GEOCHEMICAL CHARACTERISTICS AND SEDIMENTARY ENVIRONMENT OF TRIASSIC SILICEOUS ROCKS FROM MUYINHE FORMATION IN CHANGNING-MENGLIAN BELT, SOUTHWEST YUNNAN
-
摘要: 滇西南昌宁—孟连带牡音河组硅质岩已进行了较好的生物地层学和沉积学研究, 表明为中三叠世深水盆地沉积, 但对其沉积构造背景存在不同的认识. 本文尝试用分子有机地球化学方法, 并辅以无机地球化学的手段, 研究牡音河组硅质岩的物源环境, 分析沉积区构造背景. 研究结果表明硅质岩中正构烷烃碳数分布范围较宽C14—C36, 且具双峰型分布模式, 说明其有机质为陆生高等植物和水生生物混合来源; 萜类和甾类化合物特征说明研究区有机质来源总体上以水生生物为主, 同时有不同程度陆生高等植物混入. 牡音河组硅质岩Σw (REE) 为83.56 × 10-6 124.1 × 10-6, w (Ce)/w (Ce) 在0.760.99之间变化, w (La)n/w (Yb)n在0.771.98之间, 说明该盆地明显受陆源区物质影响. 另外, 该硅质岩的w (La)n/w (Ce)n和w (Al2O3)/w (Al2O3+Fe2O3) 图解及w (MnO)/w (TiO2) 比值也说明牡音河组硅质岩沉积过程中受到大陆作用. 两方面的特征互相印证, 说明研究区中三叠世为受陆地强烈作用的深水局限盆地. 这项研究还说明, 分子有机地球化学方法能够为硅质岩沉积环境的探讨提供更多的物源和环境信息.Abstract: Detailed studies of biostratigraphy and sedimentology of the siliceous rocks from the Muyinhe Formation in the Changning-Menglian belt, Southwest Yunnan indicate that the deposition occurred in a deep-water basin in Middle Triassic. However, its depositional tectonic setting is little understood. The main purpose of this article is to analyze its provenance and depositional tectonic background by using molecular organic geochemistry and inorganic geochemistry. The carbon number distribution of the normal paraffin in the siliceous rock is relatively wide, C14-C36, with two peaks, which implies that this organic matter is derived from both higher terrigenous plants and marine autochthonous organisms. The features of the steroid and terpenoid hydrocarbons suggest that the organic is mainly originated from marine sources mixed with terrigenous sources. The REE characteristics of the siliceous rock are as followed: total w (REE) ranges from 83.56 × 10-6 to 124.1 × 10-6, w (Ce)/w (Ce*) between 0.76 and 0.99, w (La)n/w (Yb)n from 0.77 to 1.98. These characteristics show that the basin was apparently influenced by terrigenous sources. In addition, w (MnO)/w (TiO2) ratio and w (La)n/w (Ce)n vs. w (Al2O3)/w (Al2O3+Fe2O3) plot consistently show that the chert was influenced by land sources during its depositional process. While the incorporating characteristics of the organic and inorganic in the siliceous rocks suggest that the studied area was a limited deep-water basin and was strongly influenced by terrigenous matter and that molecular organic geochemistry can provide more information about the provenance and sedimentary environment of siliceous rocks.
-
Key words:
- biological marker compound /
- REE /
- depositional tectonic setting /
- siliceous rock /
- Middle Triassic /
- Southwest Yunnan
-
图 1 研究区交通位置和地质简图
1.下-中三叠统牡音河组; 2.石炭—二叠系拉巴群; 3.石炭—二叠系灰岩; 4.下石炭统平掌组; 5.断层; 6.地质界线; 7.剖面位置
图 3 w (La)n/w (Ce)n-w (Al)/w (Al+Fe) 图解
Fig. 3. w (La)n/w (Ce)n-w (Al)/w (Al+Fe) diagram
表 1 反映环境的生物标志化合物参数
Table 1. Biomarker parameters reflecting depositional environment
表 2 生物标志化合物参数计算
Table 2. Calculation and interpretation of biomarker parameters
表 3 牡音河组硅质岩中稀土元素质量分数及特征
Table 3. REE mass fractions and features of chert from Muyinhe Formation
表 4 牡音河组硅质岩中常量元素质量分数及特征
Table 4. Mass fractions and features of major elements in siliceous rocks from Muyinhe Formation
-
[1] Liu B P, Feng Q L, Fang N Q. Tectonic evolution of the Palaeo-Tethys in Changning-Menglian belt and adjacent regions, Western Yunnan[J]. Journal of China University of Geosciences, 1991, 2(2): 18-23. [2] 丁林, 钟大赉. 滇西昌宁—孟连带古特提斯洋硅质岩稀土元素和铈异常特征[J]. 中国科学(B辑), 1995, 25 (1): 93-100. https://www.cnki.com.cn/Article/CJFDTOTAL-JBXK199501014.htm [3] 冯庆来, 刘本培. 滇西南晚二叠世和早、中三叠世放射虫动物群及其地质意义[J]. 地球科学——中国地质大学学报, 1993, 18(5): 540-552. [4] 方念乔, 刘本培, 冯庆来. 滇西南牡音河组的沉积特征、环境意义及与之相关的若干地质问题[J]. 地球科学——中国地质大学学报, 1996, 21(1): 11-18. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX601.001.htm [5] Zhang Z F, Feng Q L. Preliminary studies of Triassic radiolarians from Muyinhe Formation in Southwest Yunnan, China[A]. In: Yin H F, Tong J N, eds. Proceedings of the international conference on Pangea and the PaleozoicMesozoic transition[C]. Wuhan: China University of Geosciences Press, 1999. 74-79. [6] Feng Q L, Yang F Q, Zhang Z F, et al. Radiolarian evolution during the Permian and Triassic transition in South and Southwest China[A]. In: Yin H F, Dickins J M, Shi G R, et al, eds. Permian-Triassic evolution of Tethys and western circum-Pacific[C]. Amsterdam: Elsevier, 2000. 309-326. [7] 傅家谟, 盛国英. 分子有机地球化学与古气候、古环境研究[J]. 第四纪研究, 1992, 4: 306-320. doi: 10.3321/j.issn:1001-7410.1992.04.003 [8] Tissot B P, Pelet R, Rouchache J, et al. Alkanes as geochemical fossils indicators of geological environments[A]. In: Campos R, Goni J, eds. Advances in organic geochemistry 1975[C]. Madrid: Enadimsa, 1977. 117-154. [9] Brassel S C, Eglinton G, Maxwell J R, et al. Natural background of alkanesin the aquatic environment[A]. In: Hutzinger O, Van Lelyveld I H, Zoeteman B C J, eds. Aquatic pollutants[C]. Oxford: Programon Press, 1978. 69-86. [10] 阳学贤, 盛国英, 卢家烂, 等. 内蒙古湖洞察汗淖(碱)湖沉积物中的生物标志物特征及古环境意义[J]. 地球化学, 1996, 25(6): 536~543. doi: 10.3321/j.issn:0379-1726.1996.06.002 [11] 傅家谟, 盛国英, 许家友, 等. 应用生物标志化合物参数判识古沉积环境[J]. 地球化学, 1991, 20(1): 1-12. doi: 10.3321/j.issn:0379-1726.1991.01.001 [12] Brassell S C, Wardroper A M K, Thomson I D, et al. Specific acyclic isoprenoids as biological markers of methanogenic bacteria in marine sediments[J]. Nature, 1981, 277: 125-127. [13] Mackenzie A S, Brassell S C, Eglinton G, et al. Chemical fossils—the geological fate of steroids[J]. Science, 1982, 217: 491-500. doi: 10.1126/science.217.4559.491 [14] Yamamoto K, Okada T, Takayanagi Y, et al. Normal paraffin in shale as an indicator of depositional environment[J]. Geochimica et Cosmochimica Acta, 1997, 61 (20): 4403-4410. doi: 10.1016/S0016-7037(97)00238-X [15] Murry R W, Buchholtz Ten, Brink M R, et al. Rare earth elements as indicators of different marine depositional environments of chert and shale[J]. Geology, 1990, 18: 268-271. [16] Courtois H. Distribution des terres rares dans les sediments superficiels du Pacifique sud-est[J]. Bulletin de la Societe Geologique de France, 1977, 7: 1245-1251. [17] Murry R W, Buchholtz Ten, Brink M R, et al. Rare earth, major, and trace elements in chert from the Franciscan complex and Monterey Group, California: assessing REE sources to fine-grained marine sediments[J]. Geochimica et Cosmochimica Acta, 1991, 55: 1875-1893. doi: 10.1016/0016-7037(91)90030-9 [18] Murry R W. Chemical criteria to identify the depositional environment of chert: general principles and applications[J]. Sedimentary Geology, 1994, 90: 213-232. doi: 10.1016/0037-0738(94)90039-6 [19] 王东安, 陈瑞君. 雅鲁藏布江缝合带硅质岩的地球化学成因标志及其地质意义[J]. 沉积学报, 1995, 13(1): 27-31. [20] Feng Q L, Ye M, Zhang Z J. Triassic radiolarian fauna from Southwest China[J]. Scientia Geologica Sinica, 1996, 5(3): 381-394. [21] Yao A, Kuwahara K. Paleozoic and Mesozoic radiolarians from the Changning-Menglian terrane, Western Yunnan, China[A]. In: Yao A, Ezaki Y, Hao W, et al, eds. 中国古特提斯生物及地质变迁[C]. 北京: 北京大学出版社, 1999. 17-42. [22] 夏邦栋, 钟立荣, 方中. 下扬子区早二叠世孤峰组层状硅质岩成因[J]. 地质学报, 1995, 69(2): 125-137. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE199502002.htm -
下载:
点击查看大图
图(3) / 表(4)
计量
- 文章访问数: 4299
- HTML全文浏览量: 106
- PDF下载量: 3
- 被引次数: 0
