摘要
江西武功山地区发育典型的穹隆花岗岩(变质核杂岩),该区中心部位出露中生代花岗岩类和花岗质片麻岩,近EW向展布的晚古生代—中生代萍乡、安福盆地分别位于其北、南两侧。武功山中生代花岗岩类以富SiO_2、K_2O,Rb、Th、LREE,贫Ba、Nb,且具明显Eu负异常为特点,同时花岗岩中含有夕线石、石榴子石等富铝矿物,表明属于S型花岗岩,反映陆内构造环境。与中生代花岗岩相比,山庄加里东期花岗闪长岩具有不同的岩石地球化学特点,I_(Sr)为0.7066,接近于Ⅰ型,其构造背景与大陆边缘岩浆弧环境较为相似。中生代花岗岩类具有3个不同的岩相分带,岩石学与地球化学研究表明,不同岩相带具有相似的岩石学和地球化学特征,说明武功山穹隆状花岗岩经历了从三叠纪到早白垩世的演化过程,武功山变质核杂岩伸展构造发育在一个古老的加里东期变质基底之上。通过对该区花岗岩类及花岗质片麻岩的岩石学、地球化学特征分析,为揭示穹隆花岗岩构造的形成机制和地球动力学背景提供了依据。
In South China, a typical granitic dome (metamorphic core complex) is developed in the Wugongshan area, Jiangxi Province. Its centre is occupied by Mesozoic granitoids and granitic gneisses, and the E-W-trending Late Paleozoic-Mesozoic Pingxiang and Anfu basins are located along its northern and southern sides, respectively. The petrological and geochemical (major, trace, and rare earth elements) characteristics of the granitoids and granitic gneisses suggest that the Wugongshan Mesozoic granitoids, containing characteristic minerals of sillimanite and garnet, have high SiO2, K2O contents, enriched in Rb and Th, and depleted in Ba and Nb. They also exhibit LREE-enriched patterns and marked negative Eu anomalies, indicating that they are peraluminous S-type granites. Compared with Mesozoic granitoids, the Caledonian Shanzhuang granodiorite has different petrological and geochemical characteristics, ISr= 0. 7066, showing a weak geochemical affinity to I-type granites. The Mesozoic granitoids, having higher ISr values (0. 7098-0. 7288) and lower εNd(T) ( - 10. 6 to -14. 7), consists of three petrological zones, that is, an Early Cretaceous massive granitic zone in the core (Zone Ⅰ), a foliated granitic zone (Zone Ⅱ) and a Triassic granitic gneissic zone in the outer-rim (Zone Ⅲ). The geochemical study suggests that these three zones have similar petrological and geochemical features, demonstrating that the Wugongshan granitic dome was subjected to a successive evolution from the Triassic to Early Cretaceous. The research results provide important geological and geochemical evidence for revealing the formation mechanism and geodynamical settings of the granitic dome.
出处
《地质论评》
CAS
CSCD
北大核心
2002年第1期80-88,共9页
Geological Review
基金
国家自然科学基金重点项目(编号40132010)
面上项目(编号40172067
40173001
