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Early Paleozoic A-type granites in South China are rare, and their petrogenesis is still highly debated. This study focuses on the controversial Epo pluton in the Wuyi-Yunkai Orogen and conducts petrological and petrogeochemical research to discuss its origin. The Epo granites were emplaced at approximately 414 Ma and exhibit petrological and geochemical features of A-type granites. They contain only one ferromagnesian mineral, ferrum biotite. The granites mostly have high alkalis contents (Na2O + K2O = 6.48–8.85 wt.%), high field strength element (HFSE) contents (Zr + Nb + Ce + Y = 353–461 ppm), and high Ga/Al (104×Ga/Al = 2.50–3.72) and FeOT/(FeOT + MgO) (0.74–0.85) ratios. Besides, they formed under high-temperature (>850°C) and low-pressure (≤5 kbar) conditions. Their high A/CNK (average 1.20) and Eu/Eu* (average 0.46) values as well as Sr (average 128 ppm) and Ba (average 628 ppm) contents but relatively low Zr contents (approximately 200 ppm) further suggest a strongly peraluminous A-type affinity, a distinctive subtype of A-type granites. The Epo granites display enriched Sr-Nd-Hf isotope compositions with a whole-rock87Sr/86Sri average ratio of 0.712, whole-rock εNd(t) values ranging from − 8.9 to − 7.6, and zircon εHf(t) values clustering at − 8. Their two-stage Nd and Hf isotope model ages are 1.7 Ga to 2.0 Ga, suggesting ancient crustal sources. Furthermore, Nb/U (average 7.46), Ce/Pb (average 4.06) and other trace element ratios indicate negligible contributions from juvenile mantle materials. Our data on the Epo pluton, coupled with other contemporary A-type granites in South China, suggest that the high-temperature melting of metasedimentary basements generated strongly peraluminous A-type granites, while the involvement of metaigneous rocks or mantle-derived magmas resulted in metaluminous to weakly peraluminous A-type granites. Source diversity leads to different aluminium saturations. The heat required to produce high-temperature A-type magmas was supplied by upwelling mantle-derived magma in a postcollisional extensional setting. [ABSTRACT FROM AUTHOR]

The Sakarya Zone (northern Turkey) is characterized by the emplacement of voluminous granitoids during the late Carboniferous. In this study, we present geological, U-Pb zircon age, elemental abundance and Sr-Nd-Pb isotopic data on two highly evolved Carboniferous granite bodies within the Early to Late Jurassic volcaniclastic rocks in the Şiran region. The largest body forms a roughly E-W trending ~30 km long and 0.5–2.5 km wide stripe the southern boundary of which is a southvergent thrust, and the other one a subcircular outcrop, ~5 by ~3 km, unconformably overlain by Lower Jurassic volcaniclastic rocks. Their emplacement ages are constrained by LA-ICP-MS U-Pb zircon dating to 310–313 ± 7 Ma (2σ, late Carboniferous). The granitic rocks consist of quartz, microperthitic K-feldspar, plagioclase, and minor biotite, and are characterized by highly evolved compositions with high concentrations of SiO2, Na2O, K2O and Ba, and low concentrations of TiO2, Fe2O3*, MgO, CaO, P2O5 and Sr. Geochemical characteristics indicate a highly fractionated high-K calc-alkaline peraluminous I-type affinity. Chondrite-normalized rare-earth element (REE) patterns are slightly fractionated, with light REEs enriched with respect to middle and heavy ones, and showing variable negative Eu anomalies. On the N-MORB-normalized multi-element variation diagrams, samples display negative anomalies of Ba, Nb, Sr, P, Zr, Eu, and Ti, and positive anomalies of K, and Pb. Initial 87Sr/86Sr and εNd values are 0.70432–0.70610 and −6 to −11, respectively, similar to other Carboniferous high-K calc-alkaline granites and mafic-ultramafic intrusions in the region. The compositional characteristics of the Şiran granites can be explained mainly by fractional crystallization involving hornblende, plagioclase, and biotite and without the involvement of significant amounts of garnet. There is no need to invoke magma mixing and/or melting of a heterogeneous source to account for the geochemical variation. We propose that the late Carboniferous granites formed by remelting of middle- to high-K calc-alkaline mafic rocks at lower crustal depths, followed by extensive fractionation at the upper crustal depths. A thorough review of data from the literature reveals that highly fractionated granites constitute a significant component of the late Carboniferous granites in the Eastern Pontides. [ABSTRACT FROM AUTHOR]

We present U – Pb zircon geochronology and whole-rock Sr-Nd-Pb isotopic compositions of monzonitic plutons from NE Turkey to elucidate their genesis and provide significant insights into the generation of post-collisional I-type shoshonitic magmas. Zircon U – Pb dating of the monzonitic plutons yielded an emplacement of the Middle Eocene (44–39 Ma). Geochemically, the monzonitic plutons are I-type, metaluminous, and shoshonitic in composition, and have high contents of total alkalis and LILE, high ratios of LREE/HREE and LREE/HFSE, and show negative Nb-Ta-Ti and Eu (EuN/Eu* = 0.69–0.84) anomalies. The monzonitic plutons have homogeneous and moderately low initial 87Sr/86Sr (0.70464–0.70495), positive εNd(t) values (0.33 to 1.28), and narrow variation of the initial Pb isotope contents with 206Pb/204Pb (18.74–18.82), 207Pb/204Pb (15.64–15.65), and 207Pb/204Pb (38.81–38.90). The combined use of whole-rock trace elements and isotopic compositions with regional geology suggests that parental magmas of the monzonitic plutons were generated from mainly melt-metasomatized sub-continental lithospheric mantle source and lesser crustal components in an extensional orogenic setting, and then monzonitic magmas have evolved by dominantly fractional crystallization in crustal levels. [ABSTRACT FROM AUTHOR]

The Ririwai anorogenic alkaline complex harbours extensive rare metal (Nb-Zr-Sn-Zn) mineralization. However, uncertainty still surrounds their origin and magmatic-hydrothermal processes responsible for their rare metal mineralization. The complex is composed of peralkaline arfvedsonite ± albite-bearing granites, mildly peralkaline fayalite-bearing granite porphyries, and weakly peraluminous biotite-bearing granites, all of which show diagnostic A1-type characteristics. Zircon U-Pb dating reveals emplacement ages between 181.4 ± 0.81 and 188.6 ± 7 Ma for the three rock units. Sm-Nd and Pb isotopes (εNd (t) = –0.6 to −5.4, 206Pb/204Pb = 17.68–17.93) constrained the Ririwai A-type granites to represent highly fractionated products of enriched mantle-derived magmas. Mass-balance modelling suggests that magma evolution was fuelled by extensive fractional crystallization of 50 ~ 60 vol.% K-feldspar, 30 ~ 35 vol% fayalite, 5 ~ 10 vol.% amphibole, and ~ 5 vol.% apatite under reduced and water-undersaturated (ΔFMQ = –1.55; logfo2 = –18.63; H2O = <2.0 wt.%) conditions and assimilation of ~ 50 vol.% crust. Whole rock and amphibole compositions revealed an increasing degree of fractionation from the fayalite-bearing granite porphyries through biotite-bearing granites to the arfvedsonite ± albite-bearing granites. This extended fractionation at the late stage of magma differentiation, facilitated by fluorine dissolution and concentration of excess HFSE and REE as alkali-fluorocomplexes in the fluorine-rich silicate melt, allowed the accumulation of economic rare metal pyrochlore and columbite mineralizations in the highly fractionated arfvedsonite± albite- and biotite-bearing granites, respectively. Nonetheless, the metasomatic reaction rim textures around the magmatic pyrochlore, coupled with the M-type lanthanide tetrad effect (TE1,3 >1.10) indicate the subsequent effect of hydrothermal processes. Tectonically, reactivated shear fractures and transcurrent faults following lithospheric stresses in a transtensional regime allowed magma uprising and emplacement of A-type granites in the Ririwai complex. [ABSTRACT FROM AUTHOR]

The subduction-related Sunda-Banda arc hosts several giant and major Cu–Au–Mo porphyry and epithermal Au systems, making it one of the most important magmatic-related metallogenic belts in Indonesia. They are accompanied by a number of smaller systems, one of which is the recently discovered Randu-Kuning porphyry Cu-Au deposit on Java Island. The present study investigates the geochemical characteristics of this deposit through whole-rock and mineral geochemistry and mineral geothermobarometry, focusing on three sequential dioritic intrusions that make up the host igneous complex, two barren and the third mineralized. Moreover, a comparative analysis is performed between other porphyry deposits in the Sunda-Banda arc and with Grasberg in Papua. This study shows that the older porphyry deposits have mostly similar geochemical characteristics to the younger deposits, suggesting the same magma source, which is mantle-derived oxidized I-type magma. Amphibole geothermobarometry shows that the formation of syn-ore intrusion in the older porphyry was higher in temperature and pressure than those at the younger porphyry. The halogen and oxygen fugacities inferred from biotite and amphibole chemistry indicate an oxidized, water- and halogen-rich melt. Our study shows that combining amphibole and biotite chemistry and whole-rock geochemical data is useful to fingerprint the magmatic-hydrothermal processes, especially where multiple magmatic phases occur. This research also provides valuable insights into the magmatic-hydrothermal physiochemical conditions during the formation of the mineralized system. [ABSTRACT FROM AUTHOR]

Let S be a groupoid (magma) with zero 0, and let R = ⊕ s ∈ S R s be a contracted S-graded ring, that is, an S-graded ring with R 0 = 0. By G (H R) we denote the undirected power graph of a multiplicative subsemigroup H R = ∪ s ∈ S R s of R, and by G * (H R) a graph obtained from G (H R) by removing 0 and its incident edges. If Re is a nonzero ring component of R, then G * (R e) denotes a subgraph of G * (H R) , induced by R e *. In this paper we address a problem raised in [Abawajy, J., Kelarev, A., Chowdhury, M.: Power Graphs: A Survey. Electron. J. Graph Theory Appl. 1(2), 125–147 (2013)]. Namely, let S be torsion-free, that is, s n = t n implies s = t for all s, t ∈ S , and all positive integers n, and let S be 0-cancellative, that is, for all s, t, u ∈ S , su = tu ≠ 0 implies s = t , and us = ut ≠ 0 implies s = t. Also, let R be semisimple Artinian. We prove that if G * (R e) is connected for every nonzero ring component Re of R, then the connected components of G * (H R) are precisely the graphs G * (R e). [ABSTRACT FROM AUTHOR]

The surface gap of tephriphonolite compositions in the Passa Quatro alkaline complex, in SE Brazil, is attributed to non-buoyancy of these high viscosity intermediate compositions during magmatic fractional crystallization at different depths. Thermodynamic and Rayleigh models for three alkaline suites of a strongly silica-undersaturated series were integrated to demonstrate that parental (basanite, nephelinite and alkaline basalt) and residual (phonolites) magmas are cogenetic by fractional crystallization at pressures of 10 kbar and 5 kbar, i.e. at magma chambers located above and below the Conrad discontinuity within the Upper Cretaceous-Palaeogene 40 km-thick continental crust in SE Brazil. The fractional crystallization of the parental magmas produced an ultramafic residual solid (wehrlite, olivine-bearing clinopyroxenite and clinopyroxenite) and residual liquids (evolved basanite and alkaline basalt, and phonotephrite). The latter moved up and built magma chambers at lower depths in the continental crust where those magmas initially crystallized clinopyroxenite extracts and high viscosity residual liquid that was entrapped and prevented to ascent towards the surface. Then, an abrupt change in the extract mineralogy produced a feldspathic-rich extract (leucocratic leucite monzosyenite, mesocratic syenite or leucocratic monzodiorite) and a residual phonolitic liquid with low viscosity. Following the feldspar crystallization, the magma viscosity decreased, acquiring adequate buoyancy that resulted in shallow-crust magma chambers in which phonolite diversification took place. These processes occurred due to the existence of a transcrustal, plumbing architecture where the high viscosity intermediate tephriphonolites were prevented to reach shallower depths, resulting in the Daly gap observed in the Passa Quatro Alkaline Complex. [ABSTRACT FROM AUTHOR]

We propose that the 495-470 Ma Ollo de Sapo magmatism in the Iberian Massif was the result of a mantle plume event in the Furongian-Early Ordovician. This plume was located beneath the northwestern margin of Gondwana and caused rapid and extensive melting of Ediacaran arc-related crustal rocks and their derived sediments. Mafic magmas due to plume partial melting underplated the crust and were emplaced at mid-lower crustal levels (~15km), and provided the heat for crustal melting. Manifestations of the plume include (i) pronounced magnetic anomalies in the region which match the distribution of Ollo de Sapo rocks, (ii) the Toledanian unconformity (and gap), which is attributed to thermal doming, and (iii) the significant thickness variations in Lower to Middle Ordovician sedimentary successions in adjacent areas. In a more regional context, we infer that the plume was one of a cluster of plumes impacting the Gondwana periphery and that it contributed to the birth and development of the Rheic Ocean throughout Gondwana margin breakup. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that thermal models clearly demonstrate that crustal magma bodies should solidify rapidly upon emplacement. Small plutons can cool below the solidus in thousands of years, while even large plutons require hundreds of thousands of years, but not more than a million years. However, recent U-Pb zircon geochronological data contradict these results, strongly suggesting that magmatic systems are often characterized by protracted events. Therefore, a conceptual framework that reconciles thermal models and the geochronology data is necessary. The Devonian foreland magmatism of the Sierra de San Luis is made up of two distinctive suites, the Monzonite suite (<65 wt.% SiO2) and the Granite suite (>65 wt.% SiO2), both emplaced at ca. 3.7 kbar. Classification of the studied Devonian granitoids is debatable because they have a hybrid I- to A-type granite signature. Based on a robust geochronological U-Pb zircon dataset we corroborate the development of a protracted magmatic activity with three major crystallization events for this Devonian magmatism: 391 ± 1, 384 ± 1, and 379 ± 2 Ma. Considering these geochronological data, we postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the prolonged crystallization of antecrysts (ca. 395–384 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located at shallow levels, where zircon autocrysts crystallized (ca. 379 Ma). Age spectra reported within individual samples support the idea of a massive migration of magma when conditions were favourable (e.g. thermally matured crust). Individual crystallization ages recorded by monazites hosted in two-mica granites are comparable to those obtained from zircons, supporting the presence of a long-lasting hot source. Additional geochronological data indicate that a later thermal event (ca. 353 Ma) could have partially affected some areas of the Devonian magmatic zircons promoting Pb loss, with subsequent partial resetting of the isotopic clock. [ABSTRACT FROM AUTHOR]

The Okinawa Trough is an incipient back-arc basin formed by the subduction of the Philippine Sea Plate beneath the Eurasian Plate and is a natural laboratory for studying basin evolution, magmatism, and crust-mantle interactions during the early stages of back-arc spreading. Back-arc spreading and recent magmatism are occurring mainly in the Middle Okinawa Trough (MOT) and Southern Okinawa Trough (SOT). In order to investigate the magmatism in the Okinawa Trough, volcanic rock samples from the MOT and SOT were analysed for Fe – Sr – Nd – Pb – Hf isotopic compositions. The Fe isotopic compositions of basaltic andesite samples from the SOT are similar to or lower than MORBs. The fluid/melt derived from the subducted slab, especially the fluid dehydrated from slab serpentinites and sediment-derived melts, entered the overlying depleted mantle wedge and participated in magma generation, which resulted in the low δ56Fe values of the SOT basaltic magmas. The δ56Fe values of volcanic rocks from the MOT increase with increasing SiO2 contents, suggesting a gradual enrichment of heavy Fe isotopes during the evolution of the magma as it ascended to the surface. While the Sr – Nd – Pb – Hf isotopic compositions do not vary significantly, suggesting that the different samples are the products of different degrees of crystal fractionation of comagma. The fractional crystallization of olivine, pyroxene, and ilmenite minerals, which enrich in light Fe isotopes, resulted in the gradual increase in Fe isotopic values of magma during its evolution. The dacites and rhyolites from the southernmost Okinawa Trough have the similar δ56Fe values with the basaltic andesite and the basalt from the SOT and MOT, accompanied by significantly lower Nd and Hf isotope ratios relative to basalts, reflecting that the contamination of crustal materials would not change the magma in Fe isotope compositions evidently. Compared with the MOT, the volcanic rocks from the SOT was more affected by subduction components on their underlying mantle, and those from the southernmost experienced more contamination by crustal materials in the evolving magma. [ABSTRACT FROM AUTHOR]

This study provides new constraints on the causes of the chemical and isotopic variability in the central Victorian, Devonian, silicic, magmatic rocks and relates these to crustal architecture in the region. Synthesising present and previous work, it is concluded that the Selwyn Block, which forms the main source region for the Devonian silicic magmas (granitic and silicic volcanic rocks), is heterogeneous in three dimensions, on scales of 1 km and less. The sources of both the I- and S-type magmas were formed in Paleoproterozoic to Mesoproterozoic times, in the distal back-arc region of an Andean-type margin, in a basin that was extending and deepening eastward with time. The prominent rock types are high-grade metamorphosed greywackes, potassic andesites and dacites, with smaller volumes of pelitic rocks. The metasediment-dominated source rocks generally lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. This means that the I-type magmas were generally at lower temperatures and were also more hydrous than the S-type magmas. Heat for the metamorphism and partial melting of the source rocks of the silicic magmas was advected into the crust by mantle-derived magmas. These probably formed an underplate, to drive the regional metamorphism, but numerous, scattered, sill-like mafic bodies caused local contact anatexis and silicic magma production. Along with the emplacement of mafic magma bodies, the ascent of the silicic magmas to the upper crust rendered the deeper parts of the Selwyn Block denser and more mafic. The largely unexposed Selwyn Block, which forms the crustal basement in central Victoria, is heterogeneous in three dimensions, on scales of 1 km and less. The sources of the Devonian I- and S-type silicic magmas here formed in the Paleoproterozoic to Mesoproterozoic distal back-arc of an Andean-type margin. The metasedimentary S-type source rocks lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. Heat for the metamorphism and partial melting was advected by both underplating and numerous sill-like mafic bodies scattered throughout the deep crust. [ABSTRACT FROM AUTHOR]

Lake Taupō, New Zealand, conceals a large caldera volcano which last erupted in 232 AD. A surveying experiment in 1979 which utilised the surface of the lake for detecting small movements of the lakebed soon became a programme to monitor vertical deformation by making regular observations at 22 fixed points – survey stations – around the lake. The programme continues today with 4 surveys being made annually. In this paper, we review the methodology and present the 42 year-long dataset in graphical forms, and draw conclusions on its implications in terms of volcanic and tectonic deformation. We also make the dataset available for download. The dataset confirms that vertical deformation is occurring in the lakebed. Long periods of slow deformation, dominated by subsidence totalling 140 mm in the Taupō Fault Belt at the northern end of the lake, and to a lesser degree at the southern end, are interrupted by uplift episodes now reaching 160 mm in the northeastern sector containing the most recent active vents. We suggest that the subsidence is primarily tectonic while inflation episodes are driven by upward migration of magma to shallow levels during periods of unrest. [ABSTRACT FROM AUTHOR]

Plate tectonics plays a crucial role in the evolution of Earth's continents and oceans. However, the impact of oceanic subduction and continental collision on the continental lithospheric mantle within collisional orogenic belts is still a matter of debate. To address this issue, we performed a thorough analysis of mafic rocks in the Nixiong area within the central Lhasa Terrane, southern Tibet. The mafic rocks are composed of diabases and basalts formed during syn-collisional period (~50 Ma). The diabases have low SiO2 and moderate MgO contents, and are enriched in large ion lithophile elements and depleted in high field strength elements. They show high 87Sr/86Sri (0.711451–0.712084) and low εNd(t) (−7.9 to −6.44), as well as enriched Hf-Pb isotope compositions (εHf(t) = -7.58 to −6.59; 206Pb/204Pbi = 18.59–18.71; 207Pb/204Pbi = 15.71–15.72; 208Pb/204Pbi = 39.33–39.53). Geochemical modelling suggests that the diabases were formed through the partial melting of peridotite at high temperatures and shallow depths, with significant addition of subduction-related components to the primary melts. The diabases probably originated from a metasomatized lithospheric mantle due to subduction of Neo-Tethyan slab. The basalts display similar SiO2 but lower MgO contents compare with the diabases. They are also characterized by extremely high 87Sr/86Sri (0.713332–0.713448), low εNd(t) (−10.32 to −9.96), and significantly enriched Hf-Pb isotope compositions (εHf(t) = -12.30 to −12.05; 206Pb/204Pbi = 18.81–18.85; 207Pb/204Pbi = 15.74–15.75; 208Pb/204Pbi = 39.81–39.88), corresponding to an extremely enriched lithospheric mantle. Integrated with the previous studies, the Nixiong mafic rocks exhibit the most enriched isotopic compositions among the arc- or syn-collision-related mafic rocks in southern Tibet. These extremely isotopically enriched components were most likely derived from the ancient continental lithospheric mantle beneath the central Lhasa Terrane. Our results provided unambiguous evidence that the pre-existing ancient continental lithospheric mantle could persist locally during the prolonged oceanic subduction and subsequent continental collision. [ABSTRACT FROM AUTHOR]

The Ailaoshan orogen in SW China records the evolution of the Ailaoshan Paleo-Tethyan ocean and the amalgamation history between the South China and Indochina blocks, an important process for the formation of Southeast Asia. However, its tectonic evolution remains ambiguous with various competing models. We have carried out an integrated geochronological–petrological–geochemical study for the granites, dacites-rhyolites, granodiorites and trachyandesites in this orogen to give new constraints on this issue. The 255–254 Ma granites and the 250–248 Ma dacites-rhyolites show similar geochemical features and are characterized by strongly peraluminous nature, continental crust-like trace element patterns and negative zircon εHf(t) values (−14.4 to −6.6), indicating they derived from partial melting of ancient crust. The 229 Ma hornblende-bearing granodiorites are metaluminous to weakly peraluminous (A/CNK = 0.96–1.01) and belong to high-K calc-alkaline I-type granites. They show depleted whole-rock Sr-Nd and zircon Hf isotope compositions (initial 87Sr/86Sr = 0.7027 to 0.7038, εNd(t) = 4.0 to 4.1, εHf(t) = 9.3 to 11.5), suggestive of derivation from partial melting of juvenile mafic crust. The 226 Ma trachyandesites are characterized by high MgO (4.1–4.6 wt.%), high Mg# (56) and arc-type geochemical affinities with enriched isotope compositions (initial 87Sr/86Sr = 0.7108 to 0.7111, εNd(t) = −7.7 to −7.5, εHf(t) = −6.3 to −3.5). These features indicate that their parental magmas derived from partial melting of enriched lithospheric mantle metasomatized by oceanic sediment-derived melts. These new data, in conjunction with spatial-temporal-temperature variations of igneous rocks, metamorphic records and stratigraphic changes in the region, suggest that the Ailaoshan Paleo-Tethyan ocean closed at the Early Triassic (ca. 250 Ma) which was followed by the Late Triassic postcollisional slab breakoff, and the ocean experienced westward unipolar subduction during its evolution with no assumed eastward subduction. [ABSTRACT FROM AUTHOR]

The sedimentary successions of the Permian-Triassic rifting related to the Alpine Tethys in the easternmost Lower Alpujarride units (Internal Betic Zone, south Spain) host shallow-intrusive basic bodies of Mesozoic age. These gabbroic bodies experienced low-grade Alpine metamorphic overprint, singularly recorded in three outcrops nearby Alicante city in southeast Spain: Callosa and Orihuela Ranges and Nueva Tabarca Island. Overall, the metabasic bodies still preserve magmatic ophitic/subophitic texture and relicts of magmatic augite and ferropargasite-ferroedenite-edenite and kaersutite. In contrast, metamorphic minerals include magnesioriebeckite, actinolite, albite, stilpnomelane, phengite, and chlorite. Major and trace element geochemical data suggest crystallization of the igneous protoliths from subalkaline (tholeiitic) to alkaline within-plate (continental) basaltic magmas slightly enriched in incompatible elements. These magmas with E-MORB geochemical affinity very likely intruded at shallow crustal levels in an extensional-synrift-geodynamic setting related to the breakoff of Pangea in the region. Pressure-Temperature (P-T) conditions estimated by average P-T method and pseudosection calculations suggest metamorphic peak at ca. 6 kbar at 340°C consistent with burial metamorphism down to ca. 18 km depth with intermediate thermal gradients of ca. 18°C/km. These conditions are different to the typical subduction-related blueschist facies conditions of the Lower Alpujarride units and suggest, instead, a collisional (Barrovian) event. This can be explained by a late-stage accretion of the studied units after the main subduction-related event, pointing to the dispersion of the corresponding Lower Alpujarride sections along the margin in different palaeogeographic positions before deformation and movement to their actual structural position. The metamorphic correlation of the studied units with the accreted passive margin of South Iberia (Subbetic zone) is also discussed. [ABSTRACT FROM AUTHOR]

Detailed textural and compositional study of calc-alkaline lamprophyres and minettes from Zeneta, SE Spain Neogene Volcanic Province (NVP) are used to unravel the magma sources and differentiation processes involved in their formation. The presence of xenocrysts of various origins indicates a hybrid nature involving mantle-derived alkaline lamproitic and continental crust-derived granitic parental magmas. A new U-Th-Pb zircon age of Zeneta minettes allows contextualizing their generation in time and space during regional lamproite magma intrusion and crustal anatexis in the NVP. Interaction and mixing of these compositionally contrasted magmas resulted in the formation of hybrid calc-alkaline lamprophyre minette. This process is reflected by the phases that crystallized from the hybrid magma, particularly phlogopite, and by the whole-rock composition of the less fractionated rocks. The calculated contribution of lamproitic and crustal-derived magma end-members in minette formation are 30–40% and 60–70%, respectively. Mixing of end-member magmas of contrasting rheological properties was possible only in a calculated thermal-window of 1025–1125°C, after cooling of intruding lamproitic magma and heating of host granitic anatectic region. The calculated thermal window fits with the estimated rheological properties of Zeneta minettes and the crystallization temperature of early minette-derived phlogopite. Furthermore, fractional crystallization was identified for the first time in the Zeneta minettes, based on the observed whole-rock line of descent from the less evolved mixed magmas through intermediate to felsic minettes and associated textural and compositional features of late crystallized phases. Polytope Vector Analysis allowed an integrated quantitative characterization of magma differentiation, including magma mixing and subsequent fractional crystallization. The identification of mixing and fractionation processes in calc-alkaline minettes genesis, which otherwise does not show spatial and temporal association in the field with granitic bodies, opens a new scenario to be considered in understanding the petrogenesis of these rocks. [ABSTRACT FROM AUTHOR]

Mantle xenoliths from Santo Domingo, Ventura-Espíritu Santo and Durango volcanic fields (Mesa Central in Mexico) experienced low degrees of partial melting in the stability fields of garnet (⁓ 2%) and spinel peridotites (⁓ 2–4%), and interacted with hydrous alkaline melts possibly during the Basin and Range extensional tectonism since Late Oligocene. Enclosed and intergranular grains of monosulfide solid solution (mss) in Santo Domingo peridotites are residues after the extraction of 0.1–0.5 fractions of Ni-Cu-rich sulphide melt during mantle melting events. On the other hand, glo˜bular sulphides (pentlandite ± chalcopyrite) hosted in glass veinlets in the Ventura-Espíritu Santo and Durango peridotites crystallized from Ni-Cu-rich droplets of sulphide melt, immiscible in the Quaternary silicate magmas that brought the xenoliths to the surface. Rhenium-depletion model ages of these sulphide populations indicate that part of the subcontinental lithospheric mantle (SCLM) of the Oaxaquia terrane (beneath Santo Domingo and Ventura-Espíritu Santo) originated in the Archaean-Paleoproterozoic as the southernmost extension of the Laurentia craton, and was assembled with the Central terrane (beneath Durango) during the Grenville orogeny (⁓ 1.0 Ga). Early Palaeozoic (⁓ 500 Ma) model ages common to sulphides from the peridotite xenoliths of the three volcanic fields suggest that the Oaxaquia-Central composite block split away from North America during the Rodinia break-up and experienced the Pan-African-Brasiliano orogeny that led to Gondwana assembly. During the Cenozoic, the reactivation of translithospheric faults bounding this composite old SCLM provided preferential pathways for focusing the ascent of ore-productive magmas/fluids associated with the subduction-related metallogeny of the Pacific active margin of Mexico. [ABSTRACT FROM AUTHOR]

Contamination is a common scenario of intracrustal magmatic processes that may significantly change the compositions of involved anatectic melts. Here, we present major element and B isotope analyses on tourmalines from the Guowu leucogranite and their host rocks, which allow us to unravel the potential contaminations of the Himalayan leucogranites by metapelite host rocks. Three types of tourmaline have been identified in our samples. Tur-M in the host schist has the highest Mg/(Mg+Fe) ratio (0.52–0.62) and low Al content, suggesting its metamorphic character. Tourmalines in the leucogranite (Tur-L) and in the contact zone between leucogranite and schist (Tur-C) have an identical core-rim texture, and their cores are characterized by the lowest Mg/(Mg+Fe) ratio (0.13–0.18) and high Al content, which are consistent with the composition of magmatic tourmaline in the Himalayan leucogranites. The rims of Tur-L show higher Mg/(Mg + Fe) ratio (0.32–0.45) and moderate Ca, Ti, F contents, reflecting the contribution of the host schist via contamination. The composition of Tur-C rims is similar to that of Tur-M, suggesting a more significant contribution from contaminated schist than that for Tur-L. The different types of tourmaline share consistent B isotope compositions with δ11B ranging from −14 to −12‰. The compositional characteristics of the contaminated tourmaline and the mineral assemblage in the contaminated zone suggest that the involved components derived from the host schist, probably produced by the decomposition of tourmaline, biotite, plagioclase, primarily include Ca, K, Mg, Ti, B and F. In addition, contamination by tourmaline-bearing metapelite may be an alternative interpretation responsible for the peraluminous character of the Himalayan leucogranites. The occurrence of contaminated tourmaline in leucogranites suggests that contamination of host rocks is a possible way promoting the formation of tourmaline in the Himalayan leucogranites, and tourmaline is useful for deciphering the related contamination processes. [ABSTRACT FROM AUTHOR]

Arc magmatism plays a key-role in the growth and differentiation of continental crust. In particular, the prolonged magmatic flux events control the genesis of deep crustal hot zones where magma accumulation and fractionation favour the continental arc crust evolution and geochemical stratification. In this view long-lived magmatic systems located in arc domains, with their erupted products spanning from basalts to rhyolites are formidable archive for the understanding the evolution of transcrustal magmatic plumbing systems and the construction of a stratified continental crust. This study focuses on the long-lived (ca. 9 Ma) Miocene-Holocene Cordillera de San Buenaventura volcanic system in the Southern Puna Plateau (NW Argentina), a unique natural laboratory where exploring the building up of MASH-zones (or deep crustal 'hot zones') and related sustained volcanism. Synthesis of new and published data, together with new thermobarometry and fractional crystallization modelling, indicates a cyclic scenario with mantle melts undergoing fractional crystallization dominated incipient and waning stages alternate to major mafic magma recharge events during the building up phase of the MASH-zone. This magmatic scenario is also discussed in the light of the coeval geodynamic framework dominated by the subduction of the Nazca plate and the eastward migration of the frontal arc magmatism. [ABSTRACT FROM AUTHOR]

The magmas that formed each Devonian, S-type, volcanic complex in central Victoria were generated through partial melting of a distinct assemblage of rock types in the crustal source region. The more silicic rhyolites were formed independently of the rhyodacitic to dacitic magmas, rather than as differentiates. Within every complex, each ignimbritic unit is also heterogeneous in its chemical and isotopic characteristics. Thus, in this part of Paleozoic Australia, magma heterogeneity occurred on at least three scales—the individual rock unit, the complex and across the region. This means that the Selwyn Block, the logical source of the ignimbrite magmas, is highly heterogeneous, probably in three dimensions. The statistically significant differences in the ages of the various complexes suggest that the heat sources for partial melting of the deep crust were themselves rather local in extent, and probably reflected numerous asynchronous intrusions of mantle-derived mafic magmas, most likely in relatively small batches. Thus, there should be no thick underplated or intraplated layer of gabbroic rock in the deep crust here. Thinner bodies of hot mafic magmas were probably emplaced in different places and at different levels, inducing local high-grade metamorphic conditions. Published radiometric dates for various volcanic units suggest that the magmatic heating of the crust occurred over a period of at least 17 Myr, although maximum intensity occurred between ca 375 and ca 371 Ma. Thus, a model of the deep crust here should involve numerous, perhaps thin metasedimentary units with highly variable ages and original clay contents, as well as sills of Late Devonian mafic rocks scattered both vertically and horizontally and intruded episodically. The dominantly meta-igneous sources of crustally derived I-type magmas generally lie at higher structural levels, where they did not experience metamorphic temperatures sufficient to cause the higher-temperature melting reactions needed to form I-type volcanic magmas. Each Late Devonian, S-type, volcanic magma in central Victoria formed through melting of a distinct assemblage of crustal source rocks, most likely within the Selwyn Block. The rhyolites formed independently of the rhyodacitic to dacitic magmas, not as differentiates. The mafic magma heat sources for partial melting of the deep crust were emplaced as numerous, relatively small batches, in sheets distributed horizontally and vertically. The dominantly meta-igneous and shallower crustal sources of I-type magmas did not experience the higher temperatures required to form I-type volcanic magmas. [ABSTRACT FROM AUTHOR]

In central Victoria, inherited zircon in Devonian igneous rocks and detrital zircon in metasedimentary country rocks and an amphibolite-facies xenolith show that Mesoproterozoic parts of the underlying Selwyn Block cannot be the source for all the silicic magmas. Zircon inheritance in S-type samples reveals significant thermal events at 525–425 Ma and 1200–1100 Ma. Both S- and I-type samples have prominent zircon age peaks at 420–410 Ma, which record high-grade metamorphism of the deep crust during the terminal phases of the Benambran and Bindian orogenies. All I-type rocks have 650–500 Ma peaks, suggesting derivation from an arc-related metavolcanic source in the upper Selwyn Block. Protoliths of the greenschist-facies Ordovician metasediments and the amphibolite-facies Cambrian metasedimentary xenolith were deposited in distal backarc settings. Most inherited zircon cores are metamorphic, and the strongest zircon inheritance occurs in hornblende-bearing I-type rocks, highlighting their largely crustal origin. Zircon populations at ca 1400 Ma, thought to signal sediment derivation from East Antarctica and Rodinia-Nuna, are mostly absent in I-type samples and some S-types. The ca 1400 Ma signal probably applies to the upper, metasedimentary Selwyn Block, so Devonian S-type magmas were sourced mainly in the deeper sections. Zircon inheritance in the Devonian igneous rocks was not influenced by the exposed metasedimentary country rocks. Two samples from one of the smaller plutons have contrasting patterns of zircon inheritance, suggesting relatively small-scale source heterogeneity. Many rounded and corroded cores in zircon crystals yield the same ages as the crystallisation dates for the rocks, and thus are antecrysts. Higher whole-rock Zr contents generally correlate with higher proportions of inherited zircon, and differentiation does not affect this relationship. The degree of partial melting of a magma source and the efficiency of crystal entrainment are critical in governing zircon inheritance. Mesoproterozoic sections of the Selwyn Block cannot be the sources for all the Devonian silicic magmas in central Victoria. I-type rocks have 650–500 Ma zircon age peaks, suggesting derivation from arc-related metavolcanic rocks in the upper Selwyn Block. Hornblende-bearing I-type rocks have the strongest zircon inheritance patterns, indicating the largely crustal origins of I-type magmas. Exposed metasedimentary country rocks were not involved in magma genesis. [ABSTRACT FROM AUTHOR]

Mantle magmatism is active in the southern Central Asian Orogenic Belt (CAOB) in the early Permian. This paper discusses contributions from mantle pyroxenite and the onset of the early Permian mantle magmatism based on the whole-rock major elements and Sr-Nd isotopes of the early Permian basalts and mafic gabbroic rocks as well as olivine chemistries. The clinopyroxene-orthopyroxene barometer yields 1.0–3.7 kbar of emplacement pressure for these mafic-ultramafic intrusions. The Ca-in-olivine hydrometer using compositions of the most primitive olivine (Fo≥86 mol.%) yields 2.7–4.1 wt.% H2O for the parental magmas. Thus, the early Permian mafic-ultramafic intrusions formed from hydrous magmas at shallow crusts. The bulk-rock evolution of most of these mafic gabbroic rocks is consistent with the liquid lines of descent of basaltic magmas in the Hark diagrams of MgO, CaO, Al2O3, and Na2O+K2O versus SiO2, suggesting that these gabbroic rocks have melt-like compositions. The gabbroic rocks and associated basalts are characterized by low CaO, high Fe/Mn ratios, and high FC3MS values (FeO/CaO-3*MgO/SiO2), and the primitive olivines (Fo >80 mol.%) have low Ca and Mn contents with expected high Ni contents without sulphide segregation, implying that pyroxenite-derived melts (46–71 wt.%) contributed to the early Permian mantle magmatism. In addition, Sr-Nd isotopic compositions of these early Permian intrusions suggest a mixing mantle source of the enriched mantle I (EMI) and high U/Pb mantle (HIMU) components, recording geochemical signatures of the previously subducted slabs. Mantle pyroxenite formed from reactions between slab-derived (eclogite-derived) melts and peridotite at high pressure. The onset of the early Permian mantle magmatism is possibly related to the lower solidus temperature and higher melt production of mantle pyroxenite (forming a mantle plume) relative to peridotite at high pressure. [ABSTRACT FROM AUTHOR]

This paper proposes a casting improvement process to enable the casting of Al-Cu alloy cylinder heads to achieve the required quality. The hot tearing defects generated in the fire face of the cylinder head during casting were simulated using MAGMA software. The simulation results show that the large wall thickness transition difference in the fire face of the cylinder head is the reason for the large temperature and stress gradient during solidification. Therefore, the first solution was optimised by forming the fire face as a whole into a flat plate, but the fire face centre area stress is still too high. The second optimisation option optimises the cold iron structure of the fire face, the probability of cracking in the fire face is reduced to 17%. These results have important reference significance for the optimisation of the Al-Cu alloy cylinder head hot tearing problem. [ABSTRACT FROM AUTHOR]

(One-value) graph magma algebras are algebras having a basis B = V ∪ { 1 } such that, for all u , v ∈ V , u v ∈ { u , 0 }. Such bases induce graphs and, conversely, certain types of graphs induce graph magma algebras. The equivalence relation on graphs that induce isomorphic magma algebras is fully characterized for the class of associative graphs having only finitely many non-null connected components. In the process, the ring-theoretic structure of the magma algebras induced by those graphs is given as it is shown that they are precisely those graph magma algebras that are semiperfect as rings. A complete description of the semiperfect rings that arise in this fashion, in ring theoretic and linear algebra terms, is also given. In particular, the precise number of isomorphism classes of one-value magma algebras of dimension n is shown to be ∑ j ≤ n p (j) where, for any i ∈ Z + , p(i) is the number of partitions of i. While it is unknown whether uncountable dimensional algebras always have amenable bases, it is shown here that graph magma algebras do. [ABSTRACT FROM AUTHOR]

The Bakoshi-Gadanya area, with widespread Neoproterozoic granites, is located within the Pan-African Trans-Sahara Belt, sandwiched between the West African and the Sahara metacraton. The whole-rock geochemistry, Sr-Nd isotope systematics and LA-(MC)-ICP-MS U-Pb-Hf isotopes of zircon were analysed to shed light on the age and genesis of the Bakoshi-Gadanya granites in the Precambrian basement of the northern western Nigeria shield. The granites are silicic (SiO2: 72.8–77.2 wt.%), ferroan, high-K, calc-alkalic to alkali-calcic in composition, with A-type granite affinities. The ferroan calc-alkalic types range in age from 706.6 ± 1 Ma to 638.4 ± 1 Ma, and the alkali-calcic type is dated at 710 ± 1 Ma. Whole-rock Sr-Nd and zircon Hf isotope systematics have constrained the ferroan calc-alkalic granites to an enriched mantle lithospheric magma source, contaminated by Archaean-Palaeoproterozoic crustal components. On the other hand, the magma that crystallized the alkali-calcic Gadanya granite originated from an enriched mantle source, triggered by reactivation of the lithosphere-scale Kalangai fault during the post 750 Ma major collision between West African Craton and the Saharan metacraton. Both alkali-calcic and calc-alkalic ferroan granites were formed contemporaneously with the last major Pan-African syn-metamorphic deformation in northern western Nigerian shield; thus, they are syn-kinematic granites. Neoproterozoic magmatism at Bakoshi-Gadanya area is related to easterly dipping subduction at the margin of microcontinental blocks in northern western Nigeria shield. Zircon U-Pb-Hf data envisaged both early Neoproterozoic and Cryogenian juvenile magmatic additions in this part of western Nigeria shield. [ABSTRACT FROM AUTHOR]

The relationship between mafic magmatic enclaves (MMEs) and host granitoids is ongoing debate due to their significant roles in understanding deep magmatisms and geodynamic processes. This paper reports on Early Palaeozoic granitoids and associated MMEs from the Delingha pluton in the South Qilian Accretionary Belt (NW China) to constrain their petrogenesis and draw implications. The MMEs, occurring as ellipsoidal to rounded shapes, are andesitic and have the same crystallization age (~445 Ma) and mineral assemblage as the host granitoids. However, minor isotopic differences between them and compositional and textural disequilibria on minerals (e.g. plagioclase and amphibole) do not support a cumulate origin that the MMEs were formed at earlier stage of the same magmatic system, but forcefully reflect magma hybridization processes between mafic and felsic magmas, during which the hybridized magma was broken up into discrete enclaves by convective motion in the host felsic magma. Accordingly, the primitive compositions of the MMEs likely originated from metasomatized mantle wedge source, while mantle-derived melt underplated and partially melted the lower continental crust to form the host rocks with a certain mantle contribution. Thus, the Delingha pluton is the product of crust-mantle interaction at an active continental margin subduction setting rather than syn-collisional environment, indicating that subduction of the South Qilian Ocean located between the Central Qilian Block and the Oulongbuluke Block may have lasted till to ~445 Ma. [ABSTRACT FROM AUTHOR]

Both felsic and mafic intrusions occur in mantle peridotites of the New Caledonia ophiolite (Peridotite Nappe) and record important information regarding the magmatic evolution during subduction initiation. A systematic petrological, geochronological and geochemical study on gabbro/diorite samples from the Peridotite Nappe is performed to explore their petrogenesis. The gabbro is mainly composed of plagioclase, clinopyroxene and amphibole. Most clinopyroxene have been altered to hornblende or actinolite, whereas some amphibole with high Al2O3 (>8 wt%) and low SiO2 (<46 wt%) contents are of a magmatic origin. This suggests that the gabbro crystallized from hydrous melts. The gabbro shows depleted Sr-Nd-Hf isotope compositions, suggesting that the parental magma of the gabbro could have been derived from the depleted MORB-type mantle (DMM) asthenosphere. The gabbro zircon have δ18O values of +4.74-+6.63‰, which are slightly higher than the mantle-like δ18O values of +5.3 ± 0.6‰, indicating the involvement of subduction-related fluids in their genesis. The diorite mainly consists of albite (An1-4) and tremolite. The felsic dikes within the New Caledonia ophiolite, including granitoids, high-Mg felsic dikes and diorites, are oceanic plagiogranites. Extremely low TiO2 contents, roughly negative correlation of Yb and SiO2 contents, REE patterns of plagiogranites and mafic rocks, and compositions of zircon suggest that the plagiogranites were not products of fractional crystallization of MORB but were generated by hydrous melting of mafic protoliths. The diorite zircon show core-rim textures. Both rims and cores yield identical U-Pb ages of 54.6 ± 0.9 Ma vs 54.6 ± 0.6 Ma, and no old inherited cores were identified based on significantly older dates. Our studies show zircon U-Pb ages of ~55 Ma for the gabbro/diorite and titanite U-Pb age of ~53 Ma for the gabbro, which are older than the New Caledonia CE-boninites (51–47 Ma). Therefore, the magmatic evolution of the New Caledonia ophiolite during subduction initiation has been reconstructed. [ABSTRACT FROM AUTHOR]

The Apuseni Mts. is a key area to study the interplay between intra-continental extensional tectonics, sedimentation, and magmatism. These events occurred from ~14.5 to 7 Ma, covering the collision of the Tisza-Dacia mega-unit with the East European Platform at ~11 Ma and formation of a thin-skinned fold-thrust belt in the East Carpathians. The Zărand-Brad-Zlatna basin (~120 km in length) is the main graben system associated with the magmatic activity. To its south, it is bounded by two younger (<12 Ma) sub-basins: Caraci and Săcărâmb both hosting active magmatism. To the north-east, the smaller Roşia Montană–Baia de Arieş–Bucium sub-basin and, to the south-east, the Deva sub-basin are also associated with magmatism. Several andesite intrusions are also known in the northernmost Apuseni Mts. at Moigrad. Volcanism from ~14.5 to ~12 Ma displays a typical calc-alkaline affinity with high 208Pb/204Pb (38.6–38.8) and 207Pb/204Pb (15.65–15.67), moderate to high 87Sr/86Sr (0.7047–0.7085) and low to high δ18Owr (>7‰) values. The younger igneous rocks (<12 Ma) show high Sr/Y and a variable but significant enrichment in LILE up to ~7 Ma, coupled with low 87Sr/86Sr (0.7040–0.7045), low 208Pb/204Pb (38.2–38.6) and 207Pb/204Pb (15.59–15.63), and low δ18O (5.5–5.7‰). The geodynamic evolution of the area started as regional transtensional with rotational tectonics generating horst and graben structures and ended with a transpressional event. This setting provided the conditions for the formation of a large underplated magma chamber at the crust – mantle boundary (MASH zone), in response to hot upwelling convective asthenosphere. Melting of the lower crust and mixing with mantle melts may have played an important part in the magmatic evolution. The spatial and temporal changes in composition were generated in magma at the crust – mantle boundary, with different crustal thicknesses. Further crustal assimilation and minor fractional crystallization in crustal magma chambers were characteristic for each region. [ABSTRACT FROM AUTHOR]

The variation of crustal thickness of an orogenic belt through time will provide critical insights into the switch of tectonic setting. The geochemistry of subduction and collision-related magmatism is indicative of the crustal thickness. Late Palaeozoic magmatic products are prevalent in central west Junggar orogenic belt (C-WJOB), and can be employed to determine the temporal changes in crustal thickness as well as the tectonic evolution. Here, we constrain the crustal thickness and discuss the tectonic evolution of C-WJOB through by integrating Sr/Y and La/Yb ratios, zircon U-Pb ages and Hf isotopic compositions of the Late Palaeozoic igneous rocks. Our results show that the crust of C-WJOB was much thinner (20–25 km) than normal continental crust (average at 33 km) in the Early Carboniferous, and began to thicken from 350 Ma to 330 Ma at a slow rate. Crustal thickening was caused by the addition of subduction-related magma sourced from depleted-mantle but with contributions of subducted sediments. The crust started to thicken significantly at ~330 Ma and reached to a maximum thickness of ~40 km between 322 Ma and 310 Ma. The timing of maximum thickness corresponded with the emplacement of calc-alkaline to high-K calc-alkaline I-type dioritic magmas as well as adakitic magma. These magmas were generated by melting of both depleted mantle and juvenile lower crust, which was probably triggered by underplated mantle-derived basaltic magma. Lastly, crustal thinning happened between 310 Ma and 295 Ma due to regional post-collisional extension, although voluminous granitic magmatism occurred. The granitic magmas were formed by remelting of the juvenile lower crust, with a few contribution of mantle material. This study on the variation of crustal thickness in the Late Palaeozoic C-WJOB provides insight into how integrated geochemical and isotopic data can elucidate the complex histories of orogenic belts. [ABSTRACT FROM AUTHOR]

The Manzanillo Plutonic Complex (MPC) forms part of the Mexican Cordilleran plutonic belt at ~ 19°N. A special feature of the MPC is more than 125 km2 outcrops of gabbroic rocks, thus constituting the largest body of this lithology along the belt. The overall MPC composition is heterogeneous including gabbros and granitoids with or without hybridization structures and minor alkali-rich granites. In contrast to other Cordilleran plutons, MPC intrusives are often strongly deformed and foliated heterogeneous structures with evidence of magma mingling and mixing. U-Pb emplacement and Rb-Sr and K-Ar cooling ages are between 59 and 73 Ma. Four U-Pb gabbro ages from 63 to 65 Ma define the peak of the hybridization event. Although geochemical analyses display considerable differences within MPC members, their Sr-Nd isotopic signatures are highly homogeneous with magmatic primitive εNd parameters between +5 and +6 and low 87Sr/86Sr around 0.7035. Geothermobarometric data provide information for a hot environment for the gabbroic pulse at 3.4–4.9 Kb and >900°C, indicative for depths ~15 km. On the other hand, granitoids show typical Cordilleran characteristics with lower temperatures and shallow emplacement conditions. The MPC shows a unique petrogenetic evolution in the Cordilleran arc; there is no evidence for a relation to other events such as the Early Cretaceous Alisitos arc. [ABSTRACT FROM AUTHOR]

The Guéra Massif of South-Central Chad is composed of collisional and post-collisional intrusive rocks related to the Central African Orogenic Belt. Collisional granites were emplaced at 595–590 Ma but there are a series of post-collisional intrusions that were emplaced at 570–560 Ma. The older granites have zircon U-Pb weighted-mean ages of 569 ± 6 Ma, 568 ± 7 Ma, and 568 ± 6 Ma, whereas the younger granites are 556 ± 7 Ma and 561 ± 6 Ma but all ages are within their maximum uncertainty. Both groups of post-collisional granites are peraluminous, ferroan, and alkali calcic to calc-alkalic but dioritic microgranular enclaves were observed within the older granites. The chemical variability of each group can be explained by fractional crystallization and it is likely that their parental magmas were derived by partial melting of the lower crust. The Nd isotopes of the older rocks (εNd(t) = −9.5 to −1.2) are slightly less enriched than the younger rocks (εNd(t) = −13.1 and −9.1). Moreover, the Nd isotopic compositions appear to indicate the existence of two isotopically distinct regions of the Guéra Massif with one centred on the Mongo (west) region and the other near the El Hidjer to Zan (east) region. The older group was emplaced during a period of crustal thinning after oblique collision and shearing related to the final suturing of the Congo-Saõ Francisco Craton and the Saharan Metacraton. The younger group was likely emplaced after a period of regional WNW-ESE directed crustal shortening. The punctuated nature of deformation/crustal relaxation cycles in the southern Saharan Metacraton suggests that there may have been many small terranes rather than larger cratonic blocks involved in the lithotectonic evolution of the Central African Orogenic Belt north of the Congo-Saõ Francisco Craton. [ABSTRACT FROM AUTHOR]

The Sinemurian Marifil Volcanic Complex at Sierra de Pailemán, located in the east part of the North Patagonian Region, Argentina, includes five lithofacies and three volcanic events. The volcanic activity begins with subaerial pyroclastic-fall deposits, massive lapilli tuffs with eutaxitic textures, and subaerial silicic domes' emplacement. The upper part of the sequence is formed by pyroclastic fall deposits that pass to massive lapilli tuffs and rhyolitic lava flows. These lithofacies indicate the collapse of explosive eruption columns, coeval with small silicic domes' emplacement, and lava-flows' eruption. The volcanic episode at Sierra de Pailemán was generated during continuous magmatic activity because no erosional or unconformity surfaces were recognized. The Marifil Volcanic Complex's age at Sierra de Pailemán is 191.2 ± 1.3 Ma (Sinemurian) and belongs to the V0 phase of volcanism. These rocks are high-K rhyolites, possibly produced by partial melting of the lower crust, promoted by fluids derived from a subducted plate in back-arc settings that change to an intraplate setting. The Lu-Hf isotopes suggest the possibility of magma mixing in the source and recycling or re-melting of a more evolved crust related to subduction zones. The Lower Jurassic magmatic activity in the western North Patagonian Region and the Patagonian Cordillera of Argentina and Chile correspond to continental arcs. [ABSTRACT FROM AUTHOR]

The late Mesozoic tectonic domain of Southeast China transitioned from compression to extension because of the Paleo-Pacific plate rollback. However, the precise timing of the initiation of extensional tectonics remains unclear. This work focuses on the E–W-trending granite belt and the growth strata of Early Cretaceous red beds in Southeast China to establish the extensional tectonic model in Southeast China. The petrogenesis of four granitic plutons from the E–W-trending granite belt in NE Jiangxi is traced on the basis of zircon U–Pb ages and whole-rock major and trace element abundances to elucidate lithosphere evolution in the study area. U–Pb zircon dating reveals the granite emplacement at 130–135 Ma. Geochemical results demonstrate that all granite intrusions can be identified as A-type granites derived from crustal and a few mantle sources respectively through lithospheric thinning and magma upwelling under the extension background. Field observation shows the enlargement of the sedimentary area of the early Cretaceous Huizhou Formation (Fm.) in the Huangshan Basin closely after (or simultaneously) 139 Ma Shiling volcanic activities. The dip angles of the lower part of Huizhou Fm. vary from 49° to 25° towards the basin centre, and the thickness exhibited a slightly increasing trend towards the lower part within the same bed. These phenomena are consistent with the shape of the growth strata. A model, in which the NE–SW-oriented structure lines transfer to the E–W-trending tectono-magmatic belts by meeting and inheriting the previous E–W-trending tectonic axis, is established in the present work. Lithospheric thinning, magma upwelling, and crustal remelting occur within an oblique extension stress field since ca. 140 Ma. Consequently, these phenomena are influenced by the Paleo-Pacific plate rollback and the inheritance of a structural framework from the regional basement series. [ABSTRACT FROM AUTHOR]

Field observations, whole-rock geochemistry, mineral chemistry and zircon U-Pb dating results from microgranular mafic enclaves and their host syenite, Urumieh plutonic complex, NW Iran, show that the enclaves and host are coeval, genetically related and evolved by synchronous magma mixing–fractionation. Geochemically all belong to the shoshonitic series and probably originated from the same enriched subcontinental mantle-derived magma in a subduction setting. SHRIMPU-Pb dating of zircon from representative samples of host rocks and enclaves yields mutually indistinguishable late Cretaceous crystallization ages, 90.7 ± 1.3 and 91.3 ± 1.1 Ma (host syenite), and 90.2 ± 0.7 and 91.6 ± 0.7 Ma (enclaves). Pressure and temperature estimates from Al-in-amphibole and amphibole-plagioclase pairs from both host and enclaves suggest that the interacting magmas mixed and crystallized under similar P-T ‎conditions at middle crustal levels (average 662–716°C and 2.2–2.8 kbar). The occurrence of hybrid to mafic enclaves along with disrupted mafic dikes indicates a long-lived mafic source with ‎multiple replenishments throughout the crystallization history of the complex, and large variability in viscosity within the magmatic system. The transition from mixing to mingling depends on the different crystalline states of the interacting magmas, especially the host magma, which strongly influence rheological properties. In the liquid-liquid state, mixing ‎typically will continue until complete hybridization. With increasing polymerization and crystal load in the host magma, magmatic relationships change progressively from chemical mixing to more mechanical mixing (mingling), producing distributed mafic enclaves, then disrupted mafic dikes, then syn-plutonic mafic dikes as a continuum given sufficient time. [ABSTRACT FROM AUTHOR]

The Mid-Late Mesozoic magmatic arc in southern Qiangtang block was associated with the long-lasting subduction of the Bangong-Nujiang Tethyan and the subsequent Lhasa-Qiangtang collision. The detailed processes associated with the transition from oceanic lithosphere subduction to lithosphere delamination remain unclear. This paper reports zircon U-Pb age, major and trace element and Sr-Nd isotopic data for the Cretaceous two-phase magmatic rocks in the Shuanghu region of the southern Qiangtang block located in central Tibet. Zircon dating on the Qushenla volcanic rocks yields a 206Pb/238U age of 114 ± 4 Ma. The Abushan volcanic rocks comprise rhyolites. Zircon dating on two rhyolites yields a 206Pb/238U age of 74 ± 1 to 76 ± 1 Ma. In contrast with the Qushenla volcanic rocks, the Abushan rhyolites exhibit features typical of high-fractionated I-type granitoids, high K calc-alkaline and shoshonite, and peraluminous, suggesting that the Abushan rhyolites formed in post-collision setting. The Qushenla volcanic rocks have slightly higher initial 87Sr/86Sr (0.70466–0.70537), and εNd(t) (1.71–2.89) in comparison with the Abushan rhyolites (87Sr/86Sr = 0.70453–0.70491, εNd(t) = 1.63–2.35). The Qushenla volcanic rocks were most likely derived from the mixing of mantle-derived components and crustal material. And the crust assimilation and fractional crystallization played a role during the ascent of magma. The Abushan volcanic rocks derived from magmatic mixing between the crustal materials and mantle-derived components, and undergoing extensive fractional crystallization. Taking into account the regional tectonic and magmatic data, we suggest that the transition from the oceanic lithosphere subduction to lithosphere delamination occurred during the Late Cretaceous in central Tibet. It evolved through three stages: 125–100 Ma, late subduction of Bangong-Nujiang Tethys; 100–87 Ma slab break-off of subduction Bangong-Nujiang Tethys; and 87–73 Ma lithosphere delamination. [ABSTRACT FROM AUTHOR]

Late Mesozoic lithospheric extension in NE China resulted in the development of a large extensional province and widespread formation of volcanic-sedimentary basins. The Songliao Basin is the largest one and contains voluminous volcanic rocks composing the majority of the basin fill. This study focuses on two adjacent eruption cycles, the Huoshiling Formation (K1h) and the first member of the Yingcheng Formation (K1yc1), in the Changling fault depression of the Songliao basin, constrains their time ranges and compares the origins of volcanic rocks. Zircon populations from K1h yield U-Pb ages of 124–118 Ma; those from K1yc1 yield younger ones (115–106 Ma). Different volcanic rocks are identified in K1h (alkaline basic rocks, calc-alkaline intermediate-acid rocks) and K1yc1 (alkaline basic rocks, A-type rhyolites), and their geochemistry and isotope characteristics confirm their different origins. The alkaline basic rocks from K1h have the similar magma source as those from K1yc1; both formed under within-plate conditions from an ocean island basalt (OIB)-type mantle source, assumed to be the heterogeneous shallow asthenosphere. The calc-alkaline intermediate-acid volcanic rocks from K1h formed by fractional crystallization of magma, related to the enriched lithospheric mantle, whereas the A-type rhyolites from K1yc1 directly originated from the partial melting of crust newly formed from the depleted mantle. The development of alkaline basic rocks and A-type acid rocks, a typical bimodal volcanic assemblage in K1yc1, requires a relatively thin lithosphere and thus implies that lithospheric thinning reached its maximum during this time (115–106 Ma). However, the rare expression of alkaline basic rocks and the formation of acid rocks mainly by fractional crystallization in K1h indicate that the lithosphere was relatively thick; during this time (124–118 Ma), the lithosphere below the Songliao Basin had just begun thinning. These different stages of lithospheric extension may be due to the intermittent rollback of the Palaeo-Pacific Plate. [ABSTRACT FROM AUTHOR]

In recent years, the word magma has been used to designate a pair of the form (S , ∗) where * is a binary operation on the set S. Inspired by that terminology, we use the notation and terminology M (S) (the magma of S) to denote the set of all binary operations on the set S (i.e. the set of all magmas with underlying set S.) We study distributivity relations among magmas in the context of a hierarchy graph having M (S) as vertices and edges occurring precisely when an operation distributes over another one. The graph theoretic imagery and terminology serve to motivate questions in an intuitive way and to express their solutions in a reasonable fashion. While most considerations are done in general for arbitrary sets, particular emphasis is placed frequently on the case when S = n , the archetypal set with n elements. In that case, parameters such as cardinalities of outsets and insets, fully connected subsets, and longest cycle-free paths are explored. [ABSTRACT FROM AUTHOR]

In this paper, investigating the nonassociative version of groupoids and inverse semigroups, we study the relationship between these two algebraic structures and show that it can not be one-to-one. [ABSTRACT FROM AUTHOR]

We extend the recently obtained result that there exist Graph Magma Algebras that have neither simple nor projective bases to show that, in fact, no Graph Magma Algebra has a projective basis. [ABSTRACT FROM AUTHOR]

To contribute pedagogies that reimagine relationships in a more-than-human world I adopt a posthuman approach to map the content and expressions of imagination in a series of pedagogical events on Dja Dja Wurrung Country, Kooyoora, Australia. By working with Bennett's concept of vibrant matter and MacLure's generative data fragments I attend to the collective – student/teacher bodies, geological landscape, embodied actions, histories, passions and reactions – to interrogate pedagogical assemblages of an imaginative geological walk. In doing so, I explore what holds these assemblages together and what breaks them apart and follow the generative onto-epistemological forces at play. I do so with a posthuman lens to remain open to the possibilities of learning from, with, and in these educational entanglements. [ABSTRACT FROM AUTHOR]

The Northparkes district, central New South Wales, hosts several economic Cu–Au deposits associated with discrete, thin, porphyry intrusive complexes emplaced in the Late Ordovician during formation of the Macquarie Arc. The recently discovered Two-Thirty Cu–Au–(Mo) prospect is a mineralised magmatic–hydrothermal breccia complex that is hosted by the moderately east-dipping Goonumbla Volcanic Complex on the western limb of the Milpose Syncline ∼15 km south of the Northparkes porphyry district. Generation of the magmatic–hydrothermal breccia complex is interpreted to be related to the 448.0 ± 4.4 Ma emplacement of the Two-Thirty porphyry. However, Re–Os dating of molybdenite from the breccia complex indicates a potential for a ca 440 Ma mineralising event that has similar timing to economic porphyry mineralisation in the Northparkes district. The discovery of the Two-Thirty prospect has important implications for exploration in the Northparkes district and the broader Macquarie Arc. Two-Thirty is only the second known occurrence of magmatic-hydrothermal breccia-hosted mineralisation discovered within the Macquarie Arc, with the other being Cadia Quarry. Mineralisation at Two-Thirty is potentially older than the Northparkes and Cadia deposits, and younger than the epithermal and calc-alkaline deposits at Cowal, Marsden and Ridgeway. The Two-Thirty is a polyphase magmatic–hydrothermal breccia complex that hosts Cu–Au (Mo). The Two-Thirty is the first significant breccia-hosted mineralisation found in the Northparkes district. U–Pb zircon crystallisation ages of the causative intrusion at Two-Thirty pre-date mineralisation at Northparkes. Re–Os dates of molybdenite from the Two-Thirty breccia complex are coeval with syn-mineralisation at Northparkes, supporting the model of periodic release of melts and fluids from underlying magma chambers during the formation of porphyry mineralisation in the Northparkes district. [ABSTRACT FROM AUTHOR]

The study of Precambrian tectonics is an intricate task, demanding a holistic approach to take an accurate view of geologic history. Here we attempt to set up the overview of an Orosirian-Statherian continental arc in the northwestern Amazon Craton, the Cauaburi Belt. Field relations, petrological, geochemical, and geochronological data of calc-alkaline metagranitoids, high-grade metasedimentary rocks, and peraluminous metasyenogranites yielded new interpretations about its tectonic evolution. The record of intense and episodic calc-alkaline magmatism between ca. 1805 and 1759 Ma, assign to the Cauaburi Complex, with field evidence of magma mixing and lodgement in a compressional tectonic regime, suggest a continental arc as the tectonic setting. During the magmatic lulls, deformation and metamorphism increase, culminating with the partial fusion of the high-grade metasedimentary rocks of the Taiuaçu-Cauera Complex. This succession composes the precursor paleobasin, presenting maximum and minimum depositional ages of 1819 and 1794 Ma, and was a relevant source for the calc-alkaline magmatism. The geochronological record of a low-volume production of peraluminous crustal rocks (Igarapé Tocandira Granite), with crystallization age at ca. 1791 Ma and metamorphic age at ca. 1771 Ma, also highlights the time and effect of the magmatic lulls. The Cauaburi Belt structural framework follows a general E-W to ENE-WSW trend, expressed in the Paleoproterozoic rocks as syn-magmatic and solid-state deformation fabrics. Assuming that Columbia Supercontinent nucleus assembled in the late Orosirian, we interpret that this coeval continental arc developed at its border and followed a north-south shortening direction, at current orientation. [ABSTRACT FROM AUTHOR]

Ocean-continent subduction drives sequential geologic events, including upwelling of mantle magmas and delamination of thickened lithosphere, which lead to crustal thickness variations and metallic enrichment or depletion at crustal roots. This paper estimates the crustal thickness in eastern Heilongjiang and Jilin Provinces based on La/Yb ratios of crust-derived I-type granites formed by Mesozoic Palaeo-Pacific slab westward subduction beneath Eurasia and assesses the related hydrothermal Cu mineralization. During the flat subduction phase (210–160 Ma), the continental crust dramatically thickened from 32 ± 6 km to 58 ± 6 km, indicating that much mafic magma accumulated under the ancient crust; notably, 210–177 Ma granitoids were generated in the thinner crust because of their normal arc natures, and subsequent remelting of mafic cumulates in the thicker crust formed adakitic magmas (~177–165 Ma) with low MgO (0.03–1.38 wt.%). From 140 to 95 Ma, the steep subduction of the dense slab drove regional decompression and consequent delamination and thinning of the lithosphere from ~58 km to 23 km, inducing explosive volcanic activity along with limited hydrothermal Cu deposition. Most Cu mineralization was associated with normal arc magmas; therefore, we speculate that two key factors were responsible for the small volume of Cu deposition: (1) thinner crust under an extensional setting failed to suppress voluminous pyroclastic eruptions, causing the dissipation of volatiles and preventing a large magma reservoir with long-lasting shallow differentiation; (2) root removal of thickened crust led large volumes of sulphide cumulates, if present, to founder into the mantle rather than remain in the crust, which greatly depleted Cu in the ascending melts. [ABSTRACT FROM AUTHOR]

Mt. Taranaki is an andesitic stratovolcano in the western North Island of New Zealand. Its magmas show slab-dehydration signatures and over the last 200 kyr they show gradually increasing incompatible element concentrations. Source basaltic melts from the upper mantle lithosphere pond at the base of the crust (∼25 km), interacting with other stalled melts rich in amphibole. Evolved hydrous magmas rise and pause in the mid crust (14–6 km), before taking separate pathways to eruption. Over 228 tephras erupted over the last 30 kyr display a 1000–1500 yr-periodic cycle with a five-fold variation in eruption frequency. Magmatic supply and/or tectonic regime could control this rate-variability. The volcano has collapsed and re-grown 16 times, producing large (2 to >7.5 km3) debris avalanches. Magma intrusion along N-S striking faults below the edifice are the most likely trigger for its failure. The largest Mt. Taranaki Plinian eruption columns reach ∼27 km high, dispersing 0.1 to 0.6 km3 falls throughout the North Island. Smaller explosive eruptions, or dome-growth and collapse episodes were more frequent. Block-and-ash flows reached up to 13 km from the vent, while the largest pumice pyroclastic density currents travelled >23 km. Mt. Taranaki last erupted in AD1790 and the present annual probability of eruption is 1–1.3%. [ABSTRACT FROM AUTHOR]

Taupō volcano (New Zealand) is distinguished as the source of Earth's youngest supereruption (∼25.5 ka), with Lake Taupō occupying the resulting caldera. Taupō has also produced eruptions of a wide variety of sizes, styles and associated landscape responses over a ∼350 kyr period. Early Taupō (>54 ka) is poorly demarcated, merging with Maroa to the north, and is represented by widely scattered, geochemically distinct, effusive domes and explosive eruption products from vents all around the modern lake. Taupō had two independent magmatic systems from 54–25.5 ka, one that led to the Oruanui event focussed beneath the area of the modern lake and a second, northeast of the lake that has remained active to the present. Following the Oruanui supereruption, the rebuilt modern hyperactive Taupō magmatic system is primarily focussed beneath the lake and has generated 25 rhyolitic eruptions since ∼12 ka. The young rhyolite magmas come from an evolving silicic magma reservoir, but vary widely in their eruptive sizes and destructive potential. In the modern era Taupō experiences unrest every decade or so, but uncertainties remain over the nature of the magma reservoir and the processes that drive unrest or eruptive activity that require new geophysical data and interpretations. [ABSTRACT FROM AUTHOR]

Given a module T over an F-algebra A , and a basis B for T , the amenability domain of B is the subalgebra of A consisting of all elements r ∈ A with row finite matrix representation [ l r ] B with respect to B. A basis B of T having amenability domain equal to A is said to be an amenable basis. When an amenable basis for T exists, T is said to be an amenable module. A basis having amenability domain F is said to be contrarian. We show that, under some mild additional hypotheses, amenable modules always have contrarian bases. The collection of amenability domains of bases of a module T is called the amenability profile of the module T. The profile is a measurement of the diversity of the bases of T and serves to sort them according to the extent of their amenability. We consider when profiles of amenable modules are minimal (consisting of only F and A) and when they are maximal (consisting of all the subalgebras of A); the former modules are said to lack discernment and the latter to be full rank. We provide an example of a graph magma algebra without discernment. We also show that F [ x ] does not lack discernment and that graph magma algebras are never full rank. As an alternative to full rank for graph magma algebras, we consider the largest domain of amenability feasible in that context and introduce Maximal Rank graph magma algebras; we show that such algebras indeed exist. [ABSTRACT FROM AUTHOR]

Spectacular reactions textures developed during the non-isochemical breakdown of orthopyroxene and spinel in peridotite mantle xenoliths in intraplate alkaline basalts from the Auckland Volcanic Field and the Dunedin Volcano in New Zealand, and Jeju Island in South Korea. Mantle orthopyroxene is replaced by symplectitic intergrowths of silica-rich glass and olivine (± clinopyroxene ± orthopyroxene) with individual minerals showing large diffusion gradients at their margins proximal to the host melt. The glasses are basaltic to trachytic and formed by incongruent melting of orthopyroxene and subsequent re-equilibration by diffusion and mixing during changing boundary conditions with the host magma. Although the glass composition is strongly dependent on the alkalinity of the host magma, the distance to the reacting contact and the respective phase assemblage that develops in the reaction zone (melt + ol ± clinopyroxene ± orthopyroxene), the most evolved melts converge at trachytic composition. Diffusion-driven Fe enrichment for mantle olivine indicates residence timescales within the host magma on the order of weeks to several months. [ABSTRACT FROM AUTHOR]

The intraplate rocks of the Dunedin Volcanic Group (DVG) in New Zealand's South Island erupted in two discrete areas between 25 and 21 Ma before becoming distributed over > 7,800 km2 until ∼9 Ma. Although most eruptive centres were of small volume and mainly vented alkaline basanite, the largest centre–the 16–11 Ma composite Dunedin Volcano–discharged basanite and basalt through to trachyte and phonolite. DVG components were mainly derived from mantle sources with 87Sr/86Sr = ∼0.7029, 143Nd/144Nd = ∼0.5129, 206Pb/204Pb = ∼20.0, 207Pb/204Pb = ∼15.65, 208Pb/204Pb = 39.5 and εHf = +3.5 to + 10.1 that extended to anomalously light δ26Mg (−0.47). Exceptions are some potassic basalts in NW of the field with elevated 207Pb/204Pb and more radiogenic Sr. The DVG Sr-Nd-Pb isotopes mostly overlap with metasomatised anhydrous mantle peridotite xenoliths but have less radiogenic Hf, meaning that equivalent anhydrous mantle rock-types cannot be the sole magma sources. Although there is debate regarding whether DVG was derived from the lithospheric or asthenospheric mantle, intermittent melting of a middle lithospheric mantle metasomatised by hydrous asthenosphere-derived melts could account for: (1) the widely distributed magmatism for ∼16 Myr during which time Otago lithosphere shifted NW ∼ 870 km over the asthenosphere; (2) the small chemical range of the least evolved magmas; (3) the Sr-Nd-Pb-Hf isotopic range; and (4) an absence of lower lithosphere mantle xenoliths. This process could account for other occurrences of isotopically restricted Zealandia alkaline intraplate volcanism. [ABSTRACT FROM AUTHOR]

The Alpine Dyke Swarm (ADS), intruding Haast Schist in the Southern Alps, New Zealand, comprises dykes, sills and diatremes of alkaline and ultramafic lamprophyres, phonolites and carbonatites. Intrusion peaked at ∼25 Ma during inception of dextral transtensional displacement on the Alpine Fault plate boundary. In a chamber beneath Haast River, magmas evolved by fractional crystallisation from primitive lamprophyres to phonolites, and then by liquid immiscibility to carbonatite magmas. Carbonatitic magmas coexisted with a highly sodic fluid that metasomatised adjacent quartzofeldspathic schist to aegirine-albite fenites. Carbonatites fractionated from Ca- to Fe-rich and, under late-stage, hydrothermal conditions, to Ba-Sr-REE–rich varieties. Some lamprophyres rose directly from a highly refractory spinel- or possibly garnet-spinel peridotite mantle that had been extensively metasomatised prior to the low-degree partial melting event and Cr-diopside series nodule entrainment. Al-augite series nodules give ages similar to host lamprophyres and are interpreted as deep-seated cognate cumulates. Compared to the broadly coeval basaltic-basanitic magmas of the Dunedin Volcanic Group (DVG) of East Otago, ADS magmas are enriched in volatiles, LILE, and HFSE (including REE). DVG magmas were derived from a less metasomatised mantle source, and, although undergoing extensive fractionation, failed to achieve the extreme alkali enrichment necessary for silicate melt-carbonatite immiscibility. [ABSTRACT FROM AUTHOR]

Mesozoic A-type granites are widely distributed in the Lower Yangtze River Belt (LYRB) in China, but their petrogenesis and geodynamic settings are unresolved. Here, we describe geochronological and geochemical study of granites from the Zongyang area of the LYRB. Zircon LA-ICPMS U-Pb dating indicates the granites were emplaced at ca. 127 Ma. They have geochemical characteristics similar to those of A-type granites, with high total-alkali (10.5–10.7 wt.%), HFSEs (Zr + Nb + Ce + Y = 890–1011 ppm), high Ga/Al ratios (10,000 × Ga/Al = 3.19–3.25), and high whole-rock zircon saturation temperatures (850°C–900°C). In discrimination diagrams, samples plot in the A1-type granite field but close to the A1–A2 boundary. A representative whole-rock sample yielded an ISr ratio of 0.7066 and an εNd(t) value of – 5.3, with zircon εHf(t) and δ18O values of – 0.2 to – 4.3 and 5.95‰–6.79‰, respectively, all higher than those of depleted mantle, indicating the enriched nature of source materials. Apatites in the granite display mantle-origin characteristics. Incompatible element ratios (Y/Nb, Y/Ta, Nb/U and Ce/Pb) also support the enriched mantle source, and suggest that the source had experienced metasomatism, or the existence of crustal input during magmatic processes. Significant depletions in Ba, Sr, P, Ti, and Eu in the granites indicate fractional crystallization of feldspar and some accessory minerals. We conclude that the Zongyang granite were formed through fractional crystallization of oceanic island basalt (OIB)-like basic magmas derived from the lithospheric mantle. They are classified as A1 but their borderline A2 nature is most likely due to metasomatism by slab-derived fluids or melts, possibly involving crustal materials. Our results, together with those of previous studies, indicate that LYRB A-type granites, are the products of partial melting of the mantle or lower continental crust in an extensional setting, caused by slab rollback during the subduction of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]