Liquid Immiscibility of Boninite in Xiangcheng, Southwestern China, and Its implication to Genetic Relationship between Boninite and Komatiitic Basalt  

作　　者：Tetusro Urabe Takagi Naito 

机构地区：[1]Geological Survey of Japan, Ibaraki 305, Japan,Geological Survey of Japan, Ibaraki 305, Japan,Geological Survey of Japan, Ibaraki 305, Japan

出　　处：《Acta Geologica Sinica(English Edition)》2001年第1期74-93,共20页地质学报（英文版）

摘　　要：Boninitic rocks and associated high-magnesian basalt and high-iron tholeiite in the Xiangcheng area constitute the basal horizon of the arc volcanic sequence in the Triassic Yidun Island-Arc, southwestern China. The boninite occurs as pillow, massive and ocellar lavas; the last one possesses well-developed globular structure and alternates with the former two. The boninite is characterized by the absence of phenocrysts of olivine and low-Ca pyroxenes and by low CaO/Al2O3 ratios (<0.67) and high Cr (>1000 ppm) and Ni (>250 ppm). The normalized abundance patterns (NAP) of trace elements to primitive mantle are similar to the NAP of low-Ca modern boninites and SHMB in the Archaean and Proterozoic.Boninitic rocks and associated high-magnesian basalt and high-iron tholeiite in the Xiangcheng area constitute the basal horizon of the arc volcanic sequence in the Triassic Yidun Island-Arc, southwestern China. The boninite occurs as pillow, massive and ocellar lavas; the last one possesses well-developed globular structure and alternates with the former two. The boninite is characterized by the absence of phenocrysts of olivine and low-Ca pyroxenes and by low CaO/Al2O3 ratios (<0.67) and high Cr (>1000 ppm) and Ni (>250 ppm). The normalized abundance patterns (NAP) of trace elements to primitive mantle are similar to the NAP of low-Ca modern boninites and SHMB in the Archaean and Proterozoic.

关 键 词：BONINITE komatiitic basalt liquid immiscibility Xiangcheng area of Sichuan 

分 类 号：P588.12[天文地球—岩石学]