Keywords: 
• laser particle sizer

Abstract: Calcareous clastics in the tropical beaches are important fractions, which differ from the silicic constituents in the physical character. The beach sediments are chosen to study on the influence of calcareous clastics on the particle grain size distribution through different pretreatment procedures. After dissolving the calcareous clastics by hydrochloric acid, the main part of particle size distribution curve will be more peaky and move to the fine end. Because the calcareous clastics cement some finer terrigenous particles in the bodies, the dissolution may make the cemented finer particles (4～9) mix with silicic clastics in sediments. After removing the finer particles (4～9), the parameters of grain size of the insoluble residues show good correlations with the parameters of mixing sediment. The correlation coefficients of mean, sorting, skewness are 0.934, 0.890, 0.813. For more than 50% samples, the insoluble silicic sands are more fine, better sorted and more finely skew than the total samples. Because of great variability in the shape and species of calcareous clastics in the beach sands, knowing of the species and content of calcareous clastics is necessary to understand the grainsize parameters and studying the dynamic environment of beaches similar to those around Tongguling. 