Search

The Dongueni Mont nepheline syenite intrudes migmatitic paragneisses and siliciclastic metasediments of the Barue Complex, Mozambique. This study reports the whole-rock geochemical, U-Pb and Nd isotopic data of the nepheline syenite. The ferroan and alkalic geochemical characteristics are typical of alkaline rocks formed in a within-plate setting. The strong depletion in high field strength elements (HFSEs) (e.g. Ba, Nb, P, and Ti) and enrichment in large ion lithophile elements (LILEs) (e.g. Rb, Th, K, and Pb) are consistent with magmatism in a continental alkaline magmatic province associated with intracontinental rifting. Zircon U-Pb data yielded crystallization ages from 498 ± 19 to 562 ± 14 Ma, consistent with the Pan-African Orogeny and the inherited zircons yield an age of 1040 Ma, which supports the presence of a Mesoproterozoic crust. The eNd (t) values from the nepheline syenite samples range from −15.1 to −16.1 and the TDM values from 1.77 to 1.67 Ga, which indicate that the initial nepheline syenite magma formed from a tholeiitic or mantle source in a within-plate setting with crustal assimilation.

Triassic magmatic and tectonic reactivation has played a crucial role in remolding the tectonic framework of Eastern Tianshan, NW China, but is poorly understood. Triassic granites in Eastern Tianshan contain magmatic zircons with euhedral to subhedral shapes and concentric oscillatory zoning structures. These zircons have relatively high Th/U ratios (mostly 0.26–0.93) with LA-ICP-MS U-Pb ages of ca. 250–223 Ma, interpreted as the emplacement ages. The granites have high SiO 2 (71.1–77.1 wt.%), Na 2 O (3.1–3.7 wt.%) and K 2 O (4.0–4.7) wt.%, but low Al 2 O 3 (11.8–14.7 wt.%), CaO (1.4–2.3 wt.%), FeOt (1.2–2.2 wt.%) and MgO (0.5–1.0 wt.%) contents, and belong to high-K calc-alkaline I-type granite series. They show low Ni (5.2–32.4 ppm) and Cr (6.4–59.4 ppm) contents and low Ti/Zr (8.5–16.3), Ti/Y (58.3–214.6) and Nb/Ta (8.6–15.2) but high Th/Nb (1.0–1.9) and Th/Ta (9.4–26.2) ratios, suggesting that they were most probably derived from partial melt from late Paleozoic crustal rocks, consistent with Hf isotopes of Triassic zircons falling onto the continental evolution lines. Compositional variations of the granites, such as distinct Eu anomalies (δEu = 0.46–0.52 or 0.66–0.84) and flat or depleted heavy rare earth element (HREE) patterns, indicate variable amounts of residual phases, plagioclase or garnet/amphibole, during partial melting. The apparent subduction-related characteristics, e.g., fractionated REE patterns, strong enrichments in large-iron lithophile elements (e.g., Rb, Th and U) and depletions in high field strength elements (e.g., Nb, Ta and Ti), were probably inherited from the crustal sources. Combining our results with those of previous studies, we suggest that Triassic magmatic and tectonic reactivation in Eastern Tianshan and coeval tectonothermal events in the adjacent regions were possibly dynamically linked to the subduction and/or closure of the Paleo-Tethys Ocean.

The seismic, drilling and logging data reveal that a large-scale igneous intrusion with a width of 14 Km and a maximum thickness of 170 m intruded within the Paleogene Liushagang Formation in the Fushan Depression, Beibuwan Basin, South China Sea (SCS). In this study, we report the geochemistry and Sr-Nd-Pb-Hf isotopic compositions of the igneous rocks, and evaluate the thermal effect induced by this large-scale igneous intrusion on the host rocks. The analyzed igneous samples exhibit strong enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE), having characteristics similar to intra-plate oceanic island basalts (OIB). The Sr-Nd-Pb-Hf isotopic data display narrow ranges (e.g. 87Sr/86Sri = 0.7042–0.7044, 143Nd/144Ndi = 0.5128–0.5129, 206Pb/204Pbi = 18.90–18.94, eHf(t) = +7.56∼+9.60). Geochemical and isotopic compositions suggest a mixed mantle source between depleted mid-ocean-ridge-basalt (MORB) mantle (DMM)-like mantle and enriched mantle type II (EMII, possibly the Hainan mantle plume). Vitrinite reflectance values, major mineralogical changes together with a maturity-related biomarker [Ts/(Ts + Tm)] all reveal significant thermal effect induced by the igneous intrusion. Vitrinite reflectance values of the host rock are up to 2.5% in the intrusion region, whereas lower reflectance values (0.62–0.73%) occur in the unaffected area of the same strata. Moreover, our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below, which should be attributed to the different behavior of hydrothermal fluids. These observations suggest that the thermal effect of large-scale thick igneous intrusions is much more intense than that of thin igneous intrusions, and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process.

The Daheishan Mo deposit of the Lesser Xing'an–Zhangguangcai Range metallogenic belt in northeast China is a super-large molybdenum deposit with Mo reserves of 1.09 Mt. The Mo mineralization occurs mainly in a granodiorite porphyry. Zircon SIMS U–Pb dating yields a crystallization age of 168.3 ± 1.4 Ma for the granodiorite porphyry. Molybdenite Re–Os dating indicates that Mo mineralization occurred at 169.2 ± 1.2 Ma. These geochronological data indicate that these magmatic and hydrothermal activities occurred during the Middle Jurassic. The granodiorite porphyry can be classified as high-K calc-alkaline series, and the rare earth elements (REE) are characterized by a significant fractionation between light REE (LREE) and heavy REE (HREE) with slightly positive Eu anomalies (Eu/Eu* = 1.08–1.12). Large ion lithophile elements (e.g., Rb, U, K, and Pb) are enriched, whereas high field strength elements (e.g., Nb, Ta, Ti, HREEs, and Yb) are strongly depleted. The granodiorite porphyry is also characterized by initial strontium isotope ratios (87Sr/86Sr)i of 0.70460–0.70482 and magmatic zircon δ18O values of 5.2–6.5 ‰ that are similar to those of the mantle. Zircon ɛHf(t) and whole-rock eNd(t) values range from 5.6 to 9.9 and 0.8 to 1.1, respectively. The two-stage Nd model ages (TDM2) are in the range of 868–894 Ma, similar to Hf model ages, indicating that the parent magma has a uniform source and primarily originated from a juvenile crustal source. Combined with the regional geological history, geochemistry of the Daheishan granodiorite porphyry, and new isotopic age data, we propose that the formation of the Daheishan porphyry Mo deposit is likely related to the subduction of the Paleo-Pacific Plate.

Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments. Ho...

This study reports the discovery of an ophiolite located in the Eastern Kunlun Orogen (Dagele, Eastern Kunlun, China) that is mainly composed of isotropic and serpentinized dunite, gabbro, and eclogites. According to the geochemical results, the ophiolite unit is characterized by the depletion of Nb, Ta, and Ti and a slight enrichment in large-ion lithophile elements, which suggests that the Dagele ophiolite was formed in an island arc environment. To constrain the time of formation of the ophiolite, gabbro samples were selected for sensitive high-resolution ion microprobe U–Pb zircon dating and yielded an age of 445 ± 4.8 Ma. By integrating the regional geological and geochronological data, we propose that the Dagele ophiolite is a suprasubduction zone-type. Further studies on this and other ophiolites in the region will provide crucial constraints on the evolution of the Eastern Kunlun Orogen as well as the Proto-Tethys Ocean in central western China.

In order to investigate their precise geochronological framework, petrogenesis, and tectonic implications, whole-rock major and trace elements, together with zircon U–Pb and Hf isotope data, are reported for the Mo-bearing granitoids from the eastern Jilin-Heilongjiang provinces in the eastern segment of the Central Asian Orogenic Belt. Zircon U–Pb dating by LA–ICP–MS yields crystallization ages for the Liushengdian monzogranite porphyry (252.2 ± 1.6 Ma), the Luming monzogranite porphyry (197.1 ± 1.6 Ma), and the Baoshan granodiorite (164.4 ± 1.9 Ma) and quartz diorite (165.2 ± 1.7 Ma), respectively. This zircon U–Pb data, combined with previous ages, indicate that the eastern Jilin-Heilongjiang provinces is dominated by 2 stages of ore-related granitic magmatism and associated Mo mineralization, that is, Late Permian (259–252 Ma) and Early-Middle Jurassic (200–165 Ma). Geochemically, these Mo-bearing granitoids have high SiO2 (60.78–74.67 wt.%) and K2O (2.85–6.23 wt.%), low MgO (0.17–2.85 wt.%) and CaO (0.66–4.38 wt.%) contents, with A/NCK and δEu values of 0.87–1.08 and 0.19–1.07, respectively; we infer that they belong to high-K calc-alkaline series and are metaluminous to peraluminous in nature. They are characterized by enrichment in large ion lithophile elements and light rare earth elements, and weak depletion in high field strength elements and heavy rare earth elements, consistent with the geochemical signatures of subduction-related genesis. In addition, in situ Hf isotopic analyses of zircons from 4 dated samples reveal that they have eHf(t) values of −0.4 to +10.3, with 2-stage model ages varying from 551 to 1,261 Ma, indicating that they probably originated from the partial melting of a dominantly Mesoproterozoic–Neoproterozoic crustal source. On the basis of the geochemical data and regional geological investigations, we propose that the formation of the Late Permian Mo-bearing granite was related to the subduction of the Paleo-Asian Ocean plate, whereas the generation of the Early-Middle Jurassic Mo-bearing granitoids was associated with the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.

New data from mineralogy, geochemistry, zircon U–Pb dating, and Hf isotopes have revealed Late Cretaceous to Eocene magmatic intrusions in the Tengchong terrane and constrained the origin, tectonic setting, and characteristics of tin-bearing and barren granitoids. We divide the studied granitoids into two groups: (a) the Late Cretaceous Zhinaxiang (70 Ma) and Early Paleocene Dazhupeng (65 Ma) S-type barren granites and (b) the Eocene Lailishan A2-type tin-bearing granite (50 Ma). All these granitoids display Si- and K-rich and calc-alkaline characteristics and have similar chondrite-normalized rare earth element patterns. However, geochemical differences do exist between the two groups of granites. The Zhinaxiang and Dazhupeng S-type granites are slightly peraluminous, enriched in large-ion lithophile elements (e.g., Rb and K), and depleted in high-field-strength elements (e.g., Nb, Ta, Zr, and Hf), whereas the Lailishan A2-type granite has higher TFe2O3, high-field-strength element content, and Ga/Al ratios. The geochemical and Hf isotopic data indicate that the granites in this study were generated by partial melting of Paleoproterozoic metasedimentary rocks. Due to the subduction of the Neo-Tethyan Ocean beneath the Eurasian plate, the Zhinaxiang and Dazhupeng S-type granites were formed in a thickened-crustal environment, whereas the Lailishan A2-type granite was emplaced in a post-collisional extensional setting attributed to slab break-off. By comparison between tin-bearing and barren granites, we propose that the Sn mineralization could be related to relatively high-temperature and low-pressure crystallization conditions.

We present an overview of the internal structure of the 10 ophiolitic melanges in the Central China Orogen (CCO) with a focus on the geochemical character and tectonic evolution of the ophiolitic melange-related ocean island basalt (OIB) and mafic rock assemblages. The ophiolitic melanges in CCO are generally complicated and usually consist of metamorphic peridotites (serpentinite), cumulates, gabbros, basaltic lavas (pillows), and abyssal radiolarian cherts. The ages of ophiolitic melanges range from Mesoproterozoic to Carboniferous. The OIB-type basalts and mafic rocks in CCO occur as tectonic blocks within the melanges that are composed of limestones, radiolarian cherts, and turbidites, possessing formation characteristics of seamounts (oceanic islands/plateau). The mafic rocks in ophiolitic melanges of CCO display uniform chondrite-normalized rare earth element (REE) patterns with light REE enrichment and heavy REE depletion, no obvious Eu anomalies or negative Nb, Ta, and Ti anomalies, and primitive mantle-normalized trace element patterns with significant large-ion lithophile element enrichment, similar to those of modern OIB and the Hawaiian alkaline basalts. The OIB-type basalts and mafic rocks are considered as accreted seamount fragments in an accretionary complex of CCO and may represent plume-related magmatism within the Proto-Tethys Ocean and Paleo-Tethys Ocean. Our study provides further insights into the processes of multiple subduction and long-lasting accretionary histories with seamounts in the CCO.

Late Mesozoic granitic magmatism (158–112 Ma) are widespread in the southern margin of the North China Craton (NCC), contemporary with many world-class Mo-Au-Ag-Pb-Zn polymetallic deposits. There are abrupt changes in the elements and isotopic compositions of these granites at about 127 Ma. The early stage (158–128 Ma) granites show slightly or no negative Eu anomalies, large ion lithophile elements enriched and heavy REE depleted (such as Y and Yb), belonging to typical I-type granite. The late stage (126–112 Ma) granites are characterized by A-type and/or highly fractionated I-type granite, with higher contents of SiO2, K2O, Y, Yb and Rb/Sr ratio and lower contents of Sr, δ Eu value and Sr/Y ratio than that of the early-stage granites. Moreover, the whole rock Nd and Hf isotopic compositions of the granites younger than 127 Ma show more depleted than those of the older one. The two stages of Late Mesozoic granites were derived from a source region of the ancient basement of the southern margin of the NCC incorporated the mantle material. The late stage (126–112 Ma) granites contain more fractions of mantle material with depleted isotopic composition than the early ones. The granites record evidence for a strong crust-mantle interaction. They formed in an intracontinental extensional setting which was related to lithospheric thinning and asthenospheric upwelling in this region, which was possibly caused by westward subduction of the Paleo-Pacific plate. 127 Ma is an critical period of the transformation of the tectonic regime.

New geological, mineralogical, and geochemical data on rocks dredged in the local spreading zone of the Cayman Trough (Caribbean Sea) make it possible to use this ophiolite complex as a reference one for pull-apart structures. The ophiolites form fault-bounded narrow elongated zones. Separate magmatic complexes within these zones can be of different ages, which decrease along the strike from the flanks to the central parts. The base of the ophiolite complex is mostly composed of lherzolites, while the gabbroid complex demonstrates clear magmatic layering formed through crystallization differentiation. At the same time, the crystalline and igneous rocks define a single geochemical series, which is characterized by the accumulation of lithophile and light rare-earth elements in more differentiated varieties. The REE distribution patterns are strongly correlated with the mineral composition of the rocks. The geochemical characteristics of the ophiolites indicate their affiliation to the plume type.

The Early Cretaceous Yangshan granite is an A-type granitic intrusion that was emplaced along the eastern Jiangnan Orogen in southern Anhui Province, South China. The Yangshan intrusion mainly consists of syenite porphyry (127.0 ± 0.6 Ma) and alkali-feldspar granite porphyry (126.0 ± 1.0 Ma). As a part of Qingyang–Jiuhuashan complex intrusion, the Yangshan A-type granites have lower MgO, CaO, Co, Sr, and higher Rb, Nb, Th and HREE contents, with enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), and slightly negative Eu anomalies. However, the syenite porphyry and the alkali-feldspar granite porphyry differ in terms of zircon eHf(t) values: small variations in the syenite porphyry from − 5.5 to − 3.7, corresponding to Hf model ages (tDMC) between 1.42 Ga and 1.53 Ga, and large variations in the alkali-feldspar granite porphyry from − 6.4 to + 4.4, yielding tDMC of 0.90–1.59 Ga. While both rocks also have similar eNd(t) values ranging from − 7.02 to − 5.47, corresponding Nd model ages (TDMC) are 1.37–1.49 Ga, falling within the Hf model ages. We take these features to indicate that the Qingyang I-type granites, which are isotopically similar, and Yangshan A-type granites were originated from partial melting of Mesoproterozoic–Neoproterozoic crust, with minor juvenile crust input for the alkali-feldspar granite porphyry, followed by fractional crystallization. In combination with previous studies, we propose that the Cretaceous A-type granitic rocks formed between 135 Ma and 122 Ma, implying an important Mesozoic extensional event in eastern Jiangnan Orogen, which facilitated underplating of mantle-derived magma and crustal heating. This may have occurred in a back-arc extension in response to the drift of subduction direction of the Paleo-Pacific plate, which started as early as ~ 135 Ma ago.

The Late Mesozoic geology of the Gan-Hang Belt is characterized by extensive magmatism forming a belt of volcanic-intrusive complex. The geochronology, petrogenesis, and geodynamic setting of the Late Mesozoic magmatic rocks in the Gan-Hang Belt are still controversial. The Shengyuan volcanic Basin is located in the NW region of the belt and mainly contains crystal tuff, welded tuff, and trachyandesitic rocks. We integrate geochronological and geochemical data for these tuffs and trachyandesitic rocks, to explore the origin of these rocks and improve our understanding of the Late Mesozoic magmatic and tectonic evolution of the region. Zircon U-Pb dating shows that these samples were formed in the Early Cretaceous (135–137 Ma). All the tuffs have a pronounced A2-type geochemical signature and their chemical compositions are controlled by crystal fractionation. All trachyandesitic rocks exhibit high K2O contents and were attributed to the shoshonite series; they are characterized by arc-like trace element distribution patterns, with significant enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE) but depletion in high field-strength elements (HFSE). Moreover, all the tuffs and trachyandesitic rocks were characterized by negative whole rock eNd(t) and zircon eHf(t). An integrated interpretation of all these geochemical data leads to the conclusion that the Shengyuan trachyandesitic rocks were primarily derived from mantle materials and oceanic crust-derived melt. The Shengyuan tuffs were formed by the partial melting of the Proterozoic orthometamorphic and parametamorphic rocks. Our studies together with previous published data suggest that the Early Cretaceous A-type felsic rocks, with ages between 138 Ma and 122 Ma, occurred along the Gan-Hang Belt, indicating an important Late Mesozoic extensional event in the Belt. This event represents a back-arc tectonic setting due to the rollback of the Paleo-Pacific plate.

The Maoling gold deposit is located in the southwestern part of the Liaodong rift, NE China, and has estimated reserves of 25 t. In this paper we present the results of an investigation into the geochronology and geodynamic mechanisms of igneous activity and metallogenesis within the Maoling gold deposit. New zircon U–Pb age data, biotite 40Ar/39Ar age data, whole-rock geochemistry, and Hf isotopic analyses are presented in order to constrain the petrogenesis and mineralization of the deposit. Zircon U–Pb dating of the Wolongquan biotite monzogranite and Maoling biotite granite yielded mean ages of 194.0 ± 1.1 Ma and 196.1 ± 1.1 Ma, respectively. All the granites are characteristically high-K calc-alkaline, enriched in light rare earth elements and large ion lithophile elements, and depleted in high field strength elements, which is consistent with the geochemical characteristics of arc-type magmas. The Hf isotope characteristics indicate that the granites formed by partial melting of early Paleoproterozoic crustal material. In addition, biotite 40Ar/39Ar dating indicates that the Maoling gold deposit formed at 188.9 ± 1.2 Ma, implying that the mineralization was related to both the granite intrusions. Taking into account previous data on S–Pb–O–H isotopes and our new age data, the Maoling deposit can be classified as an intrusion-related gold deposit. Taking into account the geology of the study area and adjacent regions, we propose that the Maoling gold deposit and its associated granitic intrusions formed in a geodynamic setting that was dominated by subduction of the Paleo-Pacific Plate beneath the Eurasian continent.

The geochemical and Sr–Nd–Pb isotope properties, as well as the Laser Ablation Inductively Coupled Plasma and Mass Spectrometry (LA-ICP-MS) U–Pb zircon age, of Eğrikar Monzogranite in the eastern Pontides, are primarily investigated in this study with the aim of determining its magma source and geodynamic evolution. The U–Pb zircon age obtained from Eğrikar Monzogranite is 78 ± 1.5 Ma, thereby reflecting the age of monzogranite. The I-type Eğrikar Monzogranite comprises quartz, plagioclase (An35–45), orthoclase, muscovite, and biotite. The geochemical analyses of the Eğrikar Monzogranite indicate being medium K calc-alkaline, peraluminous, and resembling magmatic arc granite. The Eğrikar Monzogranite is enriched in large ion lithophile elements and light rare earth elements relative to high field strength elements. Chondrite-normalized rare earth element patterns have concave upward shapes (LaN/YbN 2.47–8.58) with pronounced negative Eu anomalies (EuN/Eu* = 0.29–0.65). Initial εNd(i) values vary between 1.85 and 2.18 and initial 87Sr/86Sr values between 0.7048 and 0.7067. Fractionation of plagioclase, hornblende, and apatite played an important role in the evolution of Eğrikar Monzogranite. The crystallization temperatures of the melts ranged from 770°C to 919°C based on zircon and apatite saturation temperatures. The geochemical and isotopic data suggest being generated by the partial melting of mafic lower crustal sources.

The widespread tectonic and magmatic events in Southeast China during the Mesozoic were accompanied by large-scale metallogenesis. Here, we investigate the petrology, geochemistry, and zircon U–Pb age of the porphyry dykes in relation to the gold mineralization at Dongyang deposit in the Fujian Province. The geochemical data show silica-rich and Mg- and Ca-poor A-type granite affinity for the dykes. The rocks have high concentrations of Light Rare Earth Elements (LREE) and Large Ion Lithophile Elements (LILE) and relatively low contents of Heavy Rare Earth Elements (HREE) and High Field Strength Element (HFSE). They display (La/Yb)N and (La/Sm)N values in the range of 5.7 to 31.4 and 6.0 to 8.3, respectively, with negative anomalies of Ba, Nb, Ta, Sr, Zr, Eu, and Ti and positive Ce anomaly. The source magma for the dykes was derived from a mixture of partially melted Al-rich crustal material, with an input of mantle components. We present sensitive high-resolution ion microprobe zircon U–Pb data from the dykes, which show emplacement ages in the range of 158 to 162 Ma, coinciding with the onset of the Yanshanian magmatism in Southeast China. Integrating the data obtained from studies on geology, geochronology and petro-geochemistry, we suggest that the dykes played role in controlling the gold mineralization, and the magmatism and gold mineralization are the response of continental lithosphere thinning in Southeast China triggered by the subduction of the ancient Pacific Ocean Plate.

Distinctive magmatic-hydrothermal, tourmaline-rich features have developed in the Heemskirk and Pieman Heads granites from western Tasmania, Australia. They are categorized as tourmaline-rich patches, orbicules, cavities, and veins, based on their distinctive morphologies, sizes, mineral assemblages, and contact relationships with host granites. These textural features occur in discrete layers in the roof zone of granitic sills within the Heemskirk and Pieman Heads granites. Tourmaline patches commonly occur below a tourmaline orbicule-rich granitic sill. Tourmaline-filled cavities have typically developed above the tourmaline-quartz orbicules in the upper layer of the white phase of the Heemskirk Granite. Tourmaline-quartz veins penetrate all exposed levels of the granites, locally cutting tourmaline orbicules and cavities.The tourmalines are mostly schorl (Fe-rich) and foitite, with an average end-member component of schorl(45) dravite(6) tsilaisite(1) uvite(0) Fe-uvite(3) foitite(31) Mg-foitite(4) olenite(10). Element substitutions of the tourmalines are controlled by FeMg-1, Al-Y(X)square(R2+Na)(-1), and minor (AlO)-Al-Y(R2+OH)(-1) (where R2+ = Fe2+ + Mg2+ + Mn2+) exchange vectors. Several trace elements in tourmaline have consistent chemical evolutions grouped from tourmaline patches, through orbicules and cavities, to veins. There is a progressive decrease of most transition and large ion lithophile elements, and a gradual increase of most high-field strength elements. These compositional variations in the different tourmaline-rich features probably relate to element partitioning occurring in these phases due to volatile exsolution and fluxing of aqueous boron-rich fluids that separated from the granitic melts during the emplacement of S-type magmas into the shallow crust (4 to 5.5 km).Tourmalines from the Heemskirk Granite are enriched in Fe, Na, Li, Be, Sn, Ta, Nb, Zr, Hf, Th, and rare earth elements relative to the tourmalines from the Pieman Heads Granite, but depleted in Mg, Mn, Sc, V, Co, Ni, Pb, Sr, and most transition elements. These results imply that bulk compositions of the host granites exert a major control on the chemical variations of tourmalines. The trace element compositions of tourmalines from the Sn-mineralized Heemskirk Granite are different from those of the barren Pieman Heads Granite. Trace element ratios (e.g., Zn/Nb, Co/Nb, Sr/Ta, and Co/La) and Sn concentrations in tourmaline can distinguish the productive Heemskirk Granite from the barren Pieman Heads Granite.

The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is the second largest porphyry region in Asia and hence has attracted considerable attention of the geologists. In this contribution, we report the zircon U–Pb ages, major and trace element geochemistry as well as Sr–Nd isotopic data for the ore-related porphyries of the Sarycheku and Kalmakyr deposits. The zircon U–Pb ages (Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)) of ore-bearing quartz monzonite and granodiorite porphyries from the Kalmakyr deposit are 326.1 ± 3.4 and 315.2 ± 2.8 Ma, and those for the ore-bearing granodiorite porphyries and monzonite dike from the Sarycheku deposit are 337.8 ± 3.1 and 313.2 ± 2.5 Ma, respectively. Together with the previous ages, they confine multi-phase intrusions from 337 to 306 Ma for the Almalyk ore cluster. Geochemically, all samples belong to shoshonitic series and are enriched in large-ion lithophile elements relative to high field strength e...

Palaeogene and Neogene volcanic rocks are widespread on the Biga Peninsula of Northwest Turkey. These rocks were formed during the Eocene, Oligocene–Miocene, and late Miocene, and the early Miocene Şapçı volcanic rocks in the Balıkesir area consist of andesitic lava flows and associated pyroclastics. Temperatures, pressures, and oxygen fugacities calculated for the hornblendes in these andesitic rocks are 903–930°C, 3.3–4.8 kbar, and –9.91 to –11.88, respectively, and for the biotites they are 755–788°C, 1.30–1.74 kbar, and –14.88 to –13.98, respectively. SHRIMP U–Pb dating of zircons from three andesite samples gave ages of 22.72 ± 0.19, 22.97 ± 0.23, and 18.72 ± 0.17 Ma (early Miocene), and these are regarded as crystallization ages. Geochemical analyses show that the volcanic rocks are mainly high-K and calc-alkaline, and have high contents of large-ion lithophile elements and low contents of high-field strength elements, revealing that they evolved from parental magmas that were derived from an enriched subcontinental lithospheric mantle source. The chondrite-normalized rare earth element patterns of the rocks are concave upwards with LaCN/LuCN = 11.9–21.2 and EuCN/Eu* = 0.84–0.92, implying significant fractional crystallization of hornblende during their evolution. According to the petrological data with regional geology, Neogene magmatic activity on the Biga Peninsula has a post-collisional feature, and was closely related to slab break-off geodynamic model after collision of Tauride–Anatolide Block and Sakarya continent.

The Earth formed by accretion of Moon- to Mars-size embryos coming from various heliocentric distances. The isotopic nature of these bodies is unknown. However, taking meteorites as a guide, most models assume that the Earth must have formed from a heterogeneous assortment of embryos with distinct isotopic compositions. High-precision measurements, however, show that the Earth, the Moon and enstatite meteorites have almost indistinguishable isotopic compositions. Models have been proposed that reconcile the Earth-Moon similarity with the inferred heterogeneous nature of Earth-forming material, but these models either require specific geometries for the Moon-forming impact or can explain only one aspect of the Earth-Moon similarity (that is, 17O). Here I show that elements with distinct affinities for metal can be used to decipher the isotopic nature of the Earth's accreting material through time. I find that the mantle signatures of lithophile O, Ca, Ti and Nd, moderately siderophile Cr, Ni and Mo, and highly siderophile Ru record different stages of the Earth's accretion; yet all those elements point to material that was isotopically most similar to enstatite meteorites. This isotopic similarity indicates that the material accreted by the Earth always comprised a large fraction of enstatite-type impactors (about half were E-type in the first 60 per cent of the accretion and all of the impactors were E-type after that). Accordingly, the giant impactor that formed the Moon probably had an isotopic composition similar to that of the Earth, hence relaxing the constraints on models of lunar formation. Enstatite meteorites and the Earth were formed from the same isotopic reservoir but they diverged in their chemical evolution owing to subsequent fractionation by nebular and planetary processes.

Femtosecond laser ionization time-of-flight mass spectrometry (fs-LI-TOFMS) is introduced for the three-dimensional elemental analysis of a Nantan meteorite. Spatially resolved multielemental imaging of major and minor compositions in a meteorite are presented with a lateral resolution of 50 μm and a depth resolution of 7 μm. Distinct 3D distributions of siderophile, lithophile, and chalcophile elements are revealed. Co and Ni are highly siderophile (Iron-loving), mainly enriched in the metal phase. Cr, Cu, V, and Mn are enriched in the sulfide for their chalcophile (S-loving) tendency. S, P, and C aggregate together in the analytical volume. Silicate inclusion, containing lithophile elements of Al, Ca, Mg, K, and so on, is embedded within the metal phase for the immiscibility between silicate inclusion and the melted metal phase. These 3D distributions of elements aid the exploration of the formation and evolution of the meteorite. They also reveal the feasibility of fs-LI-TOFMS as a versatile tool for 3D imaging.

Appinites are commonly derived from a mantle source and are potentially significant in constraining the tectonic nature and evolution of ancient orogens, yet they have received little attention because of their limited outcrop. Here we investigate the newly identified appinitic rocks from the Laoniushan complex in the eastern Qinling Orogen. The appinites are composed of coarse-grained hornblendite, medium- and fine-grained hornblende-gabbro, and diorite porphyrite in the field occurrence. Winthin the appinitic rocks, the hornblendite displays features of cumulates. This study presents LA-ICP-MS zircon U-Pb data, mineral chemistry and whole rock geochemistry of the appinites. Zircons in the mafic to ultramafic rocks yield a U-Pb age of 152 ± 1Ma. The geochemistry of the rocks displays: lower SiO2, higher Fe2O3T and MgO contents, relatively flat chondrite normalized REE patterns with slight enrichment in light REE and a minor negative Eu anomaly; enrichment in large-ion lithophile elements(LILE, e.g. Rb, Ba, Sr and P), and depletion in high field strength elements(HFSE, e.g. Nb, Zr, Hf and Ti). Such geochemical features, together with crust-like bulk Sr-Nd isotopic compositions(initial 87Sr/86Sr ratios of 0.7057–0.7072, eNd(t) = −17.2 to −9), suggest that the Laoniushan appinites likely originated from an ancient metasomatised mantle, followed by fractional crystallization in the petrogenetic process. The studied appinites were most likely generated in an intracontinental extensional environment in the Late Mesozoic.

International audience; The Earth's major heat and mass fluxes are output from the mantle to surface via mid-ocean-ridge-basalt (MORB) magmatism. The variations of MORBs are determined both by the heterogeneity of mantle source and the melt migration processes from mantle source to seafloor. However, before the MORB magmas enter crust, the role of the major melt migration passageways within the mantle (dunite channel systems) in regulating the compositions of MORBs has been rarely evaluated, especially from the perspective of Re-Os isotopes. Here, we report new Re-Os isotopic compositions of base-metal sulfides (BMS), chromites and dunites from dunite lenses with low spinel Cr# [Cr3+/(Cr3++Al3+) ≤0.66] (products of interaction between MORB-like melts and upper-mantle harzburgites) from the Zedang ophiolite (South Tibet). Rhenium-Os isotopic compositions of low-Cr# dunites from the Samail and Wadi Tayin massifs (typical MOR segments) of the Oman ophiolite are also shown for comparison to reveal the melt plumbing processes at mantle depths beneath mid-ocean ridges. Mineralogical evidence suggests that the Zedang sulfides and desulfurized alloy portions were originally precipitated as monosulfide solid solutions. The highly variable 187Os/188Os initial ratios (0.1191-0.1702) and low 187Re/188Os (

Trace elements and Hg isotopic composition were investigated in mineralized rocks, barren rocks, and mineral soils in the Xianfeng prospect, a shallow buried epithermal gold deposit in northeastern China, to understand whether this deposit has left a diagnostic geochemical fingerprint to its weathered horizon. All the rocks and soils display congruent patterns for immobile elements (large ion lithophile elements, high field strength elements, and rare earth elements), which reflect the subduction-related tectonic setting. Both mineralized rocks and soils showed common enrichment of elemental suite As–Ag–Sb–Hg, suggesting that the Xianfeng gold deposit has released these elements into its weathered horizon. Similar mercury isotopic composition was observed between mineralized rocks (δ202Hg: −0.21 ± 0.70‰; Δ199Hg: −0.02 ± 0.12‰; 2SD) and barren rocks (δ202Hg: −0.46 ± 0.48‰; Δ199Hg: 0.00 ± 0.10‰; 2SD), suggesting that mercury in the Xianfeng deposit is mainly derived from the magmatic rocks. Mineralized soils (δ202Hg: −0.44 ± 0.60‰; −0.03 ± 0.14‰; 2SD) and barren soils (δ202Hg: −0.54 ± 0.68‰; Δ199Hg: −0.05 ± 0.14‰; 2SD) displayed congruent Hg isotopic signals to the underlying rocks, suggesting limited Hg isotope fractionation during the release of Hg from ore deposit to soils via weathering. This study reveals evidence of a simple and direct geochemical link between this shallow buried hydrothermal deposit and its weathered horizon, and highlights that the weathering of shallow-buried hydrothermal gold deposits can release a substantial amount of heavy metals (e.g. Hg, As and Sb) to surface soil.

The Shulan area in Jilin Province is a part of the Lesser Xing&rsquo, an&ndash, Zhangguangcai Range polymetallic ore belt, which is an important Cu&ndash, Mo ore region of northeast China. The discovery of three large Mo ore deposits (Fu&rsquo, anbu, Chang&rsquo, anbu, and Jidetun) highlights its potential for porphyry Mo ore deposits. Here we investigated the tectonic setting and mineralization of Mo ore deposits in the Shulan area, based on comparative study of the Fu&rsquo, anbu, and Jidetun deposits. The ore-controlling structures are NE&ndash, SW- and NW&ndash, SE-trending faults. The main ore mineral in all three deposits is molybdenite. The ore bodies are all hosted in granites, have a stratiform or lenticular shape, and have strongly altered wall rocks. These observations indicate the Mo deposits in the Shulan area are typical porphyry Mo deposits. All were formed during the early Yanshanian (199.6&ndash, 133.9 Ma). Biotite adamellites from the Chang&rsquo, anbu deposit yield a U&ndash, Pb age of 182.10 &plusmn, 1.20 Ma. Molybdenites from the Fu&rsquo, anbu and Jidetun deposits have Re&ndash, Os isochron ages of 166.9 &plusmn, 6.7 and 169.1 &plusmn, 1.8 Ma, respectively. Quartz and ore minerals were analysed for H&ndash, O and S&ndash, Pb isotopes, respectively. The results suggest the ore-forming materials were predominantly of upper-mantle origin, with secondary contributions from the lower crust. The ore-hosting granites have high concentrations of SiO2 (66.67&ndash, 75.43 wt.%) and Al2O3 (12.91&ndash, 16.44 wt.%), low concentrations of MgO (0.09&ndash, 1.54 wt.%), and Ritman index (&sigma, = K2O + Na2O)2/(SiO2 &minus, 43)) ratios of 2.09&ndash, 2.57. The granites are enriched in large-ion lithophile elements and depleted in high-field-strength elements, and have negative Eu anomalies. The ore-hosting rocks are geochemically similar to granites in northeastern China that were generated in a collisional orogeny. We conclude that early Yanshanian (199.6&ndash, 133.9 Ma) mantle&ndash, crust-derived magmatism caused by the subduction of the Palaeo-Pacific Plate was the main source of Mo deposits in the Shulan area.

Chargar area is located in the southern border of Tarom subzone within the Alborz magmatic belt of NW Iran. Two types of intrusions, mainly present in the southern part of the area, have been identified. These bodies intruded into the Karaj Formation volcanic and volcaniclastic rocks. Type-I intrusions occur in the south and include two magmatic bodies: (a) Gabbro-pyroxene quartz monzodiorite-quartz monzodiorite and (b) quartz syenite. Type-II crops out in the west and has a gabbro – gabbro-diorite composition. Geochemically, Chargar intrusive rocks belong to the high-K calc-alkaline to shoshonitic series and are classified as I-type and metaluminous granitoids. These intrusive rocks show insignificant different distribution patterns of trace elements and REEs, but generally they are characterized by highly enriched large ion lithophile elements (e.g., K and Ba) and depleted Nb, similar to that of continental arc magmatism. Type-I intrusions and Type-II mafic intrusion were originated from mantle source with amphibole-bearing spinel peridotite composition. These intrusions formed in a continental arc to post-collisional tectonic setting.

SM and FJ are grateful to the Carnegie Institution of Washington for funding via the Carnegie Postdoctoral Fellowship programme which supported their time at the Geophysical Laboratory and the Department of Terrestrial Magnetism, respectively. FMM acknowledges funding from NASA’s Cosmochemistry program as well as NASA’s Planetary Science Research Program. SM also acknowledges funding from the NERC (NE/PO12167/1). The petrogenesis and relationship of diamondite to well-studied monocrystalline and fibrous diamonds are poorly understood yet would potentially reveal new aspects of how diamond-forming fluids are transported through the lithosphere and equilibrate with surrounding silicates. Of 22 silicate- and oxide-bearing diamondites investigated, most yielded garnet intergrowths (n = 15) with major element geochemistry (i.e. Ca–Cr) classifying these samples as low-Ca websteritic or eclogitic. The garnet REE patterns fit an equilibrium model suggesting the diamond-forming fluid shares an affinity with high-density fluids (HDF) observed in fibrous diamonds, specifically on the join between the saline–carbonate end-members. The δ13C values for the diamonds range from − 5.27 to − 22.48‰ (V-PDB) with δ18O values for websteritic garnets ranging from + 7.6 to + 5.9‰ (V-SMOW). The combined C–O stable isotope data support a model for a hydrothermally altered and organic carbon-bearing subducted crustal source(s) for the diamond- and garnet-forming media. The nitrogen aggregation states of the diamonds require that diamondite-formation event(s) pre-dates fibrous diamond-formation and post-dates most of the gem monocrystalline diamond-formation events at Orapa. The modelled fluid compositions responsible for the precipitation of diamondites match the fluid-poor and fluid-rich (fibrous) monocrystalline diamonds, where all grow from HDFs within the saline-silicic-carbonatitic ternary system. However, while the nature of the parental fluid(s) share a common lithophile element geochemical affinity, the origin(s) of the saline, silicic, and/or carbonatitic components of these HDFs do not always share a common origin. Therefore, it is wholly conceivable that the diamondites are evidence of a distinct and temporally unconstrained tectono-thermal diamond-forming event beneath the Kaapvaal craton. Publisher PDF

The Geza arc is an important part of the Yidun arc belt and porphyry metallogenic zone in the Sanjiang region, Southwestern China. In this paper, we report on new laser-ablation inductively coupled plasma–mass spectroscopy zircon U–Pb age and bulk geochemical and Hf isotopic data of the Tongchanggou granodioritic porphyries from the Geza arc. The results indicate that these intrusions were emplaced in the Late Cretaceous (87.6 ± 0.6–83.6 ± 1.1 Ma). The intrusive rocks have SiO2, Al2O3, and K2O + Na2O contents of 62.51–72.86, 11.43–16.30, and 5.32–7.81 wt%, respectively, similar to those of high-K calc-alkaline rock. They are enriched in large-ion lithophile elements (e.g., K, U, Th, Rb, Ba, and Sr) and light rare-earth elements (LREE (light rare-earth elements)/HREE (heavy rare-earth elements) = 16.96–24.78), but depleted in high-field-strength elements (e.g., Nb, Ta, P, and Ti) and HREE, with a slightly negative Eu anomaly (δEu = 0.72–0.89). The intrusions show uniformly negative eHf (t) values between − 9.55 and − 3.49. These elemental geochemical and Hf isotopic data indicate that the Tongchanggou porphyries were mainly derived from partial melting of the delaminated lower crust in an extensional setting at the post-collisional stage. The collision-induced upwelling of the lithospheric mantle led to the partial melting of the crust and formed the potassium-rich and Mo-bearing parental magma. Magma rising and intruding along the deep faults eventually resulted in the Late Cretaceous tectonic–magmatic and Mo-polymetallic mineralization in Geza area.

The crust–mantle transition of the Khantaishir ophiolite in western Mongolia is well exposed. The mantle section shows an up to 4 km thick refractory harzburgitic mantle with local dunite channels and lenses. Towards its top, the mantle is increasingly replaced by discrete zones of pyroxenite, which form a kilometre-wide and hundreds of metres-thick horizon at the contact with the overlying crustal section. The plutonic crustal section is composed of gabbros, gabbronorites, tonalites and minor plagiogranites. The lower part of the crustal section is intercalated with pyroxenite lenses, forming a layered sequence, whereas the upper part is cut by volcanic dykes associated with the overlying basalt–andesitic volcanic section. Most of the ultramafic rocks and gabbronorites show a depletion in high field strength elements and positive anomalies for Sr and Pb, whereas gabbros, tonalites and plagiogranites are enriched in large ion lithophile elements and have slightly enriched rare earth element patterns. Non-modal fractional melting models indicate that the most depleted harzburgites of the ophiolite originated after 20–25% of melt extraction from the mantle. Leached minerals and whole-rocks from the crust–mantle transition of the Khantaishir ophiolite define a Sm–Nd isochron at 540 ± 12 Ma, which is interpreted as the formation age of the crust–mantle transition. Additionally, minerals and whole-rocks display a restricted εNd(t=540 Ma) composition (+3·5 to +7·0) and a large scatter in εSr(t=540 Ma) (–19·8 to +14·2). Clinopyroxenes in the crust–mantle transition rocks indicate that they were in equilibrium with a boninitic-like melt, consistent with the lavas observed in the volcanic section of the ophiolite. It is therefore inferred that the Khantaishir ophiolite represents a slice of an incipient oceanic island-arc formed in a suprasubduction environment.

Field, petrographic and geochemical evidence shows the occurrence of ferruginised metapelites (FMP) in the Kazaure Schist Belt (KZSB). The KZSB consists predominantly of quartzites, pelitic metasediments, and metaconglomerates. Minor rocks includes metavolcanics and iron formations (Banded Iron Formation and ferruginised metapelites). The FMP occurs as narrow bands associated with quartzites and phyllites. Magnetite as euhedral to subhedral crystals together with subordinate anhedral hematite forms the Fe band. The Fe content of the FMP (14.54 – 82.8 %) is comparable to that of banded iron formations in the schist belt. It contains lesser amounts of Mn (0.07 – 17.83 %), Ca (0.067 – 1.25%), and the lithophile elements average values: K (1.21 ppm); Rb (89.89 ppm); Sr (190.78 ppm). It is envisaged that the FMP developed from the alteration of the metasediments entrapped as a kind of tectonic mélange as a result of late tectonic brittle deformation and activity of fluids rich in iron.Keywords: Banded Iron Formation, ferruginised metapelites, Oxide facies, Tectonic mélange, Silicate facies.

The nature and origin of the early Yanshanian granitoids, widespread in the South China Block, shed light on their geodynamic setting, however, understanding their magmatism processes remains a challenge. In this paper, we present both major and trace elements of bulk rock, Sr&ndash, Nd&ndash, Pb isotopic geochemistry, and zircon U&ndash, Pb&ndash, Hf isotopes of the low Sr and high Yb A2-type granites, which were investigated with the aim to further constrain their petrogenesis and tectonic implications. Zircon U&ndash, Pb dating indicates that these granites were emplaced at ca. 153 Ma. The granites are characterized by high SiO2 (&gt, 74 wt.%) and low Al2O3 content (11.0 wt.%&ndash, 12.7 wt.%, &lt, 13.9 wt.%). They are enriched in large ion lithophile elements (LILEs) (e.g., Rb, Th, U, and K) and Yb, but depleted in high field-strength elements (HFSEs) (e.g., Nb, Ta, Zr and Hf), Sr, Ba P, Ti and Eu concentrations. They exhibit enriched rare earth elements (REEs) with pronounced negative Eu anomalies. They have &epsilon, Nd(t) values in a range from &minus, 6.5 to &minus, 9.3, and a corresponding TDM model age of 1.5 to 1.7 Ga. They have a (206Pb/204Pb)t value ranging from 18.523 to 18.654, a (207Pb/204Pb)t value varying from 15.762 to 15.797, and a (208Pb/204Pb)t value ranging from 39.101 to 39.272. The yield &epsilon, Hf(t) ranges from &minus, 6.1 to &minus, 2.1, with crustal model ages (TDMC) of 1.3 to 1.6 Ga. These features indicate that the low Sr and high Yb weakly peraluminous A2-type granites were generated by overlying partial melting caused by the upwelling of the asthenosphere in an extensional tectonic setting. The rollback of the Paleo-Pacific Plate is the most plausible combined mechanism for the petrogenesis of A2-type granites, which contributed to the Sn&ndash, W polymetallic mineralization along the Shi-Hang zone in South China.

The aim of the present study was the paleoenvironmental reconstruction of the prevailing environment under which the Lwamondo and Zebediela kaolin deposits were formed. Hence, this study reports deuterium and oxygen stable isotope values and trace and rare earth element concentrations for two samples of kaolin. Upper continental crust-normalised trace-element patterns reveal that large ion lithophile elements and high-field-strength elements are generally depleted in Lwamondo and Zebediela kaolins, whereas transition trace elements are generally enriched in these kaolins. Upper continental crust-normalised rare earth element (REE) patterns show that there is a slight enrichment of heavy REEs (HREEs) compared to light REEs (LREEs) in these kaolins. The &delta, 18O and &delta, D stable isotope values for kaolinite from Lwamondo ranged from 17.4&permil, to 19.1&permil, and from &minus, 54&permil, to 84&permil, respectively, whereas those values for kaolinite from Zebediela varied from 15.6&permil, to 17.7&permil, 61&permil, to &ndash, 68&permil, for &delta, D, respectively. The REE patterns and the content of other trace elements indicate ongoing kaolinitisation in the Lwamondo and Zebediela kaolins with minimum mineral sorting. The sources of the kaolins varied from basic to acidic and these were derived from an active margin tectonic setting. Lwamondo kaolin was deposited in an oxic environment whereas Zebediela kaolin was deposited under suboxic/anoxic conditions. Based on the &delta, D values of the kaolinite, they formed in a supergene environment at temperatures generally below 40 &deg, C.

The recently discovered Weilasituo Sn-polymetallic deposit in the Great Xing&rsquo, an Range is an ultralarge porphyry-type deposit. The mineralization is closely associated with an Early Cretaceous quartz porphyry. Analysis of quartz porphyry samples, including zircon U-Pb dating and Hf isotopies, geochemical and molybdenite Re-Os isotopic testing, reveals a zircon U-Pb age of 138.6 &plusmn, 1.1 Ma and a molybdenite Re-Os isotopic age of 135 &plusmn, 7 Ma, suggesting the concurrence of the petrogenetic and metallogenic processes. The quartz porphyry has high concentrations of SiO2 (71.57 wt %&ndash, 78.60 wt %), Al2O3 (12.69 wt %&ndash, 16.32 wt %), and K2O + Na2O (8.85 wt %&ndash, 10.44 wt %) and A/CNK ratios from 0.94&ndash, 1.21, is mainly peraluminous, high-K calc-alkaline I-type granite and is relatively rich in LILEs (large ion lithophile elements, e.g., Th, Rb, U and K) and HFSEs (high field strength elements, e.g., Hf and Zr) and relatively poor in Sr, Ba, P, Ti and Nb. The zircon &epsilon, Hf(t) values range from 1.90 to 6.90, indicating that the magma source materials were mainly derived from the juvenile lower crust and experienced mixing with mantle materials. Given the regional structural evolution history, we conclude that the ore-forming magma originated from lower crust that had thickened and delaminated is the result of the subduction of the Paleo&ndash, Pacific Ocean. Following delamination, the lower crustal material entered the underlying mantle, where it was partially melted and reacted with mantle during ascent. The deposit formed at a time of transition from post-orogenic compression to extension following the subduction of the Paleo&ndash, Pacific Ocean.

Detailed geochemical and U-Pb studies of two diabases (Luoji and Cuiyi) from the Luoji area have been undertaken. The diabases are high-K calc-alkaline and belonging to the tholeiitic series, enriched in large ion lithophile elements, Ti, Zr and light rare earth elements, and depleted in high field strength elements. These characteristics are different from the oceanic island basalt but highly consistent with the continental rift basalt, indicating the Luoji and Cuiyi diabases are the products of the intracontinental rift related to the initial opening of the Ganzi-Litang Ocean. The Luoji and Cuiyi diabases originated from an enriched mantle source with a small degree of crustal contamination during their emplacement. Zircon U-Pb ages show that the Luoji and Cuiyi diabases were emplaced at 293.4 +/- 5.4Ma. Therefore, we propose that the time of initial rifting of the Ganzi-Litang Ocean occurred during the very Early Permian.

Nitrogen is a key constituent of our atmosphere and forms the basis of life, but its early distribution between Earth reservoirs is not well constrained. We investigate nitrogen partitioning between metal and silicate melts over a wide range of conditions relevant for core segregation during Earth accretion, i.e. 1250–2000 °C, 1.5–5.5 GPa and oxygen fugacities of ΔIW-5.9 to ΔIW-1.4 (in log units relative to the iron–wüstite buffer). At 1250 °C, 1.5 GPa, DN metal melt/silicate melt ranges from 14 ± 0.1 at ΔIW-1.4 to 2.0 ± 0.2 at ΔIW-5, N partitioning into the core forming metal. Increasing pressure has no effect on DN metal melt/silicate melt, while increasing temperature dramatically lowers DN metal melt/silicate melt to 0.5 ± 0.15 at ΔIW-4. During early core formation N was hence mildly incompatible in the metal. The partitioning data are then parameterised as a function of temperature and oxygen fugacity and used to model the evolution of N within the two early prevailing reservoirs: the silicate magma ocean and the core. Depending on the oxidation state during accretion, N either behaves lithophile or siderophile. For the most widely favoured initially reduced Earth accretion scenario, N behaves lithophile with a bulk partition coefficient of 0.17 to 1.4, leading to 500–700 ppm N in closed-system core formation models. However, core formation from a magma ocean is very likely accompanied by magma ocean degassing, the core would thus contain ≤100 ppm of N, and hence, does not constitute the missing N reservoir. Bulk Earth N would thus be 34–180 ppm in the absence of other suitable reservoirs, >98% N of the chondritic N have hence been lost during accretion., Earth and Planetary Science Letters, 510, ISSN:0012-821X, ISSN:1385-013X

During the early Mesozoic Era there was intense magmatic activity near Hainan Island, South China. As a result, the granites of Hainan Island provide information on, and are suitable material to potentially improve understanding of the Cretaceous tectonic environment of the northern margin of the South China Sea. The Gaofeng and Baocheng intrusions are composed mainly of medium- to fine-grained biotite adamellite (Baocheng) and granodiorite (Gaofeng). The two intrusions yielded U–Pb LA-ICP-MS zircon ages of 107.7 ± 6.1 Ma (Gaofeng) and 105.8 ± 2.4 Ma (Baocheng). Regarding the major elements, the Gaofeng and Baocheng intrusions had medium Si and alkali contents and high Ca, Mg, and Al contents, with an aluminum saturation index of 0.95–1.03 and 1.05–1.30. The trace element and rare earth element (REE) characteristics showed that the two intrusions have intense heavy REE/light REE (HREE/LREE) fractionation, LREE enrichment, HREE depletion, and weak negative Eu anomalies. The intrusions were enriched in high field-strength elements and depleted in large ion lithophile elements. These geochemical characteristics indicate that the Hainan Province was in a tectonic subduction environment in the late Yanshanian period. Multiple geochemical characteristics demonstrate that the granites in the Hainan Province were formed by a different mechanism and in a different setting from those in Fujian and Zhejiang. The late Mesozoic granites of Fujian and Zhejiang were formed by the Western Pacific subduction. However, Hainan Island was under an arc environment formed by the northward subduction of the Tethyan-South China Sea during the Cretaceous leading to emplacement of the Gaofeng and Baocheng intrusions.

Heterogeneity in the lithophile isotopic compositions of ocean island basalts (OIBs) has long been ascribed to the incorporation of recycled materials into the plume source. OIB heterogeneity indicates that plumes do not sample a pristine primordial reservoir, but rather sample an inhomogeneous mixture of primordial and recycled material generated by convective processes over Earth history. Here we present a synthesis of new insights into the characteristics and nature of the plume mantle source. Recent high precision noble gas data demonstrate that the origin of the reservoir supplying noble gases to plumes is fundamentally distinct from that of the mid-ocean ridge basalt (MORB) mantle reservoir: the two reservoirs cannot be related simply by differential degassing or incorporation of recycled atmospheric volatiles. Based on differences observed in the extinct 129I-129Xe system (t1/2 of 15.7 Ma), the mantle source supplying noble gases to plumes differentiated from the MORB source within ~100 Ma of the start of the Solar System, and the two sources have not been homogenized by 4.45 Ga of mantle convection. Thus, the 129I-129Xe data require a plume source that has experienced limited direct mixing with the MORB source mantle. Analysis of mantle source Xe isotopic compositions of plume-influenced samples with primordial He and Ne indicates that the plume source Xe budget is dominated by regassed atmospheric Xe. He and Ne isotopes are not sensitive to regassing due to low overall concentrations of He and Ne in recycled material relative to primordial material. Therefore, plume-influenced samples with primitive He and Ne isotopic compositions do not necessarily reflect sampling of pristine primordial mantle and the lithophile compositions of these samples should not be taken to represent undifferentiated mantle. In addition to recycled atmospheric Xe, the plume mantle source exhibits high ratios of Pu-fission Xe to U-fission Xe. The high proportion of Pu-fission Xe independently confirms a low extent of degassing of the plume source relative to the MORB source. Heavy noble gases illustrate that the mantle reservoir sampled by plumes is fundamentally distinct from the MORB mantle and reflects ongoing degassing of, and incorporation of recycled material into, an ancient (>4.45 Ga) primordial source. If plumes are derived from large low shear-wave velocity provinces (LLSVPs), then these seismically-imaged structures are ancient and long-lived.

Anhydrous, medium/coarse-grained spinel bearing mantle xenoliths from the Subei Basin, Eastern China have mineral arrangements that reflect low energy geometry. Because of clinopyroxene modal contents, they are grouped into cpx-rich lherzolites (cpx ≥ 14percentage), lherzolites (8 5My, based on modelled H2O solid-solid diffusion rate) the occurrence of the last melting episode. Keywords: Water contents, Fertile mantle, Melting models, Water diffusion, Asthenosphere/lithosphere

The Miocene Sungun porphyry Cu–Mo systems, located in Azerbaijan belt, NW Iran, is associated with the high-Sr/Y magmas, which were engendered in a post-collisional setting. However, the petrogenesis of these fertile magmas and their mineralisation are still unknown. In this study, we present whole-rock major-trace elements, zircon U–Pb dating and the Lu–Hf isotopes in the ore-forming porphyries of the Sungun porphyry systems. The corresponding results showed that the samples were rich in large-ion lithophile elements and poor in high-field-strength elements; moreover, they presented both high K2O (2.4–3.5 wt%) and Sr (727–770 ppm) and low Y (11–14 ppm) contents. The zircon U–Pb age of the Sungun porphyry was ~19 Ma, with positive eHf(t) ratios (5.5–11.8) and young TDM2 ages between 322 and 705 Ma. Additionally, the Sungun high-Sr/Y porphyries contained anhydrites (CaSO4); and had high zircon Ce4+/Ce3+ ratios (33–728), relatively low zircon saturation temperatures (620–804 °C), and plagioclases with excess Al content. Overall, these evidences suggest that a water-fluxed melting of the subduction-modified juvenile lower crust might have generated a high oxygen fugacity, leading to the formation of the hydrous and S-rich Sungun fertile magmas in the NW Urumieh–Dokhtar magmatic Arc.

The petrogenesis of continental mafic rocks that are enriched in large-ion lithophile elements (LILE) and that have enriched Sr–Nd–Hf isotope compositions is debated, with some models suggesting an enriched mantle source and others arguing for crustal contamination. Crustal contamination has generally not been favored as numerical models indicate that this would require the addition of significant amounts of crustal materials. Here we present the first detailed study of the oxygen isotope composition of zircons from representative early Paleozoic mafic, intermediate, and felsic magmatic rocks in the South China Block (SCB), and combine this information with available geochemical data to re-examine whether crustal contamination or an enriched mantle source is the principal cause of the crustal geochemical signatures in these rocks. Zircon grains in the high-MgO mafic rocks (MgO > 8 wt%) with low eNd(t) values (

The study presents new zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb ages and in situ zircon Hf isotopic data for representative Dagayin granites in the southern Great Xing'an Range (SGXR). New data provide insight into the evolution of magmatism in the SGXR. The zircon U–Pb analysis yielded 156.8 ± 1.2 and 155.9 ± 0.7 Ma for the Dagayin granites. The granites contain 77.0–74.2 wt% SiO2, 13.2–11.4 wt% Al2O3, 3.9–2.9 wt% Na2O, 4.6–3.5 wt% K2O, and 0.5–0.1 wt% MgO, are metaluminous to peraluminous and high-K calc-alkaline rocks. The granites also enriched the large ion lithophile elements (LILE; e.g., Rb, Th, and U) and depleted in Ba, Sr, P, Ti, and Nb. Zircons grains within the Dagayin granite yield eHf(t) values of 7.5 to 9.4 and TDM2 model ages of 728–607 Ma. Geochemical characteristics and zircon Hf isotopic data indicate the magmas were generated from the partial melting of juvenile crustal material originating from the depleted mantle. The Dagayin granites are compositionally similar to abundant mineralization-related granitoids in the SGXR, suggesting the Dagayin pluton may be prospective for exploring Pb–Zn–Ag or Mo mineralization. In the Late Jurassic to Early Cretaceous, the SGXR was under an intracontinental extensional environment, relating to the superimposed subduction of the Mongol-Okhotsk plate beneath the Central Mongolia Massif, and the Paleo-Pacific oceanic beneath the Central Mongolia Massif.

The newly discovered large Chating porphyry Cu–Au deposit is associated with early Cretaceous intrusive rocks in the Middle-Lower Yangtze River Belt (MLYRB), eastern China. Two types of intrusive rocks in the Chating area have been identified, i.e., the quartz-diorite porphyry, related to the Cu–Au mineralization, and the diorite porphyry that is ore-barren. Zircon LA–ICP–MS U–Pb dating yields 145–136 Ma for the Chating intrusions. They both belong to High-K calc-alkaline series, with enrichments of large-ion lithophile elements (LILEs) and light rare earth elements (LREEs), depletions of high field-strength elements (HFSEs) and heavy rare earth elements (HREEs), and no or slightly negative Eu anomalies. The quartz-diorite porphyry shows high Sr contents and Sr/Y ratios; low MgO, Cr and Ni contents; medium (La/Yb)N and Mg# (34.6–54.6) and low K2O/Na2O (

A layered gabbro suite was emplaced around Kuliana (lat 22°3ʹN and long 86°38ʹE), Orissa, eastern India, within deformed metasedimentary rocks of the north Singhbhum mobile belt. This magmatic suite does not have any exposures of feeder dikes, chilled margins, or other evidence for an intrusive character. Because the cumulate layers do not provide information about the parent magma of this suite, the equilibrium distribution method has been utilized in this study to estimate trace element concentrations of melts in equilibrium with the cumulate solid products. The mineralogical and chemical evolution of the layered suite has been carried out on the basis of both calculated parent magmas and chemical data of cumulate layers. The magmatic differentiation of the layered suite was guided by fractional crystallization and punctuated by an event of magma chamber replenishment. The calculated parent melts exhibit enriched light rare earth elements and large ion lithophile elements, marked depletion of Ti...

The Sulu Orogenic Belt in eastern China has experienced a multistage tectonic evolutionary history. However, its geological evolution has not yet been corroborated by sufficient direct evidence from basement rocks. Chaolian Island on the Qianliyan Uplift provides an opportunity to study the formation and evolution of the Sulu Orogenic Belt using direct geochronological and geochemical evidence. We determined that the characteristic mineral assemblage in the study region is quartz + K-feldspar + perthite + biotite + muscovite. The samples are silica- (SiO2 = 72.8%–75.8%) and alkali-rich (ALK(Na2O+K2O) = 8.7%–9.3%), with high iron-magnesium ratios (FeO*/(FeO*+MgO) = 0.92–0.96) and low CaO and MgO concentrations. Furthermore, they are rich in large-ion lithophile elements K, Rb, Ba, and U, but depleted in high field strength elements Nb, Ta, and Zr. They exhibit high Ga/Al values (Ga × 104/Al = 3.33–3.74) and significant fractionation between light and heavy rare earth elements. The samples are A-type granites. In the discrimination diagrams for granite genesis types, the samples plotted in the post-orogenic A2-type granite region. Secondary ion mass spectrometer (SIMS) zircon U–Pb dating results indicated that the granitic gneiss formed ~782.6–802.3 Ma (Middle Neoproterozoic), consistent with the timing of the breakup of the Rodinia supercontinent on the northeastern margin of the Yangtze Plate. Comparing geochemical characteristics and zircon U–Pb ages of the A-type granitic gneisses of the Sulu Orogenic Belt, the Qianliyan Uplift appears to be an extension of the belt across the ocean and is affiliated with the Yangtze Plate. The granitic gneiss on Chaolian Island is related to the formation of a mantle superplume during the breakup of Rodinia, and the northeastern margin of the Yangtze Plate during the Middle Neoproterozoic was located in a back-arc extension setting induced by the subduction of oceanic plates.

Massive mafic sheets were recently recognized intruding the Neoproterozoic strata in Fuyang area, eastern Jiangnan orogen. Geochronological, geochemical, and isotopic studies were carried out to understand their mantle source, crust–mantle interaction, and tectonic setting. LA-ICP-MS U-Pb zircon data indicate that the sheets were generated at 808 ± 7 Ma. The mafic sheets consist of two groups: high Ti and low Ti. They are enriched in light rare earth elements (LREE; 3.3–5.3 ppm) and show negligible Eu anomalies (δEu = 0.77–1.12). They also have strong large-ion lithophile element (LILE; Sr, K, Rb, Ba) enrichment, moderately strong high-field-strength element (HFSE) enrichment (except for Nb-Ta depletion), and positive eNd(t) (5.1–9.1). Geochemical and isotopic data indicate that the mafic sheets were generated from a depleted asthenospheric mantle source. The high-Ti mafic sheets have higher HFSE contents and less Nb-Ta depletion than the low Ti series, indicating a lower degree of partial melting...

The medium-tonnage Sarsuk polymetallic Au deposit is located in the Devonian volcanic–sedimentary Ashele Basin of the south Altay Orogenic Belt (AOB), Northwest China. Within the deposit, the rhyolite porphyries and diabases are widespread, emplaced into strata. The orebodies are hosted by the rhyolite porphyries. We studied the petrography, geochemistry, and Sr–Nd–Hf isotopes of the rhyolite porphyries and diabases, in order to understand the petrogenesis of these rocks and their tectonic significance. They display typical bimodality in geochemistry compositions. The diabases are characterized by SiO2 contents of 44.84–59.77 wt.%, high Mg# values (43–69), enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), depletion in Nb and Ta, low (87Sr/86Sr)i (0.706687–0.707613) values, positive eNd(t) (4.8–6.8) values, and positive and high eHf(t) (7.15–15.19) values, suggesting a depleted lithosphere mantle source that might have been metasomatized by subduction-related ...

Mafic dikes of mainly Early Cretaceous age (130–110 Ma) are widely developed on the Jiaodong Peninsula, China. Previous studies of the dikes, which have focused mainly on occurrences in the Jiaobei uplift and in the Sulu orogenic belt, have thoroughly examined their petrogenesis and geodynamic setting. This study identified four previously unknown mafic dikes (dolerite and lamprophyre) in southeastern Jiaolai basin (near Haiyang city), Jiaodong Peninsula. Detailed geochemical and geochronological analyses were conducted to determine the petrogenesis of the dikes and to infer their geodynamic setting. Zircon U–Pb dating by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) indicates that the dikes were emplaced at ~126 Ma. The dikes are characterized by low SiO2 contents (44.3–52.3 wt.%), high contents of MgO (7.28–10.13 wt.%), Cr (267–652 ppm), and Ni (93–335 ppm), and high Mg# values (63–73); they are enriched in large ion lithophile elements (LILEs; Ba, K, and Sr), depleted ...

The Xinyuan intrusion of the Eastern Junggar terrane is one of the mafic–ultramafic intrusions located in the Northern Xinjiang region and is associated with the southern part of the Central Asian Orogenic Belt (CAOB). Based on the secondary ion mass spectrometry (SIMS) zircon U–Pb dating, the intrusion is 326.2 ± 1.1 Ma old. Positive zircon ɛHf(t) values (+12.4 to +15.7) and mantle-like δ18O values (5.0–5.5‰) suggest that the parental magma was derived from a depleted mantle source with a low degree of crustal contamination. Significant negative Nb–Ta anomaly and large iron lithophile element (LILE) enrichment of the Xinyuan intrusion are identical to those of the coeval basalt–andesite rocks in the study area. Temporal, spatial, and geochemical evidence suggest that the Xinyuan intrusion and coeval basalt–andesite rocks are associated with the northward subduction of the Kelameili Ocean. This, together with the ages of alkaline granites and sedimentary record in the Eastern Junggar, suggests tha...

The aim of this article is to examine the geochemistry and geochronology of the Cadomian Mishu granites from northwest Iran, in order to elucidate petrogenesis and their role in the evolution of the Cadomian crust of Iran. The Mishu granites mainly consist of two-mica granites associated with scarce outcrops of tonalite, amphibole granodiorite, and diorite. Leucogranitic dikes locally crosscut the Mishu granites. Two-mica granites show S-type characteristics whereas amphibole granodiorite, tonalities, and diorites have I-type signatures. The I-type granites show enrichment in large-ion lithophile elements (e.g. Rb, Ba and K) and depletion in high field strength elements (e.g. Nb, Ti and Ta). These characteristics show that these granites have been formed along an ancient, fossilized subduction zone. The S-type granites have high K, Rb, Cs (and other large ion lithophile elements) contents, resembling collision-related granites. U–Pb zircon dating of the Mishu rocks yielded 238U/206Pb crystallizati...

New Sr, Nd, and Pb isotopic data of seven basalt samples from the middle Mariana Trough were analysed together with existing geochemical data of basalts from the middle Mariana Trough (MMT), the northern Mariana Trough (NMT), the middle Okinawa Trough (MOT), and the southern Okinawa Trough (SOT). Basalts from the Mariana and Okinawa troughs have similarities to island arc lavas and are enriched in large ion lithophile elements but depleted in high field strength elements compared with normal mid-ocean ridge basalt (N-MORB). The Sr, Nd, and Pb isotopic compositions of the back-arc basin basalts maybe modelled by a mixing between end-member components of N-MORB-like mantle and enriched mantle end-member. Modelling results suggest that as the degree of back-arc extension increases, the proportion of subduction components in the source magma decreases. The compositions of SOT basalts can be explained by the mixing of subduction components in the proportion 16%, followed by MOT at 14%, NMT at 7%, and MMT at 4%. This result indicates that the contribution of subduction components to the composition of source magmas for back-arc basalts is closely related to the tectonic evolution of the entire back-arc system. The proportions of subduction components in basaltic magma sources can be used as an indicator of the extent of evolution of a back-arc basin or the development of a back-arc spreading system. Copyright (c) 2016 John Wiley & Sons, Ltd.