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We report zircon U Pb age and Hf isotope and whole-rock major and trace element and Sr Nd isotope data for magnesian andesites from the Kongnongla area, central Tibet. These Kongnongla magnesian andesites are directly in contact with high-Nb basalts and are part of the Baila–Lanong ophiolitic mélanges. Zircon U Pb dating shows that the magnesian andesites crystallized at ca. 158 Ma. The samples are characterized by moderate SiO 2 (59.3–61.7 wt%), high MgO (3.74–4.69 wt%), Fe 2 OT 3 (4.95–5.30 wt%), Ba (570–1320 ppm), and Th (6.5–7.0 ppm) contents, and low (87Sr/86Sr) i (0.704491–0.704857), and Sr/Y (17.5–24.0) ratios. The samples also exhibit enrichments of compatible elements, such as Cr (110–150 ppm) and Ni (24.7–36.5 ppm), and display fractionated rare earth element (REE) patterns with light REE enrichment relative to heavy REEs. Negative zircon ε Hf (t) values (−10.8 to −15.7) and whole-rock ε Nd (t) values (−3.85 to −6.12) of the Kongnongla magnesian andesites are similar to those of DaruTso magnesian andesites, Hohxili high magnesian andesites, and sediments of the Mugagangri Group. We propose that the Kongnongla magnesian andesites were formed by the interaction between slab fluids, subducting sediments, and overlying mantle under high-temperature–low-pressure conditions. Based on previously published data and the regional geology, we also suggest that these magnesian andesites were generated in a back-arc setting caused by the southward subduction of the Bangong–Nujiang oceanic lithosphere during the Late Jurassic. • The Dongqiao area is a microcontinent preserved in the Bangong–Nujiang suture. • The Kongnongla magnesian andesites formed in a back-arc setting. • Southward subduction of the Bangong-Nujiang Ocean triggered back-arc spreading. [ABSTRACT FROM AUTHOR]

• The host volcanic rocks of the Sinongduo Ag–Pb–Zn deposit erupted at approximately 61.9 Ma. • The sphalerite rich in Ag, In and Cd is a kind of Fe-poor sphalerite that is commonly found in IS epithermal deposits. • The Sinongduo Ag–Pb–Zn deposit is an IS epithermal deposit rather than a LS epithermal deposit. The Sinongduo Ag–Pb–Zn deposit was first defined as a typical low sulfidation (LS) epithermal deposit in the widespread Linzizong volcanic succession (LVS), Gangdese belt, Tibet. This paper we describe the lithology, mineralization, and hydrothermal alteration based on current advances in exploration, and use multiple chemical and geochronology methods, including whole-rock geochemistry (major and trace elements) of ores and the lithocap, the mineral chemistry of sphalerite, and the LA–MC–ICP-MS zircon U–Pb dating of host volcanic rocks to better constrain the genesis of the Sinongduo deposit and give some exploration advice. In the Sinongduo deposit, the host crystal tuff yields a zircon U–Pb age of 61.9 ± 0.4 Ma, indicating nearly simultaneous diagenesis and mineralization. The metallic minerals are mainly FeS-poor sphalerite, galena, pyrite, and minor chalcopyrite, along with silver and silver-based precious minerals. These minerals, particularly FeS–poor sphalerite, pyrite, and chalcopyrite, represent IS states. Mineral chemistry shows that the content of FeS in sphalerite is lower than 4.94 mol% and the Ag concentration is quite high, ranging from 16 to 1798 ppm with a mean concentration of 245 ppm. Low Ga/in ratios (<1) and enrichment of In and Sn in sphalerite imply that the ore-forming fluid is dominated by magmatic water with intermediate temperature. Gangue minerals include the silicic group (quartz and chalcedony), carbonates group (calcite, siderite, ankerite, etc.), and hematite. Alterations, including illite, montmorillonite, and sericite, are widely distributed. The results suggest that the Sinongduo deposit is not a LS epithermal deposit but a typical IS epithermal deposit and we believe that there is potential for Au and Ag exploration. [ABSTRACT FROM AUTHOR]