...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Contributions to Mineralogy and Petrology >Zircon trace element chemistry at sub-micrometer resolution for Tarawera volcano, New Zealand, and implications for rhyolite magma evolution
【24h】

Zircon trace element chemistry at sub-micrometer resolution for Tarawera volcano, New Zealand, and implications for rhyolite magma evolution

机译：新西兰塔拉威拉火山亚微米分辨率的锆石微量元素化学性质及其对流纹岩浆演化的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Zoned crystals can be important recorders of magmatic processes in space and time. However, in most situations, the temporal dimension is difficult to quantify. Here, we have employed secondary ion mass spectrometry depth profiling to excavate parallel pits into non-polished crystal faces of zircon to obtain ~5 μm resolution U-Th disequilibrium ages (one pit) that can be correlated with trace element zoning at sub-μm resolution derived from a second pit. Data from 17 crystals representing each of the four rhyolite eruptions of Tarawera volcano, an intra-cal-dera edifice within the Okataina Volcanic Centre, reveal diverse zircon growth conditions over time. Most crystals display rimward depletions in Zr/Hf and Ti, broadly consistent with cooling and crystallization. However, a significant fraction of crystals lacks these patterns and displays rimward trace element variations consistent with isothermal or prograde crystallization. Oscillatory zonation patterns in Y, Th, and U arc superimposed on the Zr/Hf and Ti trends. Despite the limited number of crystals analyzed in this way, the striking lack of ubiquitous trace element zoning patterns in crystals from the same hand sample implies that fractional crystallization upon cooling was punctuated by magma recharge and crystal mixing affecting different parts of the magma reservoir. By combining data from all crystals, a systematic change to more heterogeneous trace element abundances is revealed by zircon crystal domains <45 ka following the Rotoiti caldera-forming eruption. This contrasts with the more uniform conditions of zircon crystallization lasting >100 ka prior to caldera formation and is best explained by the post-caldera system consisting of small, isolated melt pockets that evolved independently. An important conclusion is that the zircon 'cargo' in volcanic rocks reflects thermally and compositionally divergent processes that act near simultaneously in a magma storage region and not exclusively the conditions in the eruptible magma.
机译：分区晶体可以成为时空岩浆过程的重要记录者。但是，在大多数情况下，时间维度很难量化。在这里，我们采用了二次离子质谱深度剖析法，将平行坑开挖到未抛光的锆石晶体表面中，从而获得了约5μm的U-Th不平衡年龄（一个坑），这可与亚μm的微量元素分区相关分辨率源自第二个坑。来自代表Okataina火山中心内火山口内塔拉威拉火山（Tarawera volcano）的四个流纹岩喷发的17个晶体的数据揭示了随着时间的推移锆石的生长条件各不相同。大多数晶体在Zr / Hf和Ti中显示出向边缘耗尽，这与冷却和结晶大致一致。然而，很大一部分晶体缺乏这些图案，并且显示出与等温或渐进结晶一致的微量元素变化。 Y，Th和U的振荡分区模式叠加在Zr / Hf和Ti趋势上。尽管以这种方式分析的晶体数量有限，但同一手样品中晶体中普遍缺乏痕量元素分区模式，这意味着岩浆充注和影响岩浆储层不同部位的晶体混合会破坏冷却后的部分结晶。通过组合来自所有晶体的数据，在Rotoiti破火山口形成喷发之后，<45 ka的锆石晶体域揭示了向更不均匀的痕量元素丰度的系统变化。这与在破火山口形成之前持续> 100 ka的锆石结晶条件更为一致，并且最好由破火山口后系统组成，该系统由小而独立的熔体囊组成，并独立演化。一个重要的结论是，火山岩中的锆石“货物”反映了热和成分发散过程，这些过程在岩浆储藏区中几乎同时起作用，而不仅限于喷发岩浆中的情况。

著录项

相似文献

  • 外文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号