摘要:
关于东营凹陷古近系咸化机制的争论已持续近三十年,其中沙四上亚段是该区最为重要的烃源岩之一,查明其咸化机制及沉积特征是重要且必要的。本文从沉积物、古生物、地球化学三方面着手,分析咸化机制中最重要的两个问题:盐源与成盐机制。结果表明:通过分析本区的沉积物(白云岩、海绿石及岩相组合)、古生物(中华直管藻等)、地球化学三方面特征,证明东营凹陷在古近系确实遭受过海水影响,并将时间具体到沙四上亚段的早期。海水是由地震引发的四期海啸所带来。在此基础上,分析得出研究区早期盐源以海水侵入为主,中后期以母岩风化造成的古盐释放、火山或岩浆活动、深层卤水上涌三种盐源为主,具有多种盐源分段控制的特点。成盐机制有机械成因、化学成因、生物成因及复合成因四种,具有海陆相盐类并存,成因复杂的特点。针对此特殊现象,本文提出从地球化学及阴极发光等方面对共存的海陆相碳酸盐岩进行区分,以期引起同行的关注与讨论。
关键词:
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东营凹陷
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沙四上亚段
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咸化
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海啸
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盐源
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成盐机制
Abstract:
The debate on the salty mechanism has been going on for nearly three decades in Dongying Sag, the upper part of fourth member of Shahejie formation, as the area's most important source rocks, its salty mechanism and sedimentary characteristics are important and necessary to be researched. Based on the research of sediment, palaeontology and geochemistry, the two most important aspects of the salty mechanism-salt source and halogenesis are analysised. The results showed that sedimentary (dolomite, glauconite, and lithofacies sets), paleontologists(ortonella), geochemical characteristics proved Dongying Sag was suffered from sea water on the upper part of Es4.The sea water were brought by four periods of tsunami that induced by earthquake. Based on these, the early salt source mainly is intrusion of sea water, in the middle and later periods, mother rock weathering that caused the release of the ancient salt, volcanic or magmatic activity, deep brine upwelling are the mainly salt sources. It has a variety of salt sources that control different interval. There are four kinds of halogenesis: mechanical origin, chemical origin, biogenesis and multiple genesis. With the coexistence of the land and sea saline deposit, its causes are complex. In response to this special phenomenon, marine carbonatite and lacustrine carbonatite are distinguished by the use of geochemical and cathodeluminescence. It can arouse scholars’ attention and discuss.
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