摘要
高山河群是熊耳群之上最古老的沉积盖层和中元古代早期沉积作用记录最丰富的层位之一。本次研究在洛南-卢氏地区由下至上依次选择沉凝灰岩和石英砂岩进行碎屑锆石年代学、岩石地球化学和Nd同位素组成分析。研究发现,沉凝灰岩中碎屑锆石显示2309±3Ma(MSWD=3. 2,N=63)的特殊年龄峰值,与"静寂期"岩浆作用密切相关,全岩Nd同位素组成与熊耳群火山岩特征一致,εNd(t=1700Ma)=-13. 2^-3. 8,对应t2DM为2. 51~3. 26Ga,暗示太古宙地壳物质对岩浆源区有很大贡献。层位由底界上移,石英砂岩的成熟度逐渐降低,表明来自沉积再循环的物质减少;εNd(t)由-11. 9^-8. 3变化至-0. 8^+0. 5又至-8. 2^-2. 4,显示源区分别来自富集地幔-弱亏损地幔-富集地幔的"多元性"特征;相应地,碎屑锆石年龄主峰值从1850~2100Ma逐渐变化为2200~2300Ma和~2500Ma,表明沉积物源的多元性还与物质组分差异有关。高山河群沉积碎屑岩中最年轻的谐和锆石年龄集中于1760~1770Ma,限定了其最早沉积时限。结合上覆地层官道口群底界1600~1610Ma,确定高山河群是华北南缘"长城系"的重要组成部分。碎屑物质主要来自古元古代中-晚期1800~1900Ma、1950~2100Ma、2200~2350Ma和新太古代~2500Ma、2600~2700Ma,与燕辽地区长城系记录的华北克拉通前寒武纪基底构造热事件基本一致,二者在区域上具有可对比性。
The Gaoshanhe Group is one of the oldest sedimentary strata overlain the Xiong’er volcanic province along the southern margin of the North China Craton( NCC),with abundant Mesoproterozoic depositional records. In this paper,sedimentary tuff and quartz sandstone samples are selected from the bottom to the top to study in detrital zircon U-Pb age,lithogeochemisty and Nd isotopic composition. Detrital zircons from the bottom sedimentary tuff yield a distinct age peak of 2309 ± 3 Ma( MSWD = 3. 2,N = 63),showing a close relationship with the global magmatic shutdown period. These tuff have εNd( t = 1700 Ma)=-13. 2 ^-3. 8 and the corresponding t2 DM ages are from 2. 51 Ga to 3. 26 Ga,which resemble that of the Xiong’er volcanics,suggesting the Archean crust contributed much to their both magma source. Notably,the maturity is reduced when sandstone layer deposit upwards,meaning materials from sedimentary recirculation is less. The εNd( t) values are varying from-11. 9 ^-8. 3 to-0. 8 ^+ 0. 5 and to-8. 2 ^-2. 4,corresponding with the dominate age peaks from 1850 ~ 2100 Ma to 2200 ~ 2300 Ma and to ~ 2500 Ma. The multi-source are involved from enrichment to weak deplete and to enrichment,also resulted from component differentiation. The youngest concordant zircon grains are concentrated among 1760 ~ 1770 Ma and the overlain Guandaokou Group has been constrained younger than 1600 ~1610 Ma,implicating the Gaoshanhe Group should be a part of the "Changcheng"System in the southern margin of the NCC. Zircon grains of the Gaoshanhe quartz sandstones are from mid-late Paleoproterozoic 1800 ~ 1900 Ma,1950 ~ 2100 Ma,2200 ~ 2350 Ma and Neoarchean ~ 2500 Ma,2600 ~ 2700 Ma,in accordance with the material source of the Changcheng System in Yanliao area,suggesting they should be comparative in sequence stratigraphy.
作者
祝禧艳
仇一凡
庞岚尹
翟明国
ZHU XiYan;QIU YiFan;PANG LanYin;ZHAI MingGuo(Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China;Key Laboratory of Mineral and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;University of Chinese Academy of Sciences, Beijing 100049, China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第8期2487-2502,共16页
Acta Petrologica Sinica
基金
国家自然科学基金重点项目(41630211)、面上项目(41872198)和重大项目(41890834)
中国科学院前沿科学重点研究计划项目(QYZDY-SSW-DQC017)联合资助
关键词
华北南缘
高山河群
碎屑沉积岩
物质源区多元性
区域地层对比
Southern margin of the NCC
Gaoshanhe Group
Clastic sedimentary rocks
Multi-source
Regional stratum comparison
