福建明溪寒塘组地质特征及时代归属

Geological Features and Stratigraphical Time of Hangtang Formation in Mingxi County, Fujian Province

福建明溪北部寒塘地区出露一套低绿片岩相浅变质岩系 ,原划分为中—上元古界下峰 (岩 )组。经 1∶ 5万区调和剖面研究 ,现已查明其空间层位在万全 (岩 )群之上 ,并伏于盖洋群之下 ,其岩石组合、原岩建造与其上覆及下伏岩石地层差异明显 ,具自身特点 ,厚度较大 ,且区内有一定延伸性。因此 ,作者新创建寒塘组。据其与上覆、下伏地层关系及已取得的 930 Ma单颗粒锆石 U- Pb同位素年龄资料 ,将其时代归属青白口纪。该岩石地层单位的建立及其时代确定 ,对闽西北前寒武纪变质岩地层划分、区域对比及构造研究具有重要意义。

There is a suite of low greenschist facies of epimetamorphic rocks in Hangtang Area of Northern Mingxi County, Fujian Province, which was grouped under the Middle Upper Proterozoic Xianfeng Formation. Based on the results of 1:50000 regional geological survey and studying some geological sections, it was found that the horizon of the epimetamorphic rocks lies over the Wangquan Formation(Middle Proterozoic)and underlies the Gaiyang Group(late Sinian ) and that their rock association and protolith association have an obvious difference from their overlying and underlying strata and possess their characters such as a bigger thickness and some extension in the surveyed area. Therefore, the authors established a new stratigraphical unit-Hangtang Formation. According to the U Pb isotopic age (930 Ma) of the single zircon from the overlying and underlying strata, the Hangtang Formation is grouped under Qingbaikou epoch (Late Proterozoic). The establishment and dating of the lithological unit is of importance to the stratigraphical division of Pre Cambrian metamorphic rock, the matching of regional geology and the study of regional geological structures in Northern Fujian.