期刊
JOURNAL OF ASIAN EARTH SCIENCES
卷 105, 期 -, 页码 456-467出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jseaes.2015.02.024
关键词
Junggar Basin; Permian strata; Dolostone formation; Model of origin
资金
- National Science and Technology Major Project of China [2011ZX05000-01-06]
- National Key Basic Research Program - 973 Project [2011CB201104]
- Western Doctoral Funds of Chinese Academy of Sciences
- Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics Chinese Academy of Sciences
This study investigates the mechanism of dolostone formation and establishes a dolomitization model in the Permian strata on the northwestern margin of Junggar Basin, China. Dolomitic rock samples are collected from the Permian Fengcheng Formation in Urho area and then characterized by petrological, mineralogical, carbon and oxygen isotope, and trace element geochemical analyses. Results show that the major types of dolomitic rocks include dolomitic mudstone, dolomitic siltstone, dolomitized tuffaceous siltstone, and dolomitized tuffaceous mudstone. The dolomitized rocks are dominated by euhedral or subhedral powder- and fine-crystal dolomites formed by replacement lacustrine argilla-calcareous and siliceous (tuffaceous) components and commonly filled with residual and late calcite cements. The parameters of dolomitic rocks show great variations, including the V/Ni ratio (1.02-4.88), Sr content (95.9-783.6 mu g/g), Mg/Ca ratio (0.68-5.13), degree of ordering (0.39-1.00), delta O-18(PDB) (-14.8 parts per thousand to 3.2 parts per thousand), and delta C-13(PDB) (-1 parts per thousand to 5.2 parts per thousand). The dolomitic rocks have multi-stage origins and were formed in a semiclosed continental brackish-saltwater bay with weak hydrodynamic processes, deep water bodies, and relatively quiet conditions. In the Permian depositional stage, a combination of complex tectonic activities, fault development, hot subtropical climate, and frequent volcanic activities provided not only Mg2+ source for dolomitization but also channels for rapid flow and seepage of Mg-rich fluids. The origins of dolostones in the study area include penecontemporaneous dolomitization, burial dolomitization, and hydrothermal dolomitization. This study lays a foundation for further studies on dolomite formation and dolomite reservoir, and provides effective methods for researching complex dolostone (tuffaceous, shale and silty dolomite) formation. (C) 2015 Elsevier Ltd. All rights reserved.
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