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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat: Speleothems are secondary mineral deposits whose growth in caves can be studied by mineralogical techniques. One of these techniques is the ontogeny of minerals, which is the study of individual crystals and their aggregates as physical bodies rather than as mineral species. Ontogeny of minerals as a scientific subject has been developed in Russia but is poorly understood in the West. In this lecture, I will introduce the basic
principles of this subject and explain a hierarchy scheme whereby mineral bodies can be studied as crystal individuals, aggregates of individuals, associations of aggregates (termed koras), and as sequences of koras (ensembles). Selenite needles are crystal individuals, most other speleothems are aggregates, while the association (kora) of calcite stalactites and stalagmites is known even to members of the public. Most cavers understand that crystallization in caves is a cyclic process, the product of any one cycle being termed (in ontogeny) an ensemble.
Individuals, aggregates, koras and ensembles are classed as "minor mineral bodies" because they can be studied by mineralogical rather than by petrographic techniques.
Ontogeny of minerals is not simply a new classification system for mineral bodies, it is a method by which past crystallization environments can be interpreted. The structure and texture of minor mineral bodies can be directly related to environmental factors at the time of their development. Speleothems are ideal subjects for this type of study, since there are few common mineral species in caves, yet there is a great variety in the forms that these minerals can take. ... |
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