地质学报2017，Vol.91Issue(3)：571-587,17.
浙江大桥坞铀矿床火山岩锆石形态学与年代学研究
Zircon Morphology and Geochronology for Volcanic Rocks in the Daqiaowu Uranium Deposit, Zhejiang Province
摘要
Abstract
The Daqiaowu uranium deposit,located in the eastern Gan-Hang Tectonic Belt (GHTB) is hosted in volcanic-intrusive complex.But timimg of episodic volcanic eruptions in this area is still controversial,and the volcanic rocks have been lack of accurate geochronological data.Thus,this study focuses on zircon morphology and geochronology of volcanic rocks and their granitic breceias to elucidate the volcanism in the Daqiaowu area.Morphological results obtained by scanning electronic microscopy indicate that zircon crystal types of volcanic rocks in the Huangjian Formation are mainly S24,S25,P3,P4 and P5.Typological statistics suggest that the magma of volcanoclastic rocks from the upper Huangjian Formation is alkaline,while that from the upper Huangjian Formation is calc-alkaline to alkaline.Zircon U-Pb dating suggests that the upper and lower Huangjian Formations were formed at 128 Ma and 133 ～ 135 Ma,respectively.These characteristics imply that they could be ascribed to different volcanic eruptions.The crystallization age of granitic breccias is 138 Ma,which represents the earliest magmatism in the Daqiaowu area,suggesting a possible basement of granitic intrusive body under volcanoclastic rocks.Based on the geochronology,petrography and drill cores,the volcanic eruption cycles in the Daqiaowu area can be divided into following stages:①the formation of a basement of granitic intrusive body (138 Ma);②Early stage of volcanic eruption (136 Ma),the Laocun Formation was formed with red conglomerate and volcanic sedimentary rocks;③intense volcanic eruption stage,this stage can be divided into two subcycles.The early subcycle,named the lower Huangjian Formation,was formed at 135～133 Ma and mainly composed of massive ignimbrite.The late subcycle,named the upper Huangjian Formation,was formed at 128 Ma and composed of greyish-white to greyish-green tuff and breccia-bering crystal tuff;④dike intrusion stage,granite and diabase dikes were formed during 128 ～ 125 Ma;⑤late eruption stage,shale,fine-grained sandstone,tuff and crystal tuff of the Shouchang Formation were formed at 123 Ma.Volcanic rocks along the GHTB were formed during the Early Cretaceous,and volcanic activities were more intense in the eastern part of GHTB than in the western part.In addition,Uranium-bearing volcanic sequences in the eastern part are younger than those in the western part,and mainly have ages of 135～127 Ma.关键词
锆石形态学/U-Pb年代学/火山碎屑岩/早白垩世/大桥坞铀矿床/赣杭构造带Key words
zircon morphology/U-Pb geochronology/volcanoclastic rocks/Early Cretaceous/Daqiaowu uranium deposit/Gan-Hang Tectonic Belt引用本文复制引用
王洪作,陈培荣,吴俊奇,凌洪飞,赵友东,任海涛..浙江大桥坞铀矿床火山岩锆石形态学与年代学研究[J].地质学报,2017,91(3):571-587,17.基金项目
本文为国家重点基础研究发展计划“973”项目(编号2012CB416703)和中国核工业地矿事业部十二五高校基础科研项目联合资助的成果. （编号2012CB416703）
