Organic geochemical records of hydrotermal alteration at Idrija mercury deposit, Slovenia

Abstract

A combined molecular and stable isotopes (C, N) investigation of the organic matter associated to the Idrija mercury deposit is being used to track the pathway of the mineralizing hydrothermal fluids and their interaction with the organic matter. The studied samples include regional barren rocks, and host rocks and ore from the mine. The RockEval parameters indicate that the organic matter disseminated in regional and mine rocks is mature to post mature. The bitumens from mineralized samples are depleted in aliphatic hydrocarbons and enriched in polycyclic aromatic hydrocarbons (PAH), aromatic sulfur compounds (S-PAH) and hydrogenated PAH. The isotopic compositions of kerogens, bitumens, and individual hydrocarbons point to thermal and oxidative degradation of indigenous and migrated bitumens during mineralization and later evolution of the Idrija deposit. Kratka vsebinaKombinirana molekularna in stabilno izotopska (C, N) raziskava organske snovi Idrijskega 'ivosrebrovega rudi{~a je bila uporabljena za sledenje poti hidrotermalnih raztopin in njihovega vpliva na organsko snov. Preiskani vzorci zajemajo regionalne kamnine ter prikamnino in rudo iz Idrijskega rudnika. Parametri Rock-Eval ka'ejo na zrelost do prezrelost organske snovi, ki je razpr{ena v idrijskih in okolnih kamninah. Bitumni iz mineraliziranih vzorcev nakazujejo zmanj{ane vsebnosti nasi~enih ogljikovodikov ter pove~ane koncentracije policikli~nih aromatskih ogljikovodikov (PAH), aromatskih 'veplovih spojin (S-PAH) in hidrogeniranih PAH. Izotopske sestave kerogenov, bitumnov in posameznih ogljikovodikov pri~ajo o termi~ni in oksidativni degradaciji prvotnih in migriranih bitumnov med mineralizacijo in poznej{im razvojem idrijskega rudi{~a.