Geochemical characteristics of the pegmatite veins in Shaotangou area, Jiajika of Western Sichuan Province

Based on petrological and geochemical investigations of the pegmatite veins in Shaotangou area, this paper discusses their origin and tectonic setting. The results show that SiO₂ content of the pegmatite veins in Shaotangou ranges from 73.46% to 75.96%, and the total alkaline content ranges from 4.71% to 7.36%, with Rittman index of 0.7 to 1.84, which indicates that the rocks have calc-alkaline characteristics. The aluminum saturation index (A/CNK) of the pegmatite veins is over 1.1 (1.54 to 2.49), indicating that these rocks belong to peraluminous S-type granite. The major, trace and rare earth elements data of the pegmatite veins indicate that they are mainly sourced from clay sediments. They have similar trace and rare earth elements distribution and Nb/Ta ratio, compared with Jiajika two-mica granite. And these two pegmatite veins are cogenetic and belong to highly differentiated granite. The tectonic setting analysis shows that the pegmatite veins are classified as syn-collision granite, and that the dome structure in Jiajika area provides a favorable structural environment for the formation of the rare metal pegmatite veins during the relative stable late stage of Indo-China movement.