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西准噶尔谢米斯台山发育的泥盆系呼吉尔斯特组主要为一套火山碎屑岩—中酸性火山熔岩组合。样品SiO_2含量为55.6%~67.78%,平均值为61.73%,K_2O含量为1.72%~6.6%,平均值为3.13%,Na_2O含量为2.44%~4.42%,平均值为3.48%,全碱含量高,K_2O+Na_2O大部分大于6%。岩石样品与典型的岛弧钙碱性安山岩相比,具有CaO、MgO含量较低,Al2O3、Fe_2O_3、P_2O_5含量较高的特征,稀土总量较低,含量为(85.92~139.63)×10~(-6),所有火山岩样品均表现出轻稀土相对富集重稀土相对亏损的特征;(La/Yb)N为2.94~7.14,所有火山岩样品具有不明显或微弱的Eu负异常,在原始地幔标准化微量元素蛛网图中均表现出富集Rb、Ba、Th、U、K等大离子亲石元素,亏损Nb、Ta等高场强元素。呈现出Nb、Ta、Ti负异常,具有岛弧火山岩地球化学特征。
The Devonian Hujilst Formation, developed in the Chemisi Taishan Mountain, west Junggar, is mainly composed of a volcaniclastic-intermediate-acid volcanic lava assemblage. The content of SiO_2 is 55.6% ~ 67.78%, the average is 61.73%, the K_2O content is 1.72% ~ 6.6%, the average is 3.13%, the content of Na_2O is 2.44% ~ 4.42%, the average is 3.48% , K2O + Na2O most of more than 6%. Compared with the typical island arc calc-alkaline andesite, the rock samples are characterized by lower contents of CaO and MgO and higher contents of Al2O3, Fe 2 O 3 and P 2 O 5, with a lower total content of rare earth (85.92 ~ 139.63) × 10 ~ -6). All of the volcanic samples showed the relative depletion characteristics of light rare earths relative to heavy rare earth elements. The (La / Yb) N ranged from 2.94 to 7.14. All volcanic samples had an insignificant or weak Eu anomaly. In the trace element cobweb images, large ion lithophile elements such as Rb, Ba, Th, U and K are enriched, and high field strength elements such as Nb and Ta are depleted. Showing negative Nb, Ta, Ti anomalies, with island arc volcanic geochemical characteristics.