Brucite in the Calcareous Alga
            <i>Goniolithon</i>

Weber, Jon N.; Kaufman, J. W.

doi:10.1126/science.149.3687.996

Cited by 28 publications

(3 citation statements)

References 8 publications

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“…In some instances the precipitation of secondary minerals within the interstices of 'live' skeletal materials can contribute significantly to the trace element concentration of carbonates. For example the mineral brucite (Mg(OH 2 ) has been recorded within coral skeletons (Schmalz, 1965;Buster & Holmes, 2006) and some calcareous algae (Weber & Kaufman, 1965), thereby increasing the Mg content. Other secondary minerals within skeletons, such as LMC and aragonite, have also been widely documented and are known to alter primary elemental and stable isotopic compositions affecting palaeoenvironmental interpretations (McGregor & Gagan, 2003;Hendy et al, 2007).…”

Section: Secondary Minerals Within Skeletonsmentioning

confidence: 99%

The geochemistry of carbonate diagenesis: The past, present and future

2015

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Stable carbon and oxygen isotopes ( 18 O and  13 C values) and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years. As valuable as these insights have been, many problems regarding the interpretation of geochemical signals within mature rocks remain. For example, while the  18 O values of carbonate rocks are dependent both upon the temperature and the  18 O value of the fluid and additional information, including trace element composition aids in interpreting such signals, direct evidence of either the temperature or the composition of the fluids is required. Such information can be obtained This article is protected by copyright. All rights reserved.by analyzing the  18 O value of any fluid inclusions or by measuring the temperature using a method such as the 'clumped' isotope technique. Such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well-known tendency for  18 O values of carbonate rocks to decrease with increasing age. Unlike the  18 O,  13 C values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time. However, many studies have not sufficiently emphasized the effects of diagenesis and other post-depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored. Finally, many additional proxies are poised to contribute to the interpretation of carbonate diagenesis. Although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods, care should be taken to understand both old and new proxies before applying them to the ancient record.

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Section: Secondary Minerals Within Skeletonsmentioning

confidence: 99%

The geochemistry of carbonate diagenesis: The past, present and future

2015

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“…This experiment showed that incongruent dissolution occurs also in sea water; it must be evaluated with caution, since Goniolithon contains a small portion of brucite (Schmalz, 1965;Weber and Kaufman, 1965).…”

Section: Introductionmentioning

confidence: 95%

Experimental Dissolution of Calcium, Magnesium, and Strontium from Recent Biogenic Carbonates: A Model of Diagenesis

Schroeder¹

1969

SEPM JSR

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Laboratory experiments at ordinary temperature and pressure for periods up to 240 days on Recent biogenic carbonate materials showed that fresh water and sea water dissolve aragonite and magnesium calcite prior to mineralogical changes.The observed rates of dissolution of calcium, magnesium, and strontium indicate that these elements are incorporated in aragonite and magnesium calcite in more than one way (ill lattice positions, absorbed in lattice interstices, or as inclusions). This suggests the presence of more than one mineral phase in the skeletal material studied; these phases differ in response to solution, in quantity, and probably in chemical composition.Calcium, magnesium, and strontium are dissolved in proportions different from those in the original solid, that is incongruently. The experimentally established sequence of preference is Mg > Ca > Sr, as a rule Factors found to determine direction and degree of incongruency in dissolution include mineralogy (number, kind, and relative abundance oI phases present), chemical composition, physiologic effects (taxonomy and non-taxonomy related), and chemical composition and volume of waters effective in dissolution.Incongruent dissolution determines abundance of ions derived from solids in the diagenetic environment and hence, ion availability for precipitation in cement and for inhibition or catalysis in inversion or cement precipitation. Magnesium and strontium contents of shell material have been used by others as temperature and salinity indicators in Recent environments. The present study shows that because of incongruent dissolution these indicators are not dependable for paleo-environmental analysis. DISSOLUTION OF CALCIUM, MAGNESIUMAND STRONTIUM

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“…Mg-calcite(~), where x is the mole fraction Mg/Ca+Mg, will be used ~o denote the infinite variety of skeletal phases found in nature (Chave, 1954;Chave and Wheeler, 1965). Some Mg-ealcites, especially those formed by the red algae, contain magnesium not present as MgCO~ (Goldsmith, Graf and Joensuu, 1955;Schmalz, 1965;Weber and Kaufman, 1965), and therefore "mol percent MgC03" is not always correct.…”

Section: Mg-calcite Exsolutionmentioning

confidence: 99%

Diagenesis of Skeletal Carbonates

Land¹

1967

SEPM JSR

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Stabilization of metastable aragonite and Mg-calcites is an inevitable process and constitutes a large and important part of carbonate diagenesls. Stabilization can occur in only a limited number of ways. "Solid state" stabilization takes place by inversion or exsolution for aragonlte and Mg-calcite, respectively. Stabilization can take place by total dissolution and reprecipitation, or in the case of the Mg-calcites, by incongruent dissolution yielding a replacement product of calcite plus a solution enriched in magnesium. Lastly, stabilization can take place by replacement by either dolomite or a non-carbonate phase.The processes of stabilization which skeletal reactants undergo have been investigated by hydrothermal techniques, and the products of the reactions studied in thin sections. Aragonite inversion produces coarsegrained equigranular mosaics, and the rate of inversion of skeletal material seems to be only temperature-dependent near 300°C. Non-skeletal aragonite is less reactive. Mg-calcite exsolution is very slow compared to aragonite inversion, and the phase which exsolves is a very calclum-rlch "disordered" protodolomite.The kinetics of dolomitization have been studied semiquantltatlvely near 300°C in aqueous solution. Dolomitization is speeded by:a. increased instability of the reactant, b. increased calcium plus magnesium concentration of the dolomltizlng solutlon, c. increased magnesium/calcium ratio of the dolomitizing solution, d. increased solution/solid ratio, and e. increased temperature

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Brucite in the Calcareous Alga Goniolithon

Cited by 28 publications

References 8 publications

The geochemistry of carbonate diagenesis: The past, present and future

The geochemistry of carbonate diagenesis: The past, present and future

Experimental Dissolution of Calcium, Magnesium, and Strontium from Recent Biogenic Carbonates: A Model of Diagenesis

Diagenesis of Skeletal Carbonates

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