The fluids in of pegmatite rare metal deposits are generally rich in rare metal elements and volatiles (B, P, F, H₂O, CO₂, etc.), and they have a high capacity for dissolving and migrating rare metals. The Dakalasu No. 1 rare metal pegmatite vein is located in northwest China’s Altay orogenic belt. Previous studies have indicated that it is a small- to medium-sized beryllium-niobium-tantalum deposit. It showed significant mineral assemblage zonations from the rim to the core, and the mineralizing fluids define a volatile-rich NaCl-H₂O-CO₂ ± CH₄ system. In this contribution, beryl and quartz, which are widely developed in each mineral association and textural zone, were selected for fluid inclusion research through detailed petrographic investigation, microthermometry, and LA-ICP-MS analysis. Petrographic results show that at least three types of fluid inclusions are developed in each mineral textural zone. They are CO₂-rich inclusions (type I), gas-liquid two-phase inclusions (type II), and daughter mineral-bearing inclusions (type III), respectively. Additionally, minor melt inclusions (type IV) are visible in the beryl from the rim zone. Microthermometric measurements showed that the homogenization temperature of fluid inclusions in the rim zone was concentrated between 242 °C and 293 °C, with an average of 267 °C, and the salinity was between 7.2–10.3 wt% NaCl_eqv, with an average of 8.6 wt% NaCl_eqv. In comparison, the temperature of the core zone was in the range of 225–278 °C, with an average of 246 °C, and the salinity focused between 6.0–7.7 wt% NaCl_eqv, with an average of 7.1 wt% NaCl_eqv. The quantitative analysis of individual inclusions by LA-ICP-MS revealed that Li, B, K, Zn, Rb, Sb, Cs, and As were relatively enriched in the rim zone. In contrast, the core zone showed a decreasing trend in trace elements such as Li, B, K, Rb, and Cs. The CO₂ content in the fluid exhibited the same decreasing trend from the rim to the core zone, indicating that volatile components such as CO₂ played an essential role in the migration and enrichment of rare metal elements. The melt-fluid immiscibility is likely to be a necessary mechanism for significantly enriching rare metals in the Dakalasu No. 1 pegmatite dyke. Full article

The No. 5 pegmatite vein is the most evolved and well mineralized vein in the Renli deposit, with beryl being the most important beryllium mineral. The vein represents one of the most important gem-quality aquamarine mines at Renli. In this study, beryl crystals from the No. 5 pegmatite vein were examined by EMPA (electron microprobe analysis), ICP-MS (inductively coupled plasma-mass spectrometry), XRD (diffraction of X-rays), FTIR (fourier transform infrared spectrometer), and Raman analyses. Field and petrographic observations showed that most beryl crystals are euhedral to subhedral with light to medium blue color. EMPA analyses indicated that the main chemical compositions of beryl are close to the ideal values, with relatively low Fe (0.222–0.690 wt%) and alkali metal (0.280–0.820 wt%) contents. Geochemical and spectroscopic analyses indicated that cations replacement in beryl is relatively simple. The substituting cations of beryl in the octahedral Al site include mainly: Mg²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Cr³⁺, Ti⁴⁺, and the excess Si. The tetrahedral Be site is mainly replaced by Li. Alkali metals in channel (esp. Na) serve as a charge compensator. According to the Fe-Mg-alkali and Li-Cs contents, the beryls from No. 5 pegmatite belong to the low Li-Cs and low Fe-Mg-medium alkali beryl groups. Field and geochemical data indicated that the No. 5 pegmatite vein formed by the multistage Mufushan granitic pluton emplacement and the magma source was less evolved. Full article

The recently discovered Daping tungsten deposit is located about 25 km north of Tongcheng County, Hubei Province, in the northern margin of the Sijiapu granite deposit of the Mufushan composite batholith. The ore body is produced in the northeast-oriented greisenization granite and quartz vein, and belongs to the greisen-vein-type scheelite deposit. The resources of the Daping W deposit have a value of 7935 t W and the average grade is 0.201% WO₃. Based on mineralogical and petrographic studies, scheelite is classified into two types. A study of the geochemical characteristics of rare earth elements (REEs) and trace elements indicated that some scheelite specimens showed LREE depletion. Meanwhile, the total amount of scheelite rare earth elements (REEs) is low and the ratio of LREE/HREE ranges from 0.40~2.72 in the Daping W deposit. The contents of REEs and trace elements in the two types of scheelite differ significantly. Type I scheelite has an average ∑REE content of 195.65 ppm, an LREE/HREE value of 0.5, an Eu anomaly (δEu) of 0.78, Mo of 366.20 ppm, Sn of 22.62 ppm, and Sr of 264.80 ppm. However, type II scheelite features an average ∑REE of 111.28 ppm, an LREE/HREE ratio of 1.43, a δEu of 1.56, Mo of 188.48 ppm, Sn of 0.15 ppm, and Sr of 829.93 ppm. The content level of Mo in the two types of scheelite is not high, indicating that this whole metallogenic environment is a reduction environment. However, this is a complex process. The presence of type I scheelite with negative Eu anomalies and relatively high Mo content indicates that the ore-forming environment in the early period of the greisen stage was relatively oxidizing. In contrast, type II scheelite contains large amounts of Sr and large positive Eu anomalies, which are likely to be released from plagioclase in the granite during greisenization. The extremely low composition of Mo in type II scheelite is closely related to the reducing environment in the later period of the greisen stage. Because Mo probably exists in its Mo⁴⁺ state, it may be difficult for it to replace W⁶⁺ in the scheelite lattice. Additionally, comparing the contents of Sn and Sr in different types of scheelite shows that the metallogenic environment changes from relative oxidation to the reduction of scheelite. The variation in trace elements and REEs in scheelite over time reflects a complex magmatic–hydrothermal mineralization environment. Additionally, the Ar–Ar system dating results for muscovite that is closely associated with scheelite in the greisenization granite vein indicate that a muscovite ⁴⁰Ar/³⁹Ar plateau age of about 133 Ma represents the time of tungsten mineralization. This muscovite ⁴⁰Ar/³⁹Ar dating result is close to the previous zircon U-Pb age data of the biotite monzogranite (ca. 140–145 Ma), which is the largest intrusion in the orefield. Meanwhile, the new age data reported here confirm that the Daping tungsten deposit represents a Mesozoic magmatic–hydrothermal mineralization event with a setting of lithospheric extension in the Mufushan composite batholith. Full article

There are many celestine deposits and mineralization points in the Huayingshan ore district which form the largest strontium resource base in China. Among these celestine deposits, the Yuxia and Xinglong are two of the larger deposits. Previous studies have displayed different views on the genesis of the celestine deposit in the Huayingshan ore district. In this study, we conducted field obversions, geochemistry, and fluid inclusion studies to investigate the sources of ore-forming matters and the metallogenic mechanism of the celestine deposit. Four types of fluid inclusion (FI), namely PL (pure liquid FI), PV (pure vapor FI), L-V (liquid-vapor two-phase FI), and L-V-S (liquid-vapor-solid three-phase FI) have been identified in celestine from different types of ore in the Xishan anticline. The ore-forming fluids belong to the NaCl-H₂ O system with moderate to low temperature (190–220 °C) and moderate salinity (5–9 wt%, NaCl equiv.). Different types of ores were formed by the same period of hydrothermal activity, which is supported by the results of the microthermometer study. Geological, thermometric data, and published hydrogen and oxygen isotope results indicate that the hot brines associated with mineralization mainly originated from meteoric water and some of diagenetic fluid. The Sr (⁸⁷Sr/⁸⁶Sr = 0.7076–0.7078) and S (δ³⁴S = 36.4–39.0) isotope values of celestine are consistent with those of the Jialingjiang Formation, indicating that ore metals in hot brines were predominantly derived from that formation. In situ analysis of celestine shows that there is a strong negative correlation between Sr and CaO (R² = 0.95) and combined with mineralogical and isotope geochemical evidence, we concluded that the precipitation mechanism of celestine is the replacement of gypsum with Sr-rich hot brines. Based on the above research and the classification of celestine deposit type, we classified the celestine deposits in Huayingshan as being of hydrothermal type. The formation of celestine deposits can be divided into three periods: (1) evaporation period, forming the source bed; (2) hydrothermal activity period, forming celestine by replacement of gypsum with Sr-rich hot brines; (3) supergene period, where meteoric water dissolves orebodies and strontianization occurs. Full article

Li-F granites from the Kester deposit (Yana Plateau in Yakutia, Russia) are proved to be connected with a rare-metal complex of accessory minerals: montebrasite, columbite-(Mn), columbite-(Fe), tantalite-(Mn), Ta-bearing cassiterite, U-bearing microlite, W-bearing ixiolite, niobian ferberite, U–Hf-rich zircon, and Ta-bearing rutile. Accessory wodginite was discovered at depths of up to 150 m in association with tantalite-(Mn), columbite-(Mn), and cassiterite. According to the content of WO₃ (1.23%–3.33%) and the values of Mn/(Mn + Fe_t) and Ta/(Ta + Nb), Yakut wodginite is an intermediate mineral between wodginite and a hypothetical mineral of the wodginite group—”wolframowodginite”. The discovery of tungsten-bearing wodginite at the Kester deposit confirms the widespread presence of tungstic and tungsten-bearing accessory minerals in Li-F granites in the Russian Far East. It also serves as an indicator of rare-metal tin-tantalum-bearing granites and pegmatites. Full article

The world-class Shimensi tungsten (W)-polymetallic deposit is located in Jiangnan Orogen, with an estimated reserve of 742.5 kt WO₃ @ 0.195% W, 403.6 kt Cu and 28 kt Mo. In this paper, the trace elements and Pb-O isotopes of scheelite (the main ore mineral) are presented to study the ore-forming material source and ore-forming fluid evolution. The results show that the REE distribution in scheelite is mainly controlled by the substitution mechanism of 3Ca²⁺ = 2REE³⁺ + □Ca (where □Ca is the Ca-site vacancy). Oxygen isotope data indicate that the scheelite mineralization occurred under high-temperature oxygen isotope equilibrium conditions, and that the ore-forming fluid has a magmatic–hydrothermal origin. The variation in scheelite Eu anomalies and the wide range of scheelite Y/Ho ratio indicate that the ore-forming fluid evolves from reducing to oxidizing, and the early-stage and late-stage ore-forming fluid may have been relatively rich in F⁻ and HCO₃⁻, respectively. The significant Mo decrease in scheelite from the early to late stage that are opposite to the influence of fO₂ variation may have resulted from the crystallization of molybdenite and Mo-rich scheelite. Lead isotopes of the ore minerals of scheelite, wolframite, molybdenite and chalcopyrite can be divided into three groups, similar to these of feldspars in different granites. Both the Mesozoic porphyritic and fine-grained biotite granites have Pb isotope ratios similar to the ores, which suggests that the former two are the main ore material source. Full article

Hydrothermal vein-type fluorite deposits are the most important metallogenic type of fluorite deposits in South China, most of which are closely related to granitoid in space; however, the genetic relationship between granitoid and fluorite mineralization remains controversial. The Shuanghuajiang fluorite deposit in northern Guangxi of South China is a typical vein-type fluorite deposit hosted in a granite pluton, with the orebodies occurring within brittle faults. Zircon U-Pb dating of the hosting Xiangcaoping granite yields an emplacement age of 228.04 ± 0.76 Ma (MSWD = 0.072). Fluorite Sm-Nd dating yields an isochron age of 185 ± 18 Ma. The new age data indicate that the fluorite deposit was precipitated significantly later than the emplacement of the hosting Xiangcaoping granite pluton. The fluorite and granite exhibit similar rare earth element (REE) patterns with negative Eu anomalies, suggesting that fluorine (F) was derived from the granite. The fluorite fluid inclusions show a homogeneous temperature mainly ranging between 165 °C and 180 °C. Salinity is typically less than 1% NaCl eqv, while the δ¹⁸O_V-SMOW and δD_V-SMOW values are between −5.2‰–−6.1‰ and −17.35‰–−23.9‰, respectively. These indicate that the ore-forming fluids were a NaCl-H₂O system with medium-low temperature and low salinity, which is typical for meteoric water. Given the combined evidence of geochronology, REE, and fluid geochemistry, the mineralization of the Shuanghuajiang fluorite deposit is unrelated to magmatic-hydrothermal activity but achieved via hydrothermal circulation and leaching mechanisms. Our study presents a genetic relationship between the fluorite deposit and granitoids based on an example of northern Guangxi, providing a better understanding of the genesis of hydrothermal vein-type fluorite deposits in granitoids outcropping areas. Full article

The Xuebaoding W–Sn–Be mining area, located in the Songpan–Garze orogenic belt in western China, is known for producing large, colorful, euhedral crystals of scheelite, cassiterite, and tabular beryl. Zircon LA-ICP-MS U–Pb dating of the Wuzhutang granite yields a concordia age of 218.96 ± 2.1 Ma, and a weighted mean ²⁰⁶Pb/²³⁸U age of 218.98 ± 1.12 Ma. Cassiterite LA-MC-ICPMS dating of the quartz vein bearing beryl, cassiterite, and scheelite, yields a concordant age of 213.5 ± 1.7 Ma. These observations indicate that magmatic activities and mineralization on the western side of the Zibaishan dome occurred during the late Indosinian, prior to their occurrence on the eastern side of the dome, reflecting the fact that the granite may have undergone two epochs of magmatic evolution and metallogenic processes. Geochemical analysis revealed that the Wuzhutang granite has relatively high A/CNK (average: 1.05) and differentiation index (DI; 81.16~85.88) values, and that they are enriched in W, Sn, Be, Li, and Cs. Unlike the Pukouling and Pankou granites, the Wuzhutang granite contains a certain amount of plagioclase and relatively high contents of Ba (633~1007 ppm) and Sr (334~411 ppm). Sr–Nd–Pb isotope values (⁸⁷Sr/⁸⁶Sr(t) = 0.70747–0.70865, ε_Nd(t) = −6.35 to –4.34, ²⁰⁶Pb/²⁰⁴Pb = 18.186–18.3, ²⁰⁷Pb/²⁰⁴Pb = 15.556–15.592, and ²⁰⁸Pb/²⁰⁴Pb = 38.268–38.432) indicate a Mesoproterozoic basement origin for the Wuzhutang granite. We suggest the three granites belong to a peraluminous magma system and were derived by partial melting of the upper crust, the magma of the Wuzhutang granite originated from a deeper source and exhibits a lower degree of differentiation than that of the Pankou and Pukouling granites. Full article

The Cuonadong deposit is the first large scale Sn-W-Be rare polymetallic deposit located in southern Tibet, China, where beryl is the main beryllium-bearing mineral. In this paper, the beryl crystals in the pegmatitic and hydrothermal vein orebody from the Xianglin area of the Cuonadong deposit are the research objects, marked as Beryl-I and Beryl-II, and they are investigated by EPMA, LA-ICP-MS and in situ micro-X-ray diffraction (XRD). Data by EPMA and LA-ICP-MS reveal that beryls from this area are alkaline beryls, among which Beryl-I is composed of Li-Cs beryl, and Beryl-II is composed of Na beryl and Na-Li beryl, indicating that beryls have undergone noticeable alkali metasomatism during formation. The Cs/Na ratio in Beryl-I ranges from 0.10 to 0.44, and the Mg/Fe ratio is almost 0, showing that Beryl-I is formed under high-differentiation evolution conditions and is rarely affected by hydrothermal transformation, whereas the Mg/Fe ratio in Beryl-II ranges from 2.73 to 17.31, and the Cs/Na ratio is nearly 0, indicating that Beryl-II has been obviously affected by late hydrothermal metasomatism. In situ XRD analysis shows that both Beryl-I and Beryl-II are t-beryl, and the c/a ratio of Beryl-I (1.0010–1.0012) is slightly higher than that of Beryl-II (1.0005–1.0008), which may also reflect the transition from magmatism to hydrothermal metasomatism in the late stage of pegmatitic magmatism. Based on comprehensive analysis, we believe that the precipitation of Beryl-I is mainly caused by the emplacement of highly fractionated magma containing Be to the top of the rock mass or surrounding rock, the melt-fluid undercooling, and the crystallization of volatile-bearing minerals (such as tourmaline and fluorite). Moreover, the Be-bearing ore-forming fluid has further migrated upward along the near north–south faults formed in the middle Miocene (16–15 Ma), during which Beryl-II precipitates owing to the hydrothermal water mixing, the ore-forming fluid cooling, and large amounts of crystallization of volatile-bearing minerals (mainly fluorite). Therefore, it can be concluded that beryl mineralization largely reflects the process of magmatic–hydrothermal mineralization. Because of a large number of mineralized areas with the similar metallogenic backgrounds to the Cuonadong deposit in the Himalayan region, it has great potential to be a new globally significant rare metal metallogenic belt. Full article

The mineralogical studies of rare-element (REL) pegmatites are important for unraveling the ore-forming process and evaluating REL mineralization potential. The Chinese Altai orogenic belt hosting more than 100,000 pegmatite dykes is famous for rare-metal resources worldwide and diverse REL mineralization types. In this paper, we present the results of EMPA and LA-ICP-MS for muscovite from the typical REL pegmatite dykes of the Chinese Altai. The studied pegmatites are Li-Be-Nb-Ta, Li-Nb-Ta, Nb-Ta, Be-Nb-Ta, Be and barren pegmatites. The Li⁺ accompanied with Fe, Mg and Mn substitute for Al³⁺ at the octahedral site in muscovite from the REL pegmatites, and the substitution of Rb by Cs at the interlayer space is identified in muscovite from the Be pegmatites. The P and B contents increase with evolution degree and the lenses from the Nb-Ta pegmatite are produced at late fluid-rich stage with high fluxes (P and B). The enrichment of HFSE in muscovite indicates a Nb-Ta-Sn-W rich pegmatite magma for the Be-Nb-Ta pegmatite. From barren pegmatite, beryl-bearing zone, to spodumene-bearing zone, the evolution degrees of pegmatite-forming magmas progressively increase. In the Chinese Altai, the possible indicators of muscovite for REL mineralization types include Rb (ca. 400–600 ppm, barren pegmatite; ca. 1200–4000 ppm, Be pegmatite; >4500 ppm, Li pegmatite), Cs (ca. 5–50 ppm, barren pegmatite; ca. 100–500 ppm, Be pegmatite; >300 ppm, Li pegmatite) and Ge (<3 ppm, barren pegmatite; ca. 4–6 ppm, Be pegmatite; ca. 6–12 ppm, Li pegmatite) coupled with Ta, Be (both <10 ppm, barren pegmatite) and FeO (ca. 3–4 wt%, Be pegmatite; ca. 1–2.5 wt%, Li pegmatite). The plots of Nb/Ta vs. Cs and K/Rb vs. Ge are proposed to discriminate barren, Be- and Nb-Ta-(Li-Be-Rb-Cs) pegmatites. The Li, Be, Rb, Cs and F concentrations of forming liquid are evaluated based on the trace element compositions of muscovite. The high Rb and Cs contents of liquid and lower Be contents than beryl saturation value indicate that both highly evolved pegmatite magma and low temperature at emplacement contribute to beryl formation. The liquids saturated with spodumene have large variations of Li, possibly related to metastable state at Li unsaturation–supersaturation or heterogeneous distribution of lithium in the system. Full article

The Hubi copper (cobalt) ore district, one of the largest typical examples of the sediment-hosted stratiform type in the Zhongtiao Mountain area, is located on the southern margin of the Trans-North China Orogen within the North China Craton (NCC) and has a copper reserve of 0.79 Mt. Mineralization is mainly hosted by the Zhongtiao Group, a sequence of metasedimentary rocks deposited from ~2168 Ma to ~2059 Ma. Subsequently, a collisional orogeny (Trans-North China Orogen) occurred at ~1.85 Ga. The absolute age of mineralization has not been well constrained due to the lack of suitable minerals for dating. Rutile and monazite are common accessory minerals and are intergrown with Cu mineralization in Cu-bearing veins in the Hubi-type copper (cobalt) deposits. This study presents the first new LA-ICP-MS U-Pb ages of hydrothermal rutile and monazite for the Tongmugou and Laobaotan copper (cobalt) deposits in the ore district, which yield lower intercept rutile U-Pb ages of 1815 ± 30 Ma (Mean Squared Weighted Deviation, MSWD = 5.0) and 1858 ± 27 Ma (MSWD = 5.2) for Tongmugou and 1876 ± 30 Ma (MSWD = 5.9) for Laobaotan. Monazite crystals separated from Cu-bearing carbonate veins within the orebody of Tongmugou yield a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 1856 ± 14 Ma (MSWD = 1.9), which is close to that of rutile within error. Mineralogical observations and geochemical characteristics suggest that both monazite and rutile crystallized in the hydrothermal fluid system and are closely related to Cu sulfide mineralization. Therefore, their nearly identical U-Pb isotope age of ca. 1850 Ma directly reflects the timing of metamorphic hydrothermal Cu mineralization. This age is indistinguishable from that of metamorphism during the collisional orogeny (Trans-North China Orogen) that led to the final amalgamation of the Eastern and Western Blocks. According to previous studies, the primary sedimentary mineralization of the Hubi-type copper (cobalt) deposits was synchronous with the deposition of the Zhongtiao Group. From the perspective of mineralization age, both the Congolese–Zambian Copperbelt and the Hubi copper (cobalt) ore district experienced early preorogenic sedimentary diagenetic mineralization and late metamorphic hydrothermal mineralization related to orogenesis, and the Hubi-type copper (cobalt) deposits may also be some of the oldest sediment-hosted stratiform-type deposits in the world. Moreover, this metamorphic hydrothermal Cu mineralization spread throughout the Zhongtiao Mountain area. Full article

Chuankou tungsten (W) ore field, with an estimated WO3 reserve exceeding 300,000 tonnes, is so far the largest Indosinian (Triassic) granite-related W ore field in South China. However, the precise emplacement ages, sources of granitoids, and their relationship with W mineralization are still not well understood. In this research, four main magmatic stages (G-1 to G-4) have been identified in the Chuankou ore field, including G-1 (phase I, biotite monzogranite), G-2 (phase II, two-mica monzogranite), G-3 (phase III, fine-grained granite), and G-4 (phase IV, granite porphyry). LA-ICP-MS U-Pb dating of zircon grains from granitoids of the Chuankou W ore field yields emplacement ages of 230.8 ± 1.6 Ma, 222.1 ± 0.56 Ma, 203.1 ± 1.6 Ma, and 135.5 ± 2.4 Ma, respectively. Granitoids from the Chuankou ore field contain a large amount of peraluminous minerals such as biotite, musvite, garnet and tourmaline. Geochemically, the granitoids have high Si and Al (A/CNK > 1.1) content but low alkali, Fe, Mg, Mn, and Ca content. Moreover, there is enrichment of Rb, Zr, Hf, Th, and U, but depletions of Ba, Sr, P, and Ti. The granitoids have especially low Zr + Nb + Ce + Y and high Rb/Ba ratios, further indicating a highly fractionated S-type granite affinity with a significant crystal fractionation process in regard to K-feldspar, plagioclase, biotite, Ti-bearing minerals (except rutile), zircon, apatite, allanite, and monazite. Whole-rock εNd(t) and TDM2 values are −10.77 and 2090 Ma for G-1, −9.09 to −7.47 and 1764–1684 Ma for G-2, −10.07 to −6.53 and 1669–1471 Ma for G-3, respectively, indicating that the Chuankou granitoids were derived from two episodes of partial melting of the Paleoproterozoic to Mesoproterozoic metamorphic basement. Trace elements within the zircons and whole-rock geochemistry yielded evidence of the close relationship between W mineralization and G-1 and G-2 granitoids of the Chuankou ore field. The batholith of the Chuankou ore field was formed 20–10 Ma later than the peak age of the collisions orogeny and formed in a post-collisional setting. Full article

The Jiajika rare-metal deposit located in western Sichuan Province (China) is renowned as the largest lithium deposit in Asia, and the No. 134 pegmatite dike is the largest lithium pegmatite under mining conditions in the area. On the basis of a detailed characterization of textures and minerals in the Jiajika No. 134 pegmatite, two zones (the barren Zone I and the spodumene Zone II) and three subzones (Zone II was subdivided into microcrystalline, medium-fine grained and coarse-grained spodumene zones) have been identified. The detailed mineralogical characteristics of lithium minerals and other indicator minerals from each zone were evaluated by EPMA for illustrating the magmatic–hydrothermal evolution and the cooling path of the Jiajika No. 134 pegmatite. From the outer zone inwards, grain size gradually increased, the typical graphic pegmatite zone was absent, and spodumene randomly crystallized throughout nearly the whole pegmatite body. This evidence indicated a Li-saturated melt prior to pegmatite crystallization, which could be the main cause of the super-large-scale Li mineralization of the Jiajika No. 134 pegmatite. A comparison of the Cs content between primary beryl in the Jiajika No. 134 pegmatite and other important Li-Cs-Ta pegmatites in the world indicates that No. 134 pegmatite shows a high degree of fractional crystallization. The evolution of mica species from muscovite to Li-micas from Zone I to Zone II marks the transition from the magmatic to the hydrothermal stage in pegmatite evolution. The absence of individual lepidolite and the relatively limited scale of alteration of spodumene (<10 vol%) suggest that the activity of the hydrothermal fluids in the system is limited, which contributes to the preservation of the easily altered Li ores and is also an important controlling factor of the super-large-scale Li mineralization of the pegmatite. Spodumene–quartz intergrowth (SQI) usually occurs partly along the rims of the spodumene grains in the Jiajika No. 134 pegmatite. Combined with the pegmatite mineral equilibria, the results of fluid inclusion studies of the pegmatite and the metamorphic conditions in the area, a constrained P-T path of the magmatic–hydrothermal crystallization of the Jiajika No. 134 pegmatite is proposed. The unusual steeply sloped cooling path of the No. 134 pegmatite could be attributed to the fast pressure drop triggered by the intrusion of a pegmatitic melt along the fractures surrounding the Majingzi granite, which could also be the dominant evolution process for other spodumene pegmatites with similar SQI features in the world. The feature of limited internal geochemical fractionation suggested by mineral-scale geochemical analyses of spodumene and micas, combined with the clear textural zoning of the No. 134 pegmatite, can best be ascribed to the effect of undercooling during pegmatite formation. This effect might be one of the non-negligible rules of pegmatite petrogenesis, and would significantly upgrade the potential of Li mineralization by minimizing diffusional Li transfer to the country rocks. Full article

The Yao’an gold deposit is located in the middle of the Jinshajiang-Ailaoshan alkali-rich metallogenic belt, and this belt hosts many porphyry-type Cu-Au-Mo deposits formed at 46–33 Ma. Yao’an porphyry gold-mineralization is intimately associated with biotite syenite porphyry, whereas the contemporaneous quartz syenite porphyry is barren. In this study, we compared the major and trace elements of apatite and zircon and isotopic compositions of zircon from the biotite syenite porphyry and quartz syenite porphyry, to explore their geochemical differences that may affect their mineralization potential. The results show that both porphyries were derived from the partial melting of the thickened lower crust, which has been modified by slab-derived fluids, but has different mineral crystallization sequences, magma fluid activities, and magma oxidation states, respectively. REE contents in apatite and zircon can be used to reveal the crystallization sequence of minerals. A rapid decrease of (La/Yb)_N ratio in apatite from both porphyries may be caused by the crystallization of allanite. Large variation of Cl contents and negative correlation between F/Cl and (La/Yb)_N in apatite from fertile porphyry indicate that it has experienced the exsolution of Cl-bearing hydrothermal fluid. Higher Y/Ho and lower Zr/Hf in zircon from fertile porphyry indicate a stronger fluid activity than barren porphyry. The high S, V, As contents, δEu, low δCe in apatite, as well as high Ce⁴⁺/Ce³⁺ and log(fO₂) estimated from zircon geochemistry from fertile porphyry, indicate high a oxidation state of fertile porphyry, similar to other fertile porphyries in this metallogenic belt. High fluid activity and fluid exsolution are conducive to the migration and enrichment of metal elements, which are very important for mineralization. High oxygen fugacity inhibits the precipitation of metal in the form of sulfide, thereby enhancing the mineralization potential of rock. Therefore, the exsolution of Cl-bearing hydrothermal fluid and high oxygen fugacity are the key factors promoting mineralization in Yao’an area. Full article