科研之友
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摘要
Three relatively large intrusions locating in Fanchang district, the Lower Yangtze region, are Banshiling, Fushan and Binjiang plutons, rock types of which are dominantly quartz-monzonite, potassium feldspar granite and granite, respectively. Zircon LA-ICPMS U-Pb dating of three intrusions give quite accordant ages of 124.9 /- 1.7Ma, 126.4 /- 1.7Ma, 124.6 /- 4.7Ma (the coarse-grained phase of Binjiang pluton) and 123.0 /- 1.8Ma ( the fine-grained phase of Binjiang pluton), respectively. The Mesozoic magmatism occurred along the Lower Yangtze River can be divided into three stages. These plutons are formed simultaneously with other A-type granites along the Lower Yangtze River and belong to the third stage magmatism. Three intrusions are characterized by LREE-enrichment as well as varying degrees of negative Eu anomaly, with selective depleted characteristic of Ba and Sr depletion, an exclusive signature of A-type granite. The range of zircon epsilon(Hf) (t) and delta O-18 values of Banshiling intrusion is from -2.7 to -6.3, 6.7 to 7.4 and that of Fushan and Binjiang intrusions are from -1.6 to -7.9, 7.1 to 9.1 and 0 to -6.6, 8.0 to 10.3. Whole rock Sr-87/Sr-86((t)) and epsilon(Nd)(t) ratios for Banshiling, Fushan and Binjiang intrusions are 0.7072, -6.8, 0.7076, -7.7 and 0.7078, 3.4, respectively. Comprehensive analysis suggests that the Binjiang pluton formed by anatexis of the middle and upper crust represented by the Neoproterozoic granites. The magma formed Banshiling and Fushan plutons were underwent processes of magma mixing with different degrees which derived from mantle and crust, respectively. The petrogenesis and magmatic source of the three. stage magmatism in the Lower Yangtze region reveal a clearly deep geological process of evolution under an extension setting with increasing intensity during three magmatic stages.
- 出版日期2012-10
- 单位合肥工业大学
