Coupled Pb-Os isotope systematics were studied within ore facies, host rocks and sediments from the Paleozoic VHMS deposits in Southern Urals, Russia.
Lead isotope composition becomes progressively more radiogenic from early fore-arc environments to intra-arc and back-arc settings, which can be explained in terms of metasomatism of the depleted mantle wedge in the Ordovician - Early Devonian due to subduction of sediments and continental fragments. A metasomatized mantle wedge signature is expressed in LREE enrichment and low epsilon(Nd) values.
Os and other PGEs are enriched in first-stage high-temperature portions of hydrothermal systems, whereas Re has more affinity with lower temperature polymetallic assemblages. In each deposit, the Re/Os ratio and initial (187)OS/(188)Os isotopic compositions in ores decrease from the bottom to the top of hydrothermal system, reflecting variable degrees of mixing between hydrothermal fluid and Devonian seawater.
The Re-Os model ages for four studied deposits from different tectonic settings are similar (about 366 +/- 5 Ma) and younger than the presumed stratigraphic ages. This age could indicate a late Os isotope reequilibration associated with long living hydrothermal processes attending formation and closure of the Urals paleo-ocean in a Late Devonian time.
|Title of host publication||Smart science for exploration and mining|
|Place of Publication||Townsville, QLD|
|Publisher||JAMES COOK UNIV|
|Number of pages||3|
|Publication status||Published - 2010|
|Event||10th Biennial SGA Meeting of the Society for Geology Applied to Mineral Deposits - Townsville, Australia|
Duration: 17 Aug 2009 → 20 Aug 2009
|Conference||10th Biennial SGA Meeting of the Society for Geology Applied to Mineral Deposits|
|Period||17/08/09 → 20/08/09|
- Massive sulphide deposits
- isotope systematics
- MASSIVE SULFIDE DEPOSITS
- SOUTH URALS