Unique trace element geochemistry of pyrometamorphic apatite-supergroup minerals: a case study of fluorellestadite from burnt coal (Poland) and shale (France) post-mining waste heaps, with emphasis on boron, germanium, aluminium and titanium

Apatite-type structure is known for its flexibility towards accommodating numerous ions of different crystallographic affinities. The trace el e ment com po si tion of two sam ples of fluorellestadite from pyrometamorphic rocks (slags) of burnt waste heaps (BWH) from France (LdS) and Po land (RDT) were stud ied us ing La ser Ab la tion In duc tively Cou pled Plasma Mass Spec trom - e try. Bo ron shows an ev i dent, per sis tent en rich ment in both sam ples, with av er age/max i mum levels of 497/1040 and 49/106 ppm, re spec tively, as do mag ne sium (884/16766 and 404/6251 ppm, re spec tively) and so dium (512/697 and 249/370 ppm, re spec tively). Ger ma nium is clearly en riched in the first sam ple (29/40 ppm) and, to a lesser de gree, in the sec ond one (34 ppm on av er age). The LdS sam ple is also clearly en riched in Al (888/1238 ppm), K (385/697 ppm), Ti (515/943 ppm), V (172/347 ppm), and Cu (16/1369 ppm). The RDT sam ple is also rich in As (105/120 ppm) and Sr (1072/6592 ppm). In the REE pat tern of both sam ples, Nd dom i nates, with re spec tive Nd/ELREE and Nd/(Ce+La) val ues of 0.43 and 0.90; and 0.37 and 0.66. From high est to lower av er age con cen tra tions, alu minium, mag ne sium, ti ta nium, bo ron, po tas sium and ger ma nium may be es sen tial sub stitu ents in the BWH apatites.