滇西南昌宁—孟连带三叠纪牡音河组硅质岩地球化学特征及沉积环境

张振芳; 冯庆来; 方念乔; 黄军义; 李世雄; 陈学方

Volume 26 Issue 5

Sep. 2001

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Article Navigation > Earth Science > 2001 > 26(5): 449-455

Zhang Zhenfang, Feng Qinglai, Fang Nianqiao, Huang Junyi, Li Shixiong, Chen Xuefang, 2001. GEOCHEMICAL CHARACTERISTICS AND SEDIMENTARY ENVIRONMENT OF TRIASSIC SILICEOUS ROCKS FROM MUYINHE FORMATION IN CHANGNING-MENGLIAN BELT, SOUTHWEST YUNNAN. Earth Science, 26(5): 449-455.

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GEOCHEMICAL CHARACTERISTICS AND SEDIMENTARY ENVIRONMENT OF TRIASSIC SILICEOUS ROCKS FROM MUYINHE FORMATION IN CHANGNING-MENGLIAN BELT, SOUTHWEST YUNNAN

1.
Faculty Earth Sciences and Mineral Resources, China University of Geosciences, Beijing 100083, China
2.
Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China
3.
China National Geology and Mining Corporation, Beijing 100081, China

Received Date: 2000-12-05
Publish Date: 2001-09-25

Abstract

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.
- biological marker compound,
- REE,
- depositional tectonic setting,
- siliceous rock,
- Middle Triassic,
- Southwest Yunnan

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References(22)

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