Evolution of the Continental Crust in the Northern Tibetan Plateau: Constraints From Geochronology and Hf Isotopes of Detrital Zircons
Evolution of the Continental Crust in the Northern Tibetan Plateau: Constraints From Geochronology and Hf Isotopes of Detrital Zircons
复制标题
DOI：
10.3389/feart.2022.866375
复制
发表时间：
2022-04
期刊：
影响因子：
--
通讯作者：
Zeyu Liu;Guibin Zhang;Lu Xiong;F. Chang;Shujie Liu
中科院分区：
文献类型：
--
作者：
Zeyu Liu;Guibin Zhang;Lu Xiong;F. Chang;Shujie Liu
结果表明，南祁连地体、北柴达木地体和东昆仑地体与西扬子地块有亲缘关系，其中锆石U-Pb年龄为443次，Hf同位素为244次。尤卡河群碎屑锆石的年龄分布主要在1000 ~ 700 Ma和480 ~ 400 Ma两个年龄区间。相应的ε Hf(t)值大多为负值，两段Hf模型年龄（TDM2）为2.1 ~ 1.6 Ga。沙柳河年龄分布在1000 ~ 700、460 ~ 380和260 ~ 200 Ma之间，TDM2年龄分布在2.0 ~ 1.6 Ga和1.6 ~ 1.2 Ga之间。此外，两河样品的新元古代锆石具有相同的古元古代TDM2年龄（2.0 ~ 1.6 Ga，峰值为1.8 ~ 1.7 Ga），表明南祁连、北柴达木和东昆仑地体可能属于同一新元古代大陆。推断东昆仑—柴达木北地体包含中元古代大陆地壳（1.6 ~ 1.0 Ga），表明东昆仑—柴达木北地体与祁连地体在地壳演化上存在差异。三个地体显生宙岩浆活动主要来源于古陆壳的再循环，幼陆壳的贡献较小。
To investigate the evolution of the continental crust in the northern Tibetan Plateau, detrital zircon U–Pb geochronology and Hf isotopes analysis were performed on two fluvial sand samples from North Qaidam (the Yuka and Shaliu rivers). A total of 443 detrital zircon U–Pb ages and 244 Hf isotopic results were obtained and reveal that the South Qilian, North Qaidam, and East Kunlun terranes show affinity to the western Yangtze Block. Age distributions of detrital zircons from the Yuka River cluster mainly in two age intervals of 1,000–700 and 480–400 Ma. The corresponding ε Hf(t) values are mostly negative, with depleted two-stage Hf model ages (TDM2) of 2.1–1.6 Ga. In contrast, age data for the Shaliu River fall in the ranges of 1,000–700, 460–380, and 260–200 Ma, with TDM2 ages of 2.0–1.6 and 1.6–1.2 Ga. In addition, zircons with Neoproterozoic ages from both river samples possess common Paleoproterozoic TDM2 ages (2.0–1.6 Ga, with a peak of 1.8–1.7 Ga), indicating that the South Qilian, North Qaidam and East Kunlun terranes were probably part of the same Neoproterozoic continent. The East Kunlun and North Qaidam terranes are inferred to include Mesoproterozoic continental crust (1.6–1.0 Ga), suggesting differences in crustal evolution between the East Kunlun–North Qaidam and Qilian terranes. Phanerozoic magmatism in these three terranes was sourced mainly from the recycling of ancient continental crust with minor contributions from the juvenile crust.