Geochemical Differentiation and Genesis of Volcanic Rock Weathered Soil from the Downstream of the Nandu River on Northern Hainan Island
-
摘要: 海南岛北部的第四纪火山岩分布区是我国玄武岩风化成土最活跃的地区之一，对于理解热带成壤过程的元素地球化学行为具有重要意义。本文选取琼北南渡江下游两岸多期火山岩上的心土及风化剖面，系统探讨该区土壤的主量与稀土元素分异特征。研究发现，玄武岩风化土壤的主量元素组成均以SiO2、Al2O3、TFe2O3为主，三者总含量在73.62% 以上，MgO、CaO、Na2O 和K2O 强烈淋滤流失。除全新世石山组玄武岩风化的心土样品外，其它期次火山岩风化心土样品的风化程度均为极端风化，CIA 值（化学蚀变指数）多处于91.0 以上，且平均的CIA(Qp2d1)>CIA(Qp2d2))>CIA(Qp3d2)>CIA (Qhs) ，表现为成土年龄越老，风化程度越高。本次研究还发现，无论是面上分布的心土样品还是剖面土壤样品，均为轻稀土富集的右倾模式，Eu 异常不显著，剖面土壤样品ΣREE与CIA 之间呈现负相关。不同期次玄武岩风化土壤均呈现显著的Ce 正异常，可能与琼北地区处于热带湿热气候区，受强烈的风化淋滤作用有关。Abstract: The Quaternary volcanic region on northern Hainan Island is one of the most active areas of weathering in China, and is of great significance for understanding the element geochemical behavior during the basalt weathering. We analysis the major and trace element compositions of both subsoils from different periods of weathered basalts and soil samples from typical weathering profile in the downstream of the Nandu River on northern Hainan to investigate their differentiation mechanism. It is found that the major elements of volcanic weathering soils are SiO2, Al2O3 and TFe2O3 with the total content of more than 73.62%, and their MgO, CaO, Na2O, K2O were strongly leached. Except for the weathered core soil samples of the Holocene Shishan Formation basalts, the other subsoil samples derived from different periods of volcanic rocks were extremely weathered, and their CIA (chemical alteration index) values are all higher than 91.0 with the average CIA value trend of CIA(Qp2d1)>CIA(Qp2d2))>CIA(Qp3d2)>CIA (Qhs) , which indicates that the older soils underwent more weathering. Besides, both the regional subsoil and soil samples from the profile of the weathering basalts share the similar REE characteristics, such as right-lean pattern of LREE enrichment and insignificant Eu anomaly, and negative correlation between ΣREE and CIA values on the profile. The significant positive Ce anomaly in both the subsoil and soil samples from the different basalt weathering profiles might be correlated with the strongly weathering and leaching under the tropical hot humid climate of northern Hainan Island.
-
-
[1] White A F, Blum A E. Effects of climate on chemical weathering rates in watersheds[J]. Geochimica et Cosmochimica Acta, 1995, 59(9): 1727-1736.[br][2] Lasaga A C, Soler J M, Ganor J. Chemical weathering rate laws and global geochemical cycles[J]. Geochimica et Cosmochimica Acta, 1994, 58(10): 2361-2386. [R][3] Bluth G J S, Kump L R. Lithologic and climatologic controls of river chemistry[J]. Geochimica et Cosmochimica Acta, 1994, 58(10): 2341-2359. [br][4] Berner R A. Chemical weathering and its effect on atmospheric CO2 and climate [J]. Reviews in Mineralogy and Geochemistry, 1995, 31(1):565-583. [br][5] Louvat P, Allègre C J. Present denudation rates on the island of Reunion determined by river geochemistry: basalt weathering and mass budget between chemical and mechanical erosions[J]. Geochimica et Cosmochimica Acta, 1997, 61 (17): 3645-3669. [br][6] Dessert C, Dupré B, Gaillardet J, Franois L M , Allègre C J. Basalt weathering laws and the impact of basalt weathering on the global carbon cycle[J]. Chemical Geology, 2003, 202(3): 257-273. [br][7] Ma J L, Wei G J, Xu Y G Long W G, Sun W D. Mobilization and redistribution of major and trace elements during extreme weathering of basalt in Hainan Island, South China[J]. Geochimica et Cosmochimica Acta, 2007, 71(13): 3223-3237. [br][8] Jiang K, Qi H W, Hu R Z. Element mobilization and redistribution under extreme tropical weathering of basalts from the Hainan Island, South China[J]. Journal of Asian Earth Sciences, 2018, 158(1): 80-102. [br][9] 黄成敏，龚子同. 土壤发育过程中稀土元素的地球化 学指示意义[J]. 中国稀土学报, 2000,18 (2): 150-155. [br][10] 徐义芳，朱照宇，文高国，梁俊平，罗树文. 雷州半岛南部若干红土剖面的地球化学与成土环境研究[J]. 地球化学,2000,29(4): 402-409. [br][11] 张立娟，李徐生，李德成，韩志勇，张甘霖. 雷州半岛玄武岩母质土壤剖面稀土元素分布及其与常量元素、粒度的关系[J]. 土壤学报,2011, 48(1): 1-9. [br][12] 黄镇国，蔡福祥，韩中元. 雷琼第四纪玄武岩[M]. 北京：科学出版社, 1993: 170-188. [br][13] 樊祺诚, 孙 谦, 李 霓, 隋建立. 琼北火山活动分期与全新世岩浆演化[J]. 岩石学报, 2004,20(3): 533-544. [br][14] Wang X C, Li Z X, Li X H, Li J, Liu Y, Long W G, Zhou J B, Wang F. Temperature, Pressure, and Composition of the Mantle Source Region of Late Cenozoic Basalts in Hainan Island, SE Asia: a Consequence of a Young Thermal Mantle Plume close to Subduction Zones [J]? Journal of Petrology,2012, 53(1): 177-233. [br][15] Liu J Q, Ren Z Y, Nichols A R L, Song M S, Qian S P, Zhang Y, Zhao P P. Petrogenesis of Late Cenozoic basalts from North Hainan Island: constraints from melt inclusions and their host olivines[J]. Geochimica et Cosmochimica Acta,2015, 152: 89-121. [br][16] 段 政, 张 翔, 周 翠, 余明刚, 褚平利, 洪文涛. 琼北地区第四纪火山地质遗迹类型与地学意义[J]. 地球学报, 2021, 42(1): 111-123. [br][17] 黄成敏，龚子同. 海南岛北部玄武岩上土壤发生研究Ⅲ . 元素地球化学特征[J]. 土壤学报,2002, 39(5): 643-652. [br][18] Huang K J, Teng F Z, Wei G J, Ma J L, Bao Z Y. Adsorption and desorption controlled magnesium isotope fractionation during extreme weathering of basalt in Hainan Island, China[J]. Earth and Planetary Science Letters, 2012, 359-360: 73-83. [br][19] Ma J L, Wei G J, Xu Y G, Long W G. Variations of Sr-Nd-Hf isotopic systematics in basalt during intensive weathering[J]. Chemical Geology, 2010, 269(3): 376–385. [br][20] 朱 鑫, 汪 实, 李婷婷. 雷州半岛土壤地球化学背景值研究[J]. 华南地质，2021，37（1）：103-112. [br][21] 都 凯. 中国东部新生代玄武岩风化作用地球化学研究[D]. 南京大学硕士学位论文, 2012. [br][22] 黄成敏, 龚子同. 海南岛北部玄武岩上土壤发生的化学特性研究[J]. 热带地理, 2001, 21(3): 207-212. [br][23] 朱维晃, 杨元根, 毕 华, 刘 强. 海南土壤中稀土元素含量及分布特征[J]. 地球与环境, 2004,32 (2): 20-25. [br][24] Long X Y, Ji J F, Balsam W. Rainfall dependent transformations of iron oxides in a tropical saprolite transect Hainan Island, South China: spectral and magnetic measurements[J]. Journal of Geophysical Research: Earth Surface, 2011, 116(F3). [br][25] 龙文国. 琼海县幅E49C001002 1/25 万区域地质调查报告[R]. 海南省地质调查院, 2004. [br][26] Sun S S, Mcdonough W F. Chemical and Isotopic Systematics of Oceanic Basalts: Implications for Mantle Composition and Processes, in Magmatism in the Ocean Basins[J]. Geological Society of London Special Publications, 1989, 42: 313-345. [br][27] Nesbitt H W, Young G M. Early Proterozoic climates and plate motions inferred from major element chemistry of lutites[J]. Nature,1982, 299(5885): 715-717. [br][28] 邹海波, 郭紫佩, 樊祺诚, 赵勇伟. 中国东部全新世火山的镭- 钍同位素年代学[J]. 岩石学报, 2020, 36(7): 1945-1952. [br][29] 刘奇志. 吉林省东部玄武岩风化成壤过程中的元素地球化学特征[D]. 吉林大学硕士学位论文, 2018. [br][30] 杨元根，刘丛强，袁可能，何振立. 南方红土形成过程及其稀土元素地球化学[J]. 第四纪研究，2000, 20(5):469-480. [br][31] 冉 勇, 刘 铮. 我国主要土壤中稀土元素的含量和分布[J]. 中国稀土学报, 1994, 12 (3): 248-252. [br][32] Braun J J, Pagel M, Muller J P, Bilong P, Michard A, Guillet B. Cerium anomalies in lateritic profiles[J]. Geochimica et Cosmochimica Acta, 1990, 54 (3): 781-795. [br][33] 杨 恬，朱照宇，吴 翼，邱世藩, 饶志国, 韩江伟. 中国东部地带表土稀土元素的地球化学特征[J]. 地学前缘,2010, 17(3): 233-241. [br]
-
计量
- 文章访问数: 382
- PDF下载数: 50
- 施引文献: 0
下载: