| 莫桑比克含铜锂电气石矿物化学特征与产地示踪 |
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| 引用本文：徐立国,吕林素,熊杰,周振华,张勇,徐明旺.2026.莫桑比克含铜锂电气石矿物化学特征与产地示踪[J].地球学报,47(5):960-970. |
| DOI：10.3975/cagsb.2026.082503 |
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| 中文摘要:含铜锂电气石(帕拉伊巴碧玺)的产地溯源是宝石检测的核心难题, 现有判别方法多依赖LA-ICP-MS, 难以在常规实验室普及。本文以莫桑比克Alto Ligonha伟晶岩带7件不同色系的含铜锂电气石为研究对象, 通过显微包裹体观察并开展EPMA、FTIR、Raman及UV-Vis系统测试, 遵循IMA规范开展晶体化学式计算与种属判定。样品为富水碱性锂电气石(锂电气石指数>90%), 整体具高Li、极低Fe-Ti特征。颜色由Cu2+和Mn3+主导控制: Cu2+的d–d跃迁(~680 nm宽带)主导蓝、绿色调(蓝色系色调与饱和度受Mn3?谱系调控), 绿色系成因分异——电光绿色叠加Mn2+–Ti4+价间电荷转移(IVCT)削截; Mn3?的~500 nm与 ~535 nm双峰(Jahn–Teller分裂)主导红、紫色调并掩蔽Cu2?的蓝绿色调; Cu/(Cu+Mn)比值可表征颜色调控趋势。基于Mn3+谱系存留判据并结合完好的原生包裹体(未见热处理爆裂迹象)特征, 7件样品中4件未经明显热处理、1件倾向未经、1件暂无法裁定(另1件贫Mn样品不适用本判据), 且均不排除未留下可检测痕迹的低温处理。基于产地地球化学背景提出的Cu/(TFe+Ti)比值, 对莫桑比克样品的判别符合率(约88.9%)远高于基于EPMA数据的传统Zn/Cu判据(20%); EPMA结合该比值可为莫桑比克与巴西、尼日利亚产地的含铜锂电气石提供快速初步产地判别方法。研究为含铜锂电气石的常规检测、热处理判别与产地溯源提供了技术支撑。 |
| 中文关键词:帕拉伊巴碧玺 颜色成因 热处理判别 产地溯源 Cu/(TFe+Ti)比值 电子探针 莫桑比克 |
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| Mineral Chemistry Characteristics and Origin Tracing of Copper-bearing Elbaite Tourmaline from Mozambique |
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| Abstract:Tracing the origin of copper-bearing elbaite tourmaline (commercially known as Paraíba tourmaline) is a critical challenge in gemstone testing; existing discrimination methods mostly rely on LA-ICP-MS, which is difficult to implement in conventional laboratories. In this study, seven copper-bearing elbaite tourmaline samples of different color series from the Alto Ligonha pegmatite belt in Mozambique were systematically investigated using microscopic inclusion observation, EPMA, FTIR, Raman spectroscopy, and UV–Vis spectroscopy. Following the IMA nomenclature, crystal-chemical formulas were calculated and species identification was performed. The samples are water-rich alkaline-group elbaite tourmaline with elbaite indices exceeding 90%, overall characterized by high Li and extremely low Fe–Ti contents. The colors are dominantly controlled by Cu2? and Mn3?: Cu2? d–d transitions (~680 nm broad band) dominate the blue–green hues, with the hue and saturation of the blue series modulated by the Mn3?-related absorption; the green series is genetically divergent, with the electric-green color involving superimposed Mn2?–Ti4? intervalence charge transfer (IVCT) truncation; the Mn3? double peaks at ~500 nm and ~535 nm (Jahn–Teller splitting) for red–purple hues and masks the Cu2?-related blue–green coloration, with the Cu/(Cu+Mn) ratio effectively reflecting the color regulation trend. Based on the Mn3? spectral-retention criteria combined with well-preserved primary inclusions (showing no decrepitation cracks or other thermal-alteration features), four of the seven samples show no obvious heat treatment, one is provisionally assigned as untreated, one remains inconclusive, and one Mn-poor sample is inapplicable to this criterion; however, all samples cannot exclude the possibility of low-temperature treatment without detectable traces. The Cu/(TFe+Ti) ratio, proposed on the basis of the geochemical backgrounds of the three major origins, yields a discrimination agreement rate of approximately 88.9% for the Mozambique samples, far exceeding the 20% obtained with the traditional Zn/Cu criterion applied to EPMA data; EPMA combined with this ratio offers a rapid, preliminary method for origin discrimination of copper-bearing elbaite tourmalines from Mozambique, Brazil, and Nigeria. This study provides a low-cost and accessible technical support for routine testing, heat treatment identification, and geographic origin tracing of copper-bearing elbaite tourmaline. |
| keywords:Paraíba tourmaline color origin heat treatment identification origin tracing Cu/(TFe+Ti) ratio electron probe Mozambique |
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