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Garnet is the most common alteration mineral in skarn-type deposits, and the geochronological research on it can limit the mineralization age. The Longwan Pb–Zn deposit, situated within the Fozichong Pb–Zn ore field in Guangxi, lacks precise geochronological data, limiting the in-depth comprehension of its genesis and tectonic setting. This study employs LA-ICP-MS U–Pb dating of garnets developed in the skarn orebody and zircons in the associated granitic porphyry to determine the deposit's mineralization age. Backscatter electron images and electron probe microanalysis reveal common zonation characteristics in garnets from the Longwan Pb–Zn deposit, with dominant end-member compositions of Andradite and Grossular. The values of U concentrations range from 1.8 ppm to 3.7 ppm, and a garnet U–Pb age of 102.6 ± 1.9 Ma was obtained, consistent with the zircon U–Pb age of 102.1 ± 1.2 Ma from the granite porphyry within the deposit. The Longwan Pb–Zn deposit formed during the late Early Cretaceous as a skarn deposit resulting from contact metasomatism between the granite porphyry and the host rock. The deposit likely formed in response to the Neo-Tethys plate subducting beneath the South China continent during the Cretaceous, followed by a retreat during the Late Cretaceous. The Cenxi-Bobai Fault experienced reactivation under the extensional tectonic regime induced by the Neo-Tethys Ocean's retreat, leading to a series of magmatic activities along the NE-trending direction within the Fault. The Longwan Pb–Zn deposit formed during the processes of magma emplacement and contact metasomatic reactions with the country rock. [ABSTRACT FROM AUTHOR]

The Bawang deposit, located in the west of Wuxu ore field, southern section of the Nandan-Hechi metallogenic belt, is a medium-sized tin–zinc polymetallic deposit. Its genesis has been a matter of debate because of lacking constraints from isotope geology. In this study, LA-MC-ICP-MS U-Pb dating of cassiterite and C-O-S-Pb isotope analyses of monominerals were used to investigate the mineralization age and source of the ore-forming minerals in the Bawang deposit. LA-ICP-MS U–Pb dating of cassiterite yielded ages of 93.1 ± 4.8 Ma and 85.3 ± 6.3 Ma, indicating that the mineralization occurred in the early Late Cretaceous. The δ13CPDB and δ18OSMOW values of calcites at the ore stage range between −0.41‰ and 0.44‰ (average = −11‰) and between 13.8‰ and 15.40‰ (average = 14.59‰), respectively. This shows that ore fluid sources were a mixture of those derived from magma and stratum. Pyrite and sphalerite have uniform δ34S values (−4.45‰~−2.20‰), indicating that sulfur is also derived from the mixing of magmatic hydrothermal and stratum fluids. The Pb isotopic composition of sulfide (206Pb/204Pb = 18.4055~18.7625, 207Pb/204Pb = 15.6745~15.7209, 208Pb/204Pb = 38.6232~39.0370) is consistent with the granite of the same age, indicating that ore-forming metals are mainly derived from magmatic hydrothermal solution. The Bawang deposit is a hydrothermal vein-type deposit in the external contact zone of Late Cretaceous granite, controlled by tectonic fractures, and formed by the interaction of magmatic hydrothermal fluid and carbonate rock. There may be large skarn-type ore bodies in the deep part. The results of this study provide insights into the research and exploration of similar deposits in Nandan-Hechi metallogenic belt and in the Youjiang Basin. [ABSTRACT FROM AUTHOR]