New zircon radiometric U-Pb ages and Lu-Hf isotopic data from the ultramafic-mafic sequences of Ranau and Telupid (Sabah, eastern Malaysia): Time to reconsider the geological evolution of Southeast Asia?

New zircon U-Pb geochronology from a peridotite suite near Ranau and the Telupid ophiolite in Sabah, eastern Malaysia, contradict previous studies, which assumed that the Sabah mafic-ultramafic rocks are largely ophiolitic and Jurassic–Cretaceous in age. We show that these rocks formed during a magmatic episode in the Miocene (9.2–10.5 Ma), which is interpreted to reflect infiltration of melts and melt-rock reaction in the Ranau subcontinental peridotites during extension, and concurrent seafloor spreading forming the Telupid ophiolite further south. Older zircons from the Ranau peridotites have Cretaceous, Devonian, and Neoproterozoic ages. Zircon Lu-Hf isotopic data suggest their derivation from a depleted mantle. However, significant proportions of crustal components have been incorporated in their genesis, as evidenced by their less-radiogenic Hf signature compared to a pristine mantle reservoir. The involvement of a crustal component is consistent with our interpreted continental setting for the Ranau peridotite and formation in a narrow backarc basin for the Telupid ophiolite. We infer that the Sulu Sea, which was expanding throughout much of the Miocene, may have extended to the southwest into central Sabah. The Telupid oceanic strand formed during the split, collapse, and rollback of the Sulu arc due to the subduction of the Celebes Sea beneath Sabah. Incorporation of the Sulu arc in the evolving Miocene oceanic basin is a potential source to explain the involvement of crustal material in the zircon evolution of the Telupid ophiolite.

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Age and petrogenesis of the Qassiarsuk carbonatite-alkaline silicate volcanic complex in the Gardar rift, South Greenland

Mineralogical Magazine ◽

10.1180/minmag.1997.061.407.03 ◽

1997 ◽

Vol 61 (407) ◽

pp. 499-513 ◽

Cited By ~ 26

Author(s):

Tom Andersen

Keyword(s):

Volcanic Rocks ◽

Single Stage ◽

Volcanic Complex ◽

Crustal Material ◽

Crustal Component ◽

Depleted Mantle ◽

Common Parent ◽

Nd Model Age ◽

Extrusive Carbonatite ◽

Age Estimates

AbstractThe Qassiarsuk (formerly spelled Qagssiarssuk) complex is located in a roughly E–W trending graben structure between Qassiarsuk village and Tasiusaq settlement in the northern part of the Precambrian Gardar rift, South Greenland. The complex comprises a sequence of alkaline silicate tuffs and extrusive carbonatites interlayered with sandstones, and their subvolcanic equivalents, which represent possible feeders for the extrusive rocks. The Rb-Sr, Sm-Nd and Pb isotopic characteristics of 65 samples of extrusive carbonatite- and silicate tuffs and carbonatite diatremes have been determined by mass spectrometry. The Qassiarsuk complex can be dated to c. 1.2 Ga by Rb-Sr and Pb-Pb isochrons on whole-rocks and mineral separates, agreeing with previous isotopic ages for the volcanic rocks of the Eriksfjord formation in the Eriksfjord area of the Gardar rift, but not with previous, indirect age estimates of >1.31 Ga for assumed Eriksfjord equivalents in the Motzfeldt area further east. Recalculated isotopic compositions at 1.2 Ga indicate that the Qassiarsuk carbonatite- and alkaline-silicate magmas were comagmatic and derived from a depleted mantle source (εNd>4, εSr<−13, time-integrated, single- stage 238U/204Pb ≤ 7.4). The mantle-derived magmas were contaminated with crustal material, equivalent to the local, pre-Gardar granites and gneisses and sediments derived from these. The crustal component has a depleted mantle Nd model age of 2.1-2.6 Ga; at 1.2 Ga it was characterized by εSr = +76, εNd = −8.4, time-integrated, single- stage 238U/204Pb = 8.2−8.3. Strong decoupling of the Pb from the Sr and Nd isotopic systems suggests that the contamination happened only after carbonatitic and alkaline-silicate magmas had evolved from a common parent, by processes such as liquid immisicibility and/or fractional crystallization. Post-magmatic hydrothermal alteration (oxidation, hydration of mafic silicates, carbonatization of melilite) may have contributed further to the contamination of the carbonatite and alkaline silicate rocks of the Qassiarsuk complex.

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Oxygen-Hafnium-Neodymium Isotope Constraints on the Origin of the Talnakh Ultramafic-Mafic Intrusion (Norilsk Province, Russia)

Economic Geology ◽

10.5382/econgeo.4743 ◽

2020 ◽

Vol 115 (6) ◽

pp. 1195-1212 ◽

Cited By ~ 1

Author(s):

Kreshimir N. Malitch ◽

Elena A. Belousova ◽

William L. Griffin ◽

Laure Martin ◽

Inna Yu. Badanina ◽

...

Keyword(s):

Crustal Contamination ◽

Ultramafic Rocks ◽

Magma Chambers ◽

Nd Isotope ◽

Crustal Component ◽

Depleted Mantle ◽

Magma Sources ◽

A Minor ◽

T Values

Abstract The ultramafic-mafic Talnakh intrusion in the Norilsk province (Russia) hosts one of the world’s major platinum group element (PGE)-Cu-Ni sulfide deposits. This study employed a multitechnique approach, including in situ Hf-O isotope analyses of zircon combined with whole-rock Nd isotope data, in order to gain new insights into genesis of the Talnakh economic intrusion. Zircons from gabbrodiorite, gabbroic rocks of the layered series, and ultramafic rocks have similar mantle-like mean δ18O values (5.39 ± 0.49‰, n = 27; 5.64 ± 0.48‰, n = 34; and 5.28 ± 0.34‰, n = 7, respectively), consistent with a mantle-derived origin for the primary magma(s) parental to the Talnakh intrusion. In contrast, a sulfide-bearing taxitic-textured troctolite from the basal part of intrusion has high δ18O (mean of 6.50‰, n = 3), indicating the possible involvement of a crustal component during the formation of sulfide-bearing taxitic-textured rocks. The Hf isotope compositions of zircon from different rocks of the Talnakh intrusion show significant variations, with ɛHf(t) values ranging from –3.2 to 9.8 for gabbrodiorite, from –4.3 to 11.6 for unmineralized layered-sequence gabbroic rocks, from 2.3 to 12 for mineralized ultramafic rocks, and from –3.5 to 8.8 for mineralized taxitic-textured rocks at the base of the intrusion. The significant range in the initial 176Hf/177Hf values is ascribed to interaction of distinct magma sources during formation of the Talnakh intrusion. These include (1) a juvenile source equivalent to the depleted mantle, (2) a subcontinental lithospheric source, and (3) a minor crustal component. Initial whole-rock Nd isotope compositions of the mineralized taxitic-textured rocks from the base of the intrusion (mean ɛNd(t) = –1.5 ± 1.8) differ from the other rocks, which have relatively restricted ranges in initial ɛNd (mean ɛNd = 0.9 ± 0.2). The major set of ɛNd values around 1.0 at Talnakh is attributed to limited crustal contamination, presumably in deep magma chambers, whereas the smaller set of negative ɛNd values in taxitic-textured rocks is consistent with greater involvement of a crustal component and reflects an interaction with the wall rocks during emplacement.

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Nd and Sr isotopic constraints on the petrogenesis of the west side of the northern Coast Mountains batholith, Alaskan and Canadian Cordillera

Canadian Journal of Earth Sciences ◽

10.1139/e91-085 ◽

1991 ◽

Vol 28 (6) ◽

pp. 939-946 ◽

Cited By ~ 30

Author(s):

Scott D. Samson ◽

P. Jonathan Patchett ◽

William C. McClelland ◽

George E. Gehrels

Keyword(s):

Late Cretaceous ◽

Crustal Thickening ◽

Northern Coast ◽

Crustal Material ◽

The West ◽

Crustal Component ◽

Coast Mountains ◽

Early Proterozoic ◽

Depleted Mantle ◽

Wrangellia Terrane

Nd and Sr isotopic ratios are reported from 15 samples of plutons of the northern Coast Mountains batholith (CMB), between. the Alexander–Wrangellia terrane and the Stikine terrane of southeastern Alaska. Samples of plutons that are part of the Late Cretaceous – Eocene CMB suite have a range in initial εNd of −3.0 to −0.2 and 87Sr/86Sr of 0.70494–0.70607. There is no correlation of isotopic ratio with age, lithology, or geographic location of these plutons. Two plutons that are probably older than the bulk of the CMB plutons have present-day εNd values of −6.8 and −2.6.The Late Cretaceous – Eocene plutons have Nd depleted-mantle model ages (tDM) of 620–1070 Ma. These data indicate that the northern CMB must contain a significant component of old, evolved continental crust. The presence of an old crustal component is further demonstrated by inherited zircons of average Early Proterozoic age contained in some plutons. The mid to Late Proterozoic tDM ages of the CMB plutons are therefore a result of a mixture of Early Proterozoic crustal material with. younger, juvenile crust. The most likely source of this old crustal component is the Yukon–Tanana terrane, a fragment composed of ancient crustal material that occurs within and directly to the west of the northern CMB. The juvenile component is probably a combination of material derived from the mantle and from anatexis of the surrounding juvenile terranes. Crustal anatexis may have occurred as a result of the intrusion of mafic melts related to subduction along the outboard margin of the Alexander–Wrangellia terrane, by crustal thickening due to the underthrusting of the Alexander–Wrangellia terrane beneath the Yukon–Tanana and Stikine terranes, or by a combination of both processes.

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Lu-Hf analyses of zircon from the Makoppa Dome and Amalia-Kraaipan area: implications for evolution of the Kimberley and Pietersburg blocks of the Kaapvaal Craton

South African Journal of Geology ◽

10.25131/sajg.123.0025 ◽

2020 ◽

Vol 123 (3) ◽

pp. 369-380

Author(s):

M.A. Elburg ◽

M. Poujol

Keyword(s):

Tectonic Evolution ◽

Far East ◽

Crustal Material ◽

Crust Formation ◽

The Far East ◽

Depleted Mantle ◽

Geological Evolution ◽

Crustal Reworking ◽

Greenstone Belts ◽

Age Range

Abstract Previously dated zircon crystals from the Amalia-Kraaipan granite-greenstone belts and Makoppa Dome were analysed for their Lu-Hf isotopic characteristics to refine the geological evolution of these areas. Samples from the Makoppa Dome, belonging to the Pietersburg Block, largely fall within the epsilon Hf-age range for granitoids from the eastern part of the block. However, the oldest 3.01 to 3.03 Ga trondhjemitic gneisses show that reworking of juvenile mafic crust started earlier in the western than the eastern part of the block, suggesting a diachronous tectonic evolution. The three granitoids from the Amalia-Kraaipan area fall within the field for Pietersburg and Kimberley block granitoids. Contribution from older crustal material is seen in a 3.08 Ga schist, likely derived from a volcanic protolith, from the Madibe Belt, in the far east of the Kimberley Block, with a mantle extraction age of 3.25 to 3.45 Ga. The data suggest that the Kimberley Block, like the Pietersburg Block, also contains (minor) ancient crustal components, derived from a depleted mantle source prior to 3.1 Ga. The new data suggest that the Kimberley and Pietersburg blocks underwent a very similar Paleo- to Mesoarchean crustal evolution, with a major crust formation event at 3.1 to 3.0 Ga followed by successive crust reworking until 2.77 Ga. Lavas of the Ventersdorp Supergroup, for which zircon grains from a ca. 2.75 lapilli tuff give εHfi of +2, are the first evidence of a juvenile source, after 300 Myr of crustal reworking.

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Gondwanan Eoarchean–Neoproterozoic ancient crustal material in Iran and Turkey: zircon U–Pb–Hf isotopic evidence

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2013-0138 ◽

2014 ◽

Vol 51 (3) ◽

pp. 272-285 ◽

Cited By ~ 47

Author(s):

Allen P. Nutman ◽

Mohammad Mohajjel ◽

Vickie C. Bennett ◽

Chris L. Fergusson

Keyword(s):

Northeast India ◽

Granitic Rocks ◽

Magmatic Zircon ◽

Crustal Material ◽

Isotopic Data ◽

Crystalline Complex ◽

Crustal Component ◽

Menderes Massif ◽

Sanandaj Sirjan Zone ◽

Archean Crust

The Sanandaj–Sirjan Zone is a basement culmination northeast of the Neo-Tethys suture in Iran. In this zone near Azna, granite has a magmatic zircon U–Pb age of 568 ± 11 Ma, with 900–800, ca. 2400, and ca. 3600 Ma inherited cores. The ca. 3600 Ma inherited zircon is the oldest crustal component yet detected in Iran. Near Chadegan, orthogneiss has a magmatic zircon U–Pb age of 637 ± 15 Ma, and carries ca. 1000 and 2000 Ma inherited zircons. Inherited 900–1000 Ma zircons have juvenile initial εHf values of ca. +8 to +9, whereas the younger 630 and 568 Ma magmatic zircons show lower initial εHf values; however, the 3600 Ma core has initial εHf = 0.0. A Neoproterozoic rim on the inherited 3600 Ma core has the most extreme initial εHf value of −18. The Hf isotopic data indicates generation of the magmatic protoliths from a mixture of juvenile Neoproterozoic and Archean sources. Previous studies showed that in Turkey the Central Anatolian Crystalline Complex is underlain by Neo-Eoarchean rocks, the Menderes Massif contains Neoproterozoic granitoids, and that central Iran’s basement and the northern Sanandaj–Sirjan Zone contain Neoproterozoic granitic rocks. This basement terrane is from Gondwana, and was transferred across Paleo-Tethys to dock against Eurasia’s southern margin. Occurrence in Iran and Turkey of Eoarchean crust raises the possibility of sinistral migration of this terrane in the closure of Tethys because the nearest known early Archean crust occurs in northeast India.

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Neodymium–strontium–lead isotopic study of Vancouver Island igneous rocks

Canadian Journal of Earth Sciences ◽

10.1139/e91-156 ◽

1991 ◽

Vol 28 (11) ◽

pp. 1744-1752 ◽

Cited By ~ 17

Author(s):

A. Andrew ◽

R. L. Armstrong ◽

D. Runkle

Keyword(s):

Mantle Source ◽

Large Scale ◽

Crustal Contamination ◽

Vancouver Island ◽

Isotopic Signature ◽

Late Eocene ◽

Crustal Material ◽

Isotopic Data ◽

Isotopic Study ◽

Depleted Mantle

Combined neodymium, strontium, and lead isotope measurements show that Vancouver Island is made up of Phanerozoic crustal material accreted to North America in the Mesozoic and early Cenozoic, but that there are differences in the relative proportions of depleted mantle and aged, enriched crustal components in the Phanerozoic magmatic episodes that contribute to this new crust.The Devonian Sicker Group volcanic arc has an isotopic signature that can be explained by mixing mantle material with subducted continentally derived sediments. The Early to Middle Jurassic Bonanza Volcanics and Island Intrusions magmatic arc isotopic signature indicates mixing of magma from a depleted mantle source with crustal material of Sicker arc-type, rather than of continental origin. This is consistent with large-scale assimilation of Sicker Group and Karmutsen rocks by Jurassic mantle-derived magmas, or introduction of arc-derived sediments into the Jurassic mantle by subduction. Eocene calc-alkaline Flores Volcanics – Catface Intrusions may be derived from reworked Vancouver Island crust with little addition of mantle material.Late Triassic Karmutsen Formation flood basalts are similar to the lower parts of the Columbia River Basalt in all three isotope systems and in petrochemistry. Radiogenic isotopic data are consistent with the interpretation that the Karmutsen basalts were extruded in a post-arc or back-arc setting, with mantle lithosphere and depleted mantle components, and perhaps some plume source input and crustal contamination, but the latter are not provable from the radiogenic isotopic data alone.Early Eocene Metchosin basalts show a depleted mantle source, consistent with their origin as ocean islands, before Middle to Late Eocene accretion to the rest of Vancouver Island.

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Rheological Contrast between Quartz and Coesite Generates Strain Localization in Deeply Subducted Continental Crust

Minerals ◽

10.3390/min11080842 ◽

2021 ◽

Vol 11 (8) ◽

pp. 842

Author(s):

Kouhei Asano ◽

Katsuyoshi Michibayashi ◽

Tomohiro Takebayashi

Keyword(s):

Rheological Behavior ◽

Strain Localization ◽

Shear Zones ◽

Ultrahigh Pressure ◽

Ultramafic Rocks ◽

Crustal Material ◽

Orientation Data ◽

Crystallographic Preferred Orientation ◽

Dabie Shan ◽

Felsic Rocks

Deformation microstructures of peak metamorphic conditions in ultrahigh-pressure (UHP) metamorphic rocks constrain the rheological behavior of deeply subducted crustal material within a subduction channel. However, studies of such rocks are limited by the overprinting effects of retrograde metamorphism during exhumation. Here, we present the deformation microstructures and crystallographic-preferred orientation data of minerals in UHP rocks from the Dabie–Shan to study the rheological behavior of deeply subducted continental material under UHP conditions. The studied samples preserve deformation microstructures that formed under UHP conditions and can be distinguished into two types: high-strain mafic–ultramafic samples (eclogite and garnet-clinopyroxenite) and low-strain felsic samples (jadeite quartzite). This distinction suggests that felsic rocks are less strained than mafic–ultramafic rocks under UHP conditions. We argue that the phase transition from quartz to coesite in the felsic rocks may explain the microstructural differences between the studied mafic–ultramafic and felsic rock samples. The presence of coesite, which has a higher strength than quartz, may result in an increase in the bulk strength of felsic rocks, leading to strain localization in nearby mafic–ultramafic rocks. The formation of shear zones associated with strain localization under HP/UHP conditions can induce the detachment of subducted crustal material from subducting lithosphere, which is a prerequisite for the exhumation of UHP rocks. These findings suggest that coesite has an important influence on the rheological behavior of crustal material that is subducted to coesite-stable depths.

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Nd isotopic characteristics of metamorphic and plutonic rocks of the Coast Mountains near Prince Rupert, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e98-007 ◽

1998 ◽

Vol 35 (5) ◽

pp. 556-561 ◽

Cited By ~ 13

Author(s):

P J Patchett ◽

G E Gehrels ◽

C E Isachsen

Keyword(s):

British Columbia ◽

Volcanic Rocks ◽

Metamorphic Rocks ◽

Published Data ◽

Isotopic Data ◽

Crustal Component ◽

Coast Mountains ◽

Crustal Rocks ◽

Metasedimentary Rocks ◽

Plutonic Rocks

Nd isotopic data are presented for a suite of metamorphic and plutonic rocks from a traverse across the Coast Mountains between Terrace and Prince Rupert, British Columbia, and for three contrasting batholiths in the Omineca Belt of southern Yukon. A presumed metamorphic equivalent of Jurassic volcanic rocks of the Stikine terrane gives epsilon Nd = +6, and a number of other metaigneous and metasedimentary rocks in the core of the Coast Mountains give epsilon Nd values from +3 to +7. A single metasedimentary rock approximately 3 km east of the Work Channel shear zone gives a epsilon Nd value of -9. Coast Belt plutons in the traverse yield epsilon Nd from -1 to +2. The Omineca Belt plutons give epsilon Nd from -10 to -17. All results are consistent with published data in demonstrating that (i) juvenile origins for both igneous and metamorphic rocks are common in the Coast Belt; (ii) representatives of a continental-margin sedimentary sequence with Precambrian crustal Nd are tectonically interleaved in the Coast Mountains; (iii) Coast Mountains plutons can be interpreted as derived from a blend of metamorphic rocks like those seen at the surface, or as arc-type melts contaminated with the older crustal component; and (iv) Omineca Belt plutons are dominated by remelted Precambrian crustal rocks.

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Nd-Hf isotope geochemistry and lithogeochemistry of the Rambler Rhyolite, Ming VMS deposit, Baie Verte Peninsula, Newfoundland: evidence for slab melting and implications for VMS localization

10.4095/328988 ◽

2021 ◽

Author(s):

S J Piercey ◽

J -L Pilote

Keyword(s):

Rare Earth ◽

Trace Element ◽

Isotope Geochemistry ◽

Primitive Mantle ◽

Isotopic Data ◽

Depleted Mantle ◽

Element Enrichment ◽

Felsic Volcanic ◽

Magmatic History ◽

Felsic Rocks

New high precision lithogeochemistry and Nd and Hf isotopic data were collected on felsic rocks of the Rambler Rhyolite formation from the Ming volcanogenic massive sulphide (VMS) deposit, Baie Verte Peninsula, Newfoundland. The Rambler Rhyolite formation consists of intermediate to felsic volcanic and volcaniclastic rocks with U-shaped primitive mantle normalized trace element patterns with negative Nb anomalies, light rare earth element-enrichment (high La/Sm), and distinctively positive Zr and Hf anomalies relative to surrounding middle rare earth elements (high Zr-Hf/Sm). The Rambler Rhyolite samples have epsilon-Ndt = -2.5 to -1.1 and epsilon-Hft = +3.6 to +6.6; depleted mantle model ages are TDM(Nd) = 1.3-1.5 Ga and TDM(Hf) = 0.9-1.1Ga. The decoupling of the Nd and Hf isotopic data is reflected in epsilon-Hft isotopic data that lies above the mantle array in epsilon-Ndt -epsilon-Hft space with positive ?epsilon-Hft values (+2.3 to +6.2). These Hf-Nd isotopic attributes, and high Zr-Hf/Sm and U-shaped trace element patterns, are consistent with these rocks having formed as slab melts, consistent with previous studies. The association of these slab melt rocks with Au-bearing VMS mineralization, and their FI-FII trace element signatures that are similar to rhyolites in Au-rich VMS deposits in other belts (e.g., Abitibi), suggests that assuming that FI-FII felsic rocks are less prospective is invalid and highlights the importance of having an integrated, full understanding of the tectono-magmatic history of a given belt before assigning whether or not it is prospective for VMS mineralization.

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Fluids composition in the mantle beneath the Eastern Transylvanian Basin inferred from mineral chemistry and noble gases in fluid inclusions of ultramafic xenoliths

10.5194/egusphere-egu21-9473 ◽

2021 ◽

Author(s):

Andrea Luca Rizzo ◽

Barbara Faccini ◽

Costanza Bonadiman ◽

Theodoros Ntaflos ◽

Ioan Seghedi ◽

...

Keyword(s):

Fluid Inclusions ◽

Noble Gases ◽

Mineral Chemistry ◽

Mantle Xenoliths ◽

Alkaline Magmatism ◽

Volcanic Area ◽

Crustal Material ◽

Calc Alkaline ◽

Depleted Mantle ◽

Magmatic Gases

The investigation of noble gases (He, Ne, Ar) and CO2 in fluid inclusions (FI) of mantle-derived rocks from the Sub Continental Lithospheric Mantle (SCLM) is crucial for constraining its geochemical features and evolution as well as the volatiles cycle, and for better evaluating the information arising from the study and monitoring of volcanic and geothermal gases. Eastern Transylvanian Basin in Romania is one of the places in Central-Eastern Europe where mantle xenoliths are brought to the surface by alkaline magmatism, offering the opportunity for applying the above-mentioned approach. Moreover, this locality is one of the few places on Earth where alkaline eruptions occurred contemporaneously with calc-alkaline activity, thus being a promising area for the investigation of subduction influence on the magma sources and volatiles composition.In this work, we studied petrography, mineral chemistry and noble gases in FI of mantle xenoliths found in Per&#351;ani Mts. alkaline volcanic products. Our findings reveal that the local mantle recorded two main events. The first was a pervasive, complete re-fertilization of a previously depleted mantle by a calc-alkaline subduction-related melt, causing the formation of very fertile, amphibole-bearing lithotypes. Fluids involved in this process and trapped in olivine, opx and cpx, show 4He/40Ar* ratios up to 1.2 and among the most radiogenic 3He/4He values of the European mantle (5.8 &#177; 0.2 Ra), reflecting the recycling of crustal material in the local lithosphere. The second event is related to a later interaction with an alkaline metasomatic agent similar to the host basalts, that caused slight LREE enrichment in pyroxenes and crystallization of disseminated amphiboles, with FI showing 4He/40Ar* and 3He/4He values up to 2.5 and 6.6 Ra, respectively, more typical of magmatic fluids.Although volcanic activity in the Per&#351;ani Mts. is now extinct, strong CO2 degassing (8.7 &#215; 103 t/y) in the neighbouring Ciomadul volcanic area may indicate that magma is still present at depth (Kis et al., 2017; Laumonier et al., 2019). The gas manifestations present from Ciomadul area are the closest to the outcrops containing mantle xenoliths for comparison of the noble gas composition in FI. 3He/4He values from Stinky Cave (Puturosul), Dobo&#351;eni and Balvanyos are up to 3.2, 4.4 and 4.5 Ra, respectively, indicating the presence of a cooling magma (Vaselli et al., 2002 and references therein). In the same area and more recently, Kis et al. (2019) measured 3He/4He ratios up to 3.1 Ra, arguing that these values indicate a mantle lithosphere strongly contaminated by subduction-related fluids and post-metasomatic ingrowth of radiogenic 4He. Our findings consider more likely that magmatic gases from Ciomadul volcano are not representative of the local mantle but are being released from a cooling and aging magma that resides within the crust. Alternatively, crustal fluids contaminate magmatic gases while they are rising to the surface.&#160;Kis et al. (2017). Journal of Volcanology and Geothermal Research 341, 119&#8211;130.Kis et al. (2019) Geochem. Geophys. Geosyst. 20, 3019-3043.Laumonier et al. (2019) Earth and Planetary Science Letters, 521, 79-90.Vaselli et al. (2002) Chemical Geology 182, 637&#8211;654.

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