Petrologic and isotope evidence for crustal source of ore-bearing Suwalki Anorthosites, Poland

摘要

The magmatic Fe-Ti-V deposit in the Suwalki Anorthosite Massif (SAM), discovered in early 60-ties, is the largest deposit of iron and titanium in Poland. The SAM belongs to bigger W-E trending Proterozoic magmatic terrane called Mazury Complex. Ilmenite and magnetite are widespread ore-minerals with subordinate quantities (1-3% of vol.) of Fe, Cu, Ni, Co sulfides in SAM rocks. Ore minerals form large ore bodies in Krzemianka, Udryn, Jeleniewo and Jezioro Okragte ore fields with total documented reserves of abount 1.5 bilion tons of titanomagnetite ores grading (in wt %) 27% Fe, 7% TiO_2 and 0,3% V_2O_5. Petrographic and geochemical study of main, trace, ultratrace elements and isotopic characteristics (E_(Nd), I_(Sr), γ_(Os) and δ ~(18)O ) of SAM rocks points towards the lower, mafic crust, close to mantle/crust boundary as the most probable source of the rocks. The Re-Os ages on magnetite and sulfides have yielded 1559+-37 Ma for Krzemianka and Jezioro Okragle and 1556+-94 Ma for Udryn deposit.