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Assessing the Role of Solution Chemistry and Organic Matter in the Genesis of the Dengying Formation Dolostones at Sichuan Basin, China.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Assessing the Role of Solution Chemistry and Organic Matter in the Genesis of the Dengying Formation Dolostones at Sichuan Basin, China./
作者:	Rodriguez-Colon, Bryan J.
面頁冊數:	1 online resource (228 pages)
附註:	Source: Masters Abstracts International, Volume: 82-09.
Contained By:	Masters Abstracts International82-09.
標題:	Geochemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28261901click for full text (PQDT)
ISBN:	9798582573722

Assessing the Role of Solution Chemistry and Organic Matter in the Genesis of the Dengying Formation Dolostones at Sichuan Basin, China.
Rodriguez-Colon, Bryan J.

Assessing the Role of Solution Chemistry and Organic Matter in the Genesis of the Dengying Formation Dolostones at Sichuan Basin, China. - 1 online resource (228 pages)

Source: Masters Abstracts International, Volume: 82-09.

Thesis (M.S.)--University of Kansas, 2020.

Includes bibliographical references

The role that microorganisms play in low-temperature dolomite formation is still unresolved. Given the scarcity of dolomite in modern low-temperature depositional settings, controls on its formation remain unclear. Textural evidence from modern and ancient geomicrobiological dolomite-forming environments, combined with laboratory experiments that produce dolomite phases associated with microbial surfaces and metabolism, support a microbial model for dolomite formation. However, more research is needed to substantiate this model. This study here aims to clarify the role of organic matter abundance and solution chemistry in a putative microbial dolomite: the Neoproterozoic dolomite of the Dengying Formation, Sichuan Basin, China. Researchers debate the origin of dolomite with different data supporting a microbial model conflicting with late-state hydrothermal dolomite. This study tested the microbial model for dolomite formation in the Dengying using controlled laboratory experiments constructed to emulate Ediacaran seawater chemistry (ESW) with abundant microbial mats. The constructed Ediacaran solution chemistry accounted for alkalinity, pH, temperature, and dissolved sulfate. Experimental variables included differing Mg:Ca (1:1) ratios, the presence of dissolved silica in solution (ESW no silica), and presence/absence of synthetic organic matter (in the form of carboxyl microspheres).Solution pH, alkalinity and dolomite saturation index decreased through the incubation period in all solutions. Further, aragonite and Mg-calcite (with mol % of Mg ranging from 15-25% MgCO3) precipitates were the main mineral suite of the ESW solution, while calcite and small yields of aragonite predominated in the 1:1 solution. Further, microscopy analysis shows an association between magnesium ions and dissolved silica, the presence of spheroidal precipitates associated with the microspheres and possible Mg-carbonate precipitation in the carboxylated surfaces. Despite trends in the literature that suggest both silica and organic carbon play crucial roles in the availability of Mg for the dolomite reaction, our results did not document dolomite nucleation and precipitation from any of the studied solutions. Our summarized results suggest parallelisms with likely initial stages of carbonate precipitation in the Ediacaran prior to early or late stage dolomitization processes. While results from this study do not substantiate a microbial model of dolomite formation nor do they abrogate this possibility, our data underscore the complex interactions between solution chemistry and surface nucleation and their interaction to produce dolomite at low temperature.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798582573722Subjects--Topical Terms:

539092
Geochemistry.
Subjects--Index Terms:

Dengying formationIndex Terms--Genre/Form:

542853
Electronic books.

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500 $a Source: Masters Abstracts International, Volume: 82-09.
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502 $a Thesis (M.S.)--University of Kansas, 2020.
504 $a Includes bibliographical references
520 $a The role that microorganisms play in low-temperature dolomite formation is still unresolved. Given the scarcity of dolomite in modern low-temperature depositional settings, controls on its formation remain unclear. Textural evidence from modern and ancient geomicrobiological dolomite-forming environments, combined with laboratory experiments that produce dolomite phases associated with microbial surfaces and metabolism, support a microbial model for dolomite formation. However, more research is needed to substantiate this model. This study here aims to clarify the role of organic matter abundance and solution chemistry in a putative microbial dolomite: the Neoproterozoic dolomite of the Dengying Formation, Sichuan Basin, China. Researchers debate the origin of dolomite with different data supporting a microbial model conflicting with late-state hydrothermal dolomite. This study tested the microbial model for dolomite formation in the Dengying using controlled laboratory experiments constructed to emulate Ediacaran seawater chemistry (ESW) with abundant microbial mats. The constructed Ediacaran solution chemistry accounted for alkalinity, pH, temperature, and dissolved sulfate. Experimental variables included differing Mg:Ca (1:1) ratios, the presence of dissolved silica in solution (ESW no silica), and presence/absence of synthetic organic matter (in the form of carboxyl microspheres).Solution pH, alkalinity and dolomite saturation index decreased through the incubation period in all solutions. Further, aragonite and Mg-calcite (with mol % of Mg ranging from 15-25% MgCO3) precipitates were the main mineral suite of the ESW solution, while calcite and small yields of aragonite predominated in the 1:1 solution. Further, microscopy analysis shows an association between magnesium ions and dissolved silica, the presence of spheroidal precipitates associated with the microspheres and possible Mg-carbonate precipitation in the carboxylated surfaces. Despite trends in the literature that suggest both silica and organic carbon play crucial roles in the availability of Mg for the dolomite reaction, our results did not document dolomite nucleation and precipitation from any of the studied solutions. Our summarized results suggest parallelisms with likely initial stages of carbonate precipitation in the Ediacaran prior to early or late stage dolomitization processes. While results from this study do not substantiate a microbial model of dolomite formation nor do they abrogate this possibility, our data underscore the complex interactions between solution chemistry and surface nucleation and their interaction to produce dolomite at low temperature.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Geochemistry. $3 539092
650 4 $a Geobiology. $3 549918
653 $a Dengying formation
653 $a Dolomite
653 $a Ediacaran seawater
653 $a Microbial dolomite
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773 0 $t Masters Abstracts International $g 82-09.
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