摘要
前人对华南扬子北缘"马槽园群"的形成年代长期争论不休,影响了对神农架地区晚前寒武纪地层的正确划分对比与沉积盆地分析。"马槽园群"被普遍认为是一套角度不整合于中元古代神农架群之上的新元古代早期磨拉石建造。笔者研究发现,"马槽园群"有多层火山岩。采自该群中部玄武岩的LA-ICP-MS锆石U-Pb年龄为(1 139±29)Ma。该年龄数据表明,"马槽园群"形成于中元古代,而不是前人所认为的新元古代,与神农架群为整合接触。"马槽园群"沉积地层中缺乏大陆环境的沉积构造,重力流沉积构造比较发育,应该形成于台缘斜坡—混积陆棚环境,并非前人认为的前陆盆地磨拉石建造。
The long disputes over the age of the Macaoyuan Group disturb the classification and correlation of the late Precambrian strata and basin analysis in the Shennongjia region,South China.The strata of the Macaoyuan Group have been widely thought to be the early Neoproterozoic molasse that overlie the Mesoproterozoic Shennongjia Group in unconformity.Our study has found that there are multi-layer volcanic rocks in the Macaoyuan Group.The LA-ICP MS U-Pb dating for the basalt at the middle part shows that it was generated at circa 1 139 ± 29 Ma,which indicates that it was formed in conformity with the Shennongjia Group in the Mesoproterozoic instead of Neoproterozoic.There exists no sedimentary structures of the continental depositional environments in the Macaoyuan Group,but those of marine gravity flow are commonly found.The Macaoyuan Group is thought to be deposited in the platform-margin and slope to mixed continental shelf instead of a foreland（Molasse） basin.
出处
《资源环境与工程》
2013年第3期328-334,共7页
Resources Environment & Engineering
基金
中国地质调查局计划项目(批准号:1212011121109
1212011220900)
国家自然科学基金重点项目(批准号:41030315)的资助
