Applied Mineral Exploration
Discussion and research relevant to mineral
exploration. The BGS model 216 decrepitometer
Improved electronics, 2019
The new model 216 decrepitometer is physically similar to the model 205 decrepitometer and uses the
same furnace and operational computer and software but has updated
and improved electronics which gives higher sensitivity and more
convenient cable connections. As with the model 205, model 216
uses a standard single-board Linux computer running the Debian
Ubuntu operating system. The decrepitometer operation software is
unchanged with a full graphical interface, operating in the
Xwindows environment. The temperature and counts are monitored and
shown on screen during the analysis, and simultaneously plotted on
screen as the temperature rises. The data is saved to a file upon
completion, and the graphical plot can also be printed if required
and easily regenerated from the saved data file for additional
review.
As for the model 205, the model 216
provides the complete computer as part of the instrument. It can
be operated stand-alone with the addition of a monitor, keyboard
and mouse, or operated remotely across a network using the
included wired lan connector. The computer and its interface
electronics is in a slightly larger 15 * 13 * 7 cm enclosure
and the power supply unit is a little smaller.
Operation is the same as for the model 205 decrepitometer. The
weighed sample is added to the sample tube, which is inserted into
the furnace and the door of the enclosure is closed. The sample
information and control settings are entered into the control
window and the "GO" button is clicked. The entire analysis is then
completed automatically without further user intervention. At the
end temperature, the furnace is turned off and the control window
re-appears to allow analysis of additional samples. The plot
remains in view, with additional plot windows being created for
additional samples. It is necessary to allow the furnace to cool
before analysing subsequent samples.
Samples of 0.5gm are normally used while samples as small as 0.2
gm or up to 2 gm can be analysed according to the fluid inclusion
abundance in the sample. The heating rate used is almost always
20ºC per minute, but the instrument can also be operated at 10ºC
or 40ºC per minute. Analyses are usually performed on quartz
samples, but other minerals containing fluid inclusions can also
be used, such as carbonates, feldspars and opaque minerals such as
haematite and magnetite. Sulphides can also be analysed, but they
can be corrosive and this reduces the life of the temperature
sensor. Quartz samples are usually analysed up to 620ºC because
there is no activity above the alpha to beta phase transition at
573ºC, however the instrument can be used for analyses up to
800ºC.
The system can be installed in a normal quiet laboratory location
as ambient sounds are suppressed. However loud sounds or vibration
can interfere and should be avoided. Because it can be operated
remotely across a network the room can be unoccupied during the
analysis.
Auxiliary software is now available to simplify plotting of
the previously saved data files. These saved data files can still
be plotted using Gnuplot which is very comprehensive but driven
from the command line. The new utility software still uses Gnuplot
but is specifically designed to plot decrepigram files and has a
fully graphical interface. The following image is a screenshot of
the plotting software.
Image of the plotting software for decrepigram files.
Files for plotting are selected in the "select files" window shown here in the lower right. Multiple files or groups can be chosen and added to the main listing in the left window. Files do not all need to be in the same directory. The files to be plotted on a single graph are then selected in the left window and multiple files can be plotted together in a single plot window as shown in the upper right. Additional selections and plots can be prepared as all the plot windows remain visible to facilitate interpretation. The plots can also be saved as png graphics files for addition to presentations or printing etc.