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对内蒙古林西地区火山岩样品的地球化学研究表明,其具有大洋型(O型)高镁埃达克质安山岩的地球化学特征[w(SiO2)=57.89%～63.97%、w(Al2O3)=15.39%～16.17%、w(Na2O)/w(K2O)=1.5～2.2(除一个为0.9)、A/CNK=0.83～0.97、Mg#=49～64、w(Cr)=91～209μg/g、w(Ni)=52.2～111.4μg/g、w(Sr)=551～1018μg/g、w(Yb)=1.18～1.71μg/g、w(Y)=12.6～17.7μg/g、δ(Eu)=0.86～0.94]。利用LA-ICP-MS对其锆石进行了U-Pb定年,得到206Pb/238U加权平均年龄为(244±2)Ma(MSWD=0.36)。此时,区域内古亚洲洋已闭合,综合地球化学特征和区域地质环境说明,林西高镁埃达克质安山岩是由残余洋壳部分熔融并随后与地幔橄榄岩相互作用形成的。内蒙古林西早中生代高镁埃达克质安山岩的产出表明,洋壳来源的埃达克岩(O型埃达克岩)不仅可以随俯冲同时产生,而且也可以在非俯冲环境下由保存在古俯冲带地幔中的残余洋壳部分熔融产生。
The geochemical characteristics of the volcanic rocks in the western Linxi area of Inner Mongolia show that the geochemical characteristics of the volcanic rocks in the western part of western Inner Mongolia are as follows: w (SiO2) = 57.89% ~ 63.97%, w (Al2O3) = 15.39 % To 16.17%, w (Na2O) / w (K2O) = 1.5 to 2.2 (except 0.9), A / CNK = 0.83 to 0.97, Mg # = 49 to 64 and Cr = 91 to 209 μg / g , W (Ni) = 52.2-111.4 μg / g, w (Sr) = 551-1018 μg / g, w (Yb) = 1.18-1.71 μg / g, w (Y) = 12.6-17.7 μg / g, Eu) = 0.86 ~ 0.94]. U-Pb zircon dating was performed using LA-ICP-MS. The 206Pb / 238U weighted average age was (244 ± 2) Ma (MSWD = 0.36). At this time, the paleo-Asian ocean in the area has been closed. The comprehensive geochemical characteristics and regional geological conditions show that the Linxi high-magnesium adakitic andesite was formed by the partial melting of the residual oceanic crust and subsequent interaction with the mantle peridotite. The production of the high-magnesium adakitic andesite in the Early Mesozoic in western Linxi of Inner Mongolia shows that adakite (O-type adakite) derived from the oceanic crust can be produced not only simultaneously with subduction but also in the non-subducted environment The remnants of the oceanic crust in the ancient subduction zone are partially melted.