冀北承德盆地髫髻山组火山岩的时代  

Age of the Tiaojishan Formation volcanics in the Chengde Basin,northern Hebei province

作　　者：刘健[1] 赵越[1] 柳小明[2] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]西北大学大陆动力学重点实验室,西安710069

出　　处：《岩石学报》2006年第11期2617-2630,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金重点项目(40132020);国土资源大调查项目(200013000168)资助.

摘　　要：随着近年来的研究进展,代表燕山期大规模火山喷发的髫髻山期(蓝旗期)火山岩的年代学数据得到迅速积累。本文在结合前人对燕山地区髫髻山期(蓝旗期)火山岩 U-Pb 同位素定年工作的基础上,对取自冀北承德盆地兴隆山附近髫髻山组火山岩顶、底样品的锆石进行 U-Pb LA-ICP-MS 定年,试图进一步限定该地区髫髻山期火山岩起始和结束的时代。承德盆地髫髻山组火山岩定年结果表明,其顶部晶屑凝灰岩时代为153±1Ma(2σ),底部粗安岩时代为156±3Ma(2σ)。两者时代在误差范围内一致,说明该地区髫髻山组火山岩喷发是在短时期内完成的。燕山地区髫髻山期(蓝旗期)火山岩时代综合对比分析结果表明髫髻山组(蓝旗组)火山岩初步限定的底部年龄和顶部年龄分别为158±1Ma、153±1Ma。其形成时代在晚侏罗世。土城子组(后城组)与髫髻山组(蓝旗组)火山岩的界线年龄为153±1Ma,这是第一次获得我国中生代陆相地层界线年龄。土城子组顶部的时限确定在134±2～136±2Ma 之间。其沉积时代为晚侏罗世至早白垩世。而髫髻山组火山岩之下的九龙山组的时代可能亦为晚侏罗世。区域张家口组的底部时代限定在134±2Ma。Geochronological 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（2σ）, 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.

关 键 词：承德盆地 髫髻山组(蓝旗组) 土城子组(后城组) 锆石LA—ICP—MS U—Pb定年 

分 类 号：P588.14[天文地球—岩石学] P597.3[天文地球—地质学]