Mafic dykes can preserve near-peak metamorphic assemblages in granulitic terranes and often are key to deciphering their pressure-temperature-time-deformation (P-T-t-D) history. They are particularly important in high-grade polymetamorphic terranes, where younger metamorphic events may be poorly recorded in other units. The middle to lower crustal units of the Grenville Front Tectonic Zone (GFTZ) in western Québec, Canada, present a unique opportunity to address this issue, having experienced two metamorphic events separated by more than 1.6 billion years. The GFTZ exposes parautochthonous restitic orthopyroxene + garnet-bearing paragneisses and associated two-micas pegmatite dykes. These were formed in the Superior Craton during c. 2.6 Ga granulite-facies metamorphism (M1) and affected by a loosely constrained c. 1.0 Ga overprint during the Grenvillian orogeny (M2). Following M1 and prior to M2, the GFTZ have been intruded by Proterozoic gabbro dykes that can be used to monitor the conditions and timing of M2. In this contribution, we present new field relationships, whole rock geochemistry, in situ laser ablation U-Pb titanite and Lu-Hf garnet geochronology, along with isochemical phase equilibria modeling to provide quantitative P-T-t-D estimates of the metamorphism preserved in the mafic dykes.

Field evidence shows that ~10 m thick metagabbro dykes cross-cut foliated paragneiss and pegmatite dykes. Their immobile element geochemical signatures are consistent with those from regionally recognized Proterozoic mafic dyke swarms intruding the Superior Craton. Metagabbros are characterized by an assemblage of plagioclase + hornblende + clinopyroxene + garnet + orthopyroxene + quartz + titanite. Garnet coronas surrounding relict magmatic clinopyroxene in contact with plagioclase are common in dyke cores, contrasting with granoblastic and migmatitic assemblages in dyke margins. Five metagabbro samples returned in situ Lu-Hf garnet dates in the range of 1124 to 920 Ma and U-Pb titanite dates from 1022 to 985 Ma, interpreted as the timing of M2 metamorphism and consistent with documented Grenvillian metamorphism. Isochemical phase equilibria modeling of a granoblastic hornblende + plagioclase + clinopyroxene + quartz + garnet migmatitic assemblage in a dyke margin indicate equilibrium conditions of 833 ± 12 °C and 9.9 ± 0.4 kbar, corresponding to mid- to high-pressure granulite conditions.

Our results confirm a c. 1.0 Ga granulite-facies overprint attributed to the Grenvillian Orogen (M2). It is noteworthy that the high-grade assemblage is only expressed in the Proterozoic mafic dykes and that the host migmatitic paragneiss did not pervasively recrystallize during M2, potentially due to its restitic nature. This contrast in lithological reactivity resulted in a differential metamorphic record, emphasizing that the Grenvillian granulitic overprint could easily be overlooked if metagabbros are neglected. In conclusion, the results presented herein underscore the critical role of metamorphosed mafic dykes in disentangling the complex evolution of polymetamorphic granulitic terranes.

How to cite: Darveau, J., Guilmette, C., Godet, A., Jouvent, M., Côté-Roberge, M., and Larson, K.: Learning from mafic dykes in polymetamorphosed granulite terranes: an example from the Grenville Front Tectonic Zone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14676, https://doi.org/10.5194/egusphere-egu25-14676, 2025.

Where, when, and why large-scale shear zones nucleate and propagate into the continental lithosphere are critical issues that challenge the research in tectonics. The East Variscan shear zone is one of the crustal-scale strike-slip faults that shaped the Variscan orogenic crust during late Carboniferous time. Field-based structural analysis and petrological observations demonstrate that suprasolidus high-strain deformation zones and metagranite occurrences are spatially correlated. Among the three dominant lithologies forming this orogenic middle crust (metapelite, metagraywacke, and metagranite), petrological observations and phase equilibrium modeling indicate that the latter is the first lithology that melts during collision-induced heating, in response to H2O-fluid-saturated melting. Our field data and modeling suggest that the water-fluxed melting of metagranite has a primary rheological control on the localization, instigation, and growth of crustal-scale shear zones in the middle crust. Thus, the distribution and geometry of metagranite at the crustal scale could be regarded as critical parameters influencing the rheological inheritance governing the tectonic evolution and localization of bulk strain in the continental lithosphere.

How to cite: Vanardois, J., Trap, P., and Marquer, D.: Crucial role of water-present melting in metagranite: Implicationsfor the instigation of crustal-scale shear zones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2492, https://doi.org/10.5194/egusphere-egu25-2492, 2025.

Monazite, a key accessory mineral in high-grade metamorphic rocks, serves as both a robust geochronometer and a primary reservoir for rare earth elements (REE), Th, and U. This study investigates melt inclusions within monazite and garnet to elucidate the processes of crustal melting and element partitioning during granulite facies metamorphism in the Bohemian Massif.
Nanogranitoid inclusions, identified through Raman spectroscopy and electron microscopy, exhibit polycrystalline textures containing quartz and feldspar polymorphs, micas, and occasionally carbonate phases. These inclusions are found in chemically distinct domains of monazite and garnet, offering valuable insights into the interplay between melt entrapment, mineral growth, and metamorphic conditions. Compositional zoning in garnet, characterized by variations in major and trace elements, alongside the corresponding domains in monazite, provides a detailed record of the pressure-temperature (P–T) trajectory during high-grade metamorphism.
Our findings reveal two generations of garnet, each showing distinct chemical zoning and closely linked to monazite inclusions with different ages. Monazite grains dated to ~370 Ma are associated with the first garnet generation (Garnet1), while monazite grains dated to ~340 Ma are associated with the second garnet generation (Garnet2). These monazite inclusions, along with matrix-hosted monazite grains, display contrasting REE and Th/U patterns, reflecting diverse growth conditions and the impact of garnet breakdown during decompression.
The systematic investigation of these inclusions, alongside their textural and chemical context, enhances our understanding of monazite stability in melt-bearing systems and its role in recording the temporal evolution of crustal melting processes. This integrative approach establishes a robust framework for deciphering the intricate relationships between mineral chemistry, melt inclusions, and P–T paths. These findings underscore the critical role of accessory minerals like monazite as indispensable archives of crustal evolution.

How to cite: Sorger, D., Hauzenberger, C. A., Finger, F., and Linner, M.: Tales of Monazite, Garnet, and Melt: Linking Mineral Growth and Partial Melting to P–T Evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8442, https://doi.org/10.5194/egusphere-egu25-8442, 2025.

In zircon, transgressive textures across the oscillatory zoning and associated chemical modifications were mostly attributed to the process of fluid-mediated coupled dissolution-precipitation (CDP) over the past c. 20 years. Some works also admitted a possible role of melt in zircon CDP, expressing it for example by “fluid/melt”, but usually without explicit documentation of melt presence. The studies of melt-mediated zircon modification by CDP are thus extremely rare, and show an important but underrated process, with consequences on geological interpretation of zircon ages and chemical composition.

We choose one of the most common crustal rock types, a meta-granite, which undergone migmatization, and focused on modification of zircon textures and chemistry. To unravel primary and secondary zircon textures we use combination of high-resolution cathodoluminescence (CL), back-scattered electron (BSE) and secondary-electron (SE) images, because in CL most of the secondary textures were not visible. To relate zircon texture and date with trace- and rare earth element (REE) composition we use laser ablation–split-stream inductively coupled plasma–mass spectrometry (LASS). We relate the mineral inclusions with zircon textures, and for the secondary metamorphic inclusions we compare their assemblage and mineral chemistry with the rock assemblage and infer P–T conditions of their formation. Because the textures are typical of coupled dissolution-precipitation process and the P–T conditions of the secondary inclusions and matrix assemblage are above the wet solidus, we interpret zircon modification as caused by melt-mediated coupled dissolution-precipitation process.   

Oscillatory zoning is commonly blurred to a variable degree and it is in places truncated by patchy, convolute or structureless embayments. The irregular and relatively sharp boundaries of the embayments may be spatially associated with micro-porosity located ahead, and are interpreted as modification fronts of dissolution-precipitation. Some modification fronts are superimposed and relative timing can be inferred. Micro-porosity and inclusions are arranged in trails along modified BSE-light grey channels and are spatially associated with depressions at the surface, indicating more pronounced dissolution over precipitation. Larger inclusions tend to be located at the joints of the channels. The metamorphic zircon domains are characterized by an overall decrease of HREE with large variation in Yb/Gd, increase or decrease in LREE, increase in U, and decrease of Th and Th/U, compatible with presence of melt, garnet and titanite. Inclusions of Ph−Grt−Ttn are compatible with the matrix assemblage of Grt−Ph−Bt−Ttn−Kfs−Pl−Qz±Rt±Ilm, and equilibrated at eclogite-facies, at 15−17 kbar and 690–740 °C. The melt-mediated zircon modification resulted in a smear of mostly concordant dates from protolith oscillatory zoned domains with Cambro-Ordovician age to c. 330 Ma.

How to cite: Stipska, P., Kylander-Clark, A., Racek, M., Zavada, P., and Hasalova, P.: Melt-assisted coupled dissolution-precipitation of zircon in metagranite, Bohemian Massif, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18130, https://doi.org/10.5194/egusphere-egu25-18130, 2025.

The Caucasus is located at the convergence of the Eurasian and African-Arabian tectonic plates and represents a link between the European and Asian components of the Mediterranean (Alpine-Himalayan) collisional mobile belt. This region offers valuable insights into understanding collision tectonics and high-grade metamorphism. The presented study aims at investigating the high-grade metamorphism and crustal melting processes in the Greater Caucasian Main Range zone, which is subdivided into the Pass and the Elbrus sub-zones. They differ from each other in terms of geological structures, lithologies, metamorphism and magmatism. Migmatization and partial melting in the Caucasus refers to Cadomian (626±2 Ma) and Caledonian (461±5.3, 468±5, 471.7±4.6 Ma) stages of high-temperature regional metamorphism of Elbrus subzone infrastructure. The final, low-temperature stage of regional metamorphism occurred during the Variscan orogeny. The Elbrus subzone represents a migmatitic complex and its study is a key for understanding high-temperature metamorphic and anatectic processes in this region. This study combines geochronological data with detail mineralogical and textural analyses of migmatites from the Elbrus sub-zone to determine the conditions and mechanisms of partial melting and to shed light on the relationships between crustal anatexis and tectonics. The migmatites collected in the River Nenskra valley (Upper Svaneti region) are mostly fine-to medium-grained stromatic metatexites, characterized by light bands composed predominantly of quartz, potassium feldspar and plagioclase, and dark bands with biotite, garnet and sillimanite. Leucosomes contain euhedral feldspar crystals and thin quartz-feldspar films along grain boundaries, which can be interpreted as microstructures indicating the presence of former melt. Garnet crystals are often characterized by numerous tiny inclusions, giving them a cloudy appearance. MicroRaman investigation reveals the presence of cristobalite, graphite, phlogopite, biotite, chamosite, carbonate, CH₄ and N₂ in the vast majority of these inclusions, which are interpreted as former fluid inclusions and not as nanogranitoids. SEM analysis results show enrichments of Mn at the rims of some garnet crystals, which are related to local resorptions of the garnet crystals and replacement by biotite. In the highest grade samples muscovite is rare, displays a skeletal shape, is not in contact with quartz and is adjacent to crystals of K-feldspar and sillimanite. These observations suggest that partial melting conditions exceeded the stability of Ms+Qz and reached the stability of Kfs+Sil. In addition, inclusions of green spinel have been observed in some sillimanite clots, which represent the product of staurolite decomposition. These are the only microstructures that provide constraints on the pre-anatectic history of these migmatites. The proposed conditions of regional metamorphism suggest temperatures and pressures corresponding to upper amphibolite and up to granulite facies. These conditions support the occurrence of partial melting processes, followed by slow cooling. To further refine the understanding, new microstructural, microchemical, and geochronological data will be presented, providing deeper insights into the petrogenesis of migmatites in the Greater Caucasus. This work will also contribute to understanding the thermal regime of regional high-grade metamorphism and melting in other metamorphic structural zones of the Caucasus.

ACKNOWLEDGEMENTS: This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG) [FR-22-11295].

How to cite: Tsutsunava, T., Javakhishvili, I., Cesare, B., Bartoli, O., Shengelia, D., Chichinadze, G., and Beridze, G.: New Insights on Partial Melting and Migmatization in the Greater Caucasus Main Range Zone , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6482, https://doi.org/10.5194/egusphere-egu25-6482, 2025.

A lot of emphasis has been given lately to SiO₂ polymorphs in metamorphic rocks. A development of quartz-in-garnet elastic barometry and Ti-in-quartz thermometry refocused attention of metamorphic petrologists on this chemically simple and ubiquitous mineral in virtually all types of metamorphic rocks. A need for chemical equilibrium independent thermobarometric methods and a growing evidence for mineral reaction overstepping promoted in-depth studies of quartz behavior as inclusion in stiffer phases such as garnet and associated strain and stress development as well as fostered common usage of trace element thermometers. On the other hand, less common coesite became the primary target phase in metamorphic studies tackling a problem of deep subduction of Earth’s crust to mantle depths. A common routine to identify the latter mineral is to look for specific microtextures such as radial cracks around coesite inclusions in other minerals and/or characteristic pseudomorphs such as polycrystalline and palisade quartz. Subsequent confirmation of the presence of coesite with Raman spectroscopy and/or electron backscattered diffraction (EBSD) is needed. Therefore, we decided to look for (a) yet another way of quick identification of coesite, and (b) potential development of an alternative geothermobarometric technique applied to quartz and coesite. Here we report preliminary results obtained using acoustic microscopy, a vastly unknown technique in petrological community. Our preliminary tests on quartz monocrystals show that acoustic wave velocity depends on quartz orientation. However, the test on coesite and palisade quartz from Dora Maira shows that coesite reveals faster wave velocity than quartz regardless the crystallographic orientation. The latter is, in fact, not surprising since the method in question is primarily dependent on a density and elastic properties of the tested material. Nonetheless, to our knowledge an empirical test of this kind has not been done before. Thus, we can preliminarily conclude that the acoustic microscopy can be used as an alternative tool to quickly identify coesite. A development of a new thermobarometer would require a careful EBSD pre-study though. This obstacle together with limited access to acoustic microscopes in general may hinder this process. On the other hand, a use of acoustic impedance to image either growth and/or deformation zones in minerals or specific microtextures of multimineral systems appears to be especially advantageous.

Supported by the National Science Centre (Poland) grant no. 2021/43/D/ST10/02305.

How to cite: Majka, J., Potočný, T., Litniewski, J., Stepinski, T., Włodek, A., and Kośmińska, K.: Acoustic microscopy of quartz and coesite: yet another way to look at old good metamorphic fellas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8082, https://doi.org/10.5194/egusphere-egu25-8082, 2025.

Sulfur is transferred into the overlying mantle wedge during subduction of oceanic plates, with important ramifications for magmatic processes in volcanic arcs. Many studies have shown that arc magmas are more oxidized and enriched in ³⁴S than mid-ocean ridge basalts, which has been linked to the transfer of slab-derived volatiles, such as sulfate, into the overlying mantle wedge and into arc magmas. However, the transfer mechanisms and the oxidation states of slab fluids is still under debate, and particularly the role of sulfur is currently widely discussed. Here we present bulk rock and in situ sulfur isotope results from metasomatic, eclogitic metagabbros from the Voltri Massif in Italy that are in contact with serpentinites (Schwarzenbach et al., 2024). Previous petrological work of this contact showed that metasomatism by fluid-mediated mass transfer of Mg from the serpentinite into the metagabbro caused formation of actinolite-chlorite schists and metagabbro rich in epidote and Na- and Na-Ca amphiboles along the contact (Codillo et al., 2022). Abundant euhedral to subhedral pyrite in the metasomatized metagabbro show distinct correlations between in situ sulfur isotope analyses and sharp Co and Ni growth zones documenting multiple generations of pyrite formation. In particular, a trend of increasing δ³⁴S values from core to rim in pyrite associated with inclusions of distinct high pressure silicate minerals documents the input of ³⁴S-enriched sulfur during metasomatism of the eclogitic metagabbros concurrent to subduction metamorphism. Using thermodynamic modeling our study shows that the infiltrating fluids equilibrated with the serpentinite before entering the metagabbro and that these fluids were HS^--bearing. Infiltration of these HS^--bearing and ³⁴S-enriched fluids led to redox reactions in the Fe-Ti metagabbro involving sulfur, iron, and likely carbon, and the formation of euhedral pyrite with δ³⁴S values of up to 12.5‰ in the metasomatized metagabbro. We argue that this process of ³⁴S-enriched sulfur mobilization from serpentinites is pervasive along the plate interface in subduction zones and infer that melting of such metasomatic material can explain the ³⁴S-enriched signatures observed in arc magmas.

References:

A. Codillo et al., Fluid-Mediated Mass Transfer Between Mafic and Ultramafic Rocks in Subduction Zones. Geochemistry, Geophysics, Geosystems 23, e2021GC010206 (2022).

M. Schwarzenbach et al., Mobilization of isotopically heavy sulfur during serpentinite subduction. Science Advances 10, eadn0641 (2024).

How to cite: Schwarzenbach, E., Dragovic, B., Codillo, E., Streicher, L., Scicchitano, M., Wiechert, U., Klein, F., Marschall, H., and Scambelluri, M.: Sulfur transfer during subduction of serpentinite: insights from the Voltri Massif, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2498, https://doi.org/10.5194/egusphere-egu25-2498, 2025.

Fluid–rock interactions play a key role in the formation, evolution and recycling of the Earth’s crust. For fluids to infiltrate rocks and enable and sustain fluid-mediated mineral transformations, fluid pathways are required. Time scales of fluid-mediated rock transformations cover a wide range from several million years to several month in various geological settings. In this study, we examined the underlying mechanisms and timescales of amphibolitization of mafic crust. For this purpose we performed a detailed mineralogical, petrophysical and thermodynamic analysis of a dry, essentially “non-porous” gabbro that was hydrated and transformed into an amphibolite under amphibolite-facies conditions. The amphibolitization process was triggered by fluid infiltration through a newly opened N–S striking fracture network and allowed the fluid to pervasively infiltrate the rock. Thermodynamic modelling and petrological data show that the transition from gabbro to amphibolite was accompanied by densification and related porosity formation. The modes and compositions of minerals within partly-amphibolitized rocks indicate that besides the uptake of H₂O, no significant mass exchanges were necessary for this transformation, at least on the thin-section scale. Once the gabbro was almost entirely amphibolitized, its mineral content and mineral chemistry no longer changed, so the progress of amphibolitization progress was controlled by fluid availability. To estimate the duration of the amphibolitization we set up a reactive transport model based on local equilibrium thermodynamics, mass balance and Darcy flow, which addresses the mineralogical and petrophysical changes of the rock along the sampled profile at constant ambient amphibolite-facies P–T conditions. Starting from a non-porous rock, the model calculated reaction-induced porosity, permeability, and fluid pressure evolution based on the local bulk composition and the evolving mineral paragenesis. We reproduced the extend of the reaction front by adjusting fitting parameters such as, initial fluid pressure, permeability or fluid viscosity. We repeated these calculations for different reaction front widths we measured in the outcrop to obtain a time estimate of the hydration process that resulted in the amphibolitization of the gabbroic crust.

How to cite: John, T., Grund, S., and Vrijmoed, J.: Amphibolitization of mafic crust: mechanism and time scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18348, https://doi.org/10.5194/egusphere-egu25-18348, 2025.

Raman Spectroscopy of Carbonaceous Matter (RSCM) thermometry is a widely utilized method for estimating peak metamorphic temperatures based on the crystallinity and composition of carbonaceous matter (CM). In this study, we apply RSCM thermometry to samples from the contact aureole of the Torres del Paine Intrusive Complex (TPIC) and compare these temperature estimates with constraints from phase petrology and thermal modeling. While Raman spectra reveal a systematic increase in CM crystallinity toward the intrusion, peak temperatures estimated with RSCM are consistently lower than the modeled temperatures in the outer and middle part of the aureole, while both approaches give consistent temperatures close to the contact.

2-D thermal models suggest that the heating of the metasediments occurred over 2,000–10,000 years, while cooling occurs over some tens of thousands of years, depending on proximity to the intrusion, as well as the relative position of the sample with respect the intrusion (roof, side, or below). A review of contact metamorphic studies conducted around different sizes of intrusions underscores the critical role of the heating pulse duration.  Hence, RSCM thermometry needs to take into account the thermal history, as was similarly shown for sedimentary basins and Anchizonal metamorphism (Sweeney and Burnham, 1990).

To address this limitation, we extend a first-order kinetic model originally developed for vitrinite reflectance by Sweeney and Burnham (1990) to describe CM crystallinity evolution by considering a total set of 34 parallel reactions that includes 14 new reactions with higher activation energies to account for the reactions that dominate maturation at higher temperatures, responsible for transforming amorphous CM into graphite. Our new kinetic model was calibrated by assuming that the maturations described by the thermometer for regional metamorphism were obtained by maintaining the temperature at the peak metamorphic temperature for at least 1Myr.  Using this approach we find a better fit for maximum temperatures obtained in the Torres del Paine contact aureole. Our results highlight the importance of kinetic effects for RSCM thermometry. Hence, we strongly advise against the use of the RSCM thermometer for short-lived thermal pulses, unless an approximate knowledge of the temperature-time history is known. 

References

Sweeney, J.J. and Burnham, A.K. (1990) ‘Evaluation of a Simple Model of Vitrinite Reflectance Based on Chemical Kinetics’, AAPG Bulletin, 74(10), pp. 1559–1570. Available at: https://doi.org/10.1306/0C9B251F-1710-11D7-8645000102C1865D.

How to cite: Ariza Acero, M. M., Baumgartner, L. P., and Foster, C. T.: The kinetics of organic maturation in the Torres del Paine contact aureole and lessons for RSCM thermometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18266, https://doi.org/10.5194/egusphere-egu25-18266, 2025.

The Eastern Ghats Belt (EGB), along the eastern coast of the Indian peninsula, forms a key crustal element in reconstructing the Palaeoproterozoic and Neoproterozoic supercontinents, Columbia (~1.9-1.6 Ga) and Rodinia (~1.1-0.9 Ga), respectively. The connection of the south-eastern segment of the EGB with east Antarctica, Australia, and Laurentia in an accretionary orogeny during the assembly of the Columbia has been established. Additionally, the central and western segments of the EGB are believed to have accreted to the Rayner Complex of Western Australia and East Antarctica during the assembly of the Rodinia supercontinent.

            In this contribution, we constrain the Proterozoic tectonothermal events recorded from the khondalites and granitoids occurring within the northernmost crustal segment of the EGB, as the major lithodemic units. In-situ monazite analysis from poly-metamorphosed garnet-sillimanite-biotite-quartz-feldspar bearing khondalites helps to establish two major metamorphic events: M_1KH and M_2KH. The earliest anatectic event (M_1KH) was recorded at 1.1 Ga leading to the formation of peritectic garnet, potash felspar, and melt. A collisional tectonic setting is implied by a clockwise P-T path constrained for the mid-crustal partial melting event (M_1KH; ~8-9 kbar, >760°C). The second metamorphic event (M_2KH) occurred in a melt-absent solid-state condition (~7.8 Kbar, 675°C). The M_2KH event occurred along an anticlockwise P-T trajectory with isobaric cooling. The monazite age ranges from 922±17 Ma and 909±8 Ma correlating with the isobaric cooling of the khondalites.

The granitoid bodies associated with the khondalites preserve evidence of multiple phases of deformation. Some of these granitoids are migmatites.  Zircons from one of the samples of the undeformed granitoids yield a crystallization age of ca. 1700 Ma. The monazite ages yielded from the granitoids show crystallization ages between ~1041-997 Ma. Monazites from granitoids produce a second peak at ~934-884 Ma, indicating the litho units experienced a partial melting event which is correlated with Rodinia supercontinent formation when the belt was a part of the Rayner Complex. The creation of the extensional Mahanadi Shear Zone is linked to the third monazite population within the granitoids, which yields ages ranging from approximately 750 to 740 Ma.

The present study implies that signatures of both Columbia and Rodinia ages are stronger in the northernmost segment of the EGB. The Imprint of a 1700 Ma event significantly impacts our comprehension of the crustal domains of the EGB that formed during the accretionary orogeny as part of the Columbia assembly. A linkage of significant accretionary belts around preexisting cratons involving Laurentia, Antarctica, South Africa, and Australia can be established with the 1700 Ma events in the northern EGB. The entire EGB from the north to south thus can be added to a hypothetical correlation of orogenic belts in several continents that underwent orogenesis between 1800 and 1700 Ma, reflecting Columbia's expansion. The findings in this study further imply that all the crustal domains of the EGB were unequivocally part of the accretionary orogenies leading to the assembly of the Rodinia.

How to cite: Behera, S. R. and Saha, L.: Tectonothermal evolution of the northernmost crustal segment of the Eastern Ghats Belt, India, and its linkage to Columbia and Rodinia assembly, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-595, https://doi.org/10.5194/egusphere-egu25-595, 2025.