Influences of alkalinity and pCO2 on CaCO3 nucleation from estimated Cretaceous composition seawater representative of “calcite seas”
2010; Geological Society of America; Volume: 38; Issue: 2 Linguagem: Inglês
10.1130/g30537.1
ISSN1943-2682
Autores Tópico(s)Paleontology and Stratigraphy of Fossils
ResumoResearch Article| February 01, 2010 Influences of alkalinity and pCO2 on CaCO3 nucleation from estimated Cretaceous composition seawater representative of "calcite seas" Janie Lee; Janie Lee * Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA *E-mail: jlee@ocean.tamu.edu. Search for other works by this author on: GSW Google Scholar John W. Morse John W. Morse Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Janie Lee * Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA John W. Morse Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA *E-mail: jlee@ocean.tamu.edu. Publisher: Geological Society of America Received: 17 Jul 2009 Revision Received: 20 Aug 2009 Accepted: 21 Aug 2009 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2010 Geological Society of America Geology (2010) 38 (2): 115–118. https://doi.org/10.1130/G30537.1 Article history Received: 17 Jul 2009 Revision Received: 20 Aug 2009 Accepted: 21 Aug 2009 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Janie Lee, John W. Morse; Influences of alkalinity and pCO2 on CaCO3 nucleation from estimated Cretaceous composition seawater representative of "calcite seas". Geology 2010;; 38 (2): 115–118. doi: https://doi.org/10.1130/G30537.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Experiments were conducted on CaCO3 nucleation in seawater of estimated Cretaceous Period "calcite sea" (i.e., low-magnesium calcite being the primary inorganic marine calcium carbonate precipitate) composition to determine the influences of alkalinity and pCO2 on calcite versus aragonite formation. The pH was continually monitored throughout the experiments and it was used, in combination with the initial alkalinity, to calculate the pCO2 and saturation state of aragonite and calcite at the time of nucleation. The morphology and mineralogy of the precipitates were determined using scanning electron microscopy and X-ray diffraction analyses. It was observed that the initial alkalinity affected greatly the nucleation pCO2 and the CaCO3 polymorph that is precipitated. In seawater with Mg2+/Ca2+ = 1.2, ∼10 mM alkalinity, and a pCO2 2500 μatm. Seawater with Mg2+/Ca2+ = 1.2 and a wide range of initial alkalinities (5–50 mM) produces variable results. Seawater with Mg2+/Ca2+ = 1.7 produces only aragonite at lower alkalinities (<∼11 mM), but calcite is formed when the alkalinity is >∼18 mM. These results demonstrate the need to also consider the effects of alkalinity and pCO2 in the critical Mg2+/Ca2+ ratio region of ∼1–2 for calcite seas versus "aragonite seas" (in which the primary inorganic carbonate precipitates are aragonite and high-magnesium calcite) at various times throughout the Phanerozoic Eon and to use reasonable estimated values of alkalinity and pCO2 in experimental studies. The results of this study indicate that it may have been possible for CaCO3 to commonly nucleate directly from Cretaceous seawater due to elevated calcium and alkalinity concentrations, even though atmospheric pCO2 was higher. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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