Abstract:

Field geological, petrological and elementary geochemical studies reveal that the volcanic rocks, subvolcanic rocks and Muchen pluton of Xishantou Formation in the Wucun area in Zhejiang Province, which were formerly identified as calcicolous alkaline series rocks, should be typical shoshonitic rocks. These rocks are rich in alkali(Na₂O+K₂O=7.80％-11.48％) and kalium(K₂O/Na₂O=1.10-1.67), and poor in titanium(TiO₂=0.22％-0.88％) and ferrum(FeO+Fe₂O₃=2.91％-6.36％), also they have a relatively high content of aluminum (15.39％-18.24％), a moderate content of SiO₂ (56.96％-69.02％), and high ratios of Ce/Yb (27.29-38.19), Ta/Yb(0.32-0.74) and Th/Yb (4.76-7.72). Besides, they abound in macroion lithopile element and light rare earth element. All these are petrological geochemical features of shoshonitic rock series. The Wucun area is rich in mineral resources, its mineral deposit symbioses closely with shoshonitic magma rocks both in time and in space, and the shoshonitic magma rocks are its rock-forming matrix. These are important signs for ore-seeking petrology.

Key words: shoshonitic rock, elemental geochemistry, Xishantou Formation volcanic rock, subvolcanic rock, Muchen pluton, the Wucun area, Zhejiang