The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U–Pb zircon geochronology

Jackson, Simon E.; Pearson, Norman J.; Griffin, William L.; Белоусова, Е. А.

doi:10.1016/j.chemgeo.2004.06.017

Cited by 4,499 publications

(1,848 citation statements)

References 22 publications

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“…A ablação foi realizada em spots 30 μm, frequência de 10 Hz e intensidade de 2 mJ/cm 2 . Os dados foram adquiridos em 40 ciclos de 1 s, sendo utilizado padrão GJ-1 (Jackson et al 2004) para correções de fracionamento de massa. A redução dos dados foi realizada em planilha Microsoft ® Excel (cf.…”

Section: Materiais E Métodosunclassified

Geocronologia U-Pb em zircão de rochas intrusivas e de embasamento na região do Vale do Jacurici, Cráton do São Francisco, Bahia

et al. 2015

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RESUMO: O Complexo Jacurici, NE do Cráton do São Francisco, é constituído de vários corpos máficos-ultramáficos N-S mineralizados aCr, possivelmente fragmentos de um único sill rompido durante deformação. Alguns trabalhos sugerem que está intruso no Bloco Serrinha, enquanto outros o inserem no Cinturão Salvador-Curaçá. O embasamento nessa região é dividido informalmente em paragnaisses e ortognaisses, o último supostamente mais jovem, considerando-se estar menos deformado. Petrografia revelou que alguns dos paragnaisses são álcali-feldspato granitos fortemente milonitizados. Os ortognaisses ocorrem no norte e consistem, ao menos em parte, de monzogranitos com deformação heterogênea, localmente de baixa temperatura. Datações U-Pb em zircão foram realizadas para cinco amostras representativas. Apenas três resultaram em boas idades concórdias. Uma rocha máfica produziu idade de 2102 ± 5 Ma e é petrograficamente similar aos metanoritos do Complexo Jacurici, sendo interpretada como registro dos primeiros pulsos do magmatismo máfico. Um monzogranito gerou idade de 2995 ± 15 Ma, sendo mais antigo do que o esperado, relacionado ao Bloco Serrinha. Álcali-feldspato granito produziu idade de 2081 ± 3 Ma. O Sienito Itiúba e os pegmatitos que cortam o Complexo Jacurici têm idades semelhantes. Considerando a falta de informações sobre a sequência supracrustal que hospeda as rochas alcalinas e máficas-ultramáficas intrusivas nas áreas de Ipueira e Medrado, é possível que parte do terreno pertença ao Cinturão Salvador-Curaçá. Sugerimos que o Complexo Jacurici possa ter sido intrudido após a colagem tectônica entre o Bloco Serrinha e a parte mais antiga do Cinturão Salvador-Curaçá e, portanto, poderia ser hospedado por ambos. et al. (2004a; 2004b) entendem que as rochas máficas-ultramáficas estão inseridas nas sequências arqueanas de médio grau do Bloco Serrinha. Mapeamento na escala 1:100.000 está sendo desenvolvido pela Companhia de Pesquisa de Recursos Minerais (CPRM) e mapeamentos em escala de maior detalhe têm sido realizados de forma sistemática pela Companhia de Ferro Ligas da Bahia (FERBASA), empresa que explora o distrito cromití-fero do Vale do Jacurici e que busca entender as relações entre as rochas mineralizadas e o embasamento. No entanto, na região específica das intrusões máficas-ultramáficas, poucos dados geocronológicos estão disponíveis. Assim, este estudo buscou agregar novos dados geocronológicos U-Pb em zircão por LA-MC-ICP-MS de rochas adjacentes aos corpos mineralizados na região do Vale do Jacurici de modo a contribuir para o entendimento do posicionamento temporal dessas mineralizações e prover novos dados que apoiem as interpretações do contexto geológico regional. PALAVRAS-CHAVE: CONTEXTO GEOLÓGICO REGIONALO Cráton do São Francisco (Fig. 1) A configuração atual do embasamento do Cráton do São Francisco é interpretada como produto da colisão paleoproterozoica de antigos blocos arqueanos (Gavião, Serrinha, Jequié e Itabuna-Salvador-Curaçá) que foram amalgamados em aproximadamente 2,0 Ga para formar ...

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Section: Materiais E Métodosunclassified

Geocronologia U-Pb em zircão de rochas intrusivas e de embasamento na região do Vale do Jacurici, Cráton do São Francisco, Bahia

et al. 2015

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“…The session was conducted in a Neptune Thermo Scientific LA-MC-ICP-MS (25 μm spot size). The zircon GJ-1 (Jackson et al 2004) was used as standard, analysed twice every 6 sample grain analyses. Analytical spots were conducted avoiding grain areas with inclusions, fractures and metamictic structures.…”

Section: Methodsmentioning

confidence: 99%

Stratigraphy, tectonics and detrital zircon U-Pb (LA-ICP-MS) geochronology of the Rio Preto Belt and northern Paramirim corridor, NE, Brazil

et al. 2017

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Two important Proterozoic metasedimentary sequences, the Rio Preto and Santo Onofre Groups, crop out along the northwestern margin of the São Francisco craton and in northern Paramirim corridor, respectively. The Rio Preto Group, involved in the eponymous fold-thrust belt along the northwestern cratonic boundary, comprises the Formosa (garnet schist, quartz-mica schist, quartzite, chlorite-sericite schist and ferriferous quartz schist) and Canabravinha (quartzite, micaceous quartzite, metarhytmite, phylite, schist and metaturbidite) formations. The Santo Onofre Group occurs exclusively in the Paramirim corridor, and is composed of quartzite and minor carbonaceous or Mn-rich phylite. These units record sedimentation in shallow to deep-water marine settings related to rift basins, and were deformed and metamorphosed under greenschist facies conditions during the Brasiliano orogeny. Here we present 427 new detrital zircon U-Pb ages, which constrain the maximum depositional ages of ca. 971 Ma for the Santo Onofre Group, ca. 912 Ma for the Canabravinha Formation, and ca. 965 Ma for the Formosa Formation of the Rio Preto Group. Our data suggests that the Santo Onofre and the Rio Preto Groups accumulated in two distinct basin settings. The latter, composed mostly of sandy rocks, would represent a relatively stable, shallow-marine shelf environment. The Rio Preto Group, with metadiamictite, quartzite, pelitic and rhythmitic rocks, represents a shallow to deep marine environment influenced by gravity flows. Both groups were probably deposited in the Late Tonian, and are potential correlatives of the lower (pre-glacial) units of the Macaú-bas Group of the Araçuaí belt. KEYWORDS:Detrital zircon U-Pb geochronology, Brasiliano orogeny, sedimentary provenance, Rio Preto Belt, Paramirim corridor. RESUMO: Duas importantes sequências metassedimentares proterozoicas ocorrem ao longo da margem noroeste do Cráton do

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“…The concentrations of U and Th during each analysis were determined by comparing background-corrected count rates with the mean count rates on the GJ standard, which has well-known average U and Th concentrations of 230 and 15 ppm, respectively. A weighted mean 207 Pb/ 206 Pb age of 610 ± 11 Ma (2σ) for the GJ standard was obtained during this study, corresponding to a highly precise 207 Pb/ 206 Pb age of 608.5 ± 0.4 Ma obtained by Thermal Ionization Mass Spectrometer (TIMS) analysis (Jackson et al, 2004).…”

Section: Sample Preparation and Analytical Procedures 41 Sampling Anmentioning

confidence: 99%

“…Zircons were imaged using reflected and transmitted light microscopy and cathodoluminescence (CL) using a scanning electron microscope to characterize internal structures and to choose potential target sites for U-Pb dating. U-Pb isotope analysis was undertaken using an Agilent 7500a Inductively Coupled Plasma Mass Spectrometer (ICP-MS) equipped with a New Wave Research 213 nm laser ablation (LA) system at the State Key Laboratory of Mineral Deposit Research, Nanjing University, China, following the procedures described by Jackson et al (2004) and He et al (2009). Analyses employed a beam diameter of 18-25 μm, a repetition rate of 5 Hz, and a laser energy of 10-20 J/cm 2 .…”

Section: Sample Preparation and Analytical Procedures 41 Sampling Anmentioning

confidence: 99%

Two Periods of Skarn Mineralization in theBaizhangyanW–MoDeposit, SouthernAnhui Province, SoutheastChina: Evidence from ZirconU–Pband MolybdeniteRe–Osand Sulfur Isotope Data

Jiang

Xing

et al. 2015

Resource Geology

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The recently discovered Baizhangyan skarn-porphyry type W-Mo deposit in southern Anhui Province in SE China occurs near the Middle-Lower Yangtze Valley polymetallic metallogenic belt. The deposit is closely temporally-spatially associated with the Mesozoic Qingyang granitic complex composed of granodiorite, monzonitic granite, and alkaline granite. Orebodies of the deposit occur as horizons, veins, and lenses within the limestones of Sinian Lantian Formation contacting with buried fine-grained granite, and diorite dykes. There are two types of W mineralization: major skarn W-Mo mineralization and minor granite-hosted disseminated Mo mineralization. Among skarn mineralization, mineral assemblages and cross-cutting relationships within both skarn ores and intrusions reveal two distinct periods of mineralization, i.e. the first W-Au period related to the intrusion of diorite dykes, and the subsequent W-Mo period related to the intrusion of the fine-grained granite. In this paper, we report new zircon U-Pb and molybdenite Re-Os ages with the aim of constraining the relationships among the monzonitic granite, fine-grained granite, diorite dykes, and W mineralization. Zircons of the monzonitic granite, the fine-grained granite, and diorite dykes yield weighted mean U-Pb ages of 129.0 ± 1.2 Ma, 135.34 ± 0.92 Ma and 145.3 ± 1.7 Ma, respectively. Ten molybdenite Re-Os age determinations yield an isochron age of 136.9 ± 4.5 Ma and a weighted mean age of 135.0 ± 1.2 Ma. The molybdenites have δ 34 S values of 3.6‰-6.6‰ and their Re contents ranging from 7.23 ppm to 15.23 ppm. A second group of two molybdenite samples yield ages of 143.8 ± 2.1 and 146.3 ± 2.0 Ma, containing Re concentrations of 50.5-50.9 ppm, and with δ 34 S values of 1.6‰-4.8‰. The molybdenites from these two distinct groups of samples contain moderate concentrations of Re (7.23-50.48 ppm), suggesting that metals within the deposit have a mixed crust-mantle provenance. Field observation and new age and isotope data obtained in this study indicate that the first diorite dyke-related skarn W-Au mineralization took place in the Early Cretaceous peaking at 143.0-146.3 Ma, and was associated with a mixed crust-mantle system. The second fine-grained granite-related skarn W-Mo mineralization took place a little later at 135.0-136.9 Ma, and was crust-dominated. The fine-grained granite was not formed by fractionation of the Qingyang monzonitic Resource Geology Vol. 65,

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The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U–Pb zircon geochronology

Cited by 4,499 publications

References 22 publications

Geocronologia U-Pb em zircão de rochas intrusivas e de embasamento na região do Vale do Jacurici, Cráton do São Francisco, Bahia

Geocronologia U-Pb em zircão de rochas intrusivas e de embasamento na região do Vale do Jacurici, Cráton do São Francisco, Bahia

Stratigraphy, tectonics and detrital zircon U-Pb (LA-ICP-MS) geochronology of the Rio Preto Belt and northern Paramirim corridor, NE, Brazil

Two Periods of Skarn Mineralization in theBaizhangyanW–MoDeposit, SouthernAnhui Province, SoutheastChina: Evidence from ZirconU–Pband MolybdeniteRe–Osand Sulfur Isotope Data

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