胶东栖霞闪长玢岩脉中花岗岩捕虏体地球化学、锆石U-Pb年龄、Lu-Hf同位素研究及地质意义
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P581.12+1;P597

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山东省地勘基金项目[鲁勘字(2018)19号,(2023)3号]


Geological significance of granite xenoliths in Qixia diorite porphyrite vein, Jiaodong: Geochemical characteristics, zircon U-Pb age and Lu-Hf isotope constraints
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    摘要:

    胶东地区晚侏罗世玲珑期花岗岩主要出露于招远、莱州、文登、乳山等地区,主要包括玲珑岩体和鹊山-昆嵛山岩体,而两者之间的栖霞地区主要出露太古宙TTG类岩石。本次在栖霞地区上曲家村闪长玢岩脉(围岩为TTG类岩石)中发现较多中粒二长花岗岩捕虏体,锆石SHRIMP U-Pb年龄为161.0±2.2 Ma,176Hf/177Hf值为0.281 929~0.281 971,εHf(t)值为-26.39~-24.77,亏损地幔二阶段模式年龄tDM2为2 871~2 773 Ma,岩石地球化学特征显示,二长花岗岩捕虏体具有富钾、高铝、贫镁和铁的特征,为过铝质高钾钙碱性岩石,亏损重稀土元素,轻重稀土元素分馏明显, (La/Yb)N值变化在28.11~78.50之间,有明显的Eu正异常(Eu/Eu*=1.16~1.77),大离子亲石元素Rb、K、Ba、Sr相对富集。其同位素年代学、岩相学、岩石地球化学特征与玲珑岩体、鹊山-昆嵛山岩体基本一致,是在古太平洋板块的运动背景下,扬子板块与华北板块陆陆碰撞加厚的地壳部分熔融的结果,物源区以TTG类岩石为主,本文认为这些二长花岗岩捕虏体归属为玲珑期花岗岩。结合区域重力异常解译,认为栖霞地区TTG类岩石下部有隐伏的玲珑期花岗岩体,推测范围西起陡崖断裂,东至桃村断裂,南至胶莱盆地北缘,北至臧家庄盆地南缘,玲珑岩体和鹊山-昆嵛山岩体在深部可能是连通的。

    Abstract:

    Late Jurassic granite in Jiaodong area is mainly exposed in Zhaoyuan, Laizhou, Wendeng, Rushan and other areas, including Linglong pluton and Queshan-Kunyushan pluton. In between, the Qixia region is dominated by Archean TTG-type rocks. This time, many meso-grained monzogranite xenoliths were found in the diorite porphyrite veins (surrounding rock is TTG type rock) in Shangqujia village, Qixia area, the SHRIMP U-Pb age of zircon from monzonitic granite is 161.0±2.2 Ma. The ratio of 176Hf/177Hf ranged from 0.281 929 to 0.281 971, the εHf (t) was -26.39 to -24.77, tDM2 was 2 871 to 2 773 Ma. The monzogranite xenoliths are characterized by high potassium, high aluminum,low magnesium and iron. They are peraluminous, high potassium calc-alkaline rocks, which are deficient in heavy rare earth elements and have obvious fractionation of light and heavy rare earth elements. The ratio of (La/Yb)N varies from 28.11 to 78.50, there are obvious Eu positive anomalies (Eu/Eu*=1.16~1.77), and the large ion lithophilic elements Rb, K, Ba and Sr are relatively enriched. Its isotopic geochronology, petrology, and rock geochemical characteristics are basically consistent with those of the Linglong pluton and the Queshan-Kunyushan pluton. It is the result of partial melting of the crust thickened by the collision between the Yangtze plate and the North China plate under the background of the movement of the ancient Pacific plate. The source area is mainly composed of TTG type rocks. This article believes that these diorite xenoliths belong to the Linglong period granite. Based on the interpretation of regional gravity anomalies, it is believed that there is a hidden Linglong period granite body in the lower part of TTG rocks in the Qixia area. It is speculated that the range extends from the Douya fault in the west to the Taocun fault in the east, to the northern edge of the Jiaolai Basin in the south, and to the southern edge of the Zangjiazhuang Basin in the north. The Linglong pluton and the Queshan-Kunyushan pluton may be connected in the deep part.

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于晓卫,任天龙,程蓉蓉,等, 2025. 胶东栖霞闪长玢岩脉中花岗岩捕虏体地球化学、锆石U-Pb年龄、Lu-Hf同位素研究及地质意义[J]. 岩石矿物学杂志, 44(1):1~23.
YU Xiao-wei, REN Tian-long, CHENG Rong-rong, et al, 2025. Geological significance of granite xenoliths in Qixia diorite porphyrite vein, Jiaodong: Geochemical characteristics, zircon U-Pb age and Lu-Hf isotope constraints[J]. Acta Petrologica et Mineralogica, 44(1): 1~23.

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  • 收稿日期:2023-07-07
  • 最后修改日期:2024-04-18
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  • 在线发布日期: 2025-01-15
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