浙江新昌硅化木的硅质来源  

THE SOURCE OF SILICON OF XINCHANG PETRIFIED WOODS

作　　者：竺国强[1] 董传万[1] 银薇[1] 

机构地区：[1]浙江大学地球科学系,杭州310027

出　　处：《成都理工大学学报（自然科学版）》2003年第1期35-39,共5页Journal of Chengdu University of Technology: Science & Technology Edition

摘　　要：在浙江新昌早白垩世盆地西侧馆头组地层中存在丰富的硅化木。该地硅化木保留清晰的植物结构 ,均由显微结晶质石英组成。从岩石学角度 ,它们属木化石硅质岩。硅化木的硅氧同位素组成δ3 0 Si值为 - 0 .4‰～ - 1 .3‰ ,δ1 8O值为 1 8.1‰～ 2 3 .1‰。根据硅化木的硅、氧同位素组成及周围岩石的岩石化学成分 ,作者讨论了硅化木的硅质来源和成因 ,认为它们具有热水硅质岩的特点 ,系河湖水和海水向下渗透 ,并在一定深度内发生循环然后上涌 ,火山活动为热水提供热源 ,二氧化硅来源于热水流经的地层和岩石 ,富含二氧化硅的热水交代古树木形成硅化木。根据氧同位素地质温度计 ,计算出硅化木形成时的热水温度为 70 .8～ 1 0 8.A lot of petrified woods have been preserved in Xinchang basin, Zhejiang Province. The strata bearing petrified woods are Guantou Formation belonging to the Early Cretaceous in age. The petrified woods preserve obvious plant textures and consist of microcrystalline quartz. They are fossil wood silicolites in petrography. This paper focuses on silicon and oxygen isotopic compositions of the fossil wood silicalites. The δ 30 Si values vary from 18.1‰ to 23.1‰, the δ 18 O values are -0.4‰^-1.3‰. Based on these isotopic data and the chemical compositions of surrounding rocks, the authors discuss the source of silicon and origin of the Xinchang fossil wood silicalites. They have the characteristics of hydrothermal silicalite . The surface water and the sea water penetrated downward and were heated by volcanic activity in a certain depth and extracted out SiO 2 and other elements from the surrounding rocks through which they flowed. The hydrothermal fluid rich in SiO 2 flowed up and replaced the palaeo trees which formed petrified woods. According to the δ 18 O values of the fossil wood silicalites and the oxygen isotopic geologic thermometer , 1000 ln α=3.09×10 6t -2 -3.29, the formation temperatures of the petrified woods were 70.8℃ ~ 108.4℃.

关 键 词：浙江 硅质来源 硅化木 硅氧同位素地球化学 新昌盆地 早白垩 木化石硅质岩 

分 类 号：Q914.21[天文地球—古生物学与地层学]