The Florida Canyon deposit hosted by a carbonate-evaporite sequence of the Pucará Group, Peru, has both Zn-Pb sulphide and Zn non-sulphide mineralisations. The mineralogical characterisation of samples from the deposit enables the definition of a supergene assemblage dominated by smithsonite, in addition to hemimorphite, cerussite, and goethite. The main oxidation in the study area involved the direct replacement of primary MVT stratabound sulphide ore. In comparison with other non-sulphide deposits of the Bongará District, the Florida Canyon deposit can be correlated with the Cristal deposit by means of the original sulphides preserved in the supergene textures, the similar hosting dolostone layer, lack of hydrozincite, and depth of emplacement, which are characteristics that contrast with those of the Mina Grande deposit, also inserted in the Pucará Group. The Florida Canyon supergene mineral assemblage is a paleoclimatic indicator suggesting a humid tropical climate during the late Miocene in the Peruvian Amazon region.
The Mesquita Sampaio beforsite is a mineral exploration area with apatite mineralization occurring near the northern portion of the Morro da Mina apatite deposit (Cajati Mine), in the Jacupiranga Alkaline Complex. This study presents the mineralogical, geochemical and 3D geological modeling data of this target. Four lithotypes are presented for Mesquita Sampaio: the fine-grained beforsite (FGB), the coarse-grained beforsite (CGB), the xenolith zone (XEN), and the jacupirangite ( JAC). The 3D geological model shows the Mesquita Sampaio beforsite as a vertical body with an NNW direction and approximately 350 meters in length, 150 meters in width, and 400 meters of depth, with open extensions. The main mineral assemblage of the beforsite is dolomite, apatite, phlogopite, serpentine, calcite, and magnetite, in order of abundance. The distribution of major elements for both types of beforsites (FGB and CGB) indicates the same composition with only a small variation in the mineral proportions. Although no direct contact relation between Mesquita Sampaio and Morro da Mina is known, both may be the same carbonatite body with a gradual compositional variation, or the Mesquita Sampaio beforsite could be a distinct late or even earlier carbonatite pipe.
AGRADECIMENTOSAo Prof. Dr. Marcelo Rocha pela orientação na elaboração deste trabalho, pelas inúmeras e valiosas discussões geoestatísticas e a constante disposição e atenção em ajudar em todas as etapas deste pesquisa.Ao Prof. Dr. Jorge Kazuo, a quem eu admiro o profissionalismo e agradeço pela colaboração e orientação na etapas iniciais deste trabalho.À empresa Votorantim Metais, representada pelo Dir. Jones Belther e Ger. Thomas Brenner, não só por permitir o desenvolvimento deste trabalho concomitantemente às minhas atividades profissionais, mas também pelo incentivo à sua realização.Aos amigos e também colegas de profissão Geól. Paulo Ravacci, Geól. Jonas Mota e Geól. Gustavo Diniz pelo apoio, discussões geológicas e oportunidades de aprendizado proporcionadas.
Aos colegas
The Florida Canyon evaporite-related Zn-Pb sulfide deposit, in northern Peru, is one of the largest Mississippi Valley-type deposits in South America. Triassic carbonate and former evaporite-bearing rocks of the Pucará Group host the orebodies that constitute two different styles: (1) predominantly stratabound ore associated with hydrocarbon-rich porous dolostones and evaporite dissolution breccias and (2) high-grade ore associated with evaporite breccias representing diapiric injections along faults. A dome structure that controls the location of the ore deposit was defined by drill hole spatial data; the dome likely resulted from halokinetic processes during Andean deformation. NNE-trending, steeply dipping secondary faults linked to major northwest structures appear to control the distribution of ore grades in the deposit. Mineralization postdated hydrocarbon migration and accumulation. Strontium, carbon, and oxygen data isotope signatures allow distinction between pre- and synmineralization carbonate stages. The sulfur isotope composition of sulfides in the deposit suggests they precipitated as the result of mixing of a metal-rich fluid with resident hydrogen sulfide in the dome. Local thermochemical sulfate reduction may have contributed to the reduced sulfur budget during mineralization.
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