Isotope geochemistry of the mafic dikes from the Vazante nonsulfide zinc deposit, Brazil |
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| Authors: | M Babinski LVS Monteiro AH Fetter JS Bettencourt TF Oliveira |
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| Institution: | 1. Department of Nursing, Fooyin University, Kaohsiung City 831, Taiwan;2. Graduate Institute of Applied Geology, National Central University, Taoyuan City 320, Taiwan;3. Department of Environmental Engineering and Science, Fooyin University, Kaohsiung City 831, Taiwan;1. Agricultural and Food Engineering Department, IIT Kharagpur, Kharagpur 721302, India;2. Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409, USA;3. Uttar Banga Krishi Viswavidyalaya, Cooch Behar 736165, India;4. Department of Experimental Statistics, Louisiana State University, Baton Rouge, LA 70803, USA;5. IRDM Faculty Centre, Ramakrishna Mission Vivekananda University, Kolkata 700103, India;6. National Institute of Research on Jute and Allied Fibre Technology, Kolkata, India |
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| Abstract: | The Vazante Group, located in the northwestern part of Minas Gerais, hosts the most important zinc mine in Brazil, the Vazante Mine, which represents a major known example of a hypogene nonsulfide zinc deposit. The main zinc ore is represented by willemite and differs substantially from other deposits of the Vazante-Paracatu region, which are sulfide-dominated zinc-lead ore. The age of the Vazante Group and the hosted mineralization is disputable. Metamorphosed mafic dikes (metabasites) that cut the metasedimentary sequence and are affected by hydrothermal processes recently were found and may shed light on the geochronology of this important geological unit. Zircon crystals recovered from the metabasites are xenocrystic grains that yield U–Pb conventional ages ranging from 2.1 to 2.4 Ga, so the basement of the Vazante Group is Paleoproterozoic or has metasedimentary rocks whose source area was Paleoproterozoic. Pb isotopes determined for titanite separated from the metabasites have common, nonradiogenic Pb compositions, which prevents determination of their crystallization age. However, the Pb signatures observed for the titanite crystals are in agreement with those determined for galena from the carbonate-hosted Zn–Pb deposits hosted by the Vazante Group, including galena from minor sulfide ore bodies of the Vazante deposit. These similarities suggest that the metalliferous fluids that affected the metabasites may have been those responsible for galena formation, which could imply a similar lead source for both nonsulfide and sulfide zinc deposits in the Vazante–Paracatu district. This common source could be related to deep-seated, basin-derived, metalliferous fluids associated with a long-lived hydrothermal system related to diagenesis and deformation of the Vazante Group during the Neoproterozoic. |
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| Keywords: | Isotope geochemistry Mafic dikes U– Pb geochronology Vazante Group Zn– Pb mineralization |
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