New British Columbia’s Regional Geochemical Survey Database
Alexei S. Rukhlov* and Mustafa Naziri
British Columbia Ministry of Energy and Mines, British Columbia Geological Survey, PO Box
9333 Stn Prov Govt, 1810 Blanshard Street, Victoria, British Columbia, V8W 9N3, Canada
* Corresponding author.
Abstract
The joint federal-provincial regional geochemical surveys (RGS) have been carried out in British
Columbia since 1976 as part of the National Geochemical Reconnaissance (NGR) program to aid
exploration and development of mineral resources. The British Columbia Geological Survey
maintains provincial geochemical databases capturing information from multi-media surveys. In
2014, we recompiled the RGS database from a total of 110 original sources, including both NGR
and RGS government reports and Geoscience BC releases (since 2006). The new database
format distinguishes the analytical determinations below the minimum detection limits (DL)
from the quantitative results. The results <DL are now stored as negative DL values instead of
arbitrary positive replacement values, so that the users of the RGS database will have a choice of
handling the <DL values as needed. The current version of the RGS database consists of five MS
Access tables capturing locations, field observations, analytical results and laboratories, and
geology underlying sample sites for a total of 64,828 stream-, lake- and moss-sediment (<0.18
mm fraction) and water samples. The analytical determinations include up to 63 analytes from
sediment samples and up to 78 analytes from water samples. These samples, collected at an
average density of about 1 site per 7–13 km2, provide representative geochemical data for the
catchment basin upstream from the sample site. The RGS currently covers approximately 80
percent of the province.
Key words: Regional geochemical survey (RGS) database, stream sediment, lake sediment,
moss mat-trapped drainage sediment, water geochemistry, British Columbia.
Introduction
Since 1976, the joint federal National Geochemical Reconnaissance (NGR) and provincial
Regional Geochemical Survey (RGS) programs have been carried out in British Columbia to aid
exploration and development of mineral resources (e.g., Lett, 2005; 2011). To provide
representative geochemical data for the catchment basin upstream, samples of fine-grained
(<0.18 mm) sediment and water are collected from drainages at an average density of about 1
site per 7–13 km2. These data include determinations of up to 63 analytes for sediments (Table 1)
and up to 78 analytes for water (Table 2), field observations, sample locations, and geology
underlying the sample sites. Sample collection, preparation, and analytical protocols are strictly
specified and carefully monitored to ensure consistent data regardless of the area, year of survey,
or analytical laboratory (Friske and Hornbrook, 1991).
Previous versions of RGS database had inconsistent format for capturing missing values (nulls)
and values below the minimum detection limit (DL), with some <DL values reported as negative
DL values and others set to positive 0.5DL values and to positive DL values even within a single
dataset. Consequently, the variable (up to an order of magnitude) censored values <DL (>80%
for some analytes) could not be distinguished from the quantitative determinations of different
vintage in the database, downgrading the original quality and limiting the interpretation of the
compiled geochemical data. We have addressed these issues in the new RGS database.
New RGS database standard
In 2014, we recompiled the RGS database from the original sources (Tables 3 and 4) into a MS
Access database, using a new data standard (Table 5). All values <DL are now stored as negative
DL values. For the original datasets that reported <DL values set as positive DL values that
could not be distinguished from the quantitative determinations equal to detection limits, the
latter were set to negative DL values. We believe that this approach does not cost any significant
data loss for the affected survey areas, since the results near the minimum detection limits are
typically up to an order of magnitude less precise than those at higher concentration levels. Due
to the imprecise determinations at concentration levels near the detection limits, the duplicate
results from these samples are commonly below the detection limits.
All missing values or nulls are now reported as blanks instead of using an arbitrary value of ‘-1’
in the previous database versions that conflicted with some of the <DL values given as negative
DL values. We have also standardized the field observations which are now explicit descriptions
instead of variable code values for different datasets. Where reported in the original source, the
predominant catchment geology is now captured in the RGS database, in addition to the
provincial digital geology (after Cui et al., 2013) underlying each sample site.
We checked each database table source-by-source and field-by-field to ensure that the new RGS
database is free of errors and omissions. Locations of individual samples are as given in the
original sources, except one sample site (two field duplicates), falling across the national border,
adjusted based on the field data and geology underlying the site. If not given in the original
source, the latitude and longitude decimal degree coordinates using NAD83 datum were
calculated from the original UTM coordinates. The current RGS database contains 64,828
samples from 110 original data sources that cover approximately 80 percent of the province
(Figure 1).
114O
114P
114I
104M
104N
104L
104K
104O
104J
104P
104I
094M
094N
094O
094L
094K
094J
Stream sediment - water
094P
Lake sediment - water
Moss sediment - water
094I
Spring sediment - water
104F
104C
103K
103F
103C
200 km
0
104G
104H
094E
094F
094G
094H
104B
104A
094D
094C
094B
094A
103O
103P
093M
093N
093O
093P
103J
103I
093L
093K
093J
093I
103G
103H
093E
093F
093G
093H
103B
103A
093D
093C
093B
093A
102O
102P
092M
092N
092O
092P
082M
102I
092L
092K
092J
092I
082L
092E
092F
092G
092H
092C
092B
083E
083D
082E
083C
082N
082K
082F
082O
082J
082G
Figure 1. RGS samples coverage.
MS Access Data Tables
Water_geochemistry: Water geochemistry by inductively coupled plasma mass spectrometry
(ICP-MS) and atomic emission spectrometry (ICP-ES), ion chromatography (chloride, fluoride,
nitrate, and sulphate), titration (total alkalinity), and reference electrode (total dissolved solids) 4332 samples.
Laboratories: List of original report designations (foreign database key) with information about
the format used for values below detection limits for different analytical methods and
laboratories that performed the preparation and analysis of the samples - 110 records.
Sediment_and_routine_water_master: Master table providing locations, sample medium, field
observations, and the complete analytical data for sediment samples by different methods and
routine RGS water samples (pH, conductivity, fluoride by specific ion electrode, uranium by
laser-induced fluorescence, and sulphate by turbidimetry in untreated water) - 64,828 samples.
Sediment_selective_extraction: Re-analysis of archived RGS sediment samples by nonstandard partial extraction using sodium acetate leaching with ICPM-ES finish - 1997 samples.
Geology_at_sample_site: Geology underlying sample site from the provincial digital geology
(after Cui et al., 2013) – 64,828 samples.
Metadata
Table 5 explains all of the column header codes and the codes used for recording stream, lake and moss
sample information.
Acknowledgements
We are grateful to Wayne Jackaman (Noble Exploration Services Ltd.) and Ray Lett (British Columbia
Geological Survey Emeritus Scientist) for useful discussions of the new RGS database standard and some
of the original data.
Selected references
Cui, Y., Katay, F., Nelson, J.L., Han, T., Desjardins, P.J., Sinclair, L., compilers, 2013. British
Columbia Digital Geology. British Columbia Ministry of Energy and Mines, British Columbia
Geological Survey, Open File 2013-4.
Friske, P.W.B., Hornbrook, E.H.W., 1991. Canada’s National Geochemical Reconnaissance
programme. Transactions of the Institution of Mining and Metallurgy, London, Section B 100,
47–56.
Lett, R.E., 2005. Regional Geochemical Survey Database on CD. British Columbia Ministry of Energy
and Mines, British Columbia Geological Survey GeoFile 2005-17.
Lett, R.E., 2011. Regional Geochemical Survey Database 2011. British Columbia Ministry of Energy and
Mines, British Columbia Geological Survey GeoFile 2011-7.