Pre-Late Eocene position of the Lüchun-Jinping microblock in western Yangtze Craton: Constraints from Eocene-Oligocene lamprophyres in southeastern Tibet

The tectono-magmatic history of the Lüchun-Jinping microblock and its possible affinity with Yangtze Craton are important elements for reconstruction Cenozoic plate tectonics in southeastern Tibet. In order to constrain decipher pre-Cenozoic paleopositon microblock, we focused on petrogenesis Eocene-Oligocene lamprophyres microblock. yield zircon UPb ages 34.7–33.3 Ma exhibit potassic-ultrapotassic features elevated K2O/Na2O (1.4–4.0) ratios. They characterized by high concentrations compatible (e.g., Cr = 187–692 ppm, Ni 31–218 ppm), large-ion-lithophile light rare-earth enrichment, high-field-strength depletion, radiogenic isotopic values, i.e. (87Sr/86Sr)i 0.7063–0.7078 ?Nd(t) ?3.9 ?2.4. Combined low Nb/U ratios, these suggest that lithospheric mantle source was metasomatized subduction-related fluids beneath relatively Rb/Sr ratios heavy element contents indicate were derived from partial melting a phlogopite-bearing lherzolite within spinel stability field. parental magmas have experienced fractional crystallization olivine clinopyroxene during emplacement. Comprehensive comparisons between mafic rocks western can be regarded as dismembered part due continental extrusion sinistral displacement. compositional trends palaeogeographic position near Dali area (west Binchuan) close Jinshajiang suture zone before Cenozoic.