...
  • 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 >Petrogenesis of plagiogranites from the Troodos Ophiolite Complex, Cyprus
【24h】

Petrogenesis of plagiogranites from the Troodos Ophiolite Complex, Cyprus

机译：来自Troodos Ophiolite复合物，塞浦路斯的浮雕细胞

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

Small volumes of felsic melt, commonly known as oceanic plagiogranites, appear as melt pockets or dikes within the gabbroic section and the sheeted dikes root zone of the oceanic crust. Plagiogranites from the Troodos Ophiolite Complex on Cyprus are among the best exposures of felsic rocks that are embedded in a complete section of obducted oceanic lithosphere. Nevertheless, their exact petrogenesis is still a matter of debate, largely due to limited high-quality trace element and radiogenic isotope data. Previously proposed models for Troodos plagiogranites have included both low-pressure dehydration melting and fractional crystallisation at deeper levels of the oceanic crust. To evaluate both models, oceanic plagiogranites from the Troodos Ophiolite Complex were analysed in this study for their major and trace elements, and for the first time also for Hf-Nd-Sr isotope compositions. The trace element measurements also include for the first time high-precision measurements of high-field-strength element (HFSE) abundances that now permit to better unravel the petrogenesis of the Troodos plagiogranites and their possible mantle sources. In general, the Troodos plagiogranites exhibit a narrow range of Nb/Ta and Zr/Hf that overlap the compositions of mid-ocean ridge basalts (MORB). In line with earlier studies, three compositional groups can be identified: two groups formed by either fractional crystallisation or combined fractional crystallisation and wall rock assimilation, and one group derived from partial melting of slightly altered oceanic crust. The majority of the Troodos plagiogranites (Main Group) are the product of extensive fractional crystallisation of ambient arc-tholeiitic mafic melts. A second group of plagiogranites (Spilia Group) is generated by fractional crystallisation of boninitic precursor melts and the assimilation of arc-tholeiitic crustal material. Variable HFSE concentrations and diagnostic Hf-Nd isotope signatures that are unique to both suites allow discriminating between the two parental melts and fractionation processes. A small group of plagiogranites (Zoopigi Group) is interpreted to derive from partial melting in the conductive layer of active magma chamber lenses (AML). Elevated Nb/Ta, Zr/Hf, and light rare-earth element (LREE) enrichments in these rocks are in support of this model. Collectively, our data suggest that low-pressure fractional crystallisation (also in combination with assimilation of wall rocks) might be the predominant process controlling the formation of felsic rocks on Cyprus, whereas dehydration melting appears to be less important. If compared to Archean tonalitic-trondhjemitic-granodioritic suites (TTGs), compositions of plagiogranites from Cyprus mirror shallow-level processes in thin oceanic crust, which is illustrated by their narrow, MORB-like range of HFSE ratios and their distinct enrichment in heavy rare-earth elements (HREE) that distinguishes them from the Archean TTGs.
机译：众所周知的肠道熔体量，俗称海洋斑块，在GBBBOCE部分和海洋地壳的片状堤坝根部出现为熔体口袋或堤坝。来自Troodos Ophiolite Complex上的塞浦路斯的斑岩是肠道岩石的最佳曝光，嵌入在凸起的海洋岩石圈的完整部分中。然而，它们的确切化纤仍然是辩论的问题，主要是由于高质量的痕量元素和辐射同位素数据有限。以前提出的Troodos Plagiogranites的模型包括低压脱水熔化和在海洋外壳的更深层次的较深层次的脱水结晶。为了评估两种模型，在本研究中分析了来自Troodos Ophiolite络合物的海洋棱镜，对其主要和微量元素进行了分析，并且第一次也适用于HF-ND-SR同位素组合物。痕量元素测量还包括首次高精度测量的高型强度元件（HFSE）丰富，现在允许更好地解开Troodos PlagioGranites及其可能的地幔源的纤维化。通常，TROODOS甲岩具有窄范围的Nb / Ta和Zr / Hf，其与中海底沼泽（Morb）的组成重叠。根据早期的研究，可以鉴定三个组合物基团：通过分数结晶或组合的分数结晶和壁岩同化形成的两组，以及衍生自略微改变的海洋地壳的部分熔化。大多数Troodos Plagiogranites（主要组）是环境弧 - 烟型MAFIC MELTS广泛分数结晶的产物。通过Boninitic前体熔体的分数结晶和Arc-Tholeitait地壳材料的同化产生，产生第二组噬菌体（Spilia组）。两种套房具有独特的可变HFSE浓度和诊断HF-ND同位素签名允许判别两个父母熔体和分馏过程之间。一小组斑块（ZOOPIGI组）被解释为导出活动岩浆室镜片（AML）的导电层中的部分熔化。这些岩石中的升高的Nb / Ta，Zr / Hf和轻稀土元素（Lree）富含浓缩是支持该模型的。集体，我们的数据表明，低压分数结晶（也与墙岩同化相结合）可能是控制塞浦路斯上肠岩的形成的主要过程，而脱水熔化似乎不太重要。如果与Archean Tonalitic-trondhjemitic-granodioritic Suites（TTG）相比，来自塞浦路斯镜镜浅级过程中的斑块的组成，薄脑壳体中的浅层过程，其狭窄的Morb样的HFSE比率和它们在重稀有的不同浓缩 - 将它们与Archean TTGS区分开来的 - earth元素（hree）。

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