Genesis of magnesite deposits in the view of isotope geochemistry

Resumo

Isotopic data, i.e. δ
13 C and δ
18 O including 86 Sr/87 Sr, are the fundamental data to characterize
geochemically magnesite mineralizations. Other geochemical data, e.g. chemical data, REE and
fluid chemistry, are supplementary characteristics for genetic models. The geological setting and
the origin of magnesium are relevant to classify magnesites genetically. The δ
13 C - δ
18 O - diagrams
of magnesite and siderite are significantly different. Stratabound magnesite is dominated by the
isotopic signature of carbonate sediments, while siderites from occurrences with economic
importance preferably show light carbon isotope like the ultramafic-hosted vein type mineralization.
The δ
18 O original values of sparry magnesites are strongly influenced by burial and grade of
metasomatism. Thus, the origin of sparry magnesite hosted by metasediments is to be considered
as a sedimentary enrichment influenced by diagenetic and metamorphic processes. An approach
to the best genetic model of each magnesite deposit needs the synopsis of all geological facts and
geochemical data.