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野外地质关系及岩相学、地球化学、同位素和年代学研究表明,成水泉片麻状花岗岩是典型的原地改造型花岗岩,其原岩(即围岩)为糜棱岩化花岗闪长岩。本次锆石 LA-ICP-MS U-Pb 定年获得其原岩糜棱岩化花岗闪长岩~(206)Pb/~(238)U 加权平均年龄为369.9±5.6Ma(MSWD=36),片麻状花岗岩锆石核部年龄为367.9±5.4Ma(MSWD=2.2),此年龄与其原岩年龄在误差范围内一致,为片麻状花岗岩原地改造成因提供了年代学证据。此外,还获得其锆石热液增生边不一致线下交点年龄254±10Ma(MSWD=1.4),该年龄代表了片麻状花岗岩的形成时间。片糜状花岗岩在地球化学上继承了许多原岩的特征,同时又受到了深源流体-熔体的显著影响。将原岩糜棱岩化花岗闪长岩改造成片麻状花岗岩的流体-熔体具有富硅富钾和正ε_(Nd)(t)值的特征,表明这种流体-熔体可能主要地来自幔源岩浆内侵体,以及在内侵岩浆热量作用下的初生地壳岩石的变质和熔融。原岩糜棱岩化花岗闪长岩及其派生的片麻状花岗岩ε_(Nd)(t)值分别为+3.87及+3.05～+6.09,表明糜棱岩化花岗闪长岩源自于年轻的陆壳,而片麻状花岗岩除继承了其原岩糜棱岩化花岗闪长岩的高ε_(Nd)(t)值这一特征外,还可能受到了深源流体-熔体中幔源组分的影响。咸水泉岩体的实例研究表明,原地改造型片麻状花岗岩不但可以形成于造山带的挤压-伸展转折阶段,还可以形成于碰撞后进一步伸展的时期,而经过强烈韧性剪切的岩石是转变为片麻状花岗岩的最有利原岩。东天山咸水泉、平顶山和天湖东等原地改造型片麻状花岗岩的形成均与内侵有关,因而片麻状花岗岩可被看作是内侵的重要产物。
Field geological relationships and petrography, geochemistry, isotopes and geochronology studies show that the Chengshuiquan gneissic granite is a typical in situ remolded granite, the original rock (ie, the surrounding rock) mylonitized granodiorite rock. The weighted average age of ~ (206) Pb / ~ (238) U in the protolith mylonitized granodiorite was 369.9 ± 5.6 Ma (MSWD = 36) obtained from U-Pb dating of LA- The age of zircons in the gneissic granite is 367.9 ± 5.4Ma (MSWD = 2.2). This age is consistent with the original rock age within the error range, which provides the chronological evidence for the genetic modification of the gneissic granite. In addition, the age of 254 ± 10 Ma (MSWD = 1.4) at the inconsistency line of zircon hydrothermal accretion edge was also obtained, which indicates the formation time of gneissic granite. Micellar granite has geochemically inherited many of the characteristics of the original rock, while being significantly affected by deep-source fluid-melt. The fluid-melt transformation of the protolith mylonitized granodiorite into gneissic granite has the characteristics of silicon-rich potassium and positive ε_ (Nd) (t) values, indicating that this fluid-melt may be predominantly From mantle-derived magmatic intrusions, and metamorphic and melted primary crustal rocks under the intrusion of magma. The ε_ (Nd) (t) values of protolith mylonitized granodiorite and its derived gneissic granite are +3.87 and +3.05 ~ + 6.09, respectively, suggesting that the mylonitic granodiorite is derived from In the young continental crust, the gneissic granite may inherit the characteristics of high-ε Nd Nd value of mylonitized granodiorite from its original source rocks, Influence of mantle source components in the body. The case study of Xianshuiquan rock body shows that in situ modified gneissic granite not only can be formed during the extrusion-extension transition of the orogenic belt, but also can be formed during the period of further extension after collision, while the rock subjected to intense ductile shearing Is the most favorable original rock transformed into gneissic granite. The formation of the in situ remodeled gneissic granites in the eastern Tianshan such as Saline Springs, Pingdingshan and Tianhu East are all related to the intrusions, so that the gneissic granite can be regarded as an important product of intrusion.