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Experimental Insights into the Origin of Microcrystalline Calcites.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Experimental Insights into the Origin of Microcrystalline Calcites./
Author:	Hashim, Mohammed S.
Description:	1 online resource (259 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 83-12, Section: B.
Contained By:	Dissertations Abstracts International83-12B.
Subject:	Geochemistry. -
Online resource:	click for full text (PQDT)
ISBN:	9798438782766

Experimental Insights into the Origin of Microcrystalline Calcites.
Hashim, Mohammed S.

Experimental Insights into the Origin of Microcrystalline Calcites. - 1 online resource (259 pages)

Source: Dissertations Abstracts International, Volume: 83-12, Section: B.

Thesis (Ph.D.)--Western Michigan University, 2022.

Includes bibliographical references

A significant proportion of modern marine calcium carbonate sediments is dominated by metastable aragonite and high Mg calcite that either dissolves or stabilizes to low-Mg-calcite (calcite) or dolomite during diagenesis. Sediment dissolution and stabilization have implications for the CaCO3 budget in the ocean and carbon burial rates. Yet, the diagenetic conditions that promote each process and their relative importance are poorly understood. Further, stabilization most commonly produces calcite microcrystals that exhibit various textures and host micropores. Despite their ubiquity in the rock record, the controls on microcrystal textures remain unclear. Here, laboratory experiments were used to investigate aragonite-to-calcite stabilization as well as calcite dissolution under various conditions. Results from stabilization experiments show that the well-documented Mg inhibitory effect of calcite precipitation during stabilization is valid only at high fluid:solid ratios (F:S). at low F:S, stabilization readily occurs despite the presence of Mg at near seawater concentrations. These observations suggest that the stabilization of aragonite-rich sediments to calcite-rich limestones is likely promoted by a decrease in F:S and the development of a closed system during burial. The results also show that calcite microcrystal texture is controlled by various depositional and diagenetic parameters including fluid chemistry, temperature, as well as aragonite reactant type and size. These findings challenge existing hypotheses by showing that certain calcite textures previously interpreted to reflect later stage dissolution and cementation, can form during early diagenesis. The results also show that rhombic calcite microcrystals form only under conditions that prevail in meteoric settings, implying that this crystal morphology can be used as a textural proxy for meteoric diagenesis. Results from our dissolution experiments show that the degree of fluid undersaturation with respect to calcite correlates with district textural features at the surface of dissolving crystals, suggesting that these distinguishing features can be used to discern dissolution conditions and mechanisms in natural settings.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798438782766Subjects--Topical Terms:

648291
Geochemistry.
Subjects--Index Terms:

AragoniteIndex Terms--Genre/Form:

554714
Electronic books.

Experimental Insights into the Origin of Microcrystalline Calcites.
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245 1 0 $a Experimental Insights into the Origin of Microcrystalline Calcites.
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502 $a Thesis (Ph.D.)--Western Michigan University, 2022.
504 $a Includes bibliographical references
520 $a A significant proportion of modern marine calcium carbonate sediments is dominated by metastable aragonite and high Mg calcite that either dissolves or stabilizes to low-Mg-calcite (calcite) or dolomite during diagenesis. Sediment dissolution and stabilization have implications for the CaCO3 budget in the ocean and carbon burial rates. Yet, the diagenetic conditions that promote each process and their relative importance are poorly understood. Further, stabilization most commonly produces calcite microcrystals that exhibit various textures and host micropores. Despite their ubiquity in the rock record, the controls on microcrystal textures remain unclear. Here, laboratory experiments were used to investigate aragonite-to-calcite stabilization as well as calcite dissolution under various conditions. Results from stabilization experiments show that the well-documented Mg inhibitory effect of calcite precipitation during stabilization is valid only at high fluid:solid ratios (F:S). at low F:S, stabilization readily occurs despite the presence of Mg at near seawater concentrations. These observations suggest that the stabilization of aragonite-rich sediments to calcite-rich limestones is likely promoted by a decrease in F:S and the development of a closed system during burial. The results also show that calcite microcrystal texture is controlled by various depositional and diagenetic parameters including fluid chemistry, temperature, as well as aragonite reactant type and size. These findings challenge existing hypotheses by showing that certain calcite textures previously interpreted to reflect later stage dissolution and cementation, can form during early diagenesis. The results also show that rhombic calcite microcrystals form only under conditions that prevail in meteoric settings, implying that this crystal morphology can be used as a textural proxy for meteoric diagenesis. Results from our dissolution experiments show that the degree of fluid undersaturation with respect to calcite correlates with district textural features at the surface of dissolving crystals, suggesting that these distinguishing features can be used to discern dissolution conditions and mechanisms in natural settings.
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538 $a Mode of access: World Wide Web
650 4 $a Geochemistry. $3 648291
650 4 $a Petrology. $3 783490
650 4 $a Paleoclimate science. $3 1185587
653 $a Aragonite
653 $a Calcite
653 $a Carbon cycle
653 $a Carbonate sediments and rocks
653 $a Limestone microporosity
653 $a Paleoclimate paleoenvironment paleoceanography
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710 2 $a Western Michigan University. $b Geological and Environmental Sciences. $3 1473107
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