中国西南乡城地区玻镁安山岩和伴生的高镁玄武岩及高铁玄武岩构成了晚三叠世义敦岛弧的下部弧火山序列。玻镁安山岩主要呈互层的枕状、块状和球颗状熔岩产出,以缺乏橄榄石和低钙辉石斑晶以及低CaO/Al_1O_3比值(<0.67)、高Cr(>1000×10~(-6))和高Ni(>250×10~(-6))为特征。原生地幔标准化的微量元素配分型式类似于现代的低钙玻镁安山岩和太古代及显生宙SHMB。乡城玻镁安山岩发生岩浆不混溶并形成球状构造,得到下列证据佐证:①球颗状玻镁安山岩的球体与基体具有截然的接触关系;②球体与基体具有类似的 The volcanic andesite and associated high-magnesium basalt and high-speed basalt in the Xiangcheng area of ​​southwest China constitute the lower arc volcano sequence of the Late Triassic Rethymnon Island arc. The vitrinite andesite is mainly composed of lamellar, massive and spherical lava with interlayered lamellae. Due to the lack of olivine and calcite pyrophyllite and the low CaO / Al 1 O 3 ratio (<0.67) and the high Cr (> 1000 × 10 ~ (-6)) and high Ni (> 250 × 10 -6). The normalized trace elements in the primary mantle are similar to the modern low-calcium-magnesium-andesite and the Archean and Phanerozoic SHMB. Magma anagrams in the Xiangcheng area are immiscible and form a spherical structure. The following evidences are obtained: (1) the sphere of the globular magnesian andesite has a close contact relationship with the matrix; (2) the sphere has a similar