张宏法, 陈刚, 包洪平, 王润三, 彭天朗. 火山岩锆石产状及痕量元素对成因的约束[J]. 地质与资源, 2013, 22(1): 67-75. DOI: 10.13686/j.cnki.dzyzy.2013.01.013
    引用本文: 张宏法, 陈刚, 包洪平, 王润三, 彭天朗. 火山岩锆石产状及痕量元素对成因的约束[J]. 地质与资源, 2013, 22(1): 67-75. DOI: 10.13686/j.cnki.dzyzy.2013.01.013
    ZHANG Hong-fa, CHEN Gang, BAO Hong-ping, WANG Run-san, PENG Tian-lang. ORIGIN OF THE IGNEOUS ZIRCONS: Constraints from Morphology and Trace Element Chemistry[J]. Geology and Resources, 2013, 22(1): 67-75. DOI: 10.13686/j.cnki.dzyzy.2013.01.013
    Citation: ZHANG Hong-fa, CHEN Gang, BAO Hong-ping, WANG Run-san, PENG Tian-lang. ORIGIN OF THE IGNEOUS ZIRCONS: Constraints from Morphology and Trace Element Chemistry[J]. Geology and Resources, 2013, 22(1): 67-75. DOI: 10.13686/j.cnki.dzyzy.2013.01.013

    火山岩锆石产状及痕量元素对成因的约束

    ORIGIN OF THE IGNEOUS ZIRCONS: Constraints from Morphology and Trace Element Chemistry

    • 摘要: 为了探索火山岩产出锆石的成因属性,用CL图像及LA-ICP-MS原位分析痕量元素数据对山西临县紫金山碱性杂岩体内火山喷出相岩石是否产出锆石进行了研究.结果显示:响岩质、粗面质火山角砾岩(爆发相)均没有结晶出锆石,紫红色与灰白色响岩(溢流相)、粗面斑岩(火山颈侵出相)产出少量结构复杂的捕获锆石.对这些锆石进行LA-ICP-MS原位分析,表面年龄呈5段分布,分别为太古宙、古元古代、晚古生代、印支期与燕山期.年龄数据大多数与燕山期岩浆活动年代不符,呈现出大多数为捕获锆石的数据结构特征.CL图像显示大多数具有捕获锆石的岩浆熔蚀及后期改造迹象.痕量元素显示非碱性岩浆结晶的复杂成因特征,稀土元素显示多期次岩浆结晶、改造特征.结果表明:山西临县紫金山杂岩体内爆发相岩浆温度高,Zr元素含量不饱和,不结晶锆石同时将捕获锆石熔化;溢流相与火山颈相岩浆温度稍低,Zr元素含量仅达到饱和临界点,捕获锆石仅发生轻度熔蚀,而没有结晶自生锆石.

       

      Abstract: Detailed study on the morphology and trace element chemistry of the Zijinshan alkaline complex reveals that there is no igneous zircon in the phonolitic, trachytic and volcanic breccia, with minor xenocryst zircons in the purple and white phonolite and trachyte porphyry. LA-ICP MS analysis results indicate that there are five stages for the formation of these zircons, i.e. Archean, Paleoproterozoic, Late Paleozoic, Early Mesozoic and Late Mesozoic. Most of the zircons present as xenocrysts, which show erosion textures in the CL images. Trace element chemistry suggests a complex crystallization process for the zircons in sub-alkaline rocks, with REE patterns characterized by multi-stage crystallization and alteration. It is concluded that the zirconium is unsaturation in the alkaline magma, with all the xenocrysts corroded. The zircon in the overflow facies magma just reaches the critical point of saturation, so there is no igneous zircon in these melts.

       

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