Variational Characteristics of Sm/Nd Ratio in Cambrian-Triassic Paleoseawater from Three Gorges Area Conodont Evidence
-
摘要: 牙形石作为划分地层的标准化石, 具有确切的地层层位和较高的REE含量, 并不容易受成岩作用的影响, 因此作为研究古海水演化的指示剂引起人们的广泛关注.利用同位素稀释法对扬子克拉通三峡地区寒武纪—三叠纪海相碳酸盐岩中代表古海水化学组成牙形石的Sm/Nd比值进行测定, Sm/Nd比值在0.108-0.348之间, 有较大的变化范围.建立Sm/Nd比值随时间的演化曲线, 并结合已有沉积地层学和沉积地球化学的成果进行研究, 结果表明, 古海水Sm/Nd比值变化与海平面升降、古陆块的隆起有明显对应关系, 同时, 区域性构造运动, 如海底地壳拉张产生的幔源组分和地幔柱活动也会影响古海水的Sm/Nd比值.因此, 古海水的Sm/Nd比值对海平面的升降、古大陆的风化作用和区域构造事件有指示意义.Abstract: Conodonts have received extensive attention in terms of their potential as geochemical tracers, due to their precise stratigraphic age and high REE concentration as well as their relative resistance to diagenetic alternation. The ratios of Sm/Nd of paleoseawater from the Cambrian to the Triassic in the northern of the Yangtze craton were determined using the Isotope Dilution Mass Spectrometry method. The samples exhibit a large variation in Sm/Nd ratio (0. 108-0. 348). It shows that the temporal variability in Sm/Nd ratios of the seawater from the Cambrian to the Triassic is characterized by strongly correlated eustatic changes of sea level and submergence history of old continental in the Three Gorges area, corresponding to the previously published sedimentological and geochemical studies on these areas. In the other hand, the preliminary conclusion revealed that the submarine hydrothermal system (mantle flux) and the Emeishan mantle plume with higher Sm/Nd ratios, which were existing in the subarea adjacent to the Three Gorges area during the Phanerozoic, may likely influence the Sm/Nd values of contemporaneous seawater. It allows us to speculate that the Srn/Nd curve of paleoseawater constructed by using conodonts has a potentially wide range of applications in studies relating to the paleoenvironmental and regional tectonic event.
-
Key words:
- Sm/Nd ratio /
- conodont /
- paleoenvironment /
- Yangtze craton.
-
图 1 三峡地区地质略图(汪啸风等(1987))
1.黄陵花岗岩崆岭群片麻岩；2.震旦纪；3.取样位置
Fig. 1. Schematic geologic map of the Three Gorges area
图 2 三峡地区显生宙牙形石Sm/Nd比值随时间演化
Fig. 2. Sm/Nd ratio distribution of conodonts in response to the age changes during the Phaneroaoie in the Three Gorges area
表 1 三峡地区寒武纪一三叠纪不同时期牙形石Sm/Nd比值
Table 1. Sm/Nd ratios of conodont from Cambrian to Triassic in the Three Gorges area
-
Bertram, C.J., Elderfieid, H.J., Aldrldge, R.J. et al., 1992. 87Sr/86Sr, 143Nd/144Nd and REEs in Silurian pbosphatic fossils. Earth Planet. Sci. Lett., 113: 239-249. doi: 10.1016/0012-821X(92)90222-H Chen, X., Xu, J.T., Cheng, H.J., et al., 1990. On the Hannan old land and Dabashan uplift. Journal of Stratigraphy, 14(2): 81-116(in Chinese with English abstract). Chen, X. L., Wang, X. E., 1999. Multiple stratigraphic subdivi sion and sea level changes of the Early Paleomic in Yangtze gorges area. Geology and Mineral Resources of South China, 3: 1-11(in Chinese with English abstract). Elderfield, H., Greaves, M. J., 1982. The Fare earth elements in seawater, Nature. 296: 214-219. doi: 10.1038/296214a0 Fanton, K.C., Hohnden, C., Nowlan, G. S, et al., 2002. 143Nd/144Nd and Sm/Nd stratigraphy of Upper Ordovician epeiric sea carbonates. Geochimica et Cosmxchirnica Acta, 66(2): 24l-255. Gao, S., Lin, W.L., Qiu, Y., et al., 1999. Contrasting geochemical and Sm-Nd isotopic compositions of Archean metasediments from the Kongling high grade terrain of the Yangtze craton: Evidence for cratonic evolution and redistribution of REE during crustal anatexis. Geochim. Cosmochim. Aeta, 63(13/14): 2071-2088. Grandjean-Leécuyer, P., Feist, R., Albaréde, F., 1993. Rare earth elements in old biogenic apatites. Geochim. Coawlo chimi. Aeta, 57: 2507-2514. doi: 10.1016/0016-7037(93)90413-Q Haq, R. U., Vail, P. R., 1987. The chronology of fluctuating sea 1evel since the Triasslc. Science, 235(1): 156-1167. Hohnden, C., Creaser, R. A., Muehlenbacbs, K., et al., 1996. Isotopic and elemental systematics of Sr and Nd irl 454Ma biogcnic apatites: hnplications for paleoseawater studies. Earth Planet. Sci. Lett. , 142: 425 437. doi: 10.1016/0012-821X(96)00119-7 Huang, S. J., 1997. Carbon and strontium isotopes of Late Paleomic marine carbonates in the upper Yangtze plat form, S0uthwest China. Acta Geologica Sinica, 71(1): 45-53(in Chinese with English abstract) Huang, S. J., Shi, H., Zhang, M., et al., 2001. Strontium isotope evolution and global sea level changes of Carbon Kerous and Permian marine carbonate, upper Yah gtze platfom. Acta Sedimentologica Sinica, 19(4): 481 -487(in Chinese with English abstract). Huang, Z.X., Li, Z. H., Chen, L.D., et al., 1999. Early Middle Triassic sequence stratigraphy in Wushan area. Chongqing. Geology and Mineral Resources of South China, 4: 50-56(in Chinese with English abstract). Lai, X.L., Zhou, H. W., Qi, S. H., 1995. Study of low very low grade metamorphism of carbonate by conodont col our alternation index(CAI). Geological Science and Technology Information, 14(2): 23-30(in Chinese with English abstract). Imeuyer, C., Reynard, B., Grandjean, P., 2004. Rare earth element evolution of Phanerozoic seawater recorded in blogenie apatites. Chemical Geology, 204: 63-102. doi: 10.1016/j.chemgeo.2003.11.003 Martin, E. E., Haley, B. A., 2000. Fossil fish teeth as proxies for seawater Sr and Nd isotopes. Geochirm. Cosmochim Acta, 64: 835-847. doi: 10.1016/S0016-7037(99)00376-2 Niu, Z. J., Duan, Q. F., Fu, T.A., et al., 2000. Paleokarst unconformity on the top of the Maokou Formation in the Jianshi-Badong area, Huhei: Its discovery and signiI ieance. Regional Geology of China, 19(3): 276-280 (in Chinese with English abstract). Niu, Z.J., Xu, A. W, Duan, Q F., et al., 2000. Origin and enrichment of selenium in Permian strata in the northern part of Jianshi, Hubei. Regional Ceology of China, 19(4): 396-401(in Chinese with English abstract). Ouyang, J.P., Zhang, R. R., 1996. Geochemistry of sedimentary provenanee in Qinling orogenic belt and its implica tions for tectonic evolution. Earth Science Journal of China University of Geosciences, 21(5): 465-468 (in Chinese with English abstract). Picard, S., Lécuyer, C., Barrat, J.A., et al., 2002. Rare-earth element contents of Jurassic fish and reptile teeth and their potential relation to seawater composition(Anglo Paris basin, France and England), Chemical Geology, 186: 1-16. doi: 10.1016/S0009-2541(01)00424-7 Reynard, B., Leeuyer, C., Grandjean, P., 1999. Crystalehemical controls on rareearth element concennations in fossil biogenic apatites and implications for paleoenvironmental reconstructions. Chemical Geology, 155: 233-241 doi: 10.1016/S0009-2541(98)00169-7 Su, W. B., He, I.O., Wang, Y. B., et al, 2003. K-bentonite beds and high-resolution integrated stratigraphy of the uppermost Ordovician Wufeng and the lowest Silurian Longmaxi formations in South China. Science in China (Series D), 46(11): 1121-1133. Wang, C. S, Li, X. H., Chen, H. D., et al., 1999. Permian sea-level changes and rising-falling events in South China. Acta Sedimentologica Sinica, 17(4): 536 54l(in Chinese with English abstract). Wang, X.F., Ni, S.Z., Zeng, Q. L., et al., 1987. Biostratigraphy of the Yangtze gorge area: (2)Early Palaeozoic era. Geological Publishing House, Bejing, 43-137(1n Chinese with English abstract). Xu, Y G, Chung, S L, 2001. The Emdshan large igneous province: Evidence for mantle plume activity and melting conditions. Geochimica, 30(1): 1-9(in Chinese with English abstract). Xu, Y.G., Chung, S. L., Jahn, B.M., et al., 2001 Petrologic and geochemical constraints on the petrogenesis of Pennian-Triassic Emeishan flood basahs in southwestern China. Lithos. 58: 145-168. doi: 10.1016/S0024-4937(01)00055-X Yang, Z. Y., Wu, S. B., Yin, H. F, et al., 1991. Permo Triassic events of South China. Geological Publishing House, Beijing(in Chinese). Yin, H.F., Peng, Y. Q., 1995. Evolution of the Phanerozoic paleo-ocean of Qinling. Earth Science-Journal of China University of Geosciences, 20(6): 605-611(in Chinese with English abstract). Yin, H. F, Tong, J.N., Ding, M. H., et al., 1994. Late Permian-Middle Triassic sea level changes of Yangtze platform. Earth Science Journal of China University of Geosciences, 19(5): 628-632(in Chinese with English abstract). Yin, H.F., Wu. S. B., Du, V. S., et al., 1999. South China defined as part of Tethyan archipelagic Ocean system. Earth Science Journal of China University Geosciences, 28(1): 1-11(1n Chinese). 陈孝红, 汪啸风, 1999. 长江三峡地区早古生代多重地层划分与海平面升降事件. 华南地质与矿产, 3: 1-11. https://www.cnki.com.cn/Article/CJFDTOTAL-HNKC199903000.htm 陈旭, 徐均涛, 成汉钧, 等, 1990. 论汉南古陆及大巴山隆起. 地层学杂志, 14(2): 81-116. https://www.cnki.com.cn/Article/CJFDTOTAL-DCXZ199002000.htm 黄思静, 1997. 上扬子地区晚古生代海相碳酸盐岩的碳、铭同位素研究. 地质学报, 71(1): 45-53. 黄思静, 石和, 张萌, 等, 2001. 上扬子石炭一二叠纪海相碳酸盐的银同位素演化与全球海平面变化. 沉积学报, 19 (4): 481-487. doi: 10.3969/j.issn.1000-0550.2001.04.001 黄照先, 李志宏, 陈立德, 等, 1999. 重庆市巫山地区早、中三叠世层序地层研究. 华南地质与矿产, 4: 50-56. https://www.cnki.com.cn/Article/CJFDTOTAL-HNKC199904010.htm 赖旭龙, 周汉文, 祁士华, 1995. 论利用牙形石色变度值研究碳酸盐岩低级一极低级变质作用. 地质科技情报, 14(2): 23-30. https://www.cnki.com.cn/Article/CJFDTOTAL-DZKQ502.004.htm 牛志军, 段其发, 傅泰安, 等, 2000. 湖北建始一巴东地区茅口组顶部古岩溶不整合面的发现. 中国区域地质, 19(3): 276-280. doi: 10.3969/j.issn.1671-2552.2000.03.011 牛志军, 徐安武, 段其发, 等, 2000. 湖北建始北部二叠纪地层硒的来源与富集. 中国区域地质, 19(4): 396-401. doi: 10.3969/j.issn.1671-2552.2000.04.010 欧阳建平, 张本仁, 1996. 秦岭造山带沉积物源地球化学研究及其构造意义. 地球科学-中国地质大学学报, 21(5): 465-468. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX605.001.htm 汪啸风, 倪世钊, 曾庆奏, 等, 1987. 长江三峡地区生物地层学早古生代分册(2). 北京: 地质出版社, 43-137. 王成善, 李祥辉, 陈洪德, 等, 1999. 中国南方二叠纪海平面变化及升降事件. 沉积学报, 17(4): 536-541. https://www.cnki.com.cn/Article/CJFDTOTAL-CJXB199904004.htm 徐义刚, 钟孙霖, 2001. 峨眉山火山成岩省: 地慢柱活动的证据及其熔融条件. 地球化学, 30(1): 1-9 https://cdmd.cnki.com.cn/Article/CDMD-10491-1020802481.htm 杨遵仪, 吴顺宝, 殷鸿福, 等, 1991. 华南二叠一三叠纪过渡期地质事件. 北京: 地质出版社. 殷鸿福, 彭元桥, 1995. 秦岭显生宙古海洋演化. 地球科学-中国地质大学学报, 20(6): 605-611. doi: 10.3321/j.issn:1000-2383.1995.06.004 殷鸿福, 童金南, 丁梅华, 等, 1994. 扬子区晚二叠世一中三叠世海平面变化. 地球科学-中国地质大学学报, 19(5): 628-632. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX199405009.htm 殷鸿福, 吴顺宝, 杜远生, 等, 1999. 华南是特提斯多岛洋体系的一部分. 地球科学-中国地质大学学报, 28(1): 1-11. doi: 10.3321/j.issn:1000-2383.1999.01.001 -
下载:
点击查看大图
图(2) / 表(1)
计量
- 文章访问数: 3963
- HTML全文浏览量: 527
- PDF下载量: 13
- 被引次数: 0
