| 蓟县中上元古界典型剖面锶同位素组成特征及其地层意义 |
| |
| 关键词:Jixian section Sr-isotope |
| 基金项目: |
|
| 摘要点击次数: 4069 |
| 全文下载次数: 4808 |
| 摘要: |
| Strontium isotope compositions of jixian middle-upper proterozoic stratatype section and their significances |
| This paper briefly introduced a study method for strontium isotope stratigraphy.Also presented are the strontium isotope data on samples collected from boundaries between different formations or systems inside Jixian middle-upper Pronterozoic strataype section.Our results indicate that carbonate strata of Gaoyuzhuang,Wumishan and Tieling formation in Jixian system and Jingeryu formation in Qingbaikou system are ideal targets for studying 87Sr/86Sr-time evolution curve.If theinfluence of continental material mixing is negligible,the younger the strata ,the slightly higher the 87Sr/86Sr ratio values.For example,average 87Sr/86Sr ratio value is 0.7071 for Gaoyuzhuang formation (1600-1400±50Ma),0.7073-0.7089 for Wunishan and Tieling formations(1400-1000±50Ma),0.7086-0.7094 for Jingeryu for mation and Cambrian Fujunshan formation(800-600±50Ma),representing the original oceanic strontium isotope compositions of those periods,while Chuanlinggou,Tuanshanzi and Dahongyu formations in Great Wall system and Yangzhuang and Hongshuizhuang formations in Jixian system show exceptionally high 87Sr/86Sr isotope ratio values. One of interpretations for these anomalies is continental material addition.Most of samples collected from these strata contain more or less argillaceous components and fine sands.Consequently,their 87Sr/86Sr ratio values reflect gross compositions of mixtures of both oceanic and continentla natures. In another word,these values should not be considered as strontum isotope compositions of original oceanic water,but they may have some bearings on paleotectonic setting and deposition environments. By studying the 87Sr/86Sr-time evolution curve of Jixian middle-upper Proterozoic stratatype section,we conciuded that variations of strontium isotope compositions of carbonate stata(unmetamorphosed)may be used not only in classification and correlation of strata in different regions,but also in discussing internal relations between deposition environment and ocean-continent changes,providing a useful tool for researches on geological events and an efficient evidence for classification and correlation of global Proterozoic strata. |
| LI Hua-qin,CAI Hong,TAI Zheng-yong,LIU Bo.1994.Strontium isotope compositions of jixian middle-upper proterozoic stratatype section and their significances[J].Acta Geoscientica Sinica,15(1,2):232-244. |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|