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In order to address the causes of compositional variations of crust-derived granitic rocks in continental margin arc, we focused on the petrogenesis of Eocene granitic host rocks with enclosed MMEs, associated metagabbro, fine-grained quartz-diorite in Xima-Tongbiguan area, the Tengchong Block, which is a continental margin arc related to the subduction of Neo-Tethys. Both the Eocene granitic and mafic rocks are characterized by gradual increment in enriched compositions, such as K, Rb, Th, LREE, initial 87Sr/86Sr, eNd(t), and eHf(t), but decreasing Pb isotopic ratios from the west to the east of the Tengchong Block. Zircon U Pb age data of granitic host rocks, MMEs, metagabbro and fine-grained quartz-diorite reveal a similar age range of 55–50 Ma. The lithologies, zircon Hf compositions, geochemical and isotopic signatures of host granitic rocks show that the origin of these host rocks are mainly controlled by magma mixing between felsic and mafic magma. The products of the mafic magma are dominated by metagabbro, fine-grained quartz-diorite and MMEs enclosed in granitic rocks, which are all resulted from the reaction and mixture between different mafic magmatic products and felsic magma. The metagabbros could be the products of felsic magma mixing with early crystallized mafic magma, and the fine-grained quartz-diorites could be the products of felsic magma mixing with crystal-rich mafic magma, and the MMEs could be the products of felsic magma mixing with crystal-poor mafic magma or melt. The metagabbro has positive eHf(t) values of 1.8 to 10.9, which could provide the relative primitive Lu Hf isotopic compositions of mafic magma, indicating that the mafic magma is derived from a depleted mantle. The host granitic rocks have negative eNd(t) values of −5.2 to −6.5, indicating that the felsic magma is derived from partial melting of an ancient mafic lower crust. Furthermore, there are excess reactions after magma mixing between the mafic and felsic magma, such as multi-stage reactions between solidified MMEs and felsic magma, and the disaggregation of MMEs, finally resulting in the basification of felsic magma. Magma mixing is therefore the main mechanism of the formation of granitic rocks in the Tengchong Block. The compositional variation of intermediate to acid igneous rock in a continental margin arc is likely dominated by the characteristics of mafic magma because the intermediate to acid igneous rock is derived from mixing of crust-derived granitic and different mantle sources-derived mafic magma.

Strongly peraluminous fractionated S-type granites are important indicators of compositional maturity of the continental crust. Here we report the finding of strongly peraluminous fractionated S-type granites from the western Baoshan Block in the southeastern Tibetan–Himalayan orogenic belt. We present LA ICP-MS zircon U–Pb ages from biotite- and two-mica- granites which reveal two distinct periods of magmatism at 121.8 ± 1.1 Ma and 81.9–79.7 Ma. These Cretaceous granites are strongly peraluminous (A/CNK = 1.18–1.31), high-K calc-alkaline, enriched in Rb, Th, K, and Pb, and depleted in Ba, Sr and Ti. They also show high normative- corundum contents of 2.84–4.42 wt%, moderately high P2O5 content (0.22–0.28 wt%) and high differentiation index (DI) of 93.1–96.8, similar to the features of fractionated S-type granites. The low total Fe2O3T + MgO + TiO2 contents (

Under the condition of paucity of mantle-derived ferromagnesian components, peritectic assemblage entrainment (PAE) model can properly explain a large variation of Fe, Mg, Ti, and Ca contents as well as positive linear trends for Ti and Ca plotted against maficity (molar Fe + Mg) exhibited by more mafic I-type granitic melts. Herein we present a comprehensive study of zircon U–Pb–Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotopes for newly identified Neoproterozoic high-maficity I-type granitoids collected from the Yonglang area in the western Yangtze Block, South China, in order to evaluate PAE process acting on the petrogenesis of these more mafic granitoids. Zircon U-Pb geochronological results show that the Yonglang granitoids, including the granodiorites, monzogranites, and biotite granites, yield the weighted mean 206Pb/238U ages of ca. 850–825 Ma. They are geochemically characterized by high SiO2 (64.63–72.62 wt.%) and K2O (3.49–6.59 wt.%) contents as well as variable A/CNK (0.94–1.09) and molar Fe + Mg values (0.0452–0.1210), and display a negative correlation of A/CNK and Fe + Mg, indicating an I-type affinity. Isotopically, they display negative whole-rock eNd(t) (−4.06 to−6.38) and highly evolved zircon eHf(t) values (−9.36 to +1.92) as well as old two-stage Nd model ages (1.69–1.85 Ga) and crustal Hf model ages (1608–2139 Ma), implying a crustal source. In comparison with the geochemical composition of fluid-absent experimental melts, the Yonglang I-type granitoids have Fe, Mg, Ti, and Ca contents that are too high to equilibrium with those of pure crustal melts, indicating the additional incorporation of a ferromagnesian, Ti-, and Ca-rich component into primary melts. Like the Cotoncello–Monte Capanne granitic complex in Elba Island and Verdenburg I-type granite in South Africa, the Yonglang I-type granitoids exhibit highly positive linear correlations for Ti vs. maficity and Ca vs. maficity as well as negative correlation for A/CNK vs. maficity, suggesting that these high-maficity I-type granitoids predominantly underwent the peritectic assemblage entrainment of Ca-Fe-Mg-Ti bearing minerals (e.g., clinopyroxene, plagioclase, ilmenite, etc.) during coupled melting of biotite and hornblende phases in crustal source. The process of peritectic assemblage entrainment thus play a vital role in moulding geochemical compositions of more mafic I-type granites.

The Dehua Au-polymetallic ore cluster, as one of the most important area in the Wuyi Au-Cu-Mo metallogenic belt, consists of many large to middle sized epithermal Au deposits and recently discovered porphyry Cu-Mo deposits. We first study the geochronology and geochemistry characteristics of the Cu-Mo mineralization-related Xianyang granite porphyry to constrain its petrogenesis, tectonic setting and metal endowment. LA-ICP-MS zircon U-Pb dating yield a precise age of 157.2 ± 0.8 Ma for the Xianyang granite porphyry, indicating that the granite porphyry was emplaced during the Late Jurassic. The Xianyang granite porphyry was suggested to be generated under continental arc setting, associated with subduction of the paleo-Pacific slab beneath the South China Block. The Xianyang granite porphyry belongs to the high-K calc-alkaline series, with SiO2 of 71.16–72.02 wt% and K2O of 4.28–4.69 wt%. It shows light rare earth element-enriched distribution patterns with (La/Yb)N of = 9.74–13.93, enrichment in large ion lithophile elements, but depletion of high field strength elements, with negative Nb, Ta and Ti anomalies, suggesting an arc magma geochemical affinity. It has lower initial 87Sr/86Sr ratios of 0.7079–0.7086 and relatively higher eNd(t) and eHf(t) values of −8.03 to −7.69 and − 8.86 to −5.48, respectively, than those of basement rocks of the Cathaysia block, suggesting that it was most likely generated by partial melting of the regional ancient crustal materials, with the involvement of asthenosphere mantle-derived materials. The Xianyang granite porphyry has remarkably high zircon Ce4+/Ce3+ values of 119–404 (mean = 245) and EuN/EuN* values of 0.37–0.60 (mean = 0.51), indicating a high oxygen fugacity, which is favor of the formation of the Xianyang porphyry Cu-Mo mineralization. Combining with published research results for regional subvolcanic rocks-related epithermal Au deposits, the porphyry Cu-Mo deposits and epithermal Au deposits in the Dehua ore cluster share similar petrogenetic-metallogenic ages and magma sources in the continental arc setting during the Late Jurassic period. The identification of the coeval porphyry-epithermal Cu-Mo-Au metallogenic system in the Dehua ore cluster highlights the possibility of finding the hidden porphyry Cu-Mo orebodies beneath the discovered epithermal Au deposits.

Geochemical variations in granitic rocks may be controlled by their source rocks, melting reactions and subsequent magmatic processes, which resulted from various geodynamic processes related to subduction, collision, or slab break-off. Here we report new LA–ICP-MS zircon U–Pb ages and Hf isotopes, whole-rock chemistry and Sr–Nd isotopes for the late Early Cretaceous quartz diorite, granodiorite and monzogranite in the Gaoligong belt, southeastern Tibet Plateau. The zircon U–Pb dating yield ages of 113.9 ± 1.6, 111.7 ± 0.8, and 112.8 ± 1.7 Ma for the quartz diorite, granodiorite, and monzogranite, respectively, which are coeval with bimodal magmatism in the central and northern Lhasa sub-terrane. There are the distinct sources regions for the quartz diorite and granodiorite–monzogranite association. The quartz diorites are sodic, calc-alkaline and have high Mg# (52–54) values. They also have elevated initial 87Sr/86Sr (0.707019 to 0.709176) and low eNd(t) (− 5.16 to − 7.63), with variable zircon eHf(t) values (+ 5.65 to − 9.02). Zircon chemical data indicate a typical crustal-derived character with high Th (142–1260 ppm) and U (106–1082 ppm) and moderate U/Yb ratios (0.30 to 2.32) and Y content (705–1888 ppm). Those data suggest that the quartz diorites were derived from partial melting of ancient basaltic lower crust by a mantle-derived magma in source region. The granodiorite–monzogranite association has high-K calc-alkaline, weakly peraluminous characters. They show lower Nb/Ta (5.57 to 13.8), CaO/Na2O (0.62 to 1.21), higher Al2O3/TiO2 (24.4 to 44.4) ratios, more evolved whole-rock Sr–Nd and zircon Hf isotopic signatures, all of which suggest derivation from mixed basaltic and metasedimentary source rocks in a deep crustal zone. We propose that the granitic magmatisms at ca. 113–110 Ma in the Gaologong belt was triggered by the slab break-off of Bangong–Nujiang Tethyan oceanic lithosphere.

The Na-rich intermediate-to-felsic granitic rocks provide insights into the generation of magmas in subduction zones. This paper presents zircon LA-ICP-MS U–Pb ages as well as whole-rock geochemical, mineral chemical, and in situ zircon Hf isotopic data on Na-rich granitic rocks from the Tengchong Block, SW China. The granodiorites and associated mafic magmatic enclaves (MMEs) from the Menglian batholith yield zircon U–Pb ages of 116.1 ± 0.8 to 117.8 ± 0.6 Ma and 117.7 ± 0.7 Ma, respectively. Both host granodiorites and enclaves show calc-alkaline and sodium-rich nature, enrichment in large-ion lithophile elements (LILEs), and variable depletion in zircon Hf isotopic compositions. Euhedral amphiboles in both granodiorites and associated enclaves are magnesian-hornblende with high Mg and Ca and contain euhedral plagioclase inclusions of labradorite to andesine (An36–57) composition. The granodiorite was most likely derived through the mixing of partial melts derived from juvenile basaltic lower crust and a minor evolved component of ancient crustal sources. The quartz monzodiorite–granodiorites and associated MMEs from the Xiaotang-Mangdong batholith yield zircon U–Pb ages of 120.3 ± 1.3 to 122.6 ± 0.8 Ma and 120.7 ± 1.5 Ma. These rocks are also sodium-rich and show calc-alkaline trend with negative zircon Hf isotopic compositions (− 5.55 to + 0.58). The MMEs in the host intrusions are monzogabbro with variable and depleted zircon Hf isotopic compositions. The amphiboles in the both host intrusions and the enclaves show Al-rich ferro-tschermakite composition. We infer that the quartz monzodiorite–granodiorites were derived from magmas generated by the melting of ancient basaltic rocks in the lower arc crust induced by the underplating of mantle-derived mafic magmas. The formation of the different types of Na-rich granitic rocks is correlated to the subduction of Bangong–Nujiang Tethyan ocean. A comparison with magmatism in the northern magmatic belt suggests that mantle-derived magmas played an important role in the genesis of Early Cretaceous intrusions from Tengchong to Lhasa Blocks, although crustal melting is the dominant contributor.

Eocene granitic and related igneous rocks in the western Tengchong Block are considered to be the result of eastward subduction of Neo-Tethyan oceanic lithosphere beneath the Tengchong Block. In this paper we show that the granitic and mafic rocks in the western Tengchong Block exhibit a systematic compositional variation from west to east, with Na-rich granodiorites in the Nabang area (west) that differ from coeval high-K calc-alkaline granodiorites in the Bangwan area (east), and with tholeiitic mafic rocks in the Nabang area that differ from shoshonitic mafic microgranular enclaves (MMEs) in granodiorites of the Bangwan area. In addition, high-silica biotite granites were intruded into the granodiorites in the Bangwan area. The host granodiorites, MMEs, and biotite granites in the Bangwan area yield zircon U–Pb ages of ca. 50 Ma. The MMEs have relatively low SiO 2 contents (53.1–64.95 wt%) and Mg# values (37–45), and high K 2 O (4.14–5.02 wt%) and ∑ REE contents (331–509 ppm); the MMEs contain acicular apatites that indicate quenching. The host granodiorites also have high K 2 O (4.48–5.95 wt%) and ∑ REE compositions (320–459 ppm), and together with the MMEs they are enriched in Th but depleted in Nb and Ti. The Sr–Nd–Pb isotopic compositions of the host granodiorites and the MMEs are similar, with e Hf (t) values of − 1.0 to − 10.8 and 3.3 to − 11.1, respectively. The geochemical data and igneous textures suggest that the MMEs represent a mafic magma that was derived from the partial melting of mantle pyroxenite, with the melting induced by the influx of fluids/melts from the recycling of sediments in the subducted slab. The mafic melts then caused the partial melting of lower crustal tonalitic rocks to produce granodioritic magma that was subsequently mixed with mafic magma. The biotite granites have relatively high SiO 2 contents and low Mg# values that indicate a purely crustal origin and derivation from the partial melting of upper crustal metagraywacke. The similar isotopic compositions of the biotite granites and the granodiorites can be interpreted to reflect the influence of fluids released during crystallization of the granodiorites. A comparison of contemporaneous Eocene granitic and mafic rocks in Nabang, Tongbiguan, Longchuan, and Bangwan in the Tengchong Block reveals that the mafic rocks vary from tholeiitic through high-K calc-alkaline to shoshonitic in composition from west to east, while the granitic rocks vary from Na- to K-rich. These systematic compositional variations indicate that the arc magmatism in the western Tengchong Block was the result of the eastward subduction of the Neo-Tethyan oceanic lithosphere. Fluids or/and melts from the subducted slab (including sediments) are likely to have played an important role in producing these compositional variations.

Early Paleozoic mafic dykes are widespread in the South Qinling Belt, central China. In this study, we present new major and trace element, zircon U–Pb age and Sr–Nd–Hf isotopic results of Early Paleozoic diabases dykes in the South Qinling Belt to explore the nature of their mantle source. The zircon U–Pb dating yielded ages of 455.9 ± 1.5 Ma and 446.2 ± 1.1 Ma. The South Qinling Belt diabases had low SiO2 (42.1–49.5 wt%), high TiO2 (2.89–5.17 wt%) and variable MgO (4.0–9.4 wt%) contents. In primitive mantle normalized multi-element diagrams, all samples were strongly enriched in the majority of incompatible trace elements but showed systematic depletion in Rb, K, Pb, Zr and Hf. The negative K and Rb anomalies, together with high TiO2 and high Na2O/K2O, suggests magma was derived from a source rich in amphibole. Partial melting modeling indicated that 20%–36% partial melting of amphibole-clinopyroxene-phlogopite veins with subsequent dissolution of ~30% orthopyroxene from the wall-rock peridotite within the spinel stability field can produce the observed diabase compositions. Additionally, the South Qinling Belt diabases were characterized by moderately depleted Nd (eNd(t) = +2.2 to +3.3) and Hf (eHf(t) = +6.2 to +7.2) isotopic compositions without pronounced isotope decoupling, indicating mantle metasomatism occurred prior to Early Paleozoic magmatism. We propose that low-degree silicate melts released from the asthenosphere infiltrated and solidified within the lithospheric mantle, forming non-peridotitic lithologies rich in amphibole, clinopyroxene and phlogopite. Subsequent lithospheric extension caused the melting of the most easily fusible material in the lithosphere, which gave rise to the Early Paleozoic alkaline magmatism in South Qinling.

The granite is one of most widely distribution rocks in crust, and its petrogenesis is crucial to advance our knowledge of thermal condition in continental crust. The long-time tectonic evolution of crust in the active continental margin could be recorded by multi-stages of granitic assemblage. In order to reveal the subduction of Neo-Tethys and initial collision of Indian-Asian continents in eastern Tibetan Plateau, we selected the Early Paleocene to Early Eocene granitic rocks with associated enclaves in Tengchong Block, southeastern extension of Gangdese magmatic belt, to clarify their different derivation regimes using geochemical and isotopic compositions, mineral compositional variation. The zircon data show that Early Paleocene granites formed at 64 Ma, and Early Eocene granitic rocks formed at 54 Ma. Combing with the field contact relationship, the similar and enriched Sr-Nd-Pb and zircon Hf isotopic compositions indicate that the two stages of granitic rocks have a common and ancient lower crustal source. The enclaves in Early Paleocene granites could represent crystallization of coeval and cognate magmas at margin of magmatic conduit, but the enclaves in Early Eocene granitic rocks are products of magma mixing between mafic and felsic magma. According to rock assemblages and geochemical signatures of granitic rocks during Early Paleocene to Early Eocene in Tengchong Block, we propose that Early Paleocene granitic rocks are derived from partial melting of lower crustal rocks induced by long-lived heat accumulation with no or minimal basalt flux during the Neo-Tethyan subduction, whereas Early Eocene granitic rocks are derived from melting of crustal materials resulted from high mafic magma flux during Indian-Asian continental collision. The initial collision occurred at ca. 55 Ma.

Silicic magmas, primarily felsic I- and S-type granite (sensu lato), play a key role in understanding the compositional evolution and differentiation of the continental crust. However, the genetic models of felsic I-type granites remain controversial. Herein we investigate the Gaoligong granite (sensu lato) belt in southern Tibet and compare its features with an extensive dataset that we compiled on high‑potassium calc-alkaline peraluminous I-type granite from typical granitic belts around the word with a view to gain insights on the genesis of felsic I-type granites. The Early-Cretaceous granites from Gaoligong belt mostly belong to high-K calc-alkaline peraluminous I-type series. Zircon Lu Hf (eHf(t) = −16.3 – +0.9) and whole-rock Sr Nd isotopic data (eNd(t) = −14.6 – +3.0) on these rocks show highly variable and evolved nature, suggesting that the granites were generated by partial melting of lower crustal materials with possible involvement of upper crustal materials, followed by mixing, leading to marked variation in source compositions. Compilation of the dataset and comparison with felsic I- and S-type granites show the following salient features: (1) possibly distinct trends of Al2O3, P2O5, K2O, Rb, Sr, Pb, Th, U and Ga vs. MgO + FeOT between the felsic I-type granites and those S-types; and (2) there are notably higher and variable zircon Hf (eHf(t) > 10e units) and whole-rock Sr Nd (eNd(t) > 5e units) isotopic compositions of I-type granites than those of the S-types. Comparison with experimental liquids and other typical cases around the world, indicate that the felsic I-type granites from Gaoligong are similar to those secondary I-type granites, where mixing processes and extensive partial melting of the heterogeneous lower crust by a mantle-like magma control the variable components. The range of compositional diversity is significantly higher for the studied felsic I-type granites than those typical S-type granites from north Queensland. Our study provides further insights into the application of geochemical and isotopic proxies to differentiate felsic I- and S-type granites.

Deciphering the geochemical diversity of S-type granites is crucial for obtaining more profound insight into their petrogenesis. We therefore undertook an integrated study of whole-rock geochemistry, Sr-Nd isotopes, and zircon U-Pb-Hf isotopes for newly recognized Late Mesoproterozoic S-type granites, including two-mica-, biotite-, garnet-bearing two-mica granites, from the western Yangtze Block, South China. The crystallization ages of these granites are ca. 1040 Ma (weighted mean 206Pb/238U age = 1036.4 ± 4.5 Ma to 1042.2 ± 1.1 Ma). They are peraluminous to strongly peraluminous (A/CNK = molar ratio of Al2O3/(CaO + Na2O + K2O) = 1.02–1.67), high-K calc-alkaline rocks, and display high concentrations of normative-corundum (0.54–7.04 wt%) as well as positive correlations of A/CNK and FeOT + MgO values, which are characteristics of S-type granites. These S-type granites are characterized by enriched in Rb, Th, K, and Pb, depleted in Ba, Sr, Ti, and Eu, with negative whole-rock eNd(t) (−0.3 to −6.8) and predominantly negative zircon eHf(t) values (−8.09 to +5.70), indicating the affinity of middle-upper crustal trends and a heterogeneous metasedimentary source. Compared with the geochemical diversity of S-type granites around the world, the variably negative eNd(t) values as well as positive and negative eHf(t) values of our S-type granites may be caused by source heterogeneity and disequilibrium melting processes. More importantly, similar to typical more mafic S-type granites from the Cape Granite Suite (South Africa) and north Queensland (Australia), the high and variable FeOT + MgO contents (2.21–6.64 wt%) are significantly attributed to coupled co-entrainment of peritectic and accessory minerals (e.g., garnet, ilmenite, zircon, and monazite), evidenced by positive relationships between FeOT + MgO and TiO2, CaO, Zr, Th, Hf, Y, Yb, light rare earth elements (LREEs). In conjunction with the existence of coeval rift-related A-type igneous rocks, depleted asthenosphere-derived mafic rocks, marine sedimentary sequences, and subsequent extensive Neoproterozoic arc magmatism along the western Yangtze Block, we infer that the ca. 1040 Ma S-type granites studied here were produced in a continental rifting basin that was transformed into a compression setting during the Neoproterozoic.