摘要
前人对皖南休宁县石岭头花岗质小岩株进行了K-Ar测年,结果为133.4Ma,属于早白垩世。笔者近期的野外地质调查发现,这些花岗质小岩株含过铝矿物堇青石,岩性特征与休宁花岗闪长岩体非常相近,为中粗粒花岗闪长岩,且见有变形,局部片理化明显。分别在休宁花岗闪长岩体内部和北部外叶村河中采集测年样品进行测定,获得休宁花岗闪长岩体内部835.4±32Ma和外叶小岩株841±29Ma的年龄,二者在误差范围内基本一致,表明它们属于同期岩体。岩石地球化学数据显示,花岗质小岩株具有与休宁花岗闪长岩体类似的地球化学特征,亏损Nb、Ta、Sr等高场强元素,富集K、Ru、Ba、U、Th,且均为强过铝质。结合前人所测休宁岩体数据对比分析,认为这些原先被认为早白垩世的花岗岩是新元古代的产物,为晋宁期休宁岩体的一部分,同时休宁岩体北界应北移约2km。其上覆盖的南华系休宁组砂岩应为超覆沉积形成。
The small granitic stocks in Xiuning granodiorite have K-Ar age of 133.4Ma,suggesting that these stocks were formed in Early Cretaceous.During recent field geological survey,the authors found that these small stocks contain aluminum mineral cordierite,and their lithologic characteristics are very similar to those of Xiuning granodiorite.They are all coarse grained granodiorite with local deformation and obvious schistosity.Samples collected from both internal Xiuning granodiorite and Waiye stock yielded LA-ICP-MS zircon U-Pb age of 835.4±32Ma for Xiuning granodiorite and 841±29Ma for Waiye rock,showing that they were formed during the same period.In addition,these small granitic stocks have similar geochemical characteristics to Xiuning granodiorite.Whole-rock geochemical data show that both samples are characteristics by lower HFSE Nb,Ta,Sr and higher K,Ru,Ba,U,Th,and thus belong to the peraluminous S-type granite.By comparative analysis of lithology characteristics,U-Pb age and geochemical data from previous study and this paper,the authors confirm that these stocks should intruded during the Neoproterozoic as a part of the Jinningian Xiuning pluton,not in the Early Cretaceous as previously thought.And the northern boundary of Xiuning pluton must have migrated northward for about 2km.The sandstone(no conglomerate)of Xiuning Formation resulted from the transgressive deposition on these stocks.
作者
刘秀
余心起
陈子微
李鹏举
周术召
杨鑫鹏
LIU Xiu;YU Xinqi;CHEN Ziwei;LI Pengju;ZHOU Shuzhao;YANG Xinpeng(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;School of Economics and Management,Sichuan University of Science & Engineering,Zigong 643000,Sichuan,China)
出处
《地质通报》
CAS
CSCD
北大核心
2019年第2期339-348,共10页
Geological Bulletin of China
基金
国家自然科学基金项目<浙赣皖相邻区中生代推(滑)覆构造特征及其时序分析>(批准号:41872201)
