| 早寒武纪小壳化石的地球化学研究 |
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| 关键词:Anabarites paleo-temperature oxygen isotope silicon isotope |
| 基金项目:自然科学基金项目（基金号：40172041，40221301，40232020）资助。 |
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| A Geochemical Study of Anabarites Fossils from Lower Cambrian Strata in Yangtze Platform of South China and Their Palaeoceangraphic Implications |
| Anabarites fossils belong to Small Shelly Fossils (SSF) and occur widely in Lower Cambrian strata of Yangtze Platform, South China. They are phosphate shells in composition and represent the earliest stages of the Cambrian bioradiation of Bilateria, the so-called“Cambrian Explosion”. In this study,the authors attempted to separate Anabarites fossils from the Lower Cambrian dolostones by 1 N H3PO4 and obtain both the SSF and granular phosphates (GP). Geochemical analyses were performed on samples of SSF, GP,and matrix dolostone (DH-23). The results show that the oxygen isotope compositions of phosphate of SSF and GP are identical within the error (δ18Ophos=16.8±0.2 per mil). The calculated temperatures for paleo-seawater based on the data and equation of Longinelli and Nuti (1973) are 28.4～29.4℃.30Si values of quartz in SSF show negative values of -0.6 per mil, which are consistent with the data of siliceous rocks and cherts of submarine hydrothemal origin, probably indicating the existence of late hydrothermal replacement in the SSF-bearing sedimentary rocks. In addition, trace elements data are also obtained. Mn/Sr rations increase in order of SSF-2＜GP＜SSF-1＜DH-23,in which SSF-2 represents the phosphate parts of SSF and SSF-1 is the carbonate parts of SSF. These data also suggest that the phosphate parts in SSF have received the least change or no change in diagenesis, and therefore can reliably record the paleo-seawater environments durting the important interval. |
| CHEN Yongquan,JIANG Shaoyong,LING Hongfei,YANG Jinghong.2005.A Geochemical Study of Anabarites Fossils from Lower Cambrian Strata in Yangtze Platform of South China and Their Palaeoceangraphic Implications[J].Acta Geoscientica Sinica,26(z1):195-196. |
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