宁芜盆地火山作用峰期锆石U-Pb定年和Lu-Hf同位素研究  

Zircon U- Pb dating and Lu- Hf isotopic analysis of volcanic rocks from the Nanjing- Wuhu Basin in volcanism peak period

作　　者：杨颍鹤[1] 王丽娟[1] 张少琴[1] 

机构地区：[1]江苏省地质调查研究院,江苏南京210018

出　　处：《地质学刊》2015年第4期556-566,共11页Journal of Geology

基　　金：中国地质调查局项目"宁芜溧水火山岩盆地岩浆构造演化与成矿作用关系研究"(1212011120864);国家自然科学基金青年基金项目(41102123)

摘　　要：宁芜盆地是长江中下游重要的火山岩盆地之一,发育龙王山、大王山、姑山和娘娘山4期火山喷发旋回。盆地内火山作用峰期的大王山期和姑山期火山喷发旋回的安山岩样品的锆石定年和Hf同位素分析研究表明,大王山组2个安山岩年龄分别为(130.6±1.6)Ma和(132.6±1.8)Ma,姑山组安山岩年龄为(131.7±1.1)Ma,均为早白垩世。锆石^(176)Hf/^(177)Hf比值为0.282 468~0.282 607,ε_(Hf)(t)集中在-3^-6之间,结合前人的岩石地球化学数据,认为宁芜盆地火山岩源区可能主要为富集地幔,有少量地壳物质的混染。宁芜盆地火山作用峰期岩浆活动是太平洋板块俯冲作用减弱、发生后撤拉张背景下的产物。The Nanjing-Wuhu Basin is an important volcanic basin in the middle and lower reaches of the Yangtze River, which develops four stages of volcanic eruption cycles, i.e., the Longwangshan, Dawangshan, Gushan and Niangniangshan stages. This study conducted zircon dating and Hf isotopic analysis of andesite samples in the Dawangshan and Gushan stages volcanic eruption cycles of the volcanism peak periods. The result shows that the ages of the Dawangshan Formation andesites are （ 130.6±1.6） Ma and （ 132. 6±1.8） Ma, respectively, and the age of the Gushan Formation andesite is （131.7±1.1） Ma, all of which are in the Early Cretaceous. The zircon 176Hf/177Hf ratios range from 0.282 468 to 0.282 607, and the εHf（t） values lie in a narrow range of -3- -6. Combined with the previous lithogeochemical data, it is inferred that the volcanic rocks in the Nanjing-Wuhu Basin may be originated from enriched mantle, with little contamination from crustal materials. The magmatic activities during the volcanism peak time in this basin maybe result from the weakening subduction of the Pacific Plate and its subsequent tensional stress.

关 键 词：锆石U-PB年龄 HF同位素 火山岩 宁芜盆地 

分 类 号：P597[天文地球—地球化学]