安徽庐江—枞阳地区A型花岗岩的LA-ICP-MS定年及其地质意义  

LA-ICP-MS zircon U-Pb ages of the A-type granites in the Lu-Zong(Lujiang-Zongyang)area and their geological significances

作　　者：范裕[1] 周涛发[1] 袁峰[1] 钱存超[2] 陆三明[2] DAVID Cooke 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]安徽省公益性地质调查管理中心,合肥230001 [3]Centre of Excellence in Ore Deposits (CODES),University of Tasmania

出　　处：《岩石学报》2008年第8期1715-1724,共10页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划973项目(批准号:2007CB411405);高等学校博士学科点科研基金项目(批准号:20050359013);国家自然科学基金项目(批准号:40672062;40830426;40803015);安徽省地质勘查专项费项目(批准号:2005-48;2007-1);安徽省优秀青年科技基金项目(批准号:08040106907)资助

摘　　要：本文对安徽庐江—枞阳地区产出的 A 型花岗岩体(碱性侵入岩体)进行了锆石 LA-ICP-MS U-Pb 同位素年代学研究。结果表明,城山岩体、花山岩体、黄梅尖岩体和枞阳岩体的形成年龄分别为126.5±2.1Ma、126.2±0.8Ma、125.4±1.7Ma和124.8±2.2Ma,均形成于早白垩世126～124Ma 之间。这些岩体的硅含量和全碱含量均较高,准铝质;稀土含量中等,强 Eu亏损,呈略右倾的海鸥型稀土配分模式,均为 A1型花岗岩。结合长江中下游地区高碱钙碱性侵入岩和盆地内火山岩的研究成果,本文认为126～124Ma 是长江中下游地区地壳伸展最强烈的阶段,这一研究成果对探讨长江中下游地区早白垩世早期的动力学背景具有重要的意义。LA-ICP-MS zircon U-Pb dating for four A-type granites （ alkalic intrusions） such as Chengshan, Huashan, Huangmeijian and Zongyang intrusions in the Lujiang-Zongyang area was carried out in this paper. These intrusions consist of monzonite and quartz syenite which contain a lot of K-feldspar. The whole-rock analytical results of major,trace and rare earth elements of the rocks indicate that they belong to a typical A-type granitoid association. LA-ICP-MS zircon U-Pb datings yield the ages of 126. 5 ± 2. 1Ma, 126. 2 ± 0. 8Ma,125.4 ± 1.7Ma and 124. 8±2.2Ma for four intrusions, respectively. The results indicate that all A-type intrusions in the Lu-Zong basin formed in the Early Cretaceous from about 126Ma to 124Ma. These intrusions are characterized by relative high silica and alkalis, ascribed to metaluminous, has moderate REE and strong Eu depletion with a slightly right-inclined sea-gull REE pattern, all belonging to A1 type granites. These data, together with other accuracy dating data of volcanic rocks and intermediate-acid high-K calc-alkalic plutons in the Middle and Lower Reaches of the Yangtze River area, support the occurrence of intensive lithosphere thinning at 126 Ma to 124 Ma,the peak period of crustal extension in the district.

关 键 词：A型花岗岩 LA—ICP—MS定年 长江中下游 庐江—枞阳地区 地臻动力学 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]