Annabel Pérez-Aguilar

Fluoreto nas águas subterrâneas dos aqüíferos Tubarão e Cristalino, região de Salto-Indaiatuba (SP)

Anomalous concentrations of fluoride in groundwater were identified in 19 drilling wells in the Salto-Indaiatuba region, Sao Paulo State, with an average concentration of 3.03 mg dm-3 and a maximum of 6.95 mg dm-3, which constitute a restriction for the waters usage in terms of human consumption. The wells exploit water from the Tubarao Aquifer (sedimentary, granular) and Crystalline Aquifer (granitic, fractured), used for sanitary or industrial purposes. These groundwaters are typically HCO3 and HCO3-SO4 types, with high concentrations of HCO3-and Na+ and high pH-values between 7.5 and 10.0. The highest concentrations of F- are associated to the Tubarao and Tubarao/Crystalline aquifer drilling wells. The presence of F- in groundwater is controlled by these high pH-values, alkalinity, and fluorine availability. The source of fluoride in the Tubarao and Crystalline Aquifers can be related to the percolation of hydrothermal fluids associated with Mesozoic lava flow, emplaced due to the opening of Atlantic Ocean and/or hydrolysis of fluorine-rich minerals and clay minerals.

The inventory of geological heritage of the state of São Paulo, Brazil: Methodological basis, results and perspectives

An inventory of geological sites based on solid and clear criteria is a first step for any geoconservation strategy. This paper describes the method used in the geoheritage inventory of the State of São Paulo, Brazil, and presents its main results. This inventory developed by the geoscientific community aimed to identify geosites with scientific value in the whole state, using a systematic approach. All 142 geosites representative of 11 geological frameworks were characterised and quantitatively evaluated according to their scientific value and risk of degradation, in order to establish priorities for their future management. An online database of the inventory is under construction, which will be available to be easily consulted and updated by the geoscientific community. All data were made available to the State Geological Institute as the backbone for the implementation of a future state geoconservation strategy.

Superfícies estriadas no embasamento granítico e vestígio de pavimento de clastos neopaleozóicos na região de Salto, SP

Near Guarau Ceramic, localized southwest of Salto city in the State of Sao Paulo, two granite outcrops, distant some tens of meters from each other, display Neopaleozoic striated surfaces. These surfaces are in contact with diamictites from the Itarare Subgroup. The striae correspond to sub parallel grooves with millimetric spacing and depth, oriented about N48E and dipping 12° to 42° towards SE. Observed features and association with diamictites indicate an origin by glacial abrasion due to ice movement from southeast towards northwest. About 1.8 km east of Salto, unconsolidated material containing flat-iron-shaped and striated clasts was found on top of granite outcrops, interpreted as clast pavement remains.

Petrografia de zonas de alteração hidrotermal mesoproterozóicas do tipo Kuroko no Grupo Serra do Itaberaba (SP) e seu uso na exploração mineral

In the volcano-sedimentary Serra do Itaberaba Group, located within the central part of the Ribeira Fold Belt, Mesoproterozic paleo-hydrothermal systems developed surrounding small bodies of andesites and rhyodacites. These systems were responsible for the hydrothermal alteration of basic and intermediate igneous and volcaniclastic rocks. Despite the overprinting of two medium-grade and one low-grade metamorphic-deformational events, well-defined zones generated by different types and intensities of hydrothermal alteration are still recognizable. An initial large chloritic alteration zone (ZC1) was overprinted by restricted chloritic (ZC2) alteration zones, similar to those associated with Kuroko-type base metal deposits. The metamorphic products from ZC1 have magnesium amphibole(s) in different proportions (cummingtonite-anthophyllite rocks) and those from ZC2, Mg-chlorite (meta-chloritites). These rocks are composed of exotic mineralogic associations and can be used as exploration guides for Kuroko-type base metal deposits present in metamorphosed volcano-sedimentary sequences.

Anomalias de flúor nas águas subterrâneas do estado de São Paulo

This work examines the data compiled from the literature about the main occurrences of fluoride (F - ) in the groundwater of the State of Sao Paulo. The results of this study showed that at least 208 wells had high concentrations of F - (> 1.0 mg dm -3 ), 122 of which were considered anomalous (> 1.5 mg dm -3 ) and harmful when ingested in large quantities. Because of its high productivity and large-scale exploitation, the Guarani aquifer is the most studied one, but other aquifers, such as the Crystalline (Precambrian), Serra Geral and Tubarao aquifers, and the Passa Dois aquitard should also be considered important. In the past, the increase in the concentration of F - in the aquifers was related to hydrothermal processes and tectonic events with structural controls, such as the Gondwana supercontinent breakup, which would have enable the circulation of residual magma solutions, mineralization, and remobilization of the fluorine contained in the percolated rocks. Currently, the release of F - is caused due to the rock-water interaction under alkaline pH hydrochemical conditions, in typical sodium-bicarbonated (Na-HCO3) waters, poor in Ca 2+ , and under the influence of ionic strength, contact time, depth, temperature, ion exchange capacity, among others. In fissured aquifers of granitic composition and volcanic rocks, the minerals that can release F - into water are biotite and amphibole (where F - is replacing OH - , due to the similarity of its ionic radii) and, occasionally, secondary fluorite filling fractures and apatite. In sedimentary aquifers, F - is mainly found in clay minerals structures (illite, muscovite, smectite, vermiculite, kaolinite, among others) replacing OH - . Therefore, the high levels of F - in the groundwater are intrinsically associated with the characteristics and types of minerals of the aquifers.

Produtos metamórficos de sistemas high-sulfidation oceânicos mesoproterozoicos, grupo Serra do Itaberaba, SP

In the central portion of the Ribeira fold belt, southeastern Brazil, the Mesoproterozoic volcanosedimentary Serra do Itaberaba Group was affected by two medium-grade regional metamorphic events and by a third low-grade retrometamorphic event. This succession was deposited in an ocean basin having N-MORB type basalts that evolved to a back-arc environment. Within the group four occurrences of alumina-rich rocks are now known (Guavirituba, Pedra Branca, Itaberaba and Pico Pelado), which crop out as small lenses intercalated between metabasites and metamorphosed volcanoclastic rocks, tuffs and pelites. Their genesis is related to oceanic magmatic-hydrothermal activity in the backarc environment that was associated with the emplacement of small rhyolitic bodies and high-sulfidation gold mineralization. X-ray diffraction analysis (XRD) of 15 very fine-grained alumina-rich samples permitted corundum, topaz, margarita, rutile and an undifferentiated mica (possibly sericite) to be identified. Mineral associations allow recognition of two advanced argillic alteration events and a third carbonation or retrometamorphic event that affected rocks of the Serra do Itaberaba Group: the first event generated protolith 1 rich in aluminum oxides ± alunite that after metamorphism produced dark blue lithotypes composed of corundum ± sericite; the second event was a silicification event that produced protolith 2 composed of topaz + zunyite + alunite ± rutile or of andalusite + alunite, with metamorphic products corresponding to brown and whitish lithotypes (Pico Pelado occurrence); during carbonatization or retrometamorphism, margarite crystalized after andalusite, cyanite or sillimanite. The sum of these three events produced, after the metamorphism or retrometamorphism, brown, whitish, and heterogeneous lithotypes composed of margarite or of margarite + sericite ± corundum (Guavirituba and Pedra Branca occurrences). The identification of similar lithotypes during field work represents a potentially very valuable tool in mineral exploration works as they comprise rock guides for finding gold deposits in medium-grade metamorphosed volcanosedimentary sequences.

Reconstituição do sistema de transporte de água associado à lavra de ouro durante o período colonial nos arredores de Guarulhos, SP, Brasil

According to several authors, during the Brazilian colonial period, the exploitation of gold was first carried out in the regions of Guarulhos, Jaragua, Pirapora do Bom Jesus, Sorocaba and Paranagua. The period from 1553 to 1597 can be considered the starting point of the first gold mining cycle, which lasted approximately 200 years. In Guarulhos, gold was mainly mined from alluvial, colluvial, eluvial, saprolitic deposits, and from quartz veins associated with rocks of the Serra do Itaberaba Group, which corresponds to a Mesoproterozoic metamorphosed volcano-sedimentary sequence. Ten ducts and a tunnel, located near the city of Guarulhos, constitute archaeological gold mining structures from that time. They are spatially and temporally associated with dams, mining benches, mining fronts, channels, drains, places to wash and seek gold, gravel waste piles and remnants of stone walls. Mining caused anthropogenic changes in the landscape on several scales, due to activities related to excavation of hillsides, abandonment of mining operations and enlargement of valleys. The relation of the ten ducts and the tunnel to several other archaeological gold mining structures allowed us to characterize them as part of the water transportation system associated with the gold mining activity carried out in this period in the outskirts of Guarulhos. They are closely associated with the hydrographic basins of Guavirituba, Tome Goncalves, Tanque Grande, and Guaracau streams. The ducts, located in the headwaters of river basins, upstream of small drainages, were built with the objective that the water stored in dams, which was essential to downstream exploitation of gold, flew by gravity. The function of the tunnel was to supply water for the exploitation of a mainly colluvial deposit on the hillside. The results obtained in this study are part of a larger effort to retrieve, recover, preserve and disclose records of great archaeological, mining, geological, historical and cultural value within the context of the Gold Cycle Geopark of Guarulhos. These records should be useful in the difficult task of recovering the early colonial history and first Gold Cycle in Brazil, which are usually ignored by historians.

Geology of metamorphic rocks deriving from paleohydrothermal systems in the Mesoproterozoic Serra do Itaberaba Group, São Paulo State, southeastern Brazil

ABSTRACT In the central portion of the Ribeira fold belt, southeastern Brazil, the Mesoproterozoic volcanosedimentary Serra do Itaberaba Group was deposited in an ocean basin having normal mid-ocean ridge basalt type basalts that evolved to a back-arc environment. This succession was affected by two medium-grade regional metamorphic events and a third low-grade retrometamorphic event. This geological map covers an area of approximately 16 km2, between 23°16′41.824″ and 23°18′47.744″ latitudes S, and 46°20′57.056″ and 46°23′18.933″ longitudes W, as a scale of 1:5000. It encompasses the metamorphic products of tectonically deformed paleohydrothermal systems that developed in a back-arc environment, which are spatially and genetically linked to small metamorphosed andesitic-rhyolitic bodies. These systems were responsible for lixiviation of Ca and alkali in deeper parts, carbonatization in shallower parts, and a first large chloritic alteration zone (CZ1) that was crosscut by small chloritic (CZ2), silicification, and advanced argillic alteration zones. The metamorphic products of CZ1 are cummingtonite/anthophyllite rocks, whereas those related to CZ2 are Mg-rich chloritites. The metamorphic products of silicification and advanced argillic alteration zones are rocks composed of quartz ± specularite and of corundum, margarite, sericite, tourmaline, rutile, and Ca-plagioclase, respectively. Those associated with Ca and alkali depletions are garnet-hornblende amphibolites, whereas those related to carbonatization zones are composed of diopside, hornblende, tremolite/actinolite, carbonate, clinozoisite/epidote, plagioclase, and quartz. Cummingtonite/anthopyllite rocks and Mg-rich chloritites are similar to those associated with metamorphosed Kuroko-type volcanogenic massive sulfide deposits, whereas rocks composed of corundum, margarite, sericite, tourmaline, rutile, and Ca-plagioclase are genetically associated with oceanic high-sulfidation magmatic-hydrothermal gold mineralization.