<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Trace element signatures in rutile: characterization of standards and applications to accessory mineral behavior in metamorphic rocks"^^ . "This study focuses on the trace element composition of rutile, a frequent accessory mineral in various rock types (mafic, pelitic and felsic protoliths; common at blueschist-, eclogite- and granulite-facies conditions) and one of the most stable minerals in sedimentary environments. Rutile is an important carrier of highly charged elements, such as Ti, V, Cr, Zr, Nb, Sn, Sb, Hf, Ta and W. Due to these characteristics rutile has attracted significant interest in various fields of geology, e.g., as a likely controller of Nb and Ta budgets in subduction zones. Furthermore, it is useful as a geothermometer (Zr incorporation is strongly temperature dependent in quartz- and zircon-bearing systems), and as a geochronological tool (U-Pb and (U-Th)/He dating), and to assess the nature of an initial source rock in sediment provenance studies (Nb and Cr contents can de used to distinguish between mafic and felsic sources). An increasing number of today’s geochemical studies, which include the investigations presented here, are based on microanalysis of trace elements, several of which are carried out in-situ. All of these techniques depend on calibration using a homogeneous material with well documented chemical concentration. In this sense, having a rutile standard is a key issue. A set of rutile crystals were investigated in order to find rutiles suitable for use as mineral standards. Trace element concentrations of 15 elements (V, Cr, Fe, Zr, Nb, Mo, Sn, Sb, Hf, Ta, W, Lu, Pb, Th and U) as well as Pb and Hf isotope data are presented for four large (centimeter size) and relatively homogeneous rutile grains. Analytical techniques used are SIMS, EMP, LA–ICP–MS, ID–MC–ICP–MS and TIMS. For most elements, homogeneity is usually within ±10% and variations are occasionally less than (±5%), particularly in the core of two of the studied grains. The trace element concentrations of the grains span a broad compositional range (e.g., Zr concentrations are ca. 4, 100, 300 and 800 ppm). Provisional concentration values, calculated based on the homogeneity of the element and agreement between techniques, are presented for Zr, Nb, Sn, Sb, Hf, Ta, W and U. One of the studied grains has a relatively high U concentration (ca. 30 ppm) and rather constant U–Pb ages (1085.1 to 1096.2 Ma, 207Pb/235U ages and 1086.3 to 1096.6 Ma, 206Pb/238U ages), favoring its application as an age standard for U-Pb rutile dating. The studied rutiles are useful as mineral standards in for in-situ rutile measurements, particularly for Zr–in–rutile thermometry, quantitative provenance studies (Nb and Cr concentrations as an index of source rock type) and U–Pb dating. The efforts in characterizing a set of rutile standards are not only relevant for the scientific community. It also provides the analytical background for the results presented here. Following the characterization of standards, textural observations and in-situ analyses were used to investigate trace element behavior during prograde and retrograde metamorphic reactions involving rutiles. The investigated samples derive from two well studied localities: the Ivrea-Verbano Zone (Italy) and the Erzgebirge (Germany). The Ivrea-Verbano Zone is a classic granulite area and rocks from the Strona and d’Ossola Valleys are an example of the amphibolite to granulite facies transition, where rutile growth is associated with the breakdown of high-Ti biotite. Rutile bearing rocks show a rich inventory of textures that allow for the investigation of trace element behavior in response to prograde rutile growth, and the effect of postpeak processes on rutile chemistry. Nb concentrations in rutile from lower grade samples show a larger spread (from 500 to 5000 ppm within one sample) when compared to those from higher grades. This pattern can be modeled using prograde rutile growth formed from biotite breakdown. Zr concentrations in rutile are characterized by an anomalously large spread and a bimodal distribution. Maximum Zr concentrations increase according to the general metamorphic gradient known for this area. Temperatures (from Zr-in-rutile thermometry), although feasible, are considerably higher than previous calculations (increasing from ca. 850 to 930°). A second cluster of Zr concentrations in rutile occurs at rather constant concentrations (ca. 1000 ppm) for all localities and is interpreted to be related to intense fluid influx at high temperature and/or to post-peak diffusional resetting favored by slow cooling rates. Alteration textures, characterized by a complex network of microveins, are evidence for the late fluid influx. The fluid strongly affected the rutiles, which is evidenced by corrosion of older rutile grains and the formation of rutile veinlets. In the Ezgebirge, metamorphic texture support prograde rutile growth from ilmenite in low- to medium-grade (430-630C° metasedimentary rocks. Newly crystallized rutiles occur as polycrystalline aggregates that mimic the shape of the ilmenites. In-situ trace element data show that rutiles from the lowest grade samples (ca 480C° mirror the Nb/Ti ratio of ilmenite. Under these conditions, rutile did not equilibrate its chemistry with the remaining ilmenites. In higher grade samples, rutiles show a larger scatter in Nb and have Nb/Ti ratios higher than relict ilmenite. In these rocks, the Nb pattern can be modeled using prograde rutile growth from ilmenite, in a model similar to the one applied to granulites from the the Ivrea- Verbano Zone. Results indicate that rutiles from these rocks were able to reequilibrate its chemistry with the remaining ilmenites. Newly formed rutiles yield temperatures (from 500 to 630C° that are in agreement with the metamorphic conditions published for the studied rocks. Detrital rutile grains, identified by their distinct chemical composition (high Zr and Nb contents) and textures (single grains surrounded by fine grained ilmenites), occur in quartzites from the medium-grade rocks (ca 530C°. This confirms models in which detrital rutiles survive in quartzites to higher metamorphic grade compared to rutiles in metapelites. Preliminary calculations based on the grain size distribution of rutiles in the studied rocks show that quartzites are probably the main source of rutiles in sediments derived from low-grade metamorphic sequences, even if the occurrence of quartzite is minor. Part of the data obtained during the development of this thesis contributed to other publications related, directly or indirectly, to its topic. For example, to evaluate how well the Zr-in-rutile thermometer can be applied to eclogites; to evaluate the applicability of rutile trace element geochemistry to provenance studies; and to characterize the occurrence and stability of coesite-bearing tourmaline in ultra-high pressure metamorphic rocks."^^ . "2008" . . . . . . . . "George Luiz"^^ . "Luvizotto"^^ . "George Luiz Luvizotto"^^ . . . . . . "Trace element signatures in rutile: characterization of standards and applications to accessory mineral behavior in metamorphic rocks (PDF)"^^ . . . "PhD_thesis_Luvizotto_GL20081212.pdf"^^ . . . "Trace element signatures in rutile: characterization of standards and applications to accessory mineral behavior in metamorphic rocks (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Trace element signatures in rutile: characterization of standards and applications to accessory mineral behavior in metamorphic rocks (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . 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