摘要
位于华北克拉通东南缘的蚌埠隆起带随着扬子陆块与华北陆块碰撞、拼接,经历了较为复杂的演化过程,本文选取其中早白垩世晚期的7个二长花岗岩侵入体进行野外观察和年代学研究,获得的年龄集中于114.6±3.3~121±1.0Ma;地球化学数据显示了其富硅、富碱的钙碱性准铝-铝弱饱特征,LREE相对富集,具弱铕负异常,铈异常不明显,K、P和Ti元素有较明显的亏损,Rb、Ta、Sr和Nd元素相对富集,具备陆壳为主的源岩深熔作用的特征。K_2O-Na_2O及SiO_2-Zr成因类型判别图上,侵入体投影点分布于Ⅰ型花岗岩区域,ε_(Hf)(t)全部为负值且相对较低(-25.2^-15.61),说明其为壳源成因,两阶段Hf模式年龄(2.17~2.76Ga),说明其物质起源主要为新太古宙陆壳物质,结合华北克拉通主体形成时间暗示其岩浆源区主要为华北克拉通下地壳物质。随着地壳增厚和下地壳-岩石圈的拆沉作用而引发的大规模岩浆活动,增厚的下地壳底部发生部分熔融,导致地壳快速隆升和随后的伸展,古老的陆壳物质经过改造和再循环,形成区内早白垩世晚期二长花岗岩。
The Bengbu uplift,located in the southeastern margin of the North China Craton,experienced a more complex evolution process,in company with the collisions and stitching of the Yangtze platform and north China continental block.Authors collected seven samples from monzonite granite intrusions of late Early Cretaceous to conduct field observation and geochronological study.The ages obtained concentrate around 114.6±3.3 Ma～121±1.0 Ma.Geochemical data show that the rocks are characterized by Si-and alkalirich,calcium alkaline,weak Al-saturation,relative REE enrichment,weak negative Eu anomaly and no obivious Ce anomaly,distinct depletion of K,P an Ti,and relative enrichment of Rb,Ta,Sr and Nd,suggesting that the source rocks consisting mainly of continental crust experienced anatexis.K2O-Na2O and SiO2-Zr discrimination diagram shows that all points fall into I-type granite area.Epsilon Hf（t）values are all negative with relatively low values of-25.2～-15.61,indicating its crustal origin.Two stages of Hf model age（2.17～2.76 Ga）suggests that the rocks sourced dominantly from Neo-Archean continental crust material.Combined with the formation time of the North China Craton,this study concludes that magma source area was mainly lower crust material under the North China Craton.Crustal thickening and delamination of lower crust and lithosphere caused large-scale magmatic activity.Partial melting of thicken lower crust resulted in rapid uplift of the earth＇s crust and subsequent stretching.Modifying and recycling of the ancient continental crust material gave a rise to the formation of the monzonitic granite during late Early Cretaceous.
作者
康丛轩
杨献忠
蔡逸涛
宗雯
黄先觉
孔广林
李朝维
KANG Congxuan;YANG Xianzhong;CAI Yitao;ZONG Wen;HUANG Xianjue;KONG Guanglin;LI Chaowei(Nanjing Center of Geological Survey, CGS, Nanjing , 210016,China;School of Earth Sciences and Engineering, Hohai University, Nanjing, 210016,China;Geological Survey of Jiangsu Province, Nanjing, 21 O018, China 312 Geological Team of Geology and Mineral Resources Exploration Bureau in Anhui Province, Bengbu, Anhui, 233040,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2018年第4期687-703,共17页
Acta Geologica Sinica
基金
安徽省公益性地质调查基金(项目编码:2014-K-5)资助的成果
关键词
华北克拉通
蚌埠隆起带
二长花岗岩
早白垩世晚期
动力学背景
North China Craton
Bengbu uplift
monzonitic granite
late Early Cretaceous
geodynamic background
