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寇彩化,刘燕学,李廷栋,黄河,张恒.桂北地区丹洲群碎屑锆石LA-ICP-MS U-Pb年龄和Hf同位素特征及其地质意义[J].地质通报,2017,(8):1393-1406.
桂北地区丹洲群碎屑锆石LA-ICP-MS U-Pb年龄和Hf同位素特征及其地质意义    点此下载全文
寇彩化  刘燕学  李廷栋  黄河  张恒
中国地质科学院地质研究所, 北京 100037
基金项目:国家自然科学基金项目《江南造山带西段桂北新元古代基性-超基性岩岩石成因研究及其对构造演化的约束》(批准号:41402052)、中国地质科学院基本科研业务《湘西新元古代基性-超基性岩岩石年代学及成因研究》(编号:J1602)和中国地质调查项目《中国区域地质志》(编号:1212011120117)
DOI:
摘要:
      桂北丹洲群顶部拱洞组粉砂岩的碎屑锆石的阴极发光图像和Th/U(0.2~2.4)值显示,它们均为岩浆成因的锆石。锆石206Pb/238Pb年龄分布在730~769Ma和771~850Ma之间,这些锆石的Hf同位素成分范围较大,εHft)值和二阶段Hf模式年龄(TDM2)分别为-18.4~11.4和1020~2812Ma。此外,样品中还有一些年龄较老的锆石颗粒,207Pb/206Pb年龄为1910~3140Ma,εHft)值和二阶段Hf模式年龄(TDM2)分别为-13.6~3.4和2740~3635Ma。结合前人的研究推测,桂北丹洲群拱洞组沉积年龄小于等于706±10Ma,物源主要由扬子板块新元古代岩浆岩组成,也有少量太古宙岩浆岩的加入。推测中国华南地区存在对应于Rodinia超大陆聚合相关的格林威尔运动的响应。根据已测锆石的εHft)值和Hf二阶段模式年龄推断,研究区地壳生长主要经历3个阶段:①3.64~3.25Ga,初生地壳出现在3.64Ga;②2.98~2.37Ga;③2.19~1.28Ga,地壳生长的主要时期。
关键词:桂北丹洲群  碎屑锆石LA-ICP-MS U-Pb定年  Hf同位素  Rodinia超大陆  地壳生长
LA-ICP-MS U-Pb dating and Hf isotopes of detrital zircon grains from siltstone of Danzhou Group in northern Guangxi and their geological significance    Download Fulltext
KOU Caihua  LIU Yanxue  LI Tingdong  HUANG He  ZHANG Heng
Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
Fund Project:
Abstract:
      This paper reports LA-ICP-MS U-Pb dating and Hf isotopes for detrital zircon grains of siltstone from Gongdong For-mation at the top of the Danzhou Group. The majority of zircon grains are transparent, euhedral and prismatic crystals with oscillato-ry zoning in CL images and have high Th/U ratios of 0.2~2.4, indicating an igneous origin for the zircon. The 206Pb/238Pb age distri-butions for the detrital zircon grains mainly range from 730Ma to 769Ma and 771Ma to 850Ma, and εHf(t)and two-stage Hf model ages (TDM2) range from -18.4 to 11.4 and from 1020Ma to 2812Ma, respectively. Moreover, there are some detrital zircon grains with relatively older ages with 206Pb/238Pb ages from 1910Ma to 3140Ma, and εHf(t)and TDM2 from -13.6~3.4 and 2740~3635Ma, respec-tively. Combined with previous researches, the authors infer that the maximum depositional age of the Gongdong Formation from Danzhou Group is 706±10Ma. The source region was predominated by Neoproterozoic magmatic rocks from Yangtze Block (ca. 750~830Ma) with the mixture of minor Archean magmatic rocks. There was developed the Greenville movement in South China re-sulting from the assembly of Rodinia supercontinent. In addition, on the basis of the εHf(t)and TDM2 data of the detrital zircon grains, the authors hold the existence of three stages for the crust growth in the study area:①3.64Ga to 3.25Ga, with the juvenile crust at 3.64Ga; ②2.98Ga to 2.37Ga; ③2.19Ga to 1.28Ga.
Keywords:Danzhou Group in northern Guangxi  detrital zircon LA-ICP-MS U-Pb dating  Hf isotope  Rodinia supercontinent  crust growth
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