Structural Modification of the Komatiite-Associated Harmony Nickel Sulfide Deposit, Leinster, Western Australia
Notice bibliographique
Résumé
The Harmony nickel sulfide deposit (3.2 Mt of ore) is situated along the eastern margin of the Agnew-Wiluna greenstone belt, Eastern Goldfields, Western Australia. The deposit occurs 2 km north of the larger Rocky's Reward (15.9 Mt) and Perseverance (50.7 Mt) deposits. The mine stratigraphy trends north-northwest-south-southeast, dips moderately (30 degrees-80 degrees) to the west, is overturned; and metamorphosed to middle-amphibolite facies grades (about 550 degrees C, 3 kbars). Stratigraphic footwall units to the west of the nickel-bearing komatiite include ca. 2720 to 2725 Ma (volcano-) sedimentary rocks and rhyodacite volcanic and volcaniclastic units. Hanging-wall units comprise mainly reworked sedimentary or volcaniclastic rocks interlayered with at least two barren spinifex-textured komatiite units exposed in the mine area. Exhalative pyrite-rich pelitic units and thin amphibolite units are locally present in the footwall and hanging wall. The nickeliferous komatiite is thickest in the center of the deposit and thins to the north, south, and at depth. Although massive sulfides and minor disseminated sulfides are mainly located along the sheared western footwall contact, minor massive sulfides occur throughout the komatiite and country rock in fold hinges, boudin neck areas, brittle-ductile shear zones, piercement cusps, piercement veins, and brittle faults. Footwall and hanging-wall units have a strong composite fabric defined by compositional layering and several subparallel axial planar foliations. East-west shortening resulted in the folding of the composite fabric to form abundant north-northwest-trending, tight, asymmetric, moderately (20 degrees-40 degrees) N- and S-plunging folds. The asymmetric folds thicken the koniatiite and orebodies in the center of the pit and control deposit-scale orebody plunge directions. The attenuated north-northwest-trending komatiite fold limbs are boudinaged and concentrate pods of massive sulfides in boudin neck positions. Relaxation in horizontal shortening coincided with open recumbent folding of the steeply dipping limbs of earlier upright asymmetric folds. A resumption of east-west shortening in a brittle stress regime resulted in the remobilization of massive sulfides into east-west-trending brittle faults. The concentration of massive sulfides in brittle-ductile to brittle structures indicates that massive sulfide remobilization spanned a diverse range of deformation and metamorphic conditions. The present geometry and distribution of stratigraphy and orebodies at Harmony reflect a complex interplay of primary magmatic and secondary overprinting processes. Remobilized massive sulfide orebodies are an important exploration target in other deformed and metamorphosed terranes that host primary Ni-Cu-(PGE) deposits. Although footwall units are the preferential host to remobilized massive sulfide shoots, massive sulfides are commonly remobilized within shear zones and faults zones and hosted by banging-wall units up to 50 m from their primary foot-wall position. In cases of folding, orebodies tend to be elongate parallel to the plunge direction of fold axes or mineral stretching lineation,and potential exploration targets occur along the trend of known folded ore shoots and more specifically along the plunge line of such shoots.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».