花岗伟晶岩中锂霞石形成机制的实验研究

doi:10.13745/j.esf.sf.2025.1.24

地学前缘 ›› 2026, Vol. 33 ›› Issue (2): 27-39.DOI: 10.13745/j.esf.sf.2025.1.24

• 战略矿产前沿分析与勘查技术 • 上一篇下一篇

花岗伟晶岩中锂霞石形成机制的实验研究

刘强¹^,²^,³(), 李建康¹, 刘永超¹^,^*()

1.中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室, 北京 100037
2.北京大学地球与空间科学学院, 北京 100871
3.云南省能源投资集团有限公司, 云南昆明 650228

收稿日期:2024-12-20 修回日期:2025-02-12 出版日期:2026-03-25 发布日期:2026-01-29
通信作者: *刘永超(1992—),男,副研究员,主要从事稀有金属成矿模拟实验研究。E-mail: yongchao.liu@cags.ac.cn
作者简介:刘强(1994—),男,博士,矿物学、岩石学、矿床学专业。E-mail: 931496643@qq.com
基金资助:
国家自然科学基金项目(U2444204);国家自然科学基金项目(42330806);国家自然科学基金项目(42202098);国家重点研发计划项目(2024YFC2909300);中国地质科学院基本科研业务费重点项目(JKYZD202315);中国地质科学院基本科研业务费重点项目(JKYQN202327)

Eucryptite formation in granitic pegmatites: Insights from in situ experiments

LIU Qiang¹^,²^,³(), LI Jiankang¹, LIU Yongchao¹^,^*()

1. MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
2. School of Earth and Space Sciences, Peking University, Beijing 100871, China
3. Yunnan Energy Investment Group Co., Ltd, Kunming 650228, China

Received:2024-12-20 Revised:2025-02-12 Online:2026-03-25 Published:2026-01-29

摘要/Abstract

摘要：

锂霞石是富锂伟晶岩中的主要锂铝硅酸盐矿物之一,目前对其形成机制仍不清楚。本文利用热液金刚石压腔,结合激光拉曼,通过原位观测高温高压实验,系统探究了锂霞石在花岗伟晶岩体系中的形成机制。实验结果表明,在石英饱和条件下,锂霞石在250~300 ℃、244~343 MPa条件下便失稳,与石英反应,形成锂辉石。对比之下,在石英不饱和体系,锂霞石可以在高达695 ℃、954 MPa条件下结晶和保持稳定。另外,实验结果显示热液交代锂辉石形成锂霞石的反应需要热液本身具有较高的锂活度,pH偏碱性条件有利于反应的快速发生。本文提出,锂霞石可归类为硅不饱和矿物,这解释了锂霞石在花岗伟晶岩高硅体系产出稀少的原因。“锂霞石+石英共生集合体”形成于低温低压条件,代表锂辉石等锂铝硅酸盐矿物经历退变质等化学分解的产物;而“锂霞石细脉”“锂霞石+钠长石共生集合体”“锂霞石结核体”等可以形成于较高温度压力条件,在矿物裂隙等局部硅不饱和环境,锂霞石从灌入的富锂流体中直接结晶或形成于热液交代锂辉石等原生矿物过程。本文强调,锂霞石可以在较广的温度压力条件下形成,根据锂霞石的出现来约束富锂伟晶岩成岩成矿p-T-x演化轨迹时需结合锂霞石的赋存状态。

关键词: 锂霞石, 锂辉石, 花岗伟晶岩, 交代反应, 高温高压实验

Abstract:

Eucryptite is one of the main lithium aluminosilicates in lithium-rich granitic pegmatites, yet its origin remains unclear. This study investigates the formation of eucryptite in granitic pegmatites through in situ high-temperature and high-pressure experiments using a hydrothermal diamond-anvil cell and Raman spectroscopy. The experimental results show that under quartz-saturated conditions, eucryptite becomes unstable and reacts with quartz to form spodumene at 250-300 ℃ and 244-343 MPa. In contrast, under quartz-undersaturated conditions, eucryptite can crystallize and remain stable at temperatures and pressures up to 695 ℃ and 954 MPa. Furthermore, the experimental results reveal that hydrothermal alteration of spodumene to eucryptite requires fluids with high lithium activities and that alkaline pH conditions accelerate the reaction. We propose that eucryptite can be classified as a silica-undersaturated mineral, which explains its rarity in granitic pegmatites. The eucryptite+quartz assemblage forms under low-temperature and low-pressure conditions, resulting from retrograde decomposition of lithium aluminosilicates, e.g., spodumene. In contrast, “eucryptite vein”, “eucryptite+albite” assemblage, and “eucryptite nodule” can form under relatively high-temperature and high-pressure conditions. In local silica-undersaturated environments, e.g., mineral fractures, eucryptite crystallizes directly from lithium-rich fluids or from hydrothermal alteration of primary minerals, e.g., spodumene. Our study demonstrates that eucryptite can form under a wide range of temperature and pressure conditions. Therefore, caution is required when using its occurrence for thermobarometric estimates of Li-rich pegmatite p-T-x evolution; its specific mode of occurrence must be taken into account.

Key words: eucryptite, spodumene, granitic pegmatite, metasomatism, high-temperature and high-pressure experiments

中图分类号:

P579

刘强, 李建康, 刘永超. 花岗伟晶岩中锂霞石形成机制的实验研究[J]. 地学前缘, 2026, 33(2): 27-39.

LIU Qiang, LI Jiankang, LIU Yongchao. Eucryptite formation in granitic pegmatites: Insights from in situ experiments[J]. Earth Science Frontiers, 2026, 33(2): 27-39.

图/表 14

图1 花岗伟晶中锂霞石的产出特征 a—葡萄牙Covas de Barroso地区伟晶岩中“锂霞石微细脉”充填于锂辉石和透锂长石裂隙中(引自文献[5]);b—美国Harding伟晶岩中“锂霞石+石英集合体”完全取代锂辉石(引自文献[7]);c—美国White Picacho地区伟晶岩中“锂霞石+钠长石共生集合体”充填于锂辉石裂隙(引自文献[8]);d—芬兰Haapaluoma伟晶岩中发育“锂霞石结核体” (引自文献[10])。

Fig.1 Eucryptite occurrences in granite pegmatites. a adapted from [5], b adapted from [7], c adapted from [8], d adapted from [10].

图2 锂铝硅酸盐矿物相图(据文献[15]修改)

Fig.2 The lithium aluminosilicate phase diagram. Modified after [15].

表1 实验条件和产物

Table 1 Experimental conditions and products

序号	初始物质	T_HDAC/℃	T_target/℃	p_target/MPa	恒温时间/h	实验产物
1	LiAlSiO₄ gel+H₂O	123/154	695^*	954		Ecp
2	Ecp+H₂O	195/184	350 400 500	280 365 533	5 11 2	Ecp Ecp Ecp
3	Ecp+Qz+H₂O	176/117	250 300 350	244 343 441	9 12 11	Ecp Ecp, Spd Ecp, Spd
4	LiAlSi₂O₆ gel+Li₂CO₃+H₂O	191/153	550	713	7	Ecp, Spd
5	Spd+NaCl (1 mol/L)	203/178 336/203	350 450 550	294 466 555	21 9 18	Anl, Spd Jd, Spd Nph, Spd
6	Spd+LiCl (0.5 mol/L)+NaCl (0.5 mol/L)	187/189	350 450	267 436	10 16	Spd Spd, Anl, Li-met
7	Spd+LiCl (0.9 mol/L)+NaCl (0.1 mol/L)	276/248	350 450	144 282	20 97	Spd Ecp, Spd, Li-met
8	Spd+Li₂CO₃+H₂O	152/314	350	44	27	Ecp, Spd
9	Spd+Li₂CO₃+H₂O	187/148	350 450 550	366 550 729	9 5 8	Spd Spd Ecp, Spd

图3 LiAlSiO4凝胶+H2O体系实验样品腔显微照片(实验1) a—室温下,封装好的样品腔由LiAlSiO4凝胶、水和气泡组成;b—在以10 ℃/min降温过程中,锂霞石在695 ℃时开始结晶,在635 ℃时停止生长。

Fig.3 Photographs of sample chamber in the LiAlSiO4 gel+H2O experiment (run 1)

图4 实验中形成的矿物拉曼光谱 a—LiAlSiO4+H2O体系(实验1)、Spd+LiCl (0.9 mol/L)+NaCl (0.1 mol/L)体系(实验7)、Spd+Li2CO3+H2O体系(实验9)实验形成的锂霞石拉曼光谱;b—Spd+Li2CO3+H2O体系(实验8)中形成的锂辉石拉曼光谱;c—Spd+NaCl (1 mol/L) 体系(实验5)中形成方沸石、硬玉和霞石的拉曼光谱。

Fig.4 Raman spectra of minerals formed in the experiments

图5 锂霞石+H2O体系实验样品腔显微照片(实验2) a—室温下,封装好的样品腔包含锂霞石、水和气泡;b—在500 ℃恒温过程中,锂霞石发生了溶解。

Fig.5 Photographs of sample chamber in the eucryptite+H2O experiment (run 2)

图6 锂霞石+石英+H2O体系实验样品腔显微照片(实验3) a—室温下,封装的样品腔由锂霞石、石英、水和气泡组成;b-d—在250、300和350 ℃依次进行恒温过程中,锂霞石发生分解,有锂辉石形成。

Fig.6 Photographs of sample chamber in the eucryptite+quartz+H2O experiment (run 3)

图7 LiAlSi2O6 凝胶+Li2CO3+H2O体系实验样品腔显微照片(实验4) a—室温下,封装好的样品腔由LiAlSi2O6凝胶、Li2CO3固相、水溶液和气泡组成;b—在550 ℃恒温过程中,锂辉石和锂霞石先后结晶析出。

Fig.7 Photographs of sample chamber in the LiAlSi2O6 gel+Li2CO3+H2O experiment (run 4)

图8 锂辉石+1 mol/L NaCl体系实验样品腔显微照片(实验5) a—室温下,封装的样品腔包含锂辉石、NaCl水溶液和气泡;b—在350 ℃恒温时,锂辉石部分溶解,方沸石结晶;c—在450 ℃恒温时,方沸石完全溶解,硬玉结晶;d—在550 ℃恒温时,硬玉分解,霞石结晶。

Fig.8 Photographs of sample chamber in the spodumene+1mol/L NaCl experiment (run 5)

图9 锂辉石+0.5 mol/L LiCl+0.5 mol/L NaCl体系实验样品腔显微照片(实验6) a—室温下,封装的样品腔包含锂辉石、NaCl+LiCl溶液和气泡;b—450 ℃恒温过程中锂辉石发生部分溶解,有锂硅酸盐和方沸石结晶。

Fig.9 Photographs of sample chamber in the spodumene+0.5 mol/L LiCl+0.5 mol/L NaCl experiment (run 6)

图10 锂辉石+0.9 mol/L LiCl+0.1 mol/L NaCl体系实验样品腔显微照片(实验7) a—室温下封装好的样品腔包含锂辉石、NaCl+LiCl溶液和气泡;b—450 ℃恒温时锂辉石部分溶解,生成锂硅酸盐和锂霞石。

Fig.10 Photographs of the sample chamber in spodumene+0.9 mol/L LiCl+0.1mol/L NaCl experiment (run 7)

表2 实验产物电子探针成分分析结果

Table 2 Analytical results of EPMA on experiment products

实验编号	w_B/%
实验编号	SiO₂	Al₂O₃	Na₂O	K₂O	CaO	MgO	MnO	FeO^t	TiO₂	P₂O₅	F	总量
实验7(n=5)	47.62 (0.64)	39.70 (0.65)	0.01 (0.01)	0.01 (0.01)	0.01 (0.01)	<0.01 (0.01)	<0.01 (0.01)	0.02 (0.02)	0.01 (0.02)	<0.01 (<0.01)	0.02 (0.03)	87.41 (0.50)
实验9(n=5)	49.99 (1.06)	38.26 (1.11)	0.08 (0.06)	0.13 (0.03)	0.02 (0.01)	<0.01 (<0.01)	<0.01 (<0.01)	<0.01 (<0.01)	0.01 (0.01)	0.01 (0.01)	0.02 (0.03)	87.52 (1.87)
引自文献[10]	51.74	36.76	0.26	0.16	0.30	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	89.22
引自文献[25]	47.70	40.35	0.01	b.d.l.	0.02	b.d.l.	b.d.l.	b.d.l.	n.d.	b.d.l.	n.d.	88.08

图11 锂辉石+Li2CO3+H2O体系实验样品腔显微照片(实验8和9) 实验8:a—室温下,封装好的样品腔中包含锂辉石、碳酸锂固相和气泡;b—在350 ℃恒温过程中,锂辉石部分溶解,锂霞石结晶;实验9:c—室温下装载的样品腔由锂辉石、碳酸锂溶液和气泡组成;d—在600 ℃恒温结束后,降温过程中,温度降至514 ℃时,锂霞石结晶。

Fig.11 Photographs of the sample chamber in spodumene+Li2CO3+H2O experiments (runs 8 and 9)

图12 log10 a S i O 2-log10( a N a +/ a L i +)中相图展示锂霞石在450 ℃、400 MPa的稳定域

Fig.12 Diagram of log10 a S i O 2-log10( a N a +/ a L i +) showing the stability of eucryptite at 450 ℃, 400 MPa

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花岗伟晶岩中锂霞石形成机制的实验研究

Eucryptite formation in granitic pegmatites: Insights from in situ experiments

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