Abstract:
In eastern Elba, a N-S trending belt of iron ore deposits, mainly containing hematite, magnetite and minor pyrite, were formed near the contact to shallowly underlying late Miocene granites. A detailed study of their parageneses, ore mineralogy, and their structural relationship allows to reconstruct the depositional evolution. The Miocene pyrometasomatic - hydrothermal mineralization, associated with skarn formation, precipitated parageneses at temperatures which did not surpass 500°C at most. Up to two pyrite, three magnetite, and three hematite generations crystallized or replaced each other. Silican magnetite and magnetite enclosing remnants of cassiterite appear besides of chalcopyrite, galena and pyrrhotite in joints. Magnetite-dominated deposits in the south and hematite-rich deposits in the north of the ore belt can be distinguished.
A genetic scheme is proposed including pre-Miocene iron enrichment, late Miocene contact metasomatism, Fe-(re)mobilization and ore formation by hydrothermal circulation. Cassiterite, ilvaite and other skarn minerals as well as the absence of typical magmatic parageneses indicate a fluid-dominated remobilisation process of an Fe-rich source rock, depending on the distance to the intrusion. No simple evolutionary trend along stability field interfaces occurs.
The iron ore deposits of eastern Elba were formed in connection with late Miocene (Messinian) shallow magmatic heat source in the cause of granitoid emplacement. Due to metasomatic and hydrothermal processes iron-rich skarns emerged. The primary preconcentration of iron is synsedimentary (late Paleozoic-Triassic). The deposits are lined up in NS direction and show a temperature zoning.
The Elban ore deposits were subject to different explanation models:
Epigenetic (pyrometasomatic) formation directly related to the Tertiary intrusive bodies, or a Volcano-sedimentary formation of Permo-Triassic age and subsequent Alpine metamorphic overprinting.