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准噶尔盆地东部巴里坤地区怪石山二长花岗岩体和县煤矿北花岗闪长岩体分别获得440.6±3.7 Ma和412.8±3.3 Ma的LA-ICP-MS锆石U-Pb形成年龄,指示该区早志留世-早泥盆世一期重要的花岗岩浆活动。两岩体为准铝-弱过铝钙碱性及高钾钙碱性岩系,微量元素具有富集LILE、贫HFSE,亏损Nb、Ta、Ti、P以及Pb正异常的岛弧岩浆成因特征。其中,怪石山岩体高Si、富K,高Rb/Sr和Ga/A1比值、低K/Rb比值,强Eu负异常,代表其为岛弧演化较为成熟阶段岩浆演化的产物;县煤矿北二长花岗岩富Na、高Sr和Sr/Y比值,低Y和Yb,则指示其为岛弧演化晚期,洋盆俯冲消减闭合过程、岛弧区地壳增厚环境下部陆壳物质熔融的结果。此外,两个岩体正的锆石ε_(Hf)(t)(+7.64~+13.86)和老于其形成年龄的Hf二阶段模式年龄(T_(DM2)=1123~561 Ma)证明,它们主要源自新元古代晚期到早古生代早期的新生岛弧陆壳物质。
The age of LA-ICP-MS zircon U-Pb of 440.6 ± 3.7 Ma and 412.8 ± 3.3 Ma, respectively, were obtained from the Wushishan granite body and the northern granodiorite body in Bailikun area, eastern Junggar Basin, Early Silurian - an important granite magmatism in the Early Devonian. The two intrusions are quasi-Al-weakly Al-Ca-Alkaline and high-K calc-alkaline rock series. Trace elements have the characteristics of island arc magmatism with enrichment of LILE, depletion of HFSE, loss of Nb, Ta, Ti, P and Pb positive anomalies . Among them, the rock masses of the rock are high Si, K rich, high Rb / Sr and Ga / Al ratio, low K / Rb ratio and strong Eu negative anomaly, which represent the product of magmatic evolution of the more mature stage of island arc evolution. The richness of Na, Sr and Sr / Y, low Y and Yb in the monzonitic granites indicate that they are the result of the melting of the continental crust beneath the crust thickening environment in the island arc zone due to the late evolution of the island arc and ocean basin subduction. In addition, the positive zircon ε_ (Hf) (t) (+ 7.64 ~ + 13.86) and Hf two-stage age (T_ (DM2) = 1123 ~ 561 Ma) Mainly from the late Neolithic to early Early Paleozoic archeological arc continental crust material.