...
  • 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 >TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust
【24h】

TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

机译：下弧地壳含水分馏在现代弧基岩中形成的TTG型深成岩

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

We present the geochemistry and intrusion pressures of granitoids from the Kohistan batholith, which represents, together with the intruded volcanic and sedimentary units, the middle and upper arc crust of the Kohistan paleo-island arc. Based on Al-in-hornblende barometry, the batholith records intrusion pressures from ~0.2 GPa in the north (where the volcano-sedimentary cover is intruded) to max. ~0.9 GPa in the southeast. The Al-in-hornblende barometry demonstrates that the Kohistan batholith represents a complete cross section across an arc batholith, reaching from the top at ~8–9 km depth (north) to its bottom at 25–35 km (south-central to southeast). Despite the complete outcropping and accessibility of the entire batholith, there is no observable compositional stratification across the batholith. The geochemical characteristics of the granitoids define three groups. Group 1 is characterized by strongly enriched incompatible elements and unfractionated middle rare earth elements (MREE)/heavy rare earth element patterns (HREE); Group 2 has enriched incompatible element concentrations similar to Group 1 but strongly fractionated MREE/HREE. Group 3 is characterized by only a limited incompatible element enrichment and unfractionated MREE/HREE. The origin of the different groups can be modeled through a relatively hydrous (Group 1 and 2) and of a less hydrous (Group 3) fractional crystallization line from a primitive basaltic parent at different pressures. Appropriate mafic/ultramafic cumulates that explain the chemical characteristics of each group are preserved at the base of the arc. The Kohistan batholith strengthens the conclusion that hydrous fractionation is the most important mechanism to form volumetrically significant amounts of granitoids in arcs. The Kohistan Group 2 granitoids have essentially identical trace element characteristics as Archean tonalite–trondhjemite–granodiorite (TTG) suites. Based on these observations, it is most likely that similar to the Group 2 rocks in the Kohistan arc, TTG gneisses were to a large part formed by hydrous high-pressure differentiation of primitive arc magmas in subduction zones.
机译：我们介绍了科希斯坦岩基的花岗岩类的地球化学特征和侵入压力，连同侵入的火山和沉积单元，代表了科希斯坦古岛弧的中上地壳。根据Al-in-hornblende气压计，该岩床记录了北部（〜火山沉积盖被侵入的地方）〜0.2 GPa到最大的侵入压力。东南约0.9 GPa。 Al-in-hornblende气压测量表明，Kohistan岩基代表了弧形岩基的完整横截面，从顶部在约8-9 km深度（北）到底部在25-35 km（从中南到东南） ）。尽管整个岩基岩层完全露头且易于接近，但整个岩基岩层均未观察到组成分层。花岗岩的地球化学特征分为三类。第一组的特征是高度富集的不相容元素和未分级的中等稀土元素（MREE）/重稀土元素图案（HREE）；第2组富集了与第1组相似的不相容元素浓度，但MREE / HREE的含量极高。第3组的特征是仅具有有限的不相容元素富集和未分级的MREE / HREE。不同组的起源可以通过相对含水的（第1组和第2组）和较低含水量的（第3组）分馏结晶线从原始玄武岩母体在不同压力下模拟得到。适当的铁镁/超音波累积说明了每组的化学特征，这些累积在弧的底部。 Kohistan岩基证实了以下结论：含水分馏是在弧中形成体积显着数量的类固醇的最重要机制。 Kohistan Group 2花岗岩类的示踪元素特征与太古方石，长白云母-辉闪闪石（TTG）套件基本相同。基于这些观察，TTG片麻岩很可能类似于Kohistan弧中的第2组岩石，很大一部分是由俯冲带中原始弧岩浆的含水高压分异形成的。

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