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[Display omitted] • SIMS U-Pb dating of Jiama intrusives brackets magmatic event related to Jiama porphyry-skarn mineralization in 1.3 Myr. • Zircon O-Hf isotopic compositions suggest Jiama ore-forming magmas were derived from melting of the newly formed Tibetan lower crust. • No significant magma mixing has been observed during the magmatic evolution from diorite to granite. The post-collisional Gangdese metallogenic belt with over 45 Mt Cu has attracted worldwide attention. We report the whole-rock geochemistry, zircon SIMS U–Pb geochronology, and in situ zircon Hf–O isotopic compositions of the Jiama deposit in the Gangdese belt. The intermediate to the felsic intrusive rocks are characterized by high SiO 2 (64.8 to 78.8 wt. %) and Al 2 O 3 (12.1 to 16.3 wt. %) contents, high Sr/Y ratios (43–74), showing the geochemical characteristics of adakites. Zircons from four intrusives yield U–Pb ages of 16.19 ± 0.20 Ma, 15.67 ± 0.32 Ma, 15.44 ± 0.16 Ma, and 14.90 ± 0.16 Ma, respectively, which brackets magmatic event related to mineralization in 1.3 Myr (16.19 to 14.90 Ma). Magmatic zircons have intermediate δ18O (+5.21 to + 7.18‰), and depleted Hf isotopic values (εHf(t) = 1.8 to 9.4). In combination of whole rock, plagioclase, and zircon geochemistry, we suggest the main ore-forming magma was derived from the remelting of the newly formed lower crust. During the whole journey of magma ascending from lower crust to the surface, no significant injection or mixing of mafic melt from different source has been observed. This is supported by three lines of evidence: 1) There is no clear reverse zonation in plagioclase, 2) the major and trace element compositions of continuous lithologies from diorite to granite shows no significant mixing, 3) there is no significant change of the zircon O and Hf isotope among different intrusions. Our study suggests that the formation of the giant porphyry deposits such as Jiama in post-collisional setting likely form in a short-term (<1.5 Myr) without significant magma mixing during magmatic evolution from diorite to granite. [ABSTRACT FROM AUTHOR]

The tectono-magmatic history of the Lüchun-Jinping microblock and its possible affinity with the Yangtze Craton are important elements for the reconstruction of Cenozoic plate tectonics in southeastern Tibet. In order to constrain the affinity and decipher the pre-Cenozoic paleopositon of the Lüchun-Jinping microblock, we focused on the petrogenesis of Eocene-Oligocene lamprophyres in the Lüchun-Jinping microblock. The lamprophyres yield zircon U Pb ages of 34.7–33.3 Ma and exhibit potassic-ultrapotassic features with elevated K 2 O/Na 2 O (1.4–4.0) ratios. They are characterized by high concentrations of compatible elements (e.g., Cr = 187–692 ppm, Ni = 31–218 ppm), large-ion-lithophile elements and light rare-earth elements enrichment, high-field-strength elements depletion, and high radiogenic isotopic values, i.e. (87Sr/86Sr) i = 0.7063–0.7078 and εNd(t) = −3.9 to −2.4. Combined with the low Nb/U ratios, these features suggest that the lithospheric mantle source was metasomatized by subduction-related fluids beneath the Lüchun-Jinping microblock. The relatively high Rb/Sr ratios and high heavy rare-earth element contents indicate that these lamprophyres were derived from partial melting of a phlogopite-bearing lherzolite within the spinel stability field. The parental magmas have experienced fractional crystallization of olivine and clinopyroxene during emplacement. Comprehensive comparisons between the lamprophyres from the Lüchun-Jinping microblock and the potassic-ultrapotassic mafic rocks from the western Yangtze Craton indicate that the Lüchun-Jinping microblock can be regarded as a dismembered part of the western Yangtze Craton due to continental extrusion and Cenozoic sinistral displacement. The compositional trends of the potassic-ultrapotassic mafic rocks suggest that the palaeogeographic position of the Lüchun-Jinping microblock was near the Dali area (west of the Binchuan) and close to the Jinshajiang suture zone before the Cenozoic. [Display omitted] • Mafic lamprophyre dykes from the Lüchun-Jinping microblock were emplaced at 35–33 Ma. • Geochemical compositions of mafic lamprophyres reflect an enriched SCLM domain. • The enriched SCLM domain was metasomatized by Proterozoic subduction-related fluids. • The Lüchun-Jinping microblock is a displaced part of western Yangtze Craton. • The pre-Late Eocene position of this microblock was near Dali and closer to the JSSZ. [ABSTRACT FROM AUTHOR]