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[Display omitted] • The ore-forming fluid is a mixture of magmatic fluid and meteoric water. • The ore-forming fluid was derived mainly from crustal source, with minor proportions of mantle source input (<4.28%). • Fluid boiling and mixing with meteoric water were considered likely to be the possible mechanism for the ore precipitation in Tashan deposit. The Tashan deposit is hosted and genetically associated with the highly fractionated A-type granite porphyry formed at ca. 138 Ma. Its Sn metallogenic processes can be subdivided into three stages: biotite–K-feldspar–cassiterite (stage I, main Sn mineralization), quartz–cassiterite (stage II), and chlorite–sulphides (stage III). Fluid inclusion study indicates that the hydrothermal fluids from stage I (salinity = 5.2–12.8 wt%, and T h = 303–376 °C) through stage II (salinity = 2.7–10.9 wt%, and T h = 236–313 °C) to stage III (salinity = 1.7–8.5 wt%, and T h = 192–262 °C) are of H 2 O–CO 2 –salt composition and its temperature and salinity from early to late stages tend to decrease. The H and O isotopes of quartz from stage II and stage III show δD water values in the range of –66.7 to –60.5‰ and –52.8 to –39.6‰, and δ18O (‰) values in the range of 6.7 to 7.3‰ and 5.8 to 6.9‰, respectively, suggesting contributions of both magmatic fluids and meteoric water. Inclusion-trapped fluids in stage II pyrite show 3He/4He, He mantle (%), and 40Ar/36Ar values of 0.07–0.35 Ra, 0.76%–4.28%, and 302.6–309.0, respectively, indicating that the metallogenic fluids were derived mainly from crustal sources, with minor proportions of mantle source input (<4.28%), consistent with the magma sources of the granite porphyry. Lead isotopes indicate that there is no difference for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios between the sulfide minerals from the orebodies and the fertile granites parental to Sn mineralization in Eastern Guangdong, indicating a magmatic Pb origin. Sulfur isotopic values obtained from sulfides are in the range of –4.5‰ to 0.4‰ (average, –1.7‰), implying an initially of magmatic origin with some contamination of sedimentary sulfur through the interaction with sedimentary rocks of Jinji Formation (–6.67 to –2.41‰). Fluid boiling and mixing with meteoric water were considered likely to be the possible mechanism for the ore precipitation in Tashan deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mineralization at Tashan is related to the granite porphyry, and both of them formed at ca. 138 Ma. • The granite porphyry is an A-type granite mainly produced from partial melting of crust with minor contribution of mantle materials. • Both the granite porphyry and the mineralization formed in an extensional setting induced by slab roll-back. The medium-sized Tashan Sn deposit, mainly hosted in the Tashan granite porphyry, is located in eastern Guangdong, Southeast China. Zircon U–Pb dating of the granite porphyry yielded a concordant age of 138.0 ± 1.1 Ma, which is consistent with the cassiterite U–Pb age of 138.0 ± 2.3 Ma from the Sn ores, indicating a temporal link between the emplacement of granitic pluton and Sn mineralization. The contents of Fe3+, Fe2+, and Mg2+ in biotite, low calculated zircon Ce4+/Ce3+ of 4.4–71.6, low Eu/Eu* ratios of 0.06–0.35, and low whole-rock Fe 2 O 3 /FeO of 0.04–0.13 of the granite porphyry reveals its low oxygen fugacity, which may have facilitated the Sn enrichment during magma evolution and played a key role in the Sn mineralization. Low K/Rb (150–175, aver. = 160), Nb/Ta (7.3–8.2, aver. = 7.8), and Zr/Hf (23.2–25.1, aver. = 23.9) values were observed for the granite porphyry, indicating its high fractionation and probable interaction with an aqueous fluid phase to some extent. The reduced and highly fractionated features and high F and Sn contents of the granite porphyry thus indicate it is a typical Sn-fertile granite. The granite porphyry is weakly peraluminous and belongs to high-K calc-alkaline type. The rocks are characterized by high SiO 2 , K 2 O + Na 2 O, F, and Zr + Nb + Ce + Y (360–410 ppm) contents; and 10000 Ga/Al (2.31–3.06) ratios and low CaO, MgO, TiO 2 , and P 2 O 5 contents; Rb, Cs, Th, and U enrichment; and Ba, Sr, Zr, Ti, and P depletion, exhibiting an A-type affinity. Moreover, the rocks display whole rock initial 87Sr/86Sr values of 0.70927–0.71218, εNd(t) of − 6.5 to − 6.3, and zircon εHf(t) values from − 5.7 to − 1.5 with Mesoproterozoic T DM2 ages for both Nd and Hf isotopes, indicating their formation by partial melting of a crustal source of Mesoproterozoic overall residence ages with minor input of mantle materials. By integrating new and published data on tectonic evolution, we suggest that the granite porphyry and associated Sn mineralization in the Tashan deposit that was formed in a back-arc extensional environment started before ∼ 141 Ma, related to the rollback of the paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

• Two pulses of magmatic-hydrothermal fluid are documented in Taoxihu deposit. • The first pulse of fluid is H 2 O-CO 2 -NaCl system and the second one is H 2 O–NaCl. • Fluid immiscibility is responsible for the precipitation of Sn during the first pulse. • The oxidizing process due to the influx of meteoric water accounts for the precipitation of Sn during the second pulse. The Taoxihu deposit is a newly discovered Sn-polymetallic deposit in eastern Guangdong, SE China. The mineralization is related to an Early Cretaceous, highly fractionated I-type granite porphyry. The ore-forming process is divided into six stages, i.e., garnet (stage I), quartz–fluorite–biotite (stage II), quartz–biotite–cassiterite–sulfides (stage III, main mineralization), quartz vein with minor sulfides and cassiterite (stage IV), quartz–K-feldspar–biotite–cassiterite–sulfides (stage V), and quartz–K-feldspar–chlorite–sulfides (stage VI). Fluid inclusion study shows that the hydrothermal fluids from stage II (salinity = 5.9 to 13.2 wt%, and T h = 302 to 382 °C) to stage IV (salinity = 0.2 to 5.9 wt%, and T h = 275 to 315 °C) are of H 2 O–CO 2 –(CH 4)–salt composition and show a trend of systematically decreasing temperature and salinity from early to late stages. In contrast, the fluids in stage V (salinity = 6.5 to 13.9 wt% and T h = 223 to 343 °C) and stage VI (salinity = 6.0 to 11.8 wt%, and T h = 140 to 300 °C) are of the H 2 O–salt compositional system, and demonstrate also a trend of decreasing temperature and salinity with time, representing a distinct hydrothermal event. H–O isotope data indicate that these two different fluid systems are all initially of magmatic origin. In view of the almost identical cassiterite U–Pb ages of stage III (139.7 ± 1.1 Ma) and stage V (139.8 ± 1.6), the two hydrothermal events are interpreted to represent two pulses of magmatic fluid releasing from the same magma chamber. The first pulse is characterized by an initially single-phase CO 2 -bearing magmatic fluid that was subsequently subject to unmixing or phase separation in relation to hydraulic fracturing and decompression, which lead to the main phase mineralization, whereas the second pulse is the release of residual, CO 2 -free magmatic fluid, which mixed with meteoric water and resulted in the second phase of mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • We firstly reported the ore ages of the newly discovered Li-rich pegmatite in the NQT. • The newly discovered pegmatites have similar ages to the pegmatite in the MYK. • The pegmatites in the NQT may be formed in a continental collision setting. Lithium–(beryllium) are important strategic metals in modern industries. The Markam–Yajiang–Karakoram (MYK) giant Li ore belt (>14 Mt Li 2 O) is located in the central Qinghai–Tibetan Plateau, and is a world-class Li deposit belt. The reported pegmatite deposits in the belt are mainly found in the Tianshuihai–Songpan–Garzê Terrane (TSGT) and are generally considered to be related to Late Triassic S-type granites and flysch sedimentary rocks. Recently, abundant pegmatite veins have also been discovered in an adjacent terrane (i.e., the North Qaidam Terrane) to the north of the MYK belt, but it is unclear whether these newly discovered pegmatites are genetic related to the MYK belt. Here, we report high-precision columbite–tantalite (i.e., coltan) U–Pb ages and muscovite–lepidolite 40Ar/39Ar ages for the Li–(Be) rare-element pegmatites from the North Qaidam Terrane (NQT) in the Chakabeishan area of the Zongwulong orogenic belt. Coltan grains from three spodumene-bearing pegmatite samples yielded weighted-mean 207Pb-corrected U–Pb ages of 214.9 ± 1.7, 217.0 ± 2.3, and 215.0 ± 1.5 Ma. Muscovite 40Ar/39Ar dating of two spodumene-bearing pegmatite samples and one barren pegmatite sample yielded plateau ages of 213.00 ± 0.97, 211.67 ± 0.35, and 211.78 ± 0.29 Ma, respectively. A lepidolite 40Ar/39Ar age for a lepidolite-bearing pegmatite is 216.62 ± 0.88 Ma. The subtle age differences obtained by the different methods are within reasonable error estimates or may be due to different closure temperatures. The ore-forming ages of the Chakabeishan Li–(Be) rare-element pegmatites are similar to those of Li–(Be) pegmatite deposits in the MYK belt. This and data from previous studies suggest that the Chakabeishan Li–(Be) rare-element pegmatites were also formed in a post-collisional setting after the closure of the Paleo-Tethys (Anyemaqen) Ocean. This study has important implications for understanding the origins of the MYK Li ore belt, indicating that the formation of these Li deposits was not solely associated with the Late Triassic S-type granites and flysch sedimentary rocks. Our results may also have implications for exploration, which extends the potential area of Li deposits from the Tianshuihai–Songpan–Garzê Terrane to the North Qaidam Terrane. [ABSTRACT FROM AUTHOR]

• Akesayi magnetite was occurred mainly during the retrograde skarn and oxide stages. • Akesayi comprises of banded (BO), disseminated (DO), primary (MO-1) and secondary massive (MO-2) magnetite. • Variable magnetite compositions controlled by multiple factors. • Magnetite compositions in skarn deposits are more variable than previously thought. The Akesayi skarn iron (Fe) deposit is hosted by the Huangyangling Group within the Tianshuihai Terrane of the Western Kunlun orogenic belt, Xinjiang, China, and consists of several orebodies that formed along contacts between Miocene syenogranite, diorite porphyry dykes and late Paleozoic carbonate rocks. Manganese-bearing skarn minerals are common within the deposit. The ore-forming process can be divided into five stages: Prograde skarn stage (I), retrograde skarn stage (II), oxide stage (III), quartz-sulfide stage (IV), and carbonate stage (V), with this evolution being typical of Fe skarns. Magnetite, which formed mainly during the retrograde skarn and oxide stages, includes banded (BO), disseminated (DO), and massive (MO) magnetite. Backscattered-electron images indicate that magnetite within the massive ores can be further classified as primary (MO-1) and secondary (MO-2) magnetite. Magnetite within all ore types exhibits a strongly negative correlation between Si and Fe3+ contents, indicating that Si was incorporated into intra-crystalline sites of magnetite by substitution of Si4+ for Fe3+. Positive correlation among Al, Mn, Mg, and Si contents indicate that these elements behaved similarly during magnetite formation. The δ18O V-SMOW values of MO-1 magnetite range from 4.3‰ to 4.7‰, higher than magmatic magnetite (1‰–4‰), while the BO and DO magnetite have lower δ18O V-SMOW values of 1.7‰ to 2.4‰ and 1.8‰ to 2.5‰ respectively. Its anomalous oxygen isotopic composition indicates that most magnetite in the Akesayi Fe deposit precipitated from evolved ore-forming fluids formed by reaction between country rocks and primary magmatic fluids during the early stages of mineralization, with input from meteoric water during the later stages of mineralization. Trace-element patterns indicate that the different types of magnetite share a common source, with variations in the magnetite geochemistry amongst the different ore types of the Akesayi Fe deposit reflecting variations in the extent of fluid-rock interaction, dissolution-reprecipitation, mineral precipitation, temperature, and oxygen fugacity (ƒO 2). The different types of magnetite of the Akesayi skarn Fe deposit form distinguishable populations in (Ca + Al + Mn)-(Ti + V) and (Ni/(Cr + Mn))-(Ti + V) discrimination diagrams, with the range of compositions possibly indicating more variable magnetite compositions in skarn deposits than previously thought. [ABSTRACT FROM AUTHOR]