Geochemistry characteristics and emplacement mechanism of the Cenozoic magma in Baoxingchang area, Yunnan Province, SW China

Abstract

Alkali-rich intrusions associated with Cu-Mo mineralization in Baoxingchang district, displaying both felsic and mafic rock series, can be: divided into four evolution stages. LA-ICP-MS zircon U-Pb ages of the four stages intrusions 36.5∼34.6Ma, 38.0∼33.5Ma, 36.0∼34.5Ma and 34.0Ma, respectively. All the studied rocks have similar magma sources and tectonic setting. The εHf(t) values indicate that they were reworked by ancient lithospheric mantle and crustal materials via subduction. Formation of the alkaline-rich intrusions in Baoxingchang area may be involved in the processes of partial melting of mantle rocks, crust-mantle materials and fractional crystallization. It appears an increasing tendency from felsic intrusions, to enclaves and then to early-stage lamprophyre to late-stage lamprophyre.