The World’s Highest-Grade Cobalt Mineralization at Bou Azzer Associated With Gondwana Supercontinent Breakup, Serpentinite and Kellwasser Hydrocarbon Source Rocks
Bibliographic record
Abstract
Cobalt arsenide deposits associated with Neoproterozoic serpentinite in Morocco represent the highest-grade cobalt resource worldwide. Yet, genetic models for their origin remain controversial. We report here mineralogical and geochemical evidence for arsenide-calcite mineralization at Bou Azzer to constrain the temporal framework and identify the geodynamic trigger for mineralization mechanisms. To this end, radiometric ages for ore minerals are paramount for understanding the origin of the Bou Azzer cobalt arsenide deposit. New safflorite (CoAs 2 ) rhenium-osmium (Re-Os) ages are Late Devonian in age: 380.4 ± 2.9 and 373.4 ± 1.2 to 368.1 ± 5.0 million years ago (Ma) for coarse-grained and fine-grained safflorite, respectively. These dates overlap with the timing of break-up of the supercontinent Gondwana, and the building of an arch-and-basin geometry from northern Africa to Arabia. Our findings temporally and spatially contextualize previous knowledge of fluid chemistry and mineralization mechanisms involving a two-fluid mixing. Arsenide mineralization resulted from mixing of a methane-dominated fluid with highly saline basinal brines that leached Os ( 187 Os/ 188 Os initial = 0.120 ± 0.001), and by corollary cobalt, from Neoproterozoic serpentinite. Carbon and sulfur stable isotope data of ore-stage calcite and arsenides, respectively, show that hydrocarbons acted as the main reductant for mineralization. We speculate that the seawater-derived brines sank into the sedimentary basins adjacent to a carbonate platform with the Bou Azzer serpentinite in its basement in the Late Devonian. In the context of an enhanced geothermal gradient, such brines would have been involved in warm hydrothermal alteration of hydrocarbon source rocks of the local expression of the Kellwasser event in the geological record of present-day Morocco. This warm hydrothermal alteration of hydrocarbon source rocks may have taken place for coarse-grained safflorite mineralization (380.4 ± 2.9 Ma) shortly after ca. 382–381 Ma Lower Kellwasser horizons were deposited, or, for fine-grained safflorite mineralization (373.4 ± 1.2 to 368.1 ± 5.0 Ma) while the Upper Kellwasser horizons of present-day Morocco were being deposited.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".