Abstract: This paper presents a mineralogical and element geochemical study of carbonate rocks of the Upper Carboniferous Huanglong-Chuanshan Formation section from Tongling and Chaohu, Anhui Province. The results show that (1) the base of Huanglong Formation in Tongling is a set of dolostone containing framboidal pyrite; (2) the lower part of Huanglong Formation to the top of Chuanshan Formation are limestones; and (3) from bottom to top of section, mineral associations are dolomite+kaolinite +pyrite+quartz at the bottom of the Huanglong Formation → calcite+kaolinite+quartz (the middle and lower Huanglong Formation) → calcite+illite+quartz (the upper Huanglong Formation and the Chuanshan Formation), respectively. However the Huanglong-Chuanshan Formation in Chaohu are limestones composed of calcite with kaolinite and quartz, and the content of kaolinite tends to increase from the bottom of Huanglong Formation to the top of Chuanshan Formation. Also, carbonates of the Huanglong-Chuanshan Formation in Tongling (especially the dolomites at the bottom of the Huanglong Formation) show much higher V/Cr, Ni/Co, and V/Sc ratios, and Ce and Fe, Mn are uncorrelated while these parameters are positively correlated for Chaohu carbonates. Mineralogical and geochemical features suggest that carbonates at the bottom of the Huanglong Formation in Tongling were deposited in a relatively stable reducing environment, whereas carbonates in the middle and upper Huanglong Formation and Chuanshan Formation were deposited in a stable and weak oxidizing environment, and carbonates in Chaohu were formed in a more oxidizing and high-energy volatile environment. Combined with the previous studies, this study suggests that the existence of the ancient island in Tongling may be the main reason why the sedimentary environment of Tongling is different from that in Chaohu. Also, the sedimentary environment in Tongling area is favorable for the formation of colloform Pyrite.

Key words: the Upper Carboniferous, mineralogy, trace element, sedimentary environment, Tongling and Chaohu, Anhui