Linear Correlation of Ba and Eu Contents by Hydrothermal Activities: A Case Study in the Hetang Formation, South China

Abstract

A significant linear correlation between Ba and Eu contents has been observed in a set of mudrock formations in the lower Cambrian Hetang Formation in South China. Combined with petrographic features and reinvestigation of published data obtained from the same laboratory, the analytical interference of Ba can be excluded as a main factor of this correlation. Electron microprobe analyses (EMPA) have indicated that Ba-rich minerals (hyalophane and cymrite) precipitated from hydrothermal fluids account for the total Ba content. It is evident that significant contribution of both Ba and Eu from hydrothermal fluids is the cause of this linear relationship, while this coexistence is ultimately controlled by their similar chemical properties and abundances in rock sequences along the fluid path. This interpretation was supported by similar linear Ba-Eu correlations retrieved from barite-bearing chert in another area of the Yangtze platform during the same geological period. Therefore, linear Ba-Eu correlations may be more common than previously thought in this area, where hydrothermal activities were active during the specific time interval.

Threshold Value Determination Using Machine Learning Algorithms for Ba Interference with Eu in Coal and Coal Combustion Products by ICP-MS

“…Unlike other ICP-Q-MS data which were obtained based on non-separation between Ba and Eu in solutions digested from solid samples (e.g., coal samples in the U.S. Geological Survey's WoCQI database, Palmer et al [37], and in other numerous published papers, for example but not limited to references [38][39][40][41][42][43][44][45][46]), the data by Yan et al [27] provided a good opportunity for determining the threshold value using machine learning algorithms for Ba interference with Eu in coal and coal combustion products by ICP-Q-MS. However, there have been some studies to assess the interference of 135 Ba 16 O, 134 Ba 16 OH, 137 Ba 16 O, and/or 136 Ba 16 OH on 151 Eu and/or 153 Eu, e.g., determining the yield of Ba-based oxide and hydroxide ions using a single-element solution of Ba (e.g., 500 ng/mL Ba in BaCl 2 solution) and compare the yield of potential interfering irons (e.g., 135 Ba 16 O) with the Eu ions ( 151 Eu) that has the same mass number in a single-element solution of Eu [47][48][49]. A study by Dulski [48] shows that that 1000 ng/g Ba could cause 0.22 ng/g Eu.…”