| 中亚造山带南缘甘肃北山地区花牛山闪长玢岩地球化学特征及地质意义 |
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| 引用本文： | 王二腾,武磊,翟新伟,陈万峰,苏瑞欢,郭志昂,王赟,王金荣.中亚造山带南缘甘肃北山地区花牛山闪长玢岩地球化学特征及地质意义[J].地球科学,2022,47(9):3285-3300. |
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| 作者姓名： | 王二腾 武磊 翟新伟 陈万峰 苏瑞欢 郭志昂 王赟 王金荣 |
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| 作者单位： | 兰州大学地质科学与矿产资源学院, 甘肃省西部矿产资源重点实验室, 甘肃兰州 730000 |
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| 基金项目： | 第二次青藏高原科学考察研究项目2019QZKK0901中国地质调查局项目121201011000161111?01 |
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| 摘 要： | 为揭示中亚造山带南段洋?陆构造演化时限及动力学背景，对中亚造山带南缘北山地区花牛山晚古生代闪长玢岩进行年代学、主微量及Sr-Nd-Pb同位素研究.闪长玢岩LA-ICP-MS锆石U-Pb年龄为287.6±7.5 Ma，SiO2为53.92%~54.84%，K2O+Na2O为6.34%~6.82%，高Al2O3（14.66%~15.23%）低MgO（3.20%~3.99%），Mg#值为40.26~46.50；轻稀土元素富集（（La/Yb）N=20.07~21.33），弱负Eu异常（δEu=0.79~0.82）；明显富集Cs、Rb、Ba、K、Th及Pb，弱富集Zr和Hf，亏损Nb、Ta、Ti、P和Sr；（87Sr/86Sr）i值在0.707 009~0.708 799之间，（143Nd/144Nd）i值介于0.512 248~0.512 272，εNd（t）值为-0.39~+0.09.这些特征指示闪长玢岩源于地幔物质熔融，岩浆演化过程中发生地壳同化混染.结合区域地质背景，花牛山闪长玢岩的形成与北山南部辉铜山?帐房山洋盆北向俯冲闭合后的板内伸展构造背景相关，指示中亚造山带南缘北山南部于早二叠世时已经进入陆内构造阶段.
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| 关 键 词： | 闪长玢岩 地球化学 洋-陆构造转换 北山地区 中亚造山带 |
| 收稿时间： | 2021-10-15 |
Geochronology,Petrogenesis and Tectonic Implications of Huaniushan Diorite Porphyrite from the Gansu Beishan Area in the Southern Central Asian Orogenic Belt |
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| Abstract: | To reveal the tectonic dynamic setting and timing of the ocean-continent transform in the southern Central Asian Orogenic Belt (CAOB), the geochronological data, major and trace elements and Sr-Nd-Pb isotopes of Late Paleozoic Huanuishan diorite porphyrites in the Beishan area of southern CAOB are studied. The diorite porphyrites yield a magmatic crystallization of 287.6±7.5 Ma (LA-ICP-MS zircon U-Pb dating). The SiO2, K2O+Na2O contents are 53.92%-54.84%, 6.34%-6.82% respectively. The rocks have high Al2O3 (14.66%-15.23%), low MgO (3.20%-3.99%) with Mg# values of 40.26-46.50. The diorite porphyrites have high LREE enrichment ((La/Yb)N=20.07-21.33) with negative Eu anomalies (δEu=0.79-0.82), enriched in Cs, Rb, Ba, K, Th and Pb, weakly enriched in Zr and Hf, depleted in Nb, Ta, Ti, P and Sr. Their (87Sr/86Sr)i values range from 0.707 009 to 0.708 799, (143Nd/144Nd)i values 0.512 248 to 0.512 272, 206Pb/204Pb values 18.613 to 18.711 and εNd(t) values are -0.39-+0.09. These features suggest that diorite porphyrites were derived from the mantle material, with assimilation and contamination by curst. Combined with regional geological background, the diorite porphyrites were formed in an intraplate extensional tectonic stage after the northward subduction and closure of Huitongshan-Zhangfangshan Ocean. These results indicate that the southern Beishan area has completed the ocean-continent tectonic transform during the Early Permian. |
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