Diagenetic Characteristics of Quaternary Reef-Carbonates from Well Xike-1, Xisha Islands, the South China Sea

In this study, petrographic and diagenetic characteristics of Quaternary reef-carbonates in well Xike-1 have been illuminated according to the observation analyses of polarizing microscope, alizarine red S and potassium ferricyanide composite staining, scanning electron microscope(SEM) and cathode luminescence. It is found that the diagenesis types include predominately weak compaction, neomorphism, micritization, dissolution and cementation. The diagenetic environments have been identified using the typical petrographic occurrences of cements and the cathode luminescence features. Among which, meniscus and pendant calcite indicate meteoric diagenetic environment and fibrous-needle aragonite indicates marine diagenetic environment. Diagenetic environments can be divided into 5 zones vertically including significant typical meteoric environment at depth of 0-27 m; the complex diagenetic environment of predominately meteoric and secondly marine at depth of 27-42 m; meteoric environment with weak influence of marine environment at depth of 42-105 m; relatively distinct evidences of both meteoric and marine environments at depth of 105-172 m; obvious marine environment at depth of 172.00-214.89 m.