Every core, in any science or engineering field, benefits from non-destructive analysis. Measured values may be used intrinsically, for their actual values (e.g. elemental data), or as proxies for changes in lithology or depositional environment (e.g. magnetic susceptibility or colour). The MSCL-XZ is a benchtop or small-footprint core logging system that provides a compact solution for split core non-destructive measurements, obtaining multiple data sets simultaneously. Unlike the MSCL-S, where the core moves past the sensors, the bench-top MSCL-XZ moves the sensors along the core (X-axis) while the sensors move up and down to contact the core surface (Z-axis). Split core sections enable sensors to be used that cannot operate through the plastic liner:
X-ray photons excite electrons in the sediment, releasing characteristic X-rays for each element which are collected through either an Olympus Delta handheld X-ray fluorescence (XRF) or an ultra-sensitive Geotek XRF spectrometer.
The selection of the XRF sensor determines whether a cabinet will be required. The Geotek ultra-sensitive XRF sensor requires the cabinet and is purpose-designed with a helium-flushed measurement cell to detect low energy elements such as Mg, Si and Al. The Olympus Delta handheld does not require a cabinet and can be detached from the instrument and used as a portable handheld if required. Elemental analyses can be used directly in environmental studies or indirectly as proxies for changes in mineralogy.
Reflectance spectra are collected in 39 spectral bands by a Minolta colour spectrophotometer to provide accurate colour data, including Munsell representations. The spectrophotometer is calibrated internally by using a white calibration reference tile and a zero-reflectance, “free-air” reading. True sediment or rock colour prior to core oxidation is a valuable correlation parameter for ore mineralogy, sedimentology, and climate research.
Visible and Near-Infrared Spectrometry
Geotek has integrated an ASD LabSpec Analyser into the MSCL-XZ, which includes a high intensity contact probe that comes into contact with the sample to be measured. The sample is illuminated by the integral halogen light source through a fibre optic link. The spectrometer returns data from 350-2500 nm which is collected and displayed in the MSCL software alongside any other data.
MAGNETIC SUSCEPTIBILITY MEASUREMENTS
Split-core inductive measurements of magnetic susceptibility are made with a Bartington MS2E “point” sensor that provides high down-core spatial resolutions. The active portion of the sensor is a narrow rectangle, oriented across the core, that has a field of influence of approximately 5mm.
The accuracy of the sensor is assessed using a custom check piece from the manufacturer. Magnetic susceptibility, a dimensionless number, is reported in SI units with an accuracy typically of ±4%. Changes in magnetic susceptibility correlate with changes in sedimentary provenance and/or diagenetic environment.
CORE PROCESSING SPEED
Data acquisition rates are highly dependent on the user setup and the sampling interval. XRF measurements are especially variable, with 15-120 second count times, depending on the accuracy desired. A typical scan with all sensors (30 second XRF data acquisition) at 2 cm intervals would enable about 50 m of core to be processed through a laboratory per day.
CORE ACCEPTED Length: up to 155 cm; Diameter: up to 15 cm
SENSOR MOTION Fully automated motion in the horizontal and vertical axes. Linear precision: 0.02 mm. All sensors are moved in unison and collect data in parallel
DATA OUTPUT Tab-deliminated ASCII files containing all measured parameters vs. depth in section and core: elemental concentrations, spectral reflectance data by wavelength band, magnetic susceptibility
DIMENSIONS Typical system L x W x H (cm): 230 x 35 x 130; Weight: approx. 70 kg