...
  • 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 >Rare-earth element systematics of carbonatitic fluorapatites, and their significance for carbonatite magma evolution
【24h】

Rare-earth element systematics of carbonatitic fluorapatites, and their significance for carbonatite magma evolution

机译：碳酸盐氟磷灰石的稀土元素体系及其对岩浆岩浆演化的意义

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

Magmatic fluorapatites of five African carbonatite complexes were analyzed for rare-earth (REE) and trace elements by electron microprobe and high-resolution synchrotron micro-XRF to explore the fluorapatite composition during different stages of carbonatite magma evolution. Early crystallized fluorapatites have La concentrations mostly below 1,500 ppm and low #SIGMA#REE. They display convex-upward shaped REE patterns with (La/Nd)_(cn) <= 1 and low (La/Yb)_(cn) ratios < 100. In contrast, fluorapatites from fractionated carbonatites have straight REE patterns with (La/Nd)_(cn)>1 and (La/Yb)_(cn) generally above 100, and have La up to 1 wt percent at a high #SIGMA#REE. Model calculations with the fractionating mineral assemblage fluorapatite + calcite +- clinopyroxene suggest REE distribution coefficients for fluorapatite/carbonatite melt with a positive slope throughout from La to Lu, in order to meet the relationships observed in the natural fluorapatites. The calculations oppose closed system conditions of magma fractionation along the liquid lines of descent, but suggest periods of instantaneous fluorapatite crystallization. Fluorapatite trace element characteristics are therefore thought to be indicative for carbonatite evolution, and can reflect the relative degree of magma fractionation. We suggest that the (Eu/Eu*)_(cn) and Y evolution in the fluorapatites is a manifestation of an aqueous fluid immiscibly coexisting with the carbonatite magma from early evolution on, which is able to continuously extract divalent Eu and Y from the carbonatite magma.
机译：通过电子探针和高分辨率同步加速器X射线荧光光谱仪分析了五个非洲碳酸盐岩配合物的岩浆氟磷灰石的稀土元素和微量元素，探讨了碳酸盐岩浆演化不同阶段的氟磷灰石组成。早期结晶的氟磷灰石的La浓度大多低于1,500 ppm，并且＃SIGMA＃REE低。它们显示（La / Nd）_（cn）<= 1且低（La / Yb）_（cn）比<100的凸向上形状的REE模式。相反，分馏碳酸盐岩中的氟磷灰石具有（La / Nd）_（cn）> 1和（La / Yb）_（cn）通常大于100，并且在＃SIGMA＃REE高的情况下，La含量高达1 wt％。用分馏矿物组合氟磷灰石+方解石+-斜向辉石进行的模型计算表明，从La到Lu贯穿整个正斜率的氟磷灰石/碳酸盐熔体的REE分布系数，以满足在天然氟磷灰石中观察到的关系。该计算与沿下降液体线的岩浆分离的封闭系统条件相反，但建议瞬时氟磷灰石结晶期。因此，氟磷灰石微量元素的特征被认为是碳酸盐岩演化的指示，并且可以反映岩浆分离的相对程度。我们认为氟磷灰石中的（Eu / Eu *）_（cn）和Y演化是从早期演化开始就与碳酸岩岩浆不混溶的水性流体的一种表现形式，它能够连续地从岩浆中提取二价Eu和Y.碳酸盐岩浆。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 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