现代地质Issue(2)：243-255,13.
华北克拉通北部14亿年前古风化壳的地球化学特征及古气候意义
Geochemistry and Implication to Paleoclimate of the~1.4 Ga Ancient Weathering Crust in the North of the North China Craton
摘要
Abstract
Recently,a well-preserved carbonate-derived Mesoproterozoic ancient weathering crust is identified at the boundary (~1 400 Ma)between the Tieling Formation and the Xiamaling Formation at the Zishikou sec-tion,Laishui County,Hebei Province.Based on the field observation and analyses of petrology and minera-logy,it can be referred that this ancient weathering crust is mainly composed of limonite-bearing ferric mudstone and illite claystone.Compared with element contents of the Upper Continental Crust,Al2 O3 ,TiO2 ,Fe2 O3 , K2 O in the ancient weathering crust have obvious and different enrichments,SiO2 is leached slightly and CaO, MgO,Na2 O are leached seriously,trace elements,including Sc,Cu,Ga,Zr,Hf,Nb,Ta,In,Th,Li,V, Zn,Rb,Cs,W,Pb,U,Mo,Bi,are unchanged or moderately enriched,but Cr,Sr,Cd are leached,REE are enriched and fractionated.Ce shows positive anomaly and Eu shows negative anomaly.All leaching and en-richment features,including that of U/Th,Fe3+/Fe2+,abnormality of Ce,variations of CIA and BA indexes, indicate that this ancient weathering crust should be formed under the oxidizing,moderate to strong degree of weathering conditions.Consequently,all analyses suggest that the north part of the North China Craton should be a warm and humid tropical to subtropical climate environment at the transitional time between the Calymmian Period (1 600~1400 Ma)and the Ectasian Period (1 400~1 200 Ma)of the Mesoproterozoic Era.关键词
古风化壳/古气候/中元古代/华北克拉通Key words
ancient weathering crust/paleoclimate/Mesoproterozoic Era/North China Craton分类
天文与地球科学引用本文复制引用
郭文琳,苏文博..华北克拉通北部14亿年前古风化壳的地球化学特征及古气候意义[J].现代地质,2014,(2):243-255,13.基金项目
国家自然科学基金项目（40772076，41272046）。 （）
