论文部分内容阅读
在新疆库鲁克塔格地区的震旦纪和寒武纪沉积岩地层中 ,分布有四层火山岩。它们分别产出于早震旦世的贝义西组、晚震旦世的扎摩克提组和水泉组以及早寒武世的西山布拉克组。其中 ,西山布拉克组和水泉组火山岩均属碱性玄武岩系列 ;扎摩克提组火山岩分属碱性玄武岩系列和拉斑玄武岩系列 ;贝义西组火山岩具有明显的双峰式组合特征 ,大部分属碱性火山岩。它们的多元素配分曲线均呈现出板内玄武岩的大隆起特征。斜长石的分离结晶作用导致少部分火山岩具有负铕异常。西山布拉克组和水泉组火山岩的SiO2 饱和度低于扎摩克提组拉斑玄武岩。相应地 ,前者的不相容元素丰度普遍高于后者。两者之间的差异主要是部分熔融程度的差异所致。稀土元素的强烈分馏以及重稀土元素显著贫化 ,意味着这些火山岩源自于大陆岩石圈地幔的石榴石二辉橄榄岩。Ba/Nb、La/Nb、Ba/La、Ba/Th和Rb/Nb比值证明 ,这些火山岩全部源自于富集型地幔源区 ,而且主要是EMI型地幔。
There are four layers of volcanic rocks distributed in the Sinian and Cambrian sedimentary rocks in the Kuruktag area, Xinjiang. They were produced in the early Sinian Beiyixi Formation, Late Sinian Zamokake Formation and the Shuimu Formation and the Early Cambrian Xishan Braque Formation. Among them, the Xishan Brak Formation and the Shuquan Formation volcanic rocks belong to the alkaline basalt series; the Zamokake Formation volcanic rocks belong to the basic basalt series and the tholeiitic basalt series; the Beiyixi volcanic rocks have obvious bimodal assemblages with large Part of the alkaline volcanic rocks. Their multi-element distribution curves showed the large intraplate basaltic uplift characteristics. The separation and crystallization of plagioclase led to the negative Eu anomalies in a few of volcanic rocks. The SiO2 saturation of volcanic rocks in the Xishan Braque Formation and Shuicquan Formation is lower than that in Zamoclei Group. Correspondingly, the incompatible element abundances of the former are generally higher than the latter. The difference between the two is mainly due to the difference in the degree of partial melting. The intense fractionation of rare earth elements and the significant depletion of heavy rare earth elements mean that these volcanic rocks originated from garnet lherzolites of the continental lithosphere mantle. The ratios of Ba / Nb, La / Nb, Ba / La, Ba / Th and Rb / Nb prove that these volcanic rocks all originate from the enriched mantle source area and are mainly of the mantle type.