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Diamondiferous kimberlites occur in the Wafangdian area in the eastern part of the North China Craton (NCC). In order to better constrain their magmatic source and emplacement time, we have investigated apatite from two kimberlites, i.e., the #110 dike kimberlite and the #50 root-zone kimberlite by measuring in situ their U–Pb and Sr–Nd isotopic compositions. The crystallization ages of the #110 and #50 apatites are 460.9 ± 16.8 Ma and 455.4 ± 19.3 Ma, respectively. For the #50 apatite, 87Sr/86Sr = 0.70453–0.70613 and εNd(t) = −2.74 to −4.52. For the #110 apatite, 87Sr/86Sr = 0.70394–0.70478 and εNd(t) = −3.46 to −5.65. Based on the similar distribution patterns of the rare earth elements (REEs) and the similar Sr-Nd isotope compositions of the apatite, it is believed that the #110 and #50 kimberlites have the same source region and the kimberlite magmas in Wafangdian were derived from an enriched mantle source (EMI). The primary magmatic composition has little effect on the emplacement pattern. It is more likely that the geological environment played an important role in controlling the retention and removal of volatile components (H2O and CO2). This led to the different evolutionary paths of the kimberlite magma in the later period, resulting in differences in the major element compositions of the apatite. High Sr concentrations may be associated with hydrothermal (H2O-rich fluid) overprinting events in the later magmatic period; the higher light rare earth element (LREE) concentration of the #50 apatite reflects the involvement of the REE3+ + SiO44− ⇔ Ca2+ + PO43− replacement mechanism. Two emplacement patterns of the #110 dike kimberlite (#110 apatite, low Sr, and high Si) and the #50 root-zone (#50 apatite, high Sr, and low Si) kimberlites were identified via major element analysis of the #110 apatite and #50 apatite. [ABSTRACT FROM AUTHOR]

Phlogopite is a crucial indicator for effectively constraining the magmatic evolution and emplacement mechanism of kimberlite. In this study, samples were collected from the No. 110 kimberlite pipe within diamond belt I and the No. 50 kimberlite pipe within diamond belt II in the southern Liaoning diamond mining area in the eastern North China Craton (NCC). Zonation is highly developed in the phlogopite; the major and trace element compositions of the phlogopite zonation in the samples were analyzed. In this study, phlogopite from the No. 50 pipe kimberlite (#50 phlogopite) zonation is divided into the following components: (1) The cores, low Ti-Cr xenocryst, average Mg# = 90.6, has a resorption structure, the presence of serpentine and talc minerals in low Ti-Cr cores (xenocrysts) can be used as evidence for hydrothermal metasomatism; (2) cores/inner rims (between core and outer rim), high Ti-Cr, it is thought to be related to the assimilation of mantle materials by deep kimberlite magma, average Mg# = 88.2; (3) outer rims, low-Cr/Cr-poor, average Mg# = 82.4, Fe, Al and Ba contents increased, and there was a trend of evolution to biotite composition believed to be related to the metasomatic metamorphism of melt and wall rock during the late magmatic evolution or ascent; (4) rinds, it is characterized by re-enrichment of Mg, rind I (low-Ti-Cr, average Mg# = 88.4), rind II (high-Ti-Cr, Mg# = 88.6), rind II may be formed earlier than rind I. Rind is very rare and has been reported for the first time in southern Liaoning kimberlite. This study was only accidentally found in the outermost part of #50 phlogopite, the Mg-rich feature represents an environment in which oxygen fugacity has increased. The phlogopite in samples from pipe No. 110 (#110 phlogopite) exhibits relatively homogeneous characteristics across different zones and is more enriched in Al and Ba, which is likely the result of mantle metasomatism. Due to its euhedral characteristics and limited composition variation, it is considered that #110 phlogopite is more likely to be derived from direct crystallization from magma than from xenocrysts. In addition, based on the simultaneous enrichment of Al and Fe in phlogopite from the core to the outer rim, pipe No. 50 was determined to be a micaceous kimberlite, while pipe No. 110 more closely resembles group I kimberlites. This paper proposes that successive pulses of kimberlite magma emplacement gradually metasomatized the conduit, and subsequent kimberlite magma ascended along the metasomatized conduit, thereby minimizing the interaction between the later magma and the surrounding mantle lithosphere. [ABSTRACT FROM AUTHOR]

Although the evolution of residual melts in magmatic systems controls their eruptability and ore-forming potential, their compositions are obscured in plutonic rocks by a protracted near-solidus evolution and the absence of interstitial glass. Here, we trace the evolution of residual melt compositions in rocks from the Strontian Intrusive Complex, Scotland, using the trace element chemistry of amphiboles, and titanites which are intergrown with amphibole rims. Laser ablation mapping reveals an abrupt change in certain trace elements in the amphibole rims, with sharp increases in Eu/Eu* and Sr/Y, and decreases in rare earth elements, Ta, Nb, and Ta/Nb ratios. Core-rim variations in these elements in titanite show the same variations as in amphibole, but are more gradual. By reconstructing the crystallisation sequence of the Strontian magmas using textural observations and thermobarometric estimates, we determine that amphibole cores crystallised prior to titanite saturation, but amphibole rims crystallised simultaneously with titanite. Using the trace element composition of the mineral phases and their modal abundance in the rock, with comparison to the whole-rock chemistry, we determine that titanite hosts the majority of the rare earth and high field strength element budget of the rocks. We therefore propose that the onset of titanite crystallisation had a profound effect on the trace element composition of late-stage residual melts at Strontian, which were inherited by the amphibole rims and subsequent titanites. This is supported by Rayleigh fractional crystallisation modelling, which demonstrates that the composition of amphibole rims cannot be explained without the influence of titanite. We therefore show that the saturation of trace element-rich phases in magmas represents a significant geochemical event in the petrogenesis of intermediate to silicic magmas. This has implications for provenance studies that attempt to reconstruct bulk rock compositions from mineral compositions, as the residual melts from which those minerals crystallise can be driven to significantly different compositions from the host magma by late-stage accessory phase crystallisation. [ABSTRACT FROM AUTHOR]

Phlogopite is a crucial indicator for effectively constraining the magmatic evolution and emplacement mechanism of kimberlite. In this study, samples were collected from the No. 110 kimberlite pipe within diamond belt I and the No. 50 kimberlite pipe within diamond belt II in the southern Liaoning diamond mining area in the eastern North China Craton (NCC). Zonation is highly developed in the phlogopite; the major and trace element compositions of the phlogopite zonation in the samples were analyzed. In this study, phlogopite from the No. 50 pipe kimberlite (#50 phlogopite) zonation is divided into the following components: (1) The cores, low Ti-Cr xenocryst, average Mg# = 90.6, has a resorption structure, the presence of serpentine and talc minerals in low Ti-Cr cores (xenocrysts) can be used as evidence for hydrothermal metasomatism; (2) cores/inner rims (between core and outer rim), high Ti-Cr, it is thought to be related to the assimilation of mantle materials by deep kimberlite magma, average Mg# = 88.2; (3) outer rims, low-Cr/Cr-poor, average Mg# = 82.4, Fe, Al and Ba contents increased, and there was a trend of evolution to biotite composition believed to be related to the metasomatic metamorphism of melt and wall rock during the late magmatic evolution or ascent; (4) rinds, it is characterized by re-enrichment of Mg, rind I (low-Ti-Cr, average Mg# = 88.4), rind II (high-Ti-Cr, Mg# = 88.6), rind II may be formed earlier than rind I. Rind is very rare and has been reported for the first time in southern Liaoning kimberlite. This study was only accidentally found in the outermost part of #50 phlogopite, the Mg-rich feature represents an environment in which oxygen fugacity has increased. The phlogopite in samples from pipe No. 110 (#110 phlogopite) exhibits relatively homogeneous characteristics across different zones and is more enriched in Al and Ba, which is likely the result of mantle metasomatism. Due to its euhedral characteristics and limited composition variation, it is considered that #110 phlogopite is more likely to be derived from direct crystallization from magma than from xenocrysts. In addition, based on the simultaneous enrichment of Al and Fe in phlogopite from the core to the outer rim, pipe No. 50 was determined to be a micaceous kimberlite, while pipe No. 110 more closely resembles group I kimberlites. This paper proposes that successive pulses of kimberlite magma emplacement gradually metasomatized the conduit, and subsequent kimberlite magma ascended along the metasomatized conduit, thereby minimizing the interaction between the later magma and the surrounding mantle lithosphere.

We employed MC‐ICP‐MS to measure the mass‐dependent Ca isotope compositions of Vesta‐related meteorites. Eucrites and diogenites show distinct Ca isotope compositions, which is caused by crystallization of isotopically heavy orthopyroxene. The Ca isotope data support a model where the two lithologies are linked, where the diogenites, mainly composed of orthopyroxene crystallized from an eucritic melt. As normal eucrites are the main Ca reservoir on Vesta, their δ44/40Ca values (per mil 44Ca/40Ca ratios relative to NIST 915a) best represents that of bulk silicate Vesta (0.83 ± 0.04‰). This value is different from those of bulk Earth (0.94 ± 0.05‰) and Mars (1.04 ± 0.07‰), suggesting that there exists notable Ca isotope heterogeneity between inner solar system bodies. The δ44/40Ca difference between chondrules and these planets does not support the pebble accretion model as the main mechanism for planetary growth. Plain Language Summary: Calcium is a major, refractory element in solar system, and its mass‐dependent isotope fractionation effect is a robust proxy for probing planetary magmatic evolution and tracing the genetic relationships between solar system materials. We report high‐precision Ca isotope data for the howardite‐eucrite‐diogenite and mesosiderite meteorites, which potentially derive from the asteroid 4 Vesta, to better understand the origin and differentiation of Vesta. Eucrites and diogenites have different mass‐dependent Ca isotope compositions, which is caused by orthopyroxene crystallization from a magma ocean. We have modeled the Ca isotope evolution of this magma ocean and find that eucrites and diogenites can have formed from this melt. Eucrites show similar Ca stable isotope compositions to howardites and mesosiderites, consistent with a mixing model of eucrites and diogenites for howardites and the silicate portion of mesosiderites originating from Vesta. The Ca‐rich eucrites can best represent the Ca isotope composition of bulk Vesta. It shows Earth, Mars, and Vesta do not share a common Ca isotope composition, suggesting their potentially different precursor material. All these planets and asteroids possess different Ca isotope composition from the chondrules formed in the inner solar system, which does not support a chondrule‐rich model for accretion of terrestrial planets. Key Points: Eucrites possess isotopically light Ca than diogenites; the Ca isotope modeling shows they are co‐geneticEarth, Mars, and Vesta do not share a common Ca isotope reservoir, reflecting isotopic heterogeneities in the inner solar systemThe Ca stable isotopes of the planets/asteroids do not overlap those of chondrules, which does not support a chondrule‐rich model for planet accretion [ABSTRACT FROM AUTHOR]

Abstract We employed MC‐ICP‐MS to measure the mass‐dependent Ca isotope compositions of Vesta‐related meteorites. Eucrites and diogenites show distinct Ca isotope compositions, which is caused by crystallization of isotopically heavy orthopyroxene. The Ca isotope data support a model where the two lithologies are linked, where the diogenites, mainly composed of orthopyroxene crystallized from an eucritic melt. As normal eucrites are the main Ca reservoir on Vesta, their δ44/40Ca values (per mil 44Ca/40Ca ratios relative to NIST 915a) best represents that of bulk silicate Vesta (0.83 ± 0.04‰). This value is different from those of bulk Earth (0.94 ± 0.05‰) and Mars (1.04 ± 0.07‰), suggesting that there exists notable Ca isotope heterogeneity between inner solar system bodies. The δ44/40Ca difference between chondrules and these planets does not support the pebble accretion model as the main mechanism for planetary growth.

The Laiyuan complex in the central North China Craton (NCC) incorporating different magmatic suites offers an excellent opportunity to investigate the lithospheric evolution and cratonic destruction. However, the petrogenesis and tectonic implications of this magmatic suite remain debated due to lack of integrated studies. Here we evaluate the magmatism and tectonic setting assembling data from multidisciplinary investigations of the Laiyuan complex. The complex is composed of volcanic suites, granitoids, ultramafic-mafic intrusions, and dykes showing common features of enrichments in LREEs and LILEs and depletions in HFSEs. Detailed petrogenetic considerations suggest that crust-mantle and lithosphere-asthenosphere interactions contributed to the formation of various magmatic suites. The involvement of thickened lower crust and enriched lithospheric mantle in the source, and diverse magmatic processes including partial melting, fractional crystallization, and magma mixing have played a significant role in the petrogenesis of the Laiyuan complex. Furthermore, the lithosphere-asthenosphere interaction induced by thinning lithosphere and upwelling asthenosphere controlled the source variations from dolerites to lamprophyres. The complex formed in an extensional tectonic setting triggered by the subduction of the Paleo-Pacific Plate. The subduction, rollback, and stagnation of the Paleo-Pacific slab contributed to the modification of the lithospheric architecture of the North China Craton. A slow and gradual thermal-mechanical erosion occurred at the central North China Craton whereas the rapid and intense lithospheric delamination occurred at the eastern North China Craton contributing to different lithospheric evolution. Both of the mechanisms combined with the subduction of Paleo-Pacific slab played a significant role in the destruction of the North China Craton and the formation of various magmatic suites. An integrated model is proposed to describe the magmatic evolution of the Laiyuan complex. During Jurassic, the subduction of the Paleo-Pacific Plate reached beneath the central North China Craton. At 145–140 Ma, the fast slab rollback occurred and lead to hot asthenosphere upwelling and extensional setting in the central North China Craton inducing the crust-mantle interaction accounting for the petrogenesis for the formation of granitoids with MMEs (137–126 Ma), volcanic rocks (131–127 Ma), and felsic dykes (131–127 Ma). Through time, the lithosphere became substantially thin with the asthenospheric input increasing to form dolerite dykes at 125–117 Ma and lamprophyre dykes at 115–111 Ma.

Enclaves constitute a key tracer guide to assess the magmatic source and evolutionary processes of Cu–Mo–Au porphyry-type deposits. In this study, four types of enclaves were identified in the Baogutu reduced Cu porphyry-type deposit, West Junggar, Northwest China: gabbroic enclaves (Type 1) and schist enclaves (Type 2) are proposed to be restites and immiscible enclaves, respectively, which confirm the contributions of mantle components and sediments in the reduced Cu porphyry-type deposit. Fine-grained dioritic enclaves (Type 3) have a similar mineral composition and texture to the dioritic host rocks, which are probably autoliths derived from inhomogeneous fractional crystallization. Tuffaceous siltstone enclaves (Type 4) with a zircon U-Pb age of 339.2 ± 7.5 Ma (MSWD = 0.55), the formation age of which is in agreement with the host early Carboniferous rock unit, indicate that these tuffaceous siltstone enclaves might have formed in a contamination process. Moreover, the schist enclaves, together with the newly discovered 2691.3 ± 12.3 Ma inherited zircon in tuffaceous siltstone enclaves, further indicate that the Baogutu arc could be a continental arc. [ABSTRACT FROM AUTHOR]

Iranian porphyry copper deposits (PCDs), resulted from the evolution of Neo–Tethys Ocean during the Mesozoic and Cenozoic, dominantly distributed in the five main tectono-magmatic belts that meanwhile the Kerman Porphyry Copper Belt (KPCB) is the most famous and important belt in the south of Iran while the Lut Block is the oldest and modern known porphyry belt in eastern Iran. PCDs of the KPCB (+Najmabad; group 1) hosting moderate to giant world-class deposits belong to the Oligocene–Miocene. On the other hand, PCDs of the Lut Block (except Najmabad; group 2) formed during the Eocene–Oligocene, are mostly subeconomic to barren. Despite the similarities in tectonic setting, host rock composition, hydrothermal alteration zones, and mineralization type, there are significant differences in geochemical characteristics (depression in MREE/HREE pattern (group 1) vs. horizontal trend (group 2), Sm/Yb greater than 2.4 (group 1) vs.

The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogenic belt in the world and its formation involved a complicated process of arc–continent collision. Large‐scale Mesozoic volcanic activity in the Great Xing'an Range (GXAR) in northeastern China, which constitutes part of the eastern CAOB, has received much recent research attention. However, the petrogenesis and formation mechanism of the late Mesozoic igneous rocks remain enigmatic. This paper investigates the geochronology, petrogenesis, and formation mechanism of late Mesozoic magmatic rocks in the Kelihe area of the GXAR based on zircon U–Pb dating, petrology, and geochemistry. Late Mesozoic magmatism in the Kelihe area occurred during the Late Jurassic (165–155 Ma) and Early Cretaceous (130–120 Ma). These igneous rocks generated by this magmatism are characterized by high SiO2 (69.97–75.49 wt%) and low MgO (0.11–0.68 wt%), Cr (10–30 ppm), Co (0.2–2.6 ppm), and Ni (0.5–1.6 ppm) contents. Trace elements show enrichment in Rb, Th, U, Zr, and K, and depletion in Ba, P, Nb, and Ti. These features indicate that the rocks were derived from partial melting of the crust. Furthermore, the rhyolites have high Na2O (5.02–5.44 wt%) and K2O (3.94–4.88 wt%) contents, similar to those of melts formed by the partial melting of basaltic crust. Combining the present results with the findings of previous studies, it is inferred that the Mesozoic igneous rocks formed in a post‐collisional extensional setting related to lithospheric thinning and asthenospheric upwelling after the closure of the Mongol–Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

The Wuhaolai mafic complex is located in the north margin of the North China Craton (NCC), Inner Mongolia. To discuss the mineralogical features, magma evolution process, and tectonic setting of the complex, we analyzed the geochemical compositions of clinopyroxene and hornblende using an electron probe. The results revealed that the parental magma of this complex belonged to the intraplate alkaline basalt series. The normal zoning texture and the relation between Mg# and FeO, Al2O3, CaO, Na2O, SiO2 and Cr2O3 suggested that the clinopyroxenes of pyroxenite and gabbro crystallized from the same parental magma. The similar CaO content of clinopyroxenes indicated that the parental magma of the Wuhaolai complex may have suffered crustal contamination. Furthermore, the characteristics of hornblende demonstrated that the magma source was modified by fluids derived from subducted slab. Based on the value of Kdcpx (0.23–0.27), the equilibrium melt with clinopyroxene exhibited a relatively low Mg# (43–53), indicating that the parental magma was derived from the lithospheric mantle and underwent crystal fractionation. The gabbro crystallization temperature and pressure was found to be lower than that of pyroxenite, indicating that gabbro was formed at a lower depth than that of pyroxenite. Combining the tectonic setting discrimination diagram of clinopyroxene with the results of previous studies on the late Paleozoic intrusions near the research area, we proposed that the Wuhaolai complex was formed in an intraplate environment. The magma source was modified by fluids derived from the subducted slab during the subduction of the Paleo-Asian Ocean (PAO). After the PAO closure, the parental magma of the Wuhaolai complex was produced by the partial melting of the enriched lithospheric mantle

Chemical classifications of granites sensu lato have been developed and revisited over decades, but no classification scheme has been universally accepted yet. The more or less known coupled reasons for this apparently impossible task are reviewed here. The main problem is that different granitoids do not fall in distinct categories with sharp boundaries, but comprise a continuous spectrum of rock types both in their chemical and modal compositions. The unifying factor is the minimum-melt nature of the granites sensu stricto, as primary and evolved melts can have a granitic composition. This minimum-melt nature has two consequences, which are the main reasons for the absence of sharp boundaries in every compositional classification system, either modal or chemical. Firstly, the chemistry of granites spreads from the minimum melt to non-minimum compositions, and thus some granites represent a rock series formed by a continuous magmatic evolution, not by discrete steps; secondly, granite series, which are generated from different sources and by several petrogenetic processes, eventually converge at the most silica-rich compositions. There is a relationship between the tectonic scenarios of formation of granites and the chemical overlap that contributes to the absence of a satisfactory chemical classification: the protracted evolution of the tectonic settings following the Wilson cycle and more complicated scenarios change the chemical and modal composition of the granite sources. The overlap in the most silica-rich compositions of the granites s.l. due to the minimum melt nature may extend to more mafic members in a granite series: the closer the sources are in their composition, the greater is the overlap, becoming a second contribution to the lack of sharp boundaries between granite types. The huge efforts to create a satisfactory chemical compositional classification system have actually led to a significant contribution to granite petrology: the discovery of the main chemical differences between granite types, the main chemical parameters (silica content, alkalinity, aluminosity, maficity or FeOt + MgO content, and the Fe/Mg and Na/K ratios) and the petrogenetic processes that cause the change in these parameters. Therefore, despite the lack of agreement over the 'perfect' classification system, the investigations have not been fruitless: they have led to the realization that non-genetic classifications are preferable to name the individual rock samples; chemical classification schemes should be left to distinguish magmatic suites and to unravel their prospective petrogenesis and geotectonic setting. [ABSTRACT FROM AUTHOR]

We conducted in situ geochemical (major-, trace-element and Nd isotope compositions) analyses on apatite, together with whole-rock geochemistry from gabbro, granodiorite and granite in the Cretaceous Pingtan intrusive complex (SE China), aiming to investigate the roles of magmatic evolution and post-crystallization hydrothermal activity during its formation. Regardless of limited range in initial Nd isotopes ranges in both bulk rock [ɛNd(t) = − 2.0 to − 0.4] and associated apatite [ɛNd(t) = − 3.8 to − 0.4] from the Pingtan igneous complex, the apatite shows wide compositional and textural variations from gabbro to granite. Apatite from the gabbro (Group 1) displays a zoning structure characterized by increasing F and Sr but decreasing Cl and LREE from the core to rim. The increase of Sr from the core to rim is attributed to plagioclase accumulation, and the decreases of LREE and Cl from the core to rim is caused by post-crystallization hydrothermal activity. The high Cl content in the primitive Group 1 apatite further suggests derivation of the mafic magma from a mantle wedge metasomatized by Cl-rich sediment. In contrast, apatite from the granite (Group 2) has the lowest Cl and Sr but the highest F and Yb contents, which can be further divided into two subgroups of Group 2A and 2B based on texture and composition. Group 2A apatite shows homogenous composition with trace elements similar to apatite from I-type granite. The positive correlation between Sr and Eu/Eu* indicates that crystallization of Group 2A apatite is co-precipitated with a feldspar-dominated fractionation. However, Group 2B apatite contains mineral inclusion of monazite and has the highest U content and F/Cl ratio, resembling apatite from S-type or highly fractionated I-type granite. These features are consistent with the influence of post-crystallization hydrothermal activity. Apatite from the granodiorite (Group 3) has an intermediate composition between Group 1 and 2A apatite and shows a homogenous texture with trace element features similar to that from I-type granite. Group 3 apatite defined a negative correlation of Sr with La/Yb, which is attributed to fractional crystallization of hornblende and plagioclase. The geochemistry of apatite indicates that the gabbro and granitic rocks of the Pingtan intrusive complex were, respectively, derived from the mantle and crustal sources with similar ɛNd(t) values. Our study, therefore, demonstrates that apatite geochemistry has a potential to monitor the magma source, magmatic evolution and post-crystallization fluid activity of an igneous complex. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textural and chemical features of beryl can trace magmatic-hydrothermal evolution. • Cs in beryl is an ideal trace element to monitor the magmatic evolution. • Fluid exsolution can promote the remobilization of Ta and Rb. In the large Shihuiyao Rb-Nb-Ta-Be deposit, a beryl-bearing granite was identified with three texturally different zones that show an increasing degree of fractionation, including the albite granite (bottom zone), albite granite with pegmatite pockets (intermediate zone), and intercalation of granite and pegmatite layers (top zone). Beryl occurs both in the intermediate and top zones. Microtextural (SEM), Raman spectra, and trace-element (LA-ICP-MS) data on beryl from these zones shed new light on the behavior of trace elements during magmatic-hydrothermal evolution. In the intermediate zone, magmatic beryl (Brl-1) has a homogeneous texture, while beryl in the top zone (Brl-2) can be divided into magmatic (Brl-2a) and metasomatic subtypes (Brl-2b). The magmatic Brl-2a shows oscillatory zonation, whereas the metasomatic Brl-2b is darker in BSE images and highly porous. Fractional crystallization led to an increase in Na, Sc, Fe, Rb, and Cs contents from Brl-1 to Brl-2a. Comparing these data with those of beryl in other pegmatites worldwide reveals that Cs in beryl is an ideal trace element to monitor the magmatic evolution of the pegmatite host. Distinct textural and chemical features of Brl-2a and Brl-2b reflect metasomatic alteration by a dissolution-reprecipitation process for Brl-2b. In combination with published experimental and fluid inclusion data, we propose that metasomatic fluids exsolved from the magma during late-magmatic stages could transport large amounts of rare metals, such as Ta and Rb. The higher content of Ta in Brl-2b compared to Brl-2a suggests that metasomatic fluids exsolved from the magma play a favorable role in Ta mineralization. In contrast, decreasing Rb contents in Brl-2b is attributed to the high mobility of Rb in the fluid. Such Rb-rich fluids are expected to generate Rb orebodies of economic value surrounding the ore-bearing granite, implying that more investigation into hydrothermal Rb mineralization in the Shihuiyao district is warranted. [ABSTRACT FROM AUTHOR]

The Dahutang tungsten deposit, located in the Yangtze Block, South China, is one of the largest tungsten deposits in the world. Tungsten mineralization is closely related to Mesozoic granitic plutons. A drill core through a pluton in the Dalingshang ore block in the Central segment of the Dahutang tungsten deposit shows that the pluton is characterized by multi-stage intrusive phases including biotite granite, muscovite granite, and Li-mica granite. The granites are strongly peraluminous and rich in P and F. Decreasing bulk-rock (La/Yb)N ratios and total rare earth element (ΣREE) concentrations from the biotite granite to muscovite granite and Li-mica granite suggest an evolution involving the fractional crystallization of plagioclase. Bulk-rock Li, Rb, Cs, P, Sn, Nb, and Ta contents increase with decreasing Zr/Hf and Nb/Ta ratios, denoting that the muscovite granite and Li-mica granite have experienced a higher degree of magmatic fractionation than the biotite granite. In addition, the muscovite and Li-mica granites show M-type lanthanide tetrad effect, which indicates hydrothermal alteration during the post-magmatic stage. The micas are classified as lithian biotite and muscovite in the biotite granite, muscovite in the muscovite granite, and Li-muscovite and lepidolite in the Li-mica granite. The Li, F, Rb, and Cs contents of micas increase, while FeOT, MgO, and TiO2 contents decrease with increasing degree of magmatic fractionation. Micas in the muscovite granite and Li-mica granite exhibit compositional zonation in which Si, Rb, F, Fe, and Li increase, and Al decreases gradually from core to mantle, consistent with magmatic differentiation. However, the outermost rim contains much lower contents of Si, Rb, F, Fe, and Li, and higher Al than the mantle domains due to metasomatism in the presence of fluids. The variability in W contents of the micas matches the variability in Li, F, Rb, and Cs contents, indicating that both the magmatic and hydrothermal evolutions were closely associated with W mineralization in the Dahutang deposit. The chemical zoning of muscovite and Li-micas not only traces the processes of W enrichment by magmatic differentiation and volatiles but also traces the leaching of W by the fluids. Therefore, micas are indicators not only for the magmatic–hydrothermal evolution of granite, but also for tungsten mineralization. [ABSTRACT FROM AUTHOR]

The Wuhaolai mafic complex is located in the north margin of the North China Craton (NCC), Inner Mongolia. To discuss the mineralogical features, magma evolution process, and tectonic setting of the complex, we analyzed the geochemical compositions of clinopyroxene and hornblende using an electron probe. The results revealed that the parental magma of this complex belonged to the intraplate alkaline basalt series. The normal zoning texture and the relation between Mg# and FeO, Al2O3, CaO, Na2O, SiO2 and Cr2O3 suggested that the clinopyroxenes of pyroxenite and gabbro crystallized from the same parental magma. The similar CaO content of clinopyroxenes indicated that the parental magma of the Wuhaolai complex may have suffered crustal contamination. Furthermore, the characteristics of hornblende demonstrated that the magma source was modified by fluids derived from subducted slab. Based on the value of Kdcpx (0.23-0.27), the equilibrium melt with clinopyroxene exhibited a relatively low Mg# (43-53), indicating that the parental magma was derived from the lithospheric mantle and underwent crystal fractionation. The gabbro crystallization temperature and pressure was found to be lower than that of pyroxenite, indicating that gabbro was formed at a lower depth than that of pyroxenite. Combining the tectonic setting discrimination diagram of clinopyroxene with the results of previous studies on the late Paleozoic intrusions near the research area, we proposed that the Wuhaolai complex was formed in an intraplate environment. The magma source was modified by fluids derived from the subducted slab during the subduction of the Paleo-Asian Ocean (PAO). After the PAO closure, the parental magma of the Wuhaolai complex was produced by the partial melting of the enriched lithospheric mantle. [ABSTRACT FROM AUTHOR]

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The Bijiashan intrusion belt, one of the basic–ultrabasic intrusion belts in the Beishan Terrane, northeastern Tarim Craton, is composed of the Hongshishan, Hongshishanxi, Xuanwoling, Bijiashandong, and Bijiashan intrusions. These intrusions are mainly composed of dunite, troctolite, olivine gabbro, and gabbro. Magma evolution of the intrusions was strongly controlled by fractional crystallization, and the crystallization sequence was mainly olivine → plagioclase → pyroxene. This is evidenced by whole‐rock MgO contents that are positively correlated with TFe2O3 and negatively correlated with Al2O3, CaO, and Na2O and an increase in total rare‐earth element and trace elements contents from ultrabasic to basic rocks. Most of the basic–ultrabasic rocks are enriched in large ion lithophile elements (Cs, Rb, Sr, and U) and depleted of high field strength elements (Zr, Hf, Nb, Ta, and Ti). The variable and relatively low Ce/Pb (0.17–7.3) and Nb/U (0.13–10.1) ratios, variable Th/Yb (0.02–4.1) ratio, initial 87Sr/86Sr ratios (0.7033 to 0.7094) and εNd (t) (7.54 to −4.25), suggest less than 6% crustal contamination. Based on the maximum Fo value of olivine (Fo90), whole‐rock average composition and olivine–liquid compositional relationships, the parental magma is of high‐Mg basaltic magma containing 13.4 wt.% MgO. According to rare‐earth element contents and Sr–Nd isotopic compositions, the parental magma was originated from partial melting of depleted sub‐continental lithospheric mantle. [ABSTRACT FROM AUTHOR]

The 5.65 to 1.80Ma Cerro Guacha Caldera Complex (CGCC) in the Altiplano-Puna Volcanic Complex of SW Bolivia, with >90% of its >2500km3 erupted volume consisting of crystal-rich dacite, has all the characteristics of a 'monotonous' magma system. However, it also records minor lithological heterogeneity. Such hand-sample scale heterogeneity is ubiquitous in dominantly 'monotonous' magmas, yet remains poorly investigated. Here we explore the heterogeneity in the CGCC, and its implications for the construction and evolution of 'monotonous' magma systems. We focus on the Guacha II Caldera (G2C), the younger of two calderas in the complex, because its pre- to post-climactic eruptive history is fully represented and, although the eruptive products are dominantly dacitic (66-72 wt % SiO2), the juvenile pyroclastic deposits and lavas erupted throughout the history of the G2C define a high-K, calc-alkaline suite of diverse compositions that range from andesite to high-Si rhyolite. The G2C cycle initiated with the effusive eruption of crystal-rich andesite lava. The subsequent explosive phase began with a short-lived plinian eruption of crystalpoor rhyolite pumice. This was immediately followed by the Catastrophic Caldera Forming (CCF) eruption at 3.49 ± 0.01Ma and the deposition of dacite-rhyolite and banded pumice within the >800km3 dense rock equivalent (DRE) Tara ignimbrite. A significant volume of magma remained and caused ~1.5 km of resurgent uplift. Three crystal-rich dacite-rhyolite post-climactic lava domes (Chajnantor Dome, Rio Guacha Dome, and Chajnantor Lavas) subsequently erupted from separate coexisting melt-rich 'pods' within the G2C's remnant mush. Whole-rock isotope ratios across all lithologies span a significant range in 87Sr/86Sr (0.709380-0.713159) and a relatively narrow range in 143Nd/144Nd (0.512179-0.512297) and δ18O(qtz) (+8.38 to+8.68%), best reconciled with a twostage assimilation-fractional crystallization (AFC) model. Stage 1 initiated with parental melts from the Altiplano-Puna Magma Body (APMB) fractionating and assimilating crustal lithologies in the upper crust (10-25km depth) to generate the magma compositions recorded in the andesite lava and the ignimbrite banded pumice. These magmas subsequently accumulated and underwent a second stage of AFC in the uppermost crust (~800-850 °C and 5-9km depth) to produce the most differentiated magmas recorded in the ignimbrite rhyolite pumices. Although the two-stage AFC model presented here is non-unique, it implies that the basement composition is temporally or spatially variable throughout the ~30km of upper crust beneath the G2C. The origin of some of the minor lithologies erupted from the G2C requires further explanation beyond AFC. Recharge, binary mixing, and additional crystal fractionation of the plagioclase, quartz, sanidine, biotite, and Fe-Ti oxides identified within the ignimbrite dacite-rhyolite pumice are required to explain the geochemical diversity of these minor lithologies. Integrating geochemical modeling with the volcanological framework we find that the andesite magma played a large role in the development and evolution of the G2C magma system. At least one episode of andesite magma recharge occurred in the upper crustal magma reservoir prior to the eruption of the G2C and fractionation of this andesite magma formed residual rhyolitic melt sampled by the plinian eruption. Andesitic recharge therefore not only sustained the pre-eruption magma reservoir's dominant dacitic composition throughout its history, but also may have acted as an eruption trigger. The minor lithologies erupted from a 'monotonous' magmatic system record processes that are otherwise lost in the inexorable march to homogeneity that characterizes the long-term evolution of many CCF magma systems. Our findings complement investigations that have identified heterogeneity at the crystal- and micro-scale, but emphasize that upper crustal processes are recorded as hand-sample scale heterogeneity that is serendipitously sampled by eruption before being integrated into a 'monotonous' whole. [ABSTRACT FROM AUTHOR]

[Display omitted] • One major and two subordinate episodic highly evolved granitic magmas emplacement with associated Ta-Nb mineralization occurred in the Jiabusi rare metal deposit. • The Jiabusi multiphase granites were originated by partial melting of the same sources involving Mesoproterozoic crust and significantly juvenile crustal materials. • The magmatic fractionation and melt-hydrothermal interaction contributes to Ta-Nb mineralization. • The west part of Jiabusi LAG pluton has good further prospecting potential of new hidden economic Ta-Nb deposit that in some cases have not been exposed. The newly discovered Jiabusi Ta-Nb deposit occurs within the latest Jurassic-Early Cretaceous multiphase granites, which are composed of felsic, peraluminous intrusions including biotite, two-mica, Li-mica, and topaz-lepidolite granites (abbreviated as BG, TMG, LAG, and TLG, respectively). Ore mineralizations are mainly hosted in the LAG and TLG, with subordinate mineralization occurring in the pegmatitic dykes. In this contribution, we present a systematic work of geochronology, whole-rock geochemistry, and Sr-Nd-Hf isotope composition for determining the timing of mineralization, petrogenesis, geodynamic setting, and ore-forming processes. Zircon U-Pb dating constrains the emplacement ages of 148–151 Ma for the BG, TMG, and LAG and reveals at least three episodes of Ta-bearing granitic pegmatites formed at ∼150 Ma, 127 Ma, and ∼100 Ma, respectively. Disseminated cassiterite grains from the LAG, TLG, and KPD yielded U-Pb ages of 149, 149, and 104 Ma, respectively. These granites have similar and limited features of (87Sr/86Sr) i = 0.7099, ε Nd (t) = −2.8 to −5.1, and ε Hf (t) = −4.7 to +5.5 and relative old Nd and Hf model ages of 1166–1442 Ma and 840–1500 Ma, respectively, indicating that Jiabusi multiphase granites are likely derived from the same magma reservoir by the partial melting of Mesoproterozoic crust in the destroyed northern margin of the NCC and are characterized by having involved significantly juvenile crustal materials. From the BG, TMG to LAG and TLG, bulk-rock Li, Rb, Cs, Be, Sn, Nb, and Ta contents increase with decreased Zr/Hf, Nb/Ta, and K/Rb ratios. Such systematic variations denote that these multiphase granites are cogenetic and that the LAG and TLG have experienced a higher degree of magmatic fractionation than the BG and TMG. The decrease in bulk-rock (La/Yb) N ratios, ΣREE, and Sr-Ba concentrations from the BG to TMG and LAG suggest an evolution involving the fractional crystallization of monazite and feldspar. The remarkable M−type lanthanide tetrad effect (TE 1,3 = 1.22–1.75) matches low Nb/Ta (<1.2) and Zr/Hf (<5.0) ratios, indicating both the magmatic fractionation and melt-hydrothermal interaction were closely associated with Ta-Nb super enrichment in the LAG and TLG stocks. The combined evidence of compositional gaps and geologic spatial relationship between the BG batholith and Ta-bearing plutons confirm that the western part of the Jiabusi LAG stock and its surrounding concealed muscovite granites (MSG) are the further prospecting targets for Ta-Nb and W deposits. [ABSTRACT FROM AUTHOR]

Major elements, trace elements and sulfur, oxygen isotopic compositions of the main intrusions were studied in Yueshan area. The fact that intrusions enriched in Th and Sr, and depleted in Rb and Ba in this area, suggests that the original magma roots in alkali basalt magma of upper mantle, with deep characteristics. It can be seen that the diagenesis environments are the island arc and active continental margin areas from the lg τ to lg σ diagram of intrusions. With the increase of SiO, FeO, MnO and PO decrease, which shows that the magma of Yueshan area endured crystal fractionation of ferromanganese mineral and apatite in early evolution stage. With the further rise and evolution of magma, magma composition of calcium increased, meanwhile enriched in Zr, and depleted in Nb and Ta. This indicates that crustal component is gradually added, the assimilation and contamination occur between magma and crustal material, which includes the magma evolving, from calc-alkaline series to alkaline series. The results show that crystal fractionation, assimilation and contamination are the main evolution law of magma in this area. [ABSTRACT FROM AUTHOR]

Growth of continental crust involves the complex interplay of subduction zone magmatism, to generate the crust, followed by stabilization through crustal thickening, magmatism and ultimately isolation from the active plate margin. The Jinshajiang orogenic belt, SW China, provides an exceptional record of continental development as the result of closure of the Paleo-Tethys seaway and ensuing collision. A compilation of U-Pb age and geochemical data for the plutonic and volcanic rocks within the southern part of the Jinshajiang orogenic belt, including new high-precision ages for the Ludian granitoid batholith of 231 to 220 Ma, enables us to explore the interaction between magmatism and orogeny in the context of the Paleo-Tethys closure and continental amalgamation. These age and geochemical constraints, in conjunction with other geologic evidence, suggest that subduction of the Paleo-Tethys ocean dominated local tectonics prior to the Triassic, creating a volcano--plutonic arc along the eastern margin of the Qamdo-Simao terrane. Following consumption of the ocean, collision zone magmatism, dated at 247 to 237 Ma, was manifested by eruption of voluminous volcanic rocks in a suture-parallel zone. Crustal anatexis was contemporaneous with the earliest phases of collision, producing high-silica rhyolites of Early Triassic age (ca. 247-246 Ma). Between 245 and 237 Ma, the local tectonic regime switched from compression to extension, probably due to strain partitioning caused by oblique convergence, which led to the development of rift-basins and extensive syn-tectonic bimodal volcanism associated with deep-water sediments. From 234 Ma to 214 Ma, the emplacement of high-K, calc-alkaline granodiorites-monzogranites occurred prior to, or during, isostatic uplift and extension, probably caused by breakoff of the subducted slab. The resultant exhumation brought deep-seated granitoid batholiths to the surface, and was contemporaneous with intrusion of ultramafic-mafic melts. Ophiolitic melange (ca. 362-294 Ma) and collision-related magmatic suites (247-214 Ma) are unconformably overlain by a Late Triassic (229-217 Ma) conglomerate-rich sequence that represents an overlap assemblage, across the Qamdo-Simao terrane (Indochina) and Yangtze Block of South China. [ABSTRACT FROM AUTHOR]

The build-up of large magmatic complexes can proceed piecemeal over periods of several million years through sequences of complex processes of magma production, differentiation, assimilation, final crystallization and subsequent metasomatic modification. All these stages can produce or modify minerals used as geochronometers, such as zircon, monazite and titanite. The present study exemplifies such complex relationships, also demonstrating how a systematic approach with comprehensive sampling and careful high-resolution U–Pb analyses can yield a coherent picture of the entire magmatic process. The study was conducted on the Pavia pluton, an elongated Variscan intrusion in the Ossa–Morena Zone of Portugal. The geochronological data show that the Pavia pluton was emplaced by the amalgamation of multiple magma pulses into the crust, over a period of c. 11 Myr. An early event at ∼340 Ma, revealed by xenocrystic zircon, preceded the magmatic activity at the exposed level of the pluton, but is recognized as the main magmatic event elsewhere in the Ossa–Morena Zone. A second event at 328 Ma formed tonalite, trondhjemite and granodiorite, and subordinate differentiates in the central domains of the pluton (units I and II). A third event at c. 324 Ma emplaced granodiorite in the flanking domains III–V and the contemporaneous and widespread two-mica granite in domain VI, together with late rhyodacite porphyries, microgranodiorites, aplite–pegmatite and pegmatite dikes. A fourth event at 319–317 Ma was characterized by the emplacement of some microgranites and pegmatite dikes. These two last magmatic events also had an effect on the previously emplaced rocks, causing local overgrowths and isotopic resetting of minerals. The occurrence of a fifth magmatic event at depth at 313 Ma is the inferred cause of the hydrothermal activity responsible for local zircon, monazite and titanite resorption and/or recrystallization and for some of the textures exhibited by the main rock-forming minerals. The magmatic episodes were interspersed with periods of quiescence; this cyclicity presumably reflects an external control by the transtensional tectonic regime of the Ossa–Morena Zone. [ABSTRACT FROM AUTHOR]

Taranaki (Mt. Egmont) in the western North Island of New Zealand is a high-K andesite volcano with an eruptive history extending over more than 200 kyr. In general, petrological research has concentrated on the post-10 ka record of the modern edifice. This study focuses on the earlier history, which is recorded in 11 major pre-7 ka debris avalanche deposits. Each of these formed as a result of a catastrophic collapse of the edifice of the time. The clast assemblages of these deposits provide insights into the chemical compositions of magmas erupted during the earlier stages of activity of the volcano and form the basis for a new chemo-stratigraphic analysis of the pre-10 ka volcanic succession. Sample suites from the studied debris avalanche deposits show a progressive enrichment in K2O and large ion lithophile elements (LILE), reflecting a gradual evolution to high-K andesite. The early magmatic system (pre-100 ka) produced a wide range of compositions including relatively primitive basalts and basaltic andesites. These rocks contain phenocryst assemblages that indicate crystallization within the lower crust or mantle, including a broad range of clinopyroxene compositions, high-Al2O3 hornblende, olivine and phlogopite. A higher proportion of high-silica compositions in the younger sample suites and the appearance of late-stage, low-pressure mineral phases, such as high-TiO2 hornblende, biotite and Fe-rich orthopyroxene, reflect a gradual shift to more evolved magmas with time. These new data are interpreted to reflect a multi-stage origin for Taranaki andesites. Parental magmas were generated within a lower crustal ‘hot zone’, which formed as a result of repeated intrusions of primitive melts into the lower crust. The geochemical and mineralogical evidence indicates that prior to 100 ka this zone was relatively thin and cold, so that primitive magmas were able to rise rapidly through the crust without significant interaction and modification. As the hot zone evolved, larger proportions of intruded and underplated mafic material were partially remelted, and interaction of these melts with fractionating mantle-derived magmas generated progressively more K- and LILE-enriched compositions. A complex and dispersed magma assembly and storage system developed in the upper crust where the hot-zone melts were further modified by fractional crystallization and magma mixing and mingling. [ABSTRACT FROM PUBLISHER]

The ultramafic–mafic Kharaelakh intrusion in the northwestern part of the Siberian Craton (Russia) hosts major economic platinum-group-element (PGE)–Cu–Ni sulphide deposits. In situ U–Pb, REE and Hf-isotope analyses of zircon from these rocks, combined with detailed study of crystal morphology and internal structure, identify four zircon populations. U–Pb ages of these populations cover a significant time span (from 347 ± 16 to 235.7 ± 6.1 Ma) suggesting multiple magmatic events that cluster around 350 and 250 Ma, being consistent with two recognised stages of active tectonism in the development of the Siberian Craton. The oldest zircon population, however, represents previously unknown stage of magmatic activity in the Noril’sk area. Epsilon-Hf values of +2.3 to +16.3 in the analysed zircons reflect a dominant role of mantle-derived magmas and suggest that juvenile mantle material was the main source for the ultramafic–mafic Kharaelakh intrusion. A significant range in initial 176Hf/177Hf values, found in zircons that cluster around 250 Ma, indicate mixing between mantle and crustal magma sources. Our findings imply that economic intrusions hosting PGE–Cu–Ni deposits of the Noril’sk area have a far more complex geological history than is commonly assumed. [ABSTRACT FROM AUTHOR]

Major and trace element, mineralogical and petrographical data are presented for submarine and subaerial lavas from Easter Island and two neighbouring seamounts. The samples can be divided into three groups based on their major element composition and incompatible element enrichment, typified by their (La/Sm)N ratios. Tholeiitic samples with (La/Sm)N of ∼1.2 are comparable with lavas constituting three young volcanic fields closer to the spreading axis. The other two lava series from Easter Island and the two seamounts are transitional to slightly alkaline, one having an intermediate enrichment with (La/Sm)N of 1.5–2, the other being even more enriched [(La/Sm)N ∼2.3]. Large phenocrysts and xenocrysts of olivine and plagioclase in the submarine lavas indicate a crustal reservoir with crystallizing magma. Compared with the relatively mafic submarine samples, the more fractionated lavas on Easter Island suggest the presence of another, more shallow magma chamber. The extreme differentiation of rhyolites and trachytes probably occurred as a result of decreasing magma supply during waning phases of volcano activity. Each volcano of the Easter Hotspot probably evolved through at least two stages. A tholeiitic stage appears to form large volcanoes at depths <1000 m and is succeeded by a transitional group of lavas which can be observed on Easter Island. A third stage with the most enriched lavas may form small eruptive centres on the flanks of older volcanoes or as flank cones on the seafloor. The degree of partial melting decreases from the tholeiitic to the most enriched alkaline series. The occurrence of different stages of volcanism at the Easter Hotspot not only resembles the magmatism of other Pacific hotspots such as Hawaii but also the volcanism of non-plume near-ridge seamounts at the East Pacific Rise. We suggest that the development of each magmatic stage depends on the age of the overlying plate, which determines (1) the amount of depleted mid-ocean ridge material mixed into the magma source and (2) the degree of partial melting. [ABSTRACT FROM AUTHOR]