Three-stages magma mixing in the Weiya ore district, Xinjiang

Abstract：Three-stage magma mixing occurred in the Weiya vanadium-bearing titianomagnetite ore district, East Tianshan, Xinjiang. The first stage was mixing of gabbroic and granitic magmas, which formed dioritic rock; the second stage was mixing of dioritic and granitic magmas, which formed quartz monzonitic rock; the third stage was mixing of quartz monzonitic and dioritic magmas. The data points of the rocks produced during the third stage of magma mixing show a linear relation in the Hake diagrams of main oxides vs. SiO2. The rocks formed in three stages of magma mixing show similar geochemical characteristics in terms of REE and trace elements and their distribution patterns are also similar, and the transitional rocks-hybrid rocks formed during magma mixing have inheriting relations with their respective end-member rocks. The inheriting relations of the three stages of magma mixing are as follows: the first stage gave rise to hybrid rock with a composition equivalent to that of diorite, which belongs to the same type of rock as the basic end-member rock of the second stage and displays similar geochemical characteristics to those of various types of rock formed in the second stage; and the quartz monzodiorite formed in the second stage can be completely correlated with the end-member rock—quartz monzonite-porphyry—of the third stage. The three stages of magma mixing in the Weiya area might suggest that magma mixing can occur in multiple stages and that the primary parent magma of igneous rocks in the area was derived from continental crustal acid sialic magma and mantle-derived mafic magma, and magma mixing reflects the essence of crust-mantle interaction in this area.