Brucite in Carbonate Secreted by the Red Alga
            <i>Goniolithon</i>
            sp.

Schmalz, Robert F.

doi:10.1126/science.149.3687.993

Cited by 37 publications

(12 citation statements)

References 5 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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“…Concentrations of up to 28 mole percent magnesium carbonate have been reported(Chave, 1954), but some of the magnesium is present as brucite, Mg (OH)", rather in solid solution with calcite(Schmalz, 1965). on June 8, 2015 memoirs.gsapubs.org Downloaded from…”

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confidence: 99%

PART I: Holocene Sediment Accumulations of the South Florida Shelf Margin

Enos¹

1977

Geological Society of America Memoirs

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The carbonate shelf-margin depositional model is fundamental to understanding carbonate rocks and to petroleum exploration in carbonate rocks. The sedimentary package is normally thick and permeable, trends and facies patterns are inherently predictable, and a variety of diagenetic environments are encountered. The south Florida shelf margin is one of the few currently active carbonate shelf margins and a large area where the surface sediments are relatively well known. The Holocene-Pleistocene package, the latest chapters in a long history of shallowwater carbonate deposition, is prograding seaward toward the edge of the continental shelf. The Holocene sedimentary sequence was dissected in the third dimension to study accumulation patterns, variations in the patterns, sediment sources, and pore-space characteristics. A compact, high-resolution seismic profiler, a core driver for underwater coring of sandy sediments, and a permeameter for measuring flow rates through sediment cores were essential tools in this study.Natural subdivisions of the south Florida shelf are the restricted inner shelf (Florida Bay), the slightly restricted inner shelf margin, the outer shelf margin where circulation and turbulence are maximum, and the shallow slope seaward of the shelf break. Water turbidity, temperature variations, and salinity variations generally increase landward from the shelf break. Substrate is a primary control on the organism habitat communities; organisms, in turn, produce virtually all the sediment of the substrate. Other important controls are bottom morphology and restriction of circulation. Mappable habitat communities and their sedimentologically important inhabitants on the south Florida shelf are: 1. Rock or dead reef a. open marine -mainly encrusting and boring organisms b. restricted circulation -mainly encrusters and borers 1 on June 8, 2015 memoirs.gsapubs.org Downloaded from on June 8, 2015 memoirs.gsapubs.org Downloaded from HOLOCENE SEDIMENT ACCUMULATIONS 3Holocene sediment is thickest in three discontinuous linear accumulations parallel to the shelf break. The most extensive and thickest accumulations (up to 14 m) are along the outer reefs. Behind the outer reefs, a second belt is formed by sand shoals up to 40 km (25 mi) long or by discontinuous patch-reef banks. The belt of sediment accumulations on the shallow slope is a seaward-thinning wedge up to 12 m (40 ft) thick. Sediment accumulation in the inner shelf margin is thickest in patch-reef banks, tidal deltas (up to 8 m), and broad flattopped wedges near the Keys (up to 7 m). The belts of thick sediment vary along depositional strike, parallel to the shelf break, in thickness, width, and continuity. This is particularly striking with the sand shoals that disappear to the southwest and are replaced to the north-northeast by discontinuous patch-reef banks. Areas of maximum development of all three belts tend to coincide, as do areas of minimum development. Accordingly, strong contrasts exist in the degree to which a given area has been "filled...

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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 Carbonate Secreted by the Red Alga Goniolithon sp.

Cited by 37 publications

References 5 publications

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

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

PART I: Holocene Sediment Accumulations of the South Florida Shelf Margin

Diagenesis of Skeletal Carbonates

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