GD2.2 | Geochemical and geodynamic perspectives on the origin and evolution of deep-seated mantle melts and their interaction with the lithosphere
EDI PICO
Geochemical and geodynamic perspectives on the origin and evolution of deep-seated mantle melts and their interaction with the lithosphere
Co-organized by GMPV2
Convener: Igor Ashchepkov | Co-conveners: Sonja Aulbach, Kate Kiseeva, NV Chalapathi Rao, Evgenii Sharkov
PICO
| Mon, 24 Apr, 08:30–10:15 (CEST)
 
PICO spot 2
Mon, 08:30
The origin and evolution of the continental lithosphere is closely linked to changes in mantle dynamics through time, from its formation through melt depletion to multistage reworking and reorganisation related to interaction with melts formed both beneath and within it. Understanding this history is critical to constraining terrestrial dynamics, element cycles and metallogeny. We welcome contributions dealing with: (1) Reconstructions of the structure and composition of the lithospheric mantle, and the influence of plumes and subduction zones on root construction; (2) Interactions of plume- and subduction-derived melts and fluids with the continental lithosphere, and the nature and development of metasomatic agents; (3) Source rocks, formation conditions (P-T-fO2) and evolution of mantle melts originating below or in the mantle lithosphere; (4) Deep source regions, melting processes and phase transformation in mantle plumes and their fluids; (5) Modes of melt migration and ascent, as constrained from numerical modelling and microstructures of natural mantle samples; (6) Role of mantle melts and fluids in the generation of hybrid and acid magmas.These topics can be illuminated using the geochemistry and fabric of mantle xenoliths and orogenic peridotites, mantle-derived melts and experimental simulations.

PICO: Mon, 24 Apr | PICO spot 2

Chairpersons: Sonja Aulbach, Igor Ashchepkov, Kate Kiseeva
Introduction. Mantle processes and their influence on the composition and structure of lithosphere
08:30–08:35
Global mantle processes
08:35–08:37
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PICO2.1
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EGU23-6727
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GD2.2
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Highlight
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On-site presentation
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Nadia Malaspina, Giulio Borghini, Stefano Zanchetta, and Simone Tumiati

The fate of crust-derived melts at warm subduction zones and the transport mechanism of crustal components to the supra-subduction mantle is still matter of debate. Borgo outcrop of Monte Duria Area (Adula-Cima Lunga unit, Central Alps, Italy) is an excellent case study of melt-peridotite interaction occurred under a deformation regime at high pressure, that enabled the combination of porous and focused flow of eclogite-derived melts into garnet peridotites. Migmatised eclogites are in direct contact with retrogressed garnet peridotites and experienced a common high pressure (2.8 GPa - 750 °C) and post-peak (0.8–1.0 GPa - 850 °C) static equilibration. The contact is marked by a tremolitite layer, also occurring as boudins parallel to the garnet layering in the peridotites, derived from a garnet websterite precursor after the interaction between eclogitic melts and peridotites at high pressure. LREE concentrations of retrogressed websterites along a 120 m length profile starting from the eclogite-peridotite contact to the inner part of the peridotite, show a progressive enrichment coupled with a peculiar fractionation. Numerical modelling assuming the eclogitic leucosome as the starting percolating melt reproduces the REE enrichment and LREE-HREE fractionation observed in retrogressed websterites bulks within the first 30 m by two steps of melt-peridotite reaction: a high peridotite assimilation at eclogite-peridotite boundary, followed by reactive melt percolation within the peridotite assuming variable amounts of olivine assimilation and pyroxene + amphibole/phlogopite crystallisation. The numerical simulation aims to model the effect of interaction between crust-derived melts produced by partial melting of mafic slab component with suprasubduction mantle peridotites at sub-arc depths. The comparison between the REE composition of the retrogressed garnet websterites along the profile and the result of our model suggests that reactive melt infiltration at HP is a plausible mechanism to modify the REE budged of mantle peridotites that lie on top of the subducting crustal slab, which show peculiar LREE “spoon-like” fractionations. Moreover, the melt/peridotite interaction and the percolation of slab-derived melts into the overlying mantle may strongly modify the overall REE abundance and LREE/HREE fractionation (e.g., CeN/YbN) of the residual crustal melt within the first 30 m of slab/mantle interface.

How to cite: Malaspina, N., Borghini, G., Zanchetta, S., and Tumiati, S.: Geochemical interaction between slab-derived melts and mantle at high pressure in subduction zones, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6727, https://doi.org/10.5194/egusphere-egu23-6727, 2023.

08:37–08:39
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PICO2.2
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EGU23-6901
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GD2.2
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ECS
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Highlight
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On-site presentation
Baochun Li and Gaofeng Ye*

The North China Craton (NCC) has been affected by the subduction and roll-back of the Paleo-Pacific Plate in the Mesozoic. To study the thinning of the lithosphere and the melting of the NCC, a three-dimensional (3-D) resistivity model of the lithosphere is obtained from a magnetotelluric sounding (MT) deployed in the NCC (Figure 1). In addition, the cause of the low resistivity of the upper mantle of the NCC can be solved by the Nernst-Einstein Equation and the Arrhenius Equation which is used to establish the relationship between the resistivity and temperature. Moreover, the Hashin-Shtrikman (HS) boundary conditions limit the range of electrical conductivity of mixed minerals (Figure 2). Based on the 3D resistivity structure, the temperature and melt fraction model, the lithospheric resistivity of the north of 37.5°N in the Ordos Block (OB), the southern Taihang Uplift (THU) and the Luxi Uplift (LXU) are as low as 1 Ωm which the upper mantle temperature is in the range of 1400 - 1550 °C, and the melt fraction is 1-10% in the high-temperature regions. According to the resistivity model and the thermal state, the westward subduction and roll-back of the Paleo-Pacific Plate provided conditions for upper mantle melting in the LXU and the Bohai Bay Basin (BBB). It also made the Tanlu Fault Zone (TLFZ) and THU channels for the upwelling, and the front of the Paleo-Pacific Plate stagnant slab is blowing the THU. With the remote tectonic stress of the Paleo-Pacific Plate and the Indian Plate, anticlockwise rotation of the OB induced the low resistivity of grabens and rifts around the OB (Figure 3). Moreover, upper mantle volatiles (H2O and CO2) and slight carbonatite melts significantly lower the mantle melting temperature.

* This work was supported by National Natural Science Foundation of China (Grants 41974112 and 40434010) and project SINOPROBE on sub-project SINOPROBE-01.

Reference:

Dong, S..T. Li. (2009). SinoProbe: the exploration of the deep interior beneath the Chinese continent. Acta Geologica Sinica, 83(7), 895-909.

Hirschmann, M. M. (2010). Partial melt in the oceanic low velocity zone. Physics of the Earth and Planetary Interiors, 179(1), 60-71.

Zhao, G..M. Zhai. (2013). Lithotectonic elements of Precambrian basement in the North China Craton: Review and tectonic implications. Gondwana Research, 23(4), 1207-1240.

Figure 1 Simplified s tectonic map of the North China Craton (modified from Zhao and Zhai (2013)); Map of MT profiles and sites, in which blue dots represent MT stations in this study, supported by the “SINOPROBE” project (Dong and Li, 2009). TNCO: Trans-North China Orogen 

Figure 2 Schematic diagram of dynamic changes of water and carbon dioxide during heating and melting of upper mantle minerals. NAMs means nominally anhydrous minerals; the “Calculate” in the dashed box is the calculation category of this study; the criterion for determining the interconnection of melts was proposed by Hirschmann (2010).

Figure 3 Schematic diagram of the possible formation mechanisms of the North China Craton inferred from the crustal and upper mantle 3-D resistivity model derived from this research.

How to cite: Li, B. and Ye*, G.: Three-dimensional Lithospheric Resistivity Structure and Thermal State of the North China Craton, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6901, https://doi.org/10.5194/egusphere-egu23-6901, 2023.

08:39–08:41
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PICO2.3
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EGU23-14309
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GD2.2
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Virtual presentation
Siberian Large Igneous Province: a combination of rift and platform magmatism during its formation
(withdrawn)
Nadezhda Krivolutskaya
08:41–08:43
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PICO2.4
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EGU23-822
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GD2.2
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ECS
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Highlight
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On-site presentation
New Findings on Magmatic Evolution, Source Characteristics and Geodynamic Setting of The Kula Volcanics (City of Manisa) Western Turkey
(withdrawn)
Azime Nur Özkulluk, Eren Karapolat, Mehmet Keskin, and Sıla Yurtsever
Mantle derived magmatic massifs
08:43–08:45
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PICO2.5
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EGU23-14860
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GD2.2
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ECS
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Highlight
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Virtual presentation
Mantle sources and formation processes of highly-siderophile element ore layers in magmatic, mafic-ultramafic intrusions: an alternative model
(withdrawn)
Bénard Antoine
08:45–08:47
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PICO2.6
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EGU23-10859
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GD2.2
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ECS
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Virtual presentation
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Priyanka Negi, Ivan Belousov, Leonid V Danyushevsky, Ashima Saikia, and Mansoor Ahmad

The small plutons of anorthosite and associated gabbronorite exposed near Barabar hills form a component of Chotanagpur granite gneiss complex (CGGC) in eastern India. Plagioclase (>90 vol %) make up the majority of anorthosite rock with minor mafic minerals (amphibole, mica), while orthopyroxene (>40 vol %), plagioclase (40-50 vol %) and clinopyroxene (>20 vol %) make up the associated gabbronorite. These are cumulate rocks with anorthosite and gabbronorite showing adcumulate and mesocumulate textures, respectively. Compositionally, plagioclase ranges from anorthite to labradorite (An60-96) in anorthosite and from oligoclase to bytownite (An50-70) in gabbronorite. In gabbronorite, the clinopyroxene composition ranges from diopside to augite (En36-43 Fs12-15 Wo43-47), and the orthopyroxenes are hypersthene (Wo39-40 En46-50 Fe10–21).

Anorthosite show enrichment of LILE (Rb, Ba, Sr, Th, Pb) with respect to the HFSE (Zr, Ti, Nb and display enrichment in LREE ((La/Yb) N = 2.78-15.29) with positive Eu anomaly (Eu/Eu* = 1.29-3.45) and variable MREE. A flat to depleted trend for HREE ((Sm/Yb) N = 1.02-2.95) is observed for anorthosites. Associated gabbronorites show enrichment of LREE ((La/Yb) N=1.99-4.93), depleted HREE ((Sm/Yb) N = 0.88-3.24) with negative to positive Eu anomaly (Eu/Eu* = 0.78-2.95). Also, the gabbronorite shows enrichment of LILE (Rb, Ba, Sr, Th, Pb) compared to HFSE (Zr, Ti, Nb). Clinopyroxenes of gabbronorite have low REE abundances (53.29-60.29 ppm). Clinopyroxenes are depleted in light rare earth elements (LREEs) (La/Yb) N = 0.75–0.80 and depleted in LILEs such as Ba, Sr. and also exhibit negative anomalies in Zr and Ti.

REE composition of gabbronorite clinopyroxene is constrained between TMF = 15-30% calculated using the equilibrium distribution method (EDM). This is substantiated by whole rock parental melt REE composition calculated using the concentration ratio approach (Nernst equation), the result of which is consistent with those made using EDM. In chondrite normalized plot, the estimated parental melt display (1) near-horizontal trend from Lu to Gd at rock/chondrite = ~100, (2) negative anomaly at Eu, (3) gradual rise from Sm to Ce and (4) slight dip from Ce to La.

How to cite: Negi, P., Belousov, I., Danyushevsky, L. V., Saikia, A., and Ahmad, M.: Anorthosite and associated gabbronorite plutons of Barabar hills in Chotanagpur granite gneiss complex (CGGC), eastern India: Estimation of parental melt for gabbronorite using equilibrium distribution method (EDM), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10859, https://doi.org/10.5194/egusphere-egu23-10859, 2023.

08:47–08:49
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PICO2.7
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EGU23-11507
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GD2.2
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Virtual presentation
Geochemical characteristic of the gabbro Kharanur and Kho;bun-Khairkhan ophiolite massif  (East Sayan)
(withdrawn)
Olga Kiseleva, Evgeniya Ayriants, Dmitriy Belyanin, Sergey Zhmodik, and Natalya Korobova
08:49–08:51
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PICO2.8
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EGU23-16857
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GD2.2
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On-site presentation
Sergey Zhmodik, Igor Ashchepkov, Olga Kiseleva, Dmitry Belyanin, Irina Sotnikova, Nikolai Medvedev, and Nikolai Karmanov

The Belo-Ziminsky alkaline-ultrabasic carbonatite massif contain dolomite, and calcite ankerite carbonatites essential part , syenites, melteigites and iolites cut by aillikite dikes of several generations (Ashchepkov et al., 2020; Doroshkevich et al., 2014-2021 etc). We analyzed  >4000 mineral grains by electron microscope in all types of rocks and >230 grains by  LA ICP MA  All rocks of the massif are derived from one type of mantle melt that was close to aillikite and formed at a level of >5 GPa in the mantle.

According to the nature of the PGE spectra –  and by serpentinized xenoliths in aillikites, this melt drained metasomatized enriched peorvskites and hydrogenated mantle and was initially very rich in HFSE. Above, at the level of the crust and the upper part of the mantle, the melt began to separate under liquation. In the lower and middle crust, several (3) magmatic chambers were probably formed sequentially, which separated various carbonate and silicate melts, and from dolomite to ankerite melts, judging by the slope, the number of grains in the source decreased, that is, the melts became less deep and more fractionated.

These trends are reflected both in the composition of pyroxenes from aillikites  and in the PTX diagram . All this led to significant variations in rocks and their rare-earth spectra of all rocks

 

How to cite: Zhmodik, S., Ashchepkov, I., Kiseleva, O., Belyanin, D., Sotnikova, I., Medvedev, N., and Karmanov, N.: Tracing of evolution of carbonatite and silicate melts of the Belo-Ziminsky alkaline-ultrabasic carbonatite massif by mineralogy and geochemistry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16857, https://doi.org/10.5194/egusphere-egu23-16857, 2023.

Kiimberlites and lamproites: geochemistry and petrology of xenocryst and xenoliths and petrologic reconstructions
08:51–08:53
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PICO2.9
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EGU23-13300
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GD2.2
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On-site presentation
The U-Pb and Lu-Hf isotope composition of zircon xenocrysts from the V. Grib kimberlite pipe (Arkhangelsk region, NW Russia): a key to reconstruct the history of continental crustal growth beneath the northern East European platform
(withdrawn)
Agasheva Elena, Alexey Agashev, and Vasiliy Chervyakovskiy
08:53–08:55
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PICO2.10
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EGU23-15159
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GD2.2
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ECS
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Virtual presentation
Melt inclusions within olivine in a garnet lherzolite xenolith from the V. Grib kimberlite pipe: the first finding of alkaline-carbonate melt snapshots in the lithospheric mantle beneath the East European craton.
(withdrawn)
Alexey Tarasov, Alexander Golovin, and Elena Agasheva
08:55–08:57
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PICO2.11
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EGU23-12888
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GD2.2
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Virtual presentation
Tatiana Kalashnikova and Sergei Kostrovitsky

The study of mantle xenoliths from kimberlite pipes allows to establish the composition, evolution processes and thermal condition of the lithospheric mantle under ancient cratons. The Mirny kimberlite field belongs to the diamond-bearing kimberlite fields in the center of the Siberian craton. The collection of mantle xenoliths from the Mir pipe (57 samples) was investigated by authors. Four main petrographic groups were identified: peridotites (Grt lherzolites), Grt websterites, Grt clinopyroxenites and eclogites. The pyroxenite xenoliths attract the special attention.   

Garnets from lherzolites and websterites are also characterized by a relatively high Mg# content (75–83) and low TiO2 contents (up to 0.2 wt %). Eclogites are characterized by high-calcium (3.78 - 9.46 wt.%) and high-iron (7.77 - 17.20 wt.%) composition of garnet getting into the ​​wehrlite paragenesis area. Thus, the lithospheric mantle under the Mirny kimberlite field differs from the lithospheric mantle under other diamondiferous fields (for example, Udachnaya kimberlite pipe). The Mirny mantle xenoliths are characterized by the pyroxenites widespread development (up to 50%), the low-Ti composition and deformed lherzolites absence.

In addition, websterites and lherzolites show a wide range of crystallization parameters (600 - 1200°C; 2 - 6 GPa) probably due to their gradual cooling after magmatic crystallization and the exsolution structures formation. Clinopyroxenites are characterized by narrow variations in the P-T crystallization parameters (812 - 960°C; 3-4 GPa) indicated their later crystallization from asthenospheric melts. Eclogites are characterized by relatively low calculated temperature parameters (720–840°C; 2.2–3.7 GPa) confirming their origin in subduction zones at shallow depths. The sporadic calculated values for websterites and clinopyroxenites are locating within the diamond stability area. The use of the Opx - thermobarometer (in samples founding Opx) revealed 2 trends in the crystallization of orthopyroxene. Crystallization of individual Opx grains in websterites occurred earlier than Cpx with higher P-T parameters - higher by ~100С and ~0.5 Ha. The second trend (pressure reduction with a slight decrease in temperature) notes the formation of Opx decay structures in an initially homogeneous crystal of monoclinic pyroxene. Minerals from pyroxenites demonstrate a wide development of melting processes in the lithospheric mantle in the south of the Siberian craton Craton and the formation of megacrystalline pyroxene cumulates. The origin of eclogites is assumed from subducted oceanic crust marking the subduction component in the process of formation of the lithospheric mantle.

The research was supported by Russian Science Foundation grant № 22-77-10073.

How to cite: Kalashnikova, T. and Kostrovitsky, S.: The metasomatic processes and thermal condition of lithosphere mantle under the center of Siberian craton: evidences of pyroxenite xenoliths from Mir kimberlite pipe , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12888, https://doi.org/10.5194/egusphere-egu23-12888, 2023.

08:57–08:59
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PICO2.12
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EGU23-3860
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GD2.2
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Highlight
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On-site presentation
Sergey Kostrovitsky, Igor Ashchepkov, Nikolai Medvedev, Nikolai Karmanov, and Natalia Alymova

Kimberlitic xenocrysts: garnets, pyroxenes, ilmenites, spinels from Anabar region were analyzed by EPMA and LAICPMS.

Reconstructed mantle sections of t Anabar region published (Ashchepkov et al., 2001; 2016; 2019; 2022 show in general, the relative rarity of sub-Ca pyropes  in lower part of the section and the frequency of wehrlite associations in the upper part. Pyroxenite -eclogite lens from 3 to 5 GPa is widely represented in most sections. Ilmenite trends are not long. In several pipes amphiboles from Cr-hornblendes to Cr-richterites were detected.

In the Anabar region (Khardakh and Staro-Rechensky fiedls) The REE patterns of  garnets are characterized by high variations in the spectra, with elevated LREE and HFSE minima, peaks of U, Pb, associated with subduction fluid flows. Pyroxenes are characterized by inclined REE spectra of La/Ybn ~15 to 20 and with varying HREE with subduction-related Ba, U, Pb peaks. But pyroxenes with plume related spectrums of with smooth spider diagrams (SD) are often found in pyroxenite lens.

Garnets from the Kuranakh field (Malokuonamskaya, Losi, Trudovaya, Universitetskaya etc) are divided into dunite-garburgite with low REE and LREE enrichment and wehrlite with convex REE maximum Gd, Eu and high concentrations of HREE often enriched in Th , U varying Ta-Nb and always low Zr-Hf.  Clinopyroxenes from the Malokuonamskaya pipe often have a local minimum of HREE and variations in the slope and enrichment of the REE spectra. On the CD, the peaks of Ba are varying, they show Ta, Nb enrichment and minima in Zr-Hf.

The garnets from the Universitetskaya pipe are mainly lherzolite-harzburgite with signs of subduction genesis (U peaks), and wide variations of HFSE sometime with Zr–Hf enrichment, due aqueous metasomatism. Clinopyroxenes are generally more diverse in REE spectra, Nb peaks with wide variations of Ba, Th-U and HFSE are common on CD

The Losi dike has a high content of perovskites, with highly enriched spectra with a slope with a decrease in highly charged and Pb and ilmenites with high and inclined REE spectra due to fractionation of proto-kimberlite (essentially carbonatite) melt. The eclogitic minerals with Eu anomalies and peaks of U, Ba and low HFSE are common.

In most mantle sections, ancient subduction sings are recorded in pyrope garnets, an partially adakite metasomatism in pyroxenes. Later they were modified by the action of plume carbonatite melts. The middle pyroxenite-eclogite lens originated as the boundary of the crust in ancient Archaic times. The upper wehrlitic part of the section arose during the melting of the pyroxene lens in the middle part and the migration of melts to the upper part. Protokimberlite metasomatism is not very pronounced. No signs of the supposed delamination of the lithosphere (Griffin et al, 2005) were found in the sections, which was also proved by Opx-Gar thermobarometry under the Duken field (Ashchepkov, 2003). The lower part of the section is depleted  so garnet and pyroxenes are rare and reflect low-temperature geotherm.

 

Grant RBRF 19-05-00788.

 

How to cite: Kostrovitsky, S., Ashchepkov, I., Medvedev, N., Karmanov, N., and Alymova, N.: Mineralogy and geochemistry of the kimberlite xenocrysts from the Anabar region, Yakutia, Russia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3860, https://doi.org/10.5194/egusphere-egu23-3860, 2023.

08:59–09:01
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PICO2.13
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EGU23-3560
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GD2.2
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On-site presentation
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Igor Ashchepkov, Nikolai Vladykin, Irina Sotnikova, Nikolai Medvedev, Nikolai Karmanov, and Natalia Alymova

Minerals from leucite lamproites of the Murunsky alkaline massif (Vladykin, 2000; 2005; Vladykin, 2009) were analyzed by electron microscopy in the sections of 700 grains of minerals (IGM SB RAS) and LA ICP MS (IIC SB RAS) - 40 grains. Pyroxenes, amphiboles, various micas including varieties of the Ba type, leucites and nephelines, Ba and K feldspars, eudialyte, barite, stroztianite, ilmenites, Cr- spinelides, Ti magnetites, apatites, tourmaline, and various carbonates and sulfides: pyrrhotite, petlandite, chalcopyrite, murunite, smithsonite, galena.

 

Pyroxenes are divided into 3 groups from diopsides to augites and aegirines, revealing a continuous series of compositions according to MgO (Fig. 1). Amphiboles K-richterites and arfversonites, and Ca-Fe ackermanites. Complete ranges from phlogopites to biotites have been established among micas. The proportion of Ba micas is significant. In the diagram  genetic digram (Minchell, 1995 )(Fig. 2) falls into the field of ailikites or orangeites,  and lamproites. Leucites and nephelines occurs  friquiently. Numerous apatites are characterized by Ca-Sr substitution and noticeable F contents (to 3%). K-type eudialytes and a mineral close to priderite were found.

 

In the TRE diagrams (Fig.3), pyroxenes are characterized by La-enriched ~200-250 weakly inclined spectra of La/Ybn (2-3) that spread out in the HREE wing. Amphiboles of the K-Na-Ca are characterized show inclined spectra with Ho-Tm depression,  LILE peaks elevated Zr, Hf, Y and Ta-Nb minima. The more alkaline amphiboles are characterized by reduced REE concentrations, more  elevated Zr-Hf. Ultra-alkaline amphiboles (richterite and arfvedsonite) have higher REE contentswith characteristic U-shaped spectra, very high LILE contents high peaks of Sr, Zr, Hf. Phlogopites have oblique U-shaped spectra with a sharp peak Eu interference Ti. Very high LILE with a peak at Va, Sr, Y, Pb are typical.

Low REE and especially LREE with a peak of Eu are characteristic of leucites. U, Sr, Pb peaks are also characteristic, and HFSE vary. The REE spectra of K-Ba feldspars are similar to those of phlogopite. High peaks of LILE, Sr, Pb, Y are expressed on spiderdiagrams