This section details research projects in carbonate geology that are currently underway at the University of Manchester, including opportunities to join research consortia.
PD3 (Prediction of Deposition, Deformation and Diagenesis in Carbonates) is a Joint Industry Project that combines expertise from leading carbonate geologists from Universities of Manchester, Bergen, Bristol and Liverpool. Phase I of PD3 is now complete and Phase II will launch in 2019. A summary of the project is provided below.
For more details please contact cathy.hollis@manchester.ac.uk
Carbonate sediments are principally deposited in marine basins, usually in clear, shallow water. Today, these conditions typically occur in sub-equatorial regions, such as the Caribbean, SE Asia and northern Australia. They accumulate away from the influence of large delta systems and often on discrete, topographically high areas, in shallow water. Through geological time, however, the size, morphology, latitudinal extent and architecture of carbonate platforms has varied in response to changes in tectonic plate configuration, regional tectonics, evolution and extinction, global climate and seawater chemistry.
Carbonate rocks are highly reactive, dissolving in a weak acid, such as when CO2 dissolves in water. This results in complex pore networks, often varying in size over several orders of magnitude within a single hand specimen. At the smallest scale, pores may be only a few nannometres in diameter, yet at their largest they comprise caverns and caves that form networks of 10s or even 100s of kilometres.
Dolomite (Ca.Mg.CO3) is a common carbonate mineral, which can replace limestone to form dolostone, a crystalline rock with a similar chemistry to limestone (CaCO3) but very different rock physical properties. The process of dolomitization, by which limestone is replaced by dolomite, has been studied for centuries, but there is still no cohesive understanding of how this occurs. It is particularly enigmatic because modern oceans are enriched in Mg, but dolomite does not precipitate directly from seawater in the same way that calcite does.
Carbonate sedimentary rocks are prone to alteration from immediately following deposition, e.g. on the seafloor, during burial and during uplift and emergence. Consequently, they can completely change their mineralogy (e.g. by dolomitization or silicification) or be highly altered as a result of cementation, compaction, dissolution and fracturing. The resultant pore network can host oil, gas or minerals, such as galena, fluorite and barite. Carbonate rocks can form important aquifers for freshwater and geothermal heat production, and the reaction of carbonate with CO2 is integral to predicting the behaviour of carbonate rocks during carbon sequestration.