Strontium Isotope Composition and Its Characteristics Analysis of Cambrian-Ordovician Carbonate in Tazhong District, Tarim Basin
-
摘要: 使用VG354固体同位素质谱仪对中1、中4井的25个碳酸盐岩样品做了Sr同位素测试, 并利用电感耦合等离子质谱仪(ICP-MS) 对塔中地区4口井共109个碳酸盐岩样品测试了Sr、Mn元素的含量.通过对Sr、Mn元素含量分析, 及中1、中4井碳酸盐岩的Sr同位素组成分析, 对比全球奥陶系海相碳酸盐的Sr同位素分析结果及演化趋势, 得出了如下认识: (1) 塔中地区奥陶纪87Sr/86Sr比值与全球海水Sr同位素演化趋势基本一致, 具有随时间下降的总体趋势, 这与广阔陆表海和有关的沉积物对放射性成因锶的封存作用有关, 说明海平面变化和白云岩化作用仍然是该区海相碳酸盐岩锶同位素组成与演化的主要控制因素; (2) 塔中地区早奥陶世的87Sr/86Sr比值与全球海水Sr同位素比值相当, 说明该区早奥陶世碳酸盐岩成岩环境为正常海水, 且早奥陶世87Sr/86Sr比值有单调降低的规律, 说明与海平面变化有关; (3) 塔中地区晚奥陶世87Sr/86Sr比值比全球海水高, 其原因是白云岩化作用和晚奥陶世盆地抬升近地表水带来高87Sr/86Sr比值, 且晚奥陶世87Sr/86Sr比值为整体升高的趋势; (4) 塔中地区奥陶纪碳酸盐岩中Mn元素含量变化不大, 反映了塔中地区奥陶纪成岩环境主要为浅水相, 但也有深水相, 白云岩化对其影响不大; (5) 塔中地区奥陶纪碳酸盐岩中Sr元素含量变化较大, 反映该时期该区碳酸盐岩成岩流体主要为海水, 但也有混合水, 白云岩主要为Ⅲ类白云岩和Ⅰ类白云岩.Abstract: In this paper, ICP-MS analytic technology is employed to test the strontium and manganese contents of 109 samples collected from four wells in Tazhong area, Tarim basin. In addition, strontium isotope composition tests have also been conducted, with VG354 solid isotope mass spectrograph, on 25 samples from Zhong 1 and Zhong 4 wells. The analysis of strontium and manganese contents, the research into the characteristics of strontium isotope composition from Zhong 1 and Zhong 4 wells, the comparison between the results from strontium analysis of the global Ordovician marine carbonate and its evolution trend, and the combination of sedimentary facies characteristics of isolated wells in this area conclude the following five points: (1) The marine carbonate strontium isotope curve in the Tazhong area of Tarim basin is consistent with the global evolution trend generally descending with time, the direct reason of which is the evolution of paleogeographic environment. The Ordovician paleogeographic environment ranged from the restricted platform to the open platform and then to the shallow marine shelf in Tazhong area, Tarim basin. Dolomitization is another secondary reason, and the inversion of fluid with high manganese can lead to heavy strontium; (2) The 87Sr/86Sr ratios of the Upper Ordovician in Tazhong area characterized by an apparent mono-decline trend that goes with the time, similar to the global strontium isotope ratio, implies the starting point of the variation of the Upper Ordovician sea level, the overall trend of which is rising; (3) Compared with the global seawater strontium ratios, the 87Sr/86Sr ratio of the Lower Ordovician is much higher, and the 87Sr/86Sr ratio of the Lower Ordovician is often increasing, with its maximum value determined at 0.709 727. The dolomitization, the evaporation of the supratide, and the reflux of high manganese haline, closely associated with such an increasing ratio, can lead to the increase in the content of the strontium and the rise in the 87Sr/86Sr ratio; (4) The manganese content varies little, and is affected little by dolomitization; (5) Large variations occur in the strontium values of Ordovician carbonate in the Tazhong district. Apart from paleogeographic environment and petrography, other factors that can affect the values of strontium are the content of the terrestrial clastics and the diagenisis modification which may result in the further change in the strontium values.
-
Key words:
- Tarim basin /
- carbonate rock /
- strontium composition /
- strontium isotope
-
图 1 研究区以及采样井点位置示意图
1.含油气区域; 2.断层; 3.油气井; 4.研究区域; 5.干井
Fig. 1. Study area and places of sampling wells
图 4 奥陶纪海水Sr同位素演化曲线
曲线据McArthur et al. (2001)拟合曲线中心部分的数据做出, 上、中、下奥陶统的界线按Remane et al. (2001)的国际地层表的年龄值
Fig. 4. Diagram of Sr isotope evolution in Ordovician seawater
图 5 塔中地区寒武-奥陶系87Sr/86Sr比值(a) 与海平面变化曲线(b)
Fig. 5. 87Sr/86Sr ratio (a) and sea level variation curves (b) of Cambrian and Ordovician in Tazhong area
表 1 塔中地区碳酸盐岩Mn、Sr同位素平均值
Table 1. Average values of Mn and Sr isotopes in carbonate rocks of Tazhong area
表 2 塔里木盆地塔中地区中1井奥陶系碳酸盐岩87Sr/86Sr比值
Table 2. 87Sr/86Sr ratio of Ordovician carbonate rocks of Zhong-1 in Tazhong area, Tarim basin
表 3 塔里木盆地塔中地区中4井寒武-奥陶系碳酸盐岩87Sr/86Sr比值
Table 3. 87Sr/86Sr ratio of Cambrian and Ordovician carbonate rocks of Zhong-4 in Tazhong area
-
[1] Bao, Z. D., Zhu, J. Q., Jiang, M. S., et al., 1998. Isotope and trace element evolution: Responding to sea-level fluctuation—An example of Ordovician in middle Tarim basin. Acta Sedi mentologica Sinica, 16 (4): 32-36 (in Chinese with English abstract). [2] Denison, R. E., Koepnick, R. B., Burke, W. H., et al., 1998. Construction of the Cambrian and Ordovician seawater 87Sr/86Sr curve. Chem. Geol., 152: 325-340. doi: 10.1016/S0009-2541(98)00119-3 [3] Depaolo, D. J., Ingrain, B. L., 1985. High-resolution stratigraphy with strontium isotope. Science, 227: 938-941. doi: 10.1126/science.227.4689.938 [4] Hu, M. Y., 1994. Geochemical characters and environmental significance of Ordovician carbonate rocks in Keping area, Tarim basin. Oil & Gas Geology, 15 (2): 158-163 (in Chinese with English abstract). [5] Huang, S. J., Liu, S. G., Li, G. R., et al., 2004. Strontium isotope composition of marine carbonate and the influence of diagenetic fluid on it in Ordovician. Journal of Chengdu University of Technology (Science & Technology Edition), 31 (1): 1-7 (in Chinese with English abstract). [6] Jiang, M. S., Zhu, J. Q., Chen, D. Z., et al., 2002. Carbon and strontium isotope characteristic and response with sea level variation of Ordovician carbonate rocksin Tarim basin. Science in China (Series D), 32 (1): 36-42 (in Chinese). [7] Leggett, J. M., Mckerrow, W. S., Cock, L. R. M., et al., 1981. Periodicity in the Early Palaeozoic marine realm. Journal of the Geological Society, 138: 167-176. doi: 10.1144/gsjgs.138.2.0167 [8] Li, S. Y., Jin, F. Q., Wang, D. X., 1995. Geochemical characteristics of carbonate rock diagenesis. Experimental Petroleum Geology, 17 (1): 55-61 (in Chinese with English abstract). [9] McArthur, J. M., Burnett, J., Hancock, J. M., 1992. Strontium isotopes at K/T boundary: Discussion. Nature, 355 (6355): 28. doi: 10.1038/355028a0 [10] McArthur, J. M., Howarth, R. J., Bailey, T. R., 2001. Strontium isotope stratigraphy: Lowess version 3, best fit to the marine Sr-isotope curve for 0-509Ma and accompanying look-up table for deriving numerical age. J. Geol., 109: 155-170. doi: 10.1086/319243 [11] Montanez, I. P., Banner, J. L., Olseger, D. A., et al., 1996. Integrated Sr isotope variation and sea-level history of Middle to Upper Cambrian platform carbonates: Implications for the evolution of Cambrian sea-water87Sr/86Sr. Geology, 24 (10): 917-920. doi: 10.1130/0091-7613(1996)024<0917:ISIVAS>2.3.CO;2 [12] Qing, H., Barnes, C. R., Buhl, D., et al., 1998. The strontium isotopic composition of Ordovician and Silurian brachiopods and conodonts: Relationships to geologicalevents and implications for coeval seawater. Geochi micaet Cosmochi mica Acta, 62 (10): 1721-1733. doi: 10.1016/S0016-7037(98)00104-5 [13] Remane, J., Faure-Muret, A., Odin, G. S., 2001. International stratigraphic chart. Journal of Stratigraphy, 24 (Suppl. ): 321-340. [14] Richter, F. M., Rowley, D. B., DePaolo, D. J., 1992. Sr isotope evolution of seawater: The role of tectonics. Earth and Planetary Science Letters, 109: 11-23. doi: 10.1016/0012-821X(92)90070-C [15] Ruppel, S. C., James, E. W., Barrick, J. E., et al., 1996. High-resolution 87Sr/86Sr chemostratigraphy of the Silurian: Implications for event correlation and strontiumflux. Geology, 24 (9): 831-834. doi: 10.1130/0091-7613(1996)024<0831:HRSSCO>2.3.CO;2 [16] Sun, Z. G., Liu, B. Z., Liu, J., 1996. Strontium isotope's characteristic and paleoenvironmental meaning in the coral reef of Westsand. Chinese Science Bulletin, 43 (5): 434-437 (in Chinese). [17] Qin, J. X., Zeng, Y. F., 1994. Geochemistry of Lower Ordovician dolostones in eastern Ordos basin. Acta Mineralogica Sinica, 14 (1): 22-31 (in Chinese withEnglish abstract). [18] Wickman, F. E., 1948. Isotope ratios: A clue to the age of certain marine sediments. J. Geol., 56: 61-66. doi: 10.1086/625478 [19] 鲍志东, 朱井泉, 江茂生, 等, 1998. 海平面升降中的元素地球化学响应——以塔中地区奥陶纪为例. 沉积学报, 16 (4): 32-36. https://www.cnki.com.cn/Article/CJFDTOTAL-CJXB804.005.htm [20] 胡明毅, 1994. 塔北柯坪奥陶系碳酸盐岩地球化学特征及环境意义. 石油天然气地质, 15 (2): 158-163. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT402.007.htm [21] 黄思静, 刘树根, 李国蓉, 等, 2004. 奥陶系海相碳酸盐锶同位素组成及受成岩流体的影响. 成都理工大学学报(自然科学版), 31 (1): 1-7. doi: 10.3969/j.issn.1671-9727.2004.01.001 [22] 江茂生, 朱井泉, 陈代钊, 等, 2002. 塔里木盆地奥陶纪碳酸盐岩的碳、锶同位素特征及其对海平面变化的响应. 中国科学(D辑), 32 (1): 36-42. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK200201004.htm [23] 李双应, 金福全, 王道轩, 1995. 碳酸盐岩成岩作用的微量元素地球化学特征. 石油实验地质, 17 (1): 55-61. https://www.cnki.com.cn/Article/CJFDTOTAL-SYSD501.007.htm [24] 孙志国, 刘宝柱, 刘健, 1996. 西沙珊瑚礁锶同位素特征及其古环境意义. 科学通报, 43 (5): 434-437. doi: 10.3321/j.issn:0023-074X.1996.05.014 [25] 覃建雄, 曾允孚, 1994. 鄂尔多斯盆地东部下奥陶统白云岩地球化学研究. 矿物学报, 14 (1): 22-31. doi: 10.3321/j.issn:1000-4734.1994.01.004 -
下载:
点击查看大图
图(5) / 表(3)
计量
- 文章访问数: 3853
- HTML全文浏览量: 159
- PDF下载量: 5
- 被引次数: 0
