Geochemical characteristics and sedimentary environments of the Zhujiang Formation in well HZ21 at Huizhou depression

This study discussed the sedimentary geochemistry characteristics and the palaeosedimentary environmental significance of the Zhujiang Formation in well HZ21 at Huizhou depression, Pearl River Mouth basin, on the basis of geochemical analyses of 21 rock samples. The results indicated:Al₂O₃、Fe₂O₃、K₂O、TiO₂、V、Cr and Rb remarkably were positively correlated with each other; SiO₂ was apparently negatively correlated with Al₂O₃、Fe₂O₃ and TiO₂,and weakly negatively correlated with K₂O; Sr and CaO positively correlated with each other; P₂O₅ positively correlated with Al₂O₃、Fe₂O₃、K₂O and TiO₂, and negatively correlated with SiO₂, and weakly negatively correlated with CaO. The analytic result of the value of 10³(Sr/Ca) and V/Cr revealed that the depth of sedimentary water increased from bottom to top in the Zhujiang Formation of well HZ21, and the variation regularities were consistent with the conclusions of sedimentary facies. The analytic result of the value of 10² (MgO/Al₂O₃) and V/Cr revealed that the salinity was similar from the bottom to the top of Zhujiang Formation, but decreased slightly in the top of Zhujiang Formation. Based on the characters of Rb/Sr and MgO/CaO, NSQ1 and NSQ2 were deposited in cool-dry climate condition, NSQ3 and NSQ4 were deposited in warm-wet climate condition. In summary, the geochemical characteristics and the sedimentary environment are closely correlated, and the geochemical characteristics can be regarded as a mark in the sedimentary facies recognition.