...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Volcanology and Geothermal Research >Compositional diversity among primitive lavas of Mauritius, Indian Ocean: Implications for mantle sources
【24h】

Compositional diversity among primitive lavas of Mauritius, Indian Ocean: Implications for mantle sources

机译：印度洋毛里求斯原始熔岩之间的成分多样性：对地幔来源的影响

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

Three distinct phases of basaltic volcanism (Older Series, 7.8-5.4 Ma; Intermediate Series, 3.5-1.9 Ma; Younger Series, 0.7-0.03 Ma), related to the Deccan-Reunion mantle-plume, occurred over a time span of nearly 8 million years on the island of Mauritius, Indian Ocean. Bulk rock compositions of 52 analyzed samples (including samples from 32 recent borehole sections), as well as the compositions of olivine and spinel phenocrysts, reveal significant temporal variations in the composition of the Mauritius magmas. Two distinct compositional groups are identified based on their major and trace element compositions. The Group 1 basalts comprise the Younger Series, Intermediate Series and the earlier products of the Older Series rocks, and have higher MgO (7.6-13.6 wt.%) and lower K_2O (0.2-0.5 wt.%) and La/Sm (2.1-3.5) compared to Group 2 basalts (MgO 6.2-9.2 wt.%; K_2O 1.0-1.5 wt.%; La/Sm 3.6-4.1), which exclusively encompass the later differentiation products erupted during the end of the Older Series volcanism, denoted as Older Differentiated (OD) Series. Petrographic and mineralogic studies further confirm the presence of two distinct groups. Relatively primitive olivine compositions (Fo: 87-80) in Group 1 rocks are characterized by increasing CaO (0.2 to 0.3 wt.%) with decreasing Fo content, whereas in Group 2 rocks olivine (Fo: 86-80) show decreasing CaO (0.4 to 0.3 wt.%) with decreasing Fo content. Olivine-hosted spinel inclusions also show strong compositional differences between groups 1 and 2. Unusually Al-rich spinels (compared to that usually found in plume derived magma) and the positive Sr anomalies in Group 1 rocks suggest assimilation of crustal gabbros by the plume magmas. We propose a laterally heterogeneous plume and the contributions from variable plume components to account for the compositional differences observed in the two Mauritian lava groups. The early-Shield building Older Series lavas (oldest Group 1 lavas), characterized with a relatively less enriched trace element abundances, most likely derive from extensive melting of a depleted peridotite matrix in the core of the plume. Melting of this already depleted source produced the later Intermediate and Younger Series eruptions. Towards the late-shield stage, melts presumably derive from the enriched pyroxenite/eclogite components in the outer part of the plume.
机译：与Deccan-Reunion幔幔有关的玄武质火山活动分为三个不同的阶段（较老的系列，7.8-5.4 Ma;中级系列，3.5-1.9 Ma;年轻的系列，0.7-0.03 Ma），发生了近8个时间段在印度洋毛里求斯岛上有一百万年的历史。 52个分析样品（包括最近32个井眼部分的样品）的块状岩石成分以及橄榄石和尖晶石型隐晶石的成分表明，毛里求斯岩浆的成分存在明显的时间变化。根据其主要和痕量元素组成确定两个不同的组成组。第1组玄武岩由年轻系列，中级系列和较老系列岩石的早期产品组成，并具有较高的MgO（7.6-13.6 wt。％）和较低的K_2O（0.2-0.5 wt。％）和La / Sm（2.1 -3.5）与第2组玄武岩（MgO 6.2-9.2 wt。％； K_2O 1.0-1.5 wt。％； La / Sm 3.6-4.1）相比，后者专门涵盖了在旧系列火山活动结束后爆发的后期分化产物，表示为旧的差异化（OD）系列。岩石学和矿物学研究进一步证实了两个不同群体的存在。第1组岩石中相对原始的橄榄石成分（Fo：87-80）的特征是CaO（0.2至0.3 wt。％）随着Fo含量的降低而增加，而第2组岩石中的橄榄石（Fo：86-80）则CaO减少（降低了Fo含量为0.4至0.3 wt。％）。橄榄石包裹的尖晶石夹杂物在第1组和第2组之间也显示出强烈的成分差异。通常富含Al的尖晶石（与通常在羽状岩浆中发现的相比）和第1组岩石中的Sr正异常表明，羽状岩浆对地壳辉长岩的同化作用。我们提出了一个横向异质羽状流和可变羽状流成分的贡献，以解释在两个毛里求斯熔岩群中观察到的成分差异。早期盾构建筑的较旧系列熔岩（最古老的1组熔岩），其痕量元素丰度相对较低，其特征很可能来自羽状岩心中贫化的橄榄岩基质的广泛熔化。融化了这个已经枯竭的水源，产生了后来的中级和年轻系列喷发。进入后期防护阶段，熔体可能来自羽状流外部富集的辉石岩/榴辉岩成分。

著录项

相似文献

  • 外文文献
  • 中文文献
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