陈永权, 周新源. 塔里木盆地中寒武统—下奥陶统泥晶灰岩地球化学与古海洋学[J]. 海洋地质与第四纪地质, 2009, 29(1): 47-52. DOI: 10.3724/SP.J.1140.2009.01047
引用本文: 陈永权, 周新源. 塔里木盆地中寒武统—下奥陶统泥晶灰岩地球化学与古海洋学[J]. 海洋地质与第四纪地质, 2009, 29(1): 47-52. DOI: 10.3724/SP.J.1140.2009.01047
CHEN Yongquan, ZHOU Xinyuan. GEOCHEMICAL CHARACTERISTICS OF MIDDLE CAMBRIAN-EARLY ORDOVICIAN LIMESTONE AND PALEO-OCEAN RECONSTRUCTION BASED ON δ18OSMOW, 87Sr/86Sr AND RARE EARTH ELEMENTS, TARIM BASIN[J]. Marine Geology & Quaternary Geology, 2009, 29(1): 47-52. DOI: 10.3724/SP.J.1140.2009.01047
Citation: CHEN Yongquan, ZHOU Xinyuan. GEOCHEMICAL CHARACTERISTICS OF MIDDLE CAMBRIAN-EARLY ORDOVICIAN LIMESTONE AND PALEO-OCEAN RECONSTRUCTION BASED ON δ18OSMOW, 87Sr/86Sr AND RARE EARTH ELEMENTS, TARIM BASIN[J]. Marine Geology & Quaternary Geology, 2009, 29(1): 47-52. DOI: 10.3724/SP.J.1140.2009.01047

塔里木盆地中寒武统—下奥陶统泥晶灰岩地球化学与古海洋学

GEOCHEMICAL CHARACTERISTICS OF MIDDLE CAMBRIAN-EARLY ORDOVICIAN LIMESTONE AND PALEO-OCEAN RECONSTRUCTION BASED ON δ18OSMOW, 87Sr/86Sr AND RARE EARTH ELEMENTS, TARIM BASIN

  • 摘要: 塔里木盆地西部台地沉积区中寒武统-下奥陶统发育少量的泥晶灰岩,选择和4井中寒武统与塔中19井下奥陶统泥晶灰岩作为研究对象,旨在对中寒武世-早奥陶世古海水地球化学组成给予重建。地球化学分析结果表明,和4井泥晶灰岩MgO含量较高(2.76%~10.46%),表明和4井泥晶灰岩已被部分白云岩化,塔中19井泥晶灰岩较纯。两口探井泥晶灰岩δ18OPDB值变化在-8.7‰~-7.3‰之间,且δ18OPDB与MgO含量呈线性相关关系,趋势线在δ18O轴的截距为-8.6‰;泥晶灰岩样品的87Sr/86Sr值稳定,平均值为0.708 918;与和4井稀土元素总量(1.68~2.69)×10-6相比,塔中19井稀土元素含量较高,为(6.72~6.8)×10-6。δ18OPDB与MgO含量之间的线性相关关系,指示白云岩化作用可提高灰岩δ18O值,δ18O轴的截距为-8.6‰代表了灰岩原岩的氧同位素组成,根据同位素分馏规律可计算古海水δ18OSMOW值为-8.9‰。稳定的87Sr/86Sr值0.708 918代表中寒武纪-早奥陶世海水的87Sr/86Sr比值特征,与全球海洋87Sr/86Sr值演化线吻合。虽然各泥晶灰岩样品稀土元素总量不同,但皆表现为轻稀土元素富集的右倾模式,可认为是塔里木盆地中寒武世-早奥陶世海水的稀土元素特征。

     

    Abstract: In the middle Cambrian to lower Ordovician of Tarim Basin, occurs a little limestone, which is the studied object in this research, aimed at seawater geochemical reconstruction. Geochemical results showed that a linear correlation was demonstrated between the oxygen isotope values and the MgO% content, which indicates that dolomitization will lead to higher oxygen isotope values. The intercept of the line on the δ18O axis is -8.6‰, representing the oxygen isotope value of original limstones, and the oxygen isotope value of paleo-seawater can be calculated with value of -8.9‰. The average 87Sr/86Sr value is 0.708 918, which can be considered as the value of paleo-seawater. In the PAAS-normalized Rare Earth Elements diagram, LREE-enriched pattern can be seen in the studied limstones, which might represent the REE characteristics of paleo-seawater.

     

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