Economic Geology and Ore Controls of the Santa Rosa Mine—An Integrated Structural Analysis Approach
Notice bibliographique
Résumé
Abstract The Greenstone Resources Santa Rosa mine is located in central Panama about 200 km southwest of Panama City. The mine was the largest producer in Central America, but production was temporarily suspended in February 1999 with less than 5 million tonnes (Mt) of remaining reserves at a grade of 1.9 g/t Au ($300/oz). An integrated structural analysis was performed to determine the primary ore controls within the Santa Rosa deposit. The primary control is fault-related fracturing, particularly those fractures associated with the Santa Rosa fault. Although far less important, secondary controls relate to the permeability of the various pyroclastic, epiclastic, and intrusive host rocks. The methodology and results of the integrated structural analysis are described in the text to familiarize the reader with this technique. The application of the integrated structural analysis process was used to identify exploration characteristics that could be used for the field identification of exploration targets. The best set of exploration pathfinder elements were identified, visual field characteristics associated with ore mineralization were described, the optimum drill hole orientation was defined, and individual targets were identified and prioritized. Production issues were also addressed such as slope stability within the Alto de la Mina pit and grade control. Four separate deformation events were identified from a database collected from within the two pit areas and surrounding outcrop exposures. The earliest deformation event produced the Santa Rosa fault, and provided conduits for the intrusion of a porphyritic basalt stock and later latite dikes. Injection of the latite dikes adjacent to porous, wet volcaniclastic debris piles produced a series of funnel-shaped di-atreme pipes resulting from phreatomagmatic eruptions. Fragments of the latite are abundantly incorporated within the diatreme pipes Subsequent movement along the Santa Rosa fault produced additional steeply raking, strike-slip-controlled conduits for later mineralizing solutions during gangue and ore-metal deposition. The main quartz and sulfide deposition occurred during the second deformation event and the precious metals and associated pathfinder elements came into the system during the third deformation event. The fourth event was barren and offset the upper part of the orebody in the Alto de la Mina pit with reverse movement. Ore is typically found within the diatreme pipes or directly adjacent to the Santa Rosa fault plane in the basalt porphyry. With few exceptions ore is found within several tens of meters from the fault, but in one instance in the A zone of the Santa Rosa pit, ore extends to as much as 300 m from the main fault. This distal ore developed during the third deformation event where the fluids were conducted along an earlier reactivated set of northeast fractures created during the first deformation event. The ore produced here is lower grade than the ore adjacent to the main fault, presumably due to the enhanced fluid flow and resultant better availability of ore metals nearer the primary conduit. Strike-slip movement along the Santa Rosa fault dominated the kinematics of the first three deformation events. Inflections in the Santa Rosa fault conduit from its shear direction toward the extensional direction typify the ore zones in both pits. At these strike inflections, ore-related movement along the fault generates a zone of open conduits where associated extension fracture splits and cymoid loops enhance the permeability in the zones. The increased permeability along the fluid conduits controlled the amount of silica flooding. Gold in the form of electrum is often contained within very late crosscutting clear quartz stringers or adjacent to grains of pyrite. Where fluids deposited gold in nonsilicified sediments such as in the A zone orebody of the Santa Rosa pit, grades are significantly lower than the silicified, diatreme-hosted ore of the Alto de la Mina pit. The overall grade of the diatreme-hosted Alto de la Mina ore is higher than the volcaniclastic-hosted Santa Rosa ore at 2.0 g/t Au and 1.4 g/t Au, respectively.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 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) | 0,001 | 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 tête enseignante, 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 ».