# Trace Elements and Mineralogy of Upper Permian (Zechstein)
## 7 Conclusions  
Complex studies of the Upper Permian (Zechstein, PZ1, PZ2, and PZ3 cyclothems) potash-bearing deposits (K-Mg chlorides and sulphates) in Poland enabled the first complete examination of the characteristics of the trace element geochemistry and mineral composition of these rocks in the eastern part of the Southern Permian Basin. These studies included geochemical (content of selected trace elements) and mineral composition (XRD and petrographic optic and SEM) analyses of 308 rock samples, taken mainly from four salt domes in central Poland (299 samples, PZ2 and PZ3 cyclothems) and several (9 samples) from the stratiform evaporites of PZ1 cyclothem in northern Poland. Mineral composition studies documented a varied frequency of 30 detected minerals and three mineral groups. The most frequent minerals (frequency 10-20%) are halite, kieserite, sylvite, and anhydrite; the less frequent (5-10%) are carallite, kainite, and sylvite. Quite rarely (1-5%), bischofite, calcite, langbeinite, magnesite, quartz, talc, pyrite and minerals of the chlorite group are found. Other detected minerals, such as berlinite, bloedite, cronstedite, gypsum, hexahydrite, hexahydroborite, leonite, loewite, nantokite, picornerite, spodumene, starkeyite, trevorite, boracite, hydrotalcite, goethite, celestite, hematite, carbonates, and clay minerals occur sporadically. Dominant mineral components of the K-Mg sulphates (polyhalite) of PZ1 cyclothem are anhydrite and polyhalite. For K-Mg salts of PZ2 cyclothem, the most common are halite, sylvite, kieserite, and anhydrite, but for such deposits of PZ3 cyclothem, halite, carnallite, kieserite, and anhydrite are most common. Content of selected trace elements (Ag, As, Ba, Be, Br, Ce, Cd, Co, Cr, Cs, Cu, I, Fe, Ga, La, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ti, Tl, U, V, and Zn) was defined in 308 rock samples. For some samples, content of insoluble (in water) residuum was also detected. K-Mg sulphates (polyhalite) of PZ1 cyclothem contain (arithmetic mean and median) up to 13 mg/kg of Ba, Cu, Mn, Ni, Rb, Mo, Ce, Pb, Ti, V, U, and Zn; higher is the content of Li (20-26 mg/kg), Fe (29-33 mg/kg), and Sr (723-1075 mg/kg). Chloride K-Mg salts of PZ2 cyclothem characterise a relatively low (up to 6 mg/kg) content of As, Ba, Cd, Ce, Co, Cr, Cs, Cu, Ga, I, La, Li, Mn, Mo, Ni, Pb, Sb, Tl, U, and V, and more common (3-24 mg/kg) are Rb, Ti and Zn, but the highest content are Br (119-259 mg/kg), Fe (100-146 mg/kg) and Sr (76-218 mg/kg). For chloride K-Mg salts of PZ3 cyclothem, the low (up to 5 mg/kg) content is typical for Ag, As, Ba, Cd, Ce, Co, Cr, Cs, Cu, Ga, La, Li, Mo, Ni, Pb, Sb, U, V, and Zn, and more common (3-25 mg/kg) are Mn, Rb and Ti, but the highest content characterises Br (151-310 mg/kg), Fe (31-231 mg/kg), and Sr (40-102 mg/kg). Relatively low content (up to 26 mg/kg) of most analysed trace elements in the studied Zechstein potash-bearing deposits in Poland--defined in accessible rock samples--eliminate them as potential source rocks for the economically profitable extraction of such required elements as Ce, Cs, La, Li, or Rb. Bromine, iron, and strontium are easily accessible from the natural brines, sulphate (gypsum and anhydrite), and ore deposits. **Author Contributions:** Conceptualization, G.C. ; methodology, G.C., H.T.-M., B.H., J.W. and T.M.P. ; validation, G.C. ; formal analysis, G.C., H.T.-M., B.H., J.W. and T.M.P. ; investigation, G.C., H.T.-M., B.H., J.W. and T.M.P. ; resources, G.C. and J.W. ; data curation, G.C., H.T.-M., B.H., J.W. and T.M.P. ; writing--original draft preparation, G.C. ; writing--review and editing, G.C and T.M.P. ; visualisation, G.C. ; supervision, T.M.P. ; project administration, G.C. ; funding acquisition, G.C. All authors have read and agreed to the published version of manuscript. The research was founded by the National Fund of Environment Protection and Water Management (Warsaw, Poland) as project no. 289/2018/Wn-07/FG-GO-DN/D. Not applicable.