NOME: MANOEL GABRIEL SIQUEIRA GUERREIRO
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO ALUVIONAR APLICADA À REGIÃO DE DOM BOSCO E
MORRO DO BULE - MINAS GERAIS"
RÉSUMÉ:Cette recherche a eu pour objet de
déterminer l'efficience de la prospection alluvionnaire systématique dans la
recherche des indices minéralisés. Dans ce but a été choisie une région dont la
géologie était connue et où l'on savait exister de petites minéralisations.
NOME: LUIZ CARLOS SURCAN DOS SANTOS
ORIENTADOR: ELYSIÁRIO TÁVORA
FILHO
TÍTULO: "EVOLUÇÃO GEOQUÍMICA E MINERALOGIA NA FORMAÇÃO DE UM SOLO
NIQUELÍFERO"
ABSTRACT: Seletive samples and a latosolic profile on
serpentinite at Liberdade (Minas Gerais) has been investigated in order to
elucidate the genesis of the secondary minerals and the main element behaviour
during tropical weathering. Nickel bearing minerals and related species were
identified by mineralogical, optical, chemical, X-ray diffraction and
differential thermal analyses. The parent rock is composed basically of
serpentine (90 to 95%). Minor amounts of magnetite, chlorite, spinel, talc,
pyroxene, amphibole and goethite are also present. The mineral assemblage of the
soil consists of goethite, quartz and chalcedony, chlorite, serpentine minerals,
vermiculite, kaolinite, gibbsite and magnetite. Minor amounts of talc,
montmorillonite, amphibole (cummingtonite and tremolite), spinel, cromite and
rutile are also present. Serpentine gradually alters, with the formation of
intermediate phases, into goethite, kaolinite, gibbsite and free silica
(chalcedony and quartz). The presence of Mg2+ in a basic environment promotes
the formation of montmorillonite and chlorite in an amount proportional to the
content of Al2O3 in the original solutions. Both minerals are unstable.
Magnetite, rutile and chromite which are stable, remains in the profile and are
concentrated mechanically. MgO which is removed more easily than silica was
lost. Silica is partially removed and partially precipitated as coloidal silica
with later recrystallization. Alumina is concentrated in the upper part of the
profile. Some is held in the goethite structure and the rest is constituted by
kaolinite and gibbsite. Iron shows a large accumulation in the B horizon as
goethite at different degrees of crystallization. Titanium in the soil is either
associated with goethite or present as free TiO2 in rutile and anatase or again,
in minor quantity, in the magnetite structure. Nickel is concentrated in the C2
horizon, just above fresh serpentinite, by two convergent processes: alteration
of the parent rock and leaching of unstable minerals "per descensum" in the B
horizon. This leaching is aided by the presence of iron hidroxides giving rise
to slight acidity of the soil (pH 6,0) inthe B horizon. However, ideal
conditions for nickel precipitation are found in the C2 horizon which has a
higher pH (6,8). Nickel is always associated with sheet silicates like
serpentine, chlorite, montmorillonite and vermiculite. Nickel is in diadocic
substitution of magnesium, mainly in clay fraction. There are no significant
amounts of nickel associated with goethite of magnetite. The presence of
kaolinite and gibbsite in the B horizon indicates a mature soil.
NOME: ANA MARIA NETTO FERREIRA
ORIENTADOR: LUÍS ALFREDO MOUTINHO DA
COSTA
TÍTULO: "PETROGRAFIA DA QUADRÍCULA DE CONCEIÇÃO DO RIO VERDE - MINAS
GERAIS"
ABSTRACT:
NOME: ALEXANDRE VALE DE FREITAS FERREIRA
ORIENTADOR: LUÍS ALFREDO MOUTINHO
DA COSTA
TÍTULO: "GEOLOGIA DA QUADRÍCULA DE CONCEIÇÃO DO RIO VERDE - MINAS
GERAIS"
ABSTRACT:
NOME: JOSÉ MOREIRA DE SOUZA
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO COM BATEIA DO DISTRITO DE DOM BOSCO - MINAS
GERAIS"
ABSTRACT: This study describes the investigation of the disitribution
of heavy index mineral in an area of approximately 60 square kilometers in the
regions of Dom Bosco and Morro Gabriel of central Minas Gerais through the
technique of mineral tracing by hand panning and sample concentrate
identification. Field and laboratory procedures of sampling and preparing
eighty-six panned concentrates for identification with the binocular microscope
are reviewed. The physical characteristics of twenty-two indicator minerals
including romeite and wulfenite, which had never been found previously in the
area investigated, are described and isograde maps showing their distribution
are presented. Cinnabar and topaz which are more interesting are discussed from
the viewpoint of genesis and possible economic importance. From the data
obtained the author concludes thta sampling by hand panning is the most
satisfactory procedure in exploring for economic minerals over widespread areas.
NOME: CARLINDA CAMPELO FARIAS
ORIENTADOR: JEANNINE ODETTE
CASSEDANNE
TÍTULO: "FOSFATOS MINERAIS DO PEGMATITO DA MINA SAPUCAIA,
GALILÉIA, MINAS GERAIS"
ABSTRACT: The Sapucaia pegmatite is granitic in
composition and yieds a significant production of muscovite and beryl. The
phosphate minerals occur either in intimately intergrowth with many other
phosphates or with accessory minerals such a spodumene, beryl, turmaline and
sulfides. The chemical analysis, the approximate indices of refraction, the
specific gravity, differential thermal analysis and X-ray powder data are
listed. Eighteen phosphate minerals from the Sapucaia pegmatite are described
and three additionals (unidentified) that may be alterarion products of minerals
descibed or know only from this locality.
NOME: GLÍCIA SANTOS BORBA
ORIENTADOR: ELYSIÁRIO TÁVORA FILHO
TÍTULO:
"ROCHAS VULCÂNICAS DA FAIXA COSTEIRA SUL DE PERNAMBUCO - ASPECTOS PETROGRÁFICOS
E GEOQUÍMCOS"
ABSTRACT:
NOME: ESPEDITA GONÇALVES DE TORRE
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO ALUVIONAR NO COMPLEXO ULTRAMÁFICO-ALCALINO DE
SERRA EGRA, PATROCÍNIO - MINAS GERAIS"
ABSTRACT: The research aimed at the
evaluation of the alluvial prospecting method in a region of carbonatic
intrusions. The alkaline-ultramafic Complex of Serra Negra of
Tertiary/Cretaceous Age is intrusive in rocks of the Bambui Group. These rocks
are in overthrusting contact with the rocks of the Canastra Group. Both
sequences belong to the Upper Precambrian. The work was divided in field and lab
stages. The field work consisted of a systematic sampling comprising almost all
the N rim of the dome where 138 panned concentrates were collected. The lab work
consisted of the splitting of the concentrates and identification of their
various constituents. As from the obtained data, surfaces of equal abundance
were delimited and comments about the provenience, distribution and association
of the minerals were done. The influence of the geomorphology on the behaviour
and partition of some of these minerals was also evaluated. The results were
quite interesting. It was possible to detect almost all the occurrences
previously known, permitting also the discovery of other occurrences still not
determined, like crandallite, gold, chalcopyrite, malachite, xenotime, monozite,
corundum, siderite, andaluzite and kyanite.
NOME: MARIA SUZANA PESSOA DE SOUZA
ORIENTADOR: JEANNINE ODETTE
CASSEDANNE
TÍTULO: "ESTUDO COMPARATIVO DE VÁRIOS MÉTODOS
RADIOCRISTALOGRÁFICOS APLICADOS A FOSFATOS DE FERRO E MANGANÊS"
BANCA
EXAMINADORA: IGNACIO AURELIANO MACHADO BRITO, JACQUES PIERRE CASSEDANNE, AUGUSTO
BAPTISTA
DATA DA DEFESA: 14 DE SETEMBRO
NO DO PROCESSO:
25.370/78
ABSTRACT: This research was made aiming at the evaluation of
comparatively several radiocrystallography methods under use and precision of
data obtained. The X-Ray diffraction methods (Debye-Scherrer, Precession,
Rotation, Weissenberg), the fluorescence analysis, the differential thermal
analysis and the thermal gravimetric analysis, were applied to two phosphates of
iron and manganese, Eosphorite and Hureaulite, found in pegmatites of the Rio
Doce valley and of the Rio Jequitinhonha valley, State of Minas Gerais, Brazil.
A very through study was made embracing from the unit cell dimensions up to the
group of these phosphates, enabling the addition of new radiocrystallography
data to the ones existing in the specialized literature.
NOME: ROGER DIAZ TORO
ORIENTADOR: JACQUES PIERRE CASSEDANNE
TÍTULO:
"MINERALOGIA DOS ALUVIÕES DIAMANTÍFEROS DUMA ÁREA DA QUEBRADA GRANDE AFLUENTE DO
RIO GUANIAMO - ESTADO BOLIVAR - VENEZUELA"
ABSTRACT: This work contains the
results of alluvial prospection on stratigraphic horizons in the Quebrada Grande
creck, which joints the Guaniamo river, and is located in the Cedeño District,
State of Bolivar, Venezuela. Alluvial prospection works were made along a
13kilometer belt, 40 to 300 meters wide, located approximately 450km SSE of
Caracas, the country capital. The study aim is to get the necessary information
which will let us stablish the possible origin of the Guaniamo diamonds. All
mineral besides quarz, identifide in alluvial materials as essential, were
microcline, epidote, ilmeno-rutile, garnet, diamond, forsterite and also opaque
mineral. Absence of both magnesium ilmenite and chromifem diopside let infere
that Guaniamo area diamonds have secondary origin and come from Roraima
Formation conglomerate. This is also emphasized by low rounding of gravel size
material. Due to lack of proper planning of the mining operations themselves,
the samples were collected at randon, but equidistances within a same mine were
always kept. Geologically the outcrups occur in a series of diabase, anphibolite
and gneissic-granite dikes and following the outcome of age determinations by
the K/Ar and Rb/Sr (Mendonza, 1972) methods the rocks have been classified
Pre-Cambriam (1800-1500 Myrs) overlain discordantly by the Roraima and Cinaruco
formations.
NOME: HAMILCAR D'ÁVILA FREIRE DE CARVALHO
ORIENTADOR: JEANNINE ODETTE
CASSEDANNE
TÍTULO: "CONTRIBUIÇÃO A ANÁLISE QUÍMICA QUANTITATIVA APLICADA A
FOSFATOS NATURAIS DE PEGMATITOS"
BANCA EXAMINADORA: FRANKLIN DOS SANTOS
ANTUNES, J. HANS DANIEL SCHORSCHER, JACQUES PIERRE CASSEDANNE
DATA DA DEFESA:
17 DE JULHO
NO DO PROCESSO: 16.399/79
NOME: NAJLA MAROUN ESTRADA
ORIENTADOR: JEANNINE ODETTE
CASSEDANNE
TÍTULO: "ESTUDO COMPARATIVO DE MÉTODOS PARA DOSAGEM DE FÓSFORO EM
FOSFATOS NATURAIS"
BANCA EXAMINADORA: JACQUES PIERRE CASSEDANNE, HÉLIO
MONTEIRO PENHA, FRANKLIN DOS SANTOS ANTUNES
DATA DA DEFESA: 17 DE JULHO
NO
DO PROCESSO: 16.400/79
NOME: CACILDA NASCIMENTO DE CARVALHO
ORIENTADOR: J. HANS DANIEL
SCHORSCHER
TÍTULO: "HIDROQUÍMICA DO RIO SARAPUÍ - RJ"
BANCA EXAMINADORA:
FRANKLIN DOS SANTOS ANTUNES. JEANNINE ODETTE CASSEDANNE, MÁRIO DA SILVA
PINTO
DATA DA DEFESA: 12 DE DEZEMBRO
NO DO PROCESSO:
33.292/80
ABSTRACT: Analysis of the complete course of the Rio Sarapuí-RJ, a
NW affluent of Copacabana Bay were made anda data are here presented. The
analysis were made "in situ", by colorimetry and titration. They indicate
Defficiency of Dissolved Oxigen and characterize Chloride, Sulfide, Ammonia,
Nitrite, Cyanide, Total Hardness, pH, Total Iron, Chromium VI and Copper, giving
nine hundred and eighty data. The atomic absorption spectroscopy analysis of the
soluble fraction (0,45m) characterize Magnesium, Calcium, Chromium, Manganese,
Iron, Copper, Zinc, Cobalt, Nickel, Cadmium, Mercury and Lead. Sodium and
Potassium were analysed by flame photometry. The instrumental analysis totalize
one hundred and forty data. The results obtained permit to classify the river
into domiciliar, intermediary and industrial zones, according to the emissions
that it receives. All the zones are contaminated by chemical species in
different concentrations.
NOME: LINDALVA MARIA JOSÉ DOS REIS CÂMARA
ORIENTADOR: JEANNINE ODETTE
CASSEDANNE
TÍTULO: "UTILIZAÇÃO DE INDICADORES QUÍMICOS NA ESTRATIGRAFIA DE
DEPÓSITOS CONTINENTAIS CENOZÓICOS"
BANCA EXAMINADORA: ELMO DA SILVA AMADOR,
FRANKLIN DOS SANTOS ANTUNES, MANLIO SILVESTRE FERNANDES
DATA DA DEFESA: 16 DE
DEZEMBRO
NO DO PROCESSO: 34.515/80
ABSTRACT: Research comprises the
development of quantitative chemical analises of some meaningful elements such
as: Sodium, Potassium, Calcium , Iron, Aluminum and Silica. The applied methods
were satisfactory and proposed , throughout their results, a new metodological
option toward characterizing and individualization of lithostratigraphics units
and its application as a paleoenvironmental indicator. It's a research that
comprises analises of sediments of the terciary and pleistoceno from Taubaté ,
Espírito Santo and Volta Redonda Basins.
NOME: JEANETE ALVES RIBEIRO
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO COM BATEIA NO MACIÇO ALCALINO DE TANGUÁ E
ADJACÊNCIAS, MUNICÍPIOS DE ITABORAÍ E RIO BONITO - RJ"
BANCA EXAMINADORA:
FERNANDO ROBERTO MENDES PIRES, JOEL GOMES VALENÇA, AUGUSTO BAPTISTA , HÉLIO
MONTEIRO PENHA (suplente)
DATA DA DEFESA: 08 DE OUTUBRO
NO DO PROCESSO:
29.537/81
ABSTRACT: The aim of this work was to check panning prospecting
method in a Precambrian basement complex area intrued by a sienitic massif
partially surrounded by associated intrusives magmatic breccia (Tanguá Massif).
In a first field phase, eluvional and/or aluvional samaples were systematically
collected according to a 1Km2 grid . These sample were than submitted to a
routine laboratory work (heavy liquid and isodynamic sepration, etc). Heavy
minerals were determined by optical examination under a binocular microscope and
a polarizing microscope, and chemical methods. When necessary X-Ray diffration
was used. The results obtained from the work above were plotted in 23 mineral
distribution maps and they allowed to examine the source and mineralogical
association of each of the these minerals and to establish preliminary
hypotheses. In a second field phases, a sampling control was carried out in
order to check the previous conclusions. This study permitted us to find the
following mineralogical associations: 1 - Magnetite - Titanite - Leucoxene:
Related to syenitic rocks; 2 - Zircon - Monasite - Ilmenite: Related to gneisses
and migmatites; 3 - Sillimanite - Almandine Garnet: Related to gneissic rocks
derived from pelitic sediments; 4 - Epidote - Grossularite - Andradite: Related
to calc - silicate rocks; 5 - Kyanite - Andalusite: Related to gneissic rocks.
The presence of kyanite would be taken as the indicator of the transition from
the metamorphism between the low to the medium pressure types. Finally, the
provenance of numerous others minerals some of wich were heretofore unknown in
the area, was determined. These however did not show the strong association
cited above.
NOME: RONALDO MELLO PEREIRA
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO ALUVIONAR SISTEMÁTICA APLICADA À REGIÃO DE
DIVINO DAS LARANJEIRAS - MG"
BANCA EXAMINADORA: HÉLIO MONTEIRO PENHA,
FERNANDO ROBERTO MENDES PIRES. AUGUSTO BAPTISTA
DATA DA DEFESA: 01 DE
DEZEMBRO
NO DO PROCESSO: 40.395/81
ABSTRACT: This research aimed to
evaluate the method of systematic alluvium prospecting applied to pegmatitic
areas. An area of 350 square kilometers approximately, in the central part of
the Eastern Brazil Pegmatitic Province was selected; for the studies, and the
town of Divino de Lanranjeiras, MG was selected as a field base. Geologically
the terrain is covered by the Formação São Tomé, Rio Doce Group, which contains
intrusive granitoid rocks, like the Galilea Tonalite and the Palmital
Granodiorito, all Precambrian in age. The research was developed into two
phases: - fiedl work where all creeks were systematically sampled; when never
possible a minimum of 1000 meters spacing between sampling sites was kept. A
total of 82 samples were collected. - a laboratory study, where the samples were
physically splitted and sirved; factor fracting coas made using heavy liquits
and eletromagnetic methods, followed by mineral identification. 36 minerals were
described and 17 maps showing the mineral distribution were prepared. Whenever
possible provenance and mineral associations were commented. The research
presented results, detecting most the previously known occurrences like
cassiterite, columbite-tentalite, spodumene, ambligonite, monazite, etc. and
also detecting two minerals not yet described (scheelite and anatase) as well as
some labile minerals like "gumite" and Fe-Mn phosphate. Some considerations
about the sampling and the role of the alluvium were made.
NOME: MARIA DO CARMO BUSTAMANTE JUNHO
ORIENTADOR: HÉLIO MONTEIRO
PENHA
TÍTULO: "GEOLOGIA, PETROLOGIA E GEOQUÍMICA PRELIMINAR DO GRANITO
TERESÓPOLIS, RJ"
BANCA EXAMINADORA: JOEL GOMES VALENÇA, FERNANDO ROBERTO
MENDES PIRES, J. HANS DANIEL SCHORSCHER, RITA ALVES BARBOSA, RUDOLPH ALLARD
JOHANNES TROUW (suplente)
DATA DA DEFESA: 17 DE JUNHO
NO DO PROCESSO:
3.260/82
ABSTRACT: The mapping here presented was held in a pre-Cambrian area
comprising migmatitic gneises, cut by orthogneisses and post-tectonic granites,
as well as basaltic dykes of mesozoic age. The migmatitic gneisses are related
to the Santo Aleixo Unit (Penha et alii, 1979). They are acid gneisses with an
amphibolitic-tonalitic melanosome and a granitic leucosome. The main structures
present are of the stromatic type with minor structures such as nebulitic,
agmatic and porfiroblastic types. This unit is cut by orthogneisses of the Serra
dos Órgãos Batholith, (Grossi Sad et alii, 1980), represented by a (gr)-(hn)-bi
gneissic granite and by a gneissic leucogranite, which portrays an early phase
from this magmatism. In the area of the Batholith itself there are some other
kinds of intrusive rocks of a latter age and unknown origin. The migmatitic
gneisses and orthogneisses show two phases of deformation with NS (Fn-1) and
NE-SW (fn) as the main directions. Their mineralogical assemblages are from the
high grade amphibolitic facies, superposed by medium grade greenschist facies.
An acid to intermediate post-tectonic magmatism cut the gneisses into tabular
shaped bodies of various thickness distributed along a NE-SW regional trend. The
larger bodies show mainly subhorizontal dips and are sectioned by high angles
faults related to a rigid post-Cambrian tectonism. The main fault directions are
also coincident with those directions of Fn and Fn-1. We conclude that these
granites are allochthonous and post-tectonic. They are (hn)-bi monzogranites
with allanite and sphene, and show granodiorite and monzodiorite differentiates.
They are referred to this paper as the Teresópolis Granite. In the south of the
studied area the granites are gray colored, medium grained, with porphyritic
texture. The granites in the north are also gray, but fine-grained, with flow
structures and abundant "basic inclusions". These fine-grained granites form
also narrow dykes that cut the medium grained granite and the gneisses. They are
cut by pegmatites and by dykes of a pink leucogranite, which is the last
intrusive phase of this magmatism. The inclusions show the same mineralogy as
that of the granites and are of two different types. The "surmicaceous" type is
composed basically of mafic minerals and the "microgranular" type is composed of
andesite to quartzo-andesite igneous rock, with igenous textures. They most
probably are autoliths or restites. The chemical analyses of these granites
indicate a magma of trondhjemitic (soda rapakivitic) composition, with a
relative potassium enrichment. The pattern of magmatic evolution suggests a
trend calc-alkaline. Correlations and comparisons between the Teresópolis
Granite and the Andorinha (Penha et alii, 1979a), (Zorita, 1978), Ipiranga
(Puget, 1979), Nova Friburgo e Sana (Grossi Sad et alii, 1978 e 1981) granites
reveal structural, petrographic and geochemical similarities. These features
show that the Teresópolis Granite and the other granites above have some
aftinities with granites of the I-type (Pitcher, in Atherton e Tarney, 1979)
derived by anatexis from basic continental crust.
NOME: PAULO ROBERTO OLIVA
ORIENTADOR: JACQUES PIERRE CASSEDANNE
TÍTULO:
"PROSPECÇÃO COM BATEIA NA REGIÃO PEGMATÍTICA DA GOLCONDA - MUNICÍPIO DE
GOVERNADOR VALADARES - MINAS GERAIS"
BANCA EXAMINADORA: FERNANDO ROBERTO
MENDES PIRES, HÉLIO MONTEIRO PENHA, AUGUSTO BAPTISTA
DATA DA DEFESA: 29 DE
ABRIL
NO DO PROCESSO: 13.354/83
ABSTRACT: An alluvial exploration with
panning was carried out in a area of approximately 140Km2 , located 20Km NW of
the Governador Valadares city in the State of Minas Gerais. Geologically the
terrain consists of Precambrian biotite gneiss at times cataclastic with layers
of amphibolite and pegmatites. The sampling programme involved the sampling of
135 active stream samples in a grid approximately 1km2 in the Onça and São
Domingos rivers and their respective tributaries. Thirty-eight minerals were
described. Dravite was found in this area for the first time. Trough this
research, it was possible to distinguish the following mineralogical
assemblages: 1) biotite, garnet, sillimanite and zircon characterize the gneiss.
2) amphiboles, epidote, dravite and pyrite relate with the amphibolites. 3)
ambligonite, autunite, beryl, cassiterite, columbite-tantalite, spinel,
espodumere, lepidolite, microlite, topaz, tourmalines characterize the
pegmatites. In the Onça river beryl loses approximately 75% of its size along
the distance of 12km, while in the São Domingos river cassiterite and
columbite-tantalite show a size reduction of about 80% and 60% in 7km and 3km
respectively. The minerals carried along the Onça river to the Doce river
include amphiboles, dravite, garnet, ilmenite, limonite, magnetite, malacon,
monazite, muscovite, quartz, rutile, sillimanite, tourmalines and zircon.
NOME: JOSÉ LUIZ PEIXOTO NEVES
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO ALUVIONAR NA REGIÃO PEGMATÍTICA DE GALILÉIA -
MINAS GERAIS"
BANCA EXAMINADORA: FERNANDO ROBERTO MENDES PIRES, HÉLIO
MONTEIRO PENHA, AUGUSTO BAPTISTA
DATA DA DEFESA: 13 DE DEZEMBRO
NO DO
PROCESSO: 008572/83-9
RÉSUMÉ: Cette recherche a eu pour but de dester la
méthode de prospection alluvionnaire dans la région pegmatitique de Galiléia
(MG). Les pegmatites de cette région sont encaissées dans les micashistes de la
Formation são Tomé, dans la Tonalite Galiléia, dans la Granodiorite Palmital et
dans le Granite Urucum, tous datés du Précambrien. Le travail a été divisé en
deux étapes: 1) Travail de terrain - Il a consisté dans un échantillonnage
systématique suivant une maille de 1km. 87échantillons ont été collectés dans
les thalwegs et concentrés à la batée. 2) Travail de laboratoire - Il a consisté
dans la séparation des concentrés et l'identification de leurs constituants. 28
minéraux on été d`terminés et décrits. A partir des résultats obtenus des cartes
de distribution ont été réalisées. Le comportement des minéraux, leurs
associations et leur provenance ont été discutés. Les résultats obtenus sont
trés satisfaisants: les indices déjá connus en place ont été retrouvés en
alluvions (spoduméne, chalcopyrite, cassitérite) et de nouveaux ont été
découverts (scheelite, anatase, or, chrysobéryl) qui démontrent l'efficience de
la méthode.
NOME: EDUARDO GOMES DOS SANTOS
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "MINERALOGIA E ZONEOGRAFIA DO CAMPO PEGMATÍTICO DA
GOLCONDA - MUNICÍPIO DE GOVERNADOR VALADARES - MG"
BANCA EXAMINADORA: AUGUSTO
BAPTISTA, FERNANDO ROBERTO MENDES PIRES, HÉLIO MONTEIRO PENHA
DATA DA DEFESA:
13 DE AGOSTO
NO DO PROCESSO: 017398/85-96
ABSTRACT: The pegmatites of the
Golconda Region occur preferentially embedded in the biotite and cataclastic
gnaisses inserted with beds of amphibolites Precambrian in age related to the
Paraíba do Sul Group. Two very distinct types occur. One characterized by simple
mineralogy and structure, and the other, by complex mineralogy and zoned
structure. Pegmatites of the first type occur in geomorphologic marsh unit and
those of the second type occur predominantly in the hills (Serra dos Ferreiras)
and, when they do not appear zoned, they show themselves albitized to divide the
area into two different domains. The description of identified minerals and data
about the orientation of pegmatties, forms, sizes and relation with the wall
rock, are presented in the text and are included in the index cards of the
individual description of the pegmatites that constitue the attachment. It must
be noted that the principal mining activity of the area is primitive mining for
columbite-tantalite and gems. Many are the remaning mining sites from the 40's
and 50's presently abandoned and/or completely caved in, obstructing the direct
access for study of its mineralogy, which obliged the use of panning for
concentration of the wastes and posterior processing in laborators. The
pegmatites product feldspar, mica, beryl, columbite, tantalite and gems.
NOME: MARÍLIA INÊS MENDES BARBOSA
ORIENTADOR: FERNANDO ROBERTO MENDES
PIRES
TÍTULO: "GEOQUÍMICA DAS FAIXAS MÁFICAS-ULTRAMÁFICAS, PLUTONITOS E
MIGMATITOS DO GREENSTONE BELT BARBACENA, NA REGIÃO DE CONSELHEIRO LAFAIETE
(MG)"
BANCA EXAMINADORA: JOEL GOMES VALENÇA, RUDOLPH ALLARD JOHANNES TROUW,
EDUARDO ANTONIO LADEIRA
DATA DA DEFESA: 30 DE SETEMBRO
NO DO PROCESSO:
021661/85-23
ABSTRACT: The geology of the manganiferous district of
Conselheiro Lafaiete, at the southern portion of the Minas Gerais State,
represents a fraction of typical granite-greenstone province. Precambrian
metamorphic rocks of different ages which outcrop in the region, have an
apparent basement composed of migmatitic-gneissic complex of the Mantiqueira
Group. Barbacena Group Barbacena Group comprises a volcanicplutonic assemblage
similar to those classified as Greenstone Belt. The lowermost unit of the
Barbacena Group is constituted by ultramafic rocks, talc chorite schists at
present, compositionnally similar to the basaltic komatiites of several archean
Greenstone Belts, and equivalent to phanerozoic periodites. They are marked by
high-Mgo content (> 19%), low values for alkalis (mainly K20 <0,1%),
relative enrichment in Cr and Ni, and odd ratios CaO/A12O3 (@ 1), although
sometimes this ratio been affected by seletive decalcificationj and a slight
enrichment in aluminium. The rocks have similar geochemical trend to the ocean
floor basalts (OFB). The mafic rocks of the Barbacena Group, represented by
amphibolites and amphibole shists, correspond to the middle stratigraphic unit
and spatially widespread. They are correlated in the archean Greenstone Belts to
basalts and andesites of the tholeiitic series (TH)
NOME: ARIADNE DO CARMO FONSECA
ORIENTADOR: FERNANDO ROBERTO MENDES
PIRES
TÍTULO: "GEOCRONOLOGIA DAS ROCHAS GRANÍTICAS E SUAS ENCAIXANTES NA
CIDADE DO RIO DE JANEIRO, RJ"
BANCA EXAMINADORA: JOEL GOMES VALENÇA, UMBERTO
CORDANI, RITA ALVES BARBOSA
DATA DA DEFESA: 03 DE MARÇO
NO DO PROCESSO:
2.281/86-16
ABSTRACT: In this work are presented the analytical results
obtained by Rb-Sr and K-Ar isotopic and fission-tracks dating methods of some
metamorphic and igneous rocks outcroping in the Rio de Janeiro city. The
strongly deformed gneissic rocks were generated under conditions of pressure and
temperature related to high grade metamorphism. Magmatic rocks of basic and acid
compositions, deformed or not, intrude the metamorphic sequence. Dykes of
basalt, diabase and alkaline rocks related to Mesozoic tectonism occur elsewhere
in the area. The whole rock Rb-Sr isochron age are characteristic of the
Brazilian Cycle. The ages between 750 and 550m.y. are related to the tectonic
phase, with deformation, metamorphism and anatexis of magmatic precursors and
preexistent crustal materials and the intrusion of gabbroic and granodioritic
magmas. The intrusion of late and post-tectonic granites occurred between 550
and 450m.y. The comparison between initial ratios and petrographic studies
suggests different origins for the metamorphic rocks: either magmatic
precursors, which probably generated the gneisses of Inferior Serie and
plagioclase-gneisses, or preexistent materials, which may have generated
leptinites and biotite gneisses. However the elevate initial ratios don't
determine if the leptinites and biotite-gneisses were formed by the metamorphism
and anatexis of brazilian sediments or rejuvenesce of the older metamorphic
crustal rocks. The K-Ar age of 476m.a. in hornblende, of anfibolite, is related
to regional cooling fo the Brazilian Cycle. However the ages of plagioclase of
diorites are discordant, either older or younger than other ages. Pission-tracks
dating in apatites, of two diorites and one plagioclase-gneiss, produced ages in
the interval between 85 and 124m.y. These dates represent the cooling below
110oC (retention temperature of fission tracks in apatite) of the rocks,
interpreted as consequence of ascensional movements associated with the
continental uplift, resulting of the mantle intumescence, during South Atlantic
opening.
NOME: TARCÍSIO PEREIRA DA CUNHA
ORIENTADOR: PÉRSIO DE SOUZA
SANTOS
TÍTULO: "DESENVOLVIMENTO DE MÉTODO PARA ESTUDO DOS MINERAIS DOS
FOLHELHOS OLEÍGENOS DA FORMAÇÃO IRATI"
BANCA EXAMINADORA: FRANKLIN DOS SANTOS
ANTUNES, ELMO DA SILVA AMADOR, IGNACIO AURELIANO MACHADO BRITO
DATA DA
DEFESA: 21 DE MAIO
NO DO PROCESSO: 009865/86-95
ABSTRACT: This work is
about the mineralogy of Irati Formation shales employed by Petrobrás in the
Petrosix Process in São Mateus do Sul (Paraná). The study involved the
developement of a method in which cementing agents were "degraded", allowing the
separation of individual minerals and their mineralogical classification. The
work was carried out through two stages. In the first stage the shales were
characterized through chemical and mineralogical analysis, followed by an
evaluation of the effect of cementation on Shales minerals. During this stage
the most cemented rocks - the oil shales were also determined These results led
to the definition of "xisto original de processo" from Petrosix Process as the
representative sample of the cemented materials. Eighth cement degradation
methods were applied to this representative sample and evaluated through X-Ray
difractometry and infrared spectroscopy of the resulting materials. From these
results a analysis route was defined and applied throughout this work. The
second stage involved the granulometric and mineralogical analysis of the
resulting materials, and the results defined the largest particle sice that
could be used with the method. The results of mineralogical analysis have also
shown that "xisto Original de Processo" consists of quartz, plagioclase,
feldspar, mica and the clays kaolim illite and montmorillonite. It was concluded
that the main cementing agent consists of organic matter and that the clays are
bound to the cementing agent. It was also carried out a quantitative
mineralogical analysis through physical, chemical and granulometric methods.
NOME: EURICO ZIMBRES
ORIENTADOR: JACQUES PIERRE CASSEDANNE
TÍTULO:
"PROSPECÇÃO COM BATEIA NO MACIÇO ALCALINO DE CANAÃ E ADJACÊNCIAS, MUNICÍPIO DE
DUQUE DE CAXIAS - RJ"
ABSTRACT: In this work was used panning over a
Precambrian basement complex area with alkaline rocks (Canaã Massif). In the
field phase, alluvional and elluvional samples were systematically collected
according to a 500 meters grid. These samples were, then, submited to a routine
laboratory work (heavy liquid and isodynamic separation etc.). Heavy minerals
were determined by optical examination under a binocular microscope and a
polarizing microscope and chemical methods. The results obtained from the work
above were ploted on 12 minerals distribution maps which allow to examine the
source and mineralogical association of each of these minerals. This study
permitted to find the following mineralogical associations: 1. Corundum, spinel
and zircon, related to alkaline rocks. 2. Ilmenite, sillimanite, almandine
garnet and monazite, related to granitic migmatites. Three blue gem corundum
occurrences related to alkalines pegmatites were discovered. Chemical
compositions of zircon and titanites were described.
NOME: MARIA ELIZABETH ZUCOLOTTO
ORIENTADOR: CRISTINA MARIA
WIEDEMANN
TÍTULO: "METEORITOS METÁLICOS, UMA VISÃO GERAL"
ABSTRACT: A
metallographic investigation of macro and microstructure,supported by microprobe
and X-ray examination, has been made in five Brazilian iron-meteorites. The
Soledade is lightly shocked coarse octahedrite, Og, rich in carbides. Bandwidth
2-4 mm, HV 225 ( 15, Neumann bands, subgrains, rhabdites, cohenite,
policrystaline troilite type 3 . Belongs to group IAB, with 6,78% Ni, 98.5 ppm
Ga, 420 ppm Ge, and 3.9 ppm Ir. This meteorite was briefly artificially
reheated. Pirapora is a shocked an reheated hexahedrite, H, formed by clear and
frost atching kamacite, with decorated and fresh Neumann bands, rhabdites
(giant, plate, clusters and microrhabdites), chromite and remelted troilite type
5. Belongs to group IIA, with 5.38% Ni, 59.5 ppm Ga, 190 ppm Ge, 28 ppm Ir. Nova
Petropolis is a shocked and annealed medium octahedrite, Om, Bandwidth 1.1 ( 0.1
mm, L/W ( 25, HV 170 ( 20. It presents annealed and decorated Neumann bands,
rhabdites, schreibersite and recrystalzied troilite type 4. Belongs to group
IIIA, with 7.65% Ni, 19.7 ppm Ga, 36.5 ppm Ge and 19.3 ppm Ir. Itutinga is a
shock hardened, medium octahedrite, Om. Bandwidth 1.0 ( 0.1 mm, L/W ( 25,
structure, presenting hardness range from HV 230 to 340. Neumann bands,
subgrains, rhabdites, carlsbergite and twinned troilite type 2. Belongs to group
IIIA, with 7.2% Ni, 18.6 ppm Ga, 36 ppm Ge and 13 ppm Ir. Sanclerlândia is a
lightly shocked medium octahedrite, Om, Bandwidth 1.0 ( 0.1 mm. It can be found
Neumann bands, HV 250 ( 20, subgrains, rhabdites, carlsbergite and lamellar
troilite daubreelite of type 1. Group IIIA, with 7.47% Ni, 11.6 ppm Ga, 36.4 ppm
Ge and 7.5 ppm Ir. Comparing the meteorites studied with other known brazilian
irons, we verify that: the Itutinga, Nova Petrópolis and Soledade are
independent irons. On the other hand, Sanclerlândia is closely related with the
Veríssimo (Go) iron. However a cross examination should be carried out to
determine if these two meteorites are a paired fall. Despite of the fact that
Pirapora and Angra dos Reis Iron are chemically and structurally closelly
related, there are some minerallogical differences (the presence of cohenite in
Angra dos Reis chromite in Pirapora) that put the paired fall hypoteses in
question.
NOME: NELSON CESAR CHAVES PINTO FURTADO
ORIENTADOR: CARLTON ANTHONY
TAFT
TÍTULO: "SOBRE A IMPORTÂNCIA DO ALKALIDITIOFERRATO, KFeS2, NA GÊNESE DO
MINERAL YAVAPAIITA"
ABSTRACT: This work describes the synthesis, experimental
methods and accesible theory in order to obtain in laboratory poli and mono
crystal synthetic iron sulphide KFeS2 Alkali-Di Thioferrate and subsequent
treatment of hidrogenation and oxygenation at high temperatures. It was thus
necessary to construct a special furnace with controlled atmosphere and pressure
which is shown in details permiting its reproduction. The monoclinic structure
of KFeS2 indicated lattice parameters of ao = 7.07Å, bo = 11.36Å, co = 5,41Å, (
= 112.76Å, similar to those found in the ASTM Files. The growth characterization
of the mono crystal using the Vertical BRIDGMAN Method is also discussed. The
crystals were grown at a velocity of 8 mm/hr (During a total period of 62 hours)
indicative a (110) cleavage plane. In this manner was possible to obtain
crystals with 40 mm length and 1 cm width. The changes observed in the samples
treated under vacuum and hydrogen atmosphere at a temperature of 500o C for a
period of 1 hour were similar indicating a new anstable phase coexisting with
that of the un-treated sample. In order to measure the quantify of hydrogen
absorved a high pressure reactor was used. Details of this experimental
procedure are given. The oxidation of KFeS2 was done at temperatures between 350
and 650o C yelding at 400o C the formation of the mineral yavapaiite Kfe (SO4)2.
NOME: RENATA ELIANE FRANK
ORIENTADOR: FERNANDO ROBERTO MENDES
PIRES
TÍTULO: "GEOLOGIA, PETROLOGIA E MINERALIZAÇÕES ESTANÍFERAS DO COMPLEXO
GRANÍTICO DE SANTA BÁRBARA, RONDÔNIA, BRASIL"
ABSTRACT: The Santa Barbara
Granitic Complex is a part of the Rondonian Tin Province. It displays a
subrounded shape in surface with a 6 km diameter. It is intrusive in the Xingu
Complex gneisses. Contacts with country rock are usually concealed by thick soil
cover, but blocks of the Xingu Complex milonitized biotite-rich Augen gneisses
in the northeastern boundaries of the Santa Barbara Granitic Complex suggest
tectonic contacts. Under the petrographic viewpoint, the Santa Barbara Complex
shows distinct primary(magmatic) and secondary(metasomatic) features
characterizing two lithologic facies. The primary facies represent about 90% of
the total exposed area of the complex and is subdivided into three granitic
types: 1) SERRA AZUL GRANITE (Gsa): dominant type, represented by a
coarse-grained equant biotite-granite, which usually occurs at the border zone
of the complex. 2) SERRA DO CICERO GRANITE (Gsc): marked by the porphyritic
texture and by the fact that encircles the Santa Barbara Granite. 3) SANTA
BARBARA GRANITE (Gsb): a fine-grained biotite-granite showing close
relationships with the mineralization. The granites of the complex exhibit high
SiO2 content (73-74%) and Al2O3, K2O, Na2O and CaO contents, which indicate
calcalkaline (Wright, 1969) and subaluminous compositions (Shand, 1927).
Granites are strongly differentiated. Trace-elements studies demonstrated
enrichments in F, Rb, Y, Li, Sn, Nb, Cu, Pb, Zn, Mo, Ce, La and Co, and
impoverishment in Ba and Sr. The late and post-magmatic or metasomatic events
are monitored by petrographic work and geochemical data. All the granites types
show in different proportions, late and post- magmatic and metassomatic
transformations (microclinization, albitization, silicification and
greisenization). During the greisenization process the topaz was formed at the
expenses of the feldspar breakdown. Muscovitization of biotite and feldspars and
the cassiterite precipitation, correspond to the principal hydrotermal
alterations in the greisens. Tin mineralizations (primary and secondary) are
intimately associated with the Santa Barbara Granitic Complex. Primary
mineralizations occur either as endogreisen, exogreisen or quartz-veins,
controlled by the fracture system oriented following the northeast - southwest
direction. These fractures were active during the emplacement of the granites.
Secondary tin mineralizations are the product of the intense weathering of the
granites which afforded erratic, high grade cassiterite concentrations in the
present valleys and palaeovalleys. The positioning of the Santa Barbara Granitic
Complex is related to an intracontinental rifting and can be explained by the
granite intrusion model controlled by zones of crustal weakness and partial
melting, involving the Serra Providencia granite, the probable precursor of the
Rondonian Granites.
NOME: JULIO CEZAR MENDES
ORIENTADOR: CRISTINA MARIA WIEDEMANN
TÍTULO:
"GEOLOGIA E PETROLOGIA DO COMPLEXO INTRUSIVO DE RIO NOVO DO SUL
-ES"
ABSTRACT: This thesis comprises the geological mapping (scale 1:25.000)
and interpretation of an area about 80 km2 in the south of the state of Espírito
Santo, near the town of Rio Novo do Sul. The area contains several intrusive
bodies (The Rio Novo do Sul Intrusive Complex) with rock composition ranging
from quartz-diorites to granites (intermediate rocks are quartz-monzodiorites,
quartz-monzonites, tonalites and granodiorites), which are enclosed in
orthogneisses of Braziliano age and migmatitic banded gneisses
(sillimanite-garnet gneisses) of probably Transamazonic age. All these rocks are
part of the Alegre Complex, which belongs to the Ribeira Mobile Belt, of
Braziliano age. Magnetic data show a strong anomaly in the region, indicating
the presence of a large subsurface structure of basic magmatic body. This,
combined with the irregular shape of intrusions mapped on the surface could
indicate that they represent a set of apophyses and stocks. Dominating among the
intrusive rocks are homogeneous granodiorites and quartz-diorites. The other
lithologies outcrop only in isolated areas or in mixed zones of rocks.
Sometimes, restricted compositional variations may occur. There are well
developed flow structures (linear or planar) that tend to be paralell to the
schistosity of the enclosed rocks. The degree of deformation of the intrusive is
not significant. Homogeneous rocks whithout structural complications are
prevailing, and only in some quartz-dioritic portions it is possible to observe
turbulent flow structure, small shear zones and/or faulted syn-intrusive veins.
The contacts between the enclosing rocks and the several rock units of the
complex rarely crop out. In the mixed zones of rocks sharp and irregular veined
contacts are found, as well as pillow-like structures. Many granitic dykes and
quartz-feldspatic veins cut all the lithologies, showing an irregular strike and
shape. Microdiorite dykes of small thickness cut mainly the gneisses, having
melted them in some points. The petrographic characteristics of the intrusive
rocks are repetitive. They all have a similar mineralogy and predominantly
hipidiomorphic granular and porphiritic texture. The dominant potash feldspar is
microcline, commonly of microperthitic type. Amphibole of probably
iron-hastingsitic composition is well observed in the diorites, and not present
in the granites, while in the granodiorites it occurs in trace amounts. In
several samples this mineral appears replaced by biotite, and in only on thin
section of quartz-diorite it rims augitic pyroxene. Reaction contacts can be
found, as examplified by plagioclase corroded by microcline and vice versa, as
well as intergrowths between quartz and microcline (graphic intergrowth) and
quartz and plagioclase (myrmekite). The plagioclases and biotites determine the
primary foliation of the rocks that show flow structure. In microdiorites, the
plagioclase can exhibit corroded borders. Apatite and zircon are the accessory
minerals most common il all lithologies. The chemistry of the rocks from Rio
Novo do Sul Complex reveals a magmatism rich in some elements, such as Fe, K, Ti
and P (mainly granodiorites and quartz-diorites) and slightly depleted in Na, in
comparison with an average of analyses from the literature. The different
lithologies have a peraluminous character (i.e., Al2O3/Na2O + K2O + CaO 1,1),
and are oversatured in SiO2, according to their petrographic and normative
composition. With regard to the determination of the petrogenetic type of the
granitoids, the magnetite-series rocks predominate. The study of several
diagrams points to characteristics corresponding to I-type and S-type magmas, as
well as to a calc-alkaline/alkali-calcic character of this complex. The whole
geochemical data indicate an origin of magmas produced in a transitional
environment (end of a compressive cycle/beginning of extensive cycle).
Fractional crystallization processes seem to play a major role on the genesis of
the intrusive rocks of Rio Novo do Sul. Nevertheless, mechanisms of partial
fusion and magma mixing were probably important. The Rio Novo do Sul Intrusive
Complex shows similar characteristics to other intrusive complexes from the
southern part of Espírito Santo, such as the Castelo and Iconha Intrusions.
NOME: ISABEL PEREIRA LUDKA
ORIENTADOR: CRISTINA MARIA WIEDEMANN
TÍTULO:
"GEOLOGIA, PETROLOGIA E GEOQUÍMICA DO COMPLEXO INTRUSIVO JACUTINGA-TORRE, MIMOSO
DO SUL, ES"
ABSTRACT: A small portion of the Ribeira Mobile Belt
(Brasiliano/Panafrican in age) was studied in detail by focussing the
Jacutinga-Torre Intrusive Complex in the neighbourhood of Mimoso do Sul in
southern Espírito Santo. Geological mapping (1:25.000) of the intrusive units as
well as of their enclosing rocks revealed three individual magmatic bodies: the
Torre, the Jacutinga and an orthogneissic unit of regional expression. The Torre
unit comprises three roughly concentric domains of melanocratic to leucocratic
igneous rocks, grading from diorites to quartzmonzonites, with the predominance
of monzodiorites and monzonites. The Jacutinga unit comprises meta-gabroic rocks
and is separated from the Torre intrusion by a string of orthogneissic rocks,
thant, on the other hand, seem to be intimately related to the meta-gabroic
rocks of Jacutiga. The enclosing rocks to this sequence consist of migmatitic
banded gneisses associated with sillimanite-quartzites. The schistosity of these
banded gneisses is sub-horizontal near the city of Mimoso do Sul, turning to
sub-vertical around the contacts of the intrusive Torre structure, where it dips
towards its center. A migmatitic ring (granitization ring) grading to a
diatexite of leuco-granitic composition characterizes this border region. The
Torre intrusive body shows an inversed zoned diapiric structure, with
sub-vertical dipping flow structures, grading from a centimeter to a meter
scale. Igneous lamination as well as bedding can be clearly observed. The
predominant minerals are mesoperthite (K-feldspar and plagioclase An25-35
intergrowth) plagioclases An25-35, microcline, titaniferous biotite, Fe-augite
and hypersthene. At the border plagioclase and microcline occur as separated
phases. The microcline is only found at the external domain. The clinopyroxenes
(calcium-rich Fe-augites) are restricted to the two inner zones. They are
replaced by amphibole at the external zone. Orthopyroxene (hypersthene) may be
locally found in the internal zone. Geochemical analyses on whole rock samples
of the Torre intrusive show high K contents and a very low Rb/Sr ratio, due to
the high Sr content. These rocks show calc-alkaline-monzonitic (high K) to
alkaline trend. Two genetic hypothesis for the magma generation are discussed:
diversification from one parental magma or homogenization of two parental magmas
followed by diversification. The age of the massif (490 My., U-Pb in zircon,
SOLLNER, pers. com.), associated with the alkaline tendency showing by these
rocks, points towards the magmatic-arc maturation, in a distensional tectonic
phase. The meta-gabbroic body of Jacutinga comprises gabbro-noritic rocks. The
rock composition is variable, grading from very fine grained melanocratic
meta-gabbros up to coarse-grained leucocratic meta-gabbros. This suggests an
internal structure similar to that of the Torre intrusion. Almost all these
Jacutinga rocks show a primary mineral orientation. Despite of these preserved
igneous structures, some metamorphic features are observed: hornblende
poikiloblasts (evolved from the original minerals), garnet (occurring along
fractures) and corona structures (olivine-plagioclase contacts). The metamorphic
effects changed the chemistry of these rocks, leading to an open system, with
water supply and a probable contamination and mobilization of some elements (Na,
K, Rb, Sr). Nevertheless a tholeiitic trend of the original magma can still be
recognized.
NOME: PATRÍCIA BARBOSA DE ALBUQUERQUE SGARBI
ORIENTADOR: JOEL GOMES
VALENÇA
TÍTULO: "PETROGRAFIA E GEOQUÍMICA DA FORMAÇÃO MATA DA CORDA NA REGIÃO
DE CARMO DO PARANAÍBA, MG"
ABSTRACT: This work focuses on relevant
geological, mineralogical, petrographic and chemical features of the lavas and
subvolcanic rocks of the Mata da Corda formation, as well as on the mode of
occurrence and petrographic features of the volcanoclastic and epiclastic rocks
of the same formation. The studied area, around 450 km2, is situated near the
town of Carmo do Parnaíba (western Minas Gerais state), being part of the
Cretaceous Sanfranciscan basin. This basin, represented by the Areado and the
Mata da Corda formations, is 500 m thick and unconformably overlies folded
metapelites of the Upper Proterozoic Bambuí group. The Areado formation (Lower
Cretaceous) consists of fluvial polimitic conglomerates (Abaeté member),
lacustrine shales, sandstones, limestones and marls (Quiricó member), and
aeolian and fluvio-deltaic sandstones (Três Barras member). The Mata da Corda
formation (Upper Cretaceous) overlies the latter formation, separated by local
erosive unconformities. It comprises a 40 to 80 m thick pile of K-rich mafic to
ultramafic alkaline lavas (Patos facies), volcanic conglomerates and sandstones
(Capacete facies) and clayey sandstones with little volcanic contribution
(Urucuia facies). The lavas and non-volcanoclastic rocks have a larger spatial
distribution and are volumetrically more significant than the volcanoclastic
rocks. The lavas form small exposures (frequently, very weathered) of massive
thin horizontal and subhorizontal, poorly-vesiculated flows (in places,
individually, not exceeding 0,5 m thick). In some outcrops, the extrapolated
thickness of a sequence of flows may reach 10 m. According to the IUGS
classification (Streckeisen, 1980) the Mata da Corda lavas are ultramafilites,
mafitites, leucitites and kalsilitites. These ultramafitites and mafitites have
unidentified felsic phase(s) and estimated values (vol. %) of mafic index from
80 to 70 and 60 to 70, respectively; where as the leucitites and kalsilitites
contain leucite (pseudomorphs) and kalsilite (pseudomorphs and fresh and clear
grains), and get their names from that more abundant felsic phase. All these
lavas are all feldspar-free, with plentiful abundant clinopyroxene (mostly,
diopside), perowskite and Ti-magnetite, and show very fine to meduim-grained
porphyritic to seriated textures. An interstitial material is always present and
often intensely altered to zeolites ans clay minerals. In some rocks it has been
determined as kalsilite based on electron microprobe analysis; but in other
rocks this material could not be accurately identified and it has been modally
considered as an unidentified felsic phase. The ultramafitites and mafitites are
porphyritic to seriated rocks. The porphyritic types show phenocrysts and
microphenocrysts (up to 20 vol. %, and 0,2 to 2.0 mm in size) of olivine
(Fo91-84), clinopyroxene (diopside), perowskite, Ti-magnetite, melilite
(euhedral and subhedral pseudomorphs), apatite and phlogopite (rarely, as 3.0 mm
large plates). The very fine to fine-grained groundmass has clinopyroxene
(diopside, up to 40%), Ti-magnetite, perowskite unidentified interstitial
material, and may also contain minor amounts of phlogopite and apatite. The
seriated types have coarser grains but are modally and mineralogically akin to
the previous types. The leucitites and kalsilitites are very similar fine to
medium-grained rocks, very frequently with a typical seriated texture. Some of
then, however, may develop textures which resemble those of the ultramafitites
and mafitites. Mineralogically, the leucitites and kalsilitites are similar to
the latter groups of rock, with the exception that they contain leucite
(subhedral pseudomorphs) and kalsilite (euhedral pseudomorphs and/or anhedral
fresh grains). Both feldspathoids occur as essential phases in the seriated
leucitites and kalsilitites or in the very fine-grained intergranular groundmass
of the porphyritic leucitites. In these porphyritic rocks, these feldspathoids,
in spite of being found in the groundmass, are absent from the phenocrysts and
microphenocrysts, which consists of clinopyroxene (diopside to salite),
Ti-magnetite, apatite and perowskite. The above mentioned rocks (usually, the
fine-grained type) may contain scarce and small (mostly, <20 mm across)
cognate inclusions of fine to medium-grained cumulate rocks, consisting of
diopside, perowskite, Ti-magnetite, phlogopite and kalsilite. Most commonly, the
inclusions are kalsilite pyroxenites, but more rarely, perowskite modally
dominates and they become kalsilite "perowskitites". In both cases, kalsilite is
an interstitial phase. Thirty one samples of the Mata da Corda lavas have been
chemically analysed. These data indicate that the lavas are all ultrabasic.
Fourteen of these samples, which showed more important signs of secondary
oxidation and other kinds of alteration, were separated. The other
representative rocks were subdivided in two groups (GI and GII), according to
the K2O/Na2O and K2O values. GI is potassic and has (WT%) SiO2="38-42,"
TiO2="5-7," Al2O3="5-8," Fe2O3="4-5," FeO="8-9," MgO="8-14," CaO="11-17,"
K2O="1-3" and Na2O>0-2; whereas GII is ultrapotassic, with (WT%) SiO2=43-45,
TiO2=5-8, Al2O3=7-9, Fe2O3=3-4, FeO=7-9, MgO=8-9, CaO=8-12, K2O=4-7 and
Na2O>0-2. (2) In the Na2O+K2O versus SiO2 plot, the compositions delineate a
trend from moderately (GI) to strongly (GII) alkaline. (3) The compositional
spectrum of the lavas shows mainly non-linear variation trends of increasing
SiO2, Al2O3, K2O, Na2O, Nb, Zr and Y, and decreasing FeO, CaO, Cr and Co, with
decreasing MgO. (4) Discrimination diagrams using SiO2, CaO, MgO, and FeO (total
iron) exhibit most lava compositions in fields of kamafugitic affinity.
NOME: FLÁVIO WOLFF
ORIENTADOR: JOEL GOMES VALENÇA
TÍTULO:
"CARACTERIZAÇÃO PETROGRÁFICA, LITOGEOQUÍMICA, QUÍMICA MINERAL E GEOTERMOMETRIA
DE ROCHAS DE ALTO GRAU METAMÓRFICO DO COMPLEXO ANÁPOLIS-ITAUÇÚ,
GOIÁS"
ABSTRACT: The Anapolis-Itauú Complex, in Goias State, Brazil, is part
of the Alfenas granulitic belt. The complex is composed mainly of rocks of the
amphibolite/granulite facies, showing often, effects of the role played by very
intense tectonic processes. This renders difficult the identification of the
boudaries between these rocks in terms of their different origins. In this work
besides rocks of a lower metamorphic grade, TH1 and TH2 types of ocean
tholeiites and an igneous calc-alkaline sequence, both metamorphosed under
granulite facies conditions, are also identified. Concerning the
sedimentary-derived high-grade rocks, the overall data indicate the presence of
granulitic rocks derived from original materials whose compositon approximate
those of the pelite-graywacke compositional range. In this context, a thought is
advanced that among these granulitic rocks, some may also have originated by
recrystallization of leucosomatic material derived by partial melting of these
sedimentary components. Observed parageneses and other kinds of evidence suggest
that the granulitic rocks formed under two different pressure regimes, of which
an earlier low-pressure type was followed by a medium to high-pressure type. At
present, the characteristic minerals assemblages assigned to the latter type arc
widely dominant in the studied rocks. The geothermometric results indicate that
these high-grade mineral assemblages achieved an equilibrium temperature around
800oC (opx-cpx pair). The amphibolite facies rocks predominantly correspond to
portions of a TTG terrain involved in the granulitic belt, remmants of overlying
supracrustal rocks or to elongated portions of retrogressive granulitic rocks,
these widely controled by tectonic dynamics. The lithogeochemistry, attached to
the lithological association found in this work points to the possibility that
part of studied area corresponds to a granulitized plutonic segment of a root of
greenstone belt. With regard to granulitized calc-alkaline sequence mentioned
above, it may be interpreted as representing ancient magmatic are rocks
associated with a tectonic setting somewhat analogous to a modern orogenic
continental margin.
NOME: THAÍS CRISTINA DE MONTE ALVERNE VARGAS
ORIENTADOR: JACQUES PIERRE
CASSEDANNE
TÍTULO: "PROSPECÇÃO ALUVIONAR E RECONHECIMENTOS GEOLÓGICO E
GEOMORFOLÓGICO DA REGIÃO PRODUTORA DE CRISOBERILOS PADRE PARAÍSO - AMERICANAS
(ESTADO DE MINAS GERAIS - MG)"
ABSTRACT: This research was achieved by using
the conventional method of prospection based on the panning of old alluvium
overburdens, river beds, fluvial terraces, colluvium and pegmatites. Such a
procedure was applied in order to determine the host rock of the chrysoberyl
found in the Padre Paraíso - Americanas region, in the northeastern part of the
Minas Gerais State. In order to define the relation between the deposits and the
local basement rocks, a geological mapping of the area was also carried out.
Studies on the morphological and climatic conditions associated with effect of
recent cycles of erosion, as well as the main features of the detritic deposits
allowed the reconstruction of the landscape and the depositional regimes, and
the estimates of age of the detritical deposits with the chrysoberyl-bearing bed
gravel. All the types of mineral occurrences found in the area were also
described. The results show that chrysoberyl is found in old alluvium deposits
of pleistocenic and holocenic ages, whose host rocks are suggested to be simple
non-zoned pegmatites, which intrude granitoids of granitic to granodioritic
compositions and monzogranites, weathered by recent erosion cycles. The location
of the studied samples and the distribution contours (in weight %) of their main
mineralogies on the geological map, allow to depict the relations between the
mineral occurrences and their probable source rocks. A geomorphological map is
also presented, in which main features of surfaces of erosion present in the
area are briefly discussed.
NOME: AMIN MURAD
ORIENTADOR: CRISTINA MARIA WIEDEMANN
TÍTULO:
"GEOLOGIA, PETROGRAFIA E GEOQUÍMICA (ELEMENTOS MAIORES E MENORES E ALGUNS
TRAÇOS) DO MACIÇO INTRUSIVO DE CONCEIÇÃO DE MUQUI - ES"
ABSTRACT: The
Conceição de Muqui igneous complex is located in southern Espírito Santo state
and covers about 50 km2 of outcrop area. In the eastern border of the outcrop
area it is emplaced in schistoid biotite porfiroblastic gneisses. In the
northern and western border it is emplaced in migmatitic gneisses and at the
southern border into a orthogneissic sequence associated with amphibolites and
banded migmatitic gneisses. The intrusive body consists of 4 petrographic and
trasitionals domains: 1) Mixed Zone A (at central-eastern border) consists of a
strong interfingering of irregular rock bodies of monzonitic to dioritic
composition (mainly monzodiorites), with a medium to coarse granular texture and
incipient planar flow layering. 2) Mixed Zone B (at southern border), consists
of more melanocratic, irregular and interfingering fine-grained rock bodies with
monzonitic to dioritic compositions, with strong planar flow layering cut by
felsic more leucocratic coarse-grained rocks in a network pattern. 3) Monzonitic
Rocks (mainly at western border), it is one of the most homogeneous unities of
the intrusive massif; it consists of a coarse-grained leucocratic rock. The flow
structures were slightly developed in the central zones and strongly developed
on the borders. 4) Granitic Rocks (mainly at northern border) consist of medium
to coarse grained rocks which basically corresponds to an increase of quartz
content in the monzonitic rocks. The intrusion is rich in sin-to-post-intrusive
dikes, with dioritic to granitic compositions, intermediary composition also
exists. The more felsic ones shows the younger relative ages. A post-intrusive
phase consists of granitic rocks rich in enclaves, some of them containing
quartz-plagioclase-titanite-allanite amygdals. Its is remarkable the composition
and the interrelation evolution among feldspars. Calcic plagioclase evolves to a
less sodic one. Later they became surrounded by poorly twinned alcalifeldspars,
and/or micro-grained to coarse-grainde, mesoperthites. Microcline with
plagioclase nucleous evolves towards a microperthitic texture with a
non-perthitic border. The micro grained mesoperthites occurs mainly at the
mesocratic monzonites and monzodiorites; where as the leucratic monzonites,
shows coarse grained mesoperthites. The interrelation becomes simpler on the
granites, where the feldspars are homogeneous. The main mafic mineral is
biotite, which usually surrounds amphiboles (Fe-Hastingsite). Crystals of
piroxenes (Fe-Augite and Hypersthene) occur predominantly in mafic phases,
rarely evolving to amphiboles and biotites. The main accessory minerals are:
titanite; allanite and zircon (more felsic phases); pyrite; magnetite; hematite;
muscovite and apatite, which increases in size and amount in the mafic phases.
The rocks analysed in this study belong to the High-K Monzonitic Calc-alkaline
Trend (LAMEYRE & BOWDEN, 1982). The planar and/or linear flow structures are
well preserved, dipping sub-horizontally in the central part of the intrusion to
sub-vertically, mostly in the marginal areas. Marginal shears striking radially
are common. Country rocks septa and xenolithes are abundant inside the
intrusion, often discordant with foliations of the flow structures. These facts
suggest, that the intrusive massif has a shallower erosion level than other
studied massifs in the region. Thirty three lithogeochemical analysis showed an
alkaline trend, with normative nepheline and an agpaitic index ( 1, Na/K ratio
> 1, in about 50% of basic rock groups, and an inversion of this in most of
the intermediary and acid rocks. High amounts of K, P, Ba, Sr and Zr are
indicative of incompatible elements in the more basic rocks. Anomalous amounts
of Cr and Ni in quartz-monzonites and granites suggest a mantellic source
influence in the acid rocks origin. Based on field, petrographic and geochemical
data assemblage, plus regional geochronological data and comparison with
neighbouring massifs, the age of the intrusive body is suggested herein as
Precambrian - end of the Brasiliano Cycle. The placement environment would
alternate from extensional to compressional, which is very common at the end of
any tectonic cycle.
NOME: MARIA LOURDES SOUZA FERNANDES
ORIENTADOR: CRISTINA MARIA
WIEDEMANN
TÍTULO: "GEOLOGIA, PETROGRAFIA E GEOQUÍMICA DE ROCHAS GRANITÓIDES
DA REGIÃO DE PEDRA AZUL - MG"
ABSTRACT: The granitic rocks from Pedra Azul
region can be subdivided in two groups. The first one is derived from migmatitic
rocks and is characterized by garnet as accessory mineral. These rocks are
included in the Complexo Jequitinhonha. The second group has two porphyritic
facies and one homogeneous and is intrusive in the Complexo Jequitinhonha. These
rocks contain xenoliths of saccharoid granites and dark microgranular-hornblend
bearing enclaves. These rocks constitute the Complexo de Medina. The granites of
Complexo de Medina have signatures of I-type, are late to post-orogenic with
calc-alkaline character, dominantly metaluminous, plotting in the STRECKEISEN
diagram in the granitic and granodioritic fields. The elliptical form, the
presence of xenocrysts and the intern foliation parallel to the bord of
microgranular enclaves permit to interpret their genesis by commingling. The
distribution patterns of REE of granites and enclaves are similar and compatible
with a crustal origin. Allanite and titanite are responsible by REE pattern,
being more concentrated in less diferenciated rocks. Field features,
petrographic and geochemical data indicate that the k-feldspars megacrysts were
formed together with the ones of the groundmass. All the evidences pointed to a
crustal origin for granites and enclaves, being the magma mixing and magmatic
diferenciation responsible by their evolution.
NOME: SORAYA ALMEIDA
ORIENTADOR: MARIA DO CARMO BUSTAMANTE
JUNHO
TÍTULO: "PETROGRAFIA E GEOQUÍMICA DE ROCHAS ULTRAMÁFICAS NA REGIÃO DE
LIBERDADE E CARRANCAS, MINAS GERAIS"
ABSTRACT: Six bodies of ultramafic
rocks, four exposed next to Liberdade (Fazenda da Roseta, Serra da Garça, Morro
do Corisco and Arantina) and two next to Carrancas (Serra do Moleque and Fazenda
da Areia), are object of this study. In Liberdade, the bodies are surrounded by
metasediments of Proterozoic age and, in Carrancas, they are situated at contact
zones between Proterozoic metasediments and Archean basement. In both regions,
the ultramafic bodies are considered allochtonous and show, at their edges,
schistosity in concordance with regional structures. In those rocks,
mineralogical compositions vary significantly. In Liberdade they are
predominantly websterites, honblendites, spinel harzburgites and spinel
orthopiroxenites in the Fazenda da Roseta body; serpentinites, spinel
hornblendites and dunites in the Morro do Corisco; orthopiroxenites and rocks
rich in anthophylllitic amphiboles in the Serra da Garça region and chlorites
olivine fels in Arantina. In Carrancas, hornblendites, serpentinites, talc
schists and talc fels are associated in the Serra do Moleque ultramafic body;
spinel orthopiroxenites, serpentinites and rocks made up predominantly of
chlorite are observed in the Fazenda da Areia body. Mineral parageneses in those
rocks indicate metamorphism under amphibolite facies conditions. In some
specimens, however, it is still possible to recognize mineralogical relations
that indicate equilibration under granulite facies conditions. Eighteen samples,
eleven from Liberdade and seven from Carrancas were chosen for chemical
analyses. Geochemical characteristics suggest that the ultramafic bodies of
Liberdade are genetically related. However, one of them, the Arantina body,
showed distinct compositional behavior, similar, on the other hand, to the
chemical compositions of Carrancas rocks. Genetic relations between ultramafic
rocks of both regions are, however, uncertain. Mineralogical compositions and
geochemical and textural data suggest that the ultramafic bodies were derived
from differentiated tholeiitic magmas rather than tectonic slices of upper
mantle or Alpine-type bodies.
NOME: SÍLVIA REGINA DE MEDEIROS
ORIENTADOR: CRISTINA MARIA
WIEDEMANN
TÍTULO: "GEOLOGIA, PETROLOGIA E GEOQUÍMICA DO MACIÇO INTRUSIVO DE
VÁRZEA ALEGRE - ES"
ABSTRACT: The intrusive complex of Várzea Alegre is
located at the central-northern portion of Espírito Santo State. Based on
geological mapping (1:50.000), two domains were recognized: an external domain
of a wide ring of charnockitic rocks and an internal domain of contrasting
magnetites. The contact between the two domain is clear, although sometimes
gradual (lit-par-lit, amagmatic, or nebulitic). The intrusive body, studied in
detail, could be subdivided into four sub-domains, consisting of the following
lithotypes: gabronorite, quartz-diorite, quartz-monzodiorite and monzonite rocks
and coarse megaporphyritic granite. A small stock of fine-grained quartz-syenite
crops out, in the central portion of the massif. The different lithotypes of
magmatites are disposed in a nearly circular structure, with a more basic core
and more acidic to intermediate margins, typical for an inversely zoned diapir.
Planar flow structures tend to present almost subvertical dip angles, which are
well observed nex to the contact between the internal and external domains.
Petrographic and geochemical studies suggest a mantle origin for the basic and
intermediate rocks and the existence of two main magmatic process of
differentiation: fractional crystallization and commingling. Acid rocks seem to
be related to crustal melting, induced by the rise of mantle material. Network
structures, mantled porphyritic k-feldspars and embayed quartz surrounded by
mafic minerals are evidence of mechanical mixing process of contrasting magmas.
These features are commonly found in others plutons in the South of Espírito
Santo, like Santa Angélica, Castelo and Venda Nova massifs.
NOME: MARCELO ESTEVES ALMEIDA
ORIENTADOR: MARIA DO CARMO BUSTAMANTE
JUNHO
TÍTULO: "GEOLOGIA, PETROGRAFIA E GEOQUÍMICA PRELIMINAR DO LEUCOGRANITO
CAPIVARA, ITAMONTE, SUL DE MINAS GERAIS"
RESUMO: Os migmatitos e
leucogranitos a leste de Itamonte (MG) foram gerados pelo processo
metamórfico-anatético, que afetou os metassedimentos da base do Ciclo
Deposicional Andrelândia I. A sequência migmatítica representa dois estágios
distintos de fusão parcial, marcados por tipos metatexíticos e diatexíticos. O
biotita gnaisse migmatítico (metatexito) preserva em parte as características
ré-migmatização, enquanto o leucognaisse migmatítico (diatexito heterogêneo),
gerado sob condições de fusão parcial mais avançada, possui estruturas
pré-migmatíticas bastante destruídas. Anfibolitos e muscovita-quartzo xisto
constituem resistatos do processo anatético. O leucogranito Capivara apresenta
três fácies distintas, denominadas de Ribeirão da Prata, Dois Irmãos e Monte
Belo. Este corpo possui contatos intrusivos, concordantes e gradativos com esta
sequência migmatítica, possui composição monzogranítica e demonstra, em planta,
forma lenticular, alongada na direção NE-SW. Apresenta textura equigranular à
levemente porfirítica, e associação mineral essencial composta por quartzo,
microclina (micropertítica), plagioclásio (albita-oligoclásio), muscovita,
biotita, turmalina, granada; e acessória formada de zircão, apatita, monazita e
minerais opacos. A fácies Ribeirão da Prata corresponde a um granito migmatítico
ou diatexito homogêneo, e marca a transição entre o leucogranito Capivara e as
rochas encaixantes migmatíticas. É caracterizada por apresentar aglomerados de
biotita e porções com textura migmatítica preservada. As fácies Dois Irmãos e
Monte Belo correspondem, respectivamente, a muscovita-biotita e
biotita-muscovita leucogranitos, apresentando caráter intrusivo e associações
minerais semelhantes, diferindo entre si, apenas, em alguns aspectos texturais e
químicos. A geração do magma leucogranítico ocorreu no ápice do metamorfismo
sin-Dn (principal fase de deformação), intrudindo posteriormente estruturas
relativas a Dn+1. A sudeste, o leucogranito Capivara é bordejado por biotita
granito porfirítico, denominado granito Maromba, que é caracterizado por
apresentar-se bastante deformado, com caráter porfirítico conspícuo e matriz
enriquecida em biotita. Os diagramas químicos discriminativos apontam para uma
gênese envolvendo fusão crustal, em condições PT similares às observadas em
ambientes de colisão continental ou de subducção do tipo-A. A origem do
leucogranito Capivara e das rochas encaixantes migmatíticas, baseada na fusão
parcial de material crustal, encontra embasamento nas relações de campo e
petrográficas. Constata-se uma gradação contínua, que segue uma sequência
baseada no aumento crescente proporcional de fusão: biotita gnaisse migmatítico
(metatexito) ® leucognaisse migmatítico (diatexito heterogêneo) ® Fácies
Ribeirão da Prata (granito migmatítico ou diatexito homogêneo) ® Fácies Dois
Irmãos (muscovita-biotita leucogranito) ® Fácies Monte Belo (biotita-muscovita
leucogranito).
NOME: CARLOS SIQUEIRA BANDEIRA DE MELLO
ORIENTADOR: HÉLIO MONTEIRO PENHA
TÍTULO: "A CONTRIBUIÇÃO DA GEOLOGIA E DA GEOQUÍMICA NA AVALIAÇÃO AMBIENTAL E
NO PROGNÓSTICO DA QUALIDADE DA ÁGUA DE ABASTECIMENTO DO RIO MACAÉ, RJ"
RESUMO: Este estudo teve como objetivo enfatizar a importância das ferramentas
geológicas e geoquímicas na avaliação do quadro e dos impactos ambientais decorrentes
de processos naturais e /ou antropogênicas no rio Macaé, RJ, em especial no
baixo curso do rio, onde concentra-se a maior parte das atividades de agricultura,
pecuária bem como as estações de tratamento da água de abastecimento do município
de Macaé, RJ. Para isso, realizou-se um reconhecimento geológico em 1.750 km2
correspondentes a bacia de drenagem do rio Macaé e tributários, ao longo dos
110 km de percurso desse rio. Efetuou-se, ainda um levantamento geoquímico numa
área de 230 km2 , do baixo curso do rio Macaé, onde foram coletadas amostras
de solos, rochas e águas. Baseados na geologia e nas análises dessas amostras,
e mediante um estudo estatístico - com enfoque em backgrounds, correlações de
elementos e substâncias; análise de agrupamentos e componentes principais, foi
possível obter-se tanto as assinaturas geoquímicas da área estudada como também
mostrar-se a importância de levantamentos desse tipo na discriminação dos impactos
ambientais em sistemas naturais e/ou de origem antrópica. A análise comparativa
entre os teores geoquímicos de rochas e solos indicaram a tendência dos elementos
Fe, Al, Sn, Pb e V em fixarem-se nos solos. Ao que parece a incorporação desses
elementos às águas do rio Macaé deve estar ocorrendo através das partículas
de solos carreadas pelo runoff. Por outro lado, a mesma análise comparativa,
indicou que os elementos Mn, Ba, Co, Cr, Cu, Ni, Sr, Zn, As, Si e Ca mostraram-se
mais propensos à lixiviação. Por intermédio do estudo geoquímico foi possível,
também, detectar-se os locais em que as condições naturais das águas estão sendo
modificadas antropicamente - a exemplo do aumento do teor de nitrogênio provavelmente
ligado a decomposição de alimentos e dejetos de trutas, na parte montanhosa
do alto rio Macaé. De outro lado, ressaltou-se que os backgrounds litológicos
naturalmente elevados das rochas, devem ser separados daqueles a origem antrópica,
à exemplo do alumínio - encontrado nas águas do rio Macaé com valores coincidentes
ao máximo tolerável pela legislação , devido à sua abundância em rochas oriundas
de pelitos aluminosos na Unidade São Fidélis. Tais discriminações seriam difíceis
de serem avaliadas, apenas com as análises químicas rotineiramente determinadas
em amostras de águas de rios, sem um conhecimento prévio de geoquímica das unidades
geológicas da região. No caso específico das análises de solos, os elementos
Sr e Ba serviram ainda para caracterizar a Unidade Região dos Lagos devido à
correlação perfeita existente entre eles. Dentre os principais impactos encontrados
na região, ligados aos aspectos geológicos, reconheceu-se, avaliou-se e sugeriu-se
ações mitigadoras para a melhoria da qualidade das águas do rio Macaé em: regiões
sujeitas a movimentos rápidos de massa, devido a abertura de estradas e plantio
de bandeiras em zonas de encostas íngremes; áreas de canais retificados do baixo
rio Macaé, seus efeitos no regime de deposição dos sedimentos e as prováveis
conseqüências para a biota; contaminação das águas devido ao runoff - na maioria
das vezes incrementado pela descentralização geológica e vegetal nas margens
do rio Macaé, bem como as bolsas que dragam areia no fundo do rio Macaé.