Constraints on carbonate diagenetic fluid properties by microzone in situ analysis of carbon and oxygen isotopes: a case study of Cambrian-Ordovician, Tarim Basin

Abstract

As an important technological measure to uncover complex sedimentary-diagenetic process, microzone in situ geochemical analysis has drawn more and more attention along with improving analytical and test levels. According to the analysis of microzone in situ carbon and oxygen isotopes in combination with the data about carbon and oxygen isotopes acquired by conventional sample splitting methods, seawater cementation in syngenetic-burial stages, dissolution-infill by meteoric water in hypergenetic stage, and dolomitization fluid alternation-cementation infill in multiple stages were compared and discussed. The results demonstrated that the analysis of carbon and oxygen isotopes by microzone in situ sampling was favorable for revealing multi-stage and multi-period fluid property evolution in the process of cement formation. Carbon and oxygen isotopes of this cement type acquired by conventional sample splitting analysis might be mix values of multi-stage products. With respect to relatively single product (i.e. matrix components in carbonate rocks and calcite with meteoric water genesis), the analysis of carbon and oxygen isotopes by conventional sample splitting could basically meet study requirements. Microzone in situ sampling analysis on carbon and oxygen isotopes could provide a relatively "low cost and high accuracy" analytical measures, which has important meanings for precisely tracing diagenetic evolution of carbonate rocks.

Keywords

• carbon and oxygen isotopes
• seawater cementation
• meteoric water
• dolomitization
• carbonate rocks
• tarim basin