New Constraints on Ages of the Chuanlinggou and Tuanshanzi Formations of the Changcheng System in the Yan-Liao Area in the Northern North China Craton
详细信息
- 责任者：Zhang Shuanhong (Key Laboratory of Paleomagnetism and Tectonic Reconstruction ; MLR ; Institute of Geomechanics ; Chinese Academy of Geological Sciences ; Beijing 100081 ; China) ; Zhao Yue
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：沉积作用 ; sedimentation ; 团山子组 ; Tuanshanzi Formation ; 串岭沟组 ; Chuanlinggou Formation ; 华北地区 ; North China
- 页码：p.2481-2490
- 图表：6 illus., 2 tables, 37 refs.
- 分类号：1200
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Yan-Liao aulacogen ( rifting) is the best exposed area of the Mesoproterozoic strata in the northern North China Craton ( NCC) and the standard stratigraphic section of the Changcheng System. Recent results show that the lower boundary of the Changcheng System is much younger than 1. 8Ga as previously regarded. Our new zircon LA-ICP-MS U-Pb dating on a potassium-rich volcanic rock in the upper part of the Tuanshanzi Formation in Pinggu area yields a weighted mean 207 Pb / 206 Pb age of 1637 ± 15Ma ( 95% confidence,N =15,MSWD =0. 75) and a concordia age of 1641 ±4Ma ( 1σ,N =14,MSWD =0. 12) ,which represent the sedimentary age of the upper part of the Tuanshanzi Formation. Zircons from a dioritic porphyrite dyke emplaced into the Chuanlinggou Formation in Jixian area yield a weighted mean 207 Pb / 206 Pb age of 1634 ± 9Ma ( 95% confidence,N = 17,MSWD = 0. 40) ,indicating sedimentation of the Chuanlinggou formation prior to 1634 ± 9Ma. Our new results also indicate that eruption of the potassium-rich volcanic rocks in the Yan-Liao aulacogen ( rifting) initiated from 1637 ± 15Ma,and peaked at ca. 1625Ma during the Dahongyu Period as suggested by previous studies in the Dahongyu volcanic rocks.