U-Pb Ages and Hf Isotopes of Detrital Zircon Grains from the Mesoproterozoic Chuanlinggou Formation in North China Craton: Implications for the Geochronology of Sedimentary Iron Deposits and Crustal Evolution

Minerals

Chao Duan¹  Kejun Hou¹  Yanhe Li¹  Minghui Wei²  Yun Yang²  Yongsheng Liang² 

[1] Ministry of Natural Resources Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;No. 3 Geological Brigade, Hebei Geological and Mineral Exploration Bureau, Zhangjiakou 075000, China;

关键词: Chuanlinggou Formation;    detrital zircon U-Pb age;    Hf isotope;    sedimentary iron deposit;    North China Craton;   

DOI  :  10.3390/min8120547

来源: DOAJ

【 摘 要 】

The Chuanlinggou Formation is the lower formation of the Changchengian System, and hosts sedimentary iron deposits (marine oolitic ironstones) of the North China Craton (NCC). To determine the age of the iron deposits, and provide insight into the crustal growth of the craton, laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS)U-Pb and in situ Hf isotope analysis were performed on detrital zircon grains. Samples were taken from the roof sand-shale of the sedimentary iron deposits at Jiangjiazhai and Pangjiapbu. Overall, 186 detrital zircon grain U-Pb ages yield three major age populations, with weighted average ages of 2450 Ma, 1848 Ma, and 1765 Ma, respectively. Four younger ages from magmatic zircon grains were obtained, ranging from 1694 to 1657 Ma. Combined with observations from published studies, the results define the lower limit for the age of the Chuanlinggou Formation, and constrain the age of the sedimentary iron deposits (marine oolitic ironstone) close to 1650 Ma. The peak ages of 1848 Ma and 2450 Ma define the major collisional events of the NCC. The age of 1765 Ma can be linked to the age range of the widespread mafic dyke swarms that represent the rifting of the NCC within the Columbia supercontinent. Detrital zircon grains from the Chuanlinggou Formation form two obvious groups, with different εHf (t) values ranging from −1 to −8 and from +1 to +8, which correspond to the U-Pb age ranges of 1.7⁻1.9 Ga and 2.3⁻2.6 Ga, respectively. They have a similar two-stage Hf model age peak at 2.65⁻2.85 Ga, suggesting that the source rocks for each of these events were derived from the recycling of ancient crust. The source rocks of the older group of zircon grains might be derived from juvenile crust with a short reworking period. The critical crust⁻mantle differentiation event might happen during the period of 2.65⁻2.85 Ga, marking the most significant stage of the crustal growth in the NCC.

【 授权许可】

Unknown