激光-筛分联合法粒度分析结果的表达及粒度端元的沉积动力学意义

Expression of particle size analysis results by laser-sieving combined method and the sedimentary dynamic significance of grain size endmembers

中文关键词:  粒度分析  激光-筛分联合法  粒度参数  端元分解  舟山群岛  潮间带

英文关键词:laser-sieving combined method  particle size analysis  particle size parameters  endmember decomposition  Zhoushan Archipelago  intertidal zone

中文摘要:

      河口海岸沉积动力环境复杂，沉积物粗细组分皆有。对于粗细混杂（同时含有砂砾质成分和泥质成分）的沉积物样品，单一的粒度分析方法不能覆盖整个粒度分布范围，常采用激光-筛分联合法进行粒度分析。由于两种方法的分析原理不同，细部的激光法结果经常出现与粗部的筛分结果部分重合现象，这给整个样品的粒度分布计算带来挑战。石油天然气行业标准SY/T 5434-2018《碎屑岩粒度分析方法》对此问题给出了新的解决方案，但是只有文字描述，没有可操作的计算方法。本研究根据SY/T 5434-2018提出的方案，推算出激光-筛分联合法粒度分析结果的修正计算公式。以浙江舟山群岛潮间带197个粗细混杂样品为例，采用激光-筛分联合法进行了粒度分析，分别采用直接拼接算法及SY/T 5434-2018算法计算了粒度分布，在此基础上对两套算法所得组分含量和粒度参数进行了比较。结果表明，SY/T 5434-2018算法相较于直接拼接算法，扩大了粗颗粒的体积百分比，减少了细颗粒的体积百分比。两种算法得到的组分含量具有显著的线性相关关系，且砾、砂、粉砂、黏土等组分含量的差异从粗到细依次减少。用两种算法的结果分别计算粒度参数，同样具有显著的线性相关关系，且平均粒径、分选系数、偏度与峰态等粒度参数的差异渐次减小。两种算法得到的组分数据的相似度整体优于粒度参数的相似度，均具有高度一致性，可根据工作需求选择适合的算法，无需对两种算法之间的误差再做验证。借助粒度端元分解模型，将舟山潮间带的沉积物划分出不同的粒度端元，其中泥质端元主要是长江泥沙向浙闽沿岸输送的产物；而砾和砂的成分，多是当地物源或当地波浪分选的结果。

英文摘要:

      The estuarine and coastal sedimentary dynamic environment is complex, and the sediments have both coarse and fine components. For sediment samples with mixed coarseness and fineness (containing both sand-gravel and argillaceous components), a single particle size analysis method cannot cover the entire particle size distribution range, and the laser-sieving combined method is often used for particle size analysis. Due to the different analysis principles of the two methods, the results of the laser method for the fine parts often overlap with the sieving results of the coarse parts, which brings challenges to the calculation of the particle size distribution of the entire sample. The petroleum and natural gas industry standard ' Analysis method for particle size of clastic rocks ' (SY/T 5434-2018-2018) provides a new solution to this problem, but there is only text description and no operational calculation method. In this study, according to the scheme proposed by SY/T 5434-2018-2018, the revised calculation formula of the particle size analysis results of the laser-sieving combined method was calculated. Taking 197 coarse and fine mixed samples in the intertidal zone of Zhoushan Archipelago in Zhejiang Province as an example, the particle size analysis was carried out by the laser-sieving combined method, and the particle size distribution was calculated by the direct splicing algorithm and the SY/T 5434-2018 algorithm respectively. On this basis, the component content and particle size parameters obtained by the two algorithms were compared. The results show that compared with the direct splicing algorithm, the SY/T 5434-2018 algorithm enlarges the volume percentage of coarse particles and reduces the volume percentage of fine particles. The components content obtained by the two algorithms has a significant linear correlation, and the difference in the content of gravel, sand, silt and clay decreases from coarse to fine. The particle size parameters were calculated with the results of the two algorithms, which also had a significant linear correlation, and the difference in particle size parameters such as average particle size, sorting coefficient, skewness and kurtosis gradually decreased. The similarity of the component data obtained by the two algorithms is generally better than the similarity of the particle size parameters, but both of them are highly consistent. The suitable algorithm can be selected according to the work demand, and the error between the two algorithms need not be verified again. With the aid of the grain-size endmember decomposition model, the sediments in the intertidal zone of Zhoushan are divided into different grain-size endmembers, in which the argillaceous endmember is mainly the product of the Yangtze River sediment transportation to the coast of Zhejiang and Fujian. The composition of gravel and sand is mostly the result of local provenance or local wave sorting.