Formation of Diagenetic Dolomite in Coastal Sabkha Along Arabian (Persian) Gulf
Formation of Diagenetic Dolomite in Coastal Sabkha Along Arabian (Persian) Gulf
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DOI：
10.1306/03b59a17-16d1-11d7-8645000102c1865d
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发表时间：
1982
期刊：
影响因子：
3.5
通讯作者：
R. J. Patterson;D. Kinsman
中科院分区：
文献类型：
--
作者：
R. J. Patterson;D. Kinsman
由于风力驱动的海洋卤水的渗流，阿拉伯潮间带沉积物正在阿拉伯(波斯湾)南岸萨布哈的地下潮上环境中被白云化。大量成岩白云岩的发育是高MMG++/MCA++比值流体的最佳组合，与水淹频率和沉积物渗透率有关的快速流速，以及在足够长的时间内保持适当条件的岸线形态。强烈白云岩化的地区位于残留河道的侧翼和被推进的萨布卡吞没的岛屿的背风处。白云化过程大约需要1000到1500年。大多数成岩白云石是以原生文石为代价形成的，其反应顺序为：Mg+2CaCO3(Arag)，RARRCaMG(CO3)2+Ca++。白云石是在下列条件下形成的：(A)氯浓度在3.25至3.75mCL-/kg之间；(B)MMG++/MCa+大于约6；(C)pH在6.3至6.9之间；(D)最低二氧化碳分压为10-2至10-3atm；(E)温度在25至40℃之间；(F)与石膏有关的饱和度；以及(G)与硫化氢有关的还原环境。巴哈马、佛罗里达和博内尔最近发现的其他白云石在地层、岩化程度和蒸发岩矿物组合方面与阿拉伯湾的白云石显著不同。
Aragonitic intertidal sediments are being dolomitized in the subsurface supratidal environment of a sabkha along the south shore of the Arabian (Persian) Gulf as a result of the percolation of wind-driven marine-derived brines. The development of abundant diagenetic dolomite results from an optimum combination of high mMg++/mCa++ ratio fluids, a rapid flow rate which is related to the flooding frequency and sediment permeability, and a shoreline configuration that maintains the proper conditions for a sufficient length of time. Strongly dolomitized areas are localized along the flanks of remnant channels and in the lee of islands that have been engulfed by the prograding sabkha. The dolomitizing process takes about 1,000 to 1,500 years. Most diagenetic dolomite forms at the expense of primary aragonite according to the reaction: Mg++ + 2CaCO3(arag) ^rarr CaMg(CO3)2 + Ca++. Dolomite forms under the following conditions: (a) chloride concentration between 3.25 and 3.75 mCl-/Kg; (b) mMg++/mCa++ greater than about 6; (c) pH between 6.3 and 6.9; (d) minimum PCO2 of 10-2 to 10-3 atm; (e) temperature between 25 and 40°C; (f) saturation with respect to gypsum; and (g) reducing environment in association with hydrogen sulfide. Other recent dolomite occurrences in the Bahamas, Florida, and Bonaire are significantly different in terms of stratigraphy, degree of lithification, and evaporite mineral association from those in the Arabian Gulf.