Re–Os geochemistry and geochronology of the Ransko gabbro–peridotite massif, Bohemian Massif

0396218 - GLÚ 2014 RIV DE eng J - Journal Article
Ackerman, Lukáš - Pašava, J. - Erban, V.
Re–Os geochemistry and geochronology of the Ransko gabbro–peridotite massif, Bohemian Massif.
Mineralium deposita. Roč. 48, č. 7 (2013), s. 799-804. ISSN 0026-4598. E-ISSN 1432-1866
R&D Projects: GA ČR GA13-15390S
Institutional support: RVO:67985831
Keywords : Re–Os * geochronology * gabbro * Bohemian Massif * Ni–Cu mineralization
Subject RIV: DD - Geochemistry
Impact factor: 2.667, year: 2013

The Ransko gabbro–peridotite massif in Eastern Bohemia is a strongly differentiated intrusive complex, which hosts low-grade Ni–Cu ores mainly developed close to the contact of olivine-rich rocks with gabbros, in troctolites, and to a much lesser extent in both pyroxene and olivine gabbros and plagioclase-rich peridotites. Gabbro, troctolite, peridotite and Ni–Cu ores from the Jezírka Ni–Cu (PGE) deposit, considered to be a typical example of the liquid segregation style of mineralization, were analyzed for Re–Os concentrations and isotopic ratios. Seven barren and mineralized samples from the Jezírka deposit yielded a Re–Os regression of 341.5 ± 7.9 Ma (MSWD = 69). Strongly mineralized peridotite with mantle-like initial ¹⁸⁷Os/¹⁸⁸Os ratio of 0.125 suggests that Os as well as other PGE present in the Ni–Cu mineralization are predominantly of mantle origin. On the other hand, barren and low-mineralized samples have radiogenic initial ¹⁸⁷Os/¹⁸⁸Os ratios of 0.14–0.16 suggesting some import of Re and/or radiogenic ¹⁸⁷Os most likely through contamination by continental crust during magma emplacement. The Re–Os age of the Ransko Massif is significantly younger than the previously suggested Lower Cambrian age, but it is similar to and/or younger than the age of metamorphism of the adjacent Kutná Hora crystalline complex and the Moldanubian unit. Therefore, it is likely that the emplacement of the Ransko massif and its Ni–Cu mineralization was closely connected with the late-stage evolution of the Kutná Hora crystalline complex.
Permanent Link: http://hdl.handle.net/11104/0224050