海南地块形成与拼合时限:来自早石炭世变质粉细砂岩中碎屑锆石年代学的约束  

Formation and Amalgamation Time of Hainan block: Constraints from the Detrital Zircons U-Pb Geochronology on Early Carboniferous Metasiltstone

作　　者：龙文国 王晶[1] 谭满堂 王磊 王祥东[1,2] 吴俊 李岩[1,2] LONG Wen-Guo;WANG Jing;TAN Man-Tang;WANG Lei;WANG Xiang-Dong;WU Jun;LI Yan(Wuhan Center,China Geological Survey(Geosciences Innovation Center of Central South China),Wuhan 430205,Hubei,China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan 430205,Hubei,China)

机构地区：[1]中国地质调查局武汉地质调查中心(中南地质科技创新中心),湖北武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205

出　　处：《华南地质》2023年第2期259-277,共19页South China Geology

基　　金：中国地质调查局项目(DD20230226、DD12120113066400、DD20160031、DD20190047)。

摘　　要：原-古特提斯洋的闭合时限及其缝合带的具体位置对理解特提斯洋构造演化具有非常重要的意义。本文采用碎屑锆石年代学方法,分析了海南岛乐东-定安断裂两侧早石炭世沉积物源的特征,结合志留纪时沉积物源的特征,解译了其物源变化所指示的原-古特提斯洋盆闭合时限。碎屑锆石年代学显示,乐东-定安断裂东侧志留纪兰多维列世保脚村组和足赛岭组中最年轻一组碎屑锆石年龄为420~500 Ma,西侧志留纪兰多维列世陀烈组中碎屑锆石年龄均大于1100 Ma,二者显示出不同的年龄数据及谱系特征,应分属两个不同块体上沉积区的产物;不同于兰多维列世,乐东-定安断裂东西两侧早石炭世南好组中碎屑锆石年龄值分别为343~2465 Ma与365~2742 Ma,二者具相同的年龄数据及谱系特征,暗示接收相同的物源,应属同一块体上相同沉积区的产物,表明琼西北地块与琼东南地块在早石炭世已拼合成了统一的海南地块。综合区域上的其他地质资料,笔者认为琼东南地块与琼西北地块间的原-古特提斯洋盆的最终闭合时限应该在晚泥盆世,乐东-定安断裂可能是琼东南地块与琼西北地块之间的原-古特提斯洋盆闭合的位置。The determination of the closure timing and the exact suture location of the Proto-to Paleo-Tethys is crucial for understanding the tectonic evolution of the Tethys. In this study, we used detrital zircon geochronology to examine the features of Early Carboniferous sediment sources on both sides of the Ledong-Dingan fault in Hainan Island. Combined with the characteristics of Silurian sediment sources, we interpreted the closure timing of the Proto-to Paleo-Tethys Ocean indicated by the change in sediment sources. Detrital zircon geochronology revealed that the youngest batch of detrital zircon ages in the Llandoverian Baojiaocun and Zusailing Formation on the eastern side of the Ledong-Dingan fault ranged from 420 Ma to 500 Ma, while Llandoverian Tuolie Formation on the west were all older than 1100 Ma. The different age data and lineage features shown suggested that they would have been the products of sedimentation areas of two distinct tectonic blocks. In contrast to the Llandoverian, the detrital zircon age in the Early Carboniferous Nanhao Formation on both sides of the Ledong-Dingan fault ranged from 343 Ma to 2465 Ma and 365 Ma to 2742 Ma respectively, showing similar age data and lineage features. This implied that they shared the same sediment source and could be the products of the same sedimentation area on a single tectonic block, indicating that the Qiongxibei block(Northwest Hainan Island) and Qiongdongnan(Southeast Hainan Island) block could have been amalgamated into a single Hainan block by Early Carboniferous. By combining with other geological data, we propose that the final closure of the Proto-to Paleo-Tethys Ocean between the Qiongdongnan and Qiongxibei block likely occurred during the end of the Late Devonian, and the Ledong-Dingan fault could represent the suture marking the closure location of the Proto-to Paleo-Tethys basin between these two blocks.

关 键 词：南好组 早石炭世 碎屑锆石 原-古特提斯 乐东-定安断裂 海南地块 

分 类 号：P56[天文地球—构造地质学] P534.45[天文地球—地质学]