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[Display omitted] • This study first highlights the importance of melanite in-situ U-Pb geochronology. • Mineralization at the Mengya'a deposit is precisely identified at 55–52 Ma. • Ti-bearing andradites will potentially become an invaluable geochronological tool for skarn Pb-Zn deposits. Ti-bearing andradite (Ti-Grt) occurs in a variety of geological environments, such as Si-unsaturated igneous rocks, high-temperature metamorphic rocks, and contact-metasomatized skarns. This type of garnet remains stable throughout a wide range of pressure-temperature conditions. Abundant skarn Pb–Zn deposits, where the ore-related pluton is not exposed, have been discovered along the eastern Nyainqentanglha metallogenic belt, western China. However, the mineralization age of these skarn Pb–Zn deposits remains controversial. Therefore, in this study, petrography, geochemistry, and in-situ U–Pb geochronology of the Ti-Grt are investigated together with the Re–Os geochronology of the molybdenite in the large Mengya'a Pb–Zn deposit. The potential of Ti-Grt dating is explored and the age relationships between the skarn alteration and the Pb–Zn mineralization are constrained. The results show Ti-Grt samples from the Mengya'a deposit are brown-black in color with TiO 2 -rich (mean of 3.47 wt%) features. Laser ablation inductively coupled plasma mass spectrometry dating showed that these Ti-Grts have a U–Pb age range of 54.9–53.8 Ma, which is consistent with the ages of two adjacent molybdenite Re–Os models (53.36–52.86 Ma). This indicates that the skarn alteration is temporally associated with a Pb–Zn mineralization event during the Indian-Asian main-collisional orogeny. The positive linear Ti vs. U correlation of the Ti-Grts and other compiled data indicate that Ti-bearing garnets may have high contents of U. The incorporation of U and Ti in garnet is largely controlled by the crystal chemistry of garnet and the components of hydrothermal fluids in a nearly closed system. Thus, this study confirms the reliability and accuracy of in-situ U–Pb dating of Ti-Grt and emphasizes that Ti-bearing garnets can become an invaluable geochronological tool for magmatic, metamorphic, and hydrothermal mineral assemblages. [ABSTRACT FROM AUTHOR]

[Display omitted] • The element substitution of sphalerites is established in the Chapai deposit. • The metal source comes from the continental crust. • The fluid source is characterized by mixed feature of carbonate formation and magma. • The genesis of Chapai deposit is a Mississippi Valley-type (MVT) deposit. Chapai deposit is a special medium-sized carbonate-hosted Zn-Pb deposit (4.27Mt of sulfide ore with 8.15 % Zn, 3.44 % Pb, and 53.39 g/t Ag, as well as 0.82Mt of oxidized ore with 2.8 % Zn and 1.2 % Pb and 27.68 g/t Ag) with upper oxidized ore and lower sulfide ore of South China. Due to the shortage of detailed geological and geochemical constraints, the ore genesis of single stage magmatic hydrothermal mineralization or superposition of multi-stage mineralization remains unclear. Therefore, detailed geological and geochemical analyses of in-situ S isotopic compositions of sulfide and sulfate, trace elements of sphalerite, and ore Pb isotopic compositions were performed to decode the source and genesis of the Chapai deposit. Based on the investigation and microscopic observation, mineralization of the Chapai Zn–Pb deposit has obvious early hydrothermal alternation in the early hydrothermal sulfide stage (S1) and the late hydrothermal sulfide stage (S2) as well as the supergene oxidized mineralization stage (S3). The trace elements Cu, Ag, Ga, Sb, As and Ge are incorporated into S1 and S2 stages of sphalerite mainly through the following substitution mechanisms: Zn2+↔ (Fe2+, Cd2+),2Zn2+↔ (Ag+, Cu+) +(As3+, Ga3+, Sb3+), 3Zn2+↔ Ge4++2(Cu++Ag+), 4Zn2+↔(Cu++Ag+) + Sb3++Ge4++□(vacancy). In situ δ34S values of sulfides and sulfates are within a greater range (–3.0 to + 32.2 ‰), and are significantly higher in S2 compared to S1 stage, implying the mixing of two isotopically different end-members of hydrothermal fluids and wall rocks by sulfate reduction. The S isotope of sphalerite and galena crystallized in the early stage close to 0 ‰ may be controlled by magmatic-hydrothermal fluid source, while the increased S isotope in the late stage may be derived from the increased decomposition of organic matter and organic sulfate reduction (TSR). The Pb isotopic data (206Pb/204Pb = 18.355 ∼ 18.819, 207Pb/204Pb = 15.720 ∼ 15.778, and 208Pb/204Pb = 38.912 ∼ 39.222) indicate that the sources of metallogenic materials in the Chapai deposit are primarily upper crust basement rocks. The geothermometer studies of sphalerite in Chapai deposit show that it was generated from a medium–low temperature (142 ∼ 255 °C) condition. The low Zn/Cd ratios and high concentrations of Cd and Ge in sphalerite are in agreement with those of Mississippi Valley-type (MVT) deposits. Hence, the Chapai deposit was formed in a medium–low temperature magmatic- hydrothermal system and can be categorized as a MVT deposit within Nanling region (NR). [ABSTRACT FROM AUTHOR]

[Display omitted] • We focus on the oldest tin deposit in China using geology, geochemistry and geochronology methods; • Mineralization occurred between 851–844 Ma, corresponding to rift setting; • Sn-bearing granite is identified as originating from the reworking of Paleo- to Mesoproterozoic metasedimentary crust; • A high degree of differentiation is pivotal in facilitating the formation of tin-bearing granites; • This study highlights the significance of a metasediment-derived source and highly evolved, reduced, or ilmenite-series granitic magma in controlling the formation of granite-related Neoproterozoic tin mineralizations. The scarcity of Precambrian tin deposits in China has drawn significant interest to their formation. The Chahe tin deposit (26 Mt @ 0.38 % Sn), one of the oldest in China, provides a valuable opportunity to investigate the key factors controlling the development of such deposits. Situated along the western margin of the Yangtze craton in southwestern China, this deposit exhibits diverse mineralization types, including greisen cassiterite mineralizations located on top of the granitic cupola, skarn-cassiterite-axinite-quartz veins, and cassiterite-sulfide veins at the granite-limestone contact, and structurally controlled occurrences within siliciclastic metasedimentary rocks along secondary faults. Extensive U-Pb dating reveals that both barren and tin-bearing granites associated with the deposit share similar ages, ranging from 851 ± 4 Ma to 848 ± 4 Ma. These ages closely match, within error, the cassiterite U-Pb age of 843–853 Ma and the rutile U-Pb age of 859 ± 27 Ma for greisen veins/veinlets hosted in granite. Additionally, a cassiterite U-Pb age of 844 ± 9 Ma has been identified in the cassiterite–axinite–quartz veins hosted in the skarn. These findings provide direct evidence for the spatial, temporal, and genetic association of tin mineralization with Neoproterozoic Mosuoying granites. The granites in the region are categorized as peraluminous calc-alkali granites, characterized by high FeO, Ga/Al ratios, and zircon saturation temperatures, indicative of A-type granite features. In comparison to regional contemporaneous granites, the barren and tin-bearing granites exhibit high Rb/Ba and Rb/Sr ratios, variable ε Hf (t) values (–17.8 to + 3.1), and two-stage Hf model ages (T DM2) spanning from 2.6 to 1.5 Ga. These characteristics indicate a common source and origin through the reworking of Paleo- to Mesoproterozoic metasedimentary crust in response to the breakup of the Rodinia supercontinent. Simultaneously, they display low whole-rock Fe 2 O 3 /FeO and zircon Ce4+/Ce3+ ratios, consistent with those observed in typical Sn-bearing ilmenite-series granites globally. Notably, the tin-bearing granites manifest a highly fractionated nature, evident in their REE distribution patterns with a pronounced tetrad effect, as well as lower Nb/Ta and Zr/Hf ratios for twin elements. In summary, this study emphasizes the significance of a metasediment-derived source and the presence of highly evolved, reduced, or ilmenite-series granitic magma in the development of highly fractionated A-type granites associated with Neoproterozoic tin mineralization. These findings provide insights into the crucial factors controlling Neoproterozoic tin metallogenic events, shedding light on metallogenic processes and systematic exploration strategies for tin in Precambrian terranes. [ABSTRACT FROM AUTHOR]