北京延庆高于庄组凝灰岩的锆石U-Pb定年研究及其对华北北部中元古界划分新方案的进一步约束  

Zircon U-Pb dating on tuff bed from Gaoyuzhuang Formation in Yanqing,Beijing:Further constraints on the new subdivision of the Mesoproterozoic stratigraphy in the northern North China Craton

作　　者：李怀坤[1] 朱士兴[1] 相振群[1] 苏文博[2] 陆松年[1] 周红英[1] 耿建珍[1] 李生[1] 杨锋杰[3] 

机构地区：[1]天津地质矿产研究所,天津300170 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]山东科技大学地质科学与工程学院,青岛266510

出　　处：《岩石学报》2010年第7期2131-2140,共10页Acta Petrologica Sinica

基　　金：中国地质调查局国土资源大调查项目(1212010611802);国家自然科学基金项目(40772076);中石化海相前瞻性研究项目(YPH08086)联合资助

摘　　要：作者最近在北京延庆高于庄组张家峪亚组上部发现了凝灰岩,并测得了该凝灰岩中锆石1559±12Ma的SHRIMPU-Pb年龄和1560±5Ma的LA-MC-ICPMS U-Pb年龄。这一新的高精度定年结果表明,华北北部高于庄组形成于中元古代初期的盖层纪(Calymmian Period,1600~1400Ma)早期。结合早先大红峪组火山岩的锆石U-Pb年龄(1622~1625Ma),现在可以确切地将高于庄组的底界年龄限定在1600Ma左右。结合最近在铁岭组斑脱岩获得的锆石U-Pb年龄(~1440Ma),本文再次建议,应将华北中元古界蓟县系的底界下拉到高于庄组底界,自该组底部(1600Ma)到铁岭组顶部(1400Ma)的巨厚碳酸盐岩序列都属于新定义的蓟县系,并对应于国际中元古界的盖层系,高于庄组与大红峪组之间的界线则可作为蓟县系与长城系的分界标志。高于庄组凝灰岩锆石的精确定年,为华北北部中元古界年代地层划分等研究,提供了直接的年代学约束。A tuff bed in the upper horizon of Gaoyuzhuang Formation has been newly discovered in Yanqing County,Beijing.Two almost identical precise zircon U-Pb ages,1559±12Ma(SHRIMP)and 1560±5Ma(LA-MC-ICPMS),have been obtained for the tuff bed,which indicates that the Gaoyuzhuang Formation in the northern North China Craton was formed in the early stage of Mesoproterozoic Calymmian Period(1600~1400Ma).Combining with the available zircon U-Pb age data(1622~1625Ma)for the volcanics from the upper part of Dahongyu Formaiton,the lower boundary age of Gaoyuzhuang Formation could be accurately positioned at 1600Ma.Moreover,with the newly determined SHRIMP U-Pb age(~1440Ma)of the K-bentonite in Tieling Formation,the authors therefore propose again that the basal boundary of Gaoyuzhuang Formation should be taken as the lower boundary of Mesoproterozoic Jixian System.The voluminous carbonate succession from Gaoyuzhuang Formation to Tieling Formation with time span of 1600Ma to 1400Ma comprises the Jixian System,almost identically comparable with the international Mesoproterozoic Calymmian System.The new achievement in dating on the tuff of the Gaoyuzhuang Formation provides strong age constraints on the Meso-to Neoproterozoic stratigraphic subdivision and other relevant important scientific issues in the northern North China Craton.

关 键 词：华北克拉通 高于庄组 SHRIMP和LA-MC-ICPMS U-Pb定年 盖层纪 

分 类 号：P534.3[天文地球—古生物学与地层学]