Age of the Tiaojishan Formation volcanics in the Chengde Basin,northern Hebei province
2006; Science Press; Linguagem: Inglês
ISSN
2095-8927
Autores Tópico(s)Geochemistry and Geologic Mapping
ResumoGeochronological data of the Tiaojishan (Lanqi) period volcanics of representative Yanshan period of large-scale volcanic eruption were rapidly obtained in recent years.On the basis of the early dating results of Tiaojishan (Lanqi) period volcanics in the Yanshan area and our new zircon LA-ICP-MS U-Pb dating results of the volcanics from the top and the bottom Tiaojishan Formation from Xinglong mountain area,Chengde basin,further restrictions were obtained on the initial and the terminative of Tiaojishan period in this area.Dating results show that the age of crystal tuff in top of Tiaojishan Formation is about 153±1Ma(2o-),and the age of trachyandesite in bottom is 156±3Ma(2σ) in Chengde basin.The ages of these two kinds of rock are quite closely in error range, indicating rapid erupting of volcanics of Tiaojishan Formation.Comparison of isotopic dating results of the volcanics of the Tiaojishan (Lanqi) Formation in Yanshan area indicate its bottom age and top age is 158 1Ma and 1531Ma,respectively. Therefore,the volcanics of Tiaojishan (Lanqi) Formation formed in late Jurassic.The boundary age of Tuchengzi (Houcheng) Formation and the volcanics of Tiaojishan (Lanqi) Formation can be restricted to 1531Ma,This is the first obtained boundary age of Mesozoic continental facies stratum in China.The upper(top) timing of Tuchengzi (Houcheng) Formation can be restricted within 134±2Ma～136±2Ma, and its deposit age was from late Jurassic to early Cretaceous.Furthermore,the age of Jiulongshan Formation below the volcanics of Tiaojishan Formation is likely late Jurassic.The bottom age of Zhangjiakou Formation can be restricted to 1342Ma in the Yanshan area.
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