LA-ICP-MS, and XRD were used to investigate representative samples of gypsum collected from four deposits, all of them of Badenian age: Cheia (Transilvanian Basin, Cluj county), Ivancauti (Moldavian Platform, Botosani county), Negresti (Moldavide, Neamt county) and Moinesti (Moldavide, Bacau county) deposits were selected. The main objective of this study consisted of a geochemical, crystallo-chemical and economical potential detailed characterization of these deposits.
Accordingly, the LA-ICP-MS permitted determining the mass fractions of 21 elements including 10 REE (La, Ce, Nd, Sm, Eu, Gd, Er, Yb and Lu), as well as of Mg, P, Ti, Fe, Ni, Sr, Y, Ba, Pb, Th and U. Their content was interpreted considering their presence in the upper continental crust (UCC), sea water and chondrites.
Concerning the investigated elements, excepting for the REE ones, the LA-ICP-MS determinations evidenced in the case of Sr and U contents comparable with the UCC ones. It worth mentioning the presence of Sr of which mass fractions of 930 ± 47 and 545 ± 100 mg/kg in the Ivancauti and Cheia samples exceeded the UCC one of 330 mg/kg by a factor up to three, in good agreement with reported data concerning the lagunar Mediterranean gypsum.
At its turn, the U showed mass fractions varying between 1.76 ± 0.94 mg/kg in the case of Moinesti deposit and 2.93 ± 0.8 mg/kg for the Cheia samples, having the same order of magnitude as the UCC one of 2.7 mg/kg. On contrary, the maximum value of Th mass fraction of 68 ± 31 mg/kg was 155 times smaller than the value reported for UCC one. By comparing the ratio of the mass fractions of Th and U in investigated samples with the same ration of the sea water, the gypsum samples ratio of 0.02 significantly overpasses the sea water ratio of 0.0015, suggesting rather a terrigenous origin.
The great variability of the mass fractions of the investigated 11 elements makes possible the discriminant analysis of their distribution by considered elements as variable and deposits as cases. Indeed, a Root 2 vs. Root 2 bi-plot evidenced the presence of four clusters, the Negresti and Moinesti ones relatively closer and differing by the Ivancauti and Cheia ones with respect of Root 1, while Root 2 discriminates only the Cheia one with respect with the other three, i.e. Ivancauti, Negresti and Moinesti.
Likely, the investigated REE distribution showed for all of them mass fractions lower with one order of magnitude and more than the corresponding UCC values, e.g., varying from 5.59 ± 2.82 mg/kg for Yb in Ivancauti samples to 0.21 ± 0.04 mg/kg in the case of Lu in Moinesti gypsum. A peculiarity which we observed for all samples consisted of positive Ce and Eu anomalies. If the Ce anomaly could be associated to an oxidative depositional medium, the positive Eu anomaly could be associated to an increased content of Sr, but these facts need more investigations to be elucidated, especially as this anomaly was evidenced for all investigated samples, regardless the deposit.