| 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 |
| 投稿时间：2024-12-17 修订日期：2025-02-27 |
| 关键词:monzogranite petrogeochemistry Permian Beishan area |
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| 摘要: |
| Chronological and Geochemical Characteristics of the Chengxuan monzogranite in the Beishan Area, Gansu Province, China, and Their Geological Significances |
| In order to understand the age of intrusion and petrogenesis of the diorite in Chengxuan area, Beishan, Gansu, and to further discuss the Late Paleozoic tectonic evolution of the Beishan orogenic belt, this paper is based on the detailed field geological survey and the study of petrography, zircon U-Pb chronology, and petrographic geochemical characteristics of the diorite in Chengxuan area. The results show that the LA-ICP-MS zircon U-Pb weighted average age of the Erchang Granite in Chengxuan is 278.9±1.2 Ma, and the formation age is Early Permian. The principal elements show that the diabase granite has a high content of SiO2 (73.51%~76.23%, average 75.03%), a medium content of Al3O2 (12.49%~13.52%, average 13.01), a high content of total alkali (Na2O+K2O) (7.90%~8.33%, average 8.13%), and a low content of MgO ( 0.19%~0.63%, average 0.40%), values of 0.96~1.02 for A/CNK and 1.04~1.08 for A/NK), suggesting that the dioritic granites of the Chengxuan area are quasi-aluminous, high potassium-calcium-alkaline series rocks. The relative enrichment of trace elements in the large ionic lithophilic elements Rb, Pb, K and incompatible elements Th and U, the strong loss of Ba, Nb, P, Ti and other high-field elements, the strong negative Eu anomaly, and the right-tilted V gull curve indicate that the ChengXuan diabase was formed in the post-collisional and extensional environment of the A2-type granite. The tectonic interpretation is based on the relevant tectonic diagrams. Based on the relevant tectonic diagrams and previous research results, this paper suggests that post-collisional granites are widely developed in the study area, indicating that the southern margin of the Beishan Mountain entered the post-collisional evolutionary stage in the Early Permian. |
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