Primary dolostone related to the Cretaceous lacustrine hydrothermal sedimentation in Qingxi sag, Jiuquan Basin on the northern Tibetan Plateau

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• 作者：HuaGuo Wen (1) (2)
  RongCai Zheng (1) (2)
  Hairuo Qing (3)
  MingTao Fan (4)
  YanAn Li (2)
  BoShi Gong (2)
  
• 关键词：primary ferruginous dolostone ; hydrothermal sedimentation ; fault lakes ; Cretaceous ; Jiuquan Basin
• 刊名：Science China Earth Sciences
• 出版年：2013
• 出版时间：December 2013
• 年：2013
• 卷：56
• 期：12
• 页码：2080-2093
• 全文大小：
• 作者单位：HuaGuo Wen (1) (2)
  RongCai Zheng (1) (2)
  Hairuo Qing (3)
  MingTao Fan (4)
  YanAn Li (2)
  BoShi Gong (2)
  
  1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, 610059, China
  2. Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, 610059, China
  3. Department of Geology, University of Regina, Regina, S4S OA2, Canada
  4. Yumen Oilfield Company of PetroChina, Jiuquan, 735019, China
  
• ISSN：1869-1897

文摘

Based on comprehensive studies in petrography, petrofabric analysis and geochemistry, this paper describes a unique and rare laminated micritic ferruginous primary dolostone crystallized and precipitated from the alkaline hot brine under the conditions of the Mesozoic faulted lake basin. The main rock-forming mineral of this dolostone is ferruginous dolomite with a micritic structure. This dolomite mostly exhibits laminae of 0.1–1 mm thick and is often discovered with other minerals, such as albite, analcite, barite and dickite, which have at least two types of interbedded laminae. Petrogeochemistry reveals that this dolostone contains a large number of typomorphic elements of hydrothermal sedimentation, including Sb, Ba, Sr, Mn, and V. In addition, the LREE is in relatively high concentrations and possesses the typical REE distribution pattern with negative Eu anomaly. Oxygen isotope values (δ18OPDB) range from 5.89‰ to 14.15‰ with an average of 9.69‰. The ratio of 87Sr/86Sr is between 0.711648 and 0.719546, with an average of 0.714718. These data indicate that the depositional environment is a stable, blocked, anoxic low-lying hot brine pool in the bottom of deep lake controlled by basement faults. The hydrothermal fluid is the alkaline hot brine formed by the combination of the infiltration lake water and mantle-derived magmatic water, consisting of many ions, including Ca2+, Mg2+ and Fe2+. Under the driving flow power of magmatic heat, gravity and compaction, the hydrothermal fluid overcame the overburden pressure and hydrostatic pressure of the lake water body, and boiled to explosion, and then the explosion shattered the original laminated micritic ferruginous primary dolostone near the vent and then formed a new type of dolostone called shattered “hydroexplosion breccias”. In the low-lying, unperturbed hot brine pool, far from the vent, the laminated micritic ferruginous primary dolostone was quickly crystallized and chemicals precipitated from the hydrotherm. This study of special rocks contributes to research into the causes of the formation of lacustrine carbonate rocks and dolostone. In particular, it provides new examples and research insights for future studies of the lacustrine dolomite from the similar Mesozoic and Cenozoic basins in China.