Applicability of handheld X-Ray fluorescence spectrometry in the exploration and development of carbonatite-related niobium deposits: a case study of the Aley Carbonatite, British Columbia, Canada
Applicability of handheld X-Ray fluorescence spectrometry in the exploration and development of carbonatite-related niobium deposits: a case study of the Aley Carbonatite, British Columbia, Canada
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手持式 X 射线荧光光谱仪在碳酸岩相关铌矿勘探和开发中的适用性：以加拿大不列颠哥伦比亚省 Aley Carbonatite 为例
DOI：
10.1144/geochem2012-177
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
L. Simandl
中科院分区：
文献类型：
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作者：
G. Simandl;Suzanne Paradis;R. S. Stone;R. Fajber;R. Kressall;K. Grattan;J. Crozier;L. Simandl
本研究评价了便携式(手持)X射线荧光光谱仪(PXRF)在艾利型“硬岩”(原生)碳酸盐岩型Nb矿床勘查中的适用性。评估包括：(1)选定纸浆样本的pXRF分析结果与使用传统实验室方法分析相同纸浆的结果之间的比较；(2)直接对10至15厘米长的岩芯(粉碎前)进行平均多个pXRF斑点场分析的结果与粉碎后相同岩芯的传统实验室分析结果的比较；(3)手动岩心扫描方法的结果与相应扫描断面纸浆的常规分析方法的结果比较。对大多数特种金属，如Nb(R2=0.99)、La(R2=0.97)、Ce(R2=0.67)、Y(R2=0.93)和P(R2=0.89)，纸浆上的pXRF测量结果与实验室方法有很强的相关性，而Pr和ND的R2分别为0.19和0.38。正如预期的那样，当直接在岩心上获得多个斑点读数时，样本间隔内的纹理不均匀降低了pXRF结果的质量。然而，这些数据仍然可以用来识别与碳酸岩有关的Nb(±其他特殊金属矿化)，并划定其中潜在的经济意义区域。岩心扫描减少了与SPOT分析相关的变化程度。扫描在早期勘探阶段是有用的，但提供的数据受到操作员无法保持恒定扫描速度的限制。扫描结果与实验室方法测定Nb(R2=0.88)、Th(R2=0.80)、Fe(R2=0.84)、Sr(R2=0.74)、Ba(R2=0.73)、Y(R2=0.59)和Zn(R2=0.75)相一致。La、Ce、Pr和Nd的R2值分别为0.31、0.26、0.01和0.03，表明这些元素的浓度太低，或者轻稀土元素不仅存在于铁闪锌矿、烧绿石和磷灰石的晶体结构中，而且还存在于含稀土的氟碳酸盐或锆石等少量或副矿物中，呈不规则分布。便携XRF是一种强大的工具，有助于在实地进行与勘探有关的决策，前提是如Nb等感兴趣的元素在仪器的分析范围内以浓度形式存在。PXRF岩心扫描减少了样品准备(无纸浆)的需要，可以直接在钻探现场进行，但与实验室和pXRF纸浆分析相比，数据的精密度和准确性有所降低。多点分析(无矿浆)方法有利于对未知、潜在含矿矿物的即时验证，以及分析离散的均质特征、层、脉等；但在正常情况下，这种方法在精密度和准确度方面不如矿浆分析，也不利于扫描确定岩心层段的平均品位。
This study evaluates the suitability of portable (handheld) X-Ray fluorescence spectrometry (pXRF) in the exploration for Aley-type ‘hard-rock’ (primary) carbonatite-hosted Nb deposits. The assessment consists of comparisons between: (1) results of pXRF analyses on selected pulp samples and results of analyses of the same pulps using traditional laboratory methods; (2) results of averaged, multiple pXRF spot field analyses performed directly on 10 to 15 cm long pieces of core (before pulverization) compared with those of traditional laboratory analyses of the same pieces of core after pulverization; and (3) results of a manual core scanning method compared with the results of conventional analytical methods of the pulps of the corresponding scanned sections. A strong correlation exists between pXRF measurements on pulps and laboratory methods for most specialty metals, such as Nb (r2 = 0.99), La (r2 = 0.97), Ce (r2 = 0.67), Y (r2 = 0.93), and P (r2 = 0.89); however, the values of r2 for Pr and Nd are 0.19 and 0.38, respectively. As expected, textural heterogeneities within sample intervals reduced the quality of pXRF results when multiple spot readings were taken directly on the core. Nevertheless, the data can still be used to identify carbonatite-related Nb (± other specialty metal mineralization) and delimitate potentially economically significant zones within it. The core scanning reduced the degree of variation associated with spot analyses. Scanning is useful during the early exploration stages, but provides data limited by the inability of the operator to maintain constant scanning speed. The scanning results correlate with laboratory methods for Nb (r2 = 0.88), Th (r2 = 0.80), Fe (r2 = 0.84), Sr (r2 = 0.74), Ba (r2 = 0.73), Y (r2 = 0.59), and Zn (r2 = 0.75). The values of r2 for La, Ce, Pr, and Nd were only 0.31, 0.26, 0.01 and 0.03, respectively, suggesting that concentrations of these elements were too low, and/or that the light rare earth elements (LREEs) were present not only in the crystal structure of fersmite, pyrochlore and apatite, but also in minor or accessory minerals such as REE-bearing fluorocarbonates or zircon erratically distributed throughout the core. Portable XRF is a robust tool facilitating exploration-related decision-making in the field, assuming that elements of interest such as Nb are present in concentrations within the analytical range of the instrument. The pXRF core scanning reduces the need for sample preparation (no pulps) and can be done directly on the drill-site, but the precision and accuracy of the data are reduced relative to laboratory and pXRF pulp analyses. The multiple spot analyses (no pulps) approach is good for instant verification of unknown, potentially ore-bearing minerals and for analysing discrete homogeneous features, layers, veins, etc; however, under normal circumstances this method is inferior to pulp analyses in precision and accuracy, and to scanning for determining average grade of core intervals.