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Re-Os and Sm-Nd Isotope and Trace Element Constraints on the Origin of the Chromite Deposit of the Ipueira-Medrado Sill, Bahia, Brazil |
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| Authors: | MARQUES J C; FERREIRA FILHO C F; CARLSON R W; PIMENTEL M M |
| Institution: | 1 DEPARTAMENTO DE GEOLOGIA, INSTITUTO DE GEOCIÊNCIAS, UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL, AV. BENTO GONÇALVES 9500, PORTO ALEGRE-RS, 91509-900, BRAZIL 2 INSTITUTO DE GEOCIÊNCIAS, UNIVERSIDADE DE BRASÍLIA-UNB, CAMPUS UNIVERSITÁRIO, ASA NORTE, BRASÍLIA-DF, 70910-900, BRAZIL 3 DEPARTMENT OF TERRESTRIAL MAGNETISM, CARNEGIE INSTITUTION OF WASHINGTON, 5241 BROAD BRANCH ROAD, WASHINGTON, DC 20015, USA |
| Abstract: | The chromite deposit of the Paleoproterozoic Ipueira–Medradosill is hosted in a single, thick (5–8 m), massive layer,which sets severe constraints for the origin of chromitites.It is divided from bottom to top into: (1) a Marginal Zone (5–20m); (2) an Ultramafic Zone (<250 m) consisting of duniteand harzburgite that host the chromitite layer, in which intercumulusamphibole is important and more abundant toward the top; (3)a Mafic Zone (<40 m). The parental magma was large ion lithophileelement and light rare earth element enriched and high fieldstrength element depleted. Sm–Nd isotopic compositionsare consistent with a 2 Ga age, but suggest a variable initialNd isotopic composition that correlates with the abundance ofamphibole. The more negative |
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