Abstract
The Araés gold deposit, located in eastern Mato Grosso State, central Brazil, is hosted in Neoproterozoic volcanosedimentary rocks of the Paraguay belt, which formed during collision of the Amazonian craton and the Rio Apa block. 40Ar/39Ar geochronology and Pb and S isotopic analyses constrain the timing and sources of mineralization. Three biotite flakes from two samples of metavolcanic host rock yield 40Ar/39Ar plateau ages between 541 and 531 Ma, interpreted as cooling ages following regional metamorphism. Clay minerals from a hydrothermal alteration zone yield an 40Ar/39Ar integrated age of 503 ± 3 Ma. Galena grains from ore-bearing veins yield values of 206Pb/204Pb from 17.952 to 18.383, 207Pb/204Pb from 15.156 to 15.811, and 208Pb/204Pb from 38.072 to 39.681. Pyrite grains from ore-bearing veins yield values of 206Pb/204Pb from 18.037 to 18.202, 207Pb/204Pb from 15.744 to 15.901, and 208Pb/204Pb from 38.338 to 38.800. Pb isotope variations may be explained in terms of mixing a less radiogenic lead component (μ ~ 8.4) from mafic and ultramafic basement host-rocks (Nova Xavantina metavolcanosedimentary rocks) and a more radiogenic lead component (μ ~ 9.2) probably derived from supracrustal rocks (Cuiabá sedimentary groups). Sulfur isotope compositions are homogeneous, with δ34S values ranging from -1.1‰ to 0.9‰ (galena) and -0.7‰ to 0.9‰ (pyrite), suggesting a mantle-derived reservoir for the mineralizing solutions. Based on the Ar, Pb, and S isotope data, we suggest that the precious metals were remobilized from metavolcanic host rocks by hydrothermal solutions during Brasilide-Panafrican regional metamorphism. The Araés gold deposit probably formed during a late stage of the orogeny, coeval with other mineralization events in the Paraguay Belt.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
