利用计算机断层扫描技术反演沉积物粒级组成--以黄河水下三角洲现代沉积为例

INVERSION OF SEDIMENT GRIAN SIZE COMPOSITION WITH X-RAY COMPUTED TOMOGRAPHY METHOD--AN EXAMPLE OF MODERN SEDIMENTATION IN THE SUBAQUEOUS HUANGHE(YELLOW)RIVER DELTA

计算机断层扫描技术(computed tomography,CT)可对沉积物岩芯进行高分辨率、无损分析,探索CT数据(即CT值)与沉积物粒度的关系可以实现岩芯沉积物属性的快速、连续获取,有助于对岩芯沉积特征和沉积过程的全面了解。基于采自黄河水下三角洲的多根岩芯,利用CT技术对岩芯进行扫描获取CT值,同时对岩芯进行高分辨沉积物粒度分析,探讨CT值与沉积物粒级组成的联系。研究表明,黄河水下三角洲沉积物以粉砂为主,CT值主要分布于700~1000 HU之间;沉积物粒度与CT值间存在显著的非线性正相关,即当沉积物粒度变大时CT值随之升高,并据此构建了沉积物粒度与CT值之间的关系式;沉积物粒级中的砂、粉砂、黏土粒级与CT值区间1200~1500 HU、800~1200 HU、600~800 HU亦存在良好的对应关系,并可以通过CT值区间估算粒级含量。经过实际应用验证,通过CT扫描反演沉积物岩芯的粒级组成是有效的,该方法也可以用于其他海域沉积物粒级组成的反演。

X-ray computed tomography(CT)allows for high-resolution and nondestructive analysis of sediment cores,and for exploring the relationship between CT data(i.e.,the CT value)and sediment grain size to achieve rapid,continuous acquisition of sediment properties from cores,and to enhance comprehensive understanding of core depositional processes.Based on multiple cores taken from the subaqueous Huanghe(Yellow)River Delta,CT scanning was performed to obtain the CT values,and high-resolution grain size was analyzed to quantify the relationship between CT value and grain size compositions.Results suggest that the sediments in the subaqueous delta are mainly silt,and the CT value is mainly distributed between 700 and 1000 HU.A significant nonlinear positive correlation between mean grain size and CT value was found,and the relationship equation between mean grain size and the CT value was constructed.In addition,a good correspondence between sand,silt,clay contents in the sediments and the CT intervals of 1200~1500 HU,800~1200 HU,600~800 HU was revealed,from which the grain size fractions could be estimated.The application verified that the inversion of grain size compositions and mean grain size of sediment cores with CT scanning CT value was effective.Therefore,this method could be used for the inversion of grain size composition of sediments in other marine areas.