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The PALMEIROPOLIS Cu-Zn (Pb) volcanogenic massive sulfide deposit, Brazil, consists of three ore bodies enclosed by hydrothermal alteration zones. The ore bodies and the alteration zones were metamorphosed under amphibolite fades conditions. The Palmeirdpolis alteration zones are characterized by a great diversity of bulk rock composition that originated a wide variety of low variance mineral assemblages. These assemblages are composed of orthoamphiboles (anthophyllite and gedrite), hornblende, biotite, garnet, staurolite, sillimanite, gahnite and, rarer, cordierite. Based on analyses of mineral chemistry aad mineral assemblages, temperatures are estimated to have been 550 - 625°C and pressures 2 - 5.5 kbar. The temperature of metamorphism that prevailed at the Palmeirdpolis deposit is comparable to other amphibolite fades massive sulfide deposits, such as Geco and Linda, Canada; Falun, Sweden; and Bleikvassli, Norway. The mineralogy of the alteration zones is similar in all these deposits even though they were metamorphosed at different pressure conditions, reflected by the crystallization of one of Al2SiO5 phase (andalusite, sillimanite or kyanite). RESUMO METAMORFISMO DE ROCHAS HIDROTERMALMENTE ALTERADAS ASSOCIADAS A DEPOSITO DE SULFETO MACICO VULCANOGENICO: O EXEMPLO DE PALMEIROPOLIS, BRASIL O deposito de sulfeto MACICO a Zn e Cu vulcanogenico de Palmeirdpolis, Brasil, consiste de tres corpos de minerio associados a zonas de alteracao hidrotermal. Os corpos de minerio e as zonas de alteracao foram metamorfisados no fades anfibolito. As zonas de alteracao do deposito sao caracterizadas por uma grande diversidade quimica que originou uma grande variedade de assembleias mineralogicas. Essas assembleias sao compostas por ortoanfibolios (antofilita e gedrita), homblenda, biotita, granada, estaurolita, silimanita, gahnita e, mais raramente, cordierita. Baseado na composicao quimica de diferentes minerals e na associacdes mineralogicas, a temperatura de metamorfismo foi estimada entre 550 e 625°C e a pressao entre 2 e 5,5 kbar. A temperatura de metamorfismo a qual o deposito de Palmeiropolis foi submetido e comparavel a de outros depositos de sulfeto macico tambem metamorfisados no fades anfibolito, tais como Geco e Linda, no Canada; Falun, na Suecia; e Bleikvassli, na Noruega. A mineralogia das zonas de alteracao e similar em todos esses depositos apesar de terem sido submetidos a diferentes condicoes de pressao, refletidas apenas pela cristalizacao de um ou outro polimorfo de A12SiO5 (andalusita, silimanita ou cianita). Palavras-chaves: deposito vulcanogenico, zonas de alteracao hidrotermal, facies anfibolito. INTRODUCTION The metamorphosed Zn-Cu (Pb) PALMEIROPOLIS massive sulfide deposit is located 200 km north of Brasilia, central Brazil. It contains 4 million metric ton in three ore bodies, C-l, C-2 and C-3, having an average com- position of 1.23 percent Cu, 4.64 percent Zn, 0.72 percent Pb and 25.1 g/t Ag (Figueiredo et al. 1981). All ore bodies are associated with alteration zones composed of assemblages with anthophyllite, biotite, cordierite, gahnite, sillimanite and staurolite. In this study, we present data on petrography and mineral chemistry of amphiboles, biotite, garnet, cordierite, staurolite and gahnite from the alteration zones from which we derive the metamorphic conditions that prevailed at the Palmeirdpo- lis deposit. A comparison is made with alteration zones of other metamorphosed volcanogenic massive sulfide deposits. GEOLOGICAL SETTING The Palmeiropolis deposit is situated in the Palmeirdpolis volcano-sedimentary sequence (PVSS), part of a 300 km-long major volcano-sedimentary belt that includes the southern Indaianopolis and Juscelandia volcano-sedimentary sequences. This belt is located at the western border of the large granulitic mafic-ultramafic com- plexes of central Brazil (Cana Brava, Niquelandia and Barro Alto). Together, these form a linear array within Proterozoic fold belts located between the Amazon and Sao Francisco Cratons. The main geotectonic units present in the region are

METAMORPHISM OF HYDROTHERMALLY ALTERED ROCKS IN A VOLCANOGENIC MASSIVE SULFIDE DEPOSIT: THE PALMEIRÓPOLIS, BRAZIL, EXAMPLE