Rhyolites with high Nb–Ta contents were recently discovered in the north Daxingan Mountains, China. We determined the geochemical characteristics and zircon U–Pb ages of these rhyolites to elucidate their tectonic setting of formation and petrogenesis. Zircons from the high Nb–Ta rhyolites are idiomorphic or hypidiomorphic, short prismatic crystals with oscillatory zoning; the zircon trace element has a higher Th/U ratio (> 0.4); zircon rare earth element (REE) content is high (average is 1729 × 10⁻⁶) and indicates heavy REE (HREE) enrichment (average is 1561 × 10⁻⁶) and shows positive Ce (Ce/Ce* = 2.1–103.4) and negative Eu (Eu/Eu* = 0.18–0.64) anomalies typical of crustal magmatic zircons. Their weighted-mean LA–ICP–MS U–Pb age of 155 ± 1 Ma indicates that they formed in the Upper Jurassic. The rhyolites are characterized by high SiO₂ and alkali contents and low Fe, Ca, Mg, and Mn contents, and are weakly peraluminous, indicating that they are high-K calc-alkaline rocks. Trace element compositions are characterized by enrichments in Nb, Ta, Zr, Hf, Ce, and Rb and depletions in Sr, Eu, Ba, P, Ti, Co, and Ni, with significant positive Ce (Ce/Ce* = 2.4–2.7) and negative Eu (Eu/Eu* = 0.06) anomalies. Niobium and Ta are hosted in the zircons. In (Na₂O+K₂O+FeO^T+MgO+TiO₂) vs (Na₂O+K₂O)/(FeO^T+MgO+TiO₂) and (Al₂O₃+FeO^T+MgO+TiO₂) vs Al₂O₃/(FeO^T+MgO+TiO₂) mineral characterization diagrams, data for the samples plot in the metamorphic greywacke or basic argillaceous rock fields, indicating that the magma originated from partial melting of crustal material. εSr(t) values cover a wide range (− 18.2 to + 102.9), whereas εNd(t) values have a narrow range (1.9–2.0) with T_2DM model ages of 789–785 Ma, indicating that the source was the Neoproterozoic Xinghua Ferry Group crustal basement. This crustal rock suite comprises a volcanic–sedimentary formation of metamorphosed mafic volcanic and terrigenous clastic rocks derived from a mixture of mantle and crustal materials. Residual phases in the source region include Ca-rich plagioclase, amphibole, orthopyroxene, and zircon + garnet. Together with the positive Ce anomalies and low-Sr/high-Yb characteristics of the rhyolites, this indicates that the source rocks melted at relatively shallow depths (< 30 km), low pressures (< 0.8 GPa), and high O₂ fugacity. Ga × 104/Al > 2.6, Ta vs Yb, and (Rb/30) vs Hf vs (3Ta) discrimination diagrams, data for the samples plot in the A-type rhyolite and intraplate granite fields, whereas in the Nb vs Y vs Ce diagram, the data plot in the A1-type field. It is concluded that an extensional tectonic setting, resulting from closure of the Mongolia–Okhotsk Ocean at the end-Triassic, or northward subduction of oceanic lithosphere under the Siberian Plate, caused underplating of mantle-derived basaltic magma and partial melting of metamorphic crustal rocks.

There continues to be debate regarding the timing of the collision between the Indian and Eurasian plates and the uplift of the Tibetan Plateau. This study presents zircon U–Pb geochronology, whole-rock geochemistry, and Lu–Hf isotopic data for the Saiduopugangri granite of the Qiangtang Terrane, located within the core of the Tibetan Plateau. These data provide the basis for the geodynamic setting, petrogenesis, and characteristics of its magma source. Zircons from the Saiduopugangri granite yield a weighted-mean ²⁰⁶Pb/²³⁸U age of 62.72 ± 0.06 Ma, indicating that these rocks formed during the early Palaeocene. The rocks are members of the highly calc-alkaline to shoshonitic series, with weak peraluminous characteristics. Trace elements are characterised by high Sr (483–616 ppm), and low Y (6–10 ppm) and Yb (1 ppm) content, typical of a high Sr and low Yb granite. The ε_Hf(t) of zircon ranges from −2.14 to 2.35, with two-stage Hf model ages (T_DM2) ranging from 1182 to 895 Ma. These data suggest that the Saiduopugangri granite magma was derived from the melting of lower-crustal clastic meta-sedimentary rocks and mantle-derived basalts. The high Sr and low Yb granite characteristics and experimental results indicate that melting occurred at >1.2 GPa and >750 °C, consistent with a crustal thickness greater than 50 km. Magmatism occurred from the Late Cretaceous to the early Palaeogene and is broadly synchronous with the collision timing between the Indian and Eurasian plates. The Saiduopugangri granite provides evidence of crustal thickening of the Tibetan Plateau and its age and petrogenesis constrain the timing of the initial uplift.

Seamount basalts undergoing long-term seawater immersion and percolation are subject to varying degrees of low-temperature alteration, causing a release of substantial amounts of Sr-Nd-Pb-Hf into seawater and thereby providing a sustained, long-term, mantle-derived source for marine material cycling. Such a mantle input mixes with crustal weathering material settled to the ocean via rivers and aeolian dust, resulting in crust-mantle mixing, altogether constraining the Sr-Nd-Pb-Hf isotopic compositions of seawater and polymetallic crusts. Among these, the isotopic compositions of Sr and Pb more closely resemble those of terrigenous input materials, while Nd isotopes indicate a roughly averaged mixing mechanism. The Hf isotopic composition approaches that of enriched mantle-derived Ocean Island Basalts (OIBs). Low-temperature-altered minerals in basalt, such as montmorillonite and phillipsite, possess both permanently negative and variable charges. This causes the formation of an electrostatic field, resulting in an adsorptive potential that facilitates the initial growth of charged Fe and Mn colloidal particles on the surfaces of altered basalt. Simultaneously, Fe, Mn, Co, Ni, and Rare-Earth Elements (REEs) released during the low-temperature alteration process contribute essential material for the growth of a polymetallic crust.

This text systematically investigates the Laotudingzi monzogranite (a gold-hosting intrusion) and the Dongbaligou gold ore deposit in the Laoling gold ore belt through comprehensive geochronological, whole-rock geochemical (macroelement and microelement), strontium-neodymium-lead-hafnium isotopic and in situ sulfur-lead isotopic analysis of pyrite, combined with hydrogen-oxygen isotopic studies of hydrothermal quartz. The results demonstrate a significant Early–Middle Jurassic magmatic-mineralization event in southern Jilin Province (Ji’nan). The gold mine is structurally controlled by detachment fractures within the Laoling metamorphic core complex, which developed in an extended environment. The metallogenic materials are primarily derived from adakitic magma, supporting a “decratonic-type” genetic model. By integrating geochronological, geochemical, and isotopic datasets from the ore-related intrusions and gold deposits, as well as fluid inclusion characteristics, we elucidate the metallogenic mechanism linking Jurassic gold mineralization to subduction-related cratonic destruction. The process involved lower crustal thickening induced by Paleo-Pacific Plate subduction, lithospheric destabilization via gravitational foundering and delamination, and syn-extensional magmatism that sourced ore-forming fluids during cratonic lithosphere thinning. This work establishes a genetic framework connecting plate subduction, lithospheric removal, and gold endowment in convergent margin settings.