| 甘肃北山成宣地区二长花岗岩年代学、地球化学特征及其地质意义 |
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| 引用本文：杨怀玉,赵斌斌,张秦川,杨洁璇,王永强,陈静.2025.甘肃北山成宣地区二长花岗岩年代学、地球化学特征及其地质意义[J].地球学报,46(6):1149-1162. |
| DOI：10.3975/cagsb.2025.051621 |
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| 基金项目:甘肃省地勘基金项目“甘肃省敦煌市成宣铜镍矿普查(2024年续作)”(编号: 202401-D01)、甘肃省科技计划项目“甘肃北山地区镍钴成矿预测与找矿方法研究”(编号: 24YFGA014)、甘肃省局创新项目“敦煌地块北缘高尖山岩体-岩相划分与铜镍找矿方法研究”(编号: 2024CX01)；深地国家科技重大专项“荒漠戈壁；高寒草原浅覆盖景观区地球化学勘查新技术”(编号: 2024ZD1002400)和省级基础地质调查项目(编号: 甘财资环[2023] 26号) |
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| 中文摘要:为了解甘肃北山成宣地区二长花岗岩侵位时代、岩石成因, 进一步探讨北山造山带晚古生代构造演化, 本文基于详实的野外地质调查, 对成宣地区的二长花岗岩开展了岩相学、锆石U-Pb年代学、岩石地球化学特征研究。结果显示, 成宣地区二长花岗岩LA-ICP-MS锆石U-Pb加权平均年龄为(278.9±1.2) Ma, 形成时代为早二叠世。主量元素显示二长花岗岩具有较高含量的SiO2(73.51%~76.23%, 平均75.03%), Al3O2含量中等(12.49%~13.52%, 平均为13.01%), 较高的总碱(Na2O+K2O)含量(7.90%~8.33%, 平均8.13%), 较低含量的MgO(0.19%~0.63%, 平均为0.40%), A/CNK值为0.96~1.02, 表明成宣地区二长花岗岩为准铝质的高钾钙碱性系列岩石。微量元素相对富集大离子亲石元素Rb、Pb、K和不相容元素Th、U等, 强烈亏损Ba、Nb、P、Ti等高场强元素, 强烈负Eu异常以及右倾斜的“V”字海鸥曲线。结合区域地质背景, 可以认为成宣地区花岗岩体是壳幔混合成因的, 形成于早二叠世后碰撞伸展环境中, 研究区后碰撞花岗岩广泛分布，表明北山南缘在早二叠世已处于伸展环境。 |
| 中文关键词:二长花岗岩 岩石地球化学 二叠纪 北山地区 |
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| Chronological and Geochemical Characteristics of the Chengxuan Monzogranite in the Beishan Area, Gansu Province, and Their Geological Significances |
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| Abstract:To better understand the intrusion age and petrogenesis of monzogranite in the Chengxuan area, Beishan, Gansu, and to further assess the Late Paleozoic tectonic evolution of the Beishan orogenic belt, we conducted a detailed field geological survey and petrographic analyses and examined the LA-ICP-MS zircon U-Pb chronology and petrogeochemical characteristics of monzogranite in this area. The magmatic zircons of the monzogranite in Chengxuan have a weighted average U-Pb age of (278.9±1.2) Ma. The rocks have high SiO? contents (73.51%–76.23%, average 75.03%), total alkali (Na?O+K?O) contents ranging from 7.90% to 8.33% (average 8.13%), and low MgO contents (0.19%–0.63%, average 0.40%), with A/CNK and A/NK values of 0.96–1.02 and 1.04–1.08, respectively, indicating that the monzogranites are peraluminous and belong to a high-potassium calcium-alkaline series. Furthermore, the rocks are enriched in large-ion lithophile elements (Rb, Pb, and K) and incompatible elements (Th and U) but depleted in Ba, Nb, P, and Ti, with a strong negative Eu anomaly. Based on the regional geology, the above characteristics reflect that the Chengxuan granites were the mixing products of crustal and mantle derived magmas and formed under the tectonic setting of post-collisional extension in Early Permian. The post-collisional granites are widely distributed in the study area and that the southern margin of the Beishan Mountains reached a post-collisional evolutionary stage during the Early Permian. |
| keywords:monzogranite petrogeochemistry Permian Beishan area |
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