Abstract:

 The Yingmailai granitic intrusion is located in the middle part of the southern Tianshan. It consists predominantly of biotite K-feldspar granite with minor two-mica K-feldspar granite. They have similar whole-rock geochemical characteristics, but distinct mineralogy. Opaque minerals in biotite K-feldspar granite are ilmenite, whereas they are magnetite in two-mica K-feldspar granite. According to Ishihara's classification(1977), biotite K-feldspar granite can undoubtedly be classified to ilmenite-series. Although some characteristics, e.g, presence of magnetite and Mg-rich biotite, suggest magnetiteseries, it should be noted that the magnetite in two-mica-K-feldspar granite is formed by post magmatism. In combination with low Fe³⁺ /(Fe³⁺+Fe²⁺)ratio and presence of indicating mineral—muscovite, it can be inferred that it also belongs to ilmeniteseries. In addition,the mineralogical and geochemical characteristics of the Yingmailai granitic intrusion indicate Stype granitoids,which suggests that ilmeniteseries correspond to Stype granite in the southern Tianshan. This research also suggests that the southern Tianshan had not experienced within plate during Early Permian.

Key words: southern Tianshan, Yingmailai granitic intrusion, biotite K-feldspar granite, two-mica K-feldspar granite, fo₂, ilmenite-series