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Kinetic inhibition of dolomite precipitation: Insights from Raman spectroscopy of Mg2+-SO42- ion pairing in MgSO4/MgCl2/NaCl solutions at temperatures of 25 to 200 degrees C
Wang, Xiaolin1; Chou, I-Ming2; Hu, Wenxuan1; Yuan, Shunda3; Liu, Hao1; Wan, Ye1; Wang, Xiaoyu1
2016-10-01
Source PublicationCHEMICAL GEOLOGY
Volume435Pages:10-21
AbstractThe origin of dolomite has been an issue for hundreds of years, and its kinetic inhibition is a critical aspect of this issue. Dissolved sulfate is regarded as an inhibitor for dolomite formation because it can bindMg(2+) to form tight ion pairs and thus prevent the incorporation of Mg2+ into dolomite. Using Raman spectroscopy, we investigated the Mg2+-SO42- association in vapor-saturated aqueous MgSO4/MgCl2/NaCl solutions at temperatures of 25 to 200 degrees C. The Mg2+-SO42- association is highly temperature and concentration dependent: the fractions of contact ion pairs (CIPs) and triple ion pairs (TIs) increase with increasing temperature and MgSO4 concentration. The presence of MgCl2 increases the Mg2+/SO42- ratio and favors Mg2+-SO42- interactions to produce CIPs and TIs, whereas the presence of NaCl exerts a negative effect on Mg2+-SO42- interactions, particularly at high temperatures (i.e., >= 150 degrees C). The primary sulfate species in concentrated MgSO4 solutions at high temperatures (i.e., >= 2 mol/kg, 200 degrees C) are various contact ion pairs, whereas those in diluted solutions at Earth surface temperature appear to be unassociated SO42- and weakly associated solvent-separated and solvent-shared ion pairs. We propose that dissolved sulfate can inhibit the incorporation of Mg-2(+) into dolomite crystals by attracting Mg-2(+) to form tight contact ion pairs under hydrothermal conditions. However, thermochemical sulfate reduction (TSR) can effectively remove sulfate and free Mg-2(+) to enhance the precipitation of hydrothermal dolomite from sulfate-bearing fluids. The inhibiting effect of dissolved sulfate on the formation of massive low-temperature dolomite appears to have been overestimated. Removal of sulfate by anaerobic bacterial sulfate reduction (BSR) may not be responsible for the formation of microbial dolomite at surface temperatures. These new understandings also have implications for the study of thermochemical sulfate reduction because the formation of CIPs can increase the activity of sulfate in reactions with hydrocarbons. (C) 2016 Elsevier B.V. All rights reserved.
SubtypeArticle
KeywordRaman Sulfate Ion associatIon Dolomite Origin
WOS HeadingsScience & Technology ; Physical Sciences
DOI10.1016/j.chemgeo.2016.04.020
URL查看原文
Indexed BySCI
Language英语
WOS KeywordSULFATE-REDUCING BACTERIA ; X-RAY-DIFFRACTION ; MAGNESIUM-SULFATE ; HYDROTHERMAL DOLOMITE ; AQUEOUS-SOLUTIONS ; HYGROSCOPIC PROPERTIES ; SEDIMENTARY DOLOMITE ; MOLECULAR-DYNAMICS ; FLUID INCLUSIONS ; SOUTH-AUSTRALIA
WOS SubjectGeochemistry & Geophysics
WOS IDWOS:000377373500002
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Cited Times:6[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Version同行评议接收稿
Identifierhttp://ir.idsse.ac.cn/handle/183446/1537
Collection深海科学研究部_深海极端环境模拟研究实验室
Affiliation1.Nanjing Univ, Inst Energy Sci, State Key Lab Mineral Deposits Res, 163 Xianlin Ave, Nanjing 210023, Jiangsu, Peoples R China
2.Chinese Acad Sci, Sanya Inst Deep Sea Sci & Engn, Lab Expt Study Deep Sea Extreme Condit, Sanya 572000, Hainan, Peoples R China
3.Chinese Acad Geol Sci, Insitute Mineral Resources, Beijing 100037, Peoples R China
Recommended Citation
GB/T 7714
Wang, Xiaolin,Chou, I-Ming,Hu, Wenxuan,et al. Kinetic inhibition of dolomite precipitation: Insights from Raman spectroscopy of Mg2+-SO42- ion pairing in MgSO4/MgCl2/NaCl solutions at temperatures of 25 to 200 degrees C[J]. CHEMICAL GEOLOGY,2016,435:10-21.
APA Wang, Xiaolin.,Chou, I-Ming.,Hu, Wenxuan.,Yuan, Shunda.,Liu, Hao.,...&Wang, Xiaoyu.(2016).Kinetic inhibition of dolomite precipitation: Insights from Raman spectroscopy of Mg2+-SO42- ion pairing in MgSO4/MgCl2/NaCl solutions at temperatures of 25 to 200 degrees C.CHEMICAL GEOLOGY,435,10-21.
MLA Wang, Xiaolin,et al."Kinetic inhibition of dolomite precipitation: Insights from Raman spectroscopy of Mg2+-SO42- ion pairing in MgSO4/MgCl2/NaCl solutions at temperatures of 25 to 200 degrees C".CHEMICAL GEOLOGY 435(2016):10-21.
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