Early diagenetic celestite replacement of demosponges in Upper Cretaceous (Campanian–Maastrichtian) chalk, Stevns, Denmark

Madsen, Heine Buus; Stemmerik, Lars

doi:10.1130/g25254a.1

Cited by 12 publications

(5 citation statements)

References 18 publications

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“…On the other hand, large deposits of Sr have been recognized in Stevns‐1: celestite nodules (SrSO 4 ), in the form of recrystallized sponges, are common in intervals with increased sedimentation rates. The faster sedimentation created an anoxic environment that favoured the capture of Sr and the precipitation of celestite (Madsen & Stemmerik, 2009). This interpretation is in line with the model proposed here, because the Sr might be trapped from the aragonite dissolution and mineralized only when the connection with the water column was lost and/or reduced.…”

Section: Discussionmentioning

confidence: 99%

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

et al. 2020

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Chalk is usually thought to be a homogeneous sediment with a relatively simple early diagenetic history. Here, clumped isotope analyses of samples from a core of Campanian Maastrichtian chalk are presented, indicating that material smaller than 5 µm has a different origin than the coccolith-dominated coarser fraction. The smallest size fraction (1 to 5 µm) of chalk is dominated by calcite particles without a distinct morphology (micarbs). Clumped isotope data of the micarbs reveals formation temperatures of 14 to 18°C which is 8 to 10°C colder than those derived from coeval coccoliths. The micarbs are interpreted as the product of calcite neoformation, precipitated in the uppermost part of the sediment column (100 metres below sea floor) and linked to early dissolution of aragonitic fossils. These findings prove that early cements can be an abundant component in chalk, and thus challenge the common notion that chalk is always largely composed of calcareous nannofossils, and differs only in terms of minor constituents and degree of lithification.

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Section: Discussionmentioning

confidence: 99%

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

et al. 2020

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“…1) (Madsen and Stemmerik 2009). Above this, a 100-mthick lower Maastrichtian interval is composed of almost pure chalk.…”

Section: Geological Settingmentioning

confidence: 93%

Diagenesis of Flint and Porcellanite in the Maastrichtian Chalk at Stevns Klint, Denmark

Madsen

Stemmerik

2010

Journal of Sedimentary Research

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Flint is common in many successions, but since the nodules can be the result of a series of replacement and void filling processes, their origin and broader paleo-oceanographic significance can remain enigmatic. This study addresses the origin of flint, in the Campanian-Maastrichtian chalk of Denmark using the 450-m-long Stevns-1 core as a natural laboratory.Four types of siliceous nodules occur in the core: porcellanite, white flint, white flint with a core of dark flint, and dark flint. All nodules consist mainly of microquartz with subordinate lutecite, spherulitic chalcedony, megaquartz, and dolomite. The lutecite replaces macrofossil fragments, mainly bryozoans and shells, microquartz replaces coccoliths, and the chalcedony and megaquartz are pore-filling. The preservation of the external shape of bryozoans, shells, and coccoliths suggest that siliceous nodules were formed early by a one-by-one volume replacement of chalk. Values of d 18 O smow of microquartz and lutecite around 33% indicate temperatures of 15-17uC at the time of precipitation; in contrast, the d 18 O smow values of megaquartz indicate precipitation at temperatures up to 48uC. The occurrence of chalcedony together with more stable and ordered megaquartz in irregular voids indicates that silica gel and/or opal-CT transformed to the a-quartz phases, microquartz, lutecite, chalcedony, and megaquartz, through the dissolution-precipitation process (Ostwald ripening).These results motivate a conceptual model in which the replacement process was initiated by microbial decomposition of organic matter and took place during periods of low rate of, or even stopped, sedimentation which fixed the redox boundary and the microbial metabolic zones at a specific depth below the sea floor. Biogenic opal-A incorporated in the sediment column below the sea floor was dissolved and precipitated at the redox boundary as silica gel and/or opal-CT, possibly aided by sulfideoxidizing bacteria. During burial, the dissolution-precipitation process transformed the silica gel and opal-CT to the a-quartz phases.The results of this study indicate that precipitation of the flint precursor can be controlled by a combination of an abundant biosiliceous source and high microbial activity in the sediments immediately below the seafloor. Flint is therefore likely to reflect deposition in a narrow interval at relatively shallow depths and therefore might be useful in studies of shallow-water carbonates.

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“…Source of Strontium Sr is the main element of the celestine, and Sr isotope analysis is widely used to identify the sources of Sr in the celestine [1,18,23,91]. Most of the celestine deposits located around the world are mainly hosted in marine carbonates and evaporites [92,93], and the Sr isotope value of celestine is consistent with/or slightly different from that of coeval seawater [10], indicating that the formation of celestine deposits is closely related to seawater, and some authors state that the mineralization age of the deposit by comparing the Sr isotope ratio of celestine with that of seawater [2,27].…”

Section: Nature Of the Mineralizing Fluidmentioning

confidence: 99%

“…The reason for that is complex; it can be caused by S fractionation or by the mixing of sulfur from different sources. TSR and BSR are two significant processes of S fractionation in celestine deposits [92,117]. BSR usually occurs during diagenesis at 0 to 80 • C [109], while the lowest temperature of TSR is 127 • C [118,119].…”

Section: Source Of Sulfurmentioning

confidence: 99%

Geological and Geochemical Constraints on the Origin of the Sr Mineralization in Huayingshan Ore District, Chongqing, South China

et al. 2023

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There are many celestine deposits and mineralization points in the Huayingshan ore district which form the largest strontium resource base in China. Among these celestine deposits, the Yuxia and Xinglong are two of the larger deposits. Previous studies have displayed different views on the genesis of the celestine deposit in the Huayingshan ore district. In this study, we conducted field obversions, geochemistry, and fluid inclusion studies to investigate the sources of ore-forming matters and the metallogenic mechanism of the celestine deposit. Four types of fluid inclusion (FI), namely PL (pure liquid FI), PV (pure vapor FI), L-V (liquid-vapor two-phase FI), and L-V-S (liquid-vapor-solid three-phase FI) have been identified in celestine from different types of ore in the Xishan anticline. The ore-forming fluids belong to the NaCl-H2 O system with moderate to low temperature (190–220 °C) and moderate salinity (5–9 wt%, NaCl equiv.). Different types of ores were formed by the same period of hydrothermal activity, which is supported by the results of the microthermometer study. Geological, thermometric data, and published hydrogen and oxygen isotope results indicate that the hot brines associated with mineralization mainly originated from meteoric water and some of diagenetic fluid. The Sr (87Sr/86Sr = 0.7076–0.7078) and S (δ34S = 36.4–39.0) isotope values of celestine are consistent with those of the Jialingjiang Formation, indicating that ore metals in hot brines were predominantly derived from that formation. In situ analysis of celestine shows that there is a strong negative correlation between Sr and CaO (R2 = 0.95) and combined with mineralogical and isotope geochemical evidence, we concluded that the precipitation mechanism of celestine is the replacement of gypsum with Sr-rich hot brines. Based on the above research and the classification of celestine deposit type, we classified the celestine deposits in Huayingshan as being of hydrothermal type. The formation of celestine deposits can be divided into three periods: (1) evaporation period, forming the source bed; (2) hydrothermal activity period, forming celestine by replacement of gypsum with Sr-rich hot brines; (3) supergene period, where meteoric water dissolves orebodies and strontianization occurs.

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Early diagenetic celestite replacement of demosponges in Upper Cretaceous (Campanian–Maastrichtian) chalk, Stevns, Denmark

Cited by 12 publications

References 18 publications

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

Diagenesis of Flint and Porcellanite in the Maastrichtian Chalk at Stevns Klint, Denmark

Geological and Geochemical Constraints on the Origin of the Sr Mineralization in Huayingshan Ore District, Chongqing, South China

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