Geochemical characteristics and geological significance of the albitite in the Boka gold ore district, Yunnan Province

The Boka gold deposit is located in the Dongchuan ore concentration area, and belongs to Yunnan Proterozoic copper polymetallic mineralization belt. This paper reports the petrography, geochemistry and isotope features of albitite that is closely related to mineralization. Studies show that the mineral compositions of albitite are albite, pyroxene, biotite, and the major element characteris-tics indicate a high Na, alkali-enriched, metaluminous, alkaline-peralkaline rock. This albitite is characterized by low ΣREE, strong enrichment of LILE(K, Rb, Nd)and LREE(La, Ce, Sm), and depletion of HFSE elements(Nb, Ta, U, Th). Based on I_sr, ε_Nd(t)isoto-pic geochemistry, it is suggested that Boka albitite was produced by magmatism of Middle Proterzoic continent rift in Huili-Dongch-uan area, and it was derived from the deep mantle with the addition of some crustal materials in the magma source region.