Notice bibliographique
Résumé
ABSTRACT The “dolomite problem” is the product of two distinct observations. First, there are massive amounts of ancient marine limestone (CaCO3) deposits that have been replaced by the mineral dolomite (MgCa(CO3)2). However, recent (Holocene and Pleistocene) marine deposits contain relatively minuscule amounts of dolomite, although the occurrence of small quantities of dolomite is observed in many modern settings, from deep marine to supratidal. Second, low-temperature synthesis of dolomite in laboratory settings has been elusive, particularly in comparison to the ease with which common marine calcium carbonate minerals (aragonite and calcite) can be synthesized. Since low-temperature solid-state diffusion can be discounted as a method for Mg incorporation into calcium carbonate (as it operates on time scales too long to matter), the replacement of CaCO3 by dolomite is one of dissolution followed by precipitation. Therefore, an often overlooked but required factor in the replacement of limestone by dolomite is that of undersaturation regarding the original calcium carbonate mineral during replacement. Such conditions could conceivably be caused by rapid dolomite growth relative to aragonite and calcite dissolution–precipitation reactions, but laboratory studies, modern systems analyses, and observations of ancient deposits all point to this possibility being uncommon because dolomite growth is kinetically inhibited at low temperature. Pressure solution by force of dolomite crystallization is a second possible driver for CaCO3 undersaturation, but requires a confining stress most likely attained through burial. However, based on petrographic observations, significant amounts of ancient dolomite replaced limestone before burial (synsedimentary dolomite), and many such platforms have not suffered any significant burial. Because these possibilities of undersaturation caused by dolomite precipitation and crystal growth can be largely discounted, the undersaturation required for “dolomitization” to proceed is most likely to be externally forced. In modern natural systems, undersaturation and selective CaCO3 dissolution in marine porewaters is very common, even in warm-water environments, being forced by the breakdown of organic matter. Such dissolution is frequently attended, to varying degrees, by precipitation of a kinetically-less-favored but thermodynamically more stable phase of CaCO3. Laboratory studies as well as observations of modern systems show that when undersaturation is reached with respect to all common marine CaCO3 phases, dolomite assumes the role of this kinetically-less-favored precipitate. This degree of undersaturation is uncommon in modern shallow marine pore systems in warm-water settings, but it was more common during times of elevated atmospheric CO2, and ocean acidification. Furthermore, because oxidation of organic matter drives dolomite formation, near-surface organic-rich deposits such as the remains of microbial mat communities, were more predisposed to dolomite replacement in the acidified oceans of the ancient past relative to contemporaneous deposits that contained less organic matter. These observations lend to a more harmonious explanation for the abundance and occurrence of dolomite through time.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,006 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,003 |
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; les deux têtes enseignantes s’accordent sur ce qui est montré ici.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».