...
  • 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 >Inferring protoliths of high-grade metamorphic gneisses of the Erzgebirge using zirconology, geochemistry and comparison with lower-grade rocks from Lusatia (Saxothuringia, Germany)
【24h】

Inferring protoliths of high-grade metamorphic gneisses of the Erzgebirge using zirconology, geochemistry and comparison with lower-grade rocks from Lusatia (Saxothuringia, Germany)

机译：利用锆石学，地球化学方法以及与来自卢萨西亚的低品位岩石的比较，推断出厄尔士山脉的高级变质片麻岩的原石（德国萨克斯图林根）

获取原文
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Protoliths of highly metamorphosed gneisses from the Erzgebirge are deduced from the morphology, age and chemistry of zircons as well as from whole rock geochemistry and are compared with lower-grade rocks of Lusatia. Gneisses with similar structural appearance and/or geochemical pattern may have quite different protoliths. The oldest rocks in the Erzgebirge are paragneisses representing meta-greywackes and meta-conglomerates. The youngest group of zircon of meta-greywackes that did not undergo Pb loss represents the youngest igneous component for source rocks (about 575 Ma). Similar ages and zircon morphology reflect the subordinate formation of new zircon grains or only zircon rims in the augengneiss from Bärenstein and Wolkenstein, which probably represent metamorphic equivalents to Lower Cambrian two-mica granodiorites from Lusatia. Bulk rock chemistry, intense fracturing and high U and Th concentrations of zircons suggest deformation-induced and fluid-enhanced recrystallisation of zircon grains. Temperatures during tectonic overprinting—too low to reset zircon ages—indicate mid- or upper crustal levels for shearing recorded in these augengneisses. Lower Cambrian (~540 Ma) granodiorites are widespread in Lusatia but are exclusively represented by the Freiberg gneiss dome in the Eastern Erzgebirge. Ordovician protolith ages were recorded by zircons from the augengneisses of the Reitzenhain–Catherine dome and the Schwarzenberg dome (Western Erzgebirge) documenting significant regional differences between the eastern and the western Erzgebirge (~540 vs. ~490 Ma). In the Western Erzgebirge, most meta-volcanic rocks (muscovite gneisses) and meta-granites (mainly red augengneisses) yield Ordovician zircon ages, whereas in the Eastern part, similar rocks mainly recorded Lower Cambrian protolith ages. Zircon overprinting was highest within discrete tectonic zones where the combination of fluid infiltration and deformation induced variable degrees of recrystallisation and formation of a new augengneiss structure. Variable degrees of Pb loss caused age shifts that do not correspond to changes in zircon morphology but may be associated with U and Th enrichments. Major changes in bulk rock composition appear to be restricted to discrete zones and to (U)HP nappes, whereas gneisses with a MP–MT metamorphic overprint basically show no geochemical modifications.
机译：根据锆石的形态，年龄和化学以及整个岩石的地球化学推导了厄尔士山脉的高度变质片麻岩的原石，并与卢萨西亚的低品位岩石进行了比较。具有相似结构外观和/或地球化学特征的片麻岩可能具有完全不同的原岩。 Erzgebirge中最古老的岩石是代表超大型瓦砾和超大型砾岩的板岩。没有经历过Pb损失的最年轻的变质灰泥锆石代表了烃源岩中最年轻的火成岩成分（约575 Ma）。相似的年龄和锆石形态反映了来自Bärenstein和Wolkenstein的augengneiss中新的锆石晶粒的形成或仅锆石边缘的形成，这可能代表了Lusatia的下寒武统二云母花岗闪长岩的变质等价物。块状岩石化学性质，强烈的压裂以及锆石的U和Th含量高表明锆石晶粒发生了形变和流体增强的重结晶。构造叠印过程中的温度（太低而无法重置锆石年龄）指示这些奥古涅岩中记录的地壳中上水平。下寒武纪（约540 Ma）的花岗闪长岩广泛分布于卢萨西亚，但仅以东部的厄尔士山脉的弗莱堡片麻岩穹顶为代表。 Reitzenhain-Catherine穹顶和Schwarzenberg穹顶（Western Erzgebirge）的奥金涅山脉的锆石记录了奥陶纪的原石年龄，记录了东西方Erzgebirge之间的显着区域差异（〜540 vs.〜490 Ma）。在西部的厄尔士山脉（Erzgebirge），大多数超火山岩（白云母片麻岩）和超花岗岩（主要是红色奥古尼岩）产生奥陶纪的锆石年龄，而在东部，类似的岩石主要记录下寒武纪的原生岩时代。锆石叠印在离散的构造带中最高，在那里流体的渗透和变形的结合导致了不同程度的重结晶和新的奥格涅斯结构的形成。铅的不同程度的变化导致年龄的变化，这并不对应于锆石形态的变化，但可能与铀和Th的富集有关。块状岩石成分的主要变化似乎仅限于离散带和（U）HP尿布，而具有MP–MT变质叠印的片麻岩基本上没有任何地球化学修饰。

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