Abstract Re-examination of specimens collected across the Qomolangma Formation exposed in the summit pyramid on Mount Everest confirms a complex, multi-deformational history. Two pre-Oligocene deformational events are recorded within the calcite-dominated rocks from the main summit (8848 m). The first event is characterized by an RXZ of ~1.3–1.4 in detrital quartz grains, which increases to ~1.6 after the second event. The finite strain recorded in calcite in the same rocks is higher with an RXZ of ~2.7–2.8. The deformation in the main summit appears to have been accommodated dominantly through grain boundary sliding in calcite in a slightly constrictive environment with a vorticity of >0.81. Deformation in the South Summit (8750 m) contrasts with that of the top and is instead interpreted to reflect Miocene movement along the Qomolangma detachment with no earlier deformation preserved. U–Pb geochronology on synkinematic rutile indicates that movement on the structure occurred at 16.3 ± 5.0 Ma. Rocks within the Qomolangma Formation in the summit pyramid of Mount Everest appear to record the basic history of the Himalaya with early deformation likely related to crustal thickening and later, more spatially restricted deformation reflecting the Miocene extrusion of the metamorphic core.

中文翻译：

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尼泊尔珠穆朗玛峰珠穆朗玛峰组构造演化

摘要 对在珠穆朗玛峰金字塔顶出露的珠峰组采集的标本进行重新检查，证实了其复杂的多变形历史。在主峰（8848 m）以方解石为主的岩石内记录了两个渐新世前的变形事件。第一个事件的特征是碎屑石英颗粒中的 RXZ 为~1.3-1.4，在第二个事件后增加到~1.6。相同岩石中方解石中记录的有限应变更高，RXZ 为~2.7-2.8。主峰的变形似乎主要通过方解石中的晶界滑动在略收缩的环境中得到调节，涡度 >0.81。South Summit (8750 m) 的变形与顶部的变形形成对比，而是被解释为反映了沿珠峰拆离的中新世运动，没有保留早期变形。同运动金红石的 U-Pb 年代学表明该结构的运动发生在 16.3 ± 5.0 Ma。珠穆朗玛峰顶峰金字塔珠穆朗玛峰组内的岩石似乎记录了喜马拉雅山的基本历史，早期变形可能与地壳增厚有关，后来，更多空间受限的变形反映了变质核的中新世挤压。