北秦岭西峡骨头崖花岗岩锆石U-Pb定年、地球化学特征及地质意义

发布时间：2018-05-25 09:23

  本文选题：骨头崖花岗岩 + U-Pb定年　； 参考：《地质论评》2017年06期

【摘要】：骨头崖花岗岩位于北秦岭构造带东部,西峡县北部,对其开展岩石成因研究有助于深入认识燕山期北秦岭豫西南段深部构造演化。岩体定年样品(GTY01)为中粒斑状黑云母二长花岗岩,30个锆石测点中有25个测点的U-Pb同位素测定值位于或者接近~(207)Pb/~(235)U ~(206)Pb/~(238)U一致线,23个测点的~(206)Pb/~(238)U年龄介于108.4±0.9Ma~114.3±1.0Ma之间,其加权平均年龄为111.7±0.6Ma(MSWD=1.4),代表了骨头崖花岗岩的形成时代。锆石稀土元素具有轻稀土亏损、重稀土富集、Ce正异常及负Eu异常的特征,形成温度介于626℃~769℃之间,岩体的锆石/熔体中重稀土元素特征表明,其形成过程中经历了岩浆混合作用。骨头崖花岗岩为富硅、碱和贫钙、镁的高钾钙碱性系列。岩体富集Rb、Th和亏损Nb、Ta、Ti。岩体的稀土配分模式具有右倾、轻稀土富集、重稀土亏损和负Eu异常的特征,(Eu值介于0.48~0.60之间,(La/Yb)_N范围为5.82~11.19,源区组成和部分熔融程度控制了骨头崖花岗岩的成分变异。骨头崖花岗岩形成于厚度为~40km的地壳内,其部分熔融源区为角闪岩相,部分熔融残余相主要为角闪石和斜长石。骨头崖花岗岩是岩石圈拆沉作用所触发的岩浆底侵作用的产物,从源区岩石部分熔融到最终上侵固结成岩耗时~15Ma,它是岩石圈拆沉作用滞后的岩浆响应。
[Abstract]:The Jiaoya granite is located in the east of the North Qinling tectonic belt and the north of Xixia County. The study of its petrogenesis is helpful to further understand the deep tectonic evolution of the southern segment of the North Qinling Mountains in the Yanshanian period. The U-Pb isotopic values of 25 of the 30 zircon sites are located in or close to the 235U / 235U / 238U consistent line, and the age of 238U is between 108.4 卤0.9Ma~114.3 卤1.0Ma for 23 of the 30 zircon sites, and the age of 238U is 108.4 卤0.9Ma~114.3 卤1.0Ma for 23 of the 30 zircon sites, and the U-Pb isotopic values of 25 of the 30 zircon sites are in the range of 108.4 卤0.9Ma~114.3 卤1.0Ma, and the U-Pb isotopic values of 25 of the 30 zircon sites are located at or close to the same line of 238U, and the age of 238U is between 108.4 卤0.9Ma~114.3 卤1.0Ma for 23 of the 30 zircon sites. The weighted mean age is 111.7 卤0.6 Ma MSWD1.4, which represents the age of formation of the bone cliff granite. Zircon rare earth elements have the characteristics of light rare earth deficiency, heavy rare earth enriched ce positive anomaly and negative EU anomaly, and the formation temperature is between 626 鈩，

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