Trace element geochemistry of carbonates in the Jurassic Lusitanian Basin records mineral-fluid interactions

¹ Department of Geology, Faculty of Sciences, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal
² IDL – Instituto Dom Luíz, Faculty of Sciences University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal
³ HERCULES Lab, University of Évora, 7000 Évora, Portugal
⁴ Geosciences Department, University of Évora, 7000 Évora, Portugal

^* Corresponding author: mgoncalves@ciencias.ulisboa.pt

Abstract

Carbonate rocks in sedimentary basins are reactive and can record complex histories of events associated with fluid flow in these basins. These include processes of dolomitization and dedolomitization. In this work we provide some preliminary data where distinct calcite and dolomite generations in the Jurassic Lusitanian Basin were analysed by LA-ICP-MS for trace elements in order to characterize chemical signatures of fluid-mineral interaction. It was observed that different carbonate generations can preserve the range of certain trace metal concentrations, but later calcites have distinctly higher contents in REE, Th and U, and Ba. Dolomites also show distinct chemical signatures but lack of analytical and spatial resolution does not allow quantification of the precursor calcite relicts. However, these processes point to the action of basinal fluids triggered by distinct tectonic episodes and associated volcanic activity.