论文部分内容阅读
萨尔托海蛇绿混杂岩是西准噶尔地区达拉布特蛇绿混杂岩带的重要组成部分,其形成时代和构造环境颇具争议。通过LA-ICP-MS锆石微区原位U-Pb同位素测年,获得其中辉长辉绿岩的~(206)Pb/~(238)U加权平均年龄为388.8±1.1 Ma,确定该蛇绿混杂岩形成于中泥盆世。岩石地球化学分析表明,纯橄岩(蛇纹岩)属于低Si、低碱、高Mg的变质橄榄岩,REE呈∑REE偏低的平坦型分布模式,Cr、Ni和Co含量较高;变玄武岩属于高Ti、富Mg、富Fe、偏碱的拉斑系列,REE分布模式呈现ΣREE偏低、Eu异常不明显的平坦型曲线,微量元素分布模式为K、Cs、Th、Nb和P相对亏损的平坦型曲线,Zr/Nb比值低,总体表现出与E-MORB相似的特征。综合判断认为,萨尔托海蛇绿混杂岩形成于大陆裂谷向洋盆转化的构造环境,类似于“红海式”洋盆,为进一步深入认识新疆地区众多蛇绿混杂岩的形成构造环境提供了新思路。
The Salto Sea ophiolitic melange is an important part of the ophiolite mound in the Dalbot, western Junggar. The formation age and tectonic setting are quite controversial. The ~ (206) Pb / ~ (238) U weighted average age of the gabbro diabase was 388.8 ± 1.1 Ma, which was determined by in-situ U-Pb isotope dating of LA-ICP- Green melange formed in the Middle Devonian. Petrochemical analysis shows that dunite (serpentinite) is a low-Si, low-alkali and high-Mg metamorphic peridotite. REE shows a flat ΣΣREE distribution with high Cr, Ni and Co contents. Basalt belongs to the series of high Ti, Mg-rich, Fe-rich and Alkaline pullulan series. The REE distribution pattern shows a flat curve with low ΣREE and no obvious Eu anomaly. The distribution patterns of trace elements are K, Cs, Th, Nb and P A flat curve of loss, with a low Zr / Nb ratio, generally exhibits similar characteristics as E-MORB. The comprehensive judgment shows that the Salto Sea ophiolitic melange formed in the tectonic environment transformed from the continental rift to the oceanic basin, similar to the “Red Sea” ocean basin, providing a further insight into the formation tectonic environment of many ophiolitic melanges in Xinjiang A new idea.