巴基斯坦明格拉地区祖母绿的化学成分分析及其成因意义

doi:10.19657/j.geoscience.1000-8527.2025.008

摘要/Abstract

摘要：

巴基斯坦斯瓦特地区的祖母绿因其独特的色泽和优异的晶体品质而备受关注,但该区明格拉祖母绿的化学成分尚未被系统研究。本研究采用电子探针显微分析(EMPA)和激光剥蚀电感耦合等离子质谱(LA-ICP-MS)技术,对明格拉矿床的祖母绿样品进行了系统的化学成分分析,旨在探讨其化学成分并揭示其形成过程中的地质环境影响。结果显示,明格拉祖母绿的类质同象替代程度平均为12.79%,主要发生在四面体T2位的铍(Be),归属于“四面体型”祖母绿。同时,其通道结构中碱金属离子的含量丰富,H₂O含量估算在2.28%至2.41%之间。值得注意的是,明格拉祖母绿在Cr-V含量图中显示,Cr含量均高于4500×10^-6,明显高于其他国家产地的祖母绿。通过对铷(Rb)、铯(Cs)、钪(Sc)和锂(Li)等微量元素的对比分析,为祖母绿的产地鉴定提供了科学依据和新视角。

关键词: 巴基斯坦, 明格拉, 祖母绿, 化学成分, 微量元素

Abstract:

The emeralds from the Swat region of Pakistan are notable for their unique color and exceptional crystal quality; however, the chemical composition of Mingora emeralds in this area has not been systematically studied. This research employs Electron Probe Microanalysis (EMPA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) techniques to conduct a comprehensive chemical composition analysis of emerald samples from the Mingora deposit, aiming to explore their chemical properties and uncover the geological environmental influences during their formation. The results indicate that the average degree of isomorphous substitution in Mingora emeralds is 12.79%, primarily occurring at the tetrahedral T2 site of beryllium (Be), classifying them as “tetrahedral-type” emeralds. Additionally, the channel structure of these emeralds contains a rich concentration of alkali metal ions, with estimated H₂O content ranging from 2.28% to 2.41%. Notably, the projection of Mingora emeralds in the Cr-V content diagram shows that the chromium (Cr) content is consistently higher than 4,500×10^-6, which is significantly higher than that of emeralds from other global sources. Through comparative analysis of trace elements such as rubidium (Rb), cesium (Cs), scandium (Sc), and lithium (Li), this study provides essential scientific supports and new insights for the provenance determination of emeralds.

Key words: Pakistan, Mingora, Emerald, chemical composition, trace element

中图分类号:

P575.3

赵红星, 蔡景坤, 许迎新, 李雨璇, 刘迎新. 巴基斯坦明格拉地区祖母绿的化学成分分析及其成因意义[J]. 现代地质, 2025, 39(01): 209-223.

ZHAO Hongxing, CAI Jingkun, XU Yingxin, LI Yuxuan, LIU Yingxin. Chemical Composition Analysis of Emeralds from the Mingora Region, Pakistan: Insights into Formation Mechanisms[J]. Geoscience, 2025, 39(01): 209-223.

图/表 17

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样本	ME-01	ME-02	ME-03	ME-04	ME-05	ME-06	ME-07	ME-08
颜色	浅绿色	浅绿色	浅绿色	绿色	绿色	深绿色	深绿色	深绿色
Ne	1.588	1.583	1.588	—	1.589	1.585	1.583	1.583
No	1.600	1.588	1.600	—	1.592	1.599	1.586	1.589
DR	0.002	0.005	0.002	—	0.003	0.014	0.003	0.006
SG	2.69	2.86	2.74	2.77	2.79	2.76	2.73	2.79

样本	ME-01	ME-02	ME-03	ME-04	ME-05	ME-06	ME-07	ME-08
颜色	浅绿色	浅绿色	浅绿色	绿色	绿色	深绿色	深绿色	深绿色
Ne	1.588	1.583	1.588	—	1.589	1.585	1.583	1.583
No	1.600	1.588	1.600	—	1.592	1.599	1.586	1.589
DR	0.002	0.005	0.002	—	0.003	0.014	0.003	0.006
SG	2.69	2.86	2.74	2.77	2.79	2.76	2.73	2.79

样品	Na₂O	K₂O		Cs₂O		MgO		CaO		TiO₂		P₂O₅		V₂O₃		Cr₂O₃		MnO		FeO		Al₂O₃		SiO₂		BeO	Total
ME-01	1.38	0.02		0.11		1.34		0.02		0.00		0.03		0.32		0.51		0.02		0.48		17.14		64.25		13.61	99.23
ME-02	1.44	0.07		0.15		1.34		0.06		0.00		0.01		0.31		0.50		0.00		0.65		16.74		64.66		12.76	98.68
ME-03	1.50	0.06		0.07		1.35		0.03		0.04		0.00		0.31		0.54		0.02		0.50		17.06		64.63		12.58	98.69
ME-04	1.37	0.04		0.06		1.33		0.03		0.00		0.01		0.33		0.57		0.00		0.04		17.46		65.18		13.20	99.61
ME-05	1.33	0.04		0.03		1.34		0.00		0.01		0.01		0.33		0.53		0.05		0.07		17.55		64.69		13.85	99.83
ME-06	1.34	0.02		0.06		1.33		0.00		0.01		0.01		0.38		0.52		0.00		0.07		17.44		65.64		12.83	99.66
ME-07	1.18	0.03		0.04		1.30		0.00		0.00		0.01		0.30		0.51		0.05		0.14		17.14		64.65		14.17	99.51
ME-08	1.35	0.03		0.08		1.33		0.00		0.00		0.00		0.37		0.52		0.01		0.56		17.05		65.22		13.14	99.65
平均值	1.36	0.04		0.07		1.33		0.02		0.01		0.01		0.33		0.52		0.02		0.31		17.20		64.87		13.27	99.36
样品	Na⁺		K⁺		Cs⁺		Mg²⁺		Ca²⁺		Ti⁴⁺		P⁵⁺		V³⁺		Cr³⁺		Mn²⁺		Fe²⁺		Al³⁺		Si⁴⁺			Be²⁺
ME-01	0.246		0.003		0.004		0.183		0.001		-		0.002		0.024		0.037		0.001		0.037		1.852		5.890			2.996
ME-02	0.258		0.008		0.006		0.185		0.006		-		0.001		0.023		0.037		-		0.050		1.825		5.980			2.834
ME-03	0.268		0.007		0.003		0.187		0.003		0.001		-		0.023		0.039		0.002		0.039		1.859		5.977			2.794
ME-04	0.242		0.004		0.002		0.181		0.003		-		0.001		0.024		0.041		0		0.003		1.876		5.942			2.891
ME-05	0.235		0.005		0.001		0.181		-		-		-		0.024		0.038		0.004		0.005		1.879		5.877			3.023
ME-06	0.237		0.003		0.002		0.181		-		-		0.001		0.028		0.037		-		0.005		1.874		5.985			2.811
ME-07	0.209		0.004		0.001		0.176		-		-		0.001		0.022		0.036		0.004		0.011		1.837		5.881			3.096
ME-08	0.240		0.004		0.003		0.181		-		-		-		0.027		0.037		-		0.043		1.836		5.959			2.884
平均值	0.242		0.005		0.003		0.182		0.002		-		0.001		0.024		0.038		0.001		0.024		1.855		5.936			2.916

样品	Na₂O	K₂O		Cs₂O		MgO		CaO		TiO₂		P₂O₅		V₂O₃		Cr₂O₃		MnO		FeO		Al₂O₃		SiO₂		BeO	Total
ME-01	1.38	0.02		0.11		1.34		0.02		0.00		0.03		0.32		0.51		0.02		0.48		17.14		64.25		13.61	99.23
ME-02	1.44	0.07		0.15		1.34		0.06		0.00		0.01		0.31		0.50		0.00		0.65		16.74		64.66		12.76	98.68
ME-03	1.50	0.06		0.07		1.35		0.03		0.04		0.00		0.31		0.54		0.02		0.50		17.06		64.63		12.58	98.69
ME-04	1.37	0.04		0.06		1.33		0.03		0.00		0.01		0.33		0.57		0.00		0.04		17.46		65.18		13.20	99.61
ME-05	1.33	0.04		0.03		1.34		0.00		0.01		0.01		0.33		0.53		0.05		0.07		17.55		64.69		13.85	99.83
ME-06	1.34	0.02		0.06		1.33		0.00		0.01		0.01		0.38		0.52		0.00		0.07		17.44		65.64		12.83	99.66
ME-07	1.18	0.03		0.04		1.30		0.00		0.00		0.01		0.30		0.51		0.05		0.14		17.14		64.65		14.17	99.51
ME-08	1.35	0.03		0.08		1.33		0.00		0.00		0.00		0.37		0.52		0.01		0.56		17.05		65.22		13.14	99.65
平均值	1.36	0.04		0.07		1.33		0.02		0.01		0.01		0.33		0.52		0.02		0.31		17.20		64.87		13.27	99.36
样品	Na⁺		K⁺		Cs⁺		Mg²⁺		Ca²⁺		Ti⁴⁺		P⁵⁺		V³⁺		Cr³⁺		Mn²⁺		Fe²⁺		Al³⁺		Si⁴⁺			Be²⁺
ME-01	0.246		0.003		0.004		0.183		0.001		-		0.002		0.024		0.037		0.001		0.037		1.852		5.890			2.996
ME-02	0.258		0.008		0.006		0.185		0.006		-		0.001		0.023		0.037		-		0.050		1.825		5.980			2.834
ME-03	0.268		0.007		0.003		0.187		0.003		0.001		-		0.023		0.039		0.002		0.039		1.859		5.977			2.794
ME-04	0.242		0.004		0.002		0.181		0.003		-		0.001		0.024		0.041		0		0.003		1.876		5.942			2.891
ME-05	0.235		0.005		0.001		0.181		-		-		-		0.024		0.038		0.004		0.005		1.879		5.877			3.023
ME-06	0.237		0.003		0.002		0.181		-		-		0.001		0.028		0.037		-		0.005		1.874		5.985			2.811
ME-07	0.209		0.004		0.001		0.176		-		-		0.001		0.022		0.036		0.004		0.011		1.837		5.881			3.096
ME-08	0.240		0.004		0.003		0.181		-		-		-		0.027		0.037		-		0.043		1.836		5.959			2.884
平均值	0.242		0.005		0.003		0.182		0.002		-		0.001		0.024		0.038		0.001		0.024		1.855		5.936			2.916

10^-6	ME-02	ME-03	ME-04	ME-05	ME-06	ME-07	ME-08	平均值
Li	406.092	412.057	668.929	208.514	321.818	257.364	344.145	374.132
Be	62681.734	55852.584	60428.915	53482.591	56613.642	57312.628	55799.814	57453.130
Na	18017.527	15564.226	18341.198	12751.093	14753.056	18582.547	15410.915	16202.924
K	-	-	61.356	44.589	-	102.015	44.129	36.013
Mg	19852.577	17187.883	20261.544	13842.919	16460.485	18361.850	16430.799	17485.437
Ca	701.771	243.028	-	329.012	514.024	349.524	313.578	350.134
Al	90790.700	83627.802	87548.355	76869.164	79560.711	78997.052	79798.997	82456.111
Si	267653.813	291009.260	274050.682	297681.156	288251.097	284641.439	290254.605	284791.722
Ti	44.797	-	809.506	7.424	46.745	53.712	43.088	143.610
Sc	1450.996	175.236	545.874	452.541	957.437	1433.636	804.146	831.409
V	783.112	243.856	684.005	130.738	650.461	713.564	447.744	521.926
Cr	5544.258	4978.415	6151.801	8059.077	13208.353	10250.583	11138.985	8475.925
Mn	9.874	8.027	2.459	0.468	5.292	5.360	4.395	5.125
Fe	8137.899	4172.877	5715.235	11632.990	3896.542	5569.400	4257.951	6197.556
Cs	198.909	140.905	665.849	238.524	75.717	104.661	93.495	216.866
Ni	14.703	15.699	34.041	9.549	5.041	9.816	8.459	13.901
Cu	0.293	-	0.326	0.295	2.181	0.346	-	0.492
Zn	1.445	4.196	5.010	2.752	3.425	2.836	3.380	3.292
Ga	9.956	7.046	8.344	3.633	8.388	7.444	8.319	7.590
Ge	-	-	1.289	0.258	1.139	2.785	-	0.782
Rb	10.334	12.346	16.295	5.303	11.527	14.016	10.427	11.464
Sn	0.831	0.684	3.984	2.960	3.738	2.042	2.890	2.447
Nb	0.105	0.161	0.117	0.053	0.071	0.109	0.116	0.105