發(fā)布時間：2018-01-19 20:04

  本文關(guān)鍵詞： 西沙石島島礁 西科井巖心 白云巖層 稀土元素 成巖環(huán)境 古氣候變化　出處：《海洋通報》2017年02期 　論文類型：期刊論文

【摘要】：西沙群島是南海生物礁體系發(fā)育的典型地區(qū),也是我國生物礁油氣資源勘探與開發(fā)的重點區(qū)域。對采自西沙石島"西科1井"巖心7層共107個白云巖樣品進行了稀土元素(REE)含量測試分析,旨在通過分析白云巖層的REE地球化學特征,探討西沙島礁白云巖的成巖環(huán)境及其與古氣候事件的相互關(guān)系。研究結(jié)果表明:西沙石島礁相碳酸鹽巖中7層白云巖具有相似的REE地球化學特征(含量、配分模式和元素異常等),表明其形成于相近的成巖環(huán)境;埋藏壓實及其所導致的成巖作用未造成白云巖層中REE主要特征的顯著變化,白云巖的REE地球化學特征基本反映了白云巖化作用的成巖環(huán)境及成巖流體的性質(zhì);多種地球化學指標(REE、Sr含量和碳、氧同位素特征)表明,西沙島礁白云巖主要形成于高鹽海水作用條件下的低溫偏氧化環(huán)境,o_湖環(huán)境下高鹽鹵水的滲透回流作用是導致白云巖層形成的主要形式;白云巖的形成在時間上與中新世以來的古氣候變冷事件相對應,氣候變化導致的海平面升降控制了島礁白云巖層的分布;由于氣候變冷在島礁周圍形成礁灘o_湖,相對封閉的o_湖和蒸發(fā)量大于降水量的氣候環(huán)境形成高鹽度鹵水,這種比重較大的高鹽鹵水沿孔隙下滲,交代蝕變早先形成的方解石類碳酸鹽,從而形成了西沙島礁中的白云巖層。
[Abstract]:Xisha Islands is a typical area for the development of reef system in the South China Sea. It is also a key area for exploration and development of oil and gas resources on reefs in China. The REE content of 107 dolomite samples collected from core 7 layers of Xico 1 well in Xisha Island has been tested and analyzed. The purpose of this paper is to analyze the REE geochemical characteristics of dolomite. The diagenetic environment of Xisha reef dolomite and its relationship with paleoclimate events are discussed. The results show that 7 layers of dolomite in the reef carbonate rock of Xisha Island have similar REE geochemical characteristics (content). Distribution patterns and element anomalies indicate that they were formed in similar diagenetic environments. The buried compaction and its diagenesis did not result in significant changes in the main characteristics of REE in dolomite. The REE geochemical characteristics of dolomite basically reflect the diagenetic environment of dolomitization and the properties of diagenetic fluid. A variety of geochemical indicators, such as REE Sr content and carbon and oxygen isotopic characteristics, indicate that the dolomite on Xisha island reef is mainly formed in a low-temperature partial oxidation environment under the condition of high-salt seawater. The osmotic reflux of high-salt brine is the main form of dolomite formation in the environment of O _ lake. The formation of dolomite corresponds to the paleoclimate cooling event since Miocene. The sea level rise and fall caused by climate change control the distribution of reef dolomite. Due to the cooling of the climate, the reef beach och is formed around the islands and reefs, and the relatively closed och and the climate environment in which evaporation is larger than precipitation form high salinity brine. This kind of high salt brine, which has a large proportion, permeates along the pore. Calcite carbonate formed by metasomatic alteration formed dolomite in Xisha island reef.
【作者單位】： 中國海洋大學海底科學與探測技術(shù)教育部重點實驗室海洋地球科學學院;國家海洋局北海環(huán)境監(jiān)測中心;中海石油(中國)有限公司湛江分公司;
【基金】：國家重大專項(2011ZX05025-002-03) 中國海洋石油總公司項目(CNOOC-2013-ZJ-01)
【分類號】：P618.13
【正文快照】： Lottermoser(1992)認為,從溶液中析出的礦物所具有的REE特征主要取決于流體中REE的地球化學特征,受礦物自身的晶體化學性質(zhì)影響有限。對白云巖而言,其REE特征是成巖流體與原巖(灰?guī)r)中REE重新分配、平衡的結(jié)果,記錄了成巖流體和成巖環(huán)境的相關(guān)信息。近年來,不少salinity seawa

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