field, geochronological, geochemical, and isotopic evidence links the ca. 2.59–2.47 Ga magmatic events to the Neoarchean amalgamation of the Dharwar Craton and Granulite Terrain, driven by the northward subduction of the Dharwar Ocean lithosphere beneath the WDC. We propose a tectonic model where subduction-induced magma underplating triggered syenite emplacement at 2.59 Ga, coinciding with similar arc-related magmatism in the region. The carbonatite represents a later magmatic pulse in a post-collisional setting at 2.47 Ga, utilizing pre-existing conduits during the terminal accretion phase of the Dharwar Craton and Granulite Terrain at the Archean-Proterozoic boundary.
How to cite: Pandey, R., Debnath, S., Belyatsky, B., Chew, D., Rao, N. V. C., and Singh, M. K.: Decoding Archean-Paleoproterozoic carbonatite and syenite magmatism at the Dharwar Craton-Granulite Terrain boundary, southern India: Implication for petrogenesis, source characteristics and timing of terrane subduction-accretion , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-594, https://doi.org/10.5194/egusphere-egu25-594, 2025.
The polychronous Mundwara alkaline complex displays a range in 40Ar-39Ar ages between 68.5-110 Ma. It has been previously correlated to three distinct tectonomagmatic events: (i) the Deccan Large igneous Province associated with the Reunion plume, (ii) Indo-Madagascar breakup triggered by the Marion plume, and (iii) Rajmahal-Sylhet Traps linked to the Kerguelen plume. However, the age of carbonatites from the Mundwara complex was previously unknown and based on apatite U-Pb dating is now constrained at 100 ± 20 Ma. To further our understanding of carbonatite magmatism at Mundwara, this age is supplemented with petrographic observations, bulk-carbonate carbon and oxygen isotope analyses and in-situ determinations of trace element contents and Sr-Pb isotopic ratios for calcite and apatite. The Mundwara carbonatites consist of calcite cumulates and accessory apatite, pyrochlore, albite, orthoclase, Fe-oxides, and biotite. A range of REE-bearing phases is also present, including bastnaesite, parisite, and monazite. Cumulitic and seriate texture and high Sr contents (>1 wt%) attest to the primary igneous nature of the calcites. The apatites are magmatic, as demonstrated by their euhedral shape, low Sr content, and chondrite-normalized REE patterns, distinguishing them from typical hydrothermal apatite elsewhere. The apatite grains yield a weighted mean 87Sr/86Sr of 0.70447 ± 0.00003 (n = 24), indistinguishable from those of the carbonates analyzed in the same samples (87Sr/86Sr = 0.70446 ± 0.00001; n = 54). Lead (206Pb/207Pb = 0.820- 0.289; 206Pb/204Pb = 18.53-19.20) and Sr isotopic compositions of the calcites are broadly intermediate between enriched mantle (EM) and HIMU (high 238U/204Pb) compositions and signal a source that experienced geochemical enrichment by either metasomatism or addition of subducted material. The bulk- carbonate δ13C and δ18O data of the Mundwara carbonatites have a narrow range from -6.2‰ to -6.8‰ and from +6.3‰ to +7.3‰ respectively, showing typical mantle values and excludes significant contamination or post-magmatic alteration as well as contribution by subducted carbon. The mid-Cretaceous U-Pb age of the magmatic apatite overlaps with both the pre-breakup of the Indo-Madagascar event at ~88 Ma and the Kerguelen plume-induced magmatism (117 Ma) in the north-eastern parts of the Indian shield. Although this magmatic event cannot be assigned to a specific tectonic episode, this new temporal constraint and previously reported ages for other alkaline rocks from north-western India ascertains a pre-Deccan alkaline magmatic flare-up in this region.
How to cite: Bhunia, S., Rao, N. V. C., Giuliani, A., Tavazzani, L., Talukdar, D., Pandey, R., Kumar, A., Ansari, S., and Lehmann, B.: Apatite-calcite U-Pb geochronology, trace element and C-O-Sr-Pb isotope geochemistry from the polychronous Mundwara alkaline complex: New evidence of mid-Cretaceous Pre-Deccan carbonatite magmatism in northwestern India., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-216, https://doi.org/10.5194/egusphere-egu25-216, 2025.
We present some data on Cenozoic (KZ) intraplate rocks in Baluchestan and Sistan, East Iran received by a group led by known regional trio: A. Hushmanzadeh, M.A.A. Nogol Sadate, and E. Romanko.
Some important features on intraplate and subduction-related rocks are as follows:
Rocks are mainly K-Na, middle K2O subalkaline (mainly) and alkaline ones, not very High-Ti, 87Sr/86Sr (ISr) = 0.7039+- 2 (trachyAndesite) and 0.7049+- 3 (trachyBasalt) alongside with 0.7049 of 'vulcanite' (Camp & Griffis, 1982), LREE-enrichment with a high LREE/HREE (La - more than 32 ppm), and a characteristical Eu/Eu* more than 1.1; up to high = 1/3 wt% CaO and up to a high=0.45% of Sr in basic trachyandesites (while Quaternary carbonatites are ca. 200 km to the east, Hanneshin, Afghanistan), complex correlation of some characteristical elements; then-High-Ti (rhutile, Ti-hornblende) and High-Ca phases (clinocoizite, also, Ca-rich ceolite - vayrakite is proposed), replacement of primary minerals due to a fairly strong rock-fluid interaction. North-East (submeridianal) tectonic-magmatic +- metallogenic (economic regional porphyry Cu-Au+-Mo; Pb, Zn, Au-Ag and fairly poor Ag, PGE, As, Hg, Bi etc. - e.x., Anarak known deposits in Central Iran associated with Pg (mainly Pg2) subalkaline volcanites (E. Romanko et al., 1984) ) ZONING related to known subduction of Arabian plate, e.x.: subduction-related (1) - intraplate (2) rocks:
1: Eocene shoshonites etc. - Paleocene-Oligocene calc-alkaline intrusives - Miocene-Recent calc-alkaline volcanic (-plutonic) rocks
2: Paleogene? (Lut block) - Neogene intraplate subalkaline - alkaline rocks - Quaternary Afghanistan carbonatites etc. Alpine compression in subduction depth up to 200 km in Central Iran, at least, partly compensated, as proposed, by contemporaneous / younger Pg?-N-Q intraplate magmatism of Iran - Afghanistan - SouthEast Pamir (Pg-N?) and maybe Saudi Arabia carbonatites etc.
This work was made due to the State program of the Geological Institute RAS.
How to cite: Romanko, A., Imamverdiyev, N., Heidari, M., Rashidi, B., Malykh, M., Vikentev, I., and Poleshchuk, A.: Intraplate Ca-rich and Ca-usual igneous rocks in Baluchestan, Iran associated with real carbonatites of Afghanistan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14434, https://doi.org/10.5194/egusphere-egu25-14434, 2025.
Chhotanagpur Gneissic Complex (CGC) is a part of the E-W trending Central Indian Tectonic Zone (CITZ), India. The CITZ is a major intercontinental suture which separates the northern Indian and the southern Indian blocks whose subduction polarity is a contentious issue. We present petrography, mineral chemistry, bulk rock geochemistry, Lu-Hf, Re-Os and Pb-Pb isotopes of the Neoproterozic lamprophyre from Simdega. The studied lamprophyre is an unmetamorphosed and undeformed that exhibits a strong porphyritic-panidiomorphic texture imparted by the megacrysts/phenocrysts of mica and amphibole with feldspar, apatite, titanite, zircon and opaques confined to the groundmass. Our lamprophyre shows shoshonitic affinities and is classified to be of calc-alkaline variety (minette). The Mg# values (ranging from 70.7 to 78.2) indicate a primitive melt character while the trace element ratios are consistent with those of subduction-related rocks globally as well as with the calc-alkaline lamprophyres from the Eastern Dharwar Craton (southern India) that suggest no crustal contamination. Our findings demonstrate that the western part of the CGC was less affected by the M3 regional amphibolite-grade metamorphic event (ca. 920-880 Ma) compared to the eastern part. Our study also supports geodynamic models proposing northward subduction of the Southern Indian block beneath the Northern Indian block synchronous to the Rodinia assembly. Scanning Electron Microscopy (SEM) helped to identify some of the mineral phases occurring as inclusions in zircons having abnormally higher Thorium (Th) and Silver (Ag) concentrations.
How to cite: Kumar, D., Chalapathi Rao, N. V., and Belyatsky, B. V.: Neoproterozoic (942 Ma) calc-alkaline magmatism from Simdega, Chhotanagpur Gneissic Complex and their mineralisation aspects, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-519, https://doi.org/10.5194/egusphere-egu25-519, 2025.
Rifting-driven source melting and the origin of the alkaline magmatism located along the active fault segments in Southeastern Mediterranean, Türkiye
Rift-related extensive mafic magmatism was developed along the active segments of the East Anatolian zone in southeastern part of Anatolian lithosphere, since Quaternary times. These mafic and mainly basaltic rocks are widely distributed in Osmaniye - Ceyhan district and along the Karasu valley in Hatay. The mafic lavas from Toprakkale region are predominantly classified as alkaline basalts with SiO₂ and MgO contents ranging from 45.79-48.65 wt% and 7.99-8.88 wt%, respectively. Additionally, one sample is classified as basanite, with a SiO₂ content of 44.18 wt% and MgO content of 6.53 wt%.
The primitive mantle-normalized multi-element diagram exhibit enrichments in LILE relative to HFS elements, and these elemental patterns are similar to that those of OIB source but differ from OIB signature with relatively depleted LILE and HFSE contents. However, the basanite sample distinguishes itself by the enrichment in Nb, Ta, Sr, P and minor depletions in Zr, Hf contents relative to OIB source. The incompatible element ratios Nb/U (27.29-77.55), Nb/La (0.72-1.60), Zr/Ba (0.57-0.70) suggest that basaltic rocks were derived from OIB-like mantle source. The (Tb/Yb)(N) ratios of the lava products span from 1.89 to 2.68 that separates the melting from the Garnet - Spinel ((Tb/Yb)(N) >1.8; [1]) transition zone, accompanied with moderately to high (La/Yb)(N) ratios (9.92-14.37). Besides, Zn/Fe ratios of basaltic rocks range between 10.40-12.41 which separates the peridotite-derived (Zn/Fe <12; [2]) and pyroxenite-derived (Zn/Fe 13-20); [2]) melts.
Rifting process has a key role in magma generation where the stretching lithosphere leads to decompression melting, collectively, all these elemental ratios strongly suggest that basaltic rocks were derived from the melting of peridotite source domains within the region significantly affected by the active fault segments.
1.Wang et al., 2002, J.Geophys.Res.vol:107, ECV 5, 1-21
2.Le Roux, et al.,2011, EPSL, vol:307, 395-408
How to cite: Önder, D. A., Kürkcüoğlu, B., Yürür, M. T., Kahraman, B., and Külahcı, G. D. D.: Rifting-driven source melting and the origin of the alkaline magmatism located along the active fault segments in Southeastern Mediterranean, Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-612, https://doi.org/10.5194/egusphere-egu25-612, 2025.
It is suggested that in the genesis of the large volumes of the granites of Angara-Vitim Batholiths and similar huge granite massifs the important role play the plume magmas which were the major supply of the heart. But they also could directly participate in the magma generation providing volatiles and alkalis and other components. But of course the major melting components were granulites and lower crust gneisses.
We studied major elements and the geochemistry of the Pl- bearing pyroxenites captured by the Quaternary alkaline basalts from Baikal rift – using EPMA, SEM and LAM ICP methods from Vitim plateau, Tunka valley (Karierny volcano) (Ashchepkov et al., 2024) mainly compositions oof amphiboles, Pyroxenes, plagioclases and K-Fspars as well as micas and more rare garnets.
Studied amphiboles mainly reveal inclined spectra (La/Ybn ~5-10) of pyroxenes and higher for amphiboles (~ 15 ) having higher REE and elevated LILE. Single – grain The Pls have flatter REE patterns with the peaks in Ba the K- alkali feldspars have lower REE levels and higher Ba, LILE Sr peaks. Much lower REE and higher Ba, alkalis reveal micas.
Less inclined spectra of minerals from Karierny volcano 13.5 Ma indicate a less deep of origin of the parent melts.
Thermobarometry of Vitim pyroxenites gives 5-12 kbar and for amphiboles, 8-5 kbar is somewhat shallower. In Tunka valley 10-4 kbar and 7-4 in amphiboles. This corresponds to the lower thickness of the crust in Tunka and lower garnet influence.
On the whole, amphiboles give closer TRE spectra to alkaline granitoids. But all of them have a minimum Pb, which indicates fractionation processes, and granitoids (Tsygankov et al., 2014-2017), on the contrary, have a Pb peak, which indicates partial melting. In addition, in syenites, the concave part of the HREE spectrum indicates low-temperature garnet in restites.
the Vitim Plateau imply the participation of garnet in the processes of partial melting.
The genesis of the alkaline granites and syenites (Tsygankov et al., 2014) suggest the fractional and possibly disequilibrium melting of the K -FSp and micas and partly butch melting of Ampx-Pl of the granulite and gneisses possibly in different levels as well the direct infiltration of alkaline basalt are also suggested. These magmas are more typical for the regions with the thicker crust. The major factor was the plume melts impact.
For the Ca- alkaline granitoids the batch melting is more realistic model with the higher participation of the Pl and amphiboles in magma genesis. And they corresponds to the central parts of the Transbaikal with the relatively thinner crust. These means also the more higher melting of crust material under plume influence. Supported by RNF grant 23-17-00030
How to cite: Ashchepkov, I., Tsygankov, A., Burmakina, G., and Medvedev, N.: Trace elements in the black Pl bearing xenoliths in Quaternary basalts from Baikal rift. Implications to the origin of granites , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12237, https://doi.org/10.5194/egusphere-egu25-12237, 2025.
The process of magmatic melt intrusion into permeable zones of the lithosphere, as well as deformation of the permeable region of magmatic channels, is studied within the framework of two-speed thermohydrodynamics of viscous compressible media. The model has applications in the problem of evolution of magmatic systems in the lithospheric mantle and crust of cratons and the ocean-continent transition region. The mathematical model of two-speed hydrodynamics of high-temperature melts is thermodynamically consistent and takes into account such dissipative processes as phase viscosity, thermal conductivity, interphase friction, and surface effects in a heterophase medium. Taking into account the compressibility of the medium allows us to study heat and mass transfer in flows of heterophase melts with a high content of magmatic fluids. Numerical modeling of magmatic melt intrusion into vertical channels was performed for problems characterized by the following parameters: temperature of the two-phase medium 500-1200°C, melt viscosity 101-106 P, velocities of the carrier phase and inclusions were 10-3-10-1 cm/s. The injected high-temperature heterophase magmatic flow was specified as non-uniform in terms of the content of the dispersed phase. This leads to the formation of two- and three-layer flows in the gravity field.
The process of introduction of a high-temperature heterophase medium into a permeable zone located at a lower temperature is shown in Figure 1. The introduced flow is characterized by a lower content of inclusions compared to their content in the channel. The development of instability of the intruded flow is caused by the initial heterogeneity at the boundary.
Figure 1. Dynamics of the introduction of a high-temperature heterophase substance into a vertical channel in a gravity field: the distribution of temperature (left) and volume content of dispersed phase particles (right) is shown for different moments in time.
The difference in the nature of the developed flow for melts with different viscosities is shown in Figure 2.
Figure 2. Distribution of temperature (left) and volume content of dispersed phase particles (right) during the introduction of a heterophase substance with different viscosities of the carrier phase (10-1, 100, 101, 102 P)
The work was carried out with the financial support of the Russian Science Foundation, grant No. 24-27-00411.
How to cite: Imomnazarov, S., Perepechko, Y., and Sorokin, K.: Dynamics of two-phase flows in magmatic channels, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17151, https://doi.org/10.5194/egusphere-egu25-17151, 2025.
In this paper, the evolution of the upper mantle and the formation of regions of partial melting of the asthenosphere are simulated numerically within the framework of a single-velocity multilayer hydrodynamic model that takes into account the main phase transitions. The modeling results can be used to formulate problems on the introduction of magmatic melts into the lithosphere and crust in the ocean-continent transition region. The region from the marginal sea and the ocean-continent transition zone of the northern Pacific Ocean to the rift zone was numerically studied. To formulate the numerical problem, the data on the analysis of the structure of the earth's crust and upper mantle in the ocean-continent transition region of the northwestern Pacific Ocean were used, carried out by seismic tomography methods using the GIS-ENDDB geoinformation and computing system (Mikheeva, 2016). Tomographic data made it possible to determine the regional structure of magmatic systems in the lithosphere and upper mantle of the northern Pacific Ocean. Analysis of these data, together with data on gravity and magnetic anomalies in the earth's crust, allowed us to estimate the levels and areas of transformation of the earth's crust and lithospheric mantle by past magmatic processes. The fields of shear wave velocities with vertical polarization for the areas of manifestation of PTTS for different depths of the mantle lithosphere and mantle of the northern part of the Pacific Ocean are shown in Figure 1 according to data (Schaeffer, Lebedev, 2013) in the format of the shadow model GIS-ENDDB in relative units.
Figure 1. Tomographic maps of vertically polarized shear wave anomalies for areas of PTTS manifestation at depths of 50, 100, 200, 300, 400, 500 km (according to [Schaeffer, Lebedev, 2013])
The results of the simulation of the ocean-continent transition zone and the northern part of the Pacific Ocean to the North American rift zone, calculated using a multilayer model taking into account seismic tomography data (Perepechko, Sharapov, 2014), are shown in Figure 2. The red zones indicate the melting regions that form the asthenosphere. The development of an active convective flow in the initially heterogeneous upper mantle leads to the appearance of ascending flows on the right boundary of the computational domain, corresponding to the north of the West Pacific rift belt.
Figure 2. Temperature distribution (blue) and degree of partial melting of mantle rocks (red) along the section of the northern part of the Pacific Ocean (at 47° N). The time corresponds to 72 and 149 million years after the emergence of active convective flow in the upper mantle.
Grant No. 24-27-00411.
How to cite: Perepechko, Y., Mikheeva, A., and Imomnazarov, S.: Structure of the lithosphere and upper mantle in the ocean-continent transition region of the northwestern Pacific Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11899, https://doi.org/10.5194/egusphere-egu25-11899, 2025.
