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Late-magmatic granitic fluids are typically enriched in Si, K and rare lithophile elements, including Be, Li, Sn, W, Rb, Cs, Nb, Ta, REE and U, and are also characterised by volatile components such as OH, F and B. Consequently the resultant pegmatite bodies are very coarse-grained and contain accessory minerals with unusual mineral chemistries. Pegmatites, usually present as veins, can occur as emanations from granite bodies or be produced by granite fronts generated by migmatisation during high-grade metamorphism. The former process is represented in the sites by Loch Avon; located within the Main Granite of the Cairngorms, this is the area where large topaz crystals, renowned for their blue colour, are found along with cairngorm and citrine varieties of quartz. Rare beryllium minerals, genthelvite and bertrandite, also occur. The latter process was responsible for the generation of the South Harris and Loch Nevis pegmatite suites which collectively encompass a range of mineral assemblages as follows. The Chaipaval Pegmatite site, some 2 km long, and previously worked for potassium feldspar, contains an unusual suite of uranium-bearing minerals together with spessartine, columbite and gahnite. By contrast the Sletteval Pegmatite site, also previously worked, is more thorium-rich and again contains the rare mineral thorogummite. The more mafic biotite-magnetite-bearing Loch a’ Sgurr Pegmatite site presents an intimate association of uraninite with magnetite, monazite and feldspar. The mica pegmatites at the Loch Nevis site, which formed a series of concordant lenses and veins, were rich in extractable muscovite. Additionally garnet and minor beryl are present in some pegmatites.

The Tampanchi Ultramafic–Mafic Complex (TUMC), located in the central segment of the Cordillera Real (Ecuador), is an oval-shaped intrusive body of approximately 18 km2 emplaced within a Cretaceous metavolcano-sedimentary sequence. Field investigations, zircon geochronology, mineral and whole-rock elemental and isotopic compositions constrain the nature of the parental magma as well as the physical conditions of emplacement, age of crystallization and tectonic setting of formation of the TUMC. The Complex consist of wehrlite and olivine-hornblende clinopyroxenite crosscut by hornblende gabbros and minor dikes/veins of diorite and granite. Hornblendites formed mainly at the contact between the olivine-hornblende clinopyroxenite and the intrusive hornblende gabbros by reaction-replacement processes. Geochemical data for both the wehrlites and pyroxenites define a trend with dominantly olivine and clinopyroxene accumulation, whereas a second trend is formed by hornblende gabbros that differentiated to leucocratic rocks, with amphibole as the dominant fractionating mafic phase. The trace elements show enrichment in large-ion lithophile elements, depletion in high field strength elements (Nb, Zr, Ti) and P, and enrichment in Pb, Sr and Ba relative to primitive mantle, indicating subduction-related parental liquids. The Nd and Sr isotopic composition suggests a uniform mantle source metasomatized by subducted crustal components. Thermobarometric estimations constrain emplacement and crystallization at intermediate to shallow continental crust levels (∼12.5 km depth) of hydrated basaltic melt under oxygen fugacity conditions above the nickel-nickel oxide buffer (ΔNNO = 0 to 2). Zircon SHRIMP U-Th-Pb age data constrain crystallization at 75.1–76.0 Ma, with scarce inherited zircons that record limited recycling of the Cordillera Real basement. These results confirm magmatic arc activity at the continental margin of South America during the late Cretaceous as a result of an E-dipping subduction zone prior to the accretion of the Ecuadorian-Colombian-Caribbean oceanic plateau, and support simultaneous double subduction at the northwest margin of South America during the Cretaceous. This work was funded in the frame of the project “Proyecto Junior PIJ-16-04 (VIPS-EPN)” of the Escuela Politécnica Nacional to F. Villares. J.A.Proenza and A. Garcia-Casco appreciate financial support from Spanish MICINN project PID2019-105625RB-C21. This is the IBERSIMS publication N° 86.

The age and tectonic history of the chromite-mineralised Bacuri Complex, a layered mafic–ultramafic intrusion emplaced into Archean terranes of the Guyana Shield in the Amazonian Craton, are here investigated. The stratigraphy of the Bacuri Complex consists of an Ultramafic Zone composed of interlayered metaperidotites and chromitites and two mafic zones composed of metamafic rocks (amphibolites). In this study we present whole-rock lithogeochemical data integrated with zircon U-Pb isotopic and trace-element data from amphibolites from the Mafic Zone. The investigated amphibolites consist of hornblende + plagioclase ± diopside ± biotite with whole-rock compositions like noritic rocks of Archean layered intrusions. These samples are representative of amphibolites with variable proportions of hornblende and plagioclase, interpreted as resulting from amphibolite facies metamorphism of interlayered norite and leuconorite. We suggest that progressive fractionation of a primitive parental magma led to the formation of plagioclase and orthopyroxene cumulates in the mafic zones. We found that zircons from three metanorite samples comprise euhedral crystals with oscillatory zoning (interpreted to preserve a magmatic crystallisation age), as well as variably recrystallised metamorphic zircons. Their U-Pb 207Pb/206Pb ages span over 682 million years, from 3628 Ma to 2942 Ma. Trace element data suggest that magmatic zircons precipitated from late-stage magmatic fluids at ∼ 3.34 Ga (3343 ± 3.5 Ma weighted average age, n = 48, MSWD = 1.3), which defines the Bacuri Complex as one the oldest and best-preserved layered intrusions known. We show that fluid-mediated coupled dissolution-precipitation recrystallisation during metamorphism altered the composition and ages of magmatic zircons. We could not accurately define the number and age of metamorphic events in the 2942–3379 Ma age interval of metamorphic or ‘disturbed’ zircon domains. Our results indicate that continental crust was already established in the Amazonian craton in the Paleoarchean and possibly in the Eoarchean and that it has been reworked since at least the Mesoarchean.

In order to better constrain the Late Paleozoic tectonic evolution of the SW Central Asian Orogenic Belt, we conducted field structural investigations, zircon U-Pb dating, whole-rock geochemical and Sr-Nd isotopic studies on the meta-sedimentary rocks and intruding granites and mafic dykes in the Dahalajunshan area, southern Yili Block of NW China. Our results allow us to recognize five tectonic/magmatic events. Field-scale and microscopic structures of the low-grade meta-sedimentary rocks showed a regional top-to-the-SE thrusting (Event 1). Undeformed granites that contain dioritic enclaves (Event 2) crosscut the regional foliations and thus post-date Event 1 after ca. 379–369 Ma. Mafic dykes intruded all these rocks after ∼328 Ma (Event 4–1), posterior to brittle-ductile thrusting (N-S contraction) (Event 3) and prior to normal faulting (N-S extension) (Event 4–2). All the magmatic rocks formed in a subduction-related setting. The granites and dioritic enclaves derived from a mixing of crustal- and mantle-derived sources variously modified by slab-derived hydrous melts. The primary magma of the diabase dykes derived from a mantle source modified by the slab fluids with 5% crustal contamination. Variation from regional compression (ductile and brittle-ductile thrusting) to extension (normal faulting) and increasing mantle input in arc-related magmatism reveals a transition from Early Paleozoic advancing subduction (events 1 to 3) to Late Paleozoic retreating subduction (events 4–1 and 4–2) of the Junggar oceanic plate beneath the Yili Block.

The Variscan Central-Sudetic Ophiolites (CSO) are located in the Sudetes, the NE segment of the Bohemian Massif. The Devonian CSO display highly depleted, harzburgite mantle sections containing gabbroic dykes and local occurrences of mostly isotropic, large gabbroic bodies as well as volcanic rocks. The ultramafic rocks locally show melt percolation-derived clinopyroxene-olivine aggregates and chromitites. The low REE composition and depletion in LREE relative to HREE of the clinopyroxene as well as the chromite Cr# and Mg# values are typical for phases formed from refractory melts occurring in the supra-subduction zone environment. The gabbroic bodies consist of differently evolved, mostly cumulate rocks, while the volcanic rocks form a relatively monotonous basalt sequence. The trace element compositions of both the plutonic and volcanic rocks display depleted N-MORB affinities, their derivation from a refractory mantle source is further reflected by previously published depleted mantle-like Sr-Nd isotopic compositions. The ultramafic and mafic members of the CSO show greenschist- to lower amphibolite-facies metamorphic overprints. The occurrence of depleted harzburgites and isotropic gabbros forming the mantle and the crustal sections of the CSO, respectively, indicate intermediate- to slow-spreading conditions and a heterogeneous structure of the oceanic lithosphere, untypical for layered ophiolites. The geochemical characteristics of the melt-percolation phases of the ultramafic rocks, the bulk-rock compositions of the mafic rocks and the homogeneous volcanic sequences suggest a formation of the CSO in a mature back-arc basin setting, lacking subduction-derived contamination. Spreading rate conditions and geochemical affinities of the CSO are similar to those of other Devonian ophiolites localized along the Variscan Belt, for instance the Upper Ophiolitic Units in the NW Iberian Massif (Spain), thereby confirming the general absence of N-MORB type lithosphere in the European Variscan Orogen.

The Himalayan orogen, resulting from the Early Cenozoic collision of the Indian and Asian plates, is an ideal vehicle to study active orogenic processes and test geodynamic models of how the crust responds to collisional orogeny. This paper focused on migmatitic high-pressure (HP) mafic granulite and associated leucosome from the Greater Himalayan Crystallines (GHC) in the Eastern Himalayan Syntaxis (EHS) in order to understand the conditions and timescales over which high-grade rocks and partial melts were produced during the Himalayan orogeny. Combining with previous study results from the Western and Central Himalayas and Trans-Himalayan magmatic arc, we obtained the following conclusions: (1) The mafic granulites from the EHS underwent HP and high-temperature (HT) granulite facies metamorphism and partial melting, with peak metamorphic conditions of 15–17 kbar and 820–880 °C. The GHC, at least its western part of the EHS, underwent coherent HP granulite-facies metamorphism. (2) The HP mafic granulites experienced long-lived dehydration melting of amphibole from ~40 Ma to ~20 Ma during prograde metamorphism and generated up to ~16 vol% partial melt. The variable degrees of dehydration melting of the HP mafic, pelitic and felsic granulites in the EHS generated voluminous granitic melts with distinct compositions, and provided the source for the Himalayan granites. (3) Peak metamorphic pressure of the GHC gradually decreases, whereas the metamorphic temperature progressively increases from the Western to Eastern Himalayas. This indicates that the Indian continental crust deeply subducted into the mantle in the Western Himalaya after the Indo-Asia collision, whereas the Indian crust underthrusted or relaminated beneath the Asian continental crust, and formed the thickened lower crust in the Central and Eastern Himalayas and Gangdese arc. (4) The melts derived from the underthrusted Indian crust probably resulted in isotopic compositional enrichment of the Early Cenozoic mantle- and juvenile crust-derived magmatic rocks of the Gangdese arc.

The evolution of the Mozambique Ocean spans the Rodinia and Gondwana supercontinent cycles playing a key role in Earth history. Integrated petrological, geochronological, geochemical, and isotopic data on the Neoproterozoic units from the Lhasa terrane, Tibet, constrain the magmatic and metamorphic evolution of the ocean. Our results reveal two magmatic (ca. 695 Ma and ca. 671 Ma) and two metamorphic (ca. 700 Ma and ca. 650 Ma) pulses. Gabbros define the first magmatic suite. They have within-plate affinities and experienced crustal contamination. Their positive zircon eHf(t) (+1.6 to +9.6) and whole-rock eNd(t) (+2.7 to +6.1) values are indicative of a depleted mantle source. Gabbros from the second magmatic event belong to the tholeiitic series, lack evidence for crustal contamination, and are geochemically similar to E-MORB. They have negative to positive zircon eHf(t) (−3.2 to +1.5) and low positive whole-rock eNd(t) (+1.4 to +2.0) values, and were probably derived from an E-MORB-type enriched mantle source, slightly modified by subduction components. Evidence for the metamorphic events (ca. 700 and ca. 650 Ma) was obtained from U Pb dating of zircon rims of marbles and gabbros, which are characterized by low Th/U ratios (0.01–0.07) indicative of a metamorphic origin. Integrating previous studies with the data presented in this contribution, we suggest that the history of the Lhasa terrane was linked to the evolution of the Mozambique Ocean. The older mafic magmatism (ca. 695 Ma) and metamorphism (ca. 700 Ma) formed during terrane accretion processes along an active continental margin to the ocean. The relatively younger mafic magmatism (ca. 671 Ma) provides a record from an oceanic fragment that was metamorphosed (ca. 650 Ma) during closure of the Mozambique Ocean.

Collision-induced subduction transference may have triggered subduction of the Neo-Tethys oceanic lithosphere. To verify this proposition, we present an integrated geochemical and geochronological studies of new and published data of the Permian-Triassic magmatism in the Lhasa Terrane. The newly identified Chongni mafic intrusions (gabbros and diorites) in the North Lhasa Terrane (NLT) were emplaced during the Early Permian (ca. 275 Ma). The mafic rocks have (87Sr/86Sr)t ratios between 0.7037 and 0.7042, and eNd(t) values between + 5.2 and + 5.8. The zircons of the Chongni mafic rock samples have eHf(t) values from + 9.1 to + 12.9. The isotopic data in conjunction with trace element features suggest that the Chongni mafic intrusions have been derived mainly by partial melting of a metasomatized mantle wedge source. The newly identified Quxu granodiorites and hornblende gabbros in the South Lhasa Terrane (SLT) were emplaced in the Late Triassic (ca. 228–203 Ma). The granodiorites are characterized by (87Sr/86Sr)t ratios of 0.7036–0.7037 and eNd(t) values of +6.6 to +6.7, while the hornblende gabbro samples have (87Sr/86Sr)t ratios of 0.7033–0.7035 and eNd(t) values of +7.3 to +7.4. The zircons of the granodiorite and hornblende gabbro samples revealed eHf(t) values of +10.3 to +14.0 and +10.8 to +16.4, respectively. The isotopic data in combination with trace element signatures suggest that the granodiorites were derived from a juvenile basaltic lower crust with a minor input of mantle components, while the hornblende gabbros are interpreted to have formed during partial melting of a formerly metasomatized depleted mantle wedge source. The Early Permian and Late Triassic magmatic rocks consistently show arc-related signatures, which probably record the northward subduction of the Sumdo Paleo-Tethys and the Neo-Tethys oceanic slabs, respectively. This evidence, in combination with that of other studies on the Permian-Triassic magmatism across the Lhasa Terrane, indicates that arc magmatism within the NLT switched to collisional magmatism at ca. 260 Ma due to the collision of oceanic islands/plateaus and, further on, the collision of the SLT with the NLT. Furthermore, the change from ca. 265–255 Ma alkaline magmatism to ca. 240–200 Ma calc‐alkaline magmatism within the SLT may reflect the geodynamic transition from lithospheric extension to Andean-style orogenesis. Therefore, we propose that subduction initiation of the Neo-Tethys oceanic lithosphere in the Tibetan Plateau resulted from the southward transference of the Sumdo Paleo-Tethys subduction zone, involving the collision of oceanic islands/plateaus and, subsequently, the collision of the SLT with the NLT. Additionally, the geological records of the Tethyan orogenic system suggest that the subduction initiation of the Neo-Tethys oceanic lithosphere is a uniform response to the collision between Cimmeria and Eurasia.

The Gangdese arc in southern Tibet formed during subduction of the Neo-Tethyan ocean and is characterized by mantle-derived magma accretion and juvenile crustal growth. A main period of magmatism and juvenile crustal growth occurred during the Cretaceous, but little is known about the petrological component, nature, and evolution of the lower arc crust at that time. Here, we report systematic petrologic, geochemical and geochronologic data for amphibole-bearing anorthosite and diorite from the eastern Gangdese arc. The studied rocks occur within early Late Cretaceous gabbro or meta-gabbro, and consist mainly of plagioclase and amphibole with other hydrous phases, including minor muscovite, biotite and epidote. Zircon U–Pb dating gives Late Cretaceous crystallization ages of ca. 78 Ma. The rocks have varying SiO2 (47.44–57.35 wt%), Al2O3 (19.76–25.15 wt%), MgO (0.55–3.43 wt%) and FeOT (0.89–8.31 wt%) contents that can be explained as resulting from a primary melt with either plagioclase addition or amphibole accumulation. Trace element compositions show unusually high Sr/Y (59.3 to 948, average 278), but moderate (La/Yb)N (3.2 to 16.6, average 6.4). Isotopic compositions of Sr, Nd, and Hf (initial 87Sr/86Sr = 0.704186 – 0.704552, eNd(t) = +2.8 to + 4.6 and zircon eHf(t) = +10.2 to + 15.8) are comparable to the early Late Cretaceous gabbros that form the juvenile lower crust. These geochemical characteristics imply that the studied rocks were likely derived from hydrous anatexis of early Late Cretaceous juvenile lower crust. We suggest that shallow-angle subduction and dehydration of the Neo-Tethyan oceanic plate resulted in thickening and hydrous partial melting of juvenile lower crust to form water-rich anorthosite, diorite, and previously reported adakitic rocks during the Late Cretaceous. The juvenile lower crust of the Gangdese arc consisted of hydrous mafic granulites, and experienced distinct thickening and reworking during the Late Cretaceous.

Large igneous provinces (LIPs) are often used as a powerful tool for constraining continental reconstructions, due to their potential to correlate radiometric emplacement ages across scattered fragments of once continuous igneous bodies, and establish the presence of coeval magmatic suites. Mesoproterozoic magmatism in northern Australia and north China has been suggested to be the dispersed fragments of a once contiguous LIP. Here we present new geochronology and geochemical data from the under-resolved northern Australian fragments of this province (the Derim Derim and Galiwinku suites), and review existing data on related Mesoproterozoic mafic sills in the North Australian Craton and the North China Craton. We propose an updated framework for shared magmatic genesis and cratonic proximity during magmatic emplacement. Apatite geochronology has been applied to date dolerite intrusions, using cogenetic minerals to constrain the initial common-Pb constraints of the dolerite samples which provides a significant advantage for dating mafic rocks. The ages of samples collected throughout the extent of the mafic magmatic province in northern Australia and north China supports coincident ca. 1330–1295 Ma magmatism across both regions, while geochemical evidence indicates a mantle plume derived melt as the probable source for both suites. Coeval intrusion of geochemically analogous sills within temporally and stratigraphically comparable sedimentary basins is supportive of plume activity proximal to a once continuous sedimentary system that covered much of the North Australian Craton and North China Craton, which supports a close connection between the cratons within the supercontinent Nuna in the Mesoproterozoic.

Discovering ore deposits is becoming increasingly difficult, and this is particularly true in areas of glaciated terrains. As a potential exploration tool for such terrains, we test the vectoring capacities of trace element and sulfur isotope characteristics of pyrite, combined with quantitative statistical methods of whole-rock geochemical datasets. Our target is the Rajapalot gold–cobalt project in northern Finland, where metamorphosed Paleoproterozoic volcanic and sedimentary rocks of the Peräpohja belt host recently discovered gold prospects, which also have significant cobalt enrichment. The focus is particularly put on a single gold–cobalt prospect, known as Raja, an excellent example of this unusual cobalt-enriched gold deposit, common in the metamorphosed terranes of northern Finland. The major lithologies at Rajapalot comprise amphibolite facies metamorphosed and polydeformed calcsilicate rocks that alternate with albitic units, mafic volcanic rocks, mica schist and quartzite. Mineralization at Rajapalot prospects is characterized by an older Co-mineralizing event and a younger high-grade Au mineralization with re-mobilization and re-deposition of Co. Detailed in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful technique that produces robust trace element and sulfur isotope databases from paragenetically and texturally well-characterized pyrite from the Raja prospect. The results are treated with appropriate log-ratio transformations and used for multivariate statistical data analysis, such as the computation of principal components. Application of these methods revealed that elements such as Co, Ni, Cu, Au, As, Ag, Mo, Bi, Te, Se, Sn, U, Tl and W have high vectoring capacities to discriminate between Co-only and Au–Co zones, as well as between mineralization stages. The systematic pyrite study suggests that homogenous sulfur isotopic characteristics (+1.3 ‰ to +5.9 ‰) and positive loadings of Co, Se, As, Te, Bi and Au onto PC1 are reflective of an early stage of Co mineralization, while the opposing negative loadings of Mo, Ni, W, Tl, Cu and Ag along PC1 are associated with pyrites from the Au-mineralizing event. The sulfur isotopic signature of the latter pyrite type is between −1.2 ‰ and +7.4 ‰. Subtle patterns recognized from the whole-rock geochemistry favor an As–Au–Se–Te–W–U signature along the positive axis of PC1 for the localization of high-grade Au–Co zones, whereas the element group Ni, Cu, Co, Te, Se and As, which has negative loadings onto PC2, will predict Co-only zones. This study shows the efficiency of trace element geochemistry in mineral exploration targeting, which has the capacity to define future targets by characterizing the metallogenic potential of a host rock, as well as distinguishing various stages of mineralization.

The Qilian orogen consists of the North Qilian belt, the Central Qilian block and the South Qilian belt and is regarded as part of the northern margin of the Proto-Tethys Ocean. The tectonic mechanism responsible for the early Paleozoic magma generation in the Qilian orogen is crucial to understanding the ocean-continent configurations and the closure of the Proto-Tethys Ocean. This paper compiles the early Paleozoic mafic and granitic intrusions in the South Qilian belt and the Central Qilian block, to constrain the subduction and accretion of the South Qilian ocean. The early Paleozoic mafic intrusions in the Central Qilian block indicate that the influence of slab-derived fluids dominates their petrogenesis, while the mafic intrusions in the South Qilian belt were mostly affected by involvement of significant sediment-derived melts in their formation. They are supportive of a melange model, in which melting of melange diapirs originating at the slab-mantle interface generates fluid-metasomatised magma source in the deep mantle under the Central Qilian block and sediment-derived melts-metasomatised magma source under the Hualong block in the South Qilian belt, consistent with northward subduction of the South Qilian ocean. It is proposed that northward intra-oceanic subduction of the South Qilian Ocean occurred at 530-470 Ma in front of the Hualong block and continued at 470-446 Ma but was then accompanied by the development of a mature volcanic arc. Continuous subduction resulted in accretion of the Hualong block northwards onto the Central Qilian block, and this collision started at ca. 446 Ma and lasted to ca. 420 Ma. The final closure of the South Qilian ocean was marked by the onset of continental collision between the Qaidam-Quanji block and the amalgamated Hualong-Central Qilian block at ca. 440 Ma, and also the cause of the A-type granitoids after final collision occurred at ca. 420 Ma.

The present study addresses a comparative analysis of the potentials of Airborne Visible and infrared imaging spectrometer -next generation (AVIRIS-NG) data, with respect to Landsat-8 Operational Land Imager (OLI) data for mapping of sporadic exposures of mafic cumulates within the anorthosite intrusion and delineation of major lithological units of Sittampundi layered complex. AVIRIS-NG and Landsat-8 OLI data were initially compared using scene-based relative signal-to-noise ratio (SNR) analysis. Subsequently, spectral anomaly maps were generated to map different lithological rock units using the constrained energy minimization (CEM) approach. Spectral maps derived using CEM were further filtered by low-pass filtering to control the false-positive result. Spectral angle mapper (SAM) classification technique was applied to analyze the suitability of AVIRIS-NG and Landsat-8 OLI data for lithological mapping. Confusion matrix analysis was carried out to assess the SAM classified maps. The first vertical derivative (FVD) map of magnetic anomaly and field evidence/geological exposures were used to validate the results. SNR analysis indicates the superior signal strength of AVIRIS-NG data than Landsat-8 OLI data. Moreover, combined analysis based on CEM and SAM of remote sensing data and FVD of magnetic anomaly reveals that the false-positive area indicating metagabbro/mafic cumulate is lower in AVIRIS-NG data than Landsat-8 OLI data. This is because of the relatively poor SNR, spectral and spatial resolutions of Landsat-8 OLI data; however, it can be good enough for mapping of metagabbro/mafic cumulate when AVIRIS-NG data is unavailable.

Magmatism in the passive margin records continuum rift of continental lithosphere and onset of seafloor spreading. The ca. 650 Ma ultramafic-mafic dike swarms are the latest magmatic episode in the South Qinling Belt during the Neoproterozoic, and therefore provide a window to address their mantle sources, and the continental rift to drift transition. These mafic dikes have distinct geochemical signatures, and can be grouped as N-MORB-, E-MORB-, and Arc-affinities. The Shiziyan amphibole gabbros have low Rb/Y (

The giant Pulang porphyry Cu-Au district (446.8 Mt at 0.52% Cu and 0.18 g/t Au) is located in the Yidun arc, eastern Tibet. The district is hosted in an intrusive complex comprising, in order of emplacement, premineralization fine-grained quartz diorite and coarse-grained quartz diorite, intermineralization quartz monzonite, and late-mineralization diorite porphyry, which were all emplaced at ca. 216 ± 2 Ma. Mafic magmatic enclaves are found in both the coarse-grained quartz diorite and quartz monzonite. The well-preserved primary mineral crystals in such a systematic magma series (including contemporaneous relatively mafic intrusions) with well-defined timing provide an excellent opportunity to investigate upper crustal magma reservoir processes, particularly to test the role of mafic magma recharge in porphyry Cu formation. Two groups of amphibole crystals, with different aluminum contents, are observed in these four rocks. Low-Al amphibole crystals (Аl2О3 = 6.2–7.6 wt %) with crystallization temperatures of ~780°C mainly occur in the coarse-grained quartz diorite and quartz monzonite, whereas high-Al amphibole crystals (Al2O3 = 8.0–13.3 wt %) with crystallization temperatures of ~900°C mainly occur in the fine-grained quartz diorite and diorite porphyry. These characteristics, together with detailed petrographic observations and mineral chemistry studies, indicate that the coarse-grained quartz diorite and quartz monzonite probably formed by crystal fractionation in the same felsic magma reservoir, whereas the fine-grained quartz diorite and diorite porphyry formed from relatively mafic magmas sourced from different magma reservoirs. The occurrence of mafic magmatic enclaves, disequilibrium phenocryst textures, and cumulate clots indicates that the coarse-grained quartz diorite and quartz monzonite evolved in an open crustal magma storage system through a combination of crystal fractionation and repeated mafic magma recharge. Mixing with incoming batches of hotter mafic magma is indicated by the appearance of abundant microtextures, such as reverse zoning (Na andesine core with Ca-rich andesine or labradorite rim overgrowth), sharp zoning (Ca-rich andesine or labradorite core with abrupt rimward anorthite decrease) and patchy core (Ca-rich andesine or labradorite and Na andesine patches) textured plagioclase, zoned amphibole, high-Al amphibole clots, skeletal biotite, and quartz ocelli (mantled quartz xenocrysts). Using available partitioning models for apatite crystals from the coarse-grained quartz diorite, quartz monzonite, and diorite porphyry, we estimated absolute magmatic S contents to be 20–100, 25–130, and >650 ppm, respectively. Estimates of absolute magmatic Cl contents for these three rocks are 1,000 ± 600, 1,800 ± 1,100, and 1,300 ± 1,000 ppm, respectively. The slight increase in both magmatic S and Cl contents from the premineralization coarse-grained quartz diorite magma to intermineralization quartz monzonite magma was probably due to repeated recharge of the relatively mafic diorite porphyry magma with higher S but similar Cl contents. Mass balance constraints on Cu, S, and Cl were used to estimate the minimum volume of magma required to form the Pulang porphyry Cu-Au deposit. Magma volume calculated using Cu mass balance constraints implies that a minimum of 21–36 km3 (median of 27 km3) of magma was required to provide the total of 2.3 Mt of Cu at Pulang. This magma volume can explain the Cl endowment of the deposit but is unlikely to supply the sulfur required. Recharge of 5–11 km3 of diorite porphyry magma to the felsic magma reservoir is adequate to account for the additional 6.5–15 Mt of S required at Pulang. Repeated diorite porphyry magma recharge may have supplied significant amounts of S and some Cl and rejuvenated the porphyry system, thus aiding formation of the large, long-lived magma reservoir that produced the porphyry Cu-Au deposit at Pulang.

We report stable Ni isotope compositions (��������/������Ni, relative to SRM986) for mafic lavas with a range of -0.16 ��� to +0.20 ��� (n=44), similar to that of peridotite samples. Ocean island basalts (OIB) have been analysed from Iceland (n=6), the Azores (n=3), the Gal��pagos Islands (n=2), and L����ihi, Hawaii (n=1). Samples from Iceland (average ��������/������Ni = +0.13��0.16���, 2s, n=7) display the greatest range in Ni isotope compositions from a single OIB location in this work, of +0.01 ��� to +0.23 ���. Samples from the Azores (average ��������/������Ni = -0.10��0.10 ���, 2s) and Gal��pagos (average ��������/������Ni = -0.01��0.04 ���, 2s) are generally isotopically lighter. The single L����ihi sample has a ��������/������Ni of +0.17 ���. The lightest analysed bulk rock ��������/������Ni in this work, -0.16 ���, is from the Azores island, Pico. Enriched mid ocean ridge basalts (E-MORB), which have (La/Sm)_N>1, are isotopically lighter than normal type MORB (N-MORB), as shown by data from the Mid Atlantic Ridge (n=9) and East Pacific Rise (n=3). All E-MORB average ��60/58Ni = +0.00��0.06 ��� (2s, n=7), whereas N-MORB average ��60/58Ni = +0.14��0.10 ��� (2s, n=5). A suite of 15 mafic samples from the Cameroon Line, comprising lithologies ranging from nephelinites to hypersthene-normative basalts, have Ni isotope compositions that are identical within analytical uncertainty (average ��������/������Ni = +0.08��0.06 ���, 2s). Similarly, MORB samples display no relationship between ��������/������Ni and geochemical indicators of degree of partial melting or fractional crystallisation. Host lavas for two previously analysed ultramafic xenolith suites have ��������/������Ni identical to the average ��������/������Ni of their respective xenolith suites. This is consistent with previously published evidence from peridotites and komatiites that Ni isotopes are not greatly fractionated by melting. Therefore, mafic rocks may preserve the ��������/������Ni of their mantle source. Sampling a greater volume of mantle, their average Ni isotope composition +0.07��0.17 ��� (2s, n=44) may also be a better representation of the Bulk Silicate Earth (BSE), than estimates based purely on peridotites. The ��������/������Ni of MORB co-varies with La/Sm, Rb/Sr, europium anomaly (Eu/Eu*), and K���O/(K���O+Na���O). The relationships between these parameters and ��������/������Ni are consistent with mixing between two model endmembers. One could be depleted MORB or depleted MORB mantle (DMM) with a relatively heavy Ni isotope composition; the other a more enriched endmember that has isotopically lighter ��������/������Ni. The link between lighter ��������/������Ni and enriched lithologies in the mantle is further supported by published evidence of light Ni isotope compositions associated with some pyroxenite xenoliths. However, the curvature of the apparent mixing arrays defined by basalts is hard to reconcile with admixing of geochemically enriched but isotopically fractionated oceanic crustal lithologies. High [Ni] enriched magmas such as kimberlites may be a closer match to the enriched endmember. However, this needs further study.

This review article summarizes the state of the art of cosmogenic 3He (3Hec), with a focus on the most efficient methods for measuring this cosmogenic noble gas in terrestrial samples. After briefly reviewing the scientific applications and production pathways of cosmogenic 3He, I summarize the most important theoretical and practical aspects of 3He analyses and describe the best strategies for correcting for non-cosmogenic 3He components in minerals. I also review our knowledge of 3Hec production rates and explore potential new applications for future studies. Our ability to accurately and precisely measure cosmogenic 3He is mainly constrained by the level of the non-cosmogenic 3He background (i.e., magmatic, radiogenic, nucleogenic, and atmospheric 3He), and thus by the geological characteristics of the samples. Constructing 3He vs. 4He isochrons by analyzing several aliquots from the same sample constitutes a useful and overlooked method that is advantageous because it obviates the often-complicated step of vacuum crushing. This method also allows the direct and joint determination of cosmogenic 3He and the magmatic 3He/4He ratio. I perform numerical modeling to explore the impact of the non-cosmogenic 3He components on the final uncertainties and detection limits of 3He dating. Reducing the magmatic component by selecting phenocrysts in the 100–500 m size fraction improves the precision of cosmogenic 3He analyses. Moreover, it is important to measure U, Th, and Li concentrations in the analyzed minerals and their host rocks to ensure proper corrections for radiogenic 4He and nucleogenic 3He, improving both the accuracy and precision of the method. After summarizing the most important aspects of 3He analytical techniques, including the best 3Hec extraction techniques and the key parameters of noble gas mass spectrometry that result in accurate and precise helium isotopic measurements, I also review 3Hec production rates and their spatial variability. The global database of absolute calibration sites yields a world-wide average 3Hec production rate in olivine and pyroxene of 124 ± 11 at g−1 yr−1 using the LSD scaling and the online CREp calculator (https://crep.otelo.univ-lorraine.fr/#/). Cross-calibrations against 10Be indicate that the ratio of the production rate of 3Hec in olivine/pyroxene to that of 10Be in quartz is 33 ± 2 and increases by less than 7% between sea level and 5,000 m elevation. This important observation demonstrates that 3He in olivine/pyroxene and 10Be in quartz can be considered as synchronized chronometers. However, 3Hec/10Be cross-calibrations based on 3Hec in accessory minerals (zircon, garnet, kyanite, apatite) yield unexpectedly high 3He/10Be production ratios of 40–60 above 3,000 m elevation. As the capture of cosmogenic thermal neutrons by 6Li is unlikely to explain this excess, I discuss other plausible mechanisms that should be explored, such as 3Hec inherited from previous exposure episodes, unrecognized specific reaction pathways, or the impact of snow cover. New cross-calibration data obtained by measuring 3Hec against other cosmogenic nuclides in different settings will advance our understanding of cosmogenic nuclide production rates and improve the accuracy and precision of applications relying on cosmogenic 3He. Other improvements could extend the applicability of the 3He geoscientific toolbox; for example, coupling 3He with radioactive cosmogenic nuclides (10Be, 36Cl, 53Mn) will allow paleoaltimetry or the determination of burial ages or paleo-depths in intermediate and mafic terrains.

This work was supported by Science and Technology Facilities Council grant [ST/S000291/1] to JRD. Baddeleyite (monoclinic; m-ZrO2) is a widespread accessory phase within shergottites. However, the effects of shock loading on baddeleyite U-Pb isotopic systematics, and therefore its reliability as a geochronometer within highly shocked lithologies, are less well constrained. To investigate the effects of shock metamorphism on baddeleyite U-Pb chronology, we have conducted high-resolution microstructural analysis and in-situ U-Pb isotopic measurements for baddeleyite within enriched basaltic shergottites Northwest Africa (NWA) 7257, NWA 8679 and Zagami. Electron backscatter diffraction (EBSD) analyses of baddeleyite reveal significant microstructural heterogeneity within individual thin sections, recording widespread partial to complete reversion from high-pressure (≥3.3 GPa) orthorhombic zirconia polymorphs. We define a continuum of baddeleyite microstructures into four groupings on the basis of microstructural characteristics, including rare grains that retain magmatic twin relationships. Uncorrected U-Pb isotopic measurements form Tera-Wasserburg discordia, yielding new 238U-206Pb discordia ages of 195 ± 15 Ma (n = 17) for NWA 7257 and 220 ± 23 Ma (n = 10) for NWA 8679. Critically, there is no resolvable link between baddeleyite microstructure and U-Pb isotope systematics, indicating negligible open-system behaviour of U-Pb during zirconia phase transformations. Instead, we confirm that high post-shock temperatures exert the greatest control on Pb mobility within shocked baddeleyite; in the absence of high post-shock temperatures, baddeleyite yield robust U-Pb isotope systematics and date the age of magmatic crystallization. Low bulk post-shock temperatures recorded within Zagami (≤220 °C), and suggested within NWA 7257 and NWA 8679 by baddeleyite microstructure and other petrological constraints, confirm that the previously derived baddeleyite age of Zagami records magmatic crystallization, and provide greater age diversity to 225 Ma to 160 Ma enriched shergottites. While our data yield no resolvable link between microstructure and U-Pb isotopic composition, we strongly recommend that microstructural analyses should represent an essential step of baddeleyite U-Pb chronology within planetary (e.g., martian, lunar, asteroidal) and shocked terrestrial samples, allowing full contextualisation prior to destructive isotopic techniques. Microstructurally constrained in-situ U-Pb analyses of baddeleyite thus define new opportunities for the absolute chronology of martian meteorites and, more broadly, shocked planetary materials. Publisher PDF

In this study, the crustal shear velocity structure beneath the Indo-Burma Ranges (IBR) is estimated using inversion modeling of the receiver functions computed at seismic stations operated during 2011–2018. The inversion results describe significant variations in the shear-wave velocity (Vs), velocity ratio (Vp/Vs) and crustal thickness in and around the IBR. The Moho deepens from 41 km in the west to 70 km in the east of the IBR. It is also observed that most of the earthquakes are confined to the crust in the west of the Indo-Burma arc, whilst the east of the IBR is associated with sub-crustal earthquakes, supporting the fact that the Indian plate is dipping beneath the Burma Plate. The dip angle of the Moho in the north of the IBR is smaller (7.8o) than that in its south (9.5o). We found that an average crustal Vs of 3.5 km/s for the highest value of the Vp/Vs ratio (> 1.8) was prevalent at all the stations in the IBR, associated with mafic prehnite-pumpellyite facies basalt and hydroxyl zeolite facies basalt, which suggests that the subducting Indian slab beneath the Myanmar microplate in and around the IBR is under a state of dehydration, where intra-slab earthquakes at varying depths (> 50 km) occur. This observation is highly consistent with the earlier 3-D tomographic results obtained independently.

Mafic microgranular enclaves (MMEs) are hosted by the Early Cretaceous granitic plutons from the Jiaodong Peninsula and are crucial for constraining the petrogenesis of these plutons and understanding the lithospheric evolution in the eastern North China Craton (NCC). This paper presents new geochronological, bulk-rock geochemistry, and Sr-Nd-Hf isotope data for Yashan granodiorite and its MMEs in an effort to build an integrated model of the geodynamic setting during the Early Cretaceous. Zircon U–Pb dating indicates that Yashan granodiorite (116 ± 0.42 Ma) is coeval with its MMEs (117 ± 0.81 Ma). The MMEs display magmatic textures and disequilibrium textures such as acicular apatites, plagioclase with reverse zoning, and overgrowth of amphibole around pyroxene, indicating magma mingling/mixing. The SiO2 (55.64–59.9 wt.%), MgO (3.34–5.25 wt.%), Cr (74–245 ppm), and Ni (24–91.2 ppm) contents of the Yashan MMEs combined with their Sr-Nd-Hf compositions that are identical to local arc-like mafic dikes suggest that their primary magma derived from partial melting of a metasomatised lithospheric mantle. Yashan granodiorite is characterized by relatively high SiO2 (66.93–67.63 wt.%) and low MgO (1.66–1.67 wt.%) contents, I-type, high-K calc-alkaline, metaluminous affinities, and corresponding Hf model ages from Neoarchean-Paleoproterozoic, which indicate that the felsic magma was derived from partial melting of ancient NCC lower continental crust. Our data combined with previous studies on Early Cretaceous MMEs and host granites in the Jiaodong Peninsula indicate that the Cretaceous magmatism is the result of rollback of the subducting Paleo-Pacific plate beneath the eastern NCC. Asthenospheric mantle convection generated by slab rollback induced the thinning of the lithosphere and provided necessary heat to cause partial melting of the lithospheric mantle and overlying lower crust, followed by crustal-mantle interaction. The emplacement of Yashan granodiorite and other Weideshan granites and hosted MMEs indicates the peak of lithospheric thinning.

We present new Sr-Nd-Pb-Hf isotopic data on mafic lavas from the Sivas, Develidağ, Erciyes, and Erkilet volcanic complexes in central Turkey and Tendürek in eastern Turkey to evaluate the mantle sources for volcanism in the context of the geodynamic evolution of the Anatolian microplate. Early Miocene through Quaternary volcanism in Western Anatolia and latest Miocene through Quaternary activity in Central Anatolia were dominated by contributions from two distinct source regions: heterogeneous metasomatized or subduction-modified lithosphere, and roughly homogeneous sublithospheric ambient upper mantle; we model the source contributions through mixing between three end members. The sublithospheric mantle source plots close to the Northern Hemisphere reference line (NHRL) with radiogenic 206Pb/204Pb of ∼19.15, while the other contributions plot substantially above the NHRL in Pb isotope space. The lithospheric source is heterogeneous, resulting from variable pollution by subduction-related processes likely including direct incorporation of sediment and/or mélange; its range in radiogenic isotopes is defined by regional oceanic sediment and ultrapotassic melts of the subcontinental lithospheric mantle. The geochemical impact of this contribution is disproportionately large, given that subduction-modified lithosphere and/or ocean sediment dominates the Pb isotope signatures of mafic Anatolian lavas. Subduction of the Aegean or Tethyan seafloor, associated with marked crustal shortening, took place throughout the region until ca. 16–17 Ma, after which time broad delamination of the thickened lower crust and/or the Tethyan slab beneath Central Anatolia allowed for sediment and/or mélange and slab-derived fluids to be released into the overlying evolving modified mantle. Aggregation of melts derived from both mantle and lithospheric domains was made possible by upwelling of warm asthenospheric material moving around and through the complexly torn younger Aegean-Cyprean slab that dips steeply to the north beneath southern Anatolia.

New petrological and geochemical data for lherzolite, harzburgite, and gabbros in the Darbut ophiolitic melange of west Junggar are combined to constrain the geological evolution of the Darbut ophi...

Due to high metal values and raised difficulties in finding superficial deposits, the exploration for mineral resources needs to reach greater depths. To achieve this objective, integrating ASTER and 3D inversion of aeromagnetic can be a useful tool in imaging deep magnetic mineralization hosting-structures. In this study, we present such integrated approach for deep mineral exploration in some promising zones of Gabal (G) Semna region, Eastern Desert (ED) of Egypt. Aeromagnetic data was used to delineate the structures and their relation to ore deposits and ASTER data was utilized for mapping lithological units and the hydrothermal zones. The 3D inversion was employed to imagine the depth and geometry of the magnetized ore bodies in the zones that identified by processing ASTER data. The 3D magnetic inversion revealed that mafic rocks and metavolcanics exhibit high-amplitude magnetic anomalies. High amplitude (positive) magnetic anomalies are joined with the large susceptibilities metavolcanics. Alteration zones in the mafic to basic bedrock and alongside major fault systems are high potential zones that revealed by ASTER image analysis. Aster and aeromagnetic data were used to map and alteration zones surface geology that can host mineralization and the 3D inversion was applied to outline the subsurface extent of these promising areas. This approach can be broadly used for deep mineral exploration in the Egyptian ED and identical areas around the world.

This study presents the landscape evolution of Lake Yakhi basin in eastern Mongolia where the lake plays an important role in the surface water resources. The multiple paleoshoreline features indicate wave-cut terraces, whereas the modern-day shorelines show that Lake Yakhi is at rapid northward regression. The paleo- and modern-day shorelines imply that the paleo-Lake Yakhi may have covered an extensive area with different hydrological conditions in the past. Lake Yakhi shows a decreasing trend in an area with a loss of ~62.2 km2 or 63.9% of the total area during the past five decades. The hydrological dynamics of Lake Yakhi during the last 50 years show its shift into a playa lake coinciding with the local climate changes in warming since 1987 and drying since 1992. In the lake's margin, mafic igneous provenance indicates a derivation from weathered granite and gneiss terrains on the oceanic island arc. However, in the lake's center, felsic igneous and quartzose sedimentary provenances show a derivation from the pre-existing sedimentary terrain on the active continental margin. Lake Yakhi sediments show the granite (felsic) and granite basalt (felsic to mafic) source rocks with mostly shale and arkose. The A-CN-K ternary plot shows that granites, granodiorites, and tonalities dominated in the lake sediments may have been transported from the source rocks enriched in plagioclase and feldspars. The weathering trend in the source area shows a low degree of chemical weathering and the chemical maturity shows a climatic shift from semiarid to arid climatic conditions in the Lake Yakhi basin. Cette étude présente l'évolution du paysage du bassin du lac Yakhi en Mongolie orientale. Les multiples caractéristiques de la paléosurface indiquent des terrasses découpées par les vagues, tandis que les lignes de rivage actuelles montrent que le lac Yakhi régresse rapidement vers le nord. Les lignes de rivage actuelles et les paléolignes de rivage impliquent que le paléo-lac Yakhi a pu couvrir une zone étendue avec différentes conditions hydrologiques dans le passé. Le lac Yakhi montre une tendance à la diminution de sa superficie, avec une perte de ~62,2 km2 (63,9 % de la superficie totale)sur les cinquante dernières années. La dynamique hydrologique du lac Yakhi au cours des 50 dernières années montre sa transformation en un lac de playa coïncidant avec le réchauffement du changement climatique local depuis 2001 et son assèchement depuis 1992. Dans la marge du lac, la provenance ignée mafique indique un dérivé de terrains granitiques et gneissiques altérés sur l'arc insulaire océanique. Cependant, au centre du lac, les provenances ignées felsiques et sédimentaires quartzeuses montrent une dérivation des terrains sédimentaires préexistants sur la marge continentale active. Les sédiments du lac Yakhi montrent les roches mères granitiques (felsiques) et basaltiques granitiques (felsiques à mafiques) avec principalement des schistes et des arkoses. Le tracé géochimique ternaire A-CN-K montre des granites, des granodiorites et des tonalites dominantes dans les sédiments lacustres transportés depuis les roches mères enrichies en plagioclase et en feldspath. La tendance à l'altération dans la zone source et la maturité chimique montrent un faible degré d'altération et un passage de conditions climatiques semi-arides à arides.

The Sarıseki mineralization has 4.3 million tonnes of 0.47 wt% Cu and is one of the newly-discovered massive sulfide formations in the Central Pontides. Mineralization occurred within deep marine sediments interlayered with mafic sills and/or lavas of the Çangaldağ Metamorphic Complex. The lithologic units in the area of mineralization are metamorphosed under lower-greenschist facies conditions. The metamorphism transformed deep marine sediments into phyllites, whilst mafic sills and/or lava were transformed into chlorite-actinolite schist, chlorite schist and chlorite-epidote schist. The mineral paragenesis of the mineralization is represented by the following minerals in decreasing order of abundance; pyrite, chalcopyrite, sphalerite, and magnetite. Mineralization at different levels has three different textures; banded-disseminated, semi-massive and massive. The Sarıseki mineralization has maximum Cu and Zn contents of 3.4 % Cu and 0.24 % Zn, in the Cu-dominant massive sulfide formations. Within the ore, silicified relict sections of wall rock lithology and grading in the mineralized sections indicates that mineralization might have developed by sub-seafloor replacement processes. Mineralization is dominantly formed within wall rock and metamorphic rocks with clastic origin, with no feeder zones in the lower sections of massive sulfide masses, irregular lenses in mineralization and a strata-bound structure. The mafic-clastic formation of Sarıseki mineralization has similar features to Besshi-type Volcanogenic Massive Sulfide (VMS), an observation that is also supported by the results of ore and wall rock geochemistry.

Generally all orogenic ultrapotassic rocks are formed after melting of metasomatized sub-continental lithospheric mantle via subducted crustal mica-bearing lithologies. Here we present another possible model, based on the study of the small Stomanovo ultrapotassic monzonite porphyry intrusion in the Central Rhodope Massif, Bulgaria. The monzonite dated at 30.50 ± 0.46 Ma is intruded into the voluminous Oligocene (31.63 ± 0.40 Ma) Bratsigovo–Dospat ignimbrite. The monzonite hosts both normally and reversely zoned clinopyroxene phenocrysts. The normally zoned clinopyroxene is characterized by gradually diminishing core-to-rim Mg no. (89–74), whereas the reversely zoned clinopyroxene has green Fe-rich cores (Mg no. 71–55) mantled by normally zoned clinopyroxene (Mg no. 87–74). Neither the core of the normally zoned clinopyroxene nor the Fe-rich green cores are in equilibrium with the host monzonite. This ultrapotassic monzonite shows more radiogenic Sr isotopes ((87Sr/86Sr)i= 0.71066) and ϵNd(t) = −7.8 to −8.0 that are distinct from the host ignimbrites with (87Sr/86Sr)i= 0.70917–0.70927 and ϵNd(t) = −4.6 to −6.5. The Sr–Nd isotopic data and the presence of copious zircon xenocrysts from the underlying metamorphic basement suggest extensive crustal assimilation. Our observations indicate that the Stomanovo ultrapotassic monzonite formed after extensive lower or middle crustal fractional crystallization from an evolved magma producing cumulates. The process was followed by hybridization with primitive mantle-derived magma and subsequent continuous crustal contamination. We suggest that instead of inheriting their high K2O and large-ion lithophile element enrichments from slab-derived/metasomatic fluids, the Stomanovo ultrapotassic monzonite may owe some of its unusually high alkalinity to the assimilation of potassium-rich phases from the Rhodope Massif basement rocks.

Clinopyroxene-only thermobarometry is one of the most practical tools to reconstruct crystallization pressures and temperatures of clinopyroxenes. Because it does not require any information of coexisting silicate melt or other co-crystallized mineral phases, it has been widely used to elucidate the physiochemical conditions of crystallizing magmas. However, previously calibrated clinopyroxene-only thermobarometers display low accuracy when being applied to mafic and intermediate magmatic systems. Hence, in this study, we present new empirical nonlinear barometric and thermometric models, which were formulated to improve the performance of clinopyroxene-only thermobarometry. Particularly, a total of 559 experimental runs conducted in the pressure range of 1 bar to 12 kbar have been used for calibration and validation of the new barometric and thermometric formulation. The superiority of our new models with respect to previous ones was confirmed by comparing their performance on 100 replications of calibration and validation, and the standard error of estimate (SEE) of the new barometer and thermometer are 1.66 kbar and 36.6 ∘C, respectively. Although our new barometer and thermometer fail to reproduce the entire test dataset, which has not been used for calibration and validation, they still perform well on clinopyroxenes crystallized from subalkaline basic to intermediate magmas (i.e., basaltic, basalt-andesitic, dacitic magma systems). Thus, their applicability should be limited to basaltic, basalt-andesitic and dacitic magma systems. In a last step, we applied our new thermobarometer to several tholeiitic Icelandic eruptions and established magma storage conditions exhibiting a general consistency with phase equilibria experiments. Therefore, we propose that our new thermobarometer represents a powerful tool to reveal the crystallization conditions of clinopyroxene in mafic to intermediate magmas.

A stage of mafic magmatic activity occurred in Early Permian in the Dabasong Uplift of Junggar Basin, part of the magma intruded into the normal sedimentary and shallow buried fine sandstone to form diabase, and part of the magma erupted to form basalt. The surrounding fine sandstone just entered in the early diagenetic stage A when the magma intruded. The compaction of the surrounding clastic rock and rupture of a small number of clastic grains were caused by the extrusion of the magma intrusion. The presence of chemically deposited alkaline minerals such as calcite, dolomite, shortite, natural alkali, and northupite indicates an alkali lake sedimentary environment for the Fengcheng Formation. Primary alkaline minerals dissolved from the surrounding rocks were subsequently transported and precipitated to form cements. The formation of the calcite cements and calcite metasomatism resulted in considerable densification of the surrounding rock during early diagenesis and destruction of the reservoir quality. The mafic magma had abundant Fe2+ and Mg2+ ions and was deficient in K+ ions, resulting in large amounts of chlorite and iron precipitation in the surrounding rock mainly composed of clay. We have analyzed the influence of an ultrashallow intrusion on the surrounding clastic rock during the early diagenetic period, which provided a typical reference for establishing a systematic mechanistic model of how magmatic intrusions affect the surrounding rock.

Vein, stockwork, skarn, and carbonate-replacement Sn deposits commonly contain little or no Cu, but examples rich in Cu are also well known in many Sn belts worldwide. The origin of Sn-Cu deposits in association with fractionated and reduced, ilmenite-series granites of mostly metasedimentary crustal parentage is enigmatic because Cu, in contrast to Sn, normally accompanies oxidized, magnetite-series intrusions ultimately of mantle origin. Decompression mantle melting in back-arc or post-collisional settings generates mafic magmas, which are commonly invoked as the triggers for partial melting of thick overlying metasedimentary crust to form the fractionated, peraluminous, ilmenite-series magmas required to generate any associated Sn mineralization. Therefore, it is reasonable to suppose that oxidized fluids exsolved from these mafic magmas can contribute Cu to the synchronous and coexisting silicic chambers, thereby adding Cu to reduced Sn-bearing fluids and any resultant Sn deposits. Copper could also be released from Cu-bearing immiscible magmatic sulfides, formed during early crystallization of the reduced silicic magmas, as a result of either the introduction of these oxidized fluids and/or magma degassing. These putative mechanisms are restricted to thick metasedimentary crust, whereas in dominantly metaigneous crust the resultant magnetite-series magmas generate Cu deposits. This fundamental crustal influence on Sn versus Cu metallogeny of back-arc or post-collisional settings is responsible for both along- and across-strike transitions from the Central Andean Sn belt to regions displaying partly coeval Cu ± Au mineralization.

Fluid flux through Earth’s surface and its interior causes geochemical cycling of elements in the Earth. Quantification of such process needs accurate knowledge about the composition and properties of the fluids. Knowledge about the fluids in Earth’s interior is scarce due to limitations in both experimental methods and thermodynamic modeling in high/ultrahigh pressure–temperature conditions. In this study, we present halogen (Cl, F) measurements in apatite grains from the mafic (metagabbro), and felsic (two-pyroxene granulite, charnockite, hornblende-biotite gneiss) rocks preserved in the Nilgiri Block, southern India. Previous experiments show that it is difficult to incorporate Cl in apatite compared to F at high pressure and temperature conditions. Based on regional trends in Cl and F content in apatite (with highest Cl content 2.95 wt%), we suggest the presence of acidic C–O–H fluids in the lower crust (~20–40 km deep) during the high-grade metamorphism of these rocks. These fluids are capable of causing extreme chemical alterations of minerals, especially refractory ones. They also have significant potential for mass transfer, causing extensive geochemical variations on a regional scale and altering the chemical and isotope records of rocks formed in the early Earth. Our findings have important relevance in understanding speciation triggered by acidic fluids in the lower crust, as well as the role of fluids in deep Earth processes.

The West Junggar (WJ) is generally accepted as a Paleozoic archipelago-type orogenic system and records a multiple arcs amalgamation history; however, some of the associated processes require further examination. In this paper, we conducted detailed field investigations and large-scale mapping in the Saier Mountains, northern WJ, and identified several episodes of magmatism and deformation events. The felsic rocks (dioritic porphyrite and granitic porphyry), characterized by a dense cleavage, were emplaced at the Early–Middle Silurian (433–423 Ma). These rocks exhibit geochemical characteristics comparable to those of the coeval adakite-like rocks and A2-type granites in the Xiemisitai Mountains. The undeformed mafic dike swarms yielded SHRIMP zircon age of 382 ± 6 Ma and intruded the Hebukesaier ophiolitic melange (HOM) as well as the surrounding rocks. The HOM, Silurian felsic intrusions and pyroclastic rocks (422 ± 9 Ma) in the Saier Mountains commonly display cleavage attributed north–south shortening during 422–382 Ma. Deep-sea bedded cherts and turbidites in the area also experienced deformation and exhibited cleavage, with subduction-related fold deformation partially preserved in the HOM. The fold deformation was greatly related to a subduction-accretion process of the Hongguleleng–Balkybey Ocean during the Ordovician. Considering the geochronology and geochemistry data, the extensive Silurian–Early Devonian magmatism in the northern WJ indicates a prolonged (~40 Ma) and episodic post-collisional extension in this orogen and records an obvious trend of crustal temperature increasing and thickness thinning from 435 to 410 Ma. The regional extrusion deformation was attributed to the southward subduction of the Irtysh–Zaysan Ocean during the Middle Devonian, and then the slab roll-back offered an extensional setting which favored the emplacement of mantle-derived mafic dike swarms. We propose that the northern WJ probably experienced a complicated evolution involving archipelago amalgamation and tectonic transform in the middle Paleozoic, providing a new sight to reveal the orogenic process of the Central Asian Orogenic Belt (CAOB).

Distinct mantle compositions recorded in primitive West Antarctic magmatic rocks vary by tectonic setting and time. Deep asthenospheric mantle-plume sources or shallow metasomatized mantle sources may operate either coincidently or independently to supply melts for magmatism. For example, contemporaneous subduction and plume dynamics produced the Ferrar–Karoo Large Igneous Province; subduction-related melting followed by slab-rollback or melting of slab-hosted pyroxenite explains Antarctic Peninsula volcanism through time; Marie Byrd Land magmatism results from plume materials variably mixed with subduction-modified mantle; while magmatism in Victoria Land and western Ross Sea is best explained by plate dynamics and melting of asthenospheric and metasomatized lithospheric sources, and not by an upwelling plume. Element and isotopic ratios show a fundamental change between Marie Byrd Land and Victoria Land mantle domains. Specifically, Pb isotopes indicate that Victoria Land magmatism sources have a stronger focal zone (FOZO) mantle component, while Marie Byrd Land magmatism possesses more of the high μ = high 238 U/ 204 Pb (HIMU) mantle component that leads to high 206 Pb/ 204 Pb over time. The chemical and isotopic heterogeneity of relatively unfractionated igneous rocks in West Antarctica reflects fundamental differences in mantle domains and melting conditions. This mantle variability coincides with changes in crustal structure and composition, and has a geophysical signature that is manifest in seismic data and tomographic models.

The Manzhouli–Xin Barag Right Banner area, located in the southwestern Erguna Massif, is characterized by the distribution of a large volume of Mesozoic volcanic rocks and many polymetallic deposits. However, the tectonic setting of this area during the Late Mesozoic remains controversial. In this study, zircon U–Pb ages range from 142.8 ± 1.8 to 140.4 ± 1.6 Ma for the alkali basalt from the Meiletu Formation and 140 ± 0.9 Ma for alkaline rhyolites from the Baiyingaolao Formation, forming a bimodal volcanic rock assemblage. The initial 87Sr/86Sr ratios range from 0.705365 to 0.705674, and the eNd(t) values vary from + 0.55 to + 1.47. The alkaline rhyolites show eHf(t) values ranging from + 5.3 to + 8.6, corresponding to TDM1 and TDM2 ages in the range of 0.48–0.58 Ga and 0.64–0.86 Ga, respectively. Combined with the major and trace element compositions, the Meiletu alkali basalts are characterized by Nb enrichment (averaging 23.6 ppm) and were derived from partial melting of metasomatized subcontinental lithospheric mantle and underwent moderate fractional crystallization of minerals (e.g. olivine, clinopyroxene, apatite, and plagioclase). The alkaline rhyolites show A1-type granite affinity and originated from partial melting of the mafic lower crust accompanied by fractional crystallization. This suite of bimodal volcanic rocks was mainly dominated by the Mongol–Okhotsk tectonic regime, and the Erguna Massif was in a back-arc extensional setting triggered by slab rollback during the Early Cretaceous.

A comparative study of the Precambrian Sonakhan (SGB) and Mahakoshal (MGB) greenstones belts of Central India has been undertaken to decipher their provenance, paleoweathering, paleogeography, and tectonics. As compared to the Upper Continental Crust (UCC), the MGB samples are enriched while the SGB samples are depleted in mafic elements indicating the presence of mafic rocks in the source of the MGB. This is complemented by the Ni–Cr diagram. The REE concentrations, LREE fractionated patterns and negative Eu anomalies of the MGB and SGB samples indicate derivation of sediments from a highly fractionated granitic source. Since MGB samples also contain the geochemical signature of mafic rocks, it is, therefore proposed that the MGB clastic load were derived from two sources (mafic + felsic) with arc character. This is attested by Cr and Zr relationships, and LILE enrichment, and HFSE depletion. These features suggest that the SGB developed as autochthonous while the MGB developed as an allochthonous belt. The chemical alteration indices such as chemical index of alteration (CIA), plagioclase index of alteration (PIA), and index of compositional variability for MGB samples indicate that they were dominantly derived as the first cycle (with minor recycled) sediments from bimodal sources (dominantly continental arcs) by intense chemical weathering as compared to the SGB samples, which were derived from felsic sources (dominantly cratonic rocks), and partly by recycling through a low chemical weathering. The CIA and PIA values of the samples reveal a change in the climatic conditions from Late Archean to Late Paleoproterozoic. Such change is interpreted in terms of migration of the Indian plate from high latitudes in the Late Archean to lower latitudes during the Late Paleoproterozoic. This is consistent with the paleomagnetic data that placed India in the configuration of 2.45 Ga Ur and 1.78 Ga Columbia supercontinents.

Both felsic and mafic intrusions occur in mantle peridotites of the New Caledonia ophiolite (Peridotite Nappe) and record important information regarding the magmatic evolution during subduction in...

The association between Large Igneous Provinces (LIPs) and mass extinctions and anoxic events is attributed to the radical climatic changes in Earth. Even though the Early Cretaceous Paraná–Etendeka Igneous Province has a comparable erupted volume (>1 Mkm3) to other LIPs (e.g., Deccan, Emeishan and Siberian Traps), it remains controversial why this LIP did not contribute to a mass extinction and whether it is associated with the Weissert Event. This work presents new 40Ar/39Ar dating over a 425-m vertical stratigraphic profile (out of 1,000 m) that spans three formations of the PE-LIP in southern Brazil (low-Ti Vale do Sol, high-Ti Urubici, and high-Ti Palmas). Our data demonstrate that this mafic lava pile was emplaced in c. 2.0 m.y., from c. 135.5 Ma to c. 133.5 Ma, and endorse the hypothesis that the basaltic and andesitic flows of the Vale do Sol Formation (peak of mafic magmatism) contributed to the Weissert Event.

Natural hydrogen seeps called fairy circles have been identified in Mali, Brazil, Russia, and United-States. Natural hydrogen is produced from a field in Mali for 7 years. The natural hydrogen system is still poorly understood and needs to be studied in new geological contexts as to streamline hypotheses on the system dynamics and elements into concepts. In Australia, numerous circular surface features, commonly called salt lakes or swaps, are visible from the sky but no existing work shows nor quantifies any hydrogen content in those features. In this study, we reviewed the existing literature on fairy circles as to determine and directly test with soil-gas measurements if hydrogen surface-emitting features are present in Australia. We determined best candidates to test with a multi-disciplinary approach linking geology, multi-physical imaging, and seismic interpretation. Soil-gas measurements showed persistent hydrogen concentration localized in the external ring of circular depressions aligned along the Darling Fault, a major crustal boundary between the granitic, mafic and ultramafic rocks of the Yilgarn Craton from the sedimentary rocks of the Perth Basin. This work is the proof that fairy circles, in the meaning of H2 emitting structures, are present in Australia and opens the door to new prospectivity pathways by evaluating original hypotheses on natural hydrogen generation, migration pathways and entrapment. This geological setting promotes deep serpentinization of ultramafic rocks as well as oxidation of iron-rich Archean rocks and mafic dikes as potential hydrogen sources that are both of massive potential economic value. This hydrogen can circulate and be entrapped as aqueous hydrogen in low-salinity aquifers or migrate in gaseous phase in fault zones up to intermediate structural reservoir or to the surface.

Gold exploration in the Mahakoshal belt has been carried out for the past thirty years and mostly quartz veins were identified as the host targets. The recent study based on the concept of mineral system has indicated that gold occurs in mafic and ultramafic rocks also, besides the quartz veins. The mineralisation in Agori Formation is generally confined to Algoma type BIF, metavolcanics and phyllites, while in Parsoi Formation it occurs predominantly in quartz veins. The metavolcanics have acted as source rocks and the crustal deep faults have acted as conduits for mineralizing fluids, in the continental back arc type tectonic setting with two mineral systems viz. (i) basin related fluid flow with active magmatism, and (ii) magmatic related hydrothermal system.

—Thermal metamorphism produced an aureole near the early Paleozoic Bayan-Kol gabbro–monzodiorite intrusion in the Erzin shear zone of western Sangilen (Tuva–Mongolia microcontinent, Central Asian Orogenic Belt). Field observation of intrusive contact, structure–textural and mineral transformations of metamorphic rocks, regular changes in the chemical composition of minerals with approaching the intrusive contact, and high temperature gradient from intrusive to wallrocks verified the occurrence of a contact aureole near the Bayan-Kol intrusion. The high-gradient thermal metamorphism (M2) affected garnet–staurolite–kyanite schists that formed during earlier regional metamorphism (M1) at 6.2–7.9 kbar and 600–670 ºC. The 0.5 km wide M2 metamorphic aureole mapped along the northwestern intrusion margin consists of a muscovite–sillimanite zone adjacent to the sedimentary country rocks and a cordierite–K-feldspar zone on the side of the intrusion. The M2 metamorphic reactions occurred within the granulite facies temperature range 880–910 ºC along the contact with monzodiorites and at ~950 ºC along the boundary with gabbronorites; the temperature on the aureole periphery was about 640 ºC. Pressure estimates indicate deep-seated high-grade metamorphism at 6.9–7.8 kbar, while the intrusion itself crystallized at 7.7–7.8 kbar. The suggested numerical model implying the formation of a thermal aureole at a depth of 26 km (7 kbar) in the lower crust is consistent with the temperature pattern determined by geothermobarometry for several key points of the metamorphic zoning and confirms its deep-level origin. Thus, the aureole near the Bayan-Kol intrusion represents a rare case of contact metamorphism in the lower continental crust. The obtained results, along with published petrological and geochronological evidence, reveal two depth levels of the early Paleozoic M2 metamorphism in the Sangilen area: upper (7–15 km, 2–4 kbar) and lower (26–30 km, 7–8 kbar) crust. The Bayan-Kol gabbro–monzodiorite intrusion is likely a small apophysis or a fragment of a deep-crust intermediate magma chamber, while the moderate-pressure (7–8 kbar) M2 granulites in the Erzin shear zone are products of high-gradient metamorphism related to the Cambrian–Ordovician collisional mafic magmatism in the Sangilen area.

Supracrustal rocks and garnet granite within the high-grade metamorphic complex in Daqingshan, at the northern margin of the Palaeoproterozoic Khondalite Belt, North China Craton (NCC), preserve various mineral assemblages that record three distinct stages of their metamorphic evolution. The mineral assemblages representative of prograde metamorphism (M1) comprise plagioclase (Pl) + quartz (Q) ± biotite (Bio) inclusions preserved in garnet porphyroblasts in gneiss and granite members. The metamorphic peak mineral assemblages (M2) are represented by garnet (Gt) + Pl + Bio + Q + sillimanite (Sil) + K-feldspar (Kfs) in each rock’s matrix. Retrograde mineral assemblages (M3) that formed during post-peak, near-isothermal decompression (ITD) occur between relict garnet porphyroblasts and matrix minerals. These M3 assemblages consist of Bio + cordierite (Crd) + Pl + Gt + Q + Sil + Kfs. Phase equilibria modelling shows that the supracrustal rocks record clockwise pressure–temperature (P–T) trajectories from 650 to 750 °C/5.3–8.9 kbar (M1) up to 800–830 °C/9.8–11.2 kbar (M2), to 760–830 °C/4.8–6.2 kbar (M3). Geochemical similarities between the Daqingshan supracrustal rocks (i.e. garnet-biotite gneisses) and garnet granites, such as relative enrichment in K, Rb, and Ba, and depletion in Th, U, Ta, Nb, P, and Ti, imply a petrological affinity. Sensitive high-resolution ion microprobe analysis (SHRIMP) U–Pb dating of zircons reveals that the protolith of the Daqingshan supracrustal rocks formed at ~2.5 Ga and subsequently metamorphosed at ~2.45–2.37 Ga. Anatexis likely occurred at ~2.43–2.40 Ga during the retrograde near-ITD stage. Combined with previous studies, the timing of metamorphism and anatexis in the Daqingshan area may be connected with the regional mafic magmatism.

To constrain the mechanisms governing the extremely large variations of Mg and Fe isotopes in magmatic Fe–Ti oxides in layered mafic intrusions, we investigate Mg isotopic compositions of magnetite, coupled with its chemical data and whole-rock major element and Sr-Nd isotope compositions from the Baima layered mafic intrusion in the Emeishan large igneous province, SW China. The Baima intrusion is mainly composed of magnetite-wehrlite and magnetite-troctolite (i.e., oxide-rich rocks) in the Lower Zone, and troctolite and gabbro (i.e., oxide-barren rocks) in the Middle and Upper Zones. Magnetite separates display large Mg isotopic variation, with δ26Mg ranging from −0.17 ± 0.06 to +0.58 ± 0.04‰ in the oxide-rich rocks and from −0.18 ± 0.06 to +0.98 ± 0.04‰ in the oxide-barren ones. The lack of correlation of δ26Mg with trace elements in magnetite and whole-rock Sr-Nd isotopic compositions indicates that the large Mg isotopic variation in magnetite was not produced by fractional crystallization, magma mixing, crustal contamination, and/or trapped liquid shift. Instead, equilibrium isotope fractionation induced by Mg–Fe re-equilibration between magnetite and ilmenite at different subsolidus temperatures controlled the Mg isotopic variation in the oxide-rich rocks; and kinetic isotope fractionation driven by Mg–Fe inter-diffusion between magnetite and olivine and/or clinopyroxene dominated the oxide-barren rocks. Both processes were primarily controlled by the assemblage and modal abundance of coexisting minerals to which magnetite adjoins. Overall, fractional crystallization and subsequent subsolidus diffusion played crucial roles in the genesis of the Fe–Ti oxides in the Baima intrusion. Our results also reveal widespread isotope disequilibrium between coexisting minerals in mafic magma chambers and suggest that Mg isotope geochemistry has a great potential to characterize the formation of Fe–Ti oxides in layered mafic intrusions.

In this contribution, the evolution of the Ladakh magmatic arc encompassing ca 160 Ma history from subduction initiation to intra-oceanic arc collision to final continent-continent collision is summarized. The observed compositional variation in Ladakh magmatic arc reflects directional maturity from mafic magmatism towards south to more acidic magmatism towards north, and therefore indicating northward dipping subduction. Based on the ca 160 Ma Neo-Tethys geodynamic reconstruction, the evolution of the Ladakh magmatism can be summarized into three distinct time periods; (i) from 160 to 80 Ma, representing intra-oceanic island arc (IOIA) complex dominantly of mafic magmatism, (ii) from 80 to 50 Ma, the magmatism shifts to felsic composition (involving Indian continental margin) in the form of Kohistan-Ladakh batholith and (iii) from 35 to 18 Ma, the magmatism occurred in the form of post-collisional dykes. We also support the double collision model of Ahmad et al. (2008), according to which the first collision occurred between IOIA complex (including Kohistan-Ladakh batholith) with southern margin of Asia during mid-Cretaceous to late-Cretaceous along Shyok Suture Zone (SSZ). Finally, the accreted IOIA and Asian plate margin collided with the northern margin of Indian plate during Late Eocene ∼40 Ma along the Indus Suture Zone (ISZ).

Mafic-ultramafic plutonic intrusions form an early phase in the emplacement of the predominantly granitic Vioolsdrif Suite, which together with its extrusive carapace, the Orange River Group, form the Richtersveld Magmatic Arc, a Palaeoproterozoic crustal segment formed between 1910 and 1865 Ma. Their lithologic character and distinctive dark weathering features in the mountain desert landscape of the Richtersveld, neighbouring regions of the Northern Cape Province and southern Namibia, make them a separate mappable unit in what is a predominantly granitic terrain. The name of the subsuite is taken from a spectacular twin peak massif near Goodhouse (Vuurdoodberg), while the type locality is one of the best preserved central-type intrusive bodies at Swartkop, situated 2 km off the N7 highway about 20 km south of the border town of Vioolsdrif, where the rock types present include gabbro, metagabbro, quartz-metagabbro, peridotite and troctolite.

International audience; We present new field evidence, geochemical and isotopic data, and age constraints on Lower Jurassic mafic rock suites within a >200-km-long curvilinear belt in the Rif orogenic belt in northern Morocco and show that these rock assemblages formed as part of the Central Atlantic Magmatic Province (CAMP). The CAMP represents a large igneous province that straddles the edges of the modern peri-Atlantic continents. It developed ~200 Ma, following the initiation of the breakup of Pangea. Main magmatic rocks in the Rif External Zone include basaltic lavas, massive dolerite, and isotropic and cumulate gabbros, all intruded by dolerite and trondhjemite dikes and sills. Available U-Pb zircon ages from dolerite, gabbro, and trondhjemite dike rocks are 200±4, 196±4, and 192±Ma, respectively. Based on their geochemical affinities and isotopic compositions, the analyzed rocks define basalt-dolerite and gabbro-cumulate gabbro-trondhjemite groups. The basalt-dolerite group samples are subalkaline in nature and have low TiO2 contents, whereas the gabbro-cumulate gabbro-trondhjemite group samples are alkaline and display high TiO2 values. Most samples are tholeiitic in character and show large-ion lithophile and light rare earth element enrichment and high field strength element depletion compared with normal mid-ocean ridge basalt (MORB). Samples of both groups display low 143Nd/144Nd201 Ma (0.51182–0.51262) and high 87Sr/86Sri ratios with ɛNd values ranging from −1.51 to +4.85. The basalt-dolerite group rocks have enriched MORB compositions, compatible with the low-Ti CAMP suites, whereas the gabbro-cumulate gabbro-trondhjemite group rocks have oceanic island basalt compositions reminiscent of high-Ti CAMP suites in other continents. Magmas of the gabbro-cumulate gabbro-trondhjemite group underwent differentiation through tholeiitic fractionation. Magmas of the rocks of both groups included melt components, originated from partial melting of a previously subduction-modified subcontinental lithospheric mantle. Our results indicate that the Early Jurassic CAMP magmatism in northern Morocco marked a major episode of continental magmatism before the opening of the Maghrebian Tethys between Africa and Iberia in the latest Jurassic.

Along the eastern margin of the Mesoproterozoic Namaqua metamorphic province (NMP) of southern Africa are a bimodal volcano-sedimentary succession, the ∼1.13–1.10 Ga Koras Group, composed of rhyolitic porphyries and basaltic andesites, and the ∼1.11–1.07 Ga late- to post-tectonic granitoids of the Keimoes Suite. This review examines existing whole-rock major- and trace-element data, along with isotope chemistry (with some new isotopic data), to investigate the role these two magmatic successions played in terms of post-collisional magmatism of the eastern NMP near the boundary with the Archean Kaapvaal Craton. The Keimoes Suite comprises variably porphyritic biotite monzogranites and granodiorites, with a charnockitic member. They are metaluminous to weakly peraluminous, ferroan, and calc-alkalic. They exhibit large ion lithophile (LIL) element enrichment relative to the high field strength elements (HFSE) with depletions in Ba, Sr, Nb, P, Eu and Ti, and enrichments in Th, U and Pb. Isotopic values (eNd(t): 2.78 to -2.95, but down to -8.58 for one granite, depleted mantle Nd model ages (TDM): 1.62–1.99 Ga, but up to 2.55 Ga; initial 87Sr/86Sr: 0.652 82–0.771 30) suggest derivation from weakly to mildly enriched (and radiogenic) sources of Meso- to Paleoproterozoic age, the former of more juvenile character. The Koras Group is characterized by a bimodal succession of calcic to calc-alkalic, magnesian and tholeiitic basaltic andesites and mostly metaluminous to peralkaline rhyolitic porphyries. Two successions are recognised, an older, lower succession that extruded at ∼1.13 Ga, and a younger, upper succession at ∼1.10 Ga. The rhyolitic porphyries of both successions show similar LILE/HFSE enrichment and the same element enrichments and depletions as the Keimoes Suite granitoids. The upper succession is consistently more fractionated in terms of both whole-rock major and trace element chemistry, and, isotopically, has a greater enriched source component (eNd(t)}: −0.69 to −4.26; TDM: 1.64–2.44 Ga), relative to the lower succession (eNd(t): 0.74–5.62; TDM: 1.28–2.12 Ga). Crystal fractionation of plagioclase and K-feldspar appears to have played a role in bringing about compositional variation in many of the granites. These were derived from partial melting of mainly igneous with subordinate sedimentary sources from mostly lower crustal depths, although some granitoids have indications of a possible mantle source component. The lower succession of the Koras Group was derived by partial melting of subduction-influenced enriched mantle giving rise to mafic magmas that fractionated to give rise to the rhyolitic porphyries. The upper succession rhyolites were derived by crustal melting due to the input of mafic magmatism. Crystal fractionation was the main compositional driver for both successions. The Keimoes Suite granitoids and the Koras Group are associated with extensional regimes subsequent to the main deformational episode in the eastern NMP.

Many silicic plutonic rocks of the Late Permian Emeishan large igneous province (ELIP) are spatially and temporally related to oxide ore-bearing layered mafic–ultramafic intrusions. Their association suggests that there may be a petrogenetic link between the two rock types where the layered intrusion represents the cumulate portion of the magma system and the silicic rocks are the residual liquid portion. An alkali feldspar syenite collected in close spatial association with the Hongge-layered mafic–ultramafic intrusion yielded a weighted-mean zircon U–Pb age of 261.5 ± 2.4 Ma with a corresponding weighted-mean eHf(t) value of + 6.5 ± 0.5. The Hongge syenite is alkalic, metaluminous, and ferroan and somewhat similar to other A-type granitoids of the ELIP but, it is composed of ~ 90 vol% alkali feldspar. The rocks have initial 87Sr/86Sr ratios of 0.70570 and 0.70515 and eNd(t) values of − 0.3 and + 1.4. Rhyolite-MELTS and isotopic modeling indicate that the Hongge syenite is likely produced by crystal accumulation of a residual silicic liquid derived from a mafic parental magma that experienced localized crustal contamination during emplacement. Moreover, the age, location, and composition of the Hongge syenite suggests that it is the uppermost portion of the Hongge-layered intrusion and is representative of the residual silicic liquid of the mafic magmas that form the plagioclase-rich cumulate gabbros of the upper zone.