Sediment budget of gold and magnetite and their distribution in stream sediment in lower Harris Creek, south-central British Columbia, Canada
Bibliographic record
Abstract
Although understanding the development of anomalous dispersion trains of gold in stream sediment is important to design and interpretation of exploration geochemical surveys, it has not been studied systematically with respect to variations in supply and transport of sediment. The problem is addressed by applying the sediment budget approach, with the following functional form: I(nput) - S(torage) = O(utput) Harris Creek, a gold-rich stream in south-central British Columbia was chosen as the study area. Primary sources of sediment are landslides in glacial deposits; secondary sources include bank erosion, erosion of sediment accumulated behind log jams, and sediment from tributary streams. Transport of bedload sediments within the Harris Creek drainage basin is strongly seasonal and dependent on the magnitude of the annual snowmelt flood. Field methods included collection of representative geochemical samples; direct field measurement of erosion; and collection of bedload samples using Helley-Smith samplers. Samples were analyzed in the laboratory to determine gold and magnetite. The data show that the supply of gold is discontinuous both spatially and temporally, with little or no gold being delivered to or transported out of Harris Creek during years with low or normal flood discharges (<20 m3/s). During years of large snow meltwater floods gold is transported for brief periods during very high discharge events. Coarse gold (<0.149>0.053 mm) is preferentially deposited in the voids at bar heads with exceptionally anomalous values at bar heads at breaks in slope. Conversely, fine gold (<0.053 mm) is swept in suspension over bar heads to deposit at bar tails but also has peak values at breaks in slope. Estimates of input and output of sediment, magnetite and gold show that gold is less readily mobilized and transported out of Harris Creek than magnetite and sediment. Through time, this has resulted in development of substantially greater concentrations of gold (up to twenty times) in stream sediment in Harris Creek than in the glacial deposits that are the primary sources of sediment. With respect to the anomaly dilution model in exploration geochemistry, the combined effect of accumulation of gold at breaks in slope and dilution by material derived from landslides create an apparent cut-off for gold anomalies a short distance downstream from a landslide.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".