Early diagenetic features in Holocene travertine and tufa from a volcanic setting (Azuaje, Gran Canaria, Spain)

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The diagenesis of travertine and tufa is rarely considered an issue due to the common difficulty of distinguishing what is primary from secondary, as in most of cases these diagenetic changes occur very early. The main diagenetic features of travertine and tufa formed within a volcanic ravine in the north of Gran Canaria (Canary Islands, Spain) are cementation within pores and cavities, and of micropores (< 0.06 mm), micritization, aggrading neomorphism, aragonite-to-calcite transformation, and dissolution. One of the most striking features is cementation of micropores between fibrous crystals of shrubs, spherulites and crusts. Micropore cementation leads to a textural change of the primary aragonite and calcite fibres to a massive crystalline texture retaining the original fibres. Early cementation of micropores in fibrous textures can be significant in understanding their preservation in ancient shrubs and spherulites, such as those of Cretaceous Pre-salt reservoirs. These diagenetic changes are strongly controlled by their low porosity and permeability, whereas diagenesis occurred in a different way in the more porous and permeable textures. The diagenetic changes described here occurred very early in both tufa and travertine, being almost totally restricted to the period immediately after deposition.
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