Stratigraphy, thickness, tectonic environment, and economic implications of the giant Suwar – Wadi Qutabah layered mafic complex in northwestern Yemen
Bibliographic record
Abstract
The Wadi Qutabah layered mafic intrusion in northwestern Yemen, considered part of a giant (>250 km2), Neoproterozoic (∼638.5 Ma) intrusion referred to as the Suwar – Wadi Qutabah Complex, has significant potential for economic platinum-group element and Ni–Cu–Co mineralization. A search for platinum-group element mineralization at Wadi Qutabah yielded cores from 14 drillholes along two east and west lines. Stratigraphically, they reveal ∼500 m of interlayered norites with subordinate gabbros, anorthosites, pyroxenites, and massive sulphide layers showing modal and cryptic layering that can be correlated between individual holes and between the east and west areas. Energy dispersive spectrometry major element analyses on mineral phases show gradual upward changes in plagioclase composition from An52 (lowest level drilled) to An44, and En61 to En57 in orthopyroxene, up to a distinctive, ilmenite-rich unit termed 5a (augite norite). Above 5a, minerals show a dramatic shift to more primitive An57 and En69 compositions. The gradual changes are typical of layered mafic intrusions and reflect progressive crystallization of magma upward. The dramatic changes, such as above 5a, are also common and reflect magma chamber recharge. In addition to the 500 m reported here, mineral exploration data from more-mafic rocks at Suwar suggest 400 m of layered rocks below those at Wadi Qutabah (total 900 m). A regression analysis plot of the cumulus mineral (plagioclase and orthopyroxene) compositional change versus thickness for seven well-known, giant, layered mafic intrusions suggests that the Suwar – Wadi Qutabah Complex is >2 km thick and one of the largest (thickness and area) intrusions on Earth. Comparison of the stratigraphy and mineral compositions at Wadi Qutabah with intrusions bearing PGE deposits suggests prospective areas for mineral exploration to the north and south of the study area. Recent reviews identify many similar-aged, mafic–ultramafic intrusive complexes across the Arabian–Nubian Shield. The large size of the Suwar – Wadi Qutabah Complex, its noritic composition, and subcontinental lithospheric mantle signature are characteristics typical of mafic rocks formed in extension-related, continental rift settings. Thus, the Suwar – Wadi Qutabah Complex may be part of a previously unrecognized large igneous province associated with a late Proterozoic magmatic event and preserved in what is today, the Arabian Shield.
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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 | 0.001 | 0.002 |
| 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) | 0.002 | 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".