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Vast and geochemically diverse volcanic rocks from the western Alborz Magmatic Assemblage (AMA) represent the back-arc of the central Iran Neotethyan arc (Urumieh–Dokhtar Magmatic Assemblage; UDMA). Volcanic rocks of the west AMA record valuable information on the timing, source region(s) and geodynamic setting of magmatism. Over 30 days of field study and sampling, investigation of 170 thin sections, 30 whole-rock geochemical analyses, 13 whole-rock Sr–Nd isotopic ratios and U–Pb age dating of zircon separates from 7 samples furnished the present study data. Eocene (38.5 Ma) OIB-type volcanic rocks from South Kaleybar indicate an anorogenic (extensional) setting. This lithospheric-scale extensional event induced influx of asthenospheric mantle into the sub-arc wedge, of which the partial melts differentiated to produce OIB-type melts. The OIB-type melts incorporated some inherited zircons in their ascent through the Cadomian crust. A continued extensional regime led to asthenospheric upwelling and produced mafic melts that produced 27.5-Ma-old subalkaline series volcanics. The LILE-depleted signature of the South Kaleybar subalkaline volcanic rocks implies that their mantle source region experienced previous partial melting event(s), probably during OIB-type magmatism in the Eocene. Alkaline volcanism (24.4 Ma) and concurrent high-silica adakitic volcanism (24.3 Ma–23.4 Ma) followed subalkaline magmatism. The alkaline rock signature in the study area range from 'Nb–Ta depleted' to 'plume-type'. This is consistent with lithosphere–asthenosphere interaction in an arc-related setting. Simultaneous partial melts of delaminated lower crustal rocks reacted with the asthenosphere and produced adakitic melts. Asthenospheric, lithospheric and crustal contribution to the magmatism in South Kaleybar express the back-arc signature of magmatism in Eocene to Late Oligocene times. [ABSTRACT FROM AUTHOR]

Continental basaltic volcanism in the Arabian Shield of Saudi Arabia has distinctive mineralogical and geochemical features important for understanding the composition of its mantle source and melting conditions. The studied Cenozoic basaltic rocks (19.3–15 Ma) occur at Jabal Al Gharib and Jabal Al Ghuraybayn areas within the Al Qasr quadrangle and southwest of Hail City in Saudi Arabia. They show similar chondrite-normalized REE patterns, suggesting that they were derived from a common mantle source. Their OIB-like features, silica undersaturated nature, and incompatible trace element ratios all reveal an asthenospheric mantle source and argue against crustal contamination process, subduction contribution, and interaction with a lithospheric mantle. Moreover, the elevated compatible trace element concentrations of Ni, Cr, and Co and the low and relatively narrow range of FeOtotal/MgO ratios argue for their nearly primitive nature and indicate that the role of crystal fractionation processes was minor during the evolution of the studied rocks. The estimated temperatures indicate that the sequence of crystallization likely began with olivine at 1,378–1,475°C, then clinopyroxene at 1,137–1,214°C, and soon after followed by plagioclase at 1,096–1,108°C. Plagioclase geo-hygrometers reveal 0.63–1.41 wt% water contents, suggesting crystallization under hydrous conditions. The basalts have geochemical features such as high (K2O + Na2O)/TiO2, Zr/Hf, and Nb/Ta ratios and negative K anomalies which suggest a carbonated peridotite mantle source. Their bulk-rock compositions are consistent with

In this study, zircon grains are applied for U–Pb dating, Hf isotopes and trace elements to reveal the origin of magmatism and tectonic evolution of Late Paleozoic rocks of the Indian plate, Northern Pakistan. Most of the zircons are characterized by oscillatory zoning, depletion of light rare earth elements (LREE) and enrichment of heavy rare earth elements (HREE) with Ce and Eu anomalies. The yielded ages for these rocks are 256 ± 1.9 Ma and are plotted in the zones defined for the continental setting with few deviated toward the mid-oceanic ridge and the oceanic arc setting. Deviated zircons are recognized as inherited zircons by displaying a high concentration of normalized primitive La and Pr values, while others are plotted in the continental zones. Rare earth elements (REE) and trace elements including Th, Hf, U, Nb, Sc and Ti discriminate Swat orthogneisses into the within plate setting and the inherited zircons are plotted in the orogenic or the arc-related setting. The LREE discriminated these zircons into a magmatic zone with inherited zircons deviated toward the hydrothermal zone. The temperature calculated for these rocks based on the Ti content in zircon ranges from 679 to 942°C. The εHf(t) ranging from −11.1 to +1.4 reveals that the origin is the continental crust with the minute input of the juvenile mantle.

This paper discusses the petrological and geochemical characteristics of the acid plutonic rocks (mainly granites of different colors) exposed in Khanak and Devsar areas of Neoproterozoic Malani Igneous Suite (MIS) to understand their magmatic evolution processes, petrogenetic history and tectonic regimes. Petrographically, granites of both areas show porphyritic, hypidiomorphic, granophyric, perthitic and micro-granophyric textures. Geochemically, these acidic rocks having peraluminous nature are enriched in SiO2, Na2O + K2O, Fe/Mg, Rb, Zr, Y, Th, U, REE and depleted in MgO, CaO, Sr, P, Ti, Ni, Cr, V & Eu abundances, which have affinity with A-type granites in extensional environment. The enrichment of trace elements and negative anomalies of Sr, Eu, P & Eu in the multi-element spider diagrams suggest that the emplacement of these granites were controlled by fractional crystallization and crustal contamination of protolith magma. Elemental geochemistry also attests that they are of rare-metal bearing with high heat production (HHP) nature and represent a genetically related post-collisional A2-type granitic intrusions. Petrogenetic modeling (batch melt related) suggests that the early phase (grey and grayish green colored granites) might have been generated from a gabbroic source by partial melting (5%) leaving a residue with 25% alkali feldspar, 20% quartz, 35% plagioclase, 10% biotite, 8% hornblende, 1% orthopyroxene and 1% clinopyroxene whereas late phase (pink colored granites) might have been generated from a metavolcanic source by partial melting of 2% leaving a residue with 30% alkali feldspar, 15% quartz, 45% plagioclase, 2% biotite, 2% hornblende, 3% orthopyroxene and 3% clinopyroxene. Hence, the petrology and geochemistry of these acid plutonic rocks are consistent with their formation in a plume related rift-magmatic tectonic setting and exhibit complex post magmatic chemical variations. [ABSTRACT FROM AUTHOR]

This paper reports new mineral and whole-rock geochemical data on the acid volcano-plutonic rocks of the Tusham Ring Complex (TRC) from the Neoproterozoic Malani Igneous Suite (MIS), northwestern Peninsular India and discusses their magmatic evolution, tectonic implication, and geodynamic history. Geochemically, the investigated rocks have the characteristics of hypersolvus, high-K calc-alkaline to shoshonitic, peraluminous and A-type granitoids and they are enriched in SiO2, (Na2O + K2O), Fe/ Mg, Ga/Al, Th, U, REE (except Eu), LILE + HFSE, halogens (F and Cl) and depleted in CaO, MgO, Sr, Cr, Ni, P, Ti and Eu abundances. They also show high heat production (HHP) affinity and high mineralization potential. The high abundances of fluorine (0.80–7.11 wt %) and chlorine (0.44–1.56 wt %) in biotite and the geochemistry of the studied rock types indicate that the acid volcanics and granite massifs of TRC were derived from a halogen-enriched magmatic source under low degree partial melting of crustal protolith. The field, petrography, mineral chemistry, whole-rock geochemistry of the rocks under study, in combination with their tectonic and petrogenetic signatures have proposed that the rift-related Neoproterozoic magmatism of MIS has close linkage with geodynamic evolution of Nagarparkar, Seychelles and Madagascar A-type granitoids during Rodinia breakup. [ABSTRACT FROM AUTHOR]

The present study is carried out to probe geodynamic evolution and tectonic history of A-type granitoids from the Riwasa and Nigana areas in the Tusham Ring Complex (TRC), western Peninsular India on the basis of petrological and geochemical aspects. The investigated rocks have the characteristics of hypersolvus, calc-alkaline, peraluminous and A-type granitoids. They are enriched in SiO2, Na2O+K2O, Fe/Mg, Th, U, REE (except Eu), LILE+HFSE, elevated in Fe/Mg, Ga/Al, Th/U, A/CNK ratios, and depleted in CaO, MgO, Sr, Cr, Ni, P, and Ti, and having Eu abundances. They also show high heat production (HHP) affinity and high mineralization potential. Elemental geochemistry in conjunction with mineralogical variants attested that they were formed by limited fractional crystallization of a parental magma derived from partial melting of crustal protolith accreted during the Neoproterozoic magmatic event. Physicochemical features i.e. F and Cl-rich biotite, pegmatite rim, substantial model content of albite, high mineralized veins and altered mineralogy indicate rock-fluid interactions which are caused by magmatic origin or secondary metasomatic alteration superimposed on the host rock. The magmatism occurred in the TRC is interpreted to represent the Malani Igneous Suite (MIS) and their linkage with Rodinia Supercontinent and Pan-African thermal event. [ABSTRACT FROM AUTHOR]

The occurrence of lamprophyre dikes is being reported first time in the Gebel Anweiyib area, south Eastern Desert, Egypt. The investigation of the ultramafic lamprophyre (damtjernite) dikes intruded into the crustal younger granites and metasediments based on their spectral characteristics, mineralogical and geochemical compositions. Three multispectral sensors of Landsat-8, ASTER and S2 have been used to detect and characterize the lithologic units and the lamprophyre dikes. The reflectance and absorption signatures of the granitic rocks and lamprophyre dikes were the basis for detecting them from the remotely sensed data using the application of advanced image processing algorithms including FCC, BR, PCA, MNF, and DS. Geochemical studies inferred that the damtjernite dikes are under-saturated with SiO 2 (<38.89 wt%), alkaline with total alkalis (avg. 4 wt%), metaluminous with A/CNK (0.22–0.51), and ultramafic with MgO (13.88–19.23 wt%). They exhibit unique geochemical characteristics of mantle (with high MgO, Ni, Cr, and Mg#) coupled with crustal (high Sr, Ba, Zr, Ga and REEs) sources, similar to global ultramafic lamprophyres. High TiO 2 and highly fractionated REEs with low HREEs (avg. 23 ppm) relative to LREEs (avg. 354 ppm) contents, yielding residual garnet in melts. Low partial melting of primitive garnet lherzolite can account the obtained REEs in the ultramafic lamprophyres. These features signify their derivation from a deeper enriched asthenospheric (plume-type) magma like OIB, which is attested by the high Nb/La (avg. 1.32), Nb/U (avg. 102), La/Yb (avg. 43), and low Y/Nb < 0.52, Rb/Sr < 1, Rb/Ba (<0.14), and Sr/Ba (<0.9), suggesting their derivation from a mantle-derived source rather than crustal rocks. High concentrations of TiO 2 and Fe 2 O 3 in the ultramafic lamprophyres, reflecting their formation from a fertile peridotite by mantle plume-derived melts with K-residual phlogopite rather than amphibole as obtained by low Ba/Rb and high Rb/Sr ratios. The Anweiyib lamprophyres are anorogenic and confined to being derived from rifting regions, and their magma is not contaminated with crustal sources during emplacement. • Damtjernite)ultramafic (lamprophyre dikes intruded into the younger granites rocks. • Lamprophyres exhibit unique geochemical characteristics of coupled with crustal sources. • Lamprophyres are derived from a deeper enriched asthenospheric (plume-type) magma like OIB. • These lamprophyres are anorogenic and confined to emplaced from rifting regions. [ABSTRACT FROM AUTHOR]

The southern Sinai Peninsula, underlain by the northernmost extension of the Arabian-Nubian Shield, exposes post-collisional calc-alkaline and alkaline granites that represent the youngest phase of late Neoproterozoic igneous activity. We report a petrographic, mineralogical and geochemical investigation of post-collisional plutons of alkaline and, in some cases, peralkaline granite. These granites intrude metamorphosed country rocks as well as syn- and post-collisional calc-alkaline granitoids. The alkaline and peralkaline granites of the southern tip of Sinai divide into three subgroups: syenogranite, alkali feldspar granite and riebeckite granite. The rocks of these subgroups essentially consist of alkali feldspar and quartz with variable amounts of plagioclase and mafic minerals. The syenogranite and alkali feldspar granite contain small amounts of calcic amphibole and biotite, often less than 3%, while the riebeckite granite is distinguished by sodic amphibole (5-10%). These plutons have geochemical signatures typical of post-collisional A-type granites and were most likely emplaced during a transition between orogenic and anorogenic settings. The parental mafic magma may be linked to lithospheric delamination and upwelling of asthenospheric mantle material. Differentiation of the underplated basaltic magma with contributions from the juvenile crust eventually yielded the post-collisional alkaline granites. Petrogenetic modelling of the studied granitic suite shows that pure fractional crystallization cannot quantitatively explain chemical variations with the observed suite, with both major oxides and several trace elements displaying trends opposite to those required by the equilibrium phase assemblage. Instead, we show that compositional variation from syenogranite through alkali feldspar granite to riebeckite granite is dominated by mixing between a low-SiO2 liquid as primitive or more primitive than the lowest-SiO2 syenogranite and an evolved, high-SiO2 liquid that might be a high-degree partial melt of lower crust. [ABSTRACT FROM AUTHOR]

Neoproterozoic felsic magmatic suites are important proxies to investigate the breakup history of the Rodinia supercontinent which likely coincided with the emplacement of voluminous Silicic Large Igneous Provinces (SLIPs). Here we report new zircon U Pb ages with comprehensive whole-rock and mineral chemistry data on the felsic volcano-plutonic rocks from the Tusham Ring Complex (TRC) that forms part of the anorogenic Malani Igneous Suite (MIS) (∼780–750 Ma) in NW India. The plutonic rocks (granites) and contemporaneous volcanic rocks (rhyolites) show affinity to A-type granitoids, hypersolvus to subsolvus, and metaluminous to peraluminous. The granitoids investigated in this study are enriched in SiO 2 , Na 2 O + K 2 O, Fe/Mg, Ga/Al, U, Th, REE (except Eu), and depleted in MgO, CaO, Cr, Ni, P, Ti, Sr, and Eu contents. The zircon U Pb dating for felsic volcanic rocks (four rhyolite samples) yielded Neoproterozoic ages ranging from 827 to 764 Ma whereas zircon in five felsic plutonic rocks (granite) shows ages ranging from 830 to 787 Ma, indicating coeval nature of the intrusive and extrusive rocks. The zircon grains have mostly negative εHf(t) values up to −3.62 and yield crustal Hf model ages from 1.6 Ga to 1.9 Ga, suggesting that the magmatic event involved melting of a Paleoproterozoic source. Based on geochemical features, we propose that the partial melting of crustal protoliths, fractional crystallization, and crustal contamination played a significant role in the magmatic evolution of these rocks. We also infer that the felsic anorogenic magmatism in the TRC occurred in an extensional tectonic regime, possibly associated with a mantle plume event. Our results, in conjunction with previous studies, support the model of anorogenic magmatism linked with the disruption of the Neoproterozoic Rodinia supercontinent. [Display omitted] • Anorogenic A-type acid volcano-plutonic rocks of TRC were emplaced at 830–764 Ma. • Partial melting, fractional crystallization, crustal contamination played a role. • Magmatism linked with disruption of Neoproterozoic Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

The East-Ujimqin complex, located north of the Erenhot–Hegenshan fault, North China, is composed of mafic–ultramafic and granitic rocks including peridotite, gabbro, alkali granite, and syenite. We investigated the tectonic setting, age, and anorogenic characteristics of the Xing’an–Mongolian Orogenic Belt (XMOB) through field investigation and microscopic and geochemical analyses of samples from the East-Ujimqin complex and LA-MC-ICP-MS zircon U–Pb dating of gabbro and alkali granite. Petrographic and geochemical studies of the complex indicate that this multiphase plutonic suite developed through a combination of fractional crystallization, assimilation processes, and magma mixing. The mafic–ultramafic rocks are alkaline and have within-plate geochemical characteristics, indicating anorogenic magmatism in an extensional setting and derivation from a mantle source. The mafic–ultramafic magmas triggered partial melting of the crust and generated the granitic rocks. The granitic rocks are alkali and metaluminous and have high Fe/(Fe + Mg) characteristics, all of which are common features of within-plate plutons. Zircon U–Pb geochronological dating of two samples of gabbro and alkali granite yielded ages of 280.8 ± 1.5 and 276.4 ± 0.7 Ma, placing them within the Early Permian. The zircon Hf isotopic data give inhomogeneous ε Hf ( t ) values of 8.2–14.7 for gabbroic zircons and extraordinary high ε Hf ( t ) values (8.9–12.5) for the alkali granite in magmatic zircons. Thus, we consider the East-Ujimqin mafic–ultramafic and granitic rocks to have been formed in an extensional tectonic setting caused by asthenospheric upwelling and lithospheric thinning. The sources of mafic–ultramafic and granitic rocks could be depleted garnet lherzolite mantle and juvenile continental lower crust, respectively. All the above indicate that an anorogenic magma event may have occurred in part of the XMOB during 280–276 Ma. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Paleoproterozoic Kimozero kimberlitic rock association is described. [•] Trace element composition of the Kimozero kimberlitic rock association is close to that of micaceous kimberlite/olivine lamproite. [•] U–Pb zircon data indicates an emplacement age of 1.92Ga. [•] The emplacement of the kimberlitic rock association is likely related to 2.0–1.9Ga continental break-up event. [ABSTRACT FROM AUTHOR]

Abstract: Lamproites are among the most enigmatic mantle generated melts, and are typically abundant in phlogopite. We investigated the major and trace element chemistry of phlogopite crystals from Mediterranean lamproite occurrences in Spain, Serbia and Turkey. The most primitive lamproite samples were selected in order to evaluate the generation of the different phlogopite populations in their distinct mantle setting(s). Phlogopite hosted in Mediterranean lamproites can be grouped into different compositional arrays on the basis of their major element chemistry using Al2O3, FeOT and TiO2 concentrations. Contents of Cr, F and presumably Ti allow discrimination of the macrocrysts into phlogopite phenocrysts, which are liquidus and near-liquidus phases, and mantle xenocrysts. Further distinction among different populations of mantle-derived phlogopite can be achieved, considering trace element and isotopic ratios. The latter also distinguish between crustal and asthenospheric imprints on the source of the lamproitic parental melt. [Copyright &y& Elsevier]

Abstract: The Katherina Volcanics of Gabal Ma’ain in the Sinai comprise an Ediacaran (580–590Ma) approximately 450m thick succession dominated by porphyritic rhyolite lava flows with subordinate related pyroclastics. These volcanics unconformably overlie the calc-alkaline Younger Granites (≥590Ma) and are intruded by alkaline granitoids (578±8Ma). The rhyolites have a potassic alkaline affinity and peraluminous to slightly metaluminous character. They exhibit many of the classic features of A-type magmas, including enrichment of incompatible elements, such as Zr, Nb, Y, Ga, Zn and Ce and total REE, as well as high FeO*/(FeO*+MgO) and 10,000*Ga/Al2O3 ratios. The A-type rhyolites have LREE-enriched patterns with pronounced negative Eu anomalies that are comparable with typical REE profiles for “hot-dry-reduced rhyolites”. Saturation thermometry has yielded zircon and apatite crystallization temperatures ranging between 913 and 925°C and 669 and 931°C, respectively. The investigated trace element patterns indicate that the Katherina A-type rhyolites were very likely to have evolved through simple fractional crystallization of a parental magma derived from an enriched (most probably asthenospheric) mantle source, supplemented by a crustal component inherited from pre-collision subduction events, or a ‘recycled component’ in the source. Katherina A-type rhyolites were likely erupted in a within-plate setting. The eruption of these rhyolites marks the onset of the anorogenic period during which the rigid massif (Arabian–Nubian Shield) was subjected to post-collisional tensional stresses and intra-plate rifting. [Copyright &y& Elsevier]

Abstract: We present field relationships, major and trace element geochemistry and U–Pb SHRIMP and ID-TIMS geochronology of the A-type Ordovician Quintas pluton located in the Ceará Central Domain of the Borborema Province, in northeastern Brazil. This pluton presents a concentric geometry and is composed mainly of syenogranite, monzogranite, quartz syenite to quartz monzodiorite, monzogabbro and diorite. Its geochemical characteristics [SiO2 (52–70%), Na2O/K2O (1.55–0.65), Fe2O3/MgO (2.2–7.3), metaluminous to sligthly alkaline affinity, post-collisional type in (Y + Nb) × Rb diagram, and A-type affinity (Ga > 22 ppm, Nb > 20 ppm, Zn > 60 ppm), REE fractioned pattern with negative Eu anomaly] are coherent with post-collisional A2-type granitoids. However, the emplacement of this pluton is to some extent temporally associated with the deposition of the first strata of the Parnaíba intracratonic basin, attesting also to a purely anorogenic character (A1-type granitoid). The emplacement of this pluton is preceded by one of the largest known orogenesis of the planet (Neoproterozoic Pan-African/Brasiliano) and, if it is classified as an A2-type granitoid, it provides interesting constraints about how long can last A2-type magmatic activity after a major collisional episode, arguably triggered by disturbance of the underlying mantle, a topic extensively debated in the geoscience community. [Copyright &y& Elsevier]

Abstract: A new lamproite occurrence of inferred Carboniferous age intruded into an extensive, more than 5km long rectilinear fracture zone in a granite of the West Troms Basement Complex, North Norway. This 30cm wide dyke, which shows well developed chilled margins, is characterized by up to 3mm long phenocrysts of phlogopite in a fine-grained gray matrix of K-feldspar and K-magnesioarfvedsonite with minor amounts of apatite, Ba-titanates (baotite) and rutile. Based on its mineralogy, whole rock chemistry (e.g., SiO2 =54.4–57.3wt.%, K/Na=2.02–7.03, K/Al=0.86–1.22, Mg#=76–84 and Kagp =1.0–1.7), and specific mineral compositions (e.g. tetrahedral coordination of Fe3+ in phlogopite, high Fe, but negligible Na in K-feldspar, and high Ti in K-magnesioarfvedsonite and phlogopite) the rock can be classified as a high-Si phlogopite lamproite. Concentrations and element ratios of a number of trace elements (e.g. high LILE and HFSE, except of Nb and Ta, high La/Ybn and low Th/Nb) in addition to isotope data (moderately radiogenic 87Sr/86Sr and extremely non-radiogenic 143Nd/144Nd; εNd(T) varies from −19.9 to −22.4) indicate an anorogenic, i. e., within-plate setting for the Kvaløya lamproite, similar to the anorogenic types of lamproite from Leucite Hills (Wyoming) and Smoky Butte (Montana). The Kvaløya lamproite shows high Nb/Ta and simultaneous high Zr, suggesting a multistage enrichment history of its mantle source. It is suggested that in addition to an ancient stage of enrichment (2.1–2.3Ga, based on Nd model ages), parts of the mantle enrichment possibly resulted from the involvement of subducted materials during metasomatism of the mantle during the Caledonian Orogeny. [Copyright &y& Elsevier]

High to medium content of radioactive elements (U, Th, K) together heat generation of anorogenic, A-type felsic to intermediate volcano-plutonic rocks (granite, rhyolite and trachyte) of Dhiran Area, Malani Igneous Suite, western India has been reported. These volcano-plutonic suits of rocks are classified as high to medium Heat Production (HP). Leucocratic granite shows higher Heat Production (4.84-8.75 μWm-3) and total Heat Generation Unit (11.52-20.84 HGU) than pink granite (2.09-2.94 μWm-3 HP; 4.98-7.07 HGU) and rhyolites (2.87-6.63μWm-3 HP; 6.83-15.80 HGU). Leucocratic granites, pink granites and rhyolites of the Dhiran area shows higher average value of total Heat Generation Unit (16.51 HGU, 5.79 HGU and 9.33 HGU) than the average value of 3.8 HGU for the continental crust. The high Heat Generation Unit values (4.98-20.84) of the volcano-plutonic rocks of the Dhiran indicate 'hot crust' category and a possible linear relationship between the surface heat flow and crustal heat generation in the Malani Igneous Suite. [ABSTRACT FROM AUTHOR]

Abstract: A magnetic fabric study was performed on the Redenção pluton in an attempt to understand its emplacement history. The Redenção pluton is part of the 1.88Ga, anorogenic, A-type Jamon suite that intruded 2.97–2.86Ga-old Archean granitoids of the Rio Maria Granite-Greenstone Terrane in the eastern Amazonian craton (northern Brazil). Previous gravity survey indicates that the pluton is a 6km-thick, tabular intrusion. It is characterized by a concentric distribution of facies, with rings of seriated and porphyritic granite that cut across the main facies of even-grained monzogranites. The whole set is intruded by leucogranites that occupy the center of the pluton. Petrographic examination, magnetic susceptibilities, coercivity-spectra and thermomagnetic curves indicate that the magnetic fabric is primarily carried by coarse-grained multidomain magnetite. This is reinforced by the coincidence of magnetic susceptibility and remanence anisotropy principal axes. The absence of solid-state deformation features and the low anisotropy degrees indicate that the magnetic fabric is magmatic in origin. The magnetic fabric displays a systematic pattern, with all facies, including the rings of porphyritic granite, being characterized by concentric, gently dipping foliations associated with gently plunging lineations. Only the central leucogranitic facies shows a slightly discordant pattern with steeply dipping fabrics at its northeastern sector. An emplacement model by vertical stacking of successive magma batches is proposed for the construction of the Redenção pluton, which reconciles the tabular shape of the intrusion, the petrographic and geochemical zoning, and the magnetic fabric pattern. Initially, two magma batches were emplaced as sills. First the even-grained monzogranite, then the seriated and porphyritic granites, which formed by mingling of a leucogranitic melt with the host biotite-monzogranitic magma as attested by geochemical data and field evidence. The final shape of the pluton was acquired after the intrusion and inflation of the central leucogranite giving raise to the concentric pattern of facies in map view. [Copyright &y& Elsevier]

Abstract: Age populations of detrital zircons in sand or sandstone preserve a reliable record of the ages of granitoid source rocks from which most of the zircon grains were ultimately derived, and this provenance signal can be used to infer sediment sources from independent knowledge of the areal distribution of granitoids of different ages provided allowance is made for sedimentary recycling of durable zircon sand grains. A compilation of 1386 whole-rock Zr analyses (ppm) from 72 North American suites of granitoid rock implies that the mean zircon fertility of different types and ages of granitoids ranges over nearly half an order of magnitude. Although Zr enters the lattices of some other igneous minerals sparingly, zircon contents of granitic rocks are inferred to vary with Zr contents. Subduction-related granitoid suites of varying ages (Archean, Paleoproterozoic, accreted peri-Gondwanan Neoproterozoic, Appalachian Paleozoic, Cordilleran Mesozoic) have a mean Zr content of 150 ppm and are assigned an arbitrary zircon fertility factor (ZFF) of 1.0. Mesoproterozoic Grenville granitoid suites associated with collisional orogeny have a mean Zr content of ~520 ppm (ZFF~3.5). Anorogenic plutons of a transcontinental Mesoproterozoic igneous belt and of Appalachian pre-Iapetan Neoproterozoic and pre-Atlantic Mesozoic rift belts have a mean Zr content of ~375 ppm (ZFF~2.5). Variations in the content of other high field strength elements (HFSE) parallel variations in Zr content. The differential zircon fertility of granitoid basement rocks should be taken into account for estimates of relative contributions of zircon populations from multiple bedrock sources to sediment of mixed provenance, and variations in ZFF suggest that subduction-related, collision-related, and anorogenic granitoid assemblages reflect different modes of crust–mantle evolution. [Copyright &y& Elsevier]

Abstract: The 1.88Ga, anorogenic, A-type Redenção and Bannach granites, representative of the Jamon suite and associated dikes, are intrusive in Archean granitoids of the Rio Maria Granite–Greenstone Terrane in the eastern Amazonian Craton in northern Brazil. Petrographic and geochemical aspects associated with magnetic susceptibility and gamma-ray spectrometry data show that the Redenção and the northern part of Bannach plutons are normally zoned. They were formed by two magmatic pulses: (1) a first magma pulse was fractionated in situ after emplacement at shallow crustal level, generating a series of coarse, even-grained monzogranites with variable modal proportions of biotite and hornblende; and (2) a second, slightly younger magma pulse, located to the center of the plutons, was composed of a more evolved liquid from which even-grained leucogranites derived. Gravity modeling indicates that the Redenção and Bannach plutons are sheeted-like composite intrusions, approximately 6 and 2km thick, respectively. These plutons follow the general power law for laccolith dimension and are similar in this respect to classical rapakivi granite plutons. Gravity data suggest that the growth of the northern part of the Bannach pluton resulted from the amalgamation of smaller sheeted-like plutons that intruded in sequence from northwest to southeast. The Jamon suite plutons were emplaced in an extensional tectonic setting, and the stress was oriented approximately NNE–SSW to ENE–WSW, as indicated by the occurrence of diabase and granite porphyry dyke swarms, orientated WNW–ESE to NNW–SSE and coeval with the Jamon suite. The 1.88Ga A-type granite plutons and stocks of Carajás are disposed along a belt that follows the general trend defined by the dikes. The inferred tabular geometry of the studied plutons and the high contrast of viscosity between the granites and their Archean country rocks can be explained by magma transport via dikes. [Copyright &y& Elsevier]

Abstract: Eruptions of topaz rhyolites are a distinctive part of the late Cenozoic magmatic history of western North America. As many as 30 different eruptive centers have been identified in the western United States that range in age from 50 to 0.06 Ma. These rhyolite lavas are characteristically enriched in fluorine (0.2 to 2 wt.% in glass) and lithophile trace elements, such as Be, Li, Rb, Cs, Ga, Y, Nb, and Ta. REE patterns are typically flat with large negative Eu anomalies; negative Nb–Ta anomalies are small or nonexistent; and F/Cl ratios in glasses are high (>3). These features, together with high Fe/Mg ratios and usually low fO2, set them apart from subduction-related (I-type) silicic rocks. The rhyolites are metaluminous to only slightly peraluminous, lack indicator minerals of strongly peraluminous magmas, and have low P and B contents; these features set them apart from S-type silicic magmas. Instead, topaz rhyolites have the major and trace element, mineralogic, and isotopic characteristics of aluminous A-type or within-plate granites. Topaz rhyolites were formed during regional extension, lithospheric thinning, and high heat flow. Topaz rhyolites of the western United States crystallized under subsolvus conditions, and have quartz, sanidine, and Na-plagioclase as the principal phenocrysts. Fluorite is a common magmatic accessory, but magmatic topaz occurs only in a few complexes; both are mineralogical indicators of F-enrichment. Many also crystallized at relatively low fO2 (near QFM) and contain mafic silicate minerals with high Fe/(Fe+Mg) ratios. Some crystallized at higher oxygen fugacities and are dominated by magnetite and have titanite as an accessory mineral. Post-eruption vapor-phase minerals include topaz, garnet, red Fe–Mn-rich beryl, bixbyite, pseudobrookite, and hematite. They are genetically related to deposits of Be, Mo, F, U, and Sn. Topaz rhyolites erupted contemporaneously with a variety of other igneous rocks, but most typically they form bimodal associations with basalt or basaltic andesite and are unrelated to large collapse calderas. In their composition and mineralogy, topaz rhyolites are similar to the evolved members of rapakivi granite complexes, especially those of Proterozoic age in southern Finland. This suggests similarity in origin and lessons learned from these rocks may help us better understand the origins of their more ancient counterparts. For example, all topaz rhyolites in western North America seem to be intrinsically related to extension following a regional period of subduction-related volcanism. Cratonized Precambrian crust is found beneath almost all of them as well. Trace element models, Sr–Nd isotopic data, and geologic associations indicate that topaz rhyolites probably form by fractional crystallization of silicic magma which originated by small degrees of melting of hybridized continental crust containing a significant juvenile mantle component not derived from a subduction zone (i.e., intrusions of within-plate mafic magma). The Sr and Nd isotopic compositions of the topaz rhyolites lie between the fields of contemporaneous mafic magmas and older calc-alkaline dacites and rhyolites. Intraplate mafic magmas and their derivatives appear to have lodged in the crust and were then re-melted by subsequent injections of mafic magma. In turn, the mafic mantle-derived magma probably formed as a result of decompression related to lithospheric extension or to convective-flow driven by the foundering of a subducting lithospheric plate. Although significant uncertainty remains, we suggest that topaz rhyolites (and by extension rapakivi granites) are probably not simply melts of mid-crustal granodiorites, nor are they derived solely from felsic crust that was previously dehydrated or from which melt had been extracted as proposed in earlier papers. [Copyright &y& Elsevier]

Abstract: Although A-type granites have long been recognized as a distinct group of granites, the term A-type was coined first less than thirty years ago. A-type suites occur in geodynamic contexts ranging from within-plate settings to plate boundaries, locations and times of emplacement are not random. Rare in the lower crust, as some charnockite suites, they are fairly common at shallower depths, especially at the subvolcanic level where they form ring complexes rooting caldera volcanoes. Characteristic features include hypersolvus to transsolvus to subsolvus alkali feldspar textures, iron-rich mafic mineralogy, bulk-rock compositions yielding ferroan, alkali-calcic to alkaline affinities, high LILE+HFSE abundances, and pronounced anomalies due to high degrees of mineral fractionation. Isotopic features evidence sources containing a large mantle input. Experimental data show that A-type magmas contain dissolved OH–F-bearing fluids, crystallised under reduced and oxidized conditions, and yield high-temperature liquidus, favouring early crystallisation of anhydrous iron minerals, such as fayalite. Though many petrogenetic models imply solely crustal derivation, no convincing A-type liquids were produced experimentally from crustal materials, nor have any leucosomes of A-type composition been detected within migmatitic terranes. As it occurs in association with mafic igneous rocks in continents as well as on the ocean floor, A-type granite is likely to come from mantle-derived transitional to alkaline mafic to intermediate magmas. Rare felsic materials found in the meteoritic and lunar record yield dominantly A-type features. Contrary to the more common types of granite, A-type granite is, therefore, not typical of Earth and was produced in planetary environments differing from those prevailing on Earth. [Copyright &y& Elsevier]

Abstract: Emplacement of 1.6 to 1.3 Ga Mesoproterozoic plutons in Baltica and Laurentia formed an immense belt of A-type granite batholiths that include (1) low-fO2, ilmenite-series granite intrusions from the Baltic region to Wyoming, (2) high-fO2, magnetite-series granite intrusions of the central to southwestern U.S., and (3) peraluminous, two-mica granite intrusions from Colorado to central Arizona. These mineralogic divisions are mirrored by substantial elemental and oxygen isotopic differences. The ilmenite-series granites, which often contain classic rapakivi textures, have the highest Fe/Mg ratios and are highest in LIL element enrichment. They also have the lowest whole-rock δ18O values at 5.7‰ to 7.7‰. The magnetite-series granites are less potassic, less LILE-enriched, and have higher whole-rock δ18O values, ranging from 7.6‰ to 10.8‰. Although they retain A-type characteristics, the peraluminous granites are the least LILE-enriched and have the lowest Fe/Mg ratios. They also have the highest whole-rock δ18O values ranging from 8.8‰ to 12.0‰. Feldspar, where strongly reddened, can exhibit elevated δ18O values, which is interpreted to indicate subsolidus exchange with surface-derived aqueous fluids. Quartz δ18O values are interpreted to generally retain their magmatic values. The transcontinental mineralogic, chemical, and oxygen isotopic variations are interpreted as indicative of broad changes in the composition of a lower crustal source, which is compatible with a reduced mantle-derived crustal source for the ilmenite-series granites and a more oxidized crustal source for the others, including a metasedimentary component in the source for the two-mica granite subprovince. Widespread thermal metamorphism at ∼1.4 Ga is present throughout much of the magmatic province and is viewed as a consequence of this immense event. Compressional deformation associated with several western 1.4 Ga Laurentia granite batholiths, alternatively interpreted as the distal expressions of a presumed 1.4 Ga orogeny, have at least in part been shown to be localized on preexisting Paleoproterozoic zones of deformation. Thus, we do not find compelling evidence for a ∼1.4 Ga orogeny related to the formation of most of these granites. Renewed intrusions at ∼1.0–1.1 Ga between and immediately following phases of the Grenville orogeny indicate that situations leading to their formation need to be more broadly considered. The origin of this red granite-forming event in Laurentia and Baltica is considered as part of a global magmatic event that was coeval with intrusion of massif anorthosites and associated charnockites. Most are viewed as anorogenic, but it is recognized that the same conditions leading to their formation may have occurred during extensional phases of orogens. The immense volumes of red granites produced are also essentially unique to the Mesoproterozoic and appear to be tied to the stabilization and eventual break up of supercontinents of both Paleoproterozoic and Mesoproterozoic age. [Copyright &y& Elsevier]

The early Cretaceous Gross Spitzkoppe granite is one of several igneous complexes that formed in the Damaraland of Namibia during an episode of continental rifting and magmatism associated with opening of the South Atlantic. This is a classic setting of rift-related, anorogenic magmatism showing the typical association of mantle-derived mafic and alkaline rocks along with silicic units. The Gross Spitzkoppe granite is an important example of the latter because its peraluminous composition and crustal isotopic signature makes it well suited to characterize the crustal contribution to magmatism. The Gross Spitzkoppe stock (GSS) is composed of three texturally distinct topaz-bearing biotite monzogranites (average 76 wt.% SiO2, ∼30 wt.% Rb/Sr and ∼0.5 wt.% F). Iron-rich biotite is the only mafic silicate. In proximity to the stock are numerous felsic dikes (rhyodacites to rhyolites). The elevated high-field-strength elements (HFSE) contents and high Ga/Al ratios of the granites and felsic dikes are typical of A-type granites. The granites and dikes show similar geochemical differentiation trends and the compositions of the more evolved dikes overlaps with the granites. This and similar initial isotope ratios suggest that the dikes and granites have a common origin. Major and trace element modeling confirms that the composition of the Gross Spitzkoppe granite can be produced by fractional crystallization from magma with the average felsic dike composition.Rb–Sr isotope data for nine whole-rock samples of the GSS yield an age for emplacement of the complex at 125±1 Ma. Initial 87Sr/86Sr ratios vary from 0.710 to 0.716. Neodymium isotope compositions of the granites and dikes yield initial &epsiv;Nd125 values from −5.6 to −6.4. The Pb isotopic ratios (K-feldspar or age-corrected whole rock) fall in the range 206Pb/204Pb 18.70–18.82, 207Pb/204Pb 15.66–15.71, and 208Pb/204Pb 38.57–39.07. These geochemical and isotopic characteristics are consistent with derivation of the Gross Spitzkoppe granitic magma from a granulite-facies metasedimentary source. Batch melting calculations suggest that low (10–20%) degree partial melting of a felsic granulitic source is capable of producing melt compositions similar to those of the felsic dikes, with further fractional crystallization being required to produce the granites. The source rocks are thought to be Damara Belt metasediments that were melt-depleted in the early Paleozoic by extraction of the S-type Damara granites. The most likely scenario for crustal melting is by basaltic underplating of the source region in the lower crust. The range in initial Nd and Sr values is attributed to minor mixing of basaltic magma with the crustal melts, although Sr was also affected by minor contamination from the radiogenic Damara granites near the level of emplacement. [Copyright &y& Elsevier]

The 1.43-Ga Sherman batholith of southeastern Wyoming and northeastern Colorado is a texturally and geochemically heterogeneous intrusion that comprises rocks derived from at least four different sources. The coarse-grained, metaluminous, biotite-hornblende Sherman Granite is volumetrically the most significant unit in the batholith. It has geochemical characteristics at the extreme end of A-type suites with high Fe# > 88, high K[sub2]O wt. % (generally > 5%), molar Na/K generally < 1, and high abundances of incompatible elements. The source for the Sherman Granite is constrained to be a Fe-rich, low oxygen fugacity source mafic material by initial isotopic ratios (ε[subNd] = -0.8-1.1 and initial [sub87]Sr/[sub86]Sr = 0.7024-0.7126), low oxygen fugacity (-0.1 to -0.5 log units below the fayalite-magnetite-quartz buffer reaction) and water activity (∼ 0.7), comparisons to experimental melt compositions, and mineralogical and geochemical similarities to monzonitic intrusions from the Laramie anorthosite complex (LAC). The medium-grained, peraluminous Lincoln granite, which is volumetrically subordinate to the Sherman Granite, has less extreme A-type geochemical characteristics. Initial isotopic ratios (ε [subNd] = ∼-1 and initial [sup87]Sr/[sup86]Sr = 0.7189 and 0.7238), comparisons to experimental melt compositions, and geochemical similarities to intrusions from the peraluminous Silver Plume suite favor a parental magma for the Lincoln granite derived from intermediate to felsic crustal rocks from the Colorado province, which forms the basement to the Sherman batholith. A suite of mineralogically heterogeneous biotite-hornblende porphyritic quartz monzonites and granites has geochemical characteristics that also fit the A-type classification but are less extreme than that for the Sherman Granite, with distinctly lower Fe# (< 88) and molar Na/K (generally 1). Field and geochemical observations are consistent with many of the... [ABSTRACT FROM AUTHOR]

Tin and other high-field-strength (HFS) elements are becoming increasingly significant, driven by technological advancements and a global effort to develop alternative energy solutions. A-type granites are associated with the mineralisation of these critical metals and therefore, investigating the influences on their metallogenic potential is essential for future exploration. The geochemical comparison between selected mineralised and unmineralised African A-Type granites, highlights the importance and implications of fractionation, crustal contamination, crustal emplacement and the composition and evolution of the magmatic-hydrothermal fluid in the development of endogranitic Sn mineralisation. Trace elemental ratios such as Zr/Hf, Nb/Ta and Y/Ho demonstrate the relationship between the degree of fractionation and interaction with acidic, F- and Cl-rich magmatic-hydrothermal fluids in these mineralised and barren African examples. Circumstantial differences in magmatic origin, not only directly influence the metallogenic budget of a granite but also influence the F and B content of the later stages of felsic magmatism. These volatiles prolong fractionation, consequently facilitating the likelihood of HFS element saturation and the development of an economic deposit. Moreover, the combination of continental setting and the enrichment of HFS and volatile elements by the assimilation of fortuitous crustal lithologies can upgrade an originally unfavourable magma composition, to one with a potential for mineralisation. It is therefore shown that mineralisation is ultimately achieved through a series of sequential, incompatible and HFS element enrichment stages, which culminate in the accumulation of sufficient metals to produce economically significant mineralisation. • Major and Trace element geochemistry review of African A-Type granites. • Fractionation, contamination, crustal emplacement and hydrothermal fluid influence A-Type granite metallogenic potential • The fortuitous assimilation of crustal material can upgrade an uneconomic magma to a viable mineralisation candidate. [ABSTRACT FROM AUTHOR]

The 1·43 Ga Sherman batholith, southeastern Wyoming, USA, shows extreme A-type petrochemical characteristics compared with other Mid-Proterozoic granite batholiths of North America. It consists of: (1) the Sherman granite, a coarse-grained biotite hornblende granite that locally contains fayalite and pyroxenes; (2) the Lincoln granite, a medium-grained biotite granite; (3) a porphyritic biotite hornblende granite that probably formed by interaction of granitic and mafic magmas; and (4) iron-enriched mafic dikes and pods. The ilmenite-series, metaluminous Sherman granite exhibits extreme values of FeOt/(FeOt + MgO) and is rich in K, REE, Nb and Y. It crystallized at temperatures exceeding 900°C and a pressure of ~2·5 kbar, with water activity of 0·7 and [Delta]log fO2 of -0·1 to -0·5. The Lincoln granite, which is peraluminous and has less extreme A-type geochemical characteristics, crystallized at temperatures as low as 750°C and [Delta]log fO2 of around 0·5 units above FMQ (fayalite-magnetite-quartz). The rocks of the Sherman batholith are chemically equivalent to lavas from the Yellowstone hotspot. Like the Yellowstone magmas, the Sherman batholith probably originated by partial melting of underplated, mantle-derived mafic rocks. [ABSTRACT FROM PUBLISHER]

Following accretion of southern Siberian microcontinents to the Siberian craton in the Early Paleozoic, five cycles of K-rich silicic magmatism, progressively decaying in volume, occurred on batholithic scales throughout the Paleozoic and Early Mesozoic, followed by rift-related alkali volcanism of Jurassic to Recent age. Most of the post-Ordovician magmatism occurred within the Ordovician accreted terrane of Transbaikalia, during its 400 my of cratonization. Basic magmas may be critical in the generation of K-rich silicic magma, yet only subordinate volumes of coeval mafic rocks in the silicic plutons and synchronous volcanics are present. Most of the mafic rocks contain plagioclase megacrysts (1-5 mm), and these were used to reconstruct the primary basic magma chemistry and its evolution with time. Optical and scanning electron microscopy studies, and electron microprobe profiling through plagioclase megacrysts of different ages revealed unzoned, Ca-rich cores in a number of crystals in each sample. Several crystals within each rock in a number of rocks within each age group were studied. Several ion microprobe analyses inside each of these cores were made for concentrations of Li, Be, B, F, Mg, P, Cl, K, Ti, Fe, Co, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, and Pb. In addition, partition coefficients for the same trace elements and the relevant compositional range of plagioclase were used to convert trace element concentrations in Transbaikalian plagioclase to parental magmatic values. Whole-rock and whole-plagioclase analyses for oxygen isotopes and trace elements were also made to constrain the amount of contamination of basic magma and study its temporal trends. Plagioclase core compositions reveal up to one order of magnitude variation of some trace elements and ratios between suites, and show a progressive change in trace element concentration with decreasing age. Plagioclase megacrysts and the reconstructed basic magmas exhibit depletion in large ion lithophile elements, volatile elements, light rare earth elements and [delta]18O, and simultaneous increase in high field strength elements and K. We speculate on tectonic implications of the established chemical trends as reflecting progressive incompatible element depletion and devolatilization of a mantle source and increasing prevalence of alkali basalt from the sublithospheric mantle in the course of cratonization. [ABSTRACT FROM PUBLISHER]

Proterozoic plutonism in Colorado and Wyoming was initatied ∼ 1.8 Ga with scattered tholeiitic mafic complexes coeval with widespread synorogenic bimodal volcanism. Limited Nd and Sr isotopic data for the metavolcanic rocks show derivation from depleted mantle. Major Paleoproterozoic granitic plutonism followed at 1.67-1.77 Ga. Most of the earliest plutons are distinctly calc-alkaline; they range largely from quartz diorite to granodiorite to trondhjemite in composition, and have trace-element signatures similar to plutons within magmatic arcs related to subduction zones. Later Paleoproterozoic plutons at 1.71 Ga include increased volumes of felsic rock types and, independent of silica, are shifted to more peraluminous and iron-rich compositions. The earliest appearance of anorthosite occurs with the 1.76-Ga Horse Creek anorthosite complex of Wyoming, and the earliest occurrence of A-type granite includes the late-kinematic, 1.66-Ga Garell Peak batholith of southern Colorado. Elemental and isotopic compositions of the younger Early Paleoproterozoic granitic plutons are consistent with a systematically increasing crustal component as a function of age in waning orogenic stages of crust formation in the region. After a 200 m.y. hiatus, renewed granitic plutonism occurred at 1.36-1.44 Ga. Plutonism was associated with emplacement of over a dozen Mesoproterozoic A-type granite batholiths and many smaller intrusions as part of a global "anorogenic" mid-Proterozoic event that commonly includes associated intrusions of anorthosite and charnockite. Across the former Laurentia supercontinent, three geographic and petrologic subprovinces merge in Colorado and Wyoming. An ilmenite-series granitic province, which includes the Sherman Granite and associated Laramie anorthosite complex of Wyoming, extends northeastward through Wisconsin to Labrador and the classic rapakivi granite-anorthosite intrusions of the Baltic region. A magnetite-series granite subprovince ranges... [ABSTRACT FROM AUTHOR]

• Zircon Hf-O isotopes reveal decoupling of mantle-like δ18O values (5.1–7.4) and ancient crustal-like ε Hf (T) values (−4.0 to −8.9). • Zircon U-Pb age of Damiao anorthosite and regional age correlation suggest that the anorthosite was emplaced in an anorogenic extensional setting. • Compilation of Sr-Nd-O isotopic data of massif-type anorthosites indicate important lower crustal input in their magma sources. The formation of massif-type anorthosites and the associated mangerite, charnockite and (rapakivi-) granite (AMCG suite) are mostly restricted in the "Earth's Middle Age" (~1.70–0.75 Ga), and the magma sources of massif-type anorthosites are highly debated between the depleted mantle and the mafic lower crust. The ~1.7 Ga Damiao massif-type anorthosite in the North China Craton consists mainly of anorthosite and leuconorite with minor melanorite, mangerite, Fe-Ti-(P) ores and abundant ferrodioritic or gabbroic dykes. In-situ zircon Hf-O isotopic data from anorthosite reveal decoupling of mantle-like δ18O values (5.1–7.4) and ancient crustal-like ε Hf (T) values (−4.0 to −8.9). Since the significant 177Lu/176Hf reduction in the lower mafic crust, the mafic lower crustal materials derived from depleted mantle could display an ancient crustal medium to high negative ε Hf (T) values after long period of time (e.g., 0.5–1.0 Ga). In contrast, if no supracrustal materials were added, these mafic crustal materials would retain the mantle δ18O features. Thus, the decoupling of mantle-like δ18O and ancient crustal-like ε Hf (T) values suggest a lower crustal origin of the Damiao massif-type anorthosite. Compilation of Sr-Nd-O isotopic data of massif-type anorthosites reveal decoupling of ε Hf (T), initial 87Sr/86Sr and δ18O values, which signifies important lower crustal input in magmas sources of most massif-type anorthosites. We proposed that zircon U-Pb age of the Damiao massif-type anorthosite (~1.70 Ga) and regional age correlation suggest that the anorthosite was emplaced in an intraplate, anorogenic extensional setting after the Paleoproterozoic orogeny had ended. [ABSTRACT FROM AUTHOR]

Abstract: This introductory article of the IGCP-510 Special Issue of Lithos presents the goals of IGCP Project 510 (A-type Granites and Related Rocks through Time), activities in the first two years (2005–2006) of the project, and plans for the years 2007–2009. The 11 research papers in this issue are based on papers presented at the inaugural meeting of IGCP-510 in conjunction with the 15th Goldschmidt Conference in Moscow, Idaho, USA in 2005. [Copyright &y& Elsevier]