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Mass‐dependent Mo isotope variations are a promising new tracer to study magmatic processes in different geological settings. We report the first Mo isotope data for the Kamchatka arc system in the Northwest Pacific, comprising basaltic lavas of a complete Southeast‐Northwest traverse from the volcanic arc front through to the back arc region. The majority of volcanic centers investigated directly override the Hawaii‐Emperor Seamount Chain, which is currently being subducted underneath the arc system. Our Mo isotope data show systematic trends with Ce/Pb, Ce/Mo, Nb/Zr, La/Sm, and 143 Nd/ 144 Nd ratios from the volcanic arc front to the back arc. Arc front lavas have higher δ 98/95 Mo and lower Ce/Pb, Ce/Mo, Nb/Zr, La/Sm compared to back arc lavas. Because the involvement of subducted sediments can be excluded, we attribute the observed variations to a change in the mantle source composition from the arc front to the back arc regions. The isotopic and chemical budget of arc front lavas is dominated by a slab fluid component (high δ 98/95 Mo, low Ce/Pb, Ce/Mo), whereas mantle‐like Ce/Pb, Ce/Mo, elevated Nb/Zr and La/Sm in the back arc samples suggest an enriched mantle source. Combined δ 98/95 Mo, Nd, and Pb isotope data in back arc lavas are very similar to those observed for modern ocean island basalts from Hawaii. We thus explore the possibility that the back arc mantle was contaminated by a Hawaii‐type, enriched asthenospheric mantle component from the subducted Hawaii‐Emperor Seamount Chain. In subduction zones, tectonic plates—tens of kilometers thick and making up the outer shell of our planet—are on a collision course. Although the absolute convergence rates of these plates are minute (a few cm/year), the forces in this process are so large that one plate is pushed under the other, causing the lower plate to be recycled into the Earth's mantle over time scales of millions of years. The tangible consequences are high‐magnitude earthquakes and large‐volume volcanic eruptions along these convergent plate margins. It is thus important to better understand the geological processes that operate in subduction zones. Here, we have studied the chemical and isotopic composition of volcanic rocks from the Kamchatka subduction zone. Our results confirm that water, locked into the subducting plate while residing on the surface, is released into the hot, overlying mantle after subduction, causing the formation of large volumes of magma that eventually erupt in volcanoes on the Kamchatka Peninsula. Our data also indicate that the subducting plate, once pushed into the mantle, is being ripped apart, allowing buoyant mantle material from greater depth to rise and contribute to the large‐scale volcanism observed along this convergent plate margin. Molybdenum isotope systematics in arc basalts from Kamchatka are consistent with presence of a slab‐derived fluid in their mantle source Back arc basalts also show contribution from a geochemically enriched source Combined Mo, Nd, and Pb isotope and trace element data for back arc basalts suggest involvement of Hawaii‐type asthenospheric mantle

We report on the occurrence of a new high-pressure Ca-Al-silicate in localized shock melt pockets found in the feldspatic lunar meteorite Oued Awlitis 001 and discuss the implications of our discovery. The new mineral crystallized as tiny, micrometer-sized, acicular grains in shock melt pockets of roughly anorthitic bulk composition. Transmission electron microscopy based three-dimensional electron diffraction (3D ED) reveals that the CaAl Si crystals are identical to the calcium aluminum silicate (CAS) phase first reported from static pressure experiments. The new mineral has a hexagonal structure, with a space group of and lattice parameters of = 5.42(1) Å; = 12.70(3) Å; = 323(4) Å ; = 2. This is the first time 3D ED was applied to structure determination of an extraterrestrial mineral. The International Mineralogical Association (IMA) has approved this naturally formed CAS phase as the new mineral “donwilhelmsite” [CaAl Si ], honoring the U. S. lunar geologist Don E. Wilhelms. On the Moon, donwilhelmsite can form from the primordial feldspathic crust during impact cratering events. In the feldspatic lunar meteorite Oued Awlitis 001, needles of donwilhelmsite crystallized in ~200 mm sized shock melt pockets of anorthositic-like chemical composition. These melt pockets quenched within milliseconds during declining shock pressures. Shock melt pockets in meteorites serve as natural crucibles mimicking the conditions expected in the Earth’s mantle. Donwilhelmsite forms in the Earth’s mantle during deep recycling of aluminous crustal materials, and is a key host for Al and Ca of subducted sediments in most of the transition zone and the uppermost lower mantle (460–700 km). Donwilhelmsite bridges the gap between kyanite and the Ca-component of clinopyroxene at low pressures and the Al-rich Ca-ferrite phase and Ca-perovskite at high-pressures. In ascending buoyant mantle plumes, at about 460 km depth, donwilhelmsite is expected to break down into minerals such as garnet, kyanite, and clinopyroxene. This process may trigger minor partial melting, releasing a range of incompatible minor and trace elements and contributing to the enriched mantle (EM1 and EM2) components associated with subducted sedimentary lithologies.

The gold-rich Ketté formations belong to the Adamawa-Yadé block of the Neoproterozoic Central Africa Orogenic Belt. They consist of a complex association of tonalite, granodiorite, and heterogeneous granite including rafts of metapyroxenite, amphibolite, paragneiss and migmatite. Metapyroxenite and amphibolite are metaluminous (A/CNK: 0.65–0.95), calc-alkaline, enriched in LILE and LREE, with εNd 610 < 0 and T DM ages of 1.7 Ga, highlighting their enriched mantle source. Paragneiss are rich in LREE, Cr, V, Sc and Ni and display A/CNK (1.06–1.08) and A/NK (1.5–3.49) ratios consistent with a sedimentary protolith made of poorly sorted greywackes and litharenites with a contribution from mafic rocks of the juvenile crust. Granitoids display a variety of signatures, ranging from metaluminous to peraluminous (A/CNK: 0.94–1.04), calc-alkaline to alkaline. The heterogeneous granite in diffuse contact with migmatite have εNd 654 values of –9.61 and –8.11, and are interpreted to reflect local magma collection within the zone of dominant partial melting of the paragneiss. The tonalite and granodiorite, characterized by magmatic textures, display Mg# of 39.9–48.8, low HFSE contents, and enrichment in LILE and LREE. They were likely formed by the fractional crystallisation of a dioritic magma derived from the partial melting of amphibolite. The main structure of the migmatite is a shallow- to moderately dipping NE–SW trending syn-migmatitic foliation S mgm , marked by alternating leucosome and mesosome layers, with relics of an S 0 /S 1 foliation locally preserved within the mesosome. Granulite-facies relics with a peak at 8–10 kbar/≥800 °C are preserved in metapyroxenite. Networks of texturally continuous leucosome veins concordant to discordant to the syn-migmatitic foliation, localization of granitic veins in shear zones and fold axial planes, attest for deformation in the presence of melt. Granitoids form kilometre-scale plutons with gently dipping magmatic fabrics (S m -S m /C 2 ) concordant to the syn-migmatitic foliation. These fabrics are transposed into a steeply dipping (47°–74°) E–W to NW–SE trending mylonitic fabric (S myl -S 3 /C 3 ), bearing a moderately plunging (15°–49°) stretching lineation L 3 , marking the folded Mama Shear Zone (MaSZ). These data indicate that the Ketté region has recorded magmatic accretion of a mafic crust originating from an enriched mantle source. This crust and its associated sediments were subsequently tectonically thickened during the Pan-African orogeny and affected by partial melting. Migration of dioritic to granitic magmas from the partially molten orogenic root led to syntectonic crustal differentiation. Les formations aurifères de Ketté, dans le bloc Adamawa-Yadé de la Ceinture Orogénique d'Afrique Centrale, sont constituées d'une association complexe de tonalite, granodiorite et granites hétérogènes, renfermant des enclaves de metapyroxénite, d'amphibolite, de paragneiss et de migmatite. Les metapyroxénites et amphibolites sont métalumineuses, enrichies en LILE et LREE, avec des valeurs εNd 610 < 0 et des âges modèles T DM de 1.7 Ga, indiquant une source mantellique enrichie. Les paragneiss sont riches en LREE, Cr, Sc et Ni et présentent des rapports A/CNK et A/NK caractéristiques de protolithes riches en greywackes et litharénites, avec une contribution de roches mafiques issues de la croûte juvénile. Les granitoïdes ont des signatures métalumineuses à peralumineuses, calco-alcalines à alcalines. Les granites hétérogènes présentent des contacts diffus avec les migmatites, des valeurs εNd 654 de −9.61 et −8.11, et reflètent une accumulation locale de magma au sein de zones de fusion partielle dominante des paragneiss. Les tonalites et granodiorites présentent des textures magmatiques, des valeurs Mg# de 39.9–48.8, de faibles teneurs en HFSE et des enrichissements en LILE et LREE. Elles résulteraient de la cristallisation fractionnée d'un magma dioritique issu de la fusion partielle des amphibolites. Les migmatites présentent une foliation syn-migmatitique S mgm orientée NE-SW, à pendage faible à modéré, marquée par l'alternance leucosomes-mésosomes, avec des reliques de la foliation S 0 /S 1 localement préservées. Des reliques du faciès granulitique témoin d'un pic métamorphique à 8–10 kbar/≥800 °C sont conservées dans les metapyroxénites. Les réseaux continus de leucosome, concordants à discordants à la foliation syn-migmatitique, ainsi que la localisation des veines granitiques dans des zones de cisaillement et dans les axes des plis, témoignent d'une déformation en présence de magma. Les plutons kilométriques de granitoïdes présentent des fabriques magmatiques (S m -S m /C 2 ) à faible pendage, concordantes avec la foliation syn-migmatitique. Ces fabriques sont transposées en des fabriques mylonitiques (S myl -S 3 /C 3 ) orientées E-W à NW-SE à fort pendage (47°–74°), portant une linéation d'étirement Le 3 à plongement modéré (15°–49°), dans la zone de cisaillement plissée de Mama. Ces données indiquent que le socle de Ketté a enregistré l'accrétion d'une croute mafique dérivée de la fusion du manteau enrichi. Cette croûte et les sédiments y associés ont ensuite été tectoniquement épaissis durant l'orogénèse Pan-Africaine, favorisant la fusion partielle. La migration de magmas de composition dioritique à granitique issus de la racine orogénique partiellement fondue a conduit à une différenciation crustale syntectonique.

Cratonic lamproites bear extreme Sr−Nd−Pb isotopic compositions widely known as enriched mantle I (EMI), yet the origin of the EMI reservoir remains controversial. Here, we explore this issue by examining Mg−Sr−Nd−Pb isotopic compositions of lamproites from Leucite Hills, Wyoming, USA. The δ26Mg values vary from the range of the normal mantle to lower values (− 0.43 to − 0.18 ‰), correlating with indices of the degree of carbonate metasomatism, an observation that can be best explained through mantle metasomatism by subducted carbonate-bearing sediments. With increasing extent of carbonate metasomatism, these samples display less extreme EMI Sr−Nd−Pb isotopic signatures, arguing for at least two metasomatic events that occurred in their mantle sources. The early metasomatic event associated with subducted continent-derived siliciclastic sediments led to the formation of the EMI Sr−Nd−Pb isotopic signatures while the recent carbonate metasomatism produced the light Mg isotopic signature but diluted the EMI Sr−Nd−Pb isotopic signatures. Our study indicates that a combination of Mg and Sr−Nd−Pb isotopes could be an effective tool in deciphering multiple-stage metasomatic events in mantle sources and places new constraints on the generation of enriched mantle reservoirs.

The Longshan orogenic belt is located in the southwestern margin of Ordos Basin at the junction zone between the Western Qinling and Northern Qilian orogenic belt. Voluminous Early Paleozoic magmatism in this area is of key significance for determining the Early Paleozoic tectonic evolution and deep crust-mantle structure. Previous studies mainly focused on the Paleozoic granites; the coeval mafic rocks in this area are still poorly understood. A set of Late Silurian intraplate tholeiitic basalts has been discovered in Longshan area, providing key evidence for the mantle source and deep geodynamic background in this area. The Late Silurian Angou basalt has similar geochemical features as intraplate tholeiitic basalt, with high Na 2 O/K 2 O ratios (5.22–8.25), enriched in large ion lithophile elements and LREE. In combination with their relatively evolved Sr-Nd isotopic composition [ 87 Sr/ 86 Sr (i) = 0.7128–0.7140; ε Nd (t) =  − 5.55 to − 3.40], it is suggested that it originated from decompression melting of metasomatized enriched mantle in extensional setting. These results indicate that the mantle source in the junction zone of the West Qinling-North Qilian orogenic belt evolved from depleted to enriched with the continuation of Proto-Tethys subduction from the Cambrian to the Silurian. These results are of great significance to understanding the genesis of contemporaneous granite and the crust-mantle interaction in the junction zone between the Western Qinling and Northern Qilian orogenic belt.

Post-collisional (23–8 Ma), potassium-rich (including ultrapotassic and potassic) mafic magmatic rocks occur within the north–south-trending Xuruco lake–Dangre Yongcuo lake (XDY) rift in the Lhasa terrane of the southern Tibetan Plateau, forming an approximately 130-km-long semi-continuous magmatic belt. They include both extrusive and intrusive facies. Major and trace element and Sr–Nd–Pb isotopic data are presented for all of the known exposures within the XDY rift. The potassium-rich, mafic igneous rocks are characterized by high MgO (5.9–10.8 wt.%), K 2 O (4.81–10.68 wt.%), Ba (1,782–5,618 ppm) and Th (81.3–327.4 ppm) contents, and relatively high SiO 2 (52.76–58.32 wt.%) and Al 2 O 3 (11.10–13.67 wt.%). Initial Sr isotopic compositions are extremely radiogenic (0.712600–0.736157), combined with low ( 206 Pb/ 204 Pb) i (18.28–18.96) and ( 143 Nd/ 144 Nd) i (0.511781–0.512046). Chondrite-normalized rare earth element patterns display relatively weak negative Eu anomalies. Primitive mantle-normalized incompatible trace element patterns exhibit strong enrichments in large ion lithophile elements relative to high-field-strength elements and display strongly negative Ta–Nb–Ti anomalies. The combined major and trace element and Sr–Nd–Pb isotopic characteristics of the K-rich igneous rocks suggest that the primitive magmas were produced by 1–10 % partial melting of an asthenospheric mantle source enriched by both fluids and partial melts derived from Indian passive continental margin sediments subducted into the shallow mantle as a consequence of the northward underthrusting of the Indian continental lithosphere beneath Tibet since the India–Asia collision at ~55 Ma. The best-fit model results indicate that a melt with trace element characteristics similar to those of the K-rich rocks could be generated by 8–10 % partial melting of a metasomatized mantle source in the south and 1–2 % melting in the north of the XDY rift. Trace element and Sr–Nd–Pb isotopic modeling indicate that the proportion of fluid derived from the subducted sediments, for which we use as a proxy the Higher Himalayan Crystalline Sequence (HHCS), in the mantle source region increases from north (rear-arc) to south (front-arc), ranging from 0 to 5 %, respectively. Correspondingly, the proportion of the melt derived from the subducted HHCS in the source increases from north (2 %) to south (15 %). The increasing proportion of the fluid and melt component in the mantle source from north to south, together with a southward decreasing trend in the age of the K-rich magmatism within the XDY rift, is inferred to reflect rollback of the subducted Indian lithospheric mantle slab during the period 25–8 Ma. Slab rollback may be linked to a decreasing convergence rate between India and Asia. As a consequence of slab rollback at 25 Ma beneath the Lhasa terrane, its geodynamic setting was transformed from a convergent (55–25 Ma) to an extensional (25–8 Ma) regime. The occurrence of K-rich magmatism during the period 25–8 Ma is a consequence of the decompression melting of an enriched mantle source, which may signal the onset of extension in the southern Tibetan Plateau and provide a petrological record of the extension process.

The Don terrane, which is extensively reworked by metamorphism and granitoid intrusions, is part of the Volga–Don orogen stretching along the eastern margin of the Sarmatian segment of the East European Craton. The terrane consists of gneiss-granites of the Pavlovsk complex, metavolcanic rocks, ranging from basaltic andesites to dacites (amphibolites and gneisses), and metasedimentary rocks (marbles and calc-silicate rocks) of the Don Group. The volcanic rocks are typically enriched in LILE and LREE and show negative HFSE anomalies, indicating fluid-assisted melting of the mantle wedge in a subduction zone. The Nd isotopic composition (ε Nd2200 = –1.2 to +3.4, model age 2180–2550 Ma) and Hf isotopic composition (ε Hf = –4.3 to +3.3, model age 2290–2640 Ma) indicate an enriched mantle or a mixed crustal–mantle source of the parental melts of the volcanics and a juvenile source for sediments of the Don Group. The U–Pb zircon metamorphic age of the gneisses and amphibolites is 2047 ± 7 Ma, and that of the thermal effect of the granitoid batholith on the host rocks is 2060 ± 4 Ma. According to isotope geochemical and geochronological data, the Don Group is underlain by Archean rocks, contains Archean detrital zircons, but the age of this group is no older than 2300 Ma. A facies and age analogue of the Don Group is the Temryuk Formation of the Central Azov Group of the Ukrainian shield. In the Paleoproterozoic, the eastern margin of Sarmatia was likely a continental arc, which was nearly coeval with the island arc–backarc basin system of the Losevo Group.

The late Miocene–Pliocene volcanic rocks from Todeshk, south-east of Isfahan, are located in the middle of the Urumieh–Dokhtar magmatic belt. The belt is considered the subduction-related magmatic arc. The late Miocene–Pliocene calc-alkaline volcanic rocks are mainly andesite and dacite. The rocks have been formed during the post-collisional stage of the Zagros orogen. Geochemical data show the enrichment of light rare-earth elements and large ion lithophile elements such as Cs, Rb, K, Pb, Ba and Th as well as the depletion of elements with high field strength such as Nb, Ta and Ti. The Pb–Sr–Nd isotopic ratios of the studied rocks are characterised by 206 Pb / 204 Pb = 18.41 –18.72; 207 Pb / 204 Pb = 15.64 –15.67; 208 Pb / 204 Pb = 38.49 –38.83; 207 Pb / 206 Pb = 0.8372 –0.8496; 208 Pb / 206 Pb = 2.0743 –2.0905; 87 Sr / 86 Sr = 0.7051 –0.7068 and 143 Nd / 144 Nd = 0.5125 . The rocks have Δ 7 / 4 Pb = 15.44 –15.82 and Δ 8 / 4 Pb = 57.26 –60.44. Based on petrological studies and the whole rock Pb, Sr and Nd isotopes data, the late Miocene–Pliocene calc-alkaline volcanic rocks have been generated from the partial melting of the subduction-related metasomatised mantle. Additionally, the slab-derived melts and fluids were recycled into the mantle source. The data demonstrate that terrigenous sediments accompanied by a subducted slab play an important role in the formation of the enriched mantle as the source of volcanic rocks.

The North China Craton (NCC) is one of the classic examples of decratonization through extensive lithospheric destruction during Mesozoic time. Among the various pulses of magmatism associated with cratonic erosion are the rare mafic intrusions in the Yanshan Belt. Here we investigate the Shangzhuang layered intrusion belonging to this suite, which is characterized by compositional layering with troctolite, noritic gabbro and gabbro/gabbroic anorthosite/gabbrodiorite from the bottom to top. The different lithologies of this intrusion exhibit close field relationships, similar chemical patterns and overall identical Lu–Hf isotopes indicating a co-magmatic nature. The fine-grained gabbros occurring near the margin of the intrusion display U–Pb ages similar to those of the other rocks and are considered to represent the composition of the parent magma, characterized by Fe, Mg and Ti enrichment. The magma was sourced from low-degree partial melting of spinel lherzolite sub-continental lithospheric mantle, which had been enriched by crust–mantle interaction and metasomatic fluids derived from the Mongolian oceanic slab subduction beneath the NCC during Late Palaeozoic time. In addition, limited asthenospheric or deeper-mantle materials were also locally mixed with the enriched mantle as the final source component. Our zircon U–Pb data constrain the emplacement age of this intrusion as c. 128–123 Ma in Early Cretaceous time, and correlates with the regional extensional tectonics between c. 135 and 115 Ma in the eastern and central NCC. Mantle upwelling associated with this event resulted in the thermal and chemical erosion of the lithospheric mantle, and emplacement of the parent magma of this layered intrusion.

The Qinling–Dabie orogen in central China is one of the major orogenic belts in East Asia. In the eastern Dabie–Sulu region, mafic lamprophyres show the enriched signatures of old sub-continental lithospheric mantle. However, little is known about the mafic igneous rocks and their lithospheric mantle sources in the western Qinling Range. New 40Ar–39Ar age dating, major- and trace-element data, and isotopic analyses of Qinling lamprophyres reveal their differences from the Dabie Sulu lamprophyres. Biotite 40Ar–39Ar dating yielded a plateau age of 219±2 Ma, identical to the ages of rapakivi-textured granitoids in the area. The association of lamprophyre dykes and rapakivi-textured granitoids indicates that the Qinling region was a post-collisional setting at c. 220 Ma. The Qinling lamprophyres are calc-alkaline, and rich in large ion lithophile elements (e.g. Ba, K), but depleted in Nb, Ta and Ti. They show highly fractionated REE patterns with LaN>100 and HREE <10 times chondrite abundances. εNd (219 Ma) values range from −0.5 to −3.3 and initial Sr isotope values from 0.7036 to 0.7058. These features suggest generation of the lamprophyre by partial melting of a metasomatized, garnet peridotite mantle source. The Qinling lamprophyres are distinct from the Dabie–Sulu lamprophyres in emplacement age (c. 135 Ma for Dabie–Sulu) and isotopic composition, suggesting that the nature of the lithospheric mantle and geodynamic evolution of the Qinling region contrasts with that of the Dabie–Sulu region.