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Granite is one of the most important components of the continental crust on our Earth; it thus has been an enduring studied subject in geology. According to present knowledge, granite shows a great deal of heterogeneity in terms of its texture,structure, mineral species and geochemical compositions at different scales from small dike to large batholith. However, the reasons for these variations are not well understood although numerous interpretations have been proposed. The key point of this debate is whether granitic magma can be effectively differentiated through fractional crystallization, and, if so, what kind of crystallization occurred during the magmatic evolution. Although granitic magma has high viscosity because of its elevated SiO2 content, we agree that fractional crystallization is effectively processed during its evolution based on the evidence from field investigation,mineral species and its chemical variations, and geochemical compositions. These data indicate that crystal settling by gravitation is not the only mechanism dominating granitic differentiation. On the contrary, flow segregation or dynamic sorting may be more important. Accordingly, granite can be divided into unfractionated, fractionated（including weakly fractionated and highly fractionated） and cumulated types, according to the differentiation degree. Highly fractionated granitic magmas are generally high in primary temperature or high with various volatiles during the later stage, which make the fractional crystallization much easier than the common granitic melts. In addition, effective magmatic differentiation can be also expected when the magma emplaced along a large scale of extensional structure. Highly fractionated granitic magma is easily contaminated by country rocks due to its relatively prolonged crystallization time. Thus, granites do not always reflect the characteristics of the source areas and the physical and chemical conditions of the primary magma. We proposed that highly fractionated granites are an important sign indicating compositional maturity of the continental crust, and they are also closely related to the rare-elemental（metal） mineralization of W,Sn, Nb, Ta, Li, Be, Rb, Cs, REEs, etc.

The paragenesis and composition of bavenite-bohseite were investigated in fifteen granitic pegmatites from the Bohemian Massif, Czech Republic. Three types distinct in their relation to primary Be precursors, mineral assemblages, morphology and origin were recognised: (1) primary hydrothermal bavenite-bohseite crystallised in miarolitic pockets from residual pegmatite fluids; and secondary bavenite-bohseite in two distinct types: (2) a proximal type restricted spatially to pseudomorphs after a primary Be mineral (beryl > phenakite, helvine-danalite); and (3) a distal type on brittle fractures and fissures of host pegmatite. The mineral assemblages are highly variable: (1) axinite-(Mn), smectite, calcite and pyrite; (2) bertrandite, milarite, secondary beryl, bazzite, K-feldspar, muscovite-illite, scolecite, gismondine-Ca, analcime, chlorite; and (3) muscovite, albite, quartz, epidote, pumpellyite-(Mg), pumpellyite-(Fe3+), titanite and chlorite. Electron microprobe analyses showed, in addition to major constituents (Si, Ca and Al), minor concentrations (in apfu) of Na (≤0.24), Fe (≤0.10), Mn (≤0.10) and F (≤0.36). The type 1 hydrothermal miarolitic bavenite-bohseite is mostly Al-rich (2.00-0.67 apfu) relative to type 2 proximal bavenite-bohseite and bohseite after beryl, phenakite and helvine-danalite (1.56-0.46, 0.70-0.05, 1.02-0.35 apfu, respectively); and type 3 distal bavenite-bohseite typically after beryl (1.63-0.09 apfu). Raman spectroscopy revealed that the distance between the OH- vibrational modes decreases with increasing bohseite component. The Al content of secondary type 2 proximal bavenite-bohseite is controlled by the composition of the Be precursor whereas type 3 distal bavenite-bohseite with beryl as the Be precursor is more variable and the composition is governed mainly by the composition of fluids. Calcium, a crucial component for bavenite-bohseite origins, was derived from residual pegmatite fluids (Vlastějovice, Vepice IV or Trebíc Plutons) or external sources (e.g. Drahonín IV, Věžná I or Marsíkov). Primary type 1 hydrothermal bavenite-bohseite from miarolitic pockets might have crystallised at T ≈ 300-400°C and P ≈ 200 MPa, whereas the secondary type 2 and 3 bavenite-bohseite formed at T ≈ 300-100°C and P ≈ 200-20 MPa.

Based on petrological and geochemical characteristics such as rock assemblage, petrogeochemistry, Sr-Nd isotope, zircon U-Pb age, and Hf isotope, we studied geochronological framework, magma types, source characters, and petrogenesis of different stages of magmatism of the granitic rocks from the Gangdese batholith in southern Tibet. The magmatic activities of the Gangdese batholith can be divided into three stages. The Mesozoic magmatism, induced by northern subduction of Neotethyan slab, was continuously developed, with two peak periods of Late Jurassic and Early Cretaceous. The Paleocene-Eocene magmatism was the most intensive, and resulted from a complex progress of Neotethyan oceanic slab, including subduction, rollback, and subsequent breakoff. And the Oligocene-Miocene magmatism was attributed to the convective removal of thickened lithosphere in an east-west extension setting after India-Asia collision. Isotopically, zircons from these granitic rocks are characterized by positive εHf(t) values, suggesting that the magmatic source of the Gangdese batholith might be an arc terrane, which was accreted to the southern margin of Asia during Late Paleozoic. Therefore, the chronological framework and Hf isotopic characteristics of the Gangdese batholith are distinct from the granitic rocks in adjacent areas, which can be served as a powerful tracer in studying source-to-sink relation of sediments during the uplift and erosion of Tibetan Plateau.

To better understand the transport of Mo and W in granitic melts and the formation mechanism of porphyry ore deposits, we have investigated the diffusivities of Mo and W in granitic melts with 0.04-5.1 wt% H2O at 1000-1600°C and 1 GPa using a diffusion couple approach and a Mo saturation approach with Mo sheet serving as the source. The Mo and W diffusivities obtained from diffusion profiles measured by LA-ICP-MS can be described as: DMo,anhy=10-1.47±0.73 exp[-(387±25)/RT], DW,anhy=10-1.28±1.05 exp[-(396±35)/RT], DMo,2.7wt%H2O=10-5.37±0.52 exp [-(211±18)/RT], DMo,5.1wt%H2O= 10-6.87±0.69 exp[-133±20)/RT], where D is diffusivity in m2/s (with the subscripts denoting water contents and \"anhy\" representing nominally anhydrous melt), R is the gas constant, T is the temperature in K, and the activation energies in the exponential are in kJ/mol. When the influence of H2O is incorporated, Mo diffusivity in granitic melts with <5.1 wt% H2O can be modeled as: log DMo=-(1.94±1.58) - (0.87±0.36)ω - [(19341±2784)-(2312±620)w]/T where w is H2O content in the melt in wt%. The diffusion behavior (low diffusivities, high activation energies, and strong H2O effects) of Mo and W indicates that they exist and diffuse in the melt in the form of hexavalent cations. Their low diffusivities imply that the bulk concentrations of Mo and W in exsolved hydrothermal fluid and those in the melt are probably not in equilibrium. However, because of the large fluid-melt partition coefficients of Mo and W, they can still be enriched in the hydrothermal fluid, although to a lesser extent than equilibrium partitioning would allow. Slow Mo and W diffusion can be a significant rate-limiting step for the formation of porphyry Mo/W deposits.

Helium gas is a scarce but important strategic resource, which is usually associated with natural gas. Presently, only one extra-large helium-rich gas field has been found in China: the Hetianhe Gas Field in the Tarim Basin. This paper reports a new example, the Dongsheng Gas Field (DGF) in the Ordos Basin. In this study, 92 natural gas samples from the DGF were analyzed for helium content and isotope composition using isotope mass spectrometry. The natural gas samples were found to have an average helium content of 0.133%, with 65 (70.7%) of the samples having a helium content of 0.1% or more. Based on the proven natural gas reserves of the DGF, the proven geological helium reserves were calculated to be 1.96×10 8 m 3 , suggesting that it represents the first extra-large helium-rich natural gas reservoir to be hosted in tight sandstone in China. The 3 He/ 4 He ratios of 5 natural gas samples from the DGF are within the range of 3.03×10 −8 −3.44×10 −8 . Therefore, the helium in the gas field is thought to be of typical crustal origin and to have formed in the granitic basement that is rich in uranium and thorium. The accumulation of helium-rich natural gas was controlled by regional tectonic activities. Activity along the fault connecting the reservoir with the basement caused release of the helium gas, which entered the overlying strata along the fault and accumulated with conventional hydrocarbon gas. Based on the structural background and the distribution of helium source rocks in the Ordos Basin, the main helium source rocks with high exploration potential are located in deep strata within the north and middle parts of the basin.

Experiments were conducted to explore the behavior of Li, Rb, Nb, Sn, Cs, Ta, W during crustal melting and test the anatectic origin of rare metal-bearing peraluminous granites such as rare metal granites (RMGs). The experiments were performed under fluid-absent conditions at 800 and 850 °C, 400 MPa and moderately reducing fO2 (ΔFMQ = − 0.5 to − 0.8). Starting materials were cores of several millimetres drilled from two natural rocks, a biotite-rich paragneiss (Pg) and a muscovite-rich orthogneiss (Og) enriched in Li, Be, Sn, Cs, W. Both protoliths produced small melt fractions from 8 to 20% vol. Melt distributions were either homogeneously distributed at grain boundaries in the Pg or preferentially associated with muscovite reaction zones in the Og. In the Pg at 800 °C, melting is mainly fluid present, driven by interstitial water at grain boundaries. At 850 °C, biotite dehydration-melting produces peritectic orthopyroxene, hercynitic spinel, ilmenite and alkali feldspar in addition to melt. In the Og, muscovite dehydration-melting generates melt plus peritectic biotite, hercynitic spinel, ilmenite, Al silicates and alkali feldspar. Experimental glasses are nearly homogeneous, silica rich, peraluminous and leucogranitic and their major element compositions differ only little between the two protoliths. In contrast, the trace element concentrations vary as a consequence of chemical and textural heterogeneities in our starting materials. Compared with source rocks, the Og glasses are enriched in Rb, Nb, Ta, W and depleted in Li, Cs and the Pg are enriched in Li, Rb, Cs, W and depleted in Nb, Ta. Mass-balance calculations indicate that during muscovite dehydration-melting, Li, Cs and Rb partition into the melt; whereas Nb, Ta and W are preferentially incorporated in peritectic phases. Li and Cs also partition toward the melt during biotite dehydration-melting. The partitioning behavior of trace elements during crustal melting is a function of the melting reaction and partition coefficients between melt, residual and peritectic phases. Experimental glasses are similar to peraluminous muscovite granites but fail to reproduce RMG compositions. Alternatives to mica dehydration-melting such as fluid-present and residual source melting emphasize the difficulties with an origin of RMGs by purely anatectic processes. Crystallization differentiation might have to be combined with mica dehydration-melting to explain the distinctive geochemical features of RMGs.

The Songpan-Ganze orogenic belt on the northeastern margin of the Tibetan Plateau extends westward from the Songpan-Ganze terrain in western Sichuan to the Tianshuihai region in West Kunlun, Xinjiang. It hosts numerous giant spodumene pegmatite deposits and ore fields, including Jiajika and Ke’eryin in western Sichuan Province, Zhawulong on the border between the Sichuan and Qinghai Provinces, and Dahongliutan in Xinjiang Region. These form the Songpan-Ganze-West Kunlun (SP-GZ-WK) pegmatite-type rare-metal metallogenic belt. The pegmatite type rare-metal deposits in this belt are hosted in the metamorphic thermal domes in the metamorphosed flysh of the Triassic Xikang and Bayankalashan Groups. The mineralized pegmatites are intimately related to the Li- and volatile-rich two-mica granites that are peraluminous and have high (Li+Na+K)/(Mn+Fe+Mg+Ca+Ti) ratios. Pegmatites and granites in individual ore field throughout the belt typically form a cogenetic granite-pegmatite system, in which pegmatite dikes commonly surround granites. Spodumene is the predominant ore mineral in most pegmatites with limited hydrothermal alteration. In the granite-pegmatite systems, granitic magmas were emplaced under P-T conditions of 800–850°C and ∼550 MPa, while spodumene crystallized in an alkaline environment. The granite-pegmatite systems share similar Sr-Nd-Hf-Li isotopic compositions to the metasediments of the Xikang and Bayankalashan Groups. The δ 7 Li values tend to increase from the granites to the Li-poor pegmatites, whereas the reverse is observed between the Li-poor and Li-rich pegmatites. These geochronological data suggest that the granite-pegmatite systems formed in the Late Triassic and tend to be progressively younger from the outer to the inner zones of the metallogenic belt. These characteristics show that the granitic-pegmatitic melts were derived from the anatexis of the Xikang and Bayankalashan Groups during the Paleo-Tethyan orogeny in the Late Triassic. The separation of pegmatitic melts from granitic magmas can be best explained using the Jiajika-style “melt-melt immiscibility” or the Ke’eryin-style “fractional crystallization+melt-melt immiscibility” model. High-maturity terrestrial sediments are of key importance for the anatexis that results in the granite-pegmatite melts. The bidirectional tectonic stresses in the Songpan-Ganze orogenic belt may have caused the mineralization difference between the Jiajika deposit and the Ke’eryin ore field. These features indicate the controls of the combination of orogenic deformation, metapelites anatexis, and magmatic differentiation on the rare-metal mineralization of pegmatites. We suggest that pegmatites, pegmatite-parental granite, and their protoliths are important indicators for rare-metal mineralization in the SP-GZ-WK pegmatite type rare-metal metallogenic belt. Based on the widespread presence of fertile metasediments and well development of metamorphic thermal dome, highly differentiated granites, and regional zonation of pegmatites, the Zhawulong ore field is the most prospective area for rare metals and thus should be the priority for future exploration.

The contiguous region between Guangxi, Guizhou, and Yunnan, commonly referred to as the Golden Triangle region in SW China, hosts many Carlin-type gold deposits. Previously, the ages of the gold mineralization in this region have not been well constrained due to the lack of suitable minerals for radiometric dating. This paper reports the first SIMS U–Pb age of hydrothermal rutile crystals for the Zhesang Carlin-type gold deposit in the region. The hydrothermal U-bearing rutile associated with gold-bearing sulfides in the deposit yields an U-Pb age of 213.6 ± 5.4 Ma, which is within the range of the previously reported arsenopyrite Re–Os isochron ages (204 ± 19 to 235 ± 33 Ma) for three other Carlin-type gold deposits in the region. Our new and more precise rutile U-Pb age confirms that the gold mineralization was contemporaneous with the Triassic W–Sn mineralization and associated granitic magmatism in the surrounding regions. Based on the temporal correlation, we postulate that coeval granitic plutons may be present at greater depths in the Golden Triangle region and that the formation of the Carlin-type gold deposits is probably linked to the coeval granitic magmatism in the region. This study clearly demonstrates that in situ rutile U–Pb dating is a robust tool for the geochronogical study of hydrothermal deposits that contain hydrothermal rutile.

A diverse range of dikes in the western Lhasa–Qiangtang collision zone provides constraints on the evolution of post‐collisional tectonomagmatic processes and the growth of the Tibetan Plateau. We report geochronological, geochemical, and Sr–Nd–Hf isotopic data for granitic dikes in the Rebang area of the Northern Lhasa Block, northern Tibet. Zircon U‐Pb dating of the granitic dikes reveals abundant inherited zircons with ages ranging from 1869 to 98.8 Ma, and the youngest age groups (83.9–82.0 Ma) indicate that they formed during the Late Cretaceous. The granitic dikes are characterized by high Sr and low Y contents and high Sr/Y ratios, and they have adakitic geochemical affinities and variable zircon εHf(t) (−6.01 to +9.82) and whole‐rock εNd(t) (−0.55 to +1.43) values. These features, together with the high Mg# values, suggest that the Rebang granitic dikes are derived by partial melting of thickened juvenile lower crust with variable degrees of contamination by mantle peridotite. The co‐occurrence of widely distributed dikes and thick‐bedded terrestrial molasses in the Late Cretaceous suggested that the central Tibet underwent post‐collisional extensional collapse, which was triggered by lithospheric delamination. We favor that isostatic rebound in response to delamination induces rapid surface uplifting and gravitational collapse in the Lhasa–Qiangtang collision zone. Additionally, our research proposes that the post‐collision extensional collapse in the Late Cretaceous plays an important role in the vertical growth of the Tibetan Plateau.

Egypt is mainly covered by ophiolitic rocks, muscovite, and two mica granites, in addition to different types of acidic and basic dikes. Our field observations indicated that El Sela granites were subjected to alteration types such as silicification, kaolinization, and hematitization, which is associated with uranium mineralization. Petrographic investigations clarified that these rocks were affected by saussiritization, muscovitization, and silicifications as the main alteration types associated with uranium mineralization (uranophane and autunite). We carried out chemical analyses of our samples for major oxides and trace and rare earth elements using ICP-OES and ICP-MS. The studied altered granites had high silica, titanium, and phosphorous as major components, with enhanced amounts of trace elements such as Nb, Ta, Zn, Mo, Pb, and Re, in addition to REE, especially light ones. The average REE content was higher than that of worldwide granites with LREE enrichment. One sample had a strong M-type tetrad effect in the fourth type; other samples had weak W-type in the third type, indicating the effect of hydrothermal alteration processes in the altered granites. This was confirmed by calculating the ratios of most isovalents that deviated from the chondritic ratio in many values. Variation diagrams of U and some trace elements illustrated that U had a weak positive correlation with Y and a strong positive correlation with gold, while it had weak to moderate negative correlation with Hf and Zr/U. In addition, uranium had a weakly defined correlation with the other trace elements, indicating a weak to moderate effect of magmatic processes, while the post-magmatic processes surficial or underground water greatly influenced the redistribution of uranium and other elements.