Two phases of high potassic-shoshonitic magmatism and coeval Sn polymetallic mineralization in the Bozhushan orefield, southwestern China

• Bozhushan pluton consists of granodiorites and monzogranites and is high potassic-shoshonitic and peraluminous. • Zircon, monazite and apatite age data indicate two intrusive phases. • Metallogenic evolution increases in order of the granodiorites and monzogranites. • Neotethys subduction resulted in two-period magmatic-metallogenic process. The Cretaceous granitoid magmatism in the Gejiu-Bozhushan-Laojunshan region records tectonic transitions from the Neotethys to the South China Block and is genetically linked to Sn-polymetallic mineralization. However, the tectonic settings of magmatism and metallogeny remain unclear, particularly in the Bozhushan orefield. Integrated whole-rock geochemistry, Sr-Nd-Pb isotopes, zircon U-Pb-Hf-O isotopes, monazite U-Th-Pb-Nd isotopes, apatite U-Pb-REE data from the Bozhushan pluton, and cassiterite U-Pb dating from three Sn-polymetallic deposits are presented to understand the crustal architecture and tectonic-magmatic-metallogeny. The pluton consists of six interdigitated units characterized by high potassic-shoshonitic and peraluminous compositions, which are further subdivided into two magmatic stages: (1) Rim-located granodiorites (Units 1‒3, 91‒90 Ma, Stage I): I-type, characterized by the presence of biotite + K-feldspar + plagioclase, and featuring high Sr/Y, (La/Yb) N , and LREE-enriched apatite. They likely originate from lithospheric mantle melting during eastward Neotethys subduction, which triggered crustal melting and is linked to peripheral Ag-Pb-Zn-W polymetallic mineralization (ca. 91‒89 Ma, defined as Phase I magmatic-metallogenic event). (2) Core-located high evolved monzogranites (Units 4‒6, 87‒86 Ma, Stage II): S-type, containing muscovite + K-feldspar + plagioclase ± tourmaline, with LREE-depleted apatite, higher SiO 2 and Rb/Sr, derived from the low-pressure partial melting of Neoproterozoic biotite-rich metagreywackes in the shallow crust during ongoing Neotethys subduction-induced collision, associated with Sn-dominated mineralization (87‒80 Ma, defined as Phase II magmatic-metallogenic event). Geochemical and Isotopic trends suggest mantle-crust interaction during Stage I and crustal recycling during Stage II, both driven by the ongoing subduction of Neotethys. This dual-stage magmatism establishes a dynamic model in which tectonic processes control magma sources, isotopic signatures, and metal partitioning, providing key insights into granite-related Sn polymetallic mineralization in the Bozhushan orefield.