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It is a very common requirement to understand the composition of a rock for a number of purposes. This could be so that the minerals within it can be identified meaning that the type of rock itself can be determined. Alternatively, it could be to determine if there are elements of particular value or with specific health hazards within that rock. In any case, the first step is to determine what elements are within the rock and how they relate to each other.
Geologists are often presented with unknown rock samples and need to work out what is in them. This could be for the creation of a geological map, determining the history of an area. Or it could be to determine if elements such as arsenic are present when planning the remediation of a mining area.
Different minerals have different combinations of elements and in many cases it is possible to work out what those minerals are from their composition. This is often achieved in an SEM equipped with EDS by a range of approaches from individual measurements of points of interest to mapping or measuring compositions along a line.
Elemental maps over even very large areas are one of the best ways to understand geological samples in the SEM. By recording each element that is present at each point in a map, it is possible to quickly build up a picture of where there are consistent ratios of elements across a map. These consistent ratios represent minerals. These can be automatically identified to give an immediate understanding of what minerals are in a rock and their relative proportions – quickly starting the process of determining what the rock is.
Combining electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS) techniques for geological sample characterisation, helps to unlock even more information on the likely formation and history of the sample.
This application note examines how the AutoPhaseMap technique can be used to determine and characterise the phases present in an igneous rock.The results are compared to the phase mapping results calculated from an EBSD dataset collected simultaneously with the EDS acquisition, to validate the result of the AutoPhaseMap method.
This application note examines how AutoPhaseMap can be used to determine the modal percentages of different minerals in an igneous rock, and from this result classify its type.
This application note examines how the AutoPhaseMap technique can uncover previously missed minor phases - even when their constituent elements are not known to be present in advance
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