Type and origin of the Lower Paleozoic dolostones in Tarim Basin
Zhang Demin1, 2, Bao Zhidong1, 2, Pan Wenqing3, Hao Yan4, Chen Min1
1 College of Geosciences, China University of Petroleum(Beijing), Beijing 102249 2 State Key Laboratory for Petroleum Resource and Prospecting, China University of Petroleum(Beijing), Beijing 102249 3 Research Institute of Petroleum Exploration and Development, Tarim Oilfield Company, PetroChina, Korla 841000, Xinjiang 4 Sinopec Overseas Oil & Gas Ltd. , Beijing 100029
Abstract：There was a huge exploration potential in the Lower Paleozoic dolostones of Tarim Basin. In a combination of former classification schemes and based on the analysis of tectonic evolution and sedimentary background, the Lower Paleozoic dolostone was classified into two types (penecontemporaneous dolostones and post-penecontemporaneous dolostones) according to its forming time. Furthermore, more detailed subtypes were divided through combining the data of cores, thin sections, cathodoluminescence(CL), scanning electron microscope(SEM) and stable isotopes (δ13, C and δ18, O). And penecontemporaneous dolostones could be divided into three subtypes, including penecontemporaneous dolostones in supratidal flat environments, penecontemporaneous dolostones in lagoons, and microbial dolostones. The former two subtypes were dolomitized by evaporating seawater in arid environment and complete dumbbell-like dolomite was firstly found in gypsum moldic pore, which expanded the existence area of the microbial dolomite. While post-penecontemporaneous dolostones could be divided into three subtypes: shallow burial dolostones, middle-deep burial dolostones and hydrothermal dolomites. Shallow burial dolostones were dolomitized by adjusting|pore water and infiltrating reflux of brine. Middle-deep burial dolostones were occurred in middle-deep burial. The hydrothermal dolomites|were dolomitized by hydrothermal fluids along faults/fractures.
