scholarly journals Textures and Chemical Compositions of Magnetite from Iron Oxide Copper-Gold (IOCG) and Kiruna-Type Iron Oxide-Apatite (IOA) Deposits and Their Implications for Ore Genesis and Magnetite Classification Schemes

2019 ◽  
Vol 114 (5) ◽  
pp. 953-979 ◽  
Author(s):  
Xiao-Wen Huang ◽  
Georges Beaudoin
Keyword(s):  
High Temperature ◽  
Iron Oxide ◽  
Trace Element ◽  
Oxygen Fugacity ◽  
Oscillatory Zoning ◽  
Chemical Compositions ◽  
Fluid Composition ◽  
Copper Gold

Abstract Textural and compositional data of magnetite from Igarapé Bahia, Alemao, Sossego, Salobo, and Candelaria iron oxide copper-gold (IOCG) and El Romeral Kiruna-type iron oxide-apatite (IOA) deposits show that some magnetite grains display oscillatory zoning or have been reequilibrated by oxy-exsolution, coupled dissolution and reprecipitation (CDR) reactions, and/or recrystallization. Textures formed via CDR are most widespread in the studied samples. The original oscillatory zoning was likely derived from the crystal growth during fluctuating fluid compositions rather than from variation in temperature and oxygen fugacity. The oxy-exsolution of ilmenite in magnetite is attributed to increasing oxygen fugacity and decreasing temperature with alteration and mineralization, resulting in product magnetite with lower Ti and higher V contents. Recrystallization of some magnetite grains is commonly due to high-temperature annealing that retained primary compositions. Two different types of CDR processes are defined according to textures and chemical compositions of different generations of magnetite. The first generation of magnetite (Mag-1) is an inclusion-rich and trace element-rich core, which was replaced by an inclusion-poor and trace element-poor rim (Mag-2). The third generation of magnetite (Mag-3), inclusion poor but trace element rich, occurs as veins replacing Mag-2 along fractures or grain margins. Type 1 CDR process transforming Mag-1 to Mag-2 is more extensive and is similar to processes reported in skarn deposits, whereas type 2 CDR process is local, transforming Mag-2 to Mag-3. During type 1 CDR process, minor and trace elements Si, K, Ca, Mg, Al, and Mn in magnetite are excluded, and Fe contents increase to various extents, in contrast to type 2 CDR process, which is characterized by increased contents of Si, K, Ca, Mg, Al, and Mn. Type 1 CDR process is possibly induced by the changing fluid composition and/or decreasing temperature during progressive alteration and ore formation, whereas type 2 CDR process can be interpreted as post-ore replacement due to a new pulse of magmatic-hydrothermal fluids. The identification of magnetite core (Mag-1) with igneous origin and rim (Mag-2) with magmatic-hydrothermal origin in the Sossego IOCG and El Romeral IOA deposits supports a fluid changing from magmatic to magmatic-hydrothermal during IOCG and IOA formation and indicates a genetic link between these two deposit types. The large data set here further demonstrates that magnetite is susceptible to textural and compositional reequilibration during high-temperature magmatic and magmatic-hydrothermal processes. Reequilibrated magnetite, particularly that formed by CDR processes, has a chemical composition that can be different from that of primary magnetite. Modified magnetite, therefore, cannot be used to discriminate its primary origin or to interpret its provenance in overburden sediments. Therefore, in situ chemical analysis of magnetite combined with textural characterization is necessary to understand the origin of magnetite in IOCG and IOA deposits.

scholarly journals Columbite-Tantalite Group Mineral U-Pb Geochronology of Chaqiabeishan Li-Rich Granitic Pegmatites in the Quanji Massif, NW China: Implications for the Genesis and Emplacement Ages of Pegmatites

2021 ◽  
Vol 8 ◽  
Author(s):  
Tong Pan ◽  
Qing-Feng Ding ◽  
Xuan Zhou ◽  
Shan-Ping Li ◽  
Jie Han ◽  
...  
Keyword(s):  
Trace Element ◽  
Statistical Significance ◽  
Oscillatory Zoning ◽  
Evolutionary Trend ◽  
Granitic Pegmatites ◽  
Icp Ms ◽  
Trace Element Contents ◽  
Element Contents

The Chaqiabeishan area is characterized by small Li-rich granitic pegmatites in the Quanji Massif (QM), northwest China. In this study, the columbite-tantalite group minerals (CGMs) from a typical Li-rich pegmatite dike were analyzed for major element contents using an EMPA (electron microprobe analyzer), for trace element contents using LA-ICP-MS (laser ablation-inductively coupled plasma mass spectrometry), and for ages using LA-ICP-MS U-Pb dating, respectively. The CGMs from the sample can be divided into two types, i.e., magmatic Type 1 and metasomatic Type 2. Although these two types of CGMs do not exhibit distinct major and trace element variations from core to rim within an individual grain, the Ta# values, Mn# values, and some trace element contents (such as Zr, Hf, W, and Sr) of Type 1 CGMs are distinct from those of Type 2 CGMs. The overall compositional changes from Type 1 CGMs to Type 2 CGMs are consistent with the typical evolutionary trend described for many lithium-cesium-tantalum (LCT) pegmatites and the complex spodumene trend described by Černý and Ercit (Bull. Mineral., 1989, 108, 499–532). The Type 2 CGMs have formed later and must be a metasomatic product of Type 1 CGMs. Eighteen Type 1 CGMs yielded a weighted mean 206Pb/238U age of 240.6 ± 1.5 Ma. The slight oscillatory zoning and/or sector zoning suggest that the dated Type 1 columbites have a magmatic origin. Thus, the crystallization ages of Type 1 columbites represent the emplacement ages of Li-rich pegmatites. One of the Type 2 CGMs yielded a 206Pb/238U age of 211.0 ± 4.7 Ma, which is hardly interpreted to be an age representing the later hydrothermal metasomatism, because one dataset has no apparent statistical significance. Therefore, our dating results can only indicate that the Li-rich pegmatite-forming melts were emplaced at approximately 240.6 Ma. Based on these results and previous studies of the 240–254 Ma granitoids in the QM, we conclude that the 240.6 Ma Li-rich granitic pegmatites, as well as 240–254 Ma granitoids in the QM, were both emplaced during the southward subduction of the Zongwulong Ocean Plate in the Late Permian to Middle Triassic.

Cathodoluminescence (CL) behaviour and crystal chemistry of apatite from rare-metal deposits

2002 ◽  
Vol 66 (1) ◽  
pp. 151-172 ◽  
Author(s):  
U. Kempe ◽  
J. Götze
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Crystal Chemistry ◽  
Rare Earth Element ◽  
Earth Element ◽  
Rare Metal ◽  
Oscillatory Zoning ◽  
Luminescence Spectroscopy

AbstractApatite samples from rare-metal mineralization were investigated by a combination of cathodoluminescence (CL) microscopy and spectroscopy, microchemical analysis and trace element analysis. Internal structures revealed by CL can be related to variations in the crystal chemistry and may sometimes reflect changes in the composition of the mineralizing fluids.Apatite from mineralization related to alkaline rocks and carbonatites (Type 1) typically exhibits relatively homogeneous blue and lilac/violet CL colours due to activation by trace quantities of rare earth element ions (Ce3+, Eu2+, Sm3+, Dy3+ and Nd3+). These results correlate with determined trace element abundances, which show strong light rare earth element (LREE) enrichment for this type of apatite. However, a simple quantitative correlation between emission intensities of REE3+/2+ and analysed element concentrations was not found.Apatite from P-rich altered granites, greisens, pegmatites and veins from Sn-W deposits (Type 2) shows strong Mn2+-activated yellow-greenish CL, partially with distinct oscillatory zoning. Variations in the intensity of the Mn2+-activated CL emission can be related either to varying Mn/Fe ratios (quenching of Mn activated CL by Fe) or to self-quenching effects in zones with high Mn contents (>2.0 wt.%). The REE distribution patterns of apatite reflect the specific geological position of each sample and may serve as a “tracer” for the REE behaviour within the ore system. Although the REE contents are sometimes as high as several hundred parts per million, the spectral CL measurements do not exhibit typical REE emission lines because of dominance of the Mn emission. In these samples, REE-activated luminescence is only detectable by time-resolved laser-induced luminescence spectroscopy.Both types of apatite (Type 1 in the core and Type 2 in the rim) were found in single crystals from the Be deposit Ermakovka (Transbaikalia). This finding proves the existence of two stages of mineralization within this deposit.

Research on Effect of Alloy Elements on Equilibrium and Properties of Ni-Cr-Co Type Nickel-Based Superalloy

2016 ◽  
Vol 849 ◽  
pp. 513-519
Author(s):  
Qing Quan Zhang ◽  
Ming Yang Li ◽  
Ran Wei ◽  
Hui Yun Wu ◽  
Zhen Rui Li
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
High Temperature Strength ◽  
Nickel Based Superalloy ◽  
Type 3 ◽  
Room Temperature Strength ◽  
Super Alloy ◽  
Type Nickel

Ni-Cr-Co type Nickel-based super alloy Inconel 740H was studied. The effect of Nb, Al and Ti on the equilibrium of this alloy was analyzed by JMatPro software. The amount of Ti and Nb should be controlled by 1.50wt.%, and meanwhile, Al should be 1.0-2.0wt.%. If Mo and W were added the amount of Mo should be in the range of 1.0-2.0wt. %, and W should be about 1.0wt.%. Based on these results, three types of new alloys were designed, which contain Ni-Cr-Co-Mo type (1#), Ni-Cr-Co-W type (2#) and Ni-Cr-Co-Mo-W type (3#). Compared with the Ni-Cr-Co type Inconel 740H alloy, the room temperature strength, high temperature strength and high temperature durable performance of the three new alloys improved, which can provide the evidence and reference to optimize the chemical composition of Inconel 740H alloy, i.e., adding 1.50wt.% Mo and 1.0wt.% W individually or together.

CF/SCC Interaction on Structural Materials for LWR in High Temperature Water

2002 ◽  
Author(s):  
Yasuyuki Katada ◽  
Shigeo Ohashi
Keyword(s):  
High Temperature ◽  
Water Type ◽  
Loading Test ◽  
High Temperature Water ◽  
Rate Test ◽  
Loading Modes ◽  
Type 3 ◽  
Temperature Water

A test apparatus was developed to study the interaction between corrosion fatigue (CF) and stress corrosion cracking (SCC) in high-temperature water simulated boiling water reactor environment. Tests were conducted using 1/2T-CT samples of both low alloy and sensitized stainless steels under 3 different types of loading at 0.2–8 ppm in dissolved oxygen concentrations at 563 K in water. Type 1 was a normal cyclic loading test of constant amplitude, Type 2 a monotonic constant loading rate test, and Type 3 a combination of Type 1 + Type 2 loading modes. In the low alloy steel, no striking interaction was observed between CF and SCC, whereas in the case of Type 3 loading condition crack growth rates of the sensitized stainless steel were as much as 3 times higher than those for Type 1 + Type 2. The mechanism of the CF and SCC interaction is discussed.

Isotopic analyses of clinopyroxene in mantle xenoliths demonstrate the effects of kimberlite melt metasomatism upon the lithospheric mantle

2020 ◽  
Author(s):  
Angus Fitzpayne ◽  
Andrea Giuliani ◽  
Janet Hergt ◽  
Jon Woodhead ◽  
Roland Maas
Keyword(s):  
Trace Element ◽  
Lithospheric Mantle ◽  
Mantle Metasomatism ◽  
Mantle Xenoliths ◽  
Isotopic Compositions ◽  
Isotopic Analyses ◽  
Cretaceous Magmatism

<p>As clinopyroxene is the main host of most lithophile elements in the lithospheric mantle, the trace element and radiogenic isotope systematics of this mineral have frequently been used to characterise mantle metasomatic processes. To further our understanding of mantle metasomatism, both solution-mode Sr-Nd-Hf-Pb and in situ trace element and Sr isotopic data have been acquired for clinopyroxene grains from a suite of peridotite (lherzolites and wehrlites), MARID (Mica-Amphibole-Rutile-Ilmenite-Diopside), and PIC (Phlogopite-Ilmenite-Clinopyroxene) rocks from the Kimberley kimberlites (South Africa). The studied mantle samples can be divided into two groups on the basis of their clinopyroxene trace element compositions, and this subdivision is reinforced by their isotopic ratios. Type 1 clinopyroxene, which comprises PIC, wehrlite, and some sheared lherzolite samples, is characterised by low Sr (~100–200 ppm) and LREE concentrations, moderate HFSE contents (e.g., ~40–75 ppm Zr; La/Zr < 0.04), and restricted isotopic compositions (e.g., <sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> = 0.70369–0.70383; εNd<sub>i</sub> = +3.1 to +3.6) resembling those of their host kimberlite magmas. Available trace element partition coefficients can be used to show that Type 1 clinopyroxenes are close to equilibrium with kimberlite melt compositions, supporting a genetic link between kimberlites and these metasomatised lithologies. Thermobarometric estimates for Type 1 samples indicate equilibration depths of 135–155 km within the lithosphere, thus showing that kimberlite melt metasomatism is prevalent in the deeper part of the lithosphere beneath Kimberley. In contrast, Type 2 clinopyroxenes occur in MARID rocks and coarse granular lherzolites, which derive from shallower depths (<130 km), and have higher Sr (~350–1000 ppm) and LREE contents, corresponding to higher La/Zr of >~0.05. The isotopic compositions of Type 2 clinopyroxenes are more variable and extend from compositions resembling the “enriched mantle” towards those of Type 1 rocks (e.g., εNd<sub>i</sub> = -12.7 to -4.4). To constrain the source of these variations, in situ Sr isotope analyses of clinopyroxene were undertaken, including zoned grains in Type 2 samples. MARID and lherzolite clinopyroxene cores display generally radiogenic but variable <sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> values (0.70526–0.71177), which might be explained by the interaction between peridotite and melts from different enriched sources with the lithospheric mantle. In contrast, the rims of these Type 2 clinopyroxenes trend towards compositions similar to those of the host kimberlite and Type 1 clinopyroxene from PIC and wehrlites. These results are interpreted to represent clinopyroxene overgrowth during late-stage (shortly before/during entrainment) metasomatism by kimberlite magmas. Our study shows that an early, pervasive, alkaline metasomatic event caused MARID and lherzolite genesis in the lithospheric mantle beneath the Kimberley area, which was followed by kimberlite metasomatism during Cretaceous magmatism. This latter event is the time at which discrete PIC, wehrlite, and sheared lherzolite lithologies were formed, and MARID and granular lherzolites were partly modified.</p>

Two new rare-earth-rich mineral associations in the Ilímaussaq alkaline complex, South Greenland

2001 ◽  
pp. 143-144
Author(s):  
Igor V. Pekov ◽  
Irina A. Ekimenkova
Keyword(s):  
Rare Earth ◽  
Chemical Compositions ◽  
Alkaline Complex ◽  
Complex Type ◽  
Unit Cell Parameters ◽  
Widespread Occurrence ◽  
Cell Parameters ◽  
Mineral Associations

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Pekov, I. V., & Ekimenkova, I. A. (2001). Two new rare-earth-rich mineral associations in the Ilímaussaq alkaline complex, South Greenland. Geology of Greenland Survey Bulletin, 190, 143-144. https://doi.org/10.34194/ggub.v190.5185 _______________ Two new types of REE-rich mineral associations have been discovered at Kvanefjeld in the northern part of the Ilímaussaq alkaline complex. Type 1 consists of ussingite veins intersecting lujavrite and containing 5–7% nacareniobsite-(Ce) and 2–4% steenstrupine-(Ce); the adjacent altered lujavrite contains up to 10–12% nacareniobsite-(Ce). Type 2 consists of cavernous sodalite-rich veinlets and vugs in lujavrite containing 5–8% vitusite-(Ce). The chemical compositions and unit cell parameters of REE minerals are given. Nacareniobsite-(Ce) and vitusite-(Ce) were considered to be extremely rare minerals in the Ilímaussaq complex. Nacareniobsite-(Ce) is now known to be of more widespread occurrence in some hyper-agpaitic rocks of the Ilímaussaq complex, and vitusite-(Ce) is known to be the precursor of the widespread occurrence of the yellow pseudomorphs termed erikite.

TRACE ELEMENT SIGNATURE OF PYRITE FROM THE LOS COLORADOS IRON OXIDE-APATITE (IOA) DEPOSIT, CHILE: A MISSING LINK BETWEEN ANDEAN IOA AND IRON OXIDE COPPER-GOLD SYSTEMS?

2016 ◽  
Vol 111 (3) ◽  
pp. 743-761 ◽  
Author(s):  
Martin Reich ◽  
Adam C. Simon ◽  
Artur Deditius ◽  
Fernando Barra ◽  
Stephen Chryssoulis ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Trace Element ◽  
Missing Link ◽  
Copper Gold ◽  
Trace Element Signature

scholarly journals Silician Magnetite from the Copiapó Nordeste Prospect of Northern Chile and Its Implication for Ore-Forming Conditions of Iron Oxide–Copper–Gold Deposits

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 529 ◽  
Author(s):  
Elías González ◽  
Shoji Kojima ◽  
Yoshihiko Ichii ◽  
Takayuki Tanaka ◽  
Yoshikazu Fujimoto ◽  
...  
Keyword(s):  
High Temperature ◽  
Iron Oxide ◽  
Gold Deposits ◽  
Northern Chile ◽  
Exchange Reactions ◽  
Iocg Deposits ◽  
X Ray ◽  
Copper Gold ◽  
High Concentrations ◽  
Substantial Factor

Silica-bearing magnetite was recognized in the Copiapó Nordeste prospect as the first documented occurrence in Chilean iron oxide–copper–gold (IOCG) deposits. The SiO2-rich magnetite termed silician magnetite occurs in early calcic to potassic alteration zones as orderly oscillatory layers in polyhedral magnetite and as isolated discrete grains, displaying perceptible optical differences in color and reflectance compared to normal magnetite. Micro-X-ray fluorescence and electron microprobe analyses reveal that silician magnetite has a significant SiO2 content with small amounts of other “impure” components, such as Al2O3, CaO, MgO, TiO2, and MnO. The oscillatory-zoned magnetite is generally enriched in SiO2 (up to 7.5 wt %) compared to the discrete grains. The formation of silician magnetite is explained by the exchange reactions between 2Fe (III) and Si (IV) + Fe (II), with the subordinate reactions between Fe (III) and Al (III) and between 2Fe (II) and Ca (II) + Mg (II). Silician magnetite with high concentrations of SiO2 (3.8–8.9 wt %) was similarly noted in intrusion-related magmatic–hydrothermal deposits including porphyry- and skarn-type deposits. This characteristic suggests that a hydrothermal system of relatively high-temperature and hypersaline fluids could be a substantial factor in the formation of silician magnetite with high SiO2 contents.

A Continuum from Iron Oxide Copper-Gold to Iron Oxide-Apatite Deposits: Evidence from Fe and O Stable Isotopes and Trace Element Chemistry of Magnetite

2020 ◽  
Vol 115 (7) ◽  
pp. 1443-1459 ◽  
Author(s):  
Maria A. Rodriguez-Mustafa ◽  
Adam C. Simon ◽  
Irene del Real ◽  
John F.H. Thompson ◽  
Laura D. Bilenker ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Stable Isotope ◽  
Trace Element ◽  
Minor Element ◽  
Open Pit ◽  
Temporal Association ◽  
Iocg Deposits ◽  
Copper Gold ◽  
Iocg Deposit ◽  
O Isotope

Abstract Iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of Fe, Cu, and Au. Magnetite is the modally dominant and commodity mineral in IOA deposits, whereas magnetite and hematite are predominant in IOCG deposits, with copper sulfides being the primary commodity minerals. It is generally accepted that IOCG deposits formed by hydrothermal processes, but there is a lack of consensus for the source of the ore fluid(s). There are multiple competing hypotheses for the formation of IOA deposits, with models that range from purely magmatic to purely hydrothermal. In the Chilean iron belt, the spatial and temporal association of IOCG and IOA deposits has led to the hypothesis that IOA and IOCG deposits are genetically connected, where S-Cu-Au–poor magnetite-dominated IOA deposits represent the stratigraphically deeper levels of S-Cu-Au–rich magnetite- and hematite-dominated IOCG deposits. Here we report minor element and Fe and O stable isotope abundances for magnetite and H stable isotope abundances for actinolite from the Candelaria IOCG deposit and Quince IOA prospect in the Chilean iron belt. Backscattered electron imaging reveals textures of igneous and magmatic-hydrothermal affinities and the exsolution of Mn-rich ilmenite from magnetite in Quince and deep levels of Candelaria (>500 m below the bottom of the open pit). Trace element concentrations in magnetite systematically increase with depth in both deposits and decrease from core to rim within magnetite grains in shallow samples from Candelaria. These results are consistent with a cooling trend for magnetite growth from deep to shallow levels in both systems. Iron isotope compositions of magnetite range from δ56Fe values of 0.11 ± 0.07 to 0.16 ± 0.05‰ for Quince and between 0.16 ± 0.03 and 0.42 ± 0.04‰ for Candelaria. Oxygen isotope compositions of magnetite range from δ18O values of 2.65 ± 0.07 to 3.33 ± 0.07‰ for Quince and between 1.16 ± 0.07 and 7.80 ± 0.07‰ for Candelaria. For cogenetic actinolite, δD values range from –41.7 ± 2.10 to –39.0 ± 2.10‰ for Quince and from –93.9 ± 2.10 to –54.0 ± 2.10‰ for Candelaria, and δ18O values range between 5.89 ± 0.23 and 6.02 ± 0.23‰ for Quince and between 7.50 ± 0.23 and 7.69 ± 0.23‰ for Candelaria. The paired Fe and O isotope compositions of magnetite and the H isotope signature of actinolite fingerprint a magmatic source reservoir for ore fluids at Candelaria and Quince. Temperature estimates from O isotope thermometry and Fe# of actinolite (Fe# = [molar Fe]/([molar Fe] + [molar Mg])) are consistent with high-temperature mineralization (600°–860°C). The reintegrated composition of primary Ti-rich magnetite is consistent with igneous magnetite and supports magmatic conditions for the formation of magnetite in the Quince prospect and the deep portion of the Candelaria deposit. The trace element variations and zonation in magnetite from shallower levels of Candelaria are consistent with magnetite growth from a cooling magmatic-hydrothermal fluid. The combined chemical and textural data are consistent with a combined igneous and magmatic-hydrothermal origin for Quince and Candelaria, where the deeper portion of Candelaria corresponds to a transitional phase between the shallower IOCG deposit and a deeper IOA system analogous to the Quince IOA prospect, providing evidence for a continuum between both deposit types.

Isomorphism and mixed crystals in 2-R-naphthalenes: evidence of structural subfamilies and prediction of metastable forms

1999 ◽  
Vol 32 (3) ◽  
pp. 481-488 ◽  
Author(s):  
Y. Haget ◽  
N. B. Chanh ◽  
A. Meresse ◽  
L. Bonpunt ◽  
F. Michaud ◽  
...  
Keyword(s):  
High Temperature ◽  
Unit Cell ◽  
Mixed Crystals ◽  
Unit Cell Parameters ◽  
Two Phase ◽  
Cell Parameters ◽  
Solid Liquid ◽  
Metastable Forms

Solid–liquid binary phase diagrams and isothermal unit-cell parameters as a function of composition are given for the high-temperature form (P21/a,Z= 2) mixed crystals generated by 2-fluoronaphthalene, naphthalene and 2-naphthol with four other β derivatives of naphthalene. The study leads to the distinction between two high-temperature forms (or types of packing). The first one (type 1) is taken by five 2-R-naphthalenes (R= F, Cl, Br, SH, CH3; the first subfamily), the second one (type 2) by naphthalene itself and 2-naphthol (R= H, OH; the second subfamily). The crystallographic data also allow an estimation of unit-cell parameters for the metastable forms of naphthalene (type 1,a= 8.0,b= 5.95,c= 8.6 Å, β = 116°) and 2-fluoronaphthalene (type 2,a= 8.336,b= 5.915,c= 9.000 Å, β = 122.23°), supporting an interpretation, in terms of crossed isodimorphism, of the observed two-phase regions in systems in which the components do not belong to the same subfamily.

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