安徽庐枞盆地隐伏侵入岩的LA-ICPMS定年及其构造意义  

LA-ICP MS Zircon U-Pb Dating for the Hidden Intrusions in the Lu-Zong Basin and Its Tectonic Significance

作　　者：范裕[1] 邱宏[1] 周涛发[1] 袁峰[1] 张乐骏[1,2] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]Centre of Excellence in Ore Deposit(CODES),University of Tasmania

出　　处：《地质学报》2014年第4期532-546,共15页Acta Geologica Sinica

基　　金：国家"深部探测技术与实验研究专项计划"专题(编号:SinoProbe-03-02-05);国家自然科学基金项目(批准号:41172084;41172086);国家重点基础研究发展规划973项目(批准号:2012CB416802);中国地质调查局地质调查工作项目(项目编号1212011121115)资助成果

摘　　要：庐枞中生代火山盆地位于长江中下游断陷带内,地处扬子板块的北缘。庐枞盆地内火山岩和侵入岩分布广泛,包括龙门院、砖桥、双庙和浮山4组火山岩以及34个出露地表的侵入岩体。这些侵入岩体的时空格架和岩浆演化等相关研究工作已经广泛开展,但对于盆地新发现深部隐伏岩体的研究尚未开展,制约了对庐枞盆地岩浆作用及深部成矿预测的深入研究。本次工作在详细野外地质工作的基础上,系统对盆地北部清水塘、刘墩、乔冲、牛头山、李家庄5个代表性隐伏岩体开展岩石学、地球化学和年代学研究,通过侵入岩详细镜下鉴定和锆石LAICP-MS U-Pb定年等方法,确定其主要岩性为二长岩和正长岩,岩石全碱含量均较高,准铝质或过铝质;稀土含量中等,较强Eu亏损,呈略右倾的海鸥型稀土配分模式,成岩时代分别为133.2±1.4Ma、131.3±1.3Ma、131.0±1.4Ma、131.2±1.2Ma和130.9±1.2Ma,均形成于早白垩世。通过与庐枞盆地不同侵入岩的系统对比,提出这些岩体与庐枞盆地早期侵入岩时代接近,岩石学特征类似,应为同一岩浆作用的产物,形成于区域岩石圈伸展的构造环境。The Luzong Mesozoic Volcanic Basin is located in the Middle-Lower Yangtze River fault-depression zone,which is located on the northern margin of the Yangtze Block.The volcanic and intrusive plutons occur widely in Luzong basin,including four groups of volcanic rocks,such as Longmenyuan Group, Zhuanqiao Group,Shuangmiao Group and Fushan Group and 34 intrusive plutons.Based on former geochronology research of outcropped plutons,LA-ICP MS zircon U-Pb dating for the hidden intrusions such as Qingshuitang,Liudun,Qiaochong,Niutoushan and Lijiazhuang intrusions in the north of the Lu-Zong basin was carried out in this paper.These intrusions consist of monzonite and quartz syenite which contain a lot of K-feldspar.LA-ICP MS zircon U-Pb dating yield the ages of 133.2±1.4Ma,131.3±1.3 Ma,131.0±1.4Ma,131.2±1.2Ma and 130.9±1.2Ma for five intrusions,respectively.The results indicate that all the hidden intrusions in the north of Lu-Zong basin formed in the Early Cretaceous.These intrusions are characterized by relative high silica and alkalis,ascribed to metaluminous or peraluminous, moderate REE and strong Eu depletion with a slightly right-inclined sea-gull REE patterns.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 hidden intrusions formed in a within-plate tensional tectonic environment.The results of the study are important for discussing the geodynamic settings of the hidden intrusions in the Middle and Lower Reaches of the Yangtze River area.

关 键 词：隐伏侵入岩 成岩时代 庐枞盆地 长江中下游成矿带 构造背景 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]