The influence of silica on reaction rates and molecular hydrogen (H_2) generation during olivine hydrothermal alteration

IOCAS-IR

	The influence of silica on reaction rates and molecular hydrogen (H_2) generation during olivine hydrothermal alteration
	Ruifang HUANG ; Weidong SUN; Xing DING ; Yusheng ZHAO ; Yibing LI ; Xiuqi SHANG
发表期刊	Science China Earth Sciences
ISSN	1674-7313
	2023-12-18
出版年	2024
卷号	v.67 期号:01 页码:226-237
文献类型	CNKI期刊论文
摘要	Hydrothermal alteration of olivine greatly influences geodynamics and the recycling of volatiles (such as water and carbon) in subduction zones.Silica is an important component of geological fluids,and its influence on the hydrothermal alteration of olivine remains poorly constrained.In this study,we performed experiments at 300–515℃ and 3.0 kbar (1 bar=10~5Pa) by reacting well homogenized mixtures of olivine and silica powders with saline solutions (0.5 mol L~(-1)Na Cl).Silica greatly influences the reaction pathways,reaction rates,and molecular hydrogen (H_2) formation during olivine hydrothermal alteration.In experiments at 300℃ and 3.0 kbar with mixtures of olivine and 10 wt%silica,olivine was replaced by serpentine and talc.The proportions of serpentine and talc were determined according to standard curves based on infrared spectroscopy analyses.Around 6.5%serpentine and 12%talc were produced after an experimental duration of 7 days,which had no change after a longer period (14 days).Compared to the kinetics in silica-free systems,the rates of olivine hydrothermal alteration in experiments with 10 wt%silica are much lower.The overall reaction is:4.5Forsterite+5.5SiO_(2,aq)+4H_2O=Serpentine+2Talc.With the addition of more silica (20 wt%and 40 wt%),olivine was transformed into talc.The rates of reaction were much faster,e.g.,for experiments with olivine and 20 wt%silica,43%of talc was produced after 14 days,which increased to 77% for experiments with 40 wt%silica over the same period.The overall reaction is:3Forsterite+5SiO_(2,aq)+2H_2O=2Talc.In experiments at400–505℃ and 3.0 kbar,the promoting effect of silica on olivine hydrothermal alteration was also observed,which is closely associated with a decrease in Gibbs free energies of olivine hydrothermal alteration.At 300℃ and 3.0 kbar,silica decreased H_2 formed during olivine hydrothermal alteration by around an order of magnitude,resulting in an increase in oxygen fugacity.Based on measured H_2,we calibrated oxygen fugacities,ranging from 0.96 to 3.41 log units below FMQ (fayalite-magnetitequartz buffer assemblage).This study suggests that the infiltration of SiO_2-bearing fluids into peridotites greatly influences redox conditions and the rates of olivine hydrothermal alteration.
关键词	Olivine hydrothermal alteration Silica Serpentinization Hydrogen Serpentine
CNKI专辑号	A;
CNKI专辑名称	基础科学;
CNKI专题号	A011;
CNKI专题名称	地质学;
分类号	P588.323
收录类别	中科院核心 ; 中科院扩展
语种	英文;
资助项目(基金）	supported by the National Natural Science Foundation of China (Grant No. 41873069) ; the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA22050103, XDB42000000) ; the Shenzhen Municipal Natural Science Foundation (Grant No. JCYJ20220530113016038)
文献类型	CNKI期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/186935
专题	中国科学院海洋研究所
作者单位	1.CASKeyLaboratoryofOceanandMarginalSeaGeology,SouthChinaSeaInstituteofOceanology,ChineseAcademyofSciences 2.SUSTechAcademyforAdvancedInterdisciplinaryStudies,SouthernUniversityofScienceandTechnology 3.CenterofDeepSeaResearch,InstituteofOceanology,ChineseAcademyofSciences 4.StateKeyLaboratoryofIsotopeGeochemistry,GuangzhouInstituteofGeochemistry,ChineseAcademyofSciences 5.InstitueofGeology,ChineseAcademyofGeologicalSciences
推荐引用方式 GB/T 7714	Ruifang HUANG,Weidong SUN,Xing DING,et al. The influence of silica on reaction rates and molecular hydrogen (H_2) generation during olivine hydrothermal alteration. 2023.