Analysing the mobility of metals and Rare Earth Elements during deformation in calcite within the Flamborough Head Fault Zone

Project Description

Dating faults and fractures can provide critical information on when faults moved and when and how fluid flowed through them. This is often critical information for the energy industry from determining maturity of many different types of reservoirs. Currently, this method has been used by the hydrocarbon industry over the last few years but it is also a useful technique for establishing geothermal potential. Heavy metals such as uranium (U) and lead (Pb) are increasingly used to date carbonate material within the fracture/fault fill. Rare Earth Element abundances are used to complement these U-Pb dates, providing valuable insight to the source of these fluids. Understanding the distribution of these metals within carbonates is vital to our interpretation of data produced. To date, our understanding of how these elements get into calcite, where they are accommodated into the crystal structure and how they respond to deformation or remobilisation is very poorly understood, meaning our interpretations of dates obtained are based on a series of assumptions and are lacking key information.

The Flamborough Head Fault Zone provides an excellent opportunity to study the behaviour of these elements within a variety of natural calcite, some of which is pristine, some deformed and some affected by fluids. The fault zone is exposed in the Burnham and Flamborough chalk formations in Selwicks Bay. The dominant deformation mechanisms within the fault zone are brecciation/ cataclasis and diffusive mass transfer (pressure-solution). Using laser ablation ICPMS we aim to date the calcite within the faults by U-Pb geochronology alongside analysing the REE abundances, and compare this data to the surrounding un-deformed chalks. This will allow us to gain insight into how these elements move through the Earth’s shallow crust from precipitation to deformation to solution to re-precipitation. This insight will potentially allow for improved understanding and interpretation all U-Pb calcite dates obtained from any geological setting.