• 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 >A P-T pseudosection modelling approach to understand metamorphic evolution of the Main Central Thrust Zone in the Alaknanda valley, NW Himalaya
【24h】

A P-T pseudosection modelling approach to understand metamorphic evolution of the Main Central Thrust Zone in the Alaknanda valley, NW Himalaya

机译：利用P-T伪剖面建模方法了解喜马拉雅西北阿拉克南达河谷主要中央冲断带的变质演化

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 Main Central Thrust Zone (MCTZ) in the Alaknanda valley, NW Himalaya, affected the Lesser Himalayan Crystalline Sequence and has a gradual transition to the structurally overlying Higher Himalayan Crystalline Sequence (HHCS). This boundary is defined on the basis of the following petrographic features in pelitic rocks at the base of the HHCS: (i) first appearance of microscopic needles of kyanite upon moving up-section along the transect; (ii) garnet porphyroblasts with random inclusion pattern and non-rotational growth history, which contrast with the garnet porphyroblasts in MCTZ rocks with spiral inclusion trails; and (iii) chemically homogeneous garnet porphyroblasts as opposed to the growth-zoned garnets in MCTZ rocks. Pseudosection modelling and garnet isopleth thermobarometry of pelitic rocks yield peak metamorphic conditions of 6.3-7.5 kbar and 550-582 degrees C in the MCTZ, and 8.0-10.0 kbar and 610-650 degrees C in the basal part of the HHCS. The results indicate continuity in the P-T field gradient across the contact between the MCTZ and HHCS. The MCTZ shows an inverted metamorphic sequence from biotite to garnet zones. Metamorphism in the basal part of the HHCS is in the kyanite zone, which is continuous with the inverted metamorphic sequence. Both P and T increase up-section, peak in the lower HHCS and then decrease higher up in the HHCS unit. The observations are consistent with predictions of a recently proposed thermomechanical model in which temperature in the shear zone rises due to viscous heating and pressure rises as a result of weakening of the rocks.
机译：喜马拉雅西北部阿拉克南达河谷的主要中央逆冲带（MCTZ）影响了小喜马拉雅结晶序列，并逐渐过渡到结构上的喜马拉雅高结晶序列（HHCS）。该边界是根据HHCS底部的胶粉岩中的以下岩相学特征定义的：（i）沿断面向上移动时，蓝晶石的细针首次出现; （ii）石榴石成岩细胞具有随机的包裹体模式和无旋转的生长历史，这与带有螺旋形包裹体踪迹的MCTZ岩石中的石榴石成岩细胞相反; （iii）化学均质的石榴石成卟啉细胞，与MCTZ岩石中生长带状的石榴石相反。伪剖面建模和石榴石等值热压法在MCTZ中产生的峰值变质条件为6.3-7.5 kbar和550-582°C，在HHCS基底部分为8.0-10.0 kbar和610-650°C。结果表明，MCTZ和HHCS之间接触的P-T场梯度是连续的。 MCTZ显示出从黑云母到石榴石带的反向变质序列。 HHCS基部的变质作用在蓝晶石带中，该区域与反向变质序列连续。 P和T都增加了截面，在较低的HHCS中达到峰值，然后在HHCS单元中的较高部分减小。这些观察结果与最近提出的热力学模型的预测一致，在该模型中，剪切带的温度由于粘性加热而升高，而由于岩石变弱而导致压力升高。

著录项

相似文献

  • 外文文献
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