Academic literature on the topic 'Data??o Rb-Sr e Sm-Nd de minera??o de ouro'

AbstractMineral and whole-rock isotope data for a massive charnockite from Kottaram in the Nagercoil Block at the southern tip of Peninsular India yield Sm—Nd and Rb—Sr ages of 517 ± 26 Ma and 484 ± 15 Ma respectively. The Nd model age calculated for the charnockite is c. 2100 Ma. Our study reports the first Pan-African mineral isochron ages from regional charnockites of Peninsular India, which are in good agreement with the recently obtained ages of incipient charnockites in the adjacent blocks, as well as alkaline plutons within the same block. Our results indicate that the Pan-African tectonothermal event in the granulite blocks south of the Palghat—Cauvery shear zone was regional, with terrain-wide rejuvenation. These results correlate with similar Pan-African tectono-thermal events reported from Sri Lanka and East Antarctica, and have an important bearing on Gondwana reconstructions.

Abstract Perovskite (Prv) was discovered in an abyssal harzburgite from a “mélange” type blueschist-bearing accretionary wedge of the Western Carpathians (Meliata Unit, Slovakia). Perovskite-1 formation in serpentinized orthopyroxene may be simplified by the mass-balance reaction: Ca2Si2O6 (Ca-pyroxene-member)+2Fe2TiO4 (ulvöspinel molecule in spinel)+2H2O+O2=2CaTiO3 (Prv)+2SiO2+4FeOOH (goethite). Perovskite-2 occurs in a chlorite-rich blackwall zone separating serpentinite and rodingite veins, and in rodingite veins alone. The bulk-rock trace-element patterns suggest negligible differences from visually and microscopically less (“core”) to strongly serpentinized harzburgite due to serpentinization and rodingitization: an enrichment in LREE(La,Ce), Cs, ±Ba, U, Nb, Pb, As, Sb, ±Nd and Li in comparison with HREE, Rb and Sr. The U/Pb perovskite ages at ~135 Ma are interpreted to record the interaction of metamorphic fluids with harzburgite blocks in the Neotethyan Meliatic accretionary wedge. Our LA-ICP-MS mineral study provides a complex view on trace element behaviour during the two stages of rodingitization connected with Prv genesis. The positive anomalies of Cs, U, Ta, Pb, As, Sb, Pr and Nd in Cpx, Opx and Ol are combined with the negative anomalies of Rb, Ba, Th, Nb and Sr in these minerals. The similar positive anomalies of Cs, U, Ta, ±Be, As, Sb found in typical serpentinization and rodingitization minerals, with variable contents of La, Ce and Nd, and negative anomalies of Rb, Ba, Th, Nb and Sr suggest involvement of crustal fluids during MP-LP/LT accretionary wedge metamorphism. LA-ICP-MS study revealed strong depletion in LREE from Prv-1 to Prv-2, and a typically negative Eu (and Ti) anomaly for Prv-1, while a positive Eu (and Ti) anomaly for Prv-2. Our multi-element diagram depicts enrichment in U, Nb, La, Ce, As, Sb, Pr, Nd and decreased Rb, Ba, Th, Ta, Pb, Sr, Zr in both Prv generations. In general, both Prv generations are very close to the end-member composition. In spite of low concentrations of isomorphic constituents, Prv-1 and Prv-2 display the A(La,Ce)3++B(Fe,Cr)3+=ACa2++BTi4+ heterovalent couple substitution. A decrease of ferric iron in Prv-2 indicates increasing reduction conditions during rodingitization.

Granites are assumed to be the main source of heavy rare-earth elements (HREEs), which have important applications in modern society. However, the geochemical and petrographic characteristics of such granites need to be further constrained, especially as most granitic HREE deposits have undergone heavy weathering. The LC batholith comprises both fresh granite and ion-adsorption-type HREE deposits, and contains four main iRee (ion-adsorption-type REE) deposits: the Quannei (QN), Shangyun (SY), Mengwang (MW), and Menghai (MH) deposits, which provide an opportunity to elucidate these characteristics The four deposits exhibit light REE (LREE) enrichment, and the QN deposit is also enriched in HREEs. The QN and MH deposits were chosen for study of their petrology, mineralogy, geochemistry, and geochronology to improve our understanding of the formation of iRee deposits. The host rock of the QN and MH deposits is granite that includes REE accessory minerals, with monazite, xenotime, and allanite occurring as euhedral inclusions in feldspar and biotite, and thorite, fluorite(–Y), and REE fluorcarbonate occurring as anhedral filling in cavities in quartz and feldspar. Zircon U–Pb dating analysis of the QN (217.8 ± 1.7 Ma, MSWD = 1.06; and 220.3 ± 1.2 Ma, MSWD = 0.71) and MH (232.2 ± 1.7 Ma, MSWD = 0.58) granites indicates they formed in Late Triassic, with this being the upper limit of the REE-mineral formation age. The host rock of the QN and MH iRee deposits is similar to most LC granites, with high A/CNK ratios (>1.1) and strongly peraluminous characteristics similar to S-type granites. The LC granites (including the QN and MH granites) have strongly fractionated REE patterns (LREE/HREE = 1.89–11.97), negative Eu anomalies (Eu/Eu* = 0.06–0.25), and are depleted in Nb, Zr, Hf, P, Ba, and Sr. They have high 87Sr/86Sr ratios (0.710194–0.751763) and low 143Nd/144Nd ratios (0.511709–0.511975), with initial Sr and Nd isotopic compositions of (87Sr/86Sr)i = 0.72057–0.72129 and εNd(220 Ma) = −9.57 to −9.75. Their initial Pb isotopic ratios are: 206Pb/204Pb = 18.988–19.711; 208Pb/204Pb = 39.713–40.216; and 207Pb/204Pb = 15.799–15.863. The Sr–Nd–Pb isotopic data and TDM2 ages suggest that the LC granitic magma had a predominantly crustal source. The REE minerals are important features of these deposits, with feldspars and micas altering to clay minerals containing Ree3+ (exchangeable REE), whose concentration is influenced by the intensity of weathering; the stronger the chemical weathering, the more REE minerals are dissolved. Secondary mineralization is also a decisive factor for Ree3+ enrichment. Stable geology within a narrow altitudinal range of 300–600 m enhances Ree3+ retention.

Abstract The petrogenesis of calc-alkaline magmatism in the Eocene Absaroka Volcanic Province (AVP) is investigated at Washburn volcano, a major eruptive center in the low-K western belt of the AVP. New 40Ar/39Ar age determinations indicate that magmatism at the volcano commenced as early as 55 Ma and continued until at least 52 Ma. Although mineral and whole-rock compositional data reflect near equilibrium crystallization of modal phenocrysts, petrogenetic modeling demonstrates that intermediate composition magmas are hybrids formed by mixing variably fractionated and contaminated mantle-derived melts and heterogeneous silicic crustal melts. Nd and Sr isotopic compositions along with trace element data indicate that silicic melts in the Washburn system are derived from deep-crustal rocks broadly similar in composition to granulite-facies xenoliths in the Wyoming Province. Our preferred explanation for these features is that mantle-derived basaltic magma intruded repeatedly in the deep continental crust leading to fractional crystallization, silicic melt production, and homogenization of magmas, followed by ascent to shallow reservoirs and crystallization of new plagioclase-rich mineral assemblages in equilibrium with the intermediate hybrid liquids. The implications of this process are that (1) some calc-alkaline magmas may only be recognized as hybrids on purely chemical grounds, particularly in systems where mixing precedes and is widely separated from crystallization in space and time, and (2) given the role ascribed to crustal processes at Washburn volcano, the variation between rocks that follow calc-alkaline trends in the western AVP and those that follow shoshonitic trends in the east cannot simply reflect higher pressures of fractionation to the east in Moho-level magma chambers in the absence of crustal interaction.

AbstractCarbonatites are enriched in critical raw materials such as the rare-earth elements (REE), niobium, fluorspar and phosphate. A better understanding of their fluid regimes will improve our knowledge of how to target and exploit economic deposits. This study shows that multiple fluid phases penetrated the surrounding fenite aureole during carbonatite emplacement at Chilwa Island, Malawi. The first alkaline fluids formed the main fenite assemblage and later microscopic vein networks contain the minerals of potential economic interest such as pyrochlore in high-grade fenite and rare-earth minerals throughout the aureole. Seventeen samples of fenite rock from the metasomatic aureole around the Chilwa Island carbonatite complex were chosen for study. In addition to the main fenite assemblage of feldspar and aegirine ± arfvedsonite, riebeckite and richterite, the fenite contains micro-mineral assemblages including apatite, ilmenite, rutile, magnetite, zircon, rare-earth minerals and pyrochlore in vein networks. Petrography using a scanning electron microscope in energy-dispersive spectroscopy mode showed that the rare-earth minerals (monazite, bastnäsite and parisite) formed later than the fenite feldspar, aegirine and apatite and provide evidence ofREEmobility into all grades of fenite. Fenite apatite has a distinct negative Eu anomaly (determined by laser ablation inductively coupled plasma mass spectrometry) that is rare in carbonatite-associated rocks and interpreted as related to pre-crystallization of plagioclase and co-crystallization with K-feldspar in the fenite. The fenite minerals have consistently higher midREE/lightREEratios (La/Sm ≈ 1.3 monazite, ≈ 1.9 bastnäsite, ≈ 1.2 parisite) than their counterparts in the carbonatites (La/Sm ≈ 2.5 monazite, ≈ 4.2 bastnäsite, ≈ 3.4 parisite). Quartz in the low- and medium-grade fenite hosts fluid inclusions, typically a few micrometres in diameter, secondary and extremely heterogeneous. Single phase, 2- and 3-phase, single solid and multi solid-bearing examples are present, with 2-phase the most abundant. Calcite, nahcolite, burbankite and baryte were found in the inclusions. Decrepitation of inclusions occurred at ∼200°C before homogenization but melting-temperature data indicate that the inclusions contain relatively pure CO2. A minimum salinity of ∼24 wt.% NaCl equivalent was determined. Among the trace elements in whole-rock analyses, enrichment in Ba, Mo, Nb, Pb, Sr, Th and Y and depletion in Co, Hf and V are common to carbonatite and fenite but enrichment in carbonatitic type elements (Ba, Nb, Sr, Th, YandREE) generally increases towards the inner parts of the aureole. A schematic model contains multiple fluid events, related to first and second boiling of the magma, accompanying intrusion of the carbonatites at Chilwa Island, each contributing to the mineralogy and chemistry of the fenite. The presence of distinct rare-earth mineral microassemblages in fenite at some distance from carbonatite could be developed as an exploration indicator ofREEenrichment.

Abstract. We report here the elemental composition of sinking particles in sediment traps and in the water column following four artificial dust seeding experiments (each representing a flux of 10 g m−2). Dry or wet dust deposition were simulated during two large mesocosms field campaigns that took place in the coastal water of Corsica (NW Mediterranean Sea) representative of oligotrophic conditions. The dust additions were carried out with fresh or artificially aged dust (i.e., enriched in nitrate and sulfate by mimicking cloud processing) for various biogeochemical conditions, enabling us to test the effect of these parameters on the chemical composition and settling of dust after deposition. The rates and mechanisms of total mass, particulate organic carbon (POC) and chemical elements (Al, Ba, Ca, Co, Cu, Fe, K, Li, Mg, Mn, Mo, N, Nd, P, S, Sr and Ti) transfer from the mesocosm surface to the sediment traps installed at the base of the mesocosms after dust deposition show that (1) 15% of the initial dust mass was dissolved in the water column in the first 24 h after seeding. Except for Ca, S and N, the elemental composition of dust particles was constant during their settling, showing the relevance of using interelemental ratios, such as Ti/Al as proxy of lithogenic fluxes. (2) Whatever the type of seeding (using fresh dust to simulate dry deposition or artificially aged dust to simulate wet deposition), the particulate phase both in the water column and in the sediment traps was dominated by dust particles. (3) Due to the high Ba content in dust, Ba/Al cannot be used as productivity proxy in the case of high dust input in the sediment traps. Instead, our data suggests that the ratio Co/Al could be a good productivity proxy in this case. (4) After 7 days, between 30 and 68% of added dust was still in suspension in the mesocosms. This difference in the dust settling was directly associated with a difference in POC export, since POC fluxes were highly correlated to dust lithogenic fluxes signifying a ballast effect of dust. The highest fraction of remaining dust in suspension in the mesocosm at the end of the experiment was found inversely correlated to Chl a increase. This suggests that the fertilizing effect of dust on autotrophs organisms, the ballast effect, and POC fluxes are strongly correlated. (5) Our data emphasize a typical mass ratio Lithogenic/POC fluxes around 30 which could be used as reference to estimate the POC export triggered by wet dust deposition event.

Abstract. We report here the elemental composition of sinking particles in sediment traps and in the water column following 4 artificial mineral dust seedings (representing a flux of 10 g m−2) in mesocosms, simulating dry or wet dust deposition into oligotrophic marine waters. These data were used to examine the rates and mechanisms of total mass, particulate organic carbon (POC) and elemental (Al, Ba, Ca, Co, Cu, Fe, K, Li, Mg, Mn, Mo, N, Nd, P, S, Sr and Ti) transfer from the surface to the sediment traps after dust deposition. The dust additions were carried out with fresh or artificially aged dust (i.e. enriched in nitrate and sulfate by mimicking cloud processing) for various biogeochemical conditions, enabling us to test the effect of these parameters on the chemical evolution and settling of dust after deposition. Whatever the type of seeding (using fresh dust to simulate dry deposition or artificially aged dust to simulate wet deposition), the dust was predominant in the particulate phase in the sediment traps at the bottom of mesocosms and within the water column during each experiment. 15% of initial dust mass was dissolved in the water column in the first 24 h after seeding. For artificially aged dust, this released fraction was mainly nitrate, sulfate and calcium and hence represented a significant source of new N for the marine biota. Except for Ca, S and N, the elemental composition of dust particles was constant during their settling, showing the relevance of using interelemental ratios, such as Ti/Al or Ba/Al as proxy of lithogenic fluxes or of productivity. After 7 days, between 30 and 68% of added dust was still in suspension in the mesocosms depending on the experiment. This difference in the dust settling was directly associated to a difference in POC export, since POC fluxes were highly correlated to dust lithogenic fluxes signifying a ballast effect of dust. The highest fraction of remaining dust in the mesocosm at the end of the experiment was found when the lowest chl a increase was observed, and inversely. This suggests a high interaction between a fertilizing effect of dust, a ballast effect, and POC fluxes. Our data emphasize a typical ratio Lithogenic/POC fluxes around 30 which could be used as reference to estimate the POC export triggered by wet dust deposition event. The elemental fluxes associated to the dust settling presented in this paper constitute also an original database on the export of atmospheric metals in a case of dry or wet dust deposition event.

Abstract The cratonic lithosphere–asthenosphere boundary is commonly invoked as the site of sheared peridotite and megacryst formation, a well-recognized petrologic assemblage whose genetic relationships – if any – remain poorly understood. We have undertaken a comprehensive petrology and Sr-Nd-Hf-Ca isotope study of sheared peridotite xenoliths and clinopyroxene megacrysts from the ca. 1150 Ma Premier kimberlite pipe on the central Kaapvaal craton in South Africa. New textural and mineral trace element evidence suggests that strong tectonic and magmatic overprinting affected the lower cratonic mantle over a vertical distance of ≥ 50 km from the lithosphere–asthenosphere boundary located at ∼200-225 km depth. Although modification of the central Kaapvaal cratonic mantle is commonly linked to the ca. 2056 Ma Bushveld large igneous event, our thermobarometry, mantle redox, and Sr-Nd-Hf-Ca isotope data support a model in which volatile-rich low-volume melts and associated high-density fluids refertilized the lithosphere base shortly before or during asthenosphere-derived kimberlite and carbonatite magmatism at around 1150 Ma. This episode of lithospheric mantle enrichment was facilitated by exceptionally strong shear movements, as are recorded in the plastically deformed peridotites. We argue that stress-driven segregation of percolating carbonated melts contributed to megacryst formation along, or in close proximity to, shear zones within the cratonic mantle lithosphere.

Abstract Accretionary orogens are characterized by voluminous juvenile components (recently derived from the mantle) and knowing the origin(s) of such components is vital for understanding crustal generation. Here we present field and petrological observations, along with mineral chemistry, zircon U–Pb age and Hf–O isotope data, and whole rock geochemical and Sr–Nd isotopic data for the c.320 Ma Ulungur intrusive complex from the Central Asian Orogenic Belt. The complex consists of two different magmatic series: one is characterized by medium- to high-K calc-alkaline gabbro to monzogranite; the other is defined by peralkaline aegirine–arfvedsonite granitoids. The calc-alkaline and peralkaline series granitoids have similar depleted mantle-like Sr–Nd–Hf isotopic compositions, but they have different zircon δ18O values: the calc-alkaline series have mantle-like δ18O values with mean compositions ranging from 5·2 ± 0·5‰ to 6·0 ± 0·9‰ (2SD), and the peralkaline granitoids have low δ18O values ranging from 3·3 ± 0·5‰ to 3·9 ± 0·4‰ (2SD). The calc-alkaline series were derived from a hydrous sub-arc mantle wedge, based on the isotope and geochemical compositions, under garnet peridotite facies conditions. This study suggests that the magmas underwent substantial differentiation, ranging from high pressure crystallization of ultramafic cumulates in the lower crust to lower pressure crystallization dominated by amphibole, plagioclase and minor biotite in the upper crust. The peralkaline series rocks are characterized by δ18O values lower than the mantle and enrichment of high field strength elements (HFSEs) and heavy rare earth elements (HREEs). They likely originated from melting of preexisting hydrothermally altered residual oceanic crust in the lower crust of the Junggar intra-oceanic arc. Early crystallization of clinopyroxene and amphibole was inhibited owing to their low melting temperature, leading to HFSEs and HREEs enrichment in residual peralkaline melts during crystallization of a feldspar-dominated mineral assemblage. Thus, the calc-alkaline and peralkaline series represent episodes of crust generation and reworking, respectively, demonstrating that the juvenile isotopic signature in accretionary orogens can be derived from diverse source rocks. Our results show that reworking of residual oceanic crust also plays an important role in continental crust formation for accretionary orogens, which has not previously been widely recognized.

AbstractThe Early to Late Cretaceous Mundwara alkaline complex (comprising the Musala, Mer and Toa plugs) displays a broad spectrum of alkaline rocks closely associated in space and time with the Deccan large igneous province in NW India. Petrology and Nd–Sr isotopic data on the two youngest and altogether compositionally different lamprophyre dykes of the Mundwara alkaline complex are presented in this paper to understand their petrogenesis and also to constrain the magmatic processes responsible for generation of the rock spectrum in the complex (pyroxenite, picrite ankaramite, carbonatite, shonkinite, olivine gabbro, feldspathoidal and foid-free syenite). The two lamprophyre dykes occurring in the Mer and the Musala hills are referred to as basaltic camptonite I and camptonite II, respectively. The basaltic camptonite I is highly porphyritic and contains olivine, clinopyroxene and magnetite macrocrysts embedded within the groundmass of microphenocyrsts composed of clinopyroxene, phlogopite, magnetite and feldspar. Camptonite II, however, with a more or less similar texture, contains amphibole, biotite, magnetite and clinopyroxene within the microphenocrystic groundmass of amphibole, biotite, apatite and feldspar. Pyroxenes are chemically zoned and display corrosion of the cores, revealing that they are antecrysts developed during the early stages of magma evolution and later on inherited by more evolved magmas. The mineral chemistry and trace element composition of the lamprophyres reveal that fractional crystallization was a dominant process. Early segregation of olivine + Cr-rich clinopyroxene + Cr-spinel from a primary hydrous alkali basalt within a magmatic plumbing system is inferred, which led to the generation of basaltic camptonitic magma (M1) forming the Mer hill lamprophyre. Subsequently, progressive fractionation of pyroxene and Fe–Ti oxides from the basaltic camptonitic (M1) magma generated camptonitic (M2) magma forming the Musala hill lamprophyre. Both lamprophyre dykes on the Sr–Nd isotopic array reflect plume-type asthenospheric derivation, which largely corresponds to the Réunion plume and other alkaline rocks of the Deccan large igneous province. Our study brings out a complex sequence of processes such as crystal fractionation, accumulation and corrosion in the magmatic plumbing system involved in the generation of the Mundwara alkaline complex.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Great part of the gold mineralizations are associated with shearing zones through which circulate a great volume of fluids, that interact with the host rocks, originating leaching or precipitation of chemical elements, including gold. The studied mineralizations are inserted in the Serid? Belt. The tungsten mineralization in Breju? Mine is hosted in calcsilicate rocks from Jucurutu Formation. The S?o Francisco auriferous mineralization has as host rocks mica-schists from Serid? Formation, while the Ponta da Serra and Fazenda Simp?tico mineralizations are hosted in orthogneisses of this fold belt basement. The research conducted on these mineralizations had the purpose of integrate the data of chemical elements behavior during the shearing/mineralizing event, and its influence on the isotopic systems Rb-Sr and Sm-Nd. The studies of chemical mobility in the auriferous mineralizations showed that elements that during the shearing displayed in general an immobile behavior were Al, Ti and Zr. Among the elements that were mobilized during the event, K and Rb showed mass gain in ali belts of transformed rocks, while the elements Ca, Na and Sr normally lost mass. Petrographic studies showed that the minerais biotite and plagioclase, in all investigated mineralizations, played an important role in the chemical reactions occurred in the transformed rocks to the generation of muscovite, cordierite and sillimanite, justifying the input of K to the formation of muscovite, and the release of Na and Ca from plagioclase to the fluid phase. In the S?o Francisco auriferous mineralization, the results of the Rb-Sr isotopic analysis yielded ages of 645 ? 19 Ma and 596 ? 17 Ma, with both samples, from original and transformed rocks. Two ages, 569 ? 20 Ma. and 554 ? 19 Ma., were obtained with samples frem the transformed rocks domain. These ages suggest that there were two metamorphic pulses during the emplacement of the mineralized shearing zone. The Sm-Nd data yielded TDM ages of 1,31 Ga and 1,26 Ga with 3Nd (0,6 Ga) of -0,26 e -0,40 for the original and final transformed rocks, respectively. In case of the orthogneisses of Caic? Complex, e.g. the Ponta da Serra and Fazenda Simp?tico mineralizations, the Rb-Sr data did not yield ages with geological significance. In the Ponta da Serra mineralization, the Sm-Nd isotopic data yielded T DM ages of 2,56 Ga and 2,63 Ga to the original rocks and of 2,71 Ga to the mineralized sheared rock, and values of 3Nd (2,0 Ga) between -3,70 e -5,42 to the original and sheared rock, respectively. In the Fazenda Simp?tico, Sm-Nd data yielded TDM between 2,65 and 2,69 Ga with values of 3Nd (2,0 Ga) between -5,25 e -5,52. Considering the Sm-Nd data, the TDM ages may be admitted as the age of the parental magma extraction, producer of the protoliths of the orthogneisses from Ponta da Serra and Fazenda Simp?tico mineralizations. The chemical mobility studies showed that in the basement hosted mineralizations, Rb achieved mass while Sr lost mass, as Sm as well as Nd were strongly mobilized. The Sm/Nd ratio remained constant, however, confirming the isochemical character of those elements. In the basement mineralizations, Rb-Sr ages are destituted of geological significance, because of the partial opening of the isotopic system during the tectono-metamorphic transformations. In the tungsten mineralization, the diagram Sm-Nd constructed with the whole-rock data of calcsilicatic and the high-temperature paragenesis (garnet, diopside and iron-pargasitic hornblende) indicated an 631 ? 24 Ma age, while with the whole-rock data and low-temperature paragenesis (vesuvianite, epidote and calcite), a 537 ? 107 Ma age was obtained. These ages, associated with the petrographic observations, suggest that there was a time gap among the hydrothernal events responsible by the formation of the high and low temperature paragenesis in the calcsilicatic rocks mineralized in scheelite
As mineraliza??es estudadas est?o inseridas na Faixa de dobramento Serid?. A scheelit?fera de Breju? est? hospedada em rochas calciossilic?ticas da Forma??o Jucurutu. A mineraliza??o aur?fera de S?o Francisco tem como hospedeiros micaxistos da Forma??o Serid?, enquanto que as mineraliza??es de Ponta da Serra e da Fazenda Simp?tico est?o hospedadas em ortognaisses do embasamento desta faixa de dobramentos. Grande parte das mineraliza??es de ouro est?o associadas ? zonas de cisalhamento que funcionam como conduto para a circula??o de um grande volume de fluidos, que interagem com as rochas hospedeiras provocando lixivia??o ou precipita??o de elementos qu?micos, incluindo o ouro. Estas foram algumas das principais caracter?sticas observadas nas mineraliza??es aqui estudadas. A pesquisa realizada nas mineraliza??es de ouro teve a finalidade de integrar os dados do comportamento de elementos qu?micos durante o evento cisalhamento/mineralizante, e sua influ?ncia nos sistemas isot?picos Rb-Sr e Sm-Nd. Os estudos de mobilidade qu?mica mostraram que os elementos, que durante o cisalhamento, de uma forma geral apresentaram um coportamento im?vel, foram o AI, Ti e Zr. Dentre os elementos que foram mobilizados durante o evento, o K e o Rb mostraram ganho de massa em todas as faixas de rochas transformadas, enquanto que os elementos Ca, Na e o Sr normalmente perderam massa. Os elementos Sm e Nd na mineraliza??o de S?o Francisco se comportaram como im?veis e em Ponta da Serra e Fazenda Simp?tico perderam massa. Os estudos petrogr?ficos mostraram que os minerais biotita e plagiocl?sio, em todas as mineraliza??es estudadas, tiveram papel importante nas rea??es qu?mica ocorridas nas rochas transformadas para a gera??o de muscovita, cordierita e silimanita, justificando a entrada do K para forma??o da muscovita e da libera??o de Na e Ca do plagiocl?sio para a fase fluida. Na mineraliza??o aur?fera de S?o Francisco, os resultados das an?lises isot?picas de Rb e Sr, forneceram idades de 645 ? 19 Ma e de 596 ? 17 Ma com amostras das rochas originais e transformadas juntas. Duas idades, 569 ? 20 Ma e 554 ? 19 Ma foram obtidas com as amostras do dom?nio das rochas transformadas. Estas idades s?o sugestivas de que houve dois pulsos metam?rficos durante a instala??o da zona de cisalhamento mineralizada. Os dados Sm-Nd forneceram idades TDM de 1,31 Ga e de 1,26 Ga com 3Nd (0,6 Ga) de -0,26 e -0,40 respectivamente para a rocha original e transformada final. Para os ortognaisses do Complexo Caic?, caso da mineraliza??o de Ponta da Serra e da Fazenda Simp?tico, os dados Rb-Sr n?o forneceram idades com significado geol?gico. Na mineraliza??o de Ponta da Serra, os dados isot?picos Sm-Nd forneceram idades T DM de 2,56 Ga e 2,63 Ga para as rochas originais e de 2,71 Ga para a rocha cisalhada, mineral?zada e valores de 3Nd (2,0 Ga) entre -3,70 e -5,42 para rocha original e cisalhada respectivamente. Na Fazenda Simp?tico os dados de Sm-Nd forneceram as idades T DM ficaram entre 2,65 e 2,69 Ga com valores de 3Nd (2,0 Ga) entre -5,25 e -5,52. Quanto aos dados Sm-Nd as idades T DM podem ser admitidas como a idade de extra??o do magma parental formador dos prot?l?tos dos ortognaisses das mineraliza??es Ponta da Serra e da Fazenda Simp?tico. Os valores de 3Nd baixos e negativos sugerem uma fonte crustal, ou a participa??o de duas fontes (mantocrosta) . Os estudos de mobilidade qu?mica mostraram que nas mineraliza??es hospedadas no embasamento, o Rb ganhou massa enquanto o Sr perdeu massa e tanto o Sm quanto o Nd, foram fortemente mobilizados. As raz?es Sm/Nd entretanto se mantiveram constantes, confirmando o car?ter isoqu?mico destes elementos. Nas mineraliza??es do embasamento, idades pelo m?todo Rb-Sr s?o desprovidas de significado geol?gico, em fun??o da abertura parcial do sistema isot?pico durante as transforma??es tectonometam?rficas. Na mineraliza??o scheelit?fera foi realizado um estudo geocronol?gico Sm-Nd com o intuito de se obter as idades das parag?neses formadas durante os eventos hidrotermais sofridos pelas rochas calciossilic?ticas mineralizadas. O diagrama Sm-Nd constru?do com os dados de rocha total e parag?nese de alta temperatura (granada, diops?dio e hornblenda ferropargas?tica) forneceu uma idade de 631 ? 24 Ma, e com os dados de rocha total e parag?nese de baixa temperatura (vesuvianita, epidoto e calcita), foi obtida uma idade de 537 ? 107 Ma. Estas idades associadas com as observa??es petrogr?ficas sugerem que houve um lapso de tempo entre os eventos hidrotermais respons?veis pelas forma??es das parag?neses de alta e de baixa temperatura nas rochas calciossilic?ticas mineralizadas em scheelita