Geochemical Characteristics and Geological Significance of Quaternary Sediments in the Mekong Delta
-
摘要:
湄公河三角洲是由发源于青藏高原的世界第7长河——湄公河于南海西南部入海口处沉积而成.由于缺少可靠的地球化学资料和系统研究，湄公河三角洲地区第四系沉积物源性质尚不明确，制约了对湄公河三角洲源汇系统的进一步认识.本文对湄公河三角洲第四系沉积物进行了重矿物、主量元素和微量元素的地球化学特征分析，结果表明：所有样品稀土元素球粒陨石标准化分布均表现为负Eu异常，为典型的陆源沉积.全新统样品ZTR指数为2~13，更新统样品ZTR指数为21~69；相关图解表明全新统样品主要受分选影响，更新统样品主要受旋回影响.更新统样品最远物源可能为青藏高原东部，经过多次沉积旋回，由古湄公河搬运并再次沉积于湄公河三角洲，而全新统样品成分成熟度较低，为近源沉积，可能为大叻区基岩产物.湄公河三角洲不同时期沉积物源区变化，可能与湄公河和湄公河三角洲在第四系的沉积过程和演化有关.
Abstract:Originating from Qinghai-Tibet Plateau, the Mekong River is seventh longest river of the world, forming the Mekong River Delta in southwestern South China Sea. Due to lack of reliable geochemical data and systematic research, the properties of Quaternary sediments in the Mekong Delta are still unclear, which restricts further understanding of the source and sink system of the Mekong River. Based on the analysis of heavy minerals, geochemical characteristics of major elements and trace elements of samples from Mekong Delta, all the samples present negative chondrite-normalized Eu anomaly, indicating typical terrigenous deposition. With respect to the Pleistocene samples, the ZTR index ranges between 21 and 69. By contrast, the ZTR index of the Holocene samples ranges from 2 to 13. The correlation diagrams show that the Holocene samples are mainly affected by sorting and the Pleistocene samples are mainly affected by sedimentary recycling. The provenance of sediments from the Pleistocene with high component maturity was probably derived from eastern part of the Tibet, which has experienced several depositional recycling and have been transported by Paleo-Mekong River to the Delta. However, with low component maturity, the sediments of the Holocene are proximal source, and most likely from basement of Dalat area nearby. Variation of provenance of Mekong River Delta during different depositional periods may be related to the tectonic activities, depositional processes and evolution of the Mekong River and the Mekong River Delta in Quaternary.
-
Key words:
- provenance /
- geochemistry /
- Quaternary /
- Mekong River Delta
-
图 1 东南亚及研究区地质背景(a)、采样位置(b)（据Liu et al., 2007; Hennig et al., 2018修改）以及A-B地层剖面(c)
图b中粉色虚线为古湄公河，据Hennig et al.（2018）修改；现湄公河三角洲（灰色）和大叻区（绿色）范围合为古湄公河三角洲范围，据Hennig et al.（2018）修改；A-B剖面据内部未发表资料
Fig. 1. Geological map and bathymetry of SE Asia (a); sampling location in the study area (b) (modified after Liu et al., 2007; Hennig et al., 2018), and the profile of A-B shown in figure b (c)
图 2 湄公河三角洲第四系沉积物重矿物组合特征
图中数据单位为%；VDLZ52.1和VDLZ52.1据Hennig et al.（2018）
Fig. 2. Characteristics of heavy mineral assemblages of sediments in Quaternary, Mekong Delta
图 3 湄公河三角洲第四系不同样品主量元素含量百分比对比
Fig. 3. Comparison of content percentage of major elements in different samples in Quaternary, Mekong Delta
图 5 湄公河三角洲第四系稀土元素球粒陨石标准化分布
球粒陨石标准化值据Boynton and Wark（1984）
Fig. 5. REE distribution map normalized to chondrite of samples in Quaternary, Mekong Delta
图 6 碱性金属和碱土金属迁移性对比（Garzanti et al., 2013）
αAlE值根据平均上地壳数据（UCC）标准化，据Hu and Gao（2008）；MR01-MR17据Liu et al.（2007）
Fig. 6. Comparison of migration of alkaline metals and alkaline earth metals (Garzanti et al., 2013)
图 7 湄公河三角洲第四系样品CIA-SiO2/Al2O3相关关系
MR01-MR17数据据Liu et al.（2007）
Fig. 7. The relationship of CIA-SiO2/Al2O3
图 9 湄公河三角洲第四系母岩性质判别图
a.判别函数图，据Roser and Korsch（1988），判别函数因子1=‒1.773TiO2+0.607Al2O3+0.76Fe2O3‒1.5MgO+0.616CaO+0.509Na2O‒1.224K2O‒9.09；判别函数因子2=0.445TiO2+0.07Al2O3‒0.25Fe2O3‒1.142MgO+0.438CaO+0.475Na2O+1.426K2O‒6.861.b.Co/Th-La/Sc图解，据Gu et al.（2002）. c.La/Yb-∑REE母岩性质判别图，其中：A. 沉积岩；B. 大洋拉斑玄武岩；C. 玄武岩区域；D. 大陆拉斑玄武岩；E. 碱性玄武岩；F. 花岗岩；G. 金伯利岩；H. 碳酸盐岩区
Fig. 9. Discrimination map of source rock properties in Quaternary, Mekong Delta
表 1 湄公河三角洲第四系样品主量元素（%）分析结果
Table 1. Analysis of major elements (%) of samples in Quaternary, Mekong Delta
样号 SM01 SM02 SM03 SM04 SM05 SM06 SM07 层位 全新统 全新统 全新统 上更新统 中‒上更新统 下‒中更新统 下‒中更新统 SiO2 83.86 89.32 86.67 89.03 90.37 92.04 94.03 TiO2 0.65 0.23 0.28 0.76 0.43 0.20 0.10 Al2O3 5.70 4.92 6.09 5.85 5.47 4.43 3.16 Fe2O3T 4.35 1.96 2.16 0.83 0.76 0.88 1.11 MnO 0.08 0.03 0.03 0.01 0.00 0.01 0.01 MgO 0.89 0.36 0.50 0.08 0.04 0.09 0.04 CaO 0.42 0.28 0.29 0.05 0.04 0.05 0.04 Na2O 0.61 0.58 0.75 0.06 0.03 0.05 0.03 K2O 1.15 1.53 1.65 0.15 0.03 0.37 0.17 P2O5 0.08 0.05 0.05 0.02 0.02 0.02 0.03 LOI 1.81 1.02 1.33 2.65 2.68 1.60 1.21 SiO2/Al2O3 24.97 30.84 24.17 25.82 28.06 35.30 50.45 K2O/Na2O 1.23 1.74 1.45 1.72 0.66 5.24 3.45 Al2O3/TiO2 6.92 16.81 17.03 6.03 10.03 17.25 24.53 K2O/Al2O3 0.22 0.34 0.29 0.03 0.01 0.09 0.06 CIA 65.35 61.18 63.21 94.42 97.35 88.78 91.45 
下载: 导出CSV
表 2 湄公河三角洲第四系样品微量元素（10-6）分析结果
Table 2. Analysis of rare elements (10-6) of samples in Quaternary, Mekong Delta
样号 SM01 SM02 SM03 SM04 SM05 SM06 SM07 层位 全新统 全新统 全新统 上更新统 中‒上更新统 下‒中更新统 下‒中更新统 Li 20.50 13.60 17.40 7.91 4.88 8.32 7.70 Be 1.20 0.81 1.13 0.21 0.16 0.37 0.39 Sc 6.72 3.22 3.99 4.69 3.16 2.68 2.11 V 49.7 25.6 31.7 27.3 26.6 20.9 19.8 Cr 62.00 20.20 23.40 34.40 34.60 16.60 7.09 Co 13.0 5.44 6.76 0.70 0.39 0.35 0.51 Ni 17.40 9.76 12.70 4.62 5.04 2.34 2.57 Cu 7.48 4.14 5.31 8.19 3.70 3.41 5.29 Zn 49.90 23.20 29.10 9.02 6.07 4.85 5.14 Ga 7.68 5.48 7.08 7.10 6.73 4.63 2.77 Rb 50.50 60.00 67.30 13.50 2.66 18.70 8.99 Sr 65.30 55.20 61.70 15.60 6.25 10.60 6.07 Y 34.00 10.80 11.60 18.40 8.41 6.78 5.02 Zr 1 106.0 117.0 102.0 444.0 377.0 98.2 55.6 Nb 12.80 5.06 5.95 5.47 8.69 4.41 2.37 Sn 1.77 1.03 1.28 1.67 1.33 0.90 0.60 Cs 2.72 2.27 2.89 3.14 1.16 1.40 0.58 Ba 174.0 289.0 297.0 70.7 16.2 59.1 36.6 La 43.00 14.40 15.80 15.50 5.48 10.70 9.99 Ce 87.8 29.7 33.0 28.7 10.0 23.1 17.3 Pr 9.85 3.34 3.63 3.10 1.11 2.26 1.80 Nd 37.30 12.60 14.10 10.70 4.02 8.08 6.11 Sm 6.88 2.38 2.69 1.98 0.73 1.37 1.01 Eu 1.00 0.49 0.52 0.41 0.13 0.21 0.19 Gd 5.92 2.04 2.23 2.08 0.77 1.13 0.87 Tb 0.93 0.33 0.34 0.40 0.16 0.17 0.15 Dy 5.33 1.91 2.02 2.88 1.17 1.13 0.85 Ho 1.03 0.38 0.44 0.61 0.27 0.25 0.18 Er 3.42 1.05 1.15 1.84 0.92 0.64 0.54 Tm 0.490 0.160 0.170 0.300 0.160 0.110 0.084 Yb 3.58 1.10 1.16 2.02 1.13 0.74 0.55 Lu 0.540 0.140 0.170 0.310 0.200 0.110 0.085 Hf 26.90 2.98 2.57 11.20 9.34 2.45 1.45 Ta 0.95 0.45 0.44 0.11 0.65 0.36 0.22 Tl 0.280 0.370 0.410 0.160 0.050 0.130 0.066 Pb 16.00 12.90 14.10 11.90 4.19 7.47 11.60 Th 17.50 5.19 5.74 8.16 6.81 4.96 3.34 U 4.23 1.32 1.37 2.59 1.33 0.89 0.76 ∑REE 577.50 195.79 215.75 215.41 85.71 133.02 108.27 LREE/HREE 3.17 3.30 3.34 2.04 1.49 3.74 3.92 δEu 0.47 0.66 0.64 0.61 0.52 0.49 0.59 （La/Yb）N 8.10 8.84 9.20 5.16 3.26 9.75 12.26
下载: 导出CSV
-
Allègre, C. J., Minster, J. F., 1978. Quantitative Models of Trace Element Behavior in Magmatic Processes. Earth and Planetary Science Letters, 38(1): 1-25. https://doi.org/10.1016/0012-821X(78)90123-1 An, A. R., Choi, S. H., Yu, Y., et al., 2017. Petrogenesis of Late Cenozoic Basaltic Rocks from Southern Vietnam. Lithos, 272-273: 192-204. https://doi.org/10.1016/j.lithos.2016.12.008 Bock, B., Mclennan, S. M., Hanson, G. N., 1998. Geochemistry and Provenance of the Middle Ordovician Austin Glen Member (Normanskill Formation) and the Taconian Orogeny in New England. Sedimentology, 45(4): 635-655. https://doi.org/10.1046/j.1365-3091.1998.00168.x Bodet, F., Schärer, U., 2000. Evolution of the SE-Asian Continent from U-Pb and Hf Isotopes in Single Grains of Zircon and Baddeleyite from Large Rivers. Geochimica et Cosmochimica Acta, 64(12): 2067-2091. https://doi.org/10.1016/S0016-7037(00)00352-5 Boynton, W. V., Wark, D. A., 1984. Trace Element Abundances in Rim Layers of an Allende Type a Coarse-Grained Ca, Al-Rich Inclusion. Meteoritics, 19: 195-197. Carter, A., Roques, D., Bristow, C., et al., 2001. Understanding Mesozoic Accretion in Southeast Asia: Significance of Triassic Thermotectonism (Indosinian Orogeny) in Vietnam. Geology, 29(3): 211-214. https://doi.org/10.1130/0091-7613(2001)0290211:umaisa>2.0.co;2 doi: 10.1130/0091-7613(2001)0290211:umaisa>2.0.co;2 Clift, P. D., Carter, A., Campbell, I. H., et al., 2006. Thermochronology of Mineral Grains in the Red and Mekong Rivers, Vietnam: Provenance and Exhumation Implications for Southeast Asia. Geochemistry, Geophysics, Geosystems, 7(10): Q10005. https://doi.org/10.1029/2006gc001336 Clift, P. D., Long, H. V., Hinton, R., et al., 2008. Evolving East Asian River Systems Reconstructed by Trace Element and Pb and Nd Isotope Variations in Modern and Ancient Red River-Song Hong Sediments. Geochemistry, Geophysics, Geosystems, 9(4): Q04039. https://doi.org/10.1029/2007gc001867 Dung, B. V., Stattegger, K., Unverricht, D., et al., 2013. Late Pleistocene-Holocene Seismic Stratigraphy of the Southeast Vietnam Shelf. Global and Planetary Change, 110: 156-169. https://doi.org/10.1016/j.gloplacha.2013.09.010 Garzanti, E., Padoan, M., Setti, M., et al., 2013. Weathering Geochemistry and Sr-Nd Fingerprints of Equatorial Upper Nile and Congo Muds. Geochemistry, Geophysics, Geosystems, 14(2): 292-316. https://doi.org/10.1002/ggge.20060 Gu, X. X., Liu, J. M., Zheng, M. H., et al., 2002. Provenance and Tectonic Setting of the Proterozoic Turbidites in Hunan, South China: Geochemical Evidence. Journal of Sedimentary Research, 72(3): 393-407. https://doi.org/10.1306/081601720393 Guo, Y. L., Yang, S. Y., Su, N., et al., 2018. Revisiting the Effects of Hydrodynamic Sorting and Sedimentary Recycling on Chemical Weathering Indices. Geochimica et Cosmochimica Acta, 227: 48-63. https://doi.org/10.1016/j.gca.2018.02.015 Harden, P. O., Sundborg, A., 1992. The Lower Mekong Basin Suspended Sediment Transport and Sedimentation Problems. AB Hydroconsult, Uppsala. Hennig, J., Breitfeld, H. T., Gough, A., et al., 2018. U-Pb Zircon Ages and Provenance of Upper Cenozoic Sediments from the Da Lat Zone, SE Vietnam: Implications for an Intra-Miocene Unconformity and Paleo-Drainage of the Proto-Mekong River. Journal of Sedimentary Research, 88(4): 495-515. https://doi.org/10.2110/jsr.2018.26 Hennig, J., Breitfeld, H. T., Hall, R., et al., 2017. The Mesozoic Tectono-Magmatic Evolution at the Paleo-Pacific Subduction Zone in West Borneo. Gondwana Research, 48: 292-310. https://doi.org/10.1016/j.gr.2017.05.001 Nguyen, H. H., Carter, A., Hoang, L. V., et al., 2018. Provenance, Routing and Weathering History of Heavy Minerals from Coastal Placer Deposits of Southern Vietnam. Sedimentary Geology, 373: 228-238. https://doi.org/10.1016/j.sedgeo.2018.06.008 Hoang, N., Flower, M. F. J., 1998. Petrogenesis of Cenozoic Basalts from Vietnam: Implication for Origins of a 'Diffuse Igneous Province'. Journal of Petrology, 39(3): 369-395. https://doi.org/10.1093/petroj/39.3.369 Holeman, J., N., 1968. The Sediment Yield of Major Rivers of the World. Water Resources Research, 4(4): 737-747. https://doi.org/10.1029/WR004i004p00737 Hu, Z. C., Gao, S., 2008. Upper Crustal Abundances of Trace Elements: A Revision and Update. Chemical Geology, 253(3-4): 205-221. https://doi.org/10.1016/j.chemgeo.2008.05.010 Khuc, V., 2011. Stratigraphic Units of Vietnam. Vietnam National University Publishing House, Hanoi. Lepvrier, C., van Vuong, N., Maluski, H., et al., 2008. Indosinian Tectonics in Vietnam. Comptes Rendus Geoscience, 340(2-3): 94-111. https://doi.org/10.1016/j.crte.2007.10.005 Li, C., Yang, S. Y., 2010. Is Chemical Index of Alteration (CIA) a Reliable Proxy for Chemical Weathering in Global Drainage Basins- American Journal of Science, 310(2): 111-127. https://doi.org/10.2475/02.2010.03 Liu, C., Clift, P. D., Murray, R. W., et al., 2017. Geochemical Evidence for Initiation of the Modern Mekong Delta in the Southwestern South China Sea after 8 Ma. Chemical Geology, 451: 38-54. https://doi.org/10.1016/j.chemgeo.2017.01.008 Liu, J. L., Tran, M. D., Tang, Y., et al., 2012. Permo-Triassic Granitoids in the Northern Part of the Truong Son Belt, NW Vietnam: Geochronology, Geochemistry and Tectonic Implications. Gondwana Research, 22(2): 628-644. https://doi.org/10.1016/j.gr.2011.10.011 Liu, J. P., DeMaster, D.J., Nguyen, T.T., et al., 2017. Stratigraphic Formation of the Mekong River Delta and Its Recent Shoreline Changes. Oceanography, 30(3): 72-83. https://doi.org/10.5670/oceanog.2017.316 Liu, Z. F., Colin, C., Huang, W., et al., 2007. Climatic and Tectonic Controls on Weathering in South China and Indochina Peninsula: Clay Mineralogical and Geochemical Investigations from the Pearl, Red, and Mekong Drainage Basins. Geochemistry, Geophysics, Geosystems, 8(5): Q05005. https://doi.org/10.1029/2006gc001490 Liu, Z. F., Colin, C., Trentesaux, A., et al., 2004. Clay Mineral Records of East Asian Monsoon Evolution during Late Quaternary in the Southern South China Sea. Science in China (Series D), 34(3): 272-279 (in Chinese). Liu, Z. F., Zhao, Y. L., Li, J. R., et al., 2007. Late Quaternary Clay Minerals off Middle Vietnam in the Western South China Sea: Implications for Source Analysis and East Asian Monsoon Evolution. Science in China (Series D), 37(9): 1176-1184 (in Chinese). McLennan, S. M., Taylor, S. R., 1982. Geochemical Constraints on the Growth of the Continental Crust. The Journal of Geology, 90(4): 347-361. https://doi.org/10.1086/628690 Nesbitt, H. W., Young, G. M., 1982. Early Proterozoic Climates and Plate Motions Inferred from Major Element Chemistry of Lutites. Nature, 299(5885): 715-717. https://doi.org/10.1038/299715a0 Nguyen, T. T. B., Satir, M., Siebel, W., et al., 2004. Granitoids in the Dalat Zone, Southern Vietnam: Age Constraints on Magmatism and Regional Geological Implications. International Journal of Earth Sciences, 93(3): 329-340. https://doi.org/10.1007/s00531-004-0387-6 Piman, T., Shrestha, M., 2017. Case Study on Sediment in the Mekong River Basin: Current State and Future Trends. Sotckholm Environment Institute, Stockholm. Qiao, P. J., Shao, L., Yang, S. Y., 2006. The Paleoenvironmental Significance of the Character of the Element Geochemistry in the Southwestern South China Sea since Late Pleistocene. Marine Geology & Quaternary Geology, 26(4): 59-65 (in Chinese with English abstract). Roser, B. P., Korsch, R. J., 1999. Geochemical Characterization, Evolution and Source of a Mesozoic Accretionary Wedge: The Torlesse Terrane, New Zealand. Geological Magazine, 136(5): 493-512. https://doi.org/10.1017/s0016756899003003 Roser, B. P., Korsch, R. J., 1988. Provenance Signatures of Sandstone-Mudstone Suites Determined Using Discriminant Function Analysis of Major-Element Data. Chemical Geology, 67(1-2): 119-139. https://doi.org/10.1016/0009-2541(88)90010-1 Shi, M. F., Lin, F. C., Fan, W. Y., et al., 2015. Zircon U-Pb Ages and Geochemistry of Granitoids in the Truong Son Terrane, Vietnam: Tectonic and Metallogenic Implications. Journal of Asian Earth Sciences, 101: 101-120. https://doi.org/10.1016/j.jseaes.2015.02.001 Stattegger, K., Tjallingii, R., Saito, Y., et al., 2013. Mid to Late Holocene Sea-Level Reconstruction of Southeast Vietnam Using Beachrock and Beach-Ridge Deposits. Global and Planetary Change, 110: 214-222. https://doi.org/10.1016/j.gloplacha.2013.08.014 Tran, H. T., Zaw, K., Halpin, J. A., et al., 2014. The Tam Ky-Phuoc Son Shear Zone in Central Vietnam: Tectonic and Metallogenic Implications. Gondwana Research, 26(1): 144-164. https://doi.org/10.1016/j.gr.2013.04.008 Wang, F., Wu, Y. M., Ding, W. W., 2021. Sedimentary Budget and Controlling Factors of the Northwest and Southwest Sub-Basins, the South China Sea. Earth Science, 46(3): 986-1007 (in Chinese with English abstract). Wang, H. X., Liu, Z. F., Wu, J. W., et al., 2021. Clay Mineralogical Record and Its Paleoenvironmental Significance during Marine Isotope Stage 3 on the Sunda Shelf, Southern South China Sea. Earth Science, 46(10): 3467-3480 (in Chinese with English abstract). Yang, S. Y., 2006. Advances in Sedimentary Geochemistry and Tracing Applications of Asian Rivers. Advances in Earth Science, 21(6): 648-655 (in Chinese with English abstract). Yang, S. Y., Li, C. X., Jung, H. S., et al., 2003. Geochemistry of Trace Elements in Chinese and Korean River Sediments. Marine Geology & Quaternary Geology, 23(2): 19-24 (in Chinese with English abstract). Yang, S. Y., Bi, L., Li, C., et al., 2015. Major Sinks of the Changjiang (Yangtze River)-Derived Sediments in the East China Sea during the Late Quaternary. Geological Society, London, Special Publications, 429(1): 137-152. https://doi.org/10.1144/sp429.6 Zhao, C. Q., Zhao, L., Cao, S. Y., et al., 2014. Cenozoic Deformation-Metamorphic Evolution of the Diancang Shan Metamorphic Complex and Regional Tectonic Implications. Acta Petrologica Sinica, 30(3): 851-866 (in Chinese with English abstract). Zhang, L. S., Schärer, U., 1999. Age and Origin of Magmatism along the Cenozoic Red River Shear Belt, China. Contributions to Mineralogy and Petrology, 134(1): 67-85. https://doi.org/10.1007/s004100050469 刘志飞, Colin, C., Trentesaux, A., 等, 2004. 南海南部晚第四纪东亚季风演化的粘土矿物记录. 中国科学(D辑), 34(3): 272-279. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK200403008.htm 刘志飞, 赵玉龙, 李建如, 等, 2007. 南海西部越南岸外晚第四纪黏土矿物记录: 物源分析与东亚季风演化. 中国科学(D辑), 37(9): 1176-1184. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK200709005.htm 乔培军, 邵磊, 杨守业, 2006. 南海西南部晚更新世以来元素地球化学特征的古环境意义. 海洋地质与第四纪地质, 26(4): 59-65. https://www.cnki.com.cn/Article/CJFDTOTAL-HYDZ200604011.htm 王菲, 吴艳梅, 丁巍伟, 2021. 南海西北与西南次海盆沉积通量及其控制因素. 地球科学, 46(3): 986-1007. doi: 10.3799/dqkx.2020.330 王红星, 刘志飞, 吴家望, 等, 2021. 南海南部巽他陆架氧同位素3期粘土矿物记录及其古环境意义. 地球科学, 46(10): 3467-3480. doi: 10.3799/dqkx.2020.161 杨守业, 2006. 亚洲主要河流的沉积地球化学示踪研究进展. 地球科学进展, 21(6): 648-655. doi: 10.3321/j.issn:1001-8166.2006.06.013 杨守业, 李从先, Jung, H.S., 等, 2003. 中韩河流沉积物微量元素地球化学研究. 海洋地质与第四纪地质, 23(2): 19-24. https://www.cnki.com.cn/Article/CJFDTOTAL-HYDZ200302003.htm 赵春强, 赵利, 曹淑云, 等, 2014. 点苍山变质杂岩新生代变质‒变形演化及其区域构造内涵. 岩石学报, 30(3): 851-866. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB201403023.htm -
点击查看大图
计量
- 文章访问数: 1178
- HTML全文浏览量: 536
- PDF下载量: 90
- 被引次数: 0
