水热条件下方解石-磷灰石转化机制影响因素初探
Apatite formation from calcite under hydrothermal environment: transforming mechanisms and influencing factors

师城 ¹ 陆现彩 ¹ 蔡元峰 ¹ 何宏平 ² ^*

文摘	磷灰石广泛存在于生物体和各种地质体中,其形成机制随物理化学条件变化而变化。本文采用Raman光谱、扫描电镜和X射线谱仪等技术研究了水热条件下,方解石向羟基磷灰石转变过程中矿物物相的变化,探讨了羟基磷灰石的形成机制。结果表明,在弱酸性环境下,方解石中的碳酸根离子先被溶液中的磷酸氢根离子交代,形成二水合磷酸氢钙(DCPD),随后部分DCPD经过脱水脱氢作用逐步转变为羟基磷灰石(HAP),还有部分磷酸氢钙溶解在水溶液中;但在碱性环境下,仅有少量的方解石转变为HAP。由此可知,磷酸盐流体中,羟基磷灰石替代方解石的生长是一种溶解-沉淀耦合的过程。低温条件下,酸性缓冲溶液条件首先生成DCPD,而后转变为HAP,碱性条件直接生成HAP。温度升高能加速方解石向HAP的转变,并且未发现DCPD的中间相。
其他语种文摘	Apatite widely occurs in organisms and various rocks,and its formation mechanisms change with changing physical and chemical conditions. In this study,Raman spectroscopy and field emission scanning electron microscope with energy spectrometer technology were used to study the phase transition in the replacement of calcite by hydroxyapatite in hydrothermal conditions. Formation mechanisms of hydroxyapatite were also discussed. Results show that hydrogen phosphate ion from the solution replaces carbonic acid ion of calcite first in weakly acid environment and forms dicalcium phosphate dehydrate(DCPD). Some of the DCPD become hydroxyapatite (HAP) progressively through the dehydration and dehydrogenation process; others would dissolve in aqueous solution. However,in alkaline environment,only a small fraction of calcite is replaced by HAP. Therefore,the replacement reactions from calcite to hydroxyapatite are explained by“the coupled dissolution-reprecipitation”mechanism. Under low temperature condition,acid buffer solution promotes the formation of DCPD and alkaline condition,on the other hand facilitates the formation of HAP. High temperature accelerates the replacement of calcite by HAP and no DCPD phase was observed in this condition.
来源	矿物学报 ,2018,38(1):58-63 【核心库】
DOI	10.16461/j.cnki.1000-4734.2018.007
关键词	羟基磷灰石 ; 方解石 ; 水热反应 ; 相变 ; 溶解-沉淀耦合机制
地址	1. 南京大学地球科学与工程学院, 内生金属成矿机制研究国家重点实验室, 江苏, 南京, 210046 2. 中国科学院广州地球化学研究所, 广东, 广州, 510640
语种	中文
文献类型	研究性论文
ISSN	1000-4734
学科	地质学
基金	国家大学生创新创业训练计划
文献收藏号	CSCD:6221055