...
  • 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 >The role of amphibole in the evolution of arc magmas and crust: the case from the Jurassic Bonanza arc section, Vancouver Island, Canada
【24h】

The role of amphibole in the evolution of arc magmas and crust: the case from the Jurassic Bonanza arc section, Vancouver Island, Canada

机译：闪石在弧状岩浆和地壳演化中的作用：以加拿大温哥华岛的侏罗纪波南萨弧段为例

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

The Jurassic Bonanza arc, on Vancouver Island, British Columbia, represents an exhumed island arc crustal section of broadly diorite composition. We studied bodies of mafic and ultramafic cumulates within deeper levels of the arc to constrain the conditions and fractionation pathways leading from high-Mg basalt to andesite and dacite. Major element trends coupled with textural information show the intercumulus crystallization of amphibole, as large oikocrysts enclosing olivine in primitive cumulates controls the compositions of liquids until the onset of plagioclase crystallization. This process is cryptic, occurring only in the plutonic section, and explains the paucity of amphibole in mafic arc volcanics and the change in the Dy/Yb ratios in many arc suites with differentiation. The correlation of octahedral Al in hornblende with pressure in liquidus experiments on high-Mg basalts is applied as an empirical barometer to hornblendes from the Bonanza arc. It shows that crystallization took place at 470–880 MPa in H2O-saturated primitive basaltic magmas. There are no magmatic equivalents to bulk continental crust in the Bonanza arc; no amount of delamination of ultramafic cumulates will shift the bulk arc composition to the high-Mg# andesite composition of bulk continental crust. Garnet removal from wet magmas appears to be the key factor in producing continental crust, requiring high pressures and thick crust. Because oceanic island arcs are built on thinner crust, the long-term process generating the bulk continental crust is the accretion of island arcs to continental margins with attendant tectonic thickening.
机译：位于不列颠哥伦比亚省温哥华岛的侏罗纪Bonanza弧代表着一个闪闪发光的岛弧地壳部分，其大部分为闪长岩。我们研究了弧深层中镁铁矿和超镁铁矿的堆积体，以约束从高镁玄武岩到安山岩和榴辉岩的条件和分馏途径。主要元素趋势与结构信息一起显示了角闪石的丘间结晶，因为在原始堆积物中包围橄榄石的大卵形晶控制了液体的组成，直到斜长石结晶开始。这个过程是隐秘的，仅发生在深部断层，解释了镁铁质弧形火山岩中角闪石的稀缺性以及许多具有差异性的弧形套件中Dy / Yb比的变化。在高镁玄武岩上液相线实验中，角闪石中八面体Al与压力的相关性被用作经验丰富的气压表，用于分析来自Bonanza弧的角闪石。结果表明，在H 2 O饱和的原始玄武岩浆中结晶发生在470-880 MPa。在Bonanza弧中，没有岩浆等效于大块大陆壳。超镁铁质堆积物的分层不会将大弧成分转移到大陆壳的高Mg＃安山岩成分。从湿的岩浆中除去石榴石似乎是产生大陆壳的关键因素，需要高压和厚壳。由于海洋岛弧是建立在较薄的地壳上，因此，产生大量大陆壳的长期过程是岛弧在大陆边缘增加，伴随着构造增厚。

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