Zircon U-Pb Dating of High-K Calc-Alkaline Intrusive Rocks from Tongling: Implications for the Tectonic Setting
详细信息
- 责任者：Wu Cailai (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Guo Xiangyan
- 刊名：Geochimica
- 出版年：2013
- 卷期：42(1)
- 关键词：侵入体 ; intrusions ; 铀—铅计时 ; U-Pb dating ; 安徽 ; Anhui Province
- 页码：p.11-28
- 图表：illus., 4 tables, 43 refs.
- 分类号：0801
- issnNo：ISSN0379-1726
- isbnNo：CN44-1398/P
摘要
High-K calc-alkaline intrusions from the Tongling district consist mainly of quartz monzodiorite(porphyrite) and granodiorite(porphyry),with lesser amounts of gabbro-diorite.In this paper,we report new zircon U-Pb ages and geochemical results for those rocks.The dating results show that Nanhongchong and Shatanjiao granodiorites,Xinqiaotou granodiorite porphyry and Miaojia quartz monzodiorite porphyrite have zircon SHRIMP U-Pb ages of(138.8±1.3) Ma,(144.1±1.2) Ma,(147.2±1.5) Ma and(142.8±1.6) Ma respectively.LA-ICPMS zircon U-Pb ages of the Shatanjiao and Miaojiao plutons are(144.1±1.5) Ma and(143.2±1.3) Ma,respectively,in good agreement with their SHRIMP zircon U-Pb ages.When combined with previous geochronological data,the results presented here indicate that the rocks with porphyrtic texture are older than those without porphyritic textures for the same type rocks.The same type rocks also have different ages,e.g.,Nanhongchong granodiorite is younger than other ones from the area,which may reflect multistage intrusive magmatism.The intrusive sequence of the high-K calc-alkaline rocks can be generalized as: granodiorite porphyry / the first intrusive granodiorite → gabbro-diorite / the first intrusive pyroxene monzodiorite → quartz monzodiorite porphyrite/quartz monzodiorite → the second intrusive granodiorite → the second intrusive pyroxene monzodiorite.High-K calc-alkaline intrusions in Tongling coincided temporally with the Late Jurassic to Early Cretaceous magmatic event widespread in the southeast China,indicating that the regional tectonics in southeast China switches from the Late Jurassic transpressive to the early Cretaceous extensional regimes.