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西天山二叠纪艾肯达坂组红色陆相火山岩建造不整合在下石炭统大哈拉军山组之上,未经变形和变质。主要岩石类型有粗面玄武岩、玄武粗安岩、粗安岩、粗面岩和粗面英安岩,w(SiO2)介于41.69%～65.99%,低于上陆壳平均成分(66%)。w(Na2O+K2O)随SiO2增加而增加;SI随SiO2增高而变小;w(TiO2)一般小于1.3%;w(Al2O3)较高(12.82%～18.37%),由此显示艾肯达坂组属于典型的橄榄安粗岩系。其中,玄武岩和玄武粗安岩的w(SiO2)低于54.4%(下陆壳平均值),表明它们应源于地幔,而非陆壳;相反,w(SiO2)>54.4%的粗安岩、粗面岩和粗面英安岩可能来自陆壳或经历了壳内分异作用。玄武岩类和玄武粗安岩类ΣREE,LREE,Zr,Hf,Nb,Ta,Ba,Sr,Pb,Y等的质量分数和LaN/YbN均高于世界同类岩石平均值,而Cr,Co,Ni等的质量分数低于同类岩石,指示源区地幔富集大离子亲石元素(LILE)和不相容元素;玄武岩类和玄武粗安岩类的Eu/Eu*<0.94,Sr由亏损变化到正异常,显示地幔源区成分不均一,此不均一性可能由上壳物质返回地幔所致。粗面岩和粗面英安岩Eu/Eu*平均0.59,低于上陆壳平均值0.65;Sr亏损显著;但ΣEEE,LREE,LREE/HREE,LaN/YbN,Ce/Ce*反而低于粗安岩;Sm/Nd平均值为0.25,与下陆壳(Sm/Nd=0.25)相一致;La,Ce,Nd,Sm等相对于Y和Yb富集;Ba正异常,Nb,Ta,Hf等?
The unconformity of the red continental volcanic rocks of the Aiken Daban Formation in the Permian of the Western Tianshan was not deformed and metamorphosed above the Dahalajun Mountain Formation of the Lower Carboniferous. The main types of rocks are coarse basalt, basalt, andesite, rough rock and rough dacite with w (SiO2) ranging from 41.69% to 65.99%, lower than the average composition of the upper continental crust (66%) . w (TiO2) is generally less than 1.3%; w (Al2O3) is higher (12.82% ~ 18.37%), which shows that the weight of w (Na2O + K2O) increases with the increase of SiO2 Group belongs to a typical olive Angu rock system. Among them, basalts and basaltic rocks have w (SiO2) less than 54.4% (average of continental crust), indicating that they originate from the mantle rather than the continental crust; on the contrary, w (SiO2)> 54.4% , That of the coarse and coarse dacite may come from the continental crust or have experienced intracavity divergence. The mass fractions of ΣREE, LREE, Zr, Hf, Nb, Ta, Ba, Sr, Pb and Y and LaN / YbN of basalt and basalt are higher than the average values of the same kind of rocks in the world, while the contents of Cr, Co and Ni And other mass fractions are lower than similar rocks, indicating that the source mantle enriches LILE and incompatible elements; basalts and basaltic rocks with Eu / Eu * <0.94 Sr changes from depletion to Positive anomaly, indicating that the composition of the mantle source is not uniform, this heterogeneity may be caused by the upper mantle material back to the mantle. The average Eu / Eu * of the rough and rough dacite is 0.59, which is lower than the average value of the upper crust of 0.65. The Sr loss is significant, but ΣEEE, LREE, LREE / HREE, LaN / YbN and Ce / Ce * Anan; the average value of Sm / Nd is 0.25, which is consistent with the lower crust (Sm / Nd = 0.25); La, Ce, Nd and Sm are enriched with respect to Y and Yb; Ba is anomalous; Nb, Ta and Hf Wait?