Spheroidal dolomites – origin by hydrocarbon seepage?
Spheroidal dolomites – origin by hydrocarbon seepage?
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球状白云岩——碳氢化合物渗漏的起源？
DOI：
10.1111/j.1365-3091.1989.tb02094.x
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发表时间：
1989
期刊：
影响因子：
3.5
通讯作者：
A. Gunatilaka
中科院分区：
文献类型：
--
作者：
A. Gunatilaka
球状白云岩胶结物在科威特五个不同地质年代的出露岩性中普遍存在。球体的直径范围为~ 5-350 μm，具有同心区和流体包裹体核，有或没有径向结构，成分从接近化学计量到Ca56 Mg44不等。所有的球体似乎都是原始的，没有替代的证据。一些同心区表现为选择性计算和/或浸出。这些特征大多局限在地表30米以内。因此，在古层序深处可识别的球状白云岩可能表明局部不整合。
Spheroidal dolomite cements are a pervasive and distinctive feature in five exposed lithologies of different geological age in Kuwait. The spheroids range in diameter from ∼5–350 μm, have concentric zones and nuclei of fluid inclusions with or without a radial fabric, and compositions varying from near stoichiometric to Ca56 Mg44. All spheroids appear to be primary in origin with no evidence of replacement. Some concentric zones show selective calcitization and/or leaching. Most of these features are confined to within 30 m of the surface. Consequently, spheroidal dolomites recognizable at depth in ancient sequences may be indicative of a local unconformity.
The dolomite distributions are areally correlative with known areas of hydrocarbon seepage, the latter being confined to prominent oil field anticlinal trends. It is proposed that the dolomitization was caused by groundwaters carrying hydrocarbons to the surface, which were then oxidized to carbon dioxide. The gas bubbles may have acted as nuclei for spheroid growth with a possible inducement by bacteria which have an affinity for hydrocarbons. The implication is that the regional distribution of spheroidal dolomites may be an indicator of a potential reservoir facies at depth.