Tellus geochemical sampling: collecting stream sediment, heavy mineral panned concentrate...

Stream Sediment Collection Process

Preparation of Equipment

• Before collecting stream sediment, wash the sieve set thoroughly in the stream to remove any previous materials.

• Inspect the upper 150 micron sieve for holes or tears and ensure it is clean by submerging it in water and shaking to dislodge particles.

• Clean the fibreglass sediment collection dish meticulously as it will collect fine fractions under 150 microns; it must be free from debris.

• Ensure all equipment, including gloves and funnels, are washed. Check that no screws on sieves are damaged or loose before use.

• Position the sediment collection dish close to the water course for stability, using cobbles if necessary.

Collecting Stream Sediment

• Select a suitable area for sample collection away from banks and bars; focus on active parts of the stream channel.

• Remove approximately 10 cm of oxidized top layer sediment before starting actual collection to avoid contamination.

• Tilt the shovel backward while collecting material to drain excess water; too much water can drown samples in sieves.

• Collect representative samples along a 20-meter stretch of stream bed, ensuring not to overload sieves which could cause damage.

• Use manageable amounts of material when sieving to prevent sagging or tearing of mesh.

Sieving Process

• Work comfortably while using circular motions with hands to pass material through the sieve; add water if needed for liberation of fine materials.

• Clean outer surfaces of sieves thoroughly before lifting them to avoid contaminating lower sections with coarse materials.

• Shake upper sieve gently after cleaning; use both up-and-down and side-to-side motions until no more material passes through mesh.

• Examine contents after rinsing upper sieve for lithologies present, noting size fractions and abundance while checking for contaminants like metal or plastic.

Sieve and Panning Process for Stream Sediment Collection

Cleaning the Sieve

• Ensure a spare glove is used to clean the sieve, removing persistent materials with your hand. After cleaning, wash your gloved hands thoroughly.

• Carefully shake the sieve to encourage material movement; adjust shaking intensity based on material type while avoiding eye contact with any particles. Great care should be taken to prevent coarse sediment from entering the collection dish.

Sieving Technique

• Emphasize cycles of rubbing and shaking through the fine mesh for effective material transfer. Continue until satisfied with the yield, using a field partner's assistance to monitor when no more material passes through.

• Once sieving is complete, remove the fine sieve and allow stream sediment in the collection dish to settle without contamination from foreign materials like vegetation or larger particles.

Transferring Material

• Transfer remaining material from the fine sieve into a black panning dish while ensuring distance from other samples to avoid contamination. Use water liberally to wash out all contents into the dish before starting panning.

• Begin panning by submerging the dish in water facing upstream; agitate gently so that lighter materials are washed away while denser materials sink to the bottom using specific motions (left-right and forwards-backwards).

Panning Process

• Perform an elliptical swirling action during panning, allowing water to carry away less dense materials while retaining heavier ones at the bottom of the pan. The goal is not just to isolate densest minerals but achieve a constant volume of heavy mineral concentrate over time without rushing this process.

• As you continue panning, let it float on water’s surface for easier handling and use ridges in the pan sides to trap denser minerals as finer materials are removed until reaching approximately 10 cm diameter of concentrated material at pan's bottom.

Inspecting and Bagging Samples

• Inspect your sample by swirling water gently in the pan; heavier grains will settle above lighter ones for examination using a hand lens—note color, luster, size, form, and identify minerals if necessary with provided guides before bagging up samples labeled ‘P’.

• While waiting for stream sediment sample settling, collect vegetation samples where live woody plants are present—preferably above waist height—to avoid flood zone sampling issues; ensure no diseased plants are included in sampling efforts.

Collecting Vegetation Samples

Stream Sediment Sample Collection Process

Initial Steps in Sample Collection

• Begin by collecting a fine fraction stream sediment sample, ensuring minimal disturbance to the sediment in its collection dish.

• Carefully decant water from the dish by tilting it slowly, allowing clearer water to pour out while keeping the fine sediment undisturbed.

• Observe and note the color and organic content of the stream sediment after decanting sufficient water, aiming for about two-thirds of the bag filled with sediment.

Preparing for Storage

• Re-wash the funnel to prevent contamination and prepare a pre-labelled brown Kraft® paper bag for sample transfer.

• Pour the homogenized sample into the funnel swiftly, using a clean finger to ensure complete transfer; additional water may be used if necessary.

Sealing and Transporting Samples

• After transferring, seal the bag securely by folding metal tabs and squeezing out excess air before tying it off.