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[Display omitted] • LA–ICP–MS U–Pb dating of cassiterite yielded a Tera-Wasserburg U–Pb lower intercept age of 99.2 ± 0.8 Ma. • A magmatic-hydrothermal origin was suggested by trace elements in cassiterite. • Sn and Ag–Pb–Zn mineralization are associated with the same magmatic-hydrothermal system. • Spatial relationship can be used as a mineral exploration indicator. Tin and (Ag)–Pb–Zn mineralisation generally co-exist in SEDEX, porphyry, skarn, greisen, as well as magmatic-hydrothermal Sn and/or Pb–Zn polymetallic deposits. The genetic relationship between these two styles of mineralization, however, is not well defined. More than 20 skarn and hydrothermal-vein-type Ag–Pb–Zn–Sn deposits can be found in the central Yidun Terrane (YDT) of southwestern China. Amongst these is the large Xiasai deposit, which contains 1028 t Ag @ 337.8 g/t, 0.27 Mt Pb + Zn @ 8.33 %, and 20,000 t Sn @ 0.75 %. The deposit is zoned, comprising proximal cassiterite-quartz veins and distal Ag–Pb–Zn veins. We present micro-textural studies, LA–ICP–MS U–Pb dating results, as well as cassiterite major and trace element data that served to better constrain the link between the Sn and Ag–Pb–Zn mineralisation at Xiasai. Two types of cassiterite, i.e., Cst I and Cst II, can be distinguished using cathodoluminescence (CL) imagery. Cst I has a dull luminesce and oscillatory zonation, and it has been partially replaced by Cst II, which has a bright luminesce and a homogeneous texture. Whistle the SnO 2 and TiO 2 contents of Cst I and Cst II are similar, the latter has slightly higher FeO compositions (from bdl to 0.08 wt% and 0.01 to 0.11 wt%, respectively). LA–ICP–MS U–Pb dating of cassiterite yielded a Tera-Wasserburg U–Pb lower intercept age of 99.2 ± 0.8 Ma (n = 39, MSWD = 1.8), identical to the ages of granitic magmatism and Ag–Pb–Zn vein formations. LA–ICP–MS trace element analyses revealed that cassiterite is enriched in Ti and W, but depleted in Fe, Mn, Nb, and Ta. The Zr/Hf ratios of cassiterite range from 4.7 to 15.8 and Ti/Zr ratios range from 1.8 to 6.2. Overall, the measured Fe, W, Nb, and Ta concentrations, as well as the calculated Zr/Hf and Ti/Zr ratios, indicate that the cassiterite-quartz veins at Xiasai have a magmatic-hydrothermal origin. Our findings, when combined with previous micro-thermometrical fluid inclusion data (423–481 °C for Sn and 158–386 °C for Ag–Pb–Zn mineralisation), suggest that Sn and Ag–Pb–Zn mineralisation was cogenetic and linked to a common magmatic-hydrothermal system. The spatial relationship between Cretaceous A-type granitic magmatism and Ag–Pb–Zn–Sn mineralisation in the central YDT can be used as a guideline for mineral exploration of both skarn and hydrothermal veins. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Giant Sb metallogenic belt in South China (GSMB) provides > 50% Sb production and reserves of the world. • Sb deposits in the GSMB are typically sedimentary-hosted and structurally controlled. • Sb deposits were mainly generated by low-temperature and low-salinity fluids. • Sb mineralization in the GSMB mainly occurred during 160–120 Ma. • Subduction of paleo-Pacific plate triggered Sb mineralization. The giant Sb metallogenic belt in South China (GSMB) has been proved to provide approximately half the world's reserves and Sb production. This metallogenic belt is tectonically located along the transition zone between the Yangtze and Cathaysia blocks, covering an area of ∼ 1900 km long and ∼ 200 km wide, with a set of large or giant Sb deposits such as the Xikuangshan, Banxi, Woxi, Qinglong, and Banpo-Banian. The Sb deposits have the following features in common: localisation in sedimentary rocks or counterpart metamorphic rocks as veins or strata, structural-tectonic control of mineralisation along the regional NE-trending faults, and the presence of intermediate-mafic dyke rocks in the belt whose relationship with Sb mineralisation is not obvious. Fluid inclusion data show that the Sb mineralisation in this belt generally occurred under low-temperature and low-salinity conditions (140–250 °C, 0.2%–10% NaCl equiv.). Abundant isotope data suggest that the Sb deposits in this belt were dominantly generated by crustal fluids from the Proterozoic basement sequences and fresh meteoric water or their mixture with various proportions, whereas the magmatic contribution to Sb mineralisation in this region is a preferential heat source rather than a material supplier (i.e., fluids and metals). The reported geochronological data of representative Sb deposits suggest an age distribution trend of Sb mineralisation, from 120 to 130 Ma in the Xikuangshan, Banxi, Woxi, Banpo and Banian Sb deposits in the northern and central parts of the GSMB, to 140–165 Ma in the Qinglong, Muli and Maxiong Sb deposits in the southern part of this belt. This age trend of the GSMB is largely comparable to that of Mesozoic igneous rocks in the Cathaysia Block, indicating both of them are the products of the west-northwestward flat-slab subduction and post-subduction of the paleo-Pacific Plate during the Late Mesozoic. In combination of the geological, geochemical, and reported geochronological data, we proposed that the Sb deposits in GSMB in South China probably have been mainly generated by low-temperature and low-salinity crustal fluids which leached Sb and S from basement sequences under an extensional setting during Late Mesozoic. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three stage Mesozoic magmatic activities in the DBO and the MLYRB almost in a similar duration. • Cu-Au mineralization is in the early stage for the MLYRB and Mo in the late stage for the DBO. • Three stage magmatic sources and their transformations are quite different for the two regions. • Broad continental arc and then back-arc for the MLYRB, and post-orogenic evolution for the DBO. • Magmatic source and physical–chemical condition, tectonic regime are key to mineralization. The Middle–Lower Yangtze River Belt (MLYRB) and the Dabie Orogen (DBO) are two contiguous tectonic units in which extensive late Mesozoic magmatism took place over similar time intervals. However, marked differences are observed in the geochemistry, lithology, and associated mineralization of the magmatic rocks of the two domains. Late Mesozoic magmatism in both regions can be divided into three stages (MLYRB: 148–133, 133–127, and 127–123 Ma; DBO: 143–130, 130–126, and 126–110 Ma). The MLYRB first-stage intrusions, which are closely genetically associated with Cu–Au polymetallic mineralization, are dominated by granodiorites characterized by higher Sr/Y ratios, arc-like trace-element distributions, moderately enriched Sr–Nd–Hf isotopic compositions, and higher radiogenic Pb isotopic values, indicating a mantle–crust mixed magma source. The mantle source was metasomatized by fluid and/or melt released from a subducted oceanic slab, and the crustal source was predominantly of Archean age, similar to late Archean to Paleoproterozoic basements in the MLYRB. However, the main metallogenic type in the DBO is Mo mineralization, whose ore-forming magmatic rocks are granites of the third stage of magmatism. The ore-barren magmatic rocks in the DBO are of the first and second stages of magmatism, with dominant rock types of adakitic granodiorite, andesite, and pyroxenitic or hornblenditic intrusions. In comparison, ore-forming rocks in the DBO show low Sr/Y ratios, less enriched Sr–Nd–Hf isotopic compositions, low radiogenic Pb isotopic values, and enriched light rare-earth element and large-ion lithophile element contents, which are geochemical signatures similar to those of the middle–upper crust represented by gneisses in the northern and central DBO. Separate tracing of the evolution of magmatic sources and deep processes of the two tectonic units during the three stages suggests that late Mesozoic magmatic activity in the MLYRB took place in a continental-arc geodynamic setting during the first stage, then transformed to a back-arc after the second stage. Northward flat subduction of the paleo-Pacific plate, followed by slab foundering and roll-back, provided not only the dynamic mechanism for the magmatism, but also a substantial material contribution. In contrast, late Mesozoic magmatic activity in the DBO, caused by an Indosinian continent–continent collisional orogen, occurred in a back-arc post-orogenic geodynamic setting, with orogenically thickened lithosphere preventing flat subduction. Subduction of the paleo-Pacific plate supplied the dynamic mechanism, but no material contribution to the magmatism of the DBO. A torn slab window formed along the present coordinates of the Yangtze River, corresponding to the Yangtze River fault, in the effect of sinistral shear of the Tan–Lu fault, a subordinate triggering dynamic setting for magmatism in the MLYRB. An integrated comparison of the two metallogenic belts suggests three key controls on metallogenic type: (1) Metal elemental abundance in the magma source was the first-order control on the minerogenetic series; (2) the physical–chemical conditions of the magma controlled the migration of metal elements from the source and incorporation into the metal-rich magma; and (3) the late Mesozoic tectonic regime exerted a broad influence on the generation of the different minerogenetic series. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Beimulang is a newly discovered porphyry Cu deposit in the Gangdese belt. • There are at least two episodes of fluid exsolution events of granites at Beimulang. • The highly oxidized and hydrous magmas are crucial to form porphyry Cu deposits. The porphyry Cu deposits in the Gangdese metallogenic belt were mainly formed in the eastern portion. The Beimulang is a newly discovered deposit formed in post-collisional setting in the western part of the belt and adjacent to the super-large Zhunuo porphyry Cu deposit. There are three epochs of magmatism at Beimulang, including pre-mineralization quartz porphyry (PQP; 49.7 ± 0.4 Ma), inter-mineralization monzogranite porphyry (IMGP; 14.8 ± 0.2 Ma), monzogranite (IMG; 14.1 ± 0.2 Ma), and late-mineralization granite porphyry (LGP; 11.7 ± 0.1 Ma). The various degrees of alteration and sulfide occurred at the IMG(P) and LGP indicate that there are at least two episodes of fluid exsolution events associated with different intrusions spanning ∼ 3 m.y. at Beimulang, which are unlike other Gangdese porphyry Cu deposits showing single fluid exsolution around only one porphyry at Miocene (e.g., Qulong, Zhunuo, Dabu). The PQP is characterized by high SiO 2 (75.6–81.4 wt%) and K 2 O (2.1–4.3 wt%) concentrations, high Nb/Ta (8.4–11.3) ratios, and low Mg# (22–43), Ni (1.5–2.7 ppm) contents. They have high (87Sr/86Sr) i (0.705098–0.707767) ratios and low ε Nd (t) (-4.9 to −1.9) values. These geochemical characteristics indicate that they were probably derived from a juvenile basaltic lower crust during the ongoing Indian-Asian collision. The IMGP and IMG show similar petrography and geochemical characteristics, such as high SiO 2 (65.0–69.8 wt%), K 2 O (3.6–4.3 wt%), Sr (550–809 ppm) contents, high Sr/Y (79–89) ratios, and low Mg# (43–48), Th/Yb, and Nb/Yb values, combined with high (87Sr/86Sr) i (0.707254–0.708017) and low ε Nd (t) (-7.9 to −6.0), implying a similar source probably originated in the subduction-modified lower crust metasomatized by Neo-Tethyan oceanic slab-derived fluids. The LGP displays trends produced by fractionation of magma with a composition similar to the IMG(P), but wall rock assimilation plays a significant role during magmatic evolution. Zircons from the IMG(P) show higher Eu/Eu* (>0.3), 10000*(Eu/Eu*)/Y (>4), and (Ce/Nd)/Y (>0.04) ratios than those of the PQP, indicating the fertile magmas were more oxidized and hydrous. The high magmatic oxidation state for the IMG(P) is also supported by using the zircon (ΔFMQ = +4.1 to + 6.1), and amphibole (ΔFMQ =+2.6 to + 3.4) oxybarometers. Their high magmatic water contents are supported by evaluations using amphibole (∼3.5 wt%) and plagioclase (∼6.7 wt%) compositions, respectively. However, the LGP has higher magmatic oxygen fugacity (Eu/Eu* >0.3, ΔFMQ = +4.2 to + 7.3) caused probably by auto-oxidation of the magmas, but lower magmatic water contents (Sr/Y = 31 ± 15; V/Sc = 6 ± 4) caused presumably by previous fluid exsolution and/or fractionation of hydrous silicate minerals during magma ascent than those of the IMG(P). Therefore, the highly hydrous and oxidized magmas with juvenile material are favorable to form porphyry Cu deposits in Tibetan orogen. On the contrary, magmatic evolution can probably reduce the water content of magma chamber, which is not beneficial to porphyry Cu mineralization. [ABSTRACT FROM AUTHOR]

[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]

The parental magmas of the Cilincuo, Rongyicuo and Hagela plutons are less oxidized (a) and contain less H 2 O and Cl (b) than those associated with typical porphyry Cu-Mo mineralization. [Display omitted] • Zircon U–Pb ages of the three Cu–Mo barren plutons range from 98 to 86.1 Ma. • There are different magma oxidation states and H 2 O–Cl contents between the three Cu-Mo infertile plutons. • The Cu–Mo infertility of the three plutons is related to the low H 2 O–Cl content and oxygen fugacity in the causative magmas. The Yidun Cu-Mo polymetallic metallogenic belt, located in the eastern Tibetan Plateau, is well known for numerous Mesozoic porphyry Cu–Mo deposits. The Cu-Mo deposits are only concentrated in the southern part of the belt while the granites situated in the north are generally barren in Cu-Mo mineralization. To understand the cause of Cu and Mo infertility, geochronology and petro-mineral geochemistry of three Cu- and Mo-barren granite plutons (Cilincuo, Rongyicuo, and Hagela) in the Northern Yidun Terrane were investigated. Petrogeochemical characteristics and zircon U-Pb dating (95–85 Ma) along with the tectonic evolution history confirmed that the three plutons formed in a Late Cretaceous intracontinental setting. The whole-rock geochemical compositions showed that these plutons can be classified as A-type granites and have undergone extensive magmatic differentiation. Based on the calculated magmatic oxygen fugacity using zircon composition and a set of geochemical criteria including whole-rock Sr/Y ratios, Eu/Eu* and Fe3+/Fe2+ values as well as apatite Cl-H 2 O contents, the parental magma of the Cilincuo pluton was identified as more oxidized and H 2 O-Cl-rich than those of the Rongyicuo and Hagela plutons. These features enable the Cilincuo pluton to have an elevated capacity of Cu mineralization compared to the other two plutons. However, the causative magmas of the three plutons are still not enough hydrous and oxidized for typical porphyry Cu ± Mo mineralization. The whole-rock Sr-Nd isotope values of these three plutons are consistent with Late Triassic Cu and Mo barren granites in the same region such as Dongcuo, Cuojiaoma and Sucuoma, suggesting that they were derived from a similar magma source which might lack the oxidized and hydrous Neoproterozoic arc root remnant. [ABSTRACT FROM AUTHOR]