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Significance of radioelements distribution in the Precambrian rocks of Jabel Sayid, western Saudi Arabia, using spectrometric and geochemical data
Resource Geology ( IF 1.1 ) Pub Date : 2020-12-15 , DOI: 10.1111/rge.12253 Hamdy H. Abd El‐Naby 1 , Yehia H. Dawood 2 , Abduallah A. Sabtan 1 , Mahmood S. Al Yamani 1
Resource Geology ( IF 1.1 ) Pub Date : 2020-12-15 , DOI: 10.1111/rge.12253 Hamdy H. Abd El‐Naby 1 , Yehia H. Dawood 2 , Abduallah A. Sabtan 1 , Mahmood S. Al Yamani 1
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In situ gamma‐ray spectrometry measurements were carried out using RS‐230 BGO spectrometer over an area of 9.4 km2. One hundred and seventy eight spectrometric points were collected along parallel profiles with spacing 325 m in the Easting X direction and Northing Y direction. The results are treated statistically to determine the minimum, maximum, arithmetic mean (X), SD (S), and coefficient of variability (CV %). The spectrometric survey revealed the presence of radioactive zones in the aplite‐pegmatite with maximum eU content of 1,550 ppm and eTh of 7,974 ppm, whereas alkali granite has an average eU content of 12 ppm and eTh of 34 ppm. Felsite has an average eU and eTh close to that of alkali granite, 11 and 32 ppm, respectively. Pegmatite veins cutting alkali granite have high values of eU and eTh, an average of 34 and 101 ppm, respectively. The metamorphosed volcanic rocks of the Mahd Group demonstrate the lowest radioactivity with an average eU content of 0.8 ppm and eTh of 1.6 ppm. These rocks partly show evidences of post‐magmatic alteration processes, for example, silicification, sericitization, and oxidation. Excluding metavolcanics, the strong positive correlation between eU and eTh for the different rock varieties reflects their geochemical coherence during magma crystallization and indicates that both elements are largely accommodated into accessory minerals and were not disturbed by alteration. The CV values of the different rock units show normal distribution, where all the percentages of CV values are less than 100, with the exception of eU of felsite that shows CV % value slightly higher than 100. The aplite‐pegmatite, alkali granite, and the associated pegmatite veins show negative value of uranium outward migration, but are still the most favorable host rocks for uranium and thorium mineralization. A tentative interpretation of such contradiction suggests that uranium is largely accommodated into accessory minerals and only limited labile uranium redistribution has occurred and uranium was precipitated in association with alteration products. This interpretation is supported by the presence of kasolite Pb(UO2)SiO4.(H2O), along the fractured zones and quartz veins in the aplite‐pegmatite. The limited uranium migration in the study area was also revealed by the low weathering rate estimated by the calculations of chemical indices of alteration.
中文翻译：
利用光谱和地球化学数据，在沙特阿拉伯西部Jabel Sayid的前寒武纪岩石中放射性元素的分布意义
使用RS‐230 BGO光谱仪在9.4 km 2的面积上进行了原位伽马射线光谱测量。沿平行剖面收集了一百七十八个光谱点，在东向X方向和北向Y方向上的间隔为325 m。对结果进行统计处理以确定最小，最大，算术平均值（X），SD（S）和变异系数（CV％）。光谱调查显示，在磷灰石-辉绿岩中存在放射性区域，最大eU含量为1,550 ppm，eTh为7,974 ppm，而碱性花岗岩的平均eU含量为12 ppm，eTh为34 ppm。铝铁矿的平均eU和eTh分别接近碱性花岗岩的eU和eTh，分别为11 ppm和32 ppm。切割碱花岗岩的伟晶岩脉具有较高的eU和eTh值，分别为34 ppm和101 ppm。Mahd组变质的火山岩表现出最低的放射性，其平均eU含量为0.8 ppm，eTh为1.6 ppm。这些岩石部分显示了岩浆后蚀变过程的证据，例如硅化作用，矿化作用和氧化作用。不包括超火山岩，不同岩石种类的eU和eTh之间的强正相关关系反映了它们在岩浆结晶过程中的地球化学相干性，并表明这两种元素在很大程度上都被包含在辅助矿物中，并且不受蚀变的干扰。不同岩石单元的CV值显示正态分布，其中所有CV值的百分比均小于100，除了铁矾土的eU值，其CV％值略高于100外。相关的伟晶岩脉显示出铀向外迁移的负值，但仍是铀和or矿化最有利的宿主岩。对这种矛盾的初步解释表明，铀主要容纳在辅助矿物中，只有有限的不稳定的铀重新分布发生，铀与蚀变产物结合而沉淀。钾长石Pb（UO）的存在为这种解释提供了支持2）SiO 4。（H 2 O），沿云母-斜辉晶岩的断裂带和石英脉。通过化学变化指数的计算得出的低风化率也揭示了研究区铀迁移的局限性。
更新日期：2020-12-15
中文翻译：
利用光谱和地球化学数据，在沙特阿拉伯西部Jabel Sayid的前寒武纪岩石中放射性元素的分布意义
使用RS‐230 BGO光谱仪在9.4 km 2的面积上进行了原位伽马射线光谱测量。沿平行剖面收集了一百七十八个光谱点，在东向X方向和北向Y方向上的间隔为325 m。对结果进行统计处理以确定最小，最大，算术平均值（X），SD（S）和变异系数（CV％）。光谱调查显示，在磷灰石-辉绿岩中存在放射性区域，最大eU含量为1,550 ppm，eTh为7,974 ppm，而碱性花岗岩的平均eU含量为12 ppm，eTh为34 ppm。铝铁矿的平均eU和eTh分别接近碱性花岗岩的eU和eTh，分别为11 ppm和32 ppm。切割碱花岗岩的伟晶岩脉具有较高的eU和eTh值，分别为34 ppm和101 ppm。Mahd组变质的火山岩表现出最低的放射性，其平均eU含量为0.8 ppm，eTh为1.6 ppm。这些岩石部分显示了岩浆后蚀变过程的证据，例如硅化作用，矿化作用和氧化作用。不包括超火山岩，不同岩石种类的eU和eTh之间的强正相关关系反映了它们在岩浆结晶过程中的地球化学相干性，并表明这两种元素在很大程度上都被包含在辅助矿物中，并且不受蚀变的干扰。不同岩石单元的CV值显示正态分布，其中所有CV值的百分比均小于100，除了铁矾土的eU值，其CV％值略高于100外。相关的伟晶岩脉显示出铀向外迁移的负值，但仍是铀和or矿化最有利的宿主岩。对这种矛盾的初步解释表明，铀主要容纳在辅助矿物中，只有有限的不稳定的铀重新分布发生，铀与蚀变产物结合而沉淀。钾长石Pb（UO）的存在为这种解释提供了支持2）SiO 4。（H 2 O），沿云母-斜辉晶岩的断裂带和石英脉。通过化学变化指数的计算得出的低风化率也揭示了研究区铀迁移的局限性。
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