Provenance analysis aims to determine the source region (provenance) of a sediment sample. It is aimed to reconstruct the parent rock or rocks of sand bodies, the time of deposition of the sand, and, if possible, the climate conditions during the formation of the sediments.
Several laboratory techniques can be used to determine the Provenance of sediments: at GEUS we apply Laser-Ablation Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) analyses and automated Scanning Electron Microscopy (SEM) techniques.
The source rock can be 'reconstructed' from a comparison of zircon age distributions (or of other minerals suitable for dating like rutile or monazite) with age patterns of potential source rocks (geochronology) or by matching the heavy mineral suite in the sediment to that of the potential source rock regions (automated mineralogy).
Provenance analysis in Central East Greenland. (Click on the picture to see it in full size)
Provenance analysis is applied to obtain information regarding the shape and extension of reservoir rocks, which may contain oil or gas; or could be relevant for geothermal energy. When the source area for the sediment has been established, this knowledge can be used in basin analysis and modelling.
Provenance analysis can help to determine the directions of sediment transport, the slopes of palaeo-basins, to make geodynamic reconstructions of the history of orogens or sedimentary basins. Also sandstone diagenesis may be strongly depending of the original (detrital) composition, which is governed by the sediment source rocks and climate, as well as alteration during transport and sorting during deposition; automated mineralogy is therefore an important tool in diagenesis studies of reservoir rocks.
Apart from the determination of Provenance of sand bodies with age patterns and heavy mineral suite, the provenance of (geological) materials can also be determined with the same laboratory techniques. The LA-ICP-MS can be used to determine accurate trace element concentrations in various geological materials such as minerals (e.g. ruby corundum), ores, quartz feldspar, garnet, zircon and other mineral grains, as well as in materials such as mollusk shells and fish shales. The fingerprint of chemical characteristics in such materials can be used to determine the likely origin of a specific sample.
The Scanning Electron Microscope (SEM) can be applied to characterize sandstones, sand, ores, and non-geological materials like building materials, concrete or dust. Both the chemical properties (major and minor elements) and material properties (grain size, grain shape) are analysed by a combination technique of Energy Dispersive X-ray spectrometry (EDX) measurements and image analysis.
Two basic measurements can be performed semi-automatically at GEUS: Computer-controlled Scanning Electron Microscopy (CCSEM) on loose particulate material/grains and Automated Mineralogy analyses on entire thin sections or polished mounts relevant for mining and exploration, for geoscientific research, as well as investigations of reservoir rocks (oil & gas and geothermal energy).
Laser-Ablation Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) analyses are applied to determine the age of rock samples and geological processes. Analyses are routinely performed on zircon grains, a mineral that occurs in trace amounts in a broad variety of crystalline and sedimentary rocks. The age determination is based on the principles of radioactive decay of uranium (238U and 235U) to lead (206Pb and 207Pb), as zircon typically contains abundant uranium.
The standard applied method involves in situ measurement of mounted and polished grains mass spectrometry. Apart from zircon, the lab has experience with dating of baddeleyite, perovskite and rutile minerals that often occur in rock types that are barren of zircon, and we are looking to develop new dating techniques utilizing, for example, monazite and apatite.