Geologist sample enormous amounts of drill core worldwide every year, to research a variety of aspects of their content. Through these cores, we can better understand how minerals were formed and are distributed, the past and prevailing geological conditions and re-formations, climate conditions, etc. Every year millions of meters of drill core are recovered from more or less everywhere on this planet, and are subject to various types of analyses, aiming at improving our understanding of origin and metamorphic history. One of the most important aspects of such analyses is the study of the chemical element content and distribution in the minerals. There are few techniques, if any, that offer as much useful data as XRF scanning of cores, in as short time and with a minimum of sample preparation. From XRF scanning can not only knowledge about chemical elements be established, and conclusions about minerals be drawn, furthermore the elements give us a surprisingly large amount of information about geological history and origin through proxies based on the elements and how they are distributed in the drill cores.
Proxies that can be studied in sedimentary rock and soft sediments by XRF scanning include seasonal changes, oxic/anoxic conditions, amount of shell/foraminifera, grain size related effects, tefra, shallow water aragonite source, sediment grading, redox related diagenesis, biogenic silica, etc. in a past marine as well as limnological environment. Furthermore, they include provenance studies, laminations counting, reconstruction of past lake conductivity, and estimations of past productivity, weathering, cyclone frequency, leaching and erosion intensities. Usually, these proxies are based on ratios of elements.
This image shows a photo of a laminated shale sample from the Perm period, roughly 275 million years old. Overlaid in the center of the photo is a x-ray radiographic image. The two element profiles show the variation in concentration over the sample of Silica (yellow) and Strontium (blue). The elements were measured by scanning over the sample with a step size of 0.2 millimeter. A wide range of elements were measured at the same time (not shown). Good precision for Si, Sr and most other elements is reached when applying a time for analysis of 1-3 seconds per point. All data from Itrax corescanner. The sample was kindly provided by Dr. Michael Rhodes, University of Massachusetts, Amhearst.