The mobility of water makes it an excellent exploration tool.
As waters interact with rocks, major changes occur in the chemical composition. These changes can occur via surface water-rock interactions over short periods or via ancient groundwaters that have interacted with rock for at several thousands of years (or more). Like other geochemical media such as soils and vegetation, the chemical variations in water samples across a survey can provide exploration vectors. However, waters have the additional benefit that they can be highly mobile and often geochemical pathfinders can be detected significant distances down-gradient from the source of the anomalous geochemistry. For example, the Piper Diagram below shows that waters that are dominantly Ca-SO4 have high Zn content and are related to the interaction of groundwater with sphalerite. As the Zn concentrations decrease, there is also a change in the water towards an K+Na-HCO3 type. This trend suggests that those samples are from locations increasingly more distal to mineralization.
The sensitivity of the ICP-Mass Spectrometers at BVM provides the ultra-low detection limits required to determine background and anomalous concentrations of important pathfinder elements for a several deposit styles.
Samples received by BVM are run as received. In order to ensure the most accurate readings of samples submitted it is recommended that the following handling procedures be considered when planning your sampling and choosing a method of delivery for samples.
In order to ensure a representative sample, samples should be collected in pre-cleaned, HDPE plastic bottles that have been rinsed with sample water three times prior to use. Keep in mind that if dissolved metals are required the sample should be filtered through a 0.45 um filter prior to acidification.
If anions, pH alkalinity or conductivity are required samples should be kept refrigerated. For cation analysis samples should be acidified to pH <2 as soon as possible after collection with environmental grade (ultra pure) nitric acid due to the problems of absorption or precipitation of cations to the bottle walls. Pre-acidifying sample bottles before a sampling program is not recommended as it can result in leaching of metals from the bottle material. Unacidified filtered samples can be acidified at the laboratory but they must sit for seven days to dissolve any absorbed or precipitated metals.
Important: Acidified water samples can not be analysed for anions and a second unacidified sample should be sent if required.
The following table summarizes the BC Ministry of Water, Land and Air Protection’s recommendations for sample preservation and holding times which should be considered when planning your sampling and choosing a method of delivery for samples.
|pH||Store cool 4°C||72 hours|
|Conductivity||Store cool 4°C||28 days|
|Alkalinity||Store cool 4°C||72 hours|
|Anions||Store cool 4°C||28 days|
|Metals||Nitric acid to pH<2||Metal dependent|