浙江新昌早白垩世盆地中硅质岩石的地球化学特征与成因  

Geochemical characteristics and origin of silicolites in the Early Cretaceous Basin in Xinchang, Zhejiang Province.

作　　者：董传万[1] 竺国强[1] 银薇[1] 

机构地区：[1]浙江大学地球科学系,浙江杭州310027

出　　处：《浙江大学学报（理学版）》2003年第2期230-235,共6页Journal of Zhejiang University（Science Edition）

基　　金：浙江省教育厅基金资助项目 (2 0 0 2 0 2 5 8)

摘　　要：在浙江新昌早白垩世盆地西侧的馆头组中 ,存在一些硅质岩石——块状硅质岩、含叠层石硅质岩和木化石硅质岩等 .它们以高 Si O2 、富 Fe2 O3、低 Al2 O3和 Ti O2 为特征 ,REE含量低 ,而且有弱的 Ce亏损 ,δ30 Si值为 - 0 .4‰～ - 1.5‰ ,δ1 8O值为 18.1‰～ 2 3 .1‰ .硅质岩的地球化学研究表明它们具有热水硅质岩的特点 .结合其它地质资料 ,作者讨论了这些硅质岩的硅质来源和成因 ,认为它们系地表水和海水向下渗透 ,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 ,Si O2 来源于热水流经的地层和岩石 .富含 Si O2 的热水溶液在适当的地方沉淀形成块状或透镜状硅质岩 ,也可解释古树木和含叠层石灰岩形成木化石硅质岩和含叠层石硅质岩 .根据氧同位素地质温度计计算出硅质岩形成时的热水温度为 70 .8～ 10 8.There are silicolites in the Guantou formation of the Early Cretaceous basin in Xinchang County, Zhejiang Province. The rock types include massive or lenticular silicolite, stromatolite bearing silicolite and fossil wood silicolite. They are characterized by a higher content of SiO 2 and Fe 2O 3, low content of Al 2O 3 and TiO 2, and small amount of REE with slight Ce depletion. The δ 30 Si values of the silicolites vary from -0.4‰ to -1.5‰, the δ 18 O values are in 18.1‰ to 23.1‰. The silicolites can be identified as hydrothermal sediments based on their geochemical features. The source of silicon and origin of the silicolites were discussed: The water come from the surface and sea penetrates downward and is heated by volcanic activity in a certain depth and extracts SiO 2 and other elements out from the surrounding rocks through which it passes. The SiO 2 rich hydrothermal fluid up flows and deposits, forming massive and lenticular silicolites. The fluid also expounds the palaeo trees and stromatolite bearing limestone to form fossil wood silicolite (petrified wood) and stromatolite bearing silicolite. According to the δ 18 O values of the silicolites calculated from the oxygen isotopic geologic thermometer, their forming temperatures ranges from 70.8℃ to 108.4℃.

关 键 词：浙江 硅质岩 地球化学 早白垩世 新昌盆地 热水沉积 岩石成因 化学成分 

分 类 号：P588.2[天文地球—岩石学] P595[天文地球—地质学]