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[Display omitted] • Phanerozoic granitoids are used to constrain the north boundary of the Alxa Block. • The granitoids show juvenile and ancient source provinces with contrasting isotopes. • Tectonic belts with juvenile crust (T DM 2 < 1.30 Ga) could be parts of CAOB. • Tectonic belts dominated by ancient crust (T DM 2 > 1.30 Ga) belong to the Alxa Block. The Alxa Block, located in the southern Alxa area of Inner Mongolia, is generally accepted as the westernmost part of the North China Craton (NCC), but there is still a controversy over the boundary between the southern CAOB and the Alxa Block. Currently, either the Enger Us ophiolite belt or Quagan Qulu ophiolite belt in the mid-eastern Alxa area is a candidate for the NCC-CAOB boundary, and the extension of the two ophiolite belts in the western Alxa area is ambiguous. In this study, we present a compilation of newly obtained and published zircon U-Pb age and Hf isotopic data from the Ordovician-Triassic granitoids in the Alxa area and discuss the implications of two contrasting isotope provinces for the NCC-CAOB boundary. Specifically, the granitoids in the Zongnaishan-Shalazhashan belt between the two ophiolite belts and the North Beidashan belt in the western Alxa area share similar emplacement ages (Carboniferous to Triassic) and juvenile zircon Hf isotopic compositions (two-stage mode ages < 1.30 Ga), and both Carboniferous to Permian granitoids in the Yabulai-Honggueryulin belt to the south of Quagan Qulu ophiolite belt and Ordovician to Devonian granitoids in the South Beidashan belt of the western Alxa area are characterized by similar ancient zircon Hf isotopic features (two-stage mode ages > 1.30 Ga), but most Late Carboniferous to Permian granitoids in the South Beidashan belt are characterized by juvenile zircon Hf isotopes. The two contrasting isotope provinces (juvenile in the north and generally ancient in the south) for the Phanerozoic granitoids could not result from differential denudation, but drastic differences in compositions of deep crusts. The Yabulai-Honggueryulin and South Beidashan belts with ancient crust sources are parts of the Alxa Block, whereas the Zongnaishan-Shalazhashan and North Beidashan belts with juvenile crust sources could be parts of CAOB, and thus the boundary between the CAOB and the Alxa Block is inferred located in between. [ABSTRACT FROM AUTHOR]

To constrain the behavior of K isotopes during granitic magmatic differentiation, we present high-precision K isotope data for bulk granitoids and their K-bearing minerals from Dabie and Himalayan orogens in China. Plagioclase displays extremely large K isotopic variation, with δ41K ranging from −0.56 to 1.91‰. Other minerals also have heterogeneous K isotopic compositions, with δ41K varying from −0.56 to −0.24‰ in hornblende, from −0.72 to −0.39‰ in biotite, from −0.79 to −0.47‰ in K-feldspar, and from −0.74 to −0.61‰ in muscovite. The general trend of 41K enrichment follows the order of plagioclase ≫ hornblende > biotite ≈ K-feldspar ≥ muscovite, which can be attributed to the difference in K O bond strengths. Both δ41K of plagioclase and K isotope fractionation factors between plagioclase and other minerals are negatively correlated with K concentration in plagioclase, suggesting a compositional control on isotope fractionations. Inter-mineral K isotope fractionations among other minerals are roughly temperature-dependent. Potassium isotopic compositions of whole rocks display measurable variations (δ41K = –0.69 to −0.28‰), which are correlated with proxies for plagioclase fractionation (e.g., Sr and Rb/Sr). The correlation indicates that fractional crystallization may account for the whole-rock K isotopic variations observed in high-silica igneous rocks, which is supported by modeling of fractional crystallization using the apparent isotope fractionation factors determined in this work. Our study demonstrates the existence of large K isotope fractionation during granitic magmatism, making K isotopes a potential tool for studying differentiation of felsic magmas. [ABSTRACT FROM AUTHOR]

Geochemical analyses of individual minerals provide more detailed insights into the petrogenesis of igneous rocks than whole-rock analyses. This study conducted in situ geochemical and Nd isotope analyses of apatites from 10 Jurassic granitic plutons in the Yanbian area, NE China, to establish the petrogenesis and regional tectonic evolution. The results indicate that the apatite geochemistry of Jurassic granitoids in the Yanbian area was controlled primarily by the composition of parental melt. Post-magmatic alteration may lead to geochemical decoupling between apatite and parental melt, while Nd isotopes exhibit some resilience to such alterations. Apatites from Early Jurassic granitoids display characteristics that are consistent with an I-type origin, whereas those from Middle and Late Jurassic granitoids exhibit an adakitic affinity. Variations in apatite compositions indicate the fractional crystallization of other rare earth element (REE)-bearing minerals during magma evolution. The early crystallization of plagioclase and allanite led to decreases in Sr and Th contents in apatite, respectively, resulting in a negative Eu anomaly and light REE depletion. The fractional crystallization of titanite and hornblende resulted in the depletion of middle REE in apatite. Hornblende is regarded as the main residual phase in the magma source of Middle and Late Jurassic adakitic granitoids in the Yanbian area. Apatite Nd isotopic compositions suggest that the Jurassic granitoids in the Yanbian area originated from two crustal sources: the Central Asian Orogenic Belt and the North China Craton. Additionally, increasing trends in apatite Sr/Y and (La/Yb) N ratios from the Early to Late Jurassic suggest a gradual thickening of the regional crust, which is likely driven by the continentward migration of the subduction zone associated with the Paleo-Pacific Plate. • Apatite geochemistry is indicative of magma evolution and post-magmatic alteration. • Variations in apatite trace elements reveal mineral fractional crystallization. • Apatite geochemistry reveals the genetic types and magma sources of granitoids. • Jurassic granites in the Yanbian area were formed by the Paleo-Pacific Plate subduction. [ABSTRACT FROM AUTHOR]

The West Qinling Orogen (WQO) of the northeastern region of the Tibet Plateau occupies a key tectonic position at the junction between the Pan-Asian and the Tethyan tectonic domains. However, there are ongoing debates regarding the exact timing of final continental collision in the WQO and closure time for the Paleo-Tethyan ocean. Here, we present LA-ICP-MS zircon U Pb dating results along with major-trace elemental and Sr-Nd-Hf isotopic data for four granitic plutons across the western WQO, from north to south including Xiangyu, Tongren, Heri, and Wenquan. Notably, both the Tongren and Wenquan plutons contain abundant mafic microgranular enclaves (MMEs). Our new data indicate that the Xiangyu granites were emplaced at 249 Ma in a continental arc setting. These rocks are high-K calc-alkaline, formed by partial melting of Precambrian basement within the normal lower crust (< 40 km) followed by fractional crystallization of primary crustal melts. The Heri granitoids were emplaced at 237 Ma in a continental arc setting as well. They are also high-K calc-alkaline, but generated by partial melting of Precambrian basement at depths of 40–50 km. The Wenquan granitoids along with MMEs were emplaced at 234–233 Ma in a continental arc setting. The enclave magmas were formed through orthopyroxene-dominant fractional crystallization of primary mantle-derived melts originating from a phlogopite-bearing lherzolitic lithosphere at depths no more than 60 km, while the host granitoids were formed through mixing of the crustal melts resembling the Heri granitoids with approximately 40 to 60% enclave magmas. The Tongren granitoids along with MMEs were emplaced at 231–228 Ma in a back-arc setting. The enclave magmas originated from a phlogopite-bearing lherzolitic lithosphere at depths of 60–70 km, while the host granitoids were formed through mixing of the crustal melts resembling the Xiangyu granites with approximately 18 to 40% enclave magmas. We suggest that the Paleo-Tethyan (Anemaqen) oceanic crust had subducted northward approaching the northernmost WQO by 249 Ma followed by the initiation and gradual southward migration of the oceanic slab rollback. The slab subduction did not cease at least before 228 Ma. • We have investigated four Triassic granitic plutons in western West Qinling Orogen. • The 249–233 Ma granites and microgranular enclaves formed in continental-arc setting. • The 231–228 Ma granites and microgranular enclaves formed in back-arc setting. • The origin of these rocks recorded the Paleo-Tethyan oceanic crust advance to retreat. [ABSTRACT FROM AUTHOR]

[Display omitted] • Episodic crustal growth occurred in the microcontinents within the eastern CAOB. • Most of the continental crust in the microcontinents accreted in the Precambrian. • The varying rates of regional crustal growth are linked to supercontinent cycles. The crustal growth and reworking processes of accretionary orogen such as the Central Asian Orogenic Belt (CAOB) have been a controversial issue. Here, we present in situ zircon U–Pb and Lu–Hf isotopic data for granitoids from a microcontinent (the Songnen Massif) and an arc terrane (the Duobaoshan arc terrane), which generally represent two main crustal components in the eastern CAOB to establish a crustal growth model for an accretionary orogen and to trace the influence of the assembly and breakup of supercontinents on crustal evolution in an accretionary orogen. Neoproterozoic–Mesozoic granitoids distributed in the Songnen Massif show a step-like crustal growth pattern over time with three major periods of development: Paleoproterozoic crustal growth at 2.2–1.8 Ga, Mesoproterozoic growth at 1.6–1.0 Ga, and a third pulse of growth at 0.85–0.6 Ga, along with two short pauses at 1.8–1.6 Ga and 1.0–0.85 Ga. The assembly and collision phases of supercontinents corresponded to the enhanced and degressive crustal growth rates of the Songnen Massif, respectively, suggesting that the supercontinent cycles are responsible for the episodic crustal growth pattern in the region. Crustal reworking of the Songnen Massif occurred during 1000–180 Ma, with a fluctuation at 800–600 Ma, which provided a major contribution to the isotopic heterogeneity of lower continental crust. Isotopic compositions of granitoids from the Duobaoshan arc terrane located between the Xing'an and Songnen massifs, together with those of granitoids from other microcontinents, suggest that most of the continental crust beneath the microcontinents in the eastern CAOB generated during the Precambrian, whereas a significant amount of lateral crustal accretion occurred in continental arc settings during orogenies and amalgamation of microcontinents during the Phanerozoic. [ABSTRACT FROM AUTHOR]

One of the drawbacks of fusible clays is the narrow sintering interval due to a sharp increase in the amount of iron-silicate melt at a temperature of 1000–1100 °C, which hardens in the form of a glass phase upon cooling. This leads to a relatively low mechanical strength of the calcined samples and causes the danger of melting the granular material surface from such clays during the firing process. To increase the strength of samples of fusible clays, the influence of diabase and granitoid rocks was considered. It was found that the strengthening effect of diabase and granitoid rock additives in an amount of 20–50% in a mixture with fusible clay is due to an increase of total content of the crystalline phase (mullite, cristobalite and residual quartz) from 18–20% in clays without additives to 22–28 % - in mixtures with diabase and to 28–34% - with granitoid additives) at a temperature of 1050–1100 °C. This increase is due to the activation of synthesis processes of secondary mullite and crystallization from alkali-rich feldspar melt of amorphous silica, released from the structure of clay minerals. The established influence of the igneous rocks used made it possible to develop compositions and propose process flow sheet for producing aluminosilicate proppants based on fusible clays. The use of granitoid and diabase rocks in an amount of 20–70% with fusible clays produces lightweight aluminosilicate proppants with bulk density of 1.40–1.46 g/cm3 at temperature range of 1050–1100 °C, which can endure destructive pressures up to 34.5–52 MPa. [ABSTRACT FROM AUTHOR]

• The JIC preserves two magmatic arc events with second event being a magmatic flare-up generated between 1814 and 1795 Ma. • New and published zircon U-Pb ages compiled for the JIC. • Distinct crustal architectures between Makkovik Province and the Ketilidian Orogen. • Julianehåb Igneous Complex (JIC) preserves mid-crustal levels. • Geochronological correlation between Makkovik Province, Ketilidian Orogen and the Transscandinavian Igneous Belt. The Central Domain of the Ketilidian Orogen in South Greenland preserves two magmatic events that provide insight into crustal architecture and represent a major contribution to continental crustal growth in connection with the assembly of the late Paleoproterozoic-Mesoproterozoic supercontinent Columbia/Nuna. This study provides zircon U-Pb geochronology for the western parts of the Central Domain and, combined with previous published age data, documents crustal evolution in the orogeny. The geochronological data indicate an initial volumetrically-minor magmatic event at ca. 1850 Ma, referred to here as the Older Julianehåb Igneous Suite, followed by a pause in magmatic activity. This is followed by the Younger Julianehåb Igneous Suite, a major pulse of magmatism (comparable to magmatic flare-ups in Phanerozoic arcs) between ca. 1814 and 1795 Ma. The adjacent arcs in the Makkovik Province, Canada, and the Transscandinavian Igneous Belt, Scandinavia, preserve similarly-aged magmatic events and appear to young from west to east. Exposure levels in the Makkovik Province are shallower than in the Ketilidian Orogen, and shallower supracrustal deposits are significantly more abundant in the Makkovik Province, indicating significant differences in modern erosion levels. [ABSTRACT FROM AUTHOR]

The tectonic setting of Indosinian magmatism in West Qinling Orogen and the tectonic evolution of the Paleo-Tethys remain hotly debated. Here we present SHRIMP zircon U Pb dating, major-trace elemental and Sr-Nd-Pb-Hf isotopic data for four granitic and gabbroic plutons across the eastern West Qinling Orogen, from north to south including Guanshan, Fengxian, Mishuling and Miba. Our new data indicate that the Fengxian granitoids, emplaced at 238 Ma in a continental arc setting, show adakitic affinity and were formed by partial melting of subducted sediments. The southern Guanshan granitoids, emplaced at 235–229 Ma in a continental arc setting, also show adakitic affinity but were generated by partial melting of thickened (>50 km) lower crust. The northern Guanshan granites and gabbros were emplaced at 217–216 Ma in a back-arc setting, with the former generated by partial melting of normal (40–50 km) lower crust and the latter derived from asthenospheric mantle. The Mishuling granitic pluton contains abundant mafic microgranular enclaves, both emplaced at 214 Ma in a back-arc setting with the host granitoids formed by partial melting of normal (40–50 km) lower crust and the enclave magmas derived from asthenospheric-lithospheric mantle. The Miba granitoids, emplaced at 216 Ma in a continental arc setting, show adakitic affinity and were generated by partial melting of thickened (>50 km) lower crust. We suggest that the Paleo-Tethyan oceanic crust had subducted near the Shangdan suture by 238 Ma and successively advanced northward, approaching southeastern Qilian Orogen at 235–229 Ma. Then slab rollback initiated and gradually migrated southward. The slab subduction did not cease before 214 Ma. • We have investigated four Triassic granitic-gabbroic plutons in West Qinling Orogen. • The granitoids formed in a continental-arc setting during the Ladinian-Carnian. • The granitoids, enclaves and gabbros formed in a back-arc setting during the Norian. • The origin of these rocks recorded the Paleo-Tethyan oceanic crust advance to retreat. [ABSTRACT FROM AUTHOR]

Mesozoic granitoids are widely distributed in South China, but the mechanism for generating the felsic magmas is still in debate. To understand the possible origin of the granitoids, we use joint inversion methods and forward modelling of receiver functions to reveal the lithospheric structure in the Cathaysia block. The joint inversion of receiver functions and surface wave dispersion with P-velocity constraints is applied to a dense array in the Cathaysia block, and the specific crustal Vp/Vs ratios obtained from a generalized H-κ stacking method are introduced to the traditional joint inversion for passive seismic stations. The detailed structures provide valuable knowledge of the geological processes: 1) The present-day lithosphere is 60–70 km thick, which has been thinned since the Late Mesozoic with reference to geochemical data; 2) there is a lack of high Vp and Vs in the lower crust in this region. The results may have limited resolution on the localized magmatic underplating, but they do not support the extensive magmatic underplating at the Late Mesozoic. Other factors could be the mechanism for the granitoid formation in this region. • Performed joint inversion of receiver function and dispersion with Vp constraint • Found lithospheric thickness of Cathaysia block comparable to that of eastern North China Craton • No high velocity in the lower crust that is consistent with the magmatic underplating [ABSTRACT FROM AUTHOR]

Abstract Whole rock major and trace element geochemistry together with zircon U-Pb ages and Sr-Nd isotope compositions for the Middle Eocene intrusive rocks in the Haji Abad region are presented. The granitoid hosts, including granodiorite and diorite, yielded zircon U-Pb ages with a weighted mean value of 40.0 ± 0.7 Ma for the granodiorite phase. Mafic microgranular enclaves (MMEs) are common in these plutons, and have relatively low SiO 2 contents (53.04–57.08 wt.%) and high Mg# (42.6–60.1), probably reflecting a mantle-derived origin. The host rocks are metaluminous (A/CNK = 0.69–1.03), arc-related calc-alkaline, and I-type in composition, possessing higher SiO 2 contents (59.7–66.77 wt.%) and lower Mg# (38.6–52.2); they are considered a product of partial melting of the mafic lower crust. Chondrite-normalized REE patterns of the MMEs and granitoid hosts are characterized by LREE enrichment and show slight negative Eu anomalies (Eu/Eu* = 0.60–0.93). The host granodiorite samples yield (87Sr/86Sr) i ratios ranging from 0.70498 to 0.70591, positive ε Nd (t) values varying from +0.21 to +2.3, and T DM2 ranging from 760 to 909 Ma, which is consistent with that of associated mafic microgranular enclaves (87Sr/86Sr) i = 0.705111–0.705113, ε Nd (t) = +2.14 to +2.16, T DM2 = 697–785 Ma). Petrographic and geochemical characterization together with bulk rock Nd-Sr isotopic data suggest that host rocks and associated enclaves originated by interaction between basaltic lower crust-derived felsic and mantle-derived mafic magmas in an active continental margin arc environment. Graphical abstract Image 1 Highlights • The Haji Abad granitoids (HAG) are I-type in composition. • The HAG was emplaced ca. 40 Ma on the central Urumieh-Dokhtar magmatic assemblage. • Interaction between lower crust-derived felsic and mantle-derived mafic magmas. • These granites are compared with the A-type and I-type granitoids from the UDMA. • A subduction generated magmatic system in a pre-plate collisional setting. [ABSTRACT FROM AUTHOR]

Abstract Intense magmatism and voluminous sedimentation occurred in the Jiaodong Peninsula during Mesozoic in response to the lithospheric thinning in eastern North China Craton (NCC). Here we report the results from an integrated geochemical and Sr-Nd-Pb-Hf isotopic study on granitoids and U Pb and Lu Hf isotopes of the detrital zircons from Mesozoic sediments in the Jiaodong Peninsula to provide new constraints on the crustal response to the lithospheric thinning. Geochronologic data reveal three distinct magmatic pulses at 170–140 Ma, 140–125 Ma and 125–105 Ma in this region. The Sr-Nd-Pb isotope data (0.7080–0.7139 for 87Sr/86Sr, −22.3−−10.8 for ɛ Nd (t), 16.97–17.47 for 206Pb/204Pb, 15.42–15.55 for 207Pb/204Pb, 37.36–38.34 for 208Pb/204Pb) and zircon ɛ Hf (t) values (−29−−10) for the Mesozoic plutons show more similarities with those of the lower crust of the Yangtze Craton (YC) wedged beneath the NCC, than those of the NCC. The Sr/Y, (La/Yb) N and Nb/Ta ratios for the three episodes of granitic magmatism show a gradual decrease, which is interpreted to reflect upward migration of the depth of partial melting from ~170 Ma to ~105 Ma. The dominant detrital zircon population in the sediments deposited during ca. 125–105 Ma was derived from pre-Jurassic sources in the NCC and YC basement whereas the Cretaceous population was derived from volcanic rocks in the interior of the craton. The alternating sequence suggests episodic uplift of the NCC and YC basements during this period. The data obtained in this study allow us to summarize the crustal evolution of this region into three phases. (1) During 170–140 Ma, partial melting of wedged YC lower crust resulted in high magmatic flux. (2) During 140–125 Ma, intense magmatism continued, accompanied by uplift and erosion of basement, and initiation of basin filling. (3) During 125–105 Ma, the source depth of granitoid magma became shallower associated with continuing episodic basement uplift, representing the peak of lithospheric thinning. Graphical abstract Unlabelled Image Highlights • Gradual shallowing of magma source for Late Mesozoic granitoids in Jiaodong. • The magmas were sourced from the Yangtze lower crust. • The crustal evolution in Jiaodong Peninsula includes three distinct phases. • The deep magmatism was synchronized with the surface uplift. [ABSTRACT FROM AUTHOR]

The ancient cores of modern continents, cratons, are the oldest blocks of "stable" lithosphere on Earth. Their long-term survival relies on the resistance of their underlying thick, strong, and buoyant mantle keels to subsequent recycling. However, the effect of substantial geographical variations in keel thickness on the post-assembly behaviour and mass movement within these continental cores remains unknown. Here, we demonstrate that the spatial distribution of fluid-reset in-situ Rb-Sr ages for Paleo-Mesoarchean (3.6–2.8 billion years ago; Ga) granitoids of the Pilbara Craton, Australia shows remarkable correlation with independently-constrained lithospheric thickness models. Without craton-wide heating/magmatic events, these anomalously young Rb-Sr ages document episodes of fluid infiltration into granitoid complexes as a response to lithospheric reactivation by far-field stresses. This correlation implies that craton-wide fluid mobilization triggered by extra-cratonic Neoarchean to Mesoproterozoic (2.8–1.0 Ga) tectonic events is facilitated by variations in lithospheric strength and thickness. Compared to areas of older overprints, the two-thirds of the craton comprised of younger reset ages is underlain by comparatively thin lithosphere with higher susceptibility to reactivation-assisted fluid flow. We propose that even the strongest, most pristine cratons are less stable and impermeable than previously thought, as demonstrated by the role of granitoid complexes and cratons as selective lithospheric "sponges" in response to minor tectonic forces. Therefore, variations in lithospheric thickness, likely attained before cratonization, exert a crucial control on billions of years of fluid movement, elemental redistribution and mineralization within ancient continental nuclei. • In-situ Rb-Sr ages of Pilbara Craton granitoids record anomalously young fluid overprints. • Overprint ages correspond to outboard Neoarchean and Paleo-Mesoproterozoic tectonism. • Spatial variations in overprint ages correlate with lithospheric thickness. • Older overprints are hosted in thick lithosphere; younger overprints in thin lithosphere. • Cratonic lithosphere thickness controls far-field stress-triggered fluid flow events. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dafang granitoid zircon U-Pb ages related to coeval magmatic and metallogenic events. • Dafand granitoid mainly derived from Paleoproterozoic middle-lower crust. • Pb-Zn and W-Sn metallogenic variations are determined by magmatic source, redox state and evolution degree. • Oxidized and reduced magmas related to Pb-Zn and W-Sn deposits, respectively. The Nanling Metallogenic Belt (NMB) in South China contains huge amounts of Middle to Late Jurassic granitoid-related polymetallic Pb-Zn and W-Sn deposits. Whether there is a link between granitoid genesis and mineral species and what specific factors control the metallogenic specialization remained unclear. Herein, we presented a systematic investigation on the Dafang Pb-Zn ore-causative intrusion, and then placed it into the compiled comprehensive dataset of the NMB ore-hosting granitoids aiming to reveal the magmatic control on the Pb-Zn and W-Sn metallogenic variations in South China. Our results illustrate that the Dafang granitoid is potassic, alkaline (Na 2 O + K 2 O: 5.84 % to 7.87 wt%) and meta-luminous (A/CNK: 0.75 to 1.01), with middle SiO 2 content (60.59–65.15 wt%), displaying an analogous nature of I-type granitoids. Trace elements of all samples are characterized by a significant enrichment in LREEs, Pb, and K, and a strong depletion of HREEs, HFSEs as well as Ba. Further zircon U-Pb dating yields a concordant age of 157.0 ± 0.8 Ma (MSWD = 1.1), consisting with the Jurassic magmatic-hydrothermal activities in the NMB. Their negative ε Hf (t) values (−6.7 to −10.2) and two-stage Hf model ages (1.6 to 1.7 Ga) suggest that the Dafang granitoid intrusion was generated from the partial melting of a Paleoproterozoic middle-lower crust. By comparing the Dafang with other NMB ore-causative granitoids in the comprehensive dataset, we investigated two types of ore-causative granitoids, i.e., the Pb-Zn- and W-Sn-mineralized granitoids, with distinct magmatic source, redox state and evolution degree. The Pb-Zn-bearing granitoids predominantly generated from amphibolite with a high oxygen fugacity (Ce4+/Ce3+: average 104.8, n = 55) and low differentiation degree (Rb/Sr: average 0.8, n = 60; Nb/Ta: average 12.5, n = 62). In contrast, the W-Sn metallogenic granitoids originated from metasedimentary rocks with a relatively lower oxygen fugacity (Ce4+/Ce3+: average 46.7, n = 258) and higher differentiation degree (Rb/Sr: average 59.0, n = 139; Nb/Ta: average 5.3, n = 156). Collectively, we conclude the Pb-Zn and W-Sn metallogenic variations in the NMB (South China) are jointly determined by magmatic sources, oxygen fugacity and differentiation degree. [ABSTRACT FROM AUTHOR]

Magma mixing or mingling between mafic and felsic magmas is a common phenomenon in granitoid magmatism, and chemical and mechanical interactions between the magmas are frequently observed in granitic rocks. The Dongjiangkou pluton is an example of magma mixing among the numerous early Mesozoic granitoid plutons that are exposed in eastern South Qinling. This pluton is predominantly composed of granodiorite and contains abundant mafic/intermediate microgranular enclaves (MMEs) and is sporadically intruded by mafic dykes. Both the granodiorite and MMEs were crystallized at 224–214 Ma and have inherited zircons of similar age ranges. The granodioritic rocks had metaluminous to weak peraluminous features and adakitic signatures and belong to the high-K calc-alkaline series, whereas the MMEs and dioritic dykes had low SiO 2 contents and metaluminous features and belong to the high-K calc-alkaline to shoshonite series. All of the rocks had high Mg# values and similar geochemical characteristics regarding trace elements and Sr isotopes, but they had diverse whole-rock Nd-Pb and zircon Hf isotopic compositions. The Dongjiangkou granodiorite was produced by partial melting of old basement rocks and Paleozoic juvenile crust beneath South Qinling triggered by asthenospheric upwelling. Magma(s) of the Dongjiangkou MMEs may have been derived from deep mantle and injected into and mixed with the magma(s) of the granodiorite, but chemical and isotopic homogenization was not achieved during the magma mixing process. Clastic rocks may have played a major role in the formation of crust-derived magma(s), causing strong Nd-Hf isotopic decoupling of several granitoid plutons in South Qinling. • Dongjiangkou granite witnesses insufficient mixing of felsic and mafic magmas. • Nd and Hf isotopic equilibrium did not reach during the magma mixing. • Felsic magma originated from old basement and Paleozoic rocks in South Qinling. • Input of clastic rocks to granitic magma source caused Nd-Hf isotopic decoupling. [ABSTRACT FROM AUTHOR]

• New LA-ICP-MS zircon 207Pb/206Pb ages of the Xucun pluton is ca. 830 Ma. • The Neoproterozoic granodiorites belong to the calc-alkaline and high-K calc-alkaline series and geochemically fall into the S-type granite field. • The Neoproterozoic granodiorites were possibly derived from the partial melting of juvenile crust mixed with minor Mesoproterozoic continental crustal rocks. The Jiangnan orogenic belt is a key component of the South China Block, yet the tectonic-magmatic evolution of the orogenic belt remains widely debated. The eastern segment of the Jiangnan orogenic belt experienced Neoproterozoic magmatism evidenced by widespread granitoids, which is key to understanding the tectonic evolution of the orogenic belt. In this study, we conducted detailed field, petrographic, geochemical, and geochronological studies of the Neoproterozoic Xucun pluton and adjacent magmatic rocks in the southern Anhui province of the eastern Jiangnan orogenic belt. Zircon LA-ICP-MS U-Pb dating of two samples yields interpreted crystallization ages of 830.3 ± 2.9 Ma and 831.2 ± 3.3 Ma. The Xuun pluton is an S-type, peraluminous biotite granodiorite that belongs to the calc-alkaline to high-K calc-alkaline series. εNd(t) values for the pluton range from −2.53 to −0.49, and the T DM2 model ages range from 1.66 to 1.83 Ga. The whole-rock, major and trace element and Sm-Nd isotopic compositions of the Xucun pluton suggest petrogenesis in a magmatic arc-related tectonic setting. These new constraints, combined with previous results, indicate that the Xucun pluton formed in a post-collisional tectonic setting. The source for the Xucun pluton was mainly juvenile crust mixed with some Mesoproterozoic continental crust. The juvenile crustal rocks were generated during arc magmatism before ca. 860 Ma. We interpret that the the eastern Jiangnan orogenic belt was generated during the ca. 860–830 Ma collision of the Shuangxiwu arc and a continental terrane. Subsequent collapse of the Jiangnan orogenic belt resulted in erosion and partial melting of juvenile crustal rocks to form S-type granitoids, including the Xucun pluton. [ABSTRACT FROM AUTHOR]

Granitic rocks (sensu lato) are a major rock type in orogenic belts. The crystallization pressures of granitic rocks can help to unravel the magmatic processes and tectonic evolution of these regions, particularly in areas where metamorphic rocks are not exposed. However, geobarometric techniques that are suitable for granitoids are quite limited. In this study, we propose a new approach to estimate crystallization pressures of granitoid magmas using melt inclusions in zircon, a ubiquitous accessory mineral in these lithologies. Homogenization experiments of polymineralic inclusions hosted in zircon have been conducted from a biotite granite sample in the Miocene Miuchi pluton, southwest Japan arc, using a piston-cylinder high-pressure–high-temperature apparatus. The homogenized compositions of the inclusions have high SiO 2 contents (76–80 wt%) implying that they represent fractionated interstitial melts trapped in growing zircon crystals. The rhyolite-MELTS geobarometer for the homogenized melt inclusions in oscillatory-zoned zircon rim yields pressures ranging from 80 to 114 MPa (with error of ±25 MPa), interpreted as the crystallization pressures of the Miuchi pluton. These results are consistent with field and petrographic observations suggestive of a shallow emplacement level. The approach presented here would be applicable to most granitoids, which could provide fundamental data to better understand granite petrogenesis and the tectonic evolution of orogenic belts. • It has been difficult to constrain pressures directly from hornblende-free granitoid. • We propose an alternative approach to estimate crystallization pressure of granitoid. • Homogenized compositions of former melt inclusions in zircon can constrain pressure. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • There are Late Paleozoic granitic plutons along the Longmu Co-Shuanghu suture. • These plutons emplaced between 346 Ma and 364 Ma and formed in a subduction related tectonic setting. • Subduction of the Paleo-Tethys Ocean began in the Late Devonian and lasted till the Triassic. Abstract The Longmu Co-Shuanghu suture zone in central Qiangtang, northern Tibetan plateau, is a segment of the main suture zone of the Paleo-Tethys Ocean. Numerous studies have focused on ophiolite and high-pressure metamorphic rocks from this suture zone, whereas the associated subduction-related magmatic rocks have received little attention. In this study, we present new data for the Late Paleozoic granitoids from the Gangma Co, Guoganjianian and Chasum areas along the Longmu Co-Shuanghu suture zone. Zircon U-Pb dating indicates that these granitic rocks were emplaced between 364 Ma and 346 Ma (Late Devonian-Early Carboniferous). Three granitic plutons exhibit different geochemical compositions, but show uniform Sr-Nd and zircon Hf isotopic features with positive Ɛ Nd (T) and zircon Ɛ Hf (T) values. Furthermore, these rocks were all formed in a volcanic arc setting associated with an oceanic subduction zone. Together with data from coeval volcanic rocks, we suggest that the Late Paleozoic magmatic rocks were formed as a result of northward subduction of the Paleo-Tethys Ocean. Subduction of the Paleo-Tethys Ocean probably commenced in the Late Devonian, continued throughout the Late Paleozoic, and ended in the Triassic. [ABSTRACT FROM AUTHOR]

Neoproterozoic granitoids from the Delhi Fold Belt in NW India record formation and evolution of the marginal orogen in the Rodinia supercontinent. The ca. 976 Ma Moras I-type granites show variable SiO 2 (67.15–75.87 wt%) and CaO (1.10–3.24 wt%) and low REE (59–196 ppm). Their spider diagram is characterized by enrichment of Rb, Th and U and depletion of Na and Ta with positive Pb and negative Sr and Ti anomalies. They have positive ε Nd(t) (+0.41 to +1.40) and ε Hf (+2.34 to +9.35) and moderate δ 18 O values (6.48‰ to 7.58‰). These features suggest that the Moras granites were produced by melting of the juvenile mafic curst. However, the ca. 811 Ma Pali and ca. 780 Ma Mirpur A-type granites have high SiO 2 (74.42–78.63 wt%), K 2 O + Na 2 O (7.74–8.95 wt%) and REE (266–334 ppm). Their spider diagrams are more enriched in Rb, Th and U and depleted in Ba, Sr and Ti. They have lower ε Nd (−2.28 to +0.84) and ε Hf values (−2.31 to +8.62) than, but similar δ 18 O (5.77‰ to 7.01‰) to those of the Moras granites, suggesting that the A-type granites were partial melts of the dehydrated mafic crust in a rift setting. The I- and A-type granites in NW India resulted from physicochemical variations of the lithosphere during evolution of the Rodinia. The Neoproterozoic igneous and sedimentary rocks from the Delhi Fold Belt are well correlated with those from the Jiangnan Fold Belt in South China, suggesting that the two belts probably collected together in the configuration of the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

This study provides new zircon U Pb geochronological and geochemical data for Late Jurassic to Early Cretaceous granitoids in the northern Great Xing'an Range (GXR), NE China, and uses these data to constrain the late Mesozoic tectonic evolution of the GXR. The zircons from these granitoids are magmatic, as indicated by their appearances during cathodoluminescence imaging and high Th/U ratios (0.21–2.35). Zircon U Pb dating indicates that the granitoids formed during the Late Jurassic (~161 Ma) and Early Cretaceous (~132 Ma). The Late Jurassic granitoids (LJG) are dominantly monzogranites with high SiO 2 and Na 2 O + K 2 O contents, and low MgO and FeO T contents. They are metaluminous, enriched in the light rare-earth elements (LREE) and the large-ion lithophile elements (LILE), depleted in the heavy REE (HREE) and high-field-strength elements (HFSE; e.g., Nb, Ta, Ti, and P), and have an adakitic affinity. The zircons from these monzogranites yield ε Hf (t) values of +5.7 to +8.2 and two-stage model ages (T DM2 ) of 749–618 Ma. These results indicate that the primary magma for the Late Jurassic granites was originated from partial melting of a thickened lower-crustal source. The Early Cretaceous granitoids are dominantly metaluminous to peraluminous porphyritic granites with higher HREE contents than the Late Jurassic monzogranites. They display negative Eu anomalies and have ε Hf (t) values of +3.1 to +9.0 with corresponding T DM2 ages of 877–553 Ma, suggesting they formed from magmas generated by partial melting of juvenile lower-crustal material. Combining these data with the geochemistry of coeval volcanic rocks within the GXR, we infer that the northern GXR records a late Mesozoic transition from compression to extension. The compression was most likely related to the Middle Jurassic closure of the Mongol–Okhotsk Ocean, whereas the extension was related to delamination of a thickened region of the lithosphere and/or subduction of the Paleo-Pacific Plate beneath Eurasia. [ABSTRACT FROM AUTHOR]

The electrical conductivity of granitic rocks (granitoids) is crucial to understand the rock composition, physiochemical state and structure of the crust. However, it is not clear how the conductivity of granitoids is affected by the incorporated water in major minerals and hydrous accessory minerals. Here, we measured the electrical conductivity of two natural granites and two synthetic aggregates compositionally similar to the granites at temperatures of 573–1273 K and pressures of either ambient pressure or 1 GPa. No mineral preferred orientation was observed for the natural samples. The hydrous accessory minerals in the samples, including muscovite, biotite and amphibole, start to dehydrate at about 700 K at ambient pressure, but barely affect the bulk conductivity. The increase in conductivity of granite by more than half orders of magnitude at 1273 K and 1GPa indicated the onset of melting due to the dehydration of biotite. The conductivities of synthetic aggregates are higher than the granite samples, suggesting that the structural water in feldspars could influence, to a moderate degree, the conductivity of granite. We combined the effect of modal composition and structural water on the conductivity of granite and derived a maximal electrical conductivity of a granitoid at different geological settings. The maximal conductivity can be 0.004 ± 0.0001 S/m at 60 km under orogens, over one order of magnitude higher than a cratonic crust. The maximal conductivity provides an upper limit for interpreting the electrical anomalies in the crust. • Hydrous minerals cannot affect on the granite conductivity significantly until an interconnected melt system is formed. • The structural water in feldspars moderately affect the conductivity of granite. • The maximal conductivity of a granitoid provides an upper limit for interpreting the geoelectric profile under the granitic crust. [ABSTRACT FROM AUTHOR]

The Eastern Pontides Orogenic Belt offers critical clues on the origin of Early Cenozoic continental arc magmatism in the Alpine-Himalayan system. Systematic geological, geochemical and chronological studies indicate that there are three subgroups among the Early Cenozoic intrusions in the Eastern Pontides Orogenic Belt - Late Paleocene-Early Eocene adakitic intermediate-felsic intrusions, Eocene mafic intrusions, and Eocene non-adakitic granitoid intrusions. Here we focus on the petrology and geodynamic setting of the Eocene non-adakitic granitoid intrusions that are well exposed in a belt between the Thanetian-Ypresian adakitic intrusions in the south and the Lutetian gabbroic intrusions in the north. We also present data on enclaves and surrounding Eocene volcanics. The studied intrusions can be grouped into two main categories, based on their field and petrographical characteristics: granodiorite and monzodiorite-dominated and syenite-dominated bodies. They can be further subdivided into four groups of differing K 2 O content: low-K 2 O (Çevrepınar, Kaletaş, Sarıçiçek and Üzengili), mixed (Sorkunlu, Kozluk and Tamdere), and high-K 2 O (Dölek, Meşebaşı, Çakırbağ and Arslandede) rocks are granodioritic and monzodioritic, whereas shoshonitic (Kösedağ, Meydanlı and Bademli) bodies are syenitic. Zircon U-Pb age determinations reveal that these granitoids were emplaced into crustal rocks of the Eastern Pontides Orogenic Belt between 47 and 42 Ma, in Lutetian time, simultaneously with the gabbroic intrusions in the north. Mineral compositions and P-T calculations are consistent with the interpretation that crustal melting or magma storage started at mid-crustal depth (~ 25 km), with a magma system that subsequently extended to shallow levels (< 4 km). The studied granitoids, enclaves and volcanics exhibit geochemical signatures typical of subduction-related arc magmas, however, the shoshonitic intrusions are younger than most of the other Lutetian intrusions, and indicate a temporal change in arc magmatism. The Sr-Nd-Pb isotopic data indicate that the Lutetian rocks are mixtures of three or four end-member compositions. Considering all geological, geochemical and chronological data, we conclude that the Early Cenozoic magmatism was generated by slab window processes related to ridge subduction in a south-dipping subduction zone below the Eastern Pontides Orogenic Belt. [ABSTRACT FROM AUTHOR]

Understanding the pre-Cenozoic geotectonic framework along the Japan Sea coast in southwest Japan is critical in clarifying the relationship between oceanic subduction-related and collision-related geotectonic belts along the continental margin of East Asia. Although a thick Neogene-Quaternary volcanic-sedimentary cover often conceals the pre-Cenozoic units, the Western Honshu is one of the pivotal regions especially the Mizoguchi gneiss (high-grade gneisses up to amphibolite facies with Rb-Sr isochron age of 185 Ma) exposed near Mt. Daisen in western Tottori prefecture. This unit, together with a neighboring 199 Ma granitoid, was previously correlated with the Hida gneiss in Central Japan, located nearly 250 km to the east. The present study examines this interpretation using zircon U-Pb geochronology. Ages of three gneissose rocks of the Mizoguchi gneiss reveals that the protolith is composed of and represented by granitoid, accretionary complex, and/or high pressure/low temperature (HP/LT) type metamorphosed units. In terms of protolith rock type and zircon age spectra, the Mizoguchi gneiss is different from the Hida gneiss that is interpreted to have been derived from sedimentary rocks/volcanics with continental shelf, and also from the Oki gneiss characterized by its preservation of abundant Precambrian detrital zircon grains. The high-grade metamorphism of the Mizoguchi gneiss is interpreted to have occurred after middle Jurassic as constrained by the youngest detrital grain. The protolith of the Mizoguchi gneiss belongs to the Suo belt (Jurassic HP/LT type metamorphosed accretionary complex) in southwest Japan; however, the unit is interpreted to have been metamorphosed by a Jurassic thermal event, which overlaps that of the Jurassic felsic magmatism in the Hida belt (the Funatsu episode). The Mizoguchi gneiss in western Honshu is unique, because it marks the northernmost or the most proximal occurrence of Phanerozoic subduction-accretion complex in Southwest Japan, clearly on the south of non-accretionary Oki and Hida belts. [ABSTRACT FROM AUTHOR]

We investigated the relationships between fabric, seismic and magnetic anisotropy on lithotypes representative of a continental crust exposed in the Serre Massif (Southern Italy). In particular, from five granitoids and one metagabbro, cubes were cut according to the fabric elements and seismic properties up to 400 MPa confining pressure were measured with a triaxial multi-anvil apparatus; we also calculated the elastic properties based on the mineral content and composition. In granitoids, measured average compressional wave velocity (Vp) of the fracture-free aggregate at 400 MPa is 6.2 km/s, whereas average shear wave velocity (Vs) is 3.6 km/s, with Poisson's ratio ranging from 0.240 to 0.257, related to the modal proportions of quartz. In metagabbro, average Vp and Vs at 400 MPa are 6.9 km/s and 3.7 km/s, respectively. Results showed that intrinsic velocity distribution, after microcracks closure, depends on progressive alignment of anisotropic minerals such as biotite, amphibole and pyroxene, with maxima velocities localized within the foliation plane. Mean magnetic susceptibility, K m , of the granitic rocks is < 300 × 10 − 6 SI units, indicating that paramagnetic minerals such as biotite and amphibole control the intensity of magnetic anisotropy. Comparison of seismic and magnetic anisotropies highlighted the different role of constituting minerals over the petrophysical properties. Moreover, a positive correlation between seismic and magnetic anisotropy has been recognized, indicating that biotite and amphibole contribute to the petrophysical and textural anisotropy in the middle crust. Conversely, in metagabbro, the anisotropy of magnetic susceptibility (AMS) is controlled by magnetite and pyrrhotite although these form < 10% of the rock, which dominantly comprises paramagnetic minerals such as biotite and orthopyroxene. Unlike granitoids, in metagabbro the petrophysical properties are controlled by the paramagnetic minerals, while the magnetic anisotropy is controlled by the ferromagnetic minerals. Results yielded useful constraints for the comprehension of the petrophysical behavior of the continental crust. [ABSTRACT FROM AUTHOR]

Teofilândia granitoids are representative of the Paleoproterozoic plutonic rocks, which intruded the Serrinha block, an Archean crustal fragment of the Sao Francisco Craton (Bahia, Brazil). Three plutons were emplaced, the Teofilândia granodiorite, the Barrocas trondhjemite and the Santa Rosa granite, respectively dated at 2130, 2127 and 2073 Ma. The two first plutons are calc-alkaline rocks following a trondhjemitic trend. They resemble Archean TTGs (tonalites-trondhjemites-granodiorites) by their major and trace element compositions and especially by their fractionated REE patterns, with very low HREE contents. These juvenile magmas resulted from partial melting of a young mafic protolith, likely represented by the nearby Rio Itapicuru greenstone belt. Barrocas trondhjemite and Teofilândia granodiorite derive from similar sources, possibly at different depths and with a different degree of melting. The rocks were deformed at high temperature during the Trans-Amazonian collision and are therefore pre-collisional and ascribed to a subduction stage. The younger Santa Rosa pluton is a small, syn-to post-collisional granite that derived from anatexis of the Archean crust. It is representative of a second, volumetrically minor, plutonic episode of potassic, shoshonitic or alkaline affinities. The large amount of 2.1 Ga granitoids emplaced in Brazil as well as in the West African craton, suggests that, at that time, a global event of possible mantle origin was responsible for the intense magmatic activity that involved both crustal accretion and crustal reworking in many places of the world. [ABSTRACT FROM AUTHOR]

Granitic rocks ( sensu lato ) are major constituents of upper continental crust. Recent reviews reveal that the average composition of Phanerozoic upper continental crust is granodioritic. Although oceanic arcs are regarded as a site producing continental crust material in an oceanic setting, intermediate to felsic igneous rocks occurring in modern oceanic arcs are dominantly tonalitic to trondhjemitic in composition and have lower incompatible element contents than the average upper continental crust. Therefore, juvenile oceanic arcs require additional processes in order to get transformed into mature continental crust enriched in incompatible elements. Neogene granitoid plutons are widely exposed in the Izu Collision Zone in central Japan, where the northern end of the Izu–Bonin–Mariana (IBM) arc (juvenile oceanic arc) has been colliding with the Honshu arc (mature island arc) since Middle Miocene. The plutons in this area are composed of various types of granitoids ranging from tonalite to trondhjemite, granodiorite, monzogranite and granite. Three main granitoid plutons are distributed in this area: Tanzawa plutonic complex, Kofu granitic complex, and Kaikomagatake granitoid pluton. Tanzawa plutonic complex is dominantly composed of tonalite and trondhjemite and characterized by low concentration of incompatible elements and shows geochemical similarity with modern juvenile oceanic arcs. In contrast, Kofu granitic complex and Kaikomagatake granitoid pluton consists mainly of granodiorite, monzogranite and granite and their incompatible element abundances are comparable to the average upper continental crust. Previous petrogenetic studies on these plutons suggested that (1) the Tanzawa plutonic complex formed by lower crustal anatexis of juvenile basaltic rocks occurring in the IBM arc, (2) the Kofu granitic complex formed by anatexis of ‘hybrid lower crust’ comprising of both basaltic rocks of the IBM arc and metasedimentary rocks of the Honshu arc, and (3) the Kaikomagatake granitoid pluton formed by anatexis of ‘hybrid lower crust’ consisting of K-rich rear-arc crust of the IBM arc and metasedimentary rocks of the Honshu arc. These studies collectively suggest that the chemical diversity within the Izu Collision Zone granitoid plutons reflects the chemical variation of basaltic sources (i.e., across-arc chemical variation in the IBM arc) as well as variable contribution of the metasedimentary component in the source region. The petrogenetic models of the Izu Collision Zone granitoid plutons suggest that collision with another mature arc/continent, hybrid lower crust formation and subsequent hybrid source anatexis are required for juvenile oceanic arcs to produce granitoid magmas with enriched compositions. The Izu Collision Zone granitoid plutons provide an exceptional example of the collision-induced transformation from a juvenile oceanic arc to the mature continental crust. [ABSTRACT FROM AUTHOR]

This study investigates strain distribution in granitoid rocks formerly in the middle crust in the Central Aar massif, Switzerland and places the deformation behavior in the tectonic framework of the Alpine orogeny. Strain is heterogeneously distributed in terms of strain partitioning forming several hundreds of closely spaced shear zones (SZ) (>80 SZ/km with SZ thicknesses <10 cm; about 10 SZ/km with SZ thicknesses of 0.5–10 m) separating 3D bodies of low to moderate background strain. Both the degree of background-strain intensity as well as the number of shear zones increases from granitic to granodioritic host rocks and is controlled by primary variations in the mica content between 10 and 15 vol% (granodiorite) and <8 vol% (granite). Shear zones evolved from ductile shearing in granodiorites, whereas they often nucleated from fractures in the stronger granites. The majority of the steep shear zones preferentially accommodated upward motion by the southern block leading to an increase in peak metamorphic conditions from 250 °C in the North to 450 °C in the South of the Aar massif. The shear zones initiated at about 18–20 km depths during a stage of crustal thickening (Handegg phase). Subsequent deformation reactivated some shear zones with a gradual transition from reverse dip-slip over oblique-slip to strike-slip shear zones under local transpressional conditions (Oberaar phase). [ABSTRACT FROM AUTHOR]

Anisotropy of Magnetic Susceptibility (AMS) data are presented from the Koppal Granitoid (Dharwar Craton, South India) that has U-Pb zircon age of 2528 ± 9 Ma. The magnetic fabric is oriented in NNE-SSW direction. This is parallel to the planar structures that developed during regional D 3 deformation, but oblique to the NNW-SSE oriented magnetic foliation as well as field foliation (D 1 /D 2 deformation) recorded in the country rock Peninsular Gneiss. Variation in the intensity of fabric within the granitoid is mapped. It is inferred that the emplacement of Koppal Granitoid took place by ballooning and fabric development within the pluton was syntectonic with regional D 3 . These results are compared with the time-relationship between emplacement/fabric development and regional deformation reported from the Mulgund Granite (2555 ± 6 Ma; U-Pb zircon), which is also located in the Dharwar Craton and is equivalent to the Koppal Granitoid in age. This granite is known to have emplaced syntectonically with regional D 1 /D 2 deformation, and is thus not related to the same deformation event as the Koppal Granitoid, despite their similar absolute ages. It is argued that in the study area, D 3 is ≤2537 Ma, while D 1 /D 2 is ≥2549 Ma in age. Thus, this study highlights the use of AMS in (a) deciphering the relative timing of regional deformation and emplacement of granitoids of equivalent age and (b) constraining the timing of regional superposed deformation events. [ABSTRACT FROM AUTHOR]

The tectonic framework of the North China Craton (NCC) during late Archean to early Paleoproterozoic (circa 2.5 Ga) is still lacking comprehensive understanding due to subsequent strong deformation and metamorphic overprinting events. Circa 2.5 Ga magmatic and metamorphic activities are widely spread throughout the NCC, which can be used as an efficient target to better understand the tectonic evolution at this period. In this study, based on a detailed field, structural, geochemical, geochronological and Sm–Nd isotopic study, we focus our work on the Haozhuang granitoids in the Zanhuang Massif located at the eastern margin of the Central Orogenic Belt of the NCC. The granitoids mainly include undeformed pegmatite and granodiorite. One pegmatite and two granodiorite samples yield zircon 207 Pb/ 206 Pb ages of 2513 ± 29 Ma, 2511 ± 36 Ma and 2528 ± 18 Ma, respectively. The granodiorites show metaluminous and shoshonitic to high-K calc-alkaline series characteristics with A-type granite affinity. The circa 2.5 Ga granodiorites have highly negative ε Nd (t) values (− 29.22 ~ − 33.12) and T DM model ages between 2671 Ma and 3151 Ma. This work shows clearly, from whole-rock major and trace elements and Sm–Nd isotopic studies, that the Haozhuang granodiorites were derived from partial melting of old and thickened TTG crust rather than mantle sources, and formed in a subduction-related tectonic setting. With geochemical comparison studies to other similar-aged granitic rocks in the Zanhuang Massif, we suggest that these granitic rocks possibly have a certain correlation during the magma evolution. Coupled with our previous geochemical and isotopic studies on circa 2.5 Ga mafic dike swarms, we propose that the similar-aged granitic rocks and mafic dike swarms were produced by an east-dipping subduction polarity reversal event following an arc–continent collision between the Fuping/Wutai island arc and Eastern Block of the NCC above a west-dipping slab. The east-dipping subduction resulted in partial melting of the enriched lithospheric mantle, firstly forming the circa 2.5 Ga mafic dikes inducing the widespread circa 2.5 Ga metamorphism in the Central Orogenic Belt and the Eastern Block, and then the parental magma of these mafic dike swarms heated the old and thickened TTG crust causing the formation of similar-aged granitic rocks at a later stage. [ABSTRACT FROM AUTHOR]

The Mineiro Belt originated by Siderian (2470 to 2330 Ma) to Rhyacian (2250 to 2110 Ma) arcs amalgamated to the Neoarchean foreland of the southern margin of the São Francisco Craton, Brazil. The Macuco de Minas metagranitoid is one of the most important plutons related to the Rhyacian Ritápolis arc that developed close to the Siderian crust akin to the older Cassiterita and Resende Costa arcs. We integrate new U-Pb ages, coupled geochemistry and Sr-Nd-Hf isotopes, and thermobarometry data together with compiled information in order to unravel the petrogenesis of the Macuco de Minas metagranitoid and its role in the formation of the Mineiro belt. This pluton is essentially represented by porphyritic granodiorites to monzogranites which exhibit centimetric microcline phenocrysts immersed in a medium-grained matrix mainly composed of quartz, oligoclase, biotite, and titanite. These rocks exhibit well-preserved mixing and mingling features (homogeneous hybrid rocks, mafic clots, magmatic enclaves, diorite injections with cuspate-lobate shape, and back-veining) suggesting interaction with a dioritic/tonalitic magma, similar to the coeval Rio Grande metadiorite that occurs nearby. The Macuco de Minas (and hybrid) rocks are magnesian, medium- to high-K calc-alkaline, metaluminous to slightly peraluminous, and display a high Ba-Sr signature. These exhibit enrichment in LILE and LREE compared to HFSE and HREE, as well as low Sr87/Sr86 (2.1 Ga) (0.7027 to 0.7037), εNd (2.1 Ga) values from −2 to −7, and εHf (2.1 Ga) values from +3 to −7. The Nd-T DM model ages vary from 2.3 to 2.7 Ga and the zircon Hf ones from 2.38 to 2.77 Ga. The Macuco de Minas sample yielded a LA-ICP-MS zircon U-Pb crystallisation age of 2144 ± 16 Ma, and metamorphic age (titanite) of 2071 ± 42 Ma. The crystallisation age is similar to the 2140 ± 17 Ma Rio Grande metadiorite. However, the latter contains inherited grains as old as 2200 ± 19 Ma and 2263 ± 21 Ma, not observed in the Macuco de Minas pluton. The bulk geochemical and isotopic signature of the studied granitoids point to a mantle source with a subordinated contribution of juvenile Siderian rocks of the Cassiterita and Resende Costa arcs and subducted sediments from the Archean rocks of the São Francisco Craton. From a tectonic point of view, the Macuco de Minas and Rio Grande plutons are compatible with the second stage of the Ritápolis arc development, to date the youngest episode of arc generation recognised in the Mineiro belt. • Dioritic magma injections into the Macuco de Minas chamber resulted in hybridisation. • The Macuco de Minas rocks are derived from a mantle source with crustal contribution. • The Macuco de Minas pluton developed during the second stage of the Ritápolis arc. • The accretion of the Mineiro belt during the Minas-Bahia orogeny occurred at 2.07 Ga. [ABSTRACT FROM AUTHOR]

The crust of the Paleoproterozoic West African Craton in northern Ghana is dominantly made of Tonalite-Trondhjemite-Granodiorite (TTG) suites, low-K to high-K calc-alkaline granites, with minor LILE-enriched diorites, and chemically related lavas. Results of zircon U-Pb dating indicate that all these different rock types were formed together over a prolonged period of ca. 100 Ma, between 2.21 and 2.11 Ga. Zircon Hf isotope compositions of five samples are supra-chondritic (εHf t from +1 to +6) indicating that the granitoids derive from the reworking of juvenile crustal components as old as 2.60 Ga. Geochemical data show that the TTGs were derived from the reworking of a low-K mafic crust, while biotite granites formed by the reworking of older felsic crustal rocks, and diorites derived from the melting of LILE-enriched mantle sources. The combined datasets support a three-step model for the formation of the crust of the West African craton in northern Ghana: (1) a juvenile, mafic proto-crust was extracted from the depleted mantle between 2.60 and 2.30 Ga, in an oceanic environment remote from any pre-existing continental nucleus; (2) the mafic proto-crust was reworked in several primitive magmatic arcs or in accreted oceanic plateaux. Crustal reworking initially produced minor felsic magmatism between 2.35 and 2.21 Ga, followed by the 2.21–2.15 Ga emplacement of low- to medium-P TTG and K-rich calc-alkaline granitoid suites, and was coeval with the formation of an enriched mantle source. (3) Various proto-continental terranes collided during the Eburnean orogeny between 2.14 and 2.11 Ga, triggering intense reworking of the composite crust and mantle reservoirs formed in the previous two steps, i.e. remnants of the juvenile mafic crust, older TTGs and biotite granites, and previously enriched mantle sources. The emplacement of high-P TTGs, granites and LILE-enriched diorites resulted from lower crustal heating in response to the delamination of the lower crust and lithospheric mantle. The Eburnean collision therefore marks the final stages of a 200–500 Ma long period of juvenile continental crust formation and stabilisation. The datasets further reveal that the Paleoproterozoic West African Craton comprises a minimum of two distinct crustal blocks, with north-western Ghana lying at their interface. [ABSTRACT FROM AUTHOR]

The Taihua metamorphic complex exposes in the southern Trans-North China Orogen (TNCO) and records at least three episodes of magmatism. The Shanxian TTG gneisses obtained at 2.54–2.48 Ga have high SiO 2 , variable Mg# with high (La/Yb) N and Sr/Y ratios (15.08–93.26 with average of 37.31 and 7.33–115.05 with average of 49.59, respectively). They show negative Nb and Ta but positive Zr and Hf anomalies with low Nb/Ta and Gd/Yb, and high Zr/Hf and Zr/Sm ratios (4.97–18.8, 1.92–6.37, 23.71–50.26, and 29.18–75.23, respectively), and have positive ε Hf (t) values (+1.7 to +7.9) and ε Nd (t) values (+0.72 to +2.55), indicating that they were possibly produced by partial melting of lower crust derived from metasomatized lithospheric mantle with the residue of minor garnet. The Sihe granitic gneisses recorded at 2.35–2.30 Ga are enriched in silica, Al 2 O 3 contents (13.59–15.33), K 2 O/Na 2 O ratios (1.13–1.7), defined as high-Al TTG. They exhibit high Sr/Y, Zr/Sm and Zr/Hf ratios and low Nb/Ta and Gd/Yb ratios (44.71–83.09, 47.79–62.58, 36.05–37.43, 12.04–16.36, and 2.95–3.68, respectively) with negative Eu anomaly. Combined with Hf and Nd isotopes (−2.5 to +4.7 and −0.74 to +0.36), the Sihe granitic gneiss was possibly generated from partial melting of lower crust with minor ancient material contributions, leaving residual amphibole and minor garnet in the source. The Muce monzonitic gneisses emplaced at 2.17–2.16 Ga have high Mg#, Ni and Cr contents, constant Sr/Y and (La/Yb) N (42.39–50.33, 19.8–41.4, 33.6–74.2, 31.32–34.14, and 15.32–16.7, respectively), with relatively low and constant Dy/Yb ratio (1.82–1.85). Together with Hf and Nd isotopes (−6.5 to −0.9 and −2.07 to −2.86), the Muce monzonitic gneisses might be derived from partial melting of Neoarchean pre-existing crustal materials, possibly in an arc setting. It is therefore found that four episodes of crustal growth and/or reworking in the southern segment of the TNCO have occurred at 2.85–2.72 Ga, 2.57–2.48 Ga, 2.35–2.30 Ga and 2.2–2.0 Ga, respectively, likely to connect with the subduction–collision between the Eastern and Western Blocks along the TNCO in the North China Craton. [ABSTRACT FROM AUTHOR]

Ourilândia do Norte rocks are located near Rio Maria-Carajás domains boundary and are associated to Rio Maria Mesoarchean sanukitoid. Two groups were defined on the basis of geochemistry: (i) quartz-monzodiorites and granitoids (tonalite and granodiorite) which match to the sanukitoid (stricto sensu); and (ii) enclaves and (quartz) diorites that do not. Despite this, these rocks are spatially and temporally associated and they develop microstructures under three dynamic recrystallization regimes: (i) bulging recrystallization (300–700 °C); (ii) subgrain rotation recrystallization (<700 °C); (iii) grain boundary migration recrystallization (>600 °C). Furthermore, they belong to medium to high potassium calc-alkaline series, being magnesian and mainly metaluminous. The Mg#, Cr and Ni abundances point out an ultramafic mantle source. Variation of LILE, Nb/Y, (La/Yb) N and Sr/Y contents indicate a metasomatized mantle by two independent agents, namely TTG-like melt and aqueous fluids, at different depths. In this way, quartz-monzodiorites and granitoids were derived from fractionation of a mafic magma, whose source is a TTG-metasomatized mantle, at greater depths, while enclaves and (quartz) diorites were generated from a fluid-metasomatized mantle, at shallower depths. The close spatial and temporal association of rocks with sanukitoid (quartz-monzodiorites and granitoids) and BADR (enclaves and (quartz) diorites) signature suggest that Ourilândia do Norte granitoids were generated in close spatial and temporal association with active subduction. [ABSTRACT FROM AUTHOR]

This study investigates the origin of the different Mesoarchean granitoids of the Ourilândia plutonic complex from the Carajás province (northern Brazil), as well as their geodynamic significance. This complex integrates interdigitated plutons of 2.88 Ga biotite granite (BG) and sanukitoid (SNK), with subordinate high-K calc-alkaline (HKCA) granodiorite-granite and tonalite-trondhjemite-granodiorite (TTG). (i) The BG is represented by equigranular monzogranite, which can be formed by 18% melting from TGG-type trondhjemite. (ii) The SNKs are composed of granodiorites (equigranular, heterogranular and porphyritic), with subordinate tonalite, quartz monzodiorite and quartz diorite, all with mafic microgranular enclaves. The different SNK-type granitoids and quartz monzodiorite were generated by 18–33% melting from mantle previously enriched by 20–40% TTG-type melt in the garnet stability zone. On the other hand, quartz diorite and mafic enclaves formed from fluid-metasomatized mantle at lower depths. (iii) The HKCA granodiorite-granite group (also called high-Ti SNK) is composed of porphyritic granodiorite and heterogranular monzogranite. The granodiorite can be formed by 30% melting from mantle enriched by 40% TTG-type melt under oxidizing conditions, with the participation of a component enriched in HFSEs. The heterogranular monzogranite is a hybridization product between 60% metasomatized mantle-derived magmas (high-Ti granodiorite) and 40% crust-derived magmas (equigranular monzogranite). (iv) The TTG-type tonalitic xenolith and porphyritic trondhjemite were formed by partial melting of hydrous metabasalts; however, the trondhjemite petrogenesis involves hybridization with enriched mantle-derived magmas. The BG and SNK provided coeval crystallization ages of 2881 ± 10 Ma and 2886 ± 14 Ma, respectively. In addition, in the BG, three more crystal populations were identified with ages of 3040 ± 40 Ma, 2976 ± 09 Ma and 2934 ± 21 Ma. The first two are interpreted as xenocrystals, and the latter is interpreted as inherited crystals. ∼2.88 Ga represents the main period of crustal growth in the Ourilândia do Norte area, with emplacement of juvenile magmas and crustal reworking. The studied rocks were formed in a post-subduction collision setting with coeval mantle and crust-derived magma generation over a short time span (∼2.88 Ga), where shear zones conditioned the ascent and emplacement of the Ourilândia magmas. [Display omitted] • Mesoarchean plutonic complex from Carajás province was formed by mantle and crust-derived magmas. • ∼2.88 Ga is the main period of crustal growth and reworking in the Ourilândia do Norte area. • The ascent, emplacement and interaction of the Ourilândia magmas were conditioned by shear zones. • Syntectonic magmas emplaced in collision setting under transpressive deformation regime. • Secondary mineral paragenesis was developed by hydration reactions under cooling conditions. [ABSTRACT FROM AUTHOR]

The ‘Bongo-type’ granitoids intrude the northern portion (where it cross cuts the Tarkwaian), central and south-central portions of the Bole–Nangodi greenstone belt in Ghana. The non-foliated, porphyritic granitoids are characterised by microcline (5–18 mm), often set in a medium to fine grained matrix of quartz and plagioclase, contains granular quartz and show incipient development of mymerkites under thin section. The major mafic phases are a brownish-green variety of hornblende ± biotite, with sphene, epidote and apatite occurring as accessory minerals. The pink looking ‘Bongo-type’ granitoids are classified as granites with subordinate granodiorites and quartz monzonites. Whole-rock geochemical analyses show that the granitoids are magnesian and metaluminous to weakly peraluminous. On the basis of their Th–Co–K 2 O and SiO 2 contents, the granitoids classified as high-K calc-alkaline and shoshonite series rocks. They show enriched LILE trends, decoupled LILE–HFSE patterns, negative Ta–Nb anomaly, pronounced negative Ti anomaly and variable positive and negative Sr anomalies. The K-rich granitoids from the middle and south-central portions of the Bole–Nangodi belt show the lowest concentrations of LILE and some HFSE with the most prominent negative Ti and Si anomalies. The ‘Bongo-type’ granitoids show I-type characteristics. Based on Ba–U–Th concentrations, they are interpreted to have had some interaction with crustal materials or some influence of subducted sediments. The granitoids unequivocally show subduction-related signatures and mimic high silica adakites (HSA). They show evidence of being emplaced in a volcanic arc geotectonic environment. Their geochemical similarities to A-type granitoids, however, suggest an arc–back-arc tectonic setting. [ABSTRACT FROM AUTHOR]

Late Cenozoic granitoids are widespread in a 1600 km long belt forming the Western and Northern Sulawesi tectono-magmatic provinces. They can be divided into three rock series: shoshonitic (HK), high-K felsic calc-alkaline (CAK), and normal calc-alkaline to tholeiitic (CA-TH). Representative samples collected from eleven plutons, which were subjected to petrography, major element, trace element, Sr, Nd, Pb isotope and whole-rock δ 18 O analyses, are all I-type and metaluminous to weakly peraluminous. The occurrence of the two K-rich series is restricted to Western Sulawesi, where they formed in an extensional, post-subduction tectonic setting with astenospheric upwelling providing thermal perturbation and adiabatic decompression. Two parental magma sources are proposed: enriched mantle or lower crustal equivalent for HK magmas, and Triassic igneous rocks in a Gondwana-derived fragment thrust beneath the cental and northern parts of Western Sulawesi for CAK magmas. The latter interpretation is based on striking similarities in radiogenic isotope and trace element signatures. CA-TH granitoids are found mostly in Northern Sulawesi. Partial melting of lower-middle crust amphibolites in an active subduction environment is the proposed origin of these rocks. Fractional crystallization and crustal contamination have played a significant role in magma petrogenesis, particularly in the case of the HK and CAK series. Contamination by organic carbon-bearing sedimentary rocks of the HK and CAK granitoids in the central part of Western Sulawesi is suggested by their ilmenite-series (reduced) character. The CAK granitoids further to the north and CA-TH granitoids in Northern Sulawesi are typical magnetite-series (oxidized). This may explain differences in mineralization styles in the two regions. [ABSTRACT FROM AUTHOR]

The Ordovician Faja Eruptiva de la Puna Oriental is a magmatic, predominantly intrusive belt in the Puna of northwestern Argentina with a N-S extension of ca. 400 km. Scarce isotope geochemical ages and biostratigraphic data on some of the folded Faja Eruptiva country rocks assign the magmatism either to the Lower and lower Middle Ordovician, or to the latest Ordovician. Interpretations of origin and tectonic framework of the Faja Eruptiva are controversial and vary between arc, back-arc and collisional-orogenic settings. We present high-resolution La-ICP-MS U–Pb age and Hf isotope data on zircons from 10 plutonic samples covering the magmatic belt along a length of 200 km in the northern Argentinian Puna. The xenocrystic and magmatic zircon age data have a wide spread between 2700 Ma and 440 Ma. Concordia and weighted mean age data document protracted magmatism in two phases between 480 and 460 Ma, and between 453 and 444 Ma, and constrain the time of the last intrusions at 444 ± 3 Ma and at 445 ± 2 Ma thus defining this last and main phase of intrusion at 444 Ma. εHf(t) values define a main vertical trend centered at 500 Ma with εHf(t) values between + 3 and − 16 indicating significant mixing of juvenile early Paleozoic melts with Paleoproterozoic crustal components. A second trend is formed by zircons with ages between 1.1 Ga and c. 500 Ma and predominantly positive εHf values between + 8 and − 3 and originates in juvenile mantle compositions between 1.6 and 1.1 Ga. The spread of the zircon and Hf data document that the Faja Eruptiva intrusives have experienced large-scale contamination by the hosting crustal basement. It follows that the basement of the Puna is formed either by the upper Proterozoic-lower Cambrian Puncoviscana Formation as an erosional product of the Proterozoic orogenic belts of SW Amazonia or that the Puna including its Puncoviscana basement is underlain by a crust shaped by these orogenies. The main intrusive event at 444 Ma has been linked to the Oclóyic orogeny in the Late Ordovician. The plutons intruded very likely in a sinistral strike-slip regime after the main folding phase of the Oclóyic orogeny had deformed the Ordovician sedimentary country rocks. [ABSTRACT FROM AUTHOR]

Granitoids are widely distributed in Jinchuan at the southwestern margin of the North China plate, which is also an important area of mineral deposits. The research subject of this article are two Paleozoic granitoids, a cataclastic syenogranite and a granodiorite porphyry. This study presents whole rock geochemistry and zircon U–Pb–Hf isotope data for the two granitoids to determine their petrogenesis, source characteristics and tectonic significance. The cataclastic syenogranite is characterized by metaluminous composition with high potassium, and La N /Yb N from 39 to 48. The composition with strong negative Eu anomalies and Zircon saturation temperatures ( T Zr ) from 947 to 1072 °C classify this intrusion as an A-type granite. The granodiorite porphyry is metaluminous with high sodium, sub-alkaline, La N /Yb N ratios from 27 to 32. These I-type intrusions have no Eu anomalies and T Zr ranges from 818 to 845 °C. Both the cataclastic syenogranite and granodiorite porphyry show enrichment of LREE and LILE and depletion of HREE and HFSE, except Hf and Zr. Using single zircon LA-ICP-MS U–Pb dating, the emplacement age of the cataclastic syenogranite and granodiorite porphyry are determined at 433.4 ± 3.7 Ma and 361.7 ± 4.6 Ma, respectively. Zircons from the cataclastic syenogranits have uniform negative ε Hf ( t ) values (−11 ± 0.5 to −9 ± 0.5), implying the involvement of an old Palaeoproterozoic crustal source in magma genesis. The zircons from the granodiorite porphyry have ε Hf ( t ) values that range from −8 ± 1.0 to +10 ± 0.6, suggesting heterogeneous source materials involving both juvenile and ancient crust reworked crustal components. Based on the geological significance of granites at the southwestern margin of the North China plate, the closure of the North Qilian Ocean occurred at ∼444 Ma. Geochemical features suggest that the cataclastic syenogranite and granodiorite porphyry formed in an intraplate extensional and compressional setting, respectively. Hence after a period of extensional post-collisional intraplate evolution, strong compressive forces affected the area. [ABSTRACT FROM AUTHOR]

The basement of sedimentary basins is often entirely covered by a potentially multi-stage basin fill and therefore removed from direct observation and sampling. Melts intruding through the basin stratigraphy at a subsequent stage in the geological evolution of a region may assimilate significant volumes of country rocks. This component may be preserved in the intrusive body either as xenoliths or it may be reflected only by the age spectrum of incorporated zircons. Here we present the case of an Ordovician calc-alkaline intrusive belt in NW Argentina named the “Faja Eruptiva de la Puna Oriental” (Faja Eruptiva), which in the course of intrusion sampled the unexposed and unknown basement of the Ordovician basin in this region, and parts of the basin stratigraphy. We present new LA–ICP-MS U–Pb ages on zircons from 9 granodiorites and granites of the Faja Eruptiva. The main part of the Faja Eruptiva intruded c. 445 Ma in the Late Ordovician. The zircon ages obtained from the intrusive rocks have a large spread between 2683.5 ± 21.6 and 440.0 ± 4.9 Ma and reflect the underlying crust and may be interpreted in several ways. The inherited zircons may have been derived from the oldest known unit in the region, the thick siliciclastic turbidite successions of the upper Neoproterozoic–lower Cambrian Puncoviscana Formation, which is inferred to represent the basement of the NW Argentina. The basement to the Puncoviscana Formation is not known. Alternatively, the inherited zircons may reflect the geochronological structure of the entire unexposed Early Paleozoic crust underlying this region of which the Puncoviscana Formation was only one component. This crust likely contained rocks pertaining to and detritus derived from earlier orogenic cycles of the southwestern Amazonia craton, including sources of Early Meso- and Paleoproterozoic age. Detritus derived, in turn, from the Faja Eruptiva intrusive belt reflects the origin of the granitoids as well as the inherited geochronological and isotope geochemical structure of either the basement and/or distant sources having supplied material to the basement rocks. If unrecognized, sediment formed from such granitoid sources may erroneously be used to infer the exposure of, and direct detrital contributions from, a variety of older source rocks in fact not directly involved in the studied source–sink system. [ABSTRACT FROM AUTHOR]

In the latter stages of exhumation processes, rocks undergo weathering. Weathering halos have been described in the vicinity of structures such as faults, veins or dykes, with a lateral size gradually narrowing with depth, symmetrically around the structures. In this paper, we describe the geophysical characterisation of such alteration patterns on two granitoid outcrops of the Catalan Coastal Ranges (Spain), each of which is affected by one major fault, as well as minor faults and fractures. Seismic, electric and ground penetrating radar surveys were carried out to map the spatial distribution of P-wave velocity, electrical resistivity and to identify reflectors of electromagnetic waves. The analysis of this multi-method and complementary dataset revealed that, at shallow depth, geophysical properties of the materials are compartmentalised and asymmetric with respect to major and subsidiary faults affecting the rock mass. This compartmentalisation and asymmetry both tend to attenuate with depth, whereas the effect of weathering is more symmetric with respect to the major structure of the outcrops. We interpret such compartmentalisation as resulting from the role of hydraulic and mechanical boundaries played by subsidiary faults, which tend to govern both the chemical and physical alterations involved in weathering. Thus, the smoothly narrowing halo model is not always accurate, as weathering halos can be strongly asymmetrical and present highly irregular contours delimiting sharp contrasts of geophysical properties. These results should be considered when investigating and modelling fluid storage and transfer in top crystalline rock settings for groundwater applications, hydrocarbon or geothermal reservoirs, as well as mineral deposits. [ABSTRACT FROM AUTHOR]

This paper highlights a case of extensive development of saprolith from granitic bedrock in NW Spain. The weathering front at the study area extends to more than 250 m in depth. The drilling of a railway tunnel (Madrid–Galicia high-speed line) through the bedrock and saprolith resulted in significant technical issues and economic losses. Cross-sections revealing the 3D complexity of saprolith development are mainly based on fieldwork, boreholes, laboratory tests, and the excavation works. Saprock is always observed overlying unweathered igneous bedrock. Two saprolite facies, one clay-rich and the other clay-poor overlie the saprock; the recognition is based on several criteria. These deposits gradually thicken from the boundaries between the granitoid and metasedimentary roof pendants. Factors controlling saprolith development are discussed, and the chemical and mineralogical changes and trends that occur are described. Variations in some geotechnical properties and the loss of quality of the rock masses from an engineering perspective are also quantified. [ABSTRACT FROM AUTHOR]

The structural study of the Saint-Laurent – La Jonquera pluton (Eastern Pyrenees), a Variscan composite laccolithic intrusion emplaced in metasedimentary and gneissic rocks of the Roc de Frausa dome, by means of the anisotropy of magnetic susceptibility (AMS) technique has allowed the determination of the nature and orientation of its magmatic fabrics. The magmatic foliation has a predominant NE–SW strike and the mean lineation is also NE–SW trending with a shallow plunge. A strain gradient is measured so that the tonalites to granodiorites that form the basal parts of the pluton, and are intruded into amphibolite-facies metamorphic rocks, recorded the highest anisotropies, whereas the monzogranites and leucogranites, emplaced into upper crustal, low-grade metamorphic rocks, are weakly deformed. These results point to the synkinematic sequential emplacement of multiple granitoid sheets, from less to more differentiated magmatic stages, during the Late Carboniferous D 2 event characterized by an E–W-trending dextral transpression. The magmatic foliation appears locally disturbed by the effects of two tectonic events. The first of them (D 3 ) produced mylonitization of granitoids along NW–SE retrograding shear zones and open folds in the host Ediacaran metasediments of the Roc de Frausa massif, likely during late Variscan times. Interference between D 2 and D 3 structures was responsible for the dome geometry of the whole Roc de Frausa massif. The second and last perturbation consisted of local southward tilting of the granitoids coupled to the Mesozoic–Cenozoic cover during the Alpine. [ABSTRACT FROM AUTHOR]

The Svecofennian domain comprises a c. 800 km by 800 km area in Finland and Sweden, mainly composed of Palaeoproterozoic granitoids, schists and gneisses. In the central part of the domain in western Finland, the Vaasa complex hosts a sequence of high-grade metamorphic rocks and granites formed by crustal anatexis during the culmination of the ∼1.9 Ga Svecofennian orogeny. The Vaasa complex consists of a c. 8000 km 2 granitoid batholith surrounded by diatexitic and metatexitic migmatites as well as metasedimentary rocks. In order to enhance the perception of the crystallisation history, provenance, and maximum sedimentation age of the protoliths involved, nine granitoid-xenolith pairs and a palaeosome-neosome pair were collected from the main body of the Vaasa batholith and surrounding rocks, and zircon from them was U–Pb dated using the LA-MC-ICPMS method. The U–Pb zircon crystallisation ages of the granitoids are 1.88–1.87 Ga, which is in accordance with the few previous results from the Vaasa region, and confirms a relatively swift crystallisation of the granite core throughout the Finnish part of the complex. The samples from the central part of the batholith have younger zircon ages than those from batholith margin. The inherited zircon age distribution pattern of the granitoids resembles that of the metasedimentary xenoliths. Our new comprehensive data, combined with whole-rock geochemistry from previous studies, render an in situ origin of the Vaasa granite probable. The maximum sedimentation age of the supracrustal precursors of the Vaasa complex is 1.92 Ga. Some of the metasedimentary xenoliths from the Vaasa complex host zircon that is coeval with their host granitoids and register incipient melting. Based on these ∼1.88–1.86 Ga zircon grains, the maximum sedimentation age would be deemed too young. Therefore, our data calls for caution when determining maximum sedimentation ages of high-grade metasedimentary rocks. [ABSTRACT FROM AUTHOR]

In order to clarify the early history of Japan, particularly during the Early Paleozoic, pre-Devonian granitoids in the South Kitakami Belt (SKB), NE Japan were dated by U–Pb zircon age by laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Two samples of diorite/tonalite from the Nagasaka area (Shoboji Diorite) and two of mylonitic tonalite from the Isawa area (Isawagawa Tonalite) yielded late Cambrian ages (500–490 Ma) for the primary magmatism. These ages newly identify a ca. 500 Ma (late Cambrian) arc plutonism in central NE Japan, which has not been recognized previously and has the following geological significance. The Cambrian granitoids are the oldest felsic plutonic rocks in NE Japan, which are independent of the previously known ca. 450 Ma (latest Ordovician) Hikami Granite in SKB. The Cambrian granitoids are extremely small in size at present but likely had a much larger distribution primarily, at least 30 km wide and potentially up to 80 km wide in a cross-arc direction. Their southerly extension was recognized in the Hitachi area (ca. 200 km to the south) and in central Kyushu (ca. 1500 km to SW). They likely represent remnants of the same mature arc plutonic belt in Early Paleozoic Japan, which developed in western Panthalassan (paleo-Pacific) margin, as well as the Khanka block in Far East Russia. The extremely small size of the Cambrian granitoids at present can be best explained by intermittent, severe tectonic erosion since the Paleozoic. This Cambrian arc granitoid belt likely developed from Primorye possibly to eastern Cathaysia (South China) via Japan. [ABSTRACT FROM AUTHOR]

Voluminous Late Mesozoic granitoids and the world’s largest Mo deposits occur in the East Qinling. This paper presents the results of Nd–Hf isotopic mapping for the Late Mesozoic granitoids (155–105 Ma) and demonstrates their constraint on the basements and distribution of the Mo deposits in the East Qinling. This isotopic map, made by 98 (21 new and 77 published) whole-rock Nd isotopic and 29 (7 new and 22 published) average zircon Hf isotopic data, shows large variations of whole-rock ε Nd ( t ) values from −22.1 to −1.5, and the correspondingly Nd model ages ( T DM(Nd) ) from 2.83 to 0.79 Ga, and zircon ε Hf ( t ) values from −26.3 to +0.1 and two-stage Hf model ages ( T DM2(Hf) ) from 2.86 to 0.96 Ga. Three regions of variations have been identified from north to south: (a) ε Nd ( t ) values range from −22.1 to −10.9 with T DM(Nd) of 2.82–1.47 Ga, and ε Hf ( t ) values 26.3 to −13.5 with T DM2(Hf) 2.86–2.04 Ga; (b) ε Nd ( t ) values −13.9 to −1.5 with T DM(Nd) 2.02–0.79 Ga, and ε Hf ( t ) values −16.2 to +0.1 with T DM2(Hf) 1.96–0.96 Ga; and (c) ε Nd ( t ) values −6.3 to −4.5 with T DM(Nd) 1.28–1.12 Ga, and ε Hf ( t ) values −1.0 to −0.3 with T DM2(Hf) 1.25–1.22 Ga, respectively. The three regions approximately correspond to the three different terranes, the southern margin of the North China Block (NCB), the North Qinling Belt (NQB) and the South Qinling Belt (SQB), respectively. These demonstrate that the granitoids in the different terranes have distinct sources and their sources change from old to more juvenile from the north (southern margin of the NCB) to the south (SQB). These also reveal the distinct basements for the terranes in Late Mesozoic. The southern margin of the NCB contains widespread Neoarchaean to Paleoproterozoic basement, the NQB comprises Archaean to Neoproterozic basement and the SQB Mesoproterozic to Neoproterozic basement. All these suggest that the three terranes underwent different tectonic evolution and the continental crust of the East Qinling were mainly formed during Archaean to Neoproterozic, different from a typical accretion orogen. The old sources of the granitoids and basements of the terranes constrain the distribution, scale and number of the Mo mineralization and deposits. Mo mineralization is closely related to the small granitic bodies with old continental component sources and Mo deposits are mainly hosted by the terranes with oldest basement. The scale and number of the Mo mineralization and deposits decreased from the southern margin of the NCB to SQB. [ABSTRACT FROM AUTHOR]

The Namaqua Metamorphic Complex is a Mesoproterozoic low-pressure, granulite facies belt along the southern and western margin of the Kaapvaal Craton. The NMC has formed between ~ 1.3 and 1.0 Ga and its central part consists essentially of different types of granitoids intercalated with metapelites and calc-silicate rocks. The granitoids can be subdivided into three major groups: (i) mesocratic granitoids, (ii) leucocratic granitoids and (iii) leucogranites. The high-K, ferroan mesocratic granitoids (54–75 wt% SiO 2 ) have a variable composition ranging from granitic to tonalitic, and contain biotite and/or hornblende or orthopyroxene. They are strongly enriched in REE and LILE, indicating A-type chemical characteristics, and are depleted in Ba, Sr, Eu, Nb, Ta and Ti. The leucocratic granitoids and leucogranites (68–76 wt% SiO 2 ) differ from the other group in having a granitic or slightly syenitic composition containing biotite and/or garnet/sillimanite. They have lower REE and MgO, FeO t , CaO, TiO 2 , MnO concentrations, but higher Na 2 O and K 2 O contents. Compositional variations in mesocratic granitoids indicate their formation by fractional crystallization of a mafic parental magma. Leucocratic granitoids and leucogranites lack such trends, which suggests melting of a felsic crustal source without subsequent further evolution of the generated magmas. The mineralogical and geochemical characteristics of the mesocratic granitoids are consistent magmatic differentiation of a mantle derived, hot (> 900 °C) parental magma. The leucocratic granitoids and leucogranites granites were formed from low-temperature magmas (< 730 °C), generated during fluid-present melting from metasedimentary sources. New U-Pb zircon ages reveal that both magma types were emplaced into the lower crust within a 30–40 million years interval between 1220–1180 Ma. In this time period the crust reached its thermal peak, which led to the formation of the leucocratic granitoids and leucogranites. A prolonged period of relatively high crustal temperatures is followed by a second heat pulse at ~ 1100 Ma, that was intense enough to facilitate zircon growth in the older plutons and it produced a younger granite suite. The crust cools down below amphibolite facies conditions after a further 100 million years. The prolonged high-temperature history is best compatible with steady and long-lasting heat transfer from mantle sources, suggesting a continental back-arc situation as the most likely setting of the NMC in the late Mesoproterozoic. [ABSTRACT FROM AUTHOR]

The paper presents the results of the research, connected with the granulometric and mineralogical compositions of fusible clay raw materials of Krasnoyarsk region - argillic and loose clay varieties. The influence of granitoid and diabase rocks stony additives on the sinterability and strength characteristics of the ceramic materials based on fusible clays is evaluated. It is found that the introduction of sintering additives into the loose fusible clay leads to the significant increase of samples strength – 50-100 MPa, while the introduction of the similar additives in the argillic clay does not influence positively on samples strength. [ABSTRACT FROM AUTHOR]

A combined study of zircon U–Pb ages and Lu–Hf isotopes, whole-rock major-trace elements and Sr–Nd isotopes as well as whole-rock and mineral O isotopes was carried out for Mesozoic granitic intrusions from the Taoshan batholith in the Nanling Range, South China. The results not only place constraints on the origin of granitoids but also provide insights into the effect of melting temperature on granitoid compositions. LA-ICPMS zircon U–Pb dating yields weighted 206 Pb/ 238 U ages of 230 ± 2 Ma for the Caijiang intrusion, 167 ± 2 Ma for the Huangpi intrusion, 152 ± 3 Ma for the Daguzhai intrusion, and 146 ± 3 Ma for the Luobuli intrusion. Relict zircon cores with older Mesozoic to Paleozoic U–Pb ages are present in some samples. These Mesozoic granitoids are weakly to strongly peraluminous with A/CNK ratios of 1.05 to 1.23. They exhibit arc-like trace element distribution patterns, with enrichment of LREE and LILE (e.g., Rb, K, Pb) but depletion of HFSE (e.g., Nb, Ta, Ti). They show high whole-rock initial 87 Sr/ 86 Sr ratios of 0.7101 to 0.7156 and low ε Nd (t) values of − 11.2 to − 8.8 as well as negative zircon ε Hf (t) values of − 14.3 to − 4.8 and Paleoproterozoic Nd-Hf model ages. These results suggest their derivation from partial melting of ancient continental crust. Furthermore, they have high zircon δ 18 O values of 8.6 to 10.6‰ and calculated whole-rock δ 18 O values of 10.8 to 12.5‰. Along with their peraluminous features, high K 2 O/Na 2 O ratios, arc-like trace element distribution patterns and enriched Sr–Nd–Hf isotope compositions, these Mesozoic granitoids are unambiguously derived from partial melting of metasedimentary rocks and thus are of S-type affinity. There are significant differences in both major and trace elements between the Caijiang intrusion of Triassic age and the Huangpi, Daguzhai and Luobuli intrusions of Jurassic age. While the Triassic granites exhibit high (Fe 2 O 3 ) T + MgO, P 2 O 5 , Th, LREE and Zr + Nb + Ce + Y contents but low Al 2 O 3 /TiO 2 , Rb/Ba and Rb/Sr ratios in association with high zircon saturation temperatures, the Jurassic granites have low (Fe 2 O 3 ) T + MgO, P 2 O 5 , Th, LREE and Zr + Nb + Ce + Y contents but high Al 2 O 3 /TiO 2 , Rb/Ba and Rb/Sr ratios in association with low zircon saturation temperatures. These correlations indicate that melting temperature and thus extent of partial melting have played an important role in dictating the compositions of granitoids. Therefore, the geochemical compositions of S-type granitoids are dictated not only by the composition of source rocks but also by the temperature of partial melting. [ABSTRACT FROM AUTHOR]

The Precambrian Singhbhum Craton and the adjoining orogenic belts of eastern India hold a history of continental crust generation by repeated emplacement and reworking of multiphase tonalite-trondjhemite-granodiorite (TTG) and granites throughout the Archean. Temporal classification of this complex Archean TTG and granite sequence have not been straightforward due to repeated magmatism that gave rise to complex intrusive relationships between the magmatic bodies, their complex tectonic juxtaposition and lack of geochronological data. Recent surge of new geochronological and isotope data has brought significantl clarity in the temporal relationships between different crustal components of this craton. In this study, geochemical data (published and new) of the TTG and granites (n = 251) with robust age reference was compiled and classified using a two-fold (viz. age and geochemistry) classification to understand the secular change of crustal composition. Herein, the Archean TTG suites were divided into four age-based groups, viz. Group-I (> ca. 3.5–3.4 Ga), II (ca. 3.4–3.3 Ga), III (ca. 3.3–3.2 Ga) and IV (

The Archean granitoids in the Kiéné area, Gabon, are overlained by the Paleoproterozoic sediments of the Franceville basin (2.1 Ga). The basin is known for its high-grade uranium deposits among which some have been forming natural nuclear fission reactors. Most of the studies were dedicated to the FA-FB Paleoproterozoic sediments hosting these uranium deposits. Little is known on the Archean basement itself and specifically on the hydrous alteration events it experienced before and after the sediment deposition. The present work is focused on their petrographical, mineralogical and geochemical characterization. Dating the successive alteration events has been attempted on altered monazite crystals. Rocks in different alteration states have been sampled from eight drill cores crosscutting the Archean - Paleoproterozoic unconformity. The Archean granitoids observed in the deepest levels exhibit typical petrographical features of a propylitic alteration while they are intensely illitized up to the unconformity. The propylitic alteration is mainly pervasive but the original texture of the granitoïds is conserved in spite of the formation of new minerals: Mg-chlorite, allanite and epidote forming a typical paragenesis. The illitic alteration is much more invasive near the unconformity. The illitization process leads to the replacement of feldspars and the corrosion of quartz crysals by an illitic matrix while the ferromagnesian minerals are pseudomorphosed by a Fe-chlorite + phengite + hematite assemblage. The final fluid-rock interaction step is marked by fissural deposits of calcite and anhydrite. The δ13C isotopic data show that the fissural carbonates precipitated from diagenetic fluids enriched carbon products deriving from the maturation of organic matter. The U-Pb isotopic analyzes performed on monazite crystals have dated three distinct events: 3.0-2.9 Ga (magmatic), 2.6 Ga (propylitic alteration) and 1.9 Ga (diagenetic illitization). The calculation of geochemical mass balances suggests that the water-rock ratio during the propylitic alteration event was weak. On the contrary, it was much higher during the overprinted illitization which is characterized by an intense leaching of Na, Ca, Mg, Sr, REE and an enrichment in K, Rb,Cs. Neither the petrographic features nor the geochemical data militate for an Archean weathering event (paleosol). In the present case, diagenetic fluids have percolated from the unconformity into the basement where they overprinted the illitization processes upon the previously propylitized rocks. These fluids were probably oxidant as they are also responsible of the U mobilization which led to the formation of the ore deposits close to the FA-FB interface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Granitoid magmatism changed in composition with evolution of Kadiri greenstone belt. [•] Initial sanukitoid magmatism was followed by transitional TTG, leucogranite and A-type granite. [•] A convergent setting characterized by repeated slab break-off and crustal reworking. [•] Finally post-subduction anorogenic granite magmatism. [•] Reworking of Mesoarchaean crust in eastern Dharwar craton identified. [Copyright &y& Elsevier]