oa The Sabkhas Of Qatar: An Ideal Place To Study The Origin Of Dolomitic Hydrocarbon Reservoir Rocks

Many hydrocarbon reservoirs - in Qatar and worldwide - are constituted of dolomite. For this reason, the origin of this Ca-Mg carbonate mineral has been extensively studied by generations of geologists, with the goal of exploiting gas and oil from rock reservoirs in the most efficient way. However, despite more than two centuries of research, several fundamental questions regarding the origin of sedimentary dolomite remain without a convincing answer. Recent research conducted in the field of geobiology suggests that dolomite formation may be the result of a microbial process, that is, organic molecules that in natural environments are produced by microorganisms seem to play a key role for dolomite nucleation at low temperatures in many geological settings. However, this innovative hypothesis is far from being unanimously accepted by the scientific community, and many details on the exact mechanism through which microorganisms mediate dolomite formation are still to be fully understood. The aim of this contribution is to summarize the most recent scientific studies that support the microbial model for dolomite formation, providing examples from culture experiments conducted in the laboratory using artificial growth solutions and from modern dolomite forming environments, such as the hypersaline lagoons located in the State of Rio de Janeiro (Brazil), the sabkhas of Abu Dhabi (UAE), and the sabkhas of Dohat Faishakh and Khor Al-Adaid (Qatar). Furthermore, we will elaborate on why we consider the coastal sabkhas of Qatar to be among the most ideal places on Earth where it is possible to study microbe-mineral interactions in evaporitic environments. In fact, thanks to the distinctive geology that characterizes this region, it is possible to obtain samples documenting the progressive transformation of the living microbial mats that mediate dolomite formation and other authigenic minerals into a fully lithified sediment, which is analogous to dolomite formations constituting economically important gas/oil reservoir rocks. This approach will provide key insights to test whether dolomite present in ancient evaporitic sequences can be interpreted as a fully biological product associated with early diagenesis or whether most of the dolomite forms during later stage metamorphic/replacement events that are controlled by purely abiotic processes. Finally, considering not only the scientific importance but also the aesthetic beauty of the Qatari evaporitic environments, we will discuss the idea and the challenges of transforming selected areas of the modern sabkhas into geoparks - protected natural reserves that would be of interest for the local Qatari population, as well as for tourists visiting Qatar.