The Mineralogy of the Siliceous Concretions

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 13712

Special Issue Editors

Department of Geology, University of Patras, 26504 Patras, Greece
Interests: sedimentary basin analysis; petroleum geology; depositional environments; submarine fans; fluvial deposits; carbonates diagenesis; carbonates deformation; sedimentology; sequence stratigraphy; seismic stratigraphy; geochemistry
Special Issues, Collections and Topics in MDPI journals
Department of Geology, University of Patras, 26504 Patras, Greece
Interests: mineralogy; petrology; geochemistry; archaeometry; X-ray diffraction; scanning electron microscopy; X-ray fluorescence
Special Issues, Collections and Topics in MDPI journals
Department of Geology, Saint Mary’s University, Halifax, NS B3H 3C3, Canada
Interests: igneous petrology and geochemistry; clastic sedimentary diagenesis and provenance; rock-forming minerals; detrital minerals and sediment provenance; diagenetic minerals in sandstones
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Siliceous concretions (chert) are a prominent component of diagenesis in biogenetic rocks. In biosiliceous oozes in the modern ocean, alteration of opaline silica to crystalline chert is unusual in rocks younger than Miocene. In limestones, timing of chert nodule formation has in some cases been determined from the presence of detrital chert pebbles eroded following basin inversion. The precursors of chert nodules in limestone can be initiated during very early burial diagenesis and are related to redox-controlled boundaries.

The scope of this Special Issue is to investigate the mineralogical and sedimentological characteristics of bedded and nodular chert in order to determine the conditions, processes, and timing of the formation of diagenetic silica minerals in different host rocks, of different ages and paleogeographic settings.

In some cases, the development of siliceous concretions appears linked to the formation of stylolites, which in turn relates to pathways for fluid flows. Changes in both porosity and permeability due to diagenetic processes are an important tool in hydrocarbon exploration and prospectivity.

This Special Issue welcomes high-impact original research and review papers that discuss the mineralogy of siliceous concretions, their relationship to sedimentary facies, the timing of different stages of chert formation, and basinal diagenetic processes, including the formation of stylolites and dissolution–reprecipitation reactions.

Prof. Dr. Avraam Zelilidis
Prof. Dr. Georgia Pe-Piper
Prof. Dr. Ioannis Iliopoulos
Guest Editors

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Keywords

  • chert
  • siliceous concretion
  • mineralogy
  • diagenesis
  • stylolite
  • fluid flow
  • dissolution-reprecipitation
  • stratigraphy
  • depositional facies
  • tectonic settings
  • chronology

Published Papers (5 papers)

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Research

17 pages, 6828 KiB  
Article
Characterization of Siliceous Nodules in Western Kefalonia Ιsland Greece: An Initial Approach to Their Formation and Diagenetic Characteristics
Minerals 2022, 12(1), 101; https://doi.org/10.3390/min12010101 - 15 Jan 2022
Cited by 2 | Viewed by 2232
Abstract
In this study, siliceous nodules from the world-famous Myrtos beach, as well as from Avithos beach, in the western flanks of Kefalonia Island in Greece are examined by means of petrographical, mineralogical, geochemical and micropaleontological methods. The objectives of this study are to [...] Read more.
In this study, siliceous nodules from the world-famous Myrtos beach, as well as from Avithos beach, in the western flanks of Kefalonia Island in Greece are examined by means of petrographical, mineralogical, geochemical and micropaleontological methods. The objectives of this study are to characterize the textural and compositional features of the nodules, with the aim to provide an initial interpretation of their origin and their diagenetic evolution. The studied siliceous nodules are hosted within Lower Cretaceous thin-bedded limestones at Myrtos and Upper Eocene limestones at Avithos. Nodules from both areas display a characteristic concentric texture at a macroscopic and microscopic scale. They both have a dense fine-grained siliceous sedimentary fabric, composed mainly of microcrystalline or cryptocrystalline quartz and moganite with common residual calcite in the case of Avithos. These results, and in particular the shape of the nodules, along the textural and compositional characteristics, indicate different conditions of formation in the two localities, both during the early epigenetic stages, as well as later during the diagenetic processes. Myrtos nodules originated from Si-precursors deposited in a pelagic environment, going through intense Si-replacement. Avithos nodules were deposited in a more proximal environment, being influenced by a less intense silicification. Nevertheless, the higher degree of recrystallization of Avithos samples indicates a syn- or post-diagenetic tectonic activity that resulted in the circulation of geothermal fluids. The conclusions drawn from this work demonstrate the usefulness of thorough studies of siliceous nodules in order to get a more comprehensive understanding of the initial depositional conditions, as well as diagenetic pathways and processes. Full article
(This article belongs to the Special Issue The Mineralogy of the Siliceous Concretions)
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18 pages, 5815 KiB  
Article
Origin of the Multiple-Sourced Cherts in Maokou Carbonates in Sichuan Basin, South China
Minerals 2021, 11(11), 1269; https://doi.org/10.3390/min11111269 - 15 Nov 2021
Cited by 7 | Viewed by 1614
Abstract
Cherts have been thought to originate from biosilicification, terrestrial inputs and hydrothermal activity. The study of cherts is helpful in understanding the paleo-ocean environment and tectonic–sedimentary processes. Large amounts of cherts occur widely in the Maokou Formation in the Sichuan Basin, which may [...] Read more.
Cherts have been thought to originate from biosilicification, terrestrial inputs and hydrothermal activity. The study of cherts is helpful in understanding the paleo-ocean environment and tectonic–sedimentary processes. Large amounts of cherts occur widely in the Maokou Formation in the Sichuan Basin, which may be largely connected to the Permian Chert Event (PCE). However, the source of silica and the formation process of cherts remain debated. Here, we analyze the petrographic and geochemical features of the cherts from the Guadalupian Maokou Formation (~268–259 Ma) in six sections in the Sichuan Basin. Two main types of cherts, nodular and bedded, are recognized in the Maokou Formation. The formation of nodular cherts was mainly affected by hydrothermal fluids, whereas the bedded cherts are mainly of biogenetic origin. The Emeishan large igneous province (ELIP) caused the activation of deep faults, accompanied by intense hydrothermal activities. Correspondingly, the cherts of significant hydrothermal origin developed near the active deep faults. The intensified hydrothermal activities may provide extra silica supplies and flourish the silica-secreting organisms by the associated volcanogenic upwellings that facilitated the enrichment of cherts. The study of Maokou cherts can help to record the volcanic- and silicon-related biological activities in the eastern Paleo-Tethys Ocean and can provide significant implications for chert enrichment in analogous settings. Full article
(This article belongs to the Special Issue The Mineralogy of the Siliceous Concretions)
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30 pages, 15961 KiB  
Article
Chemically Oscillating Reactions during the Diagenetic Formation of Ediacaran Siliceous and Carbonate Botryoids
Minerals 2021, 11(10), 1060; https://doi.org/10.3390/min11101060 - 28 Sep 2021
Cited by 9 | Viewed by 2740
Abstract
Chemically oscillating reactions are abiotic reactions that produce characteristic, periodic patterns during the oxidation of carboxylic acids. They have been proposed to occur during the early diagenesis of sediments that contain organic matter and to partly explain the patterns of some enigmatic spheroids [...] Read more.
Chemically oscillating reactions are abiotic reactions that produce characteristic, periodic patterns during the oxidation of carboxylic acids. They have been proposed to occur during the early diagenesis of sediments that contain organic matter and to partly explain the patterns of some enigmatic spheroids in malachite, phosphorite, jasper chert, and stromatolitic chert from the rock record. In this work, circularly concentric self-similar patterns are shown to form in new chemically oscillating reaction experiments with variable mixtures of carboxylic acids and colloidal silica. This is carried out to best simulate in vitro the diagenetic formation of botryoidal quartz and carbonate in two Ediacaran-age geological formations deposited after the Marinoan–Nantuo snowball Earth event in South China. Experiments performed with alkaline colloidal silica (pH of 12) show that this compound directly participates in pattern formation, whereas those with humic acid particles did not. These experiments are particularly noteworthy since they show that pattern formation is not inhibited by strong pH gradients, since the classical Belousov–Zhabotinsky reaction occurs in solution with a pH around 2. Our documentation of hundreds of classical Belousov–Zhabotinsky experiments yields a number of self-similar patterns akin to those in concretionary structures after the Marinoan–Nantuo snowball Earth event. Morphological, compositional, and size dimensional comparisons are thus established between patterns from these experiments and in botryoidal quartz and carbonate from the Doushantuo and Denying formations. Selected specimens exhibit circularly concentric layers and disseminations of organic matter in quartz and carbonate, which also occurs in association with sub-micron-size pyrite and sub-millimetre iron oxides within these patterns. X-ray absorption near edge structure (XANES) analyses of organic matter extracted from dolomite concretions in slightly younger, early Cambrian Niutitang Formation reveal the presence of carboxylic and N-bearing molecular functional groups. Such mineral assemblages, patterns, and compositions collectively suggest that diagenetic redox reactions take place during the abiotic decay of biomass, and that they involve Fe, sulphate, and organic matter, similarly to the pattern-forming experiments. It is concluded that chemically oscillating reactions are at least partly responsible for the formation of diagenetic siliceous spheroids and concretionary carbonate, which can relate to various other persistent problems in Earth and planetary sciences. Full article
(This article belongs to the Special Issue The Mineralogy of the Siliceous Concretions)
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28 pages, 50476 KiB  
Article
Comparison between Siliceous Concretions from the Ionian Basin and the Apulian Platform Margins (Pre-Apulian Zone), Western Greece: Implication of Differential Diagenesis on Nodules Evolution
Minerals 2021, 11(8), 890; https://doi.org/10.3390/min11080890 - 18 Aug 2021
Cited by 7 | Viewed by 2684
Abstract
Siliceous concretions (nodules), from two different geological settings—the Apulian platform margins in Kefalonia island, and the Ionian Basin in Ithaca, Atokos, and Kastos islands—have been studied both in the field and in the laboratory. Nodule cuttings are mainly characterized by the development of [...] Read more.
Siliceous concretions (nodules), from two different geological settings—the Apulian platform margins in Kefalonia island, and the Ionian Basin in Ithaca, Atokos, and Kastos islands—have been studied both in the field and in the laboratory. Nodule cuttings are mainly characterized by the development of a core, around which a ring (rim) has been formed. Mineralogical study, using X-ray powder diffraction (XRPD) analysis, showed that the rim is usually richer in moganite than the core. Homogeneous concretions, without discernible inner core and outer ring, were observed generally in both settings. Mineralogical analysis of the selected siliceous concretions from Kefalonia island showed the presence mostly of quartz and moganite, while calcite either was absent or participated in a few samples in minor/trace abundances. Moganite was generally abundant in all the samples from Kefalonia island. Concretions from the Ionian Basin showed a variation in the quartz, moganite, and calcite contents. Mineralogical differences were recognized both between the different studied geodynamic settings and internally in the same setting, but with different stages of development. The above-mentioned differential diagenesis on nodules evolution could be related to the presence and/or abundance of stylolites, later fluid flows, restrictions from one area to another due to synchronous fault activity, and the composition of substances dissolved in fluids. Moreover, the development of concretions produced secondary fractures in the surrounding area of the nodule-bearing rocks. Full article
(This article belongs to the Special Issue The Mineralogy of the Siliceous Concretions)
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16 pages, 9457 KiB  
Article
Evolution of Sedimentary Basins as Recorded in Silica Concretions: An Example from the Ionian Zone, Western Greece
Minerals 2021, 11(7), 763; https://doi.org/10.3390/min11070763 - 15 Jul 2021
Cited by 6 | Viewed by 2506
Abstract
Chert concretions in thick limestone successions preserve a more complete paragenetic sequence of diagenetic minerals than their host limestone and interbedded shale. The goal of this study was to test the possible presence of a high-temperature mineralising system in the Ionian basin of [...] Read more.
Chert concretions in thick limestone successions preserve a more complete paragenetic sequence of diagenetic minerals than their host limestone and interbedded shale. The goal of this study was to test the possible presence of a high-temperature mineralising system in the Ionian basin of western Greece. Upper Cretaceous chert nodules were sampled at Araxos, where rocks are highly faulted and uplifted by salt diapirism, and on Kastos Island, on the flanks of a regional anticline. Chert concretions have microporosity produced by recrystallisation of opal to quartz and fractures produced in the brittle chert during basin inversion. Diagenetic mineral textures were interpreted from backscattered electron images, and minerals were identified from their chemistry. Diagenetic minerals in pores and veins include sedimentary apatite (francolite), dolomite, Fe-chlorite, Fe oxide-hydroxide mixtures, sphalerite, barite and calcite. Sphalerite is restricted to Araxos, suggesting that inferred basinal fluids were hotter and more saline than at Kastos. At Araxos, the Fe oxide-hydroxide also includes minor Cu, Zn, and Ni. Whether the transported metals were derived from sub-salt clastic rocks and basement, or from enriched Mesozoic black shales, is unclear. The effectiveness of this novel approach to understanding fluid flow history in thick limestone successions is validated. Full article
(This article belongs to the Special Issue The Mineralogy of the Siliceous Concretions)
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