Use Of Zircon Research Articles

Влияние регуляторов роста растений на усообразовательную способность сортов земляники в условиях южной лесостепной зоны Башкортостана

This work aims at the influence of plant growth regulators on the ability of strawberry varieties to form runners in the conditions of the southern forest-steppe zone of Bashkortostan. The plants were twice sprayed with Albit (0.6 g/l), Krezacin (1 g/l), Zircon (1 g/l), and control water. The use of foliar fertilizers increased the resistance of strawberry plants to unfavorable environmental conditions. The use of Zircon increased the number of strawberry runners by 1.1-1.4 time and the number of daughter rosettes by 1.1-1.5 time. The Asia variety turned out to be highly sensitive to the use of preparations; the proportion of rosettes increased by 27 – 54 % above the control. Under the influence of growth regulators, the Festivalnaya romashka (Festival Chamomile) variety had the largest proportion of plants with runners, up to 83.3 %.

Characterization of Nigerian Zircon Sand and Its Suitability for Different Industrial Applications

This paper describes the potential industrial use of zircon from Nigeria (Plateau, Nasarawa, Kano, Kaduna, Bauchi, and Adamawa states). Different techniques, equipment, and indices such as scanning electron microscope, energy dispersive X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, specific gravity, refractive index, pH, and hardness were used to examine the samples. The X-ray diffraction showed predominantly quartz, zirconium oxide, and other heavy minerals. All twelve samples showed the presence of Zr-O, SiO42−, Zr-OH, and OH, with pH values ranging from 7.3 to 7.8. Six of the zircon samples had a refractive index between 1.4 and 12.5. The hardness values ranged from 0.0021 to 0.0703 GPa, while the elastic moduli were between 0.00558 and 0.9593 GPa. Four of the twelve untreated zircon samples with specific gravities above 4.2 g/cm3, which is the United States Geological Survey minimum recommended standard for zircon sand, needed to be upgraded to increase the ZrO2 weight percentages and purity toward improving their suitability for zircon-reinforced composites applications in aerospace and also for ceramic, foundry, building and construction, and refractory industries. The study’s findings can be incorporated by the industries into their businesses for the development of novel industrial materials as well as the processing methods and procedures for beneficiation of the mineral for value-addition.

The effect of the drug Zircon on the decorative qualities of large-flowered eustoma plants in pot

The article presents the results of the study of the growth stimulator Zircon concentreation influence on the decorative qualities of large-flowered eustoma of White Kyoto F1 and Flamenco pink F1 hybrids. In the experiment, the drug concentration was studied from 0.25 to 5.0%. The drug foliar application affected the height of the plant, the number of leaves and their size, the passage of phenological phases by plants and the duration of flowering. The most effective was the use of Zircon with a solution concentration of 2.5%.

Shock impedance amplified impact deformation of zircon in granitic rocks from the Chicxulub impact crater

Zircon is a precise chronometer and prominent recorder of impact deformation. However, many impact-induced features in zircon are poorly calibrated, sometimes due to contradicting experimental data, in other instances due to the lack of systematic studies of impact-deformed zircon. To resolve issues with the shock petrographic use of zircon, we classified impact deformation features in 429 zircon grains in a continuous drill core of uplifted, granitic bedrock in the peak ring of the 200-km-diameter K-Pg Chicxulub impact structure. Following initial identification in backscattered electron (BSE) images, Raman spectroscopy and electron backscatter diffraction confirmed one reidite-bearing zircon grain. Quartz-based shock barometry indicates the host rock of this zircon-reidite grain experienced an average shock pressure of 17.5 GPa. A survey of BSE images of 429 ZrSiO4 grains found brittle deformation features are ubiquitous, with planar fractures in one to five sets occurring in 23% of all zircon grains. Our survey also reveals a statistically significant correlation of the occurrence of planar fractures in zircon with the types of host materials. Compared to zircon enclosed in mafic, higher density mineral hosts, felsic, low-density minerals show a much higher incidence of zircon with planar fractures. This finding suggests amplification of pressure due to shock impedance contrasts between zircon and its mineral hosts. Using the impedance matching method, we modeled the shock impedance pressure amplification effect for zircon inclusions in Chicxulub granitic hosts. Our modeling indicates shock impedance could have amplified the average 17.5 GPa shock pressure in a zircon inclusion in quartz or feldspar in the Chicxulub granitic rocks to 24 ± 1 GPa, suggesting that reidite in these rocks formed between 17.5 and 25 GPa. In essence, our study of impedance-induced shock pressure amplification in zircon assemblages, including the onset of reidite formation, details how shock impedance in mineral associations can be quantified to refine shock pressure estimates.

Periods of keeping quality and realization of onions depending on the nutrition system

Relevance. The production of onions and its preservation for the year-round provision of the population is an important strategic task. In March-May, there is often a shortage of onions due to high storage losses and incorrect determination of the optimal timing of implementation.Methods. Studies on the effect of fertilizers and plant growth regulators on the preservation of onion hybrids were conducted in 2014-2017 at the ARRIVG-branch of the FSVC. We tested 3 hybrids of onions grown in an annual culture on 6 variants of plant nutrition backgrounds. Harvesting of onions (turnips) was carried out manually, followed by drying in a greenhouse and laying for storage in a vegetable storehouse at a temperature of -1...0°C and a humidity of 80-90%.Results and discussion. The optimal duration of storage of new hybrids and the terms of sale of products when stored in cooling conditions for onions. Data on the shelf life and implementation of onion hybrids, depending on the nutrition background, are presented. Mathematical descriptions of the dependences of the total losses of 3 modern hybrids on the duration of storage and the influence of fertilizers and growth regulators are obtained, which is of great practical importance for the agricultural and industrial complex. Conclusions. A positive effect on the preservation of onions of treatments of vegetative plants with solutions of potassium nitrate (10 kg/ha), Zircon (0.25 l/ha) and Tenso Cocktail (0.7 kg/ha) against the background of N90P90K90 was revealed. The maximum yield of marketable products after 7 months of storage at -1...0℃ and 80-90% humidity in Bennito F1 was on the N90P90K90 + KNO3+ Zircon + Tenso Cocktail variant-89,6%, losses from diseases 2,8%; Poisk 012 F1 on the variant with the use of Zircon against the background of N90P90K90-52,1%, losses from diseases 31,2%; Pervenec F1 on the N90P90K90 + KNO3 variant- 91,4%, losses from diseases 1,4%. Pervenec F1 was distinguished by the best preservation during three-and seven-month storage. In general, the use of micro-fertilizers and a growth regulator had a positive effect on the preservation of onions.

Alpha-decay induced shortening of fission tracks simulated by in situ ion irradiation

The diffusion of defects (e.g., vacancies and interstitials) and elements used for dating (e.g., He and Pb) in a mineral structure is a thermal process: This is the primary assumption used to determine the age and thermal history of minerals. For instance, thermal history reconstruction, through the number and length distribution of tracks produced by spontaneous fission of 238U, is obtained by assuming a thermal event to be the only energy source for shortening of fission tracks. Here, we report a new, non-thermal energy source that induces additional shortening of fission tracks by the irradiation of alpha-recoils from the alpha-decay of 238U and 232Th. We simulate alpha-decay induced track-shortening by combining ion accelerator irradiations with transmission electron microscopy. This allows for the first observation of track-shrinkage during in situ ion irradiation. We show that rather than alpha-particles, alpha-recoils induce a significant shortening of fission tracks by nuclear-collisions. The shortening of track-length can be quantified as a function of alpha-decay event dose. However, apatite is less sensitive than zircon to this non-thermal process. The findings exemplify the interactions among different types of self-irradiation from alpha-particles, alpha-recoils and fission-fragment nuclei in single mineral grains and have important implications for the use of zircon and apatite for radiometric dating and thermochronology.

Adaptation of foreign technologies of intensive cultivation of scots pine planting material in Kazakhstan

The purpose of the research was the adaptation of foreign technologies for intensive and accelerated cultivation of Scots pine planting material in Kazakhstan. Objects of research were annual seedlings of scots pine in forest nurseries of Pavlodar, Akmola, and North Kazakhstan regions. The experiments were established in 4 directions: application of dry growth regulators to soil, pre-sowing seed treatment with growth regulators, soaking seeds in stimulants and fungicide, pre-sowing watering of the soil with growth regulators. It was established that seed quality decreased significantly compared to the last year, only seeds from Pavlodar region had high indicators. Seeds from the nursery ‘Ertic Ormany’ had the highest average indicators of soil germination (58.7…67.8%). In ‘Bukhpa’, the highest germination was observed in seeds soaked with Zircon + Trichocin (3 + 2 hours). Baikal growth regulator and AridGrow slightly increased germination in the nursery of Arykbalyk branch of ‘Kokshetau’. In the forest nursery ‘Ertis Ormany’, the highest annual seedlings were obtained in variants with presowing treatment of scots pine seeds with stimulants and watering the soil with growth substances. The average height of experimental seedlings was 4.32 and 4.64 cm, respectively. The combined use of Zircon and Trichocin increased seedling growth in ‘Bukpa’ nursery to 1.42 cm, which was the highest value. It was revealed that the technologies used in neighboring countries for intensive cultivation of scots pine seedlings showed a positive effect only when using Citovit. According to other experiments, it was determined that seedlings of scots pine grown from seeds with pre-sowing treatment in Gumat+7 for 12 hours had the best growth indicators in height. Increased soil fertility through applying nitrogen, phosphorus fertilizers, soil activator AridGrow and KZ Cultury significantly accelerated growth of scots pine seedlings.

Improvement of the cucumber protection system in the greenhouse for production environmentally safe products

Production of environmentally friendly cucumber products is one of the important problems of modern vegetable growing. In the current situation, many issues of cucumber technology using the low-volume technology method require adjustment and further improvement. The purpose of the research was to study and assess the effect of combinations of zircon with biofertilizers against the background of the use of biological products on the growth, development, yield and quality of cucumber. The complex treatment of cucumber plants of the F1 Atlet hybrid with biologically active substances (BAS) contributed to an increase in biometric indicators in comparison with the control throughout the entire crop rotation. The period from germination to the beginning of flowering and fruiting decreased, the plant height increased by 7.2–13.2% and the stem diameter by 12.5–17.5%. The yield was significantly influenced by the growth of the leaf area of cucumber plants, which increased in variants with experimental technologies by 5.9–34%. Under the influence of the studied factors, the yield of standard cucumber production increased by 8.0–27.6%. The mass fraction of fruits that do not meet the requirements of the standard was 6.6–8.1%. On the control variant, the output of non-standard products increased to 10%. The highest net income and level of profitability were obtained with the combined use of Zircon with Ecofus, both against the background of the use of biological products (659.3 rubles / m2 or 38.4%) and without them (685.13 rubles / m2 or 40.1%).

Porphyry indicator zircons (PIZs): Application to exploration of porphyry copper deposits

Magmas with a high oxidation state (FMQ + 1 to + 2), a high-water content (≥4 wt% H2O) and a high degree of fractionation are necessary to form porphyry copper deposits (PCDs). Different proxies, such as Fe3+/Fe2+ ratio of whole-rock, minerals indicative of high oxygen fugacity (fO2) and water content as well as geochemical signatures of whole-rock (e.g. high Sr/Y and V/Sc ratios) are commonly used to trace these magmatic conditions. However, these proxies are of limited use for rocks hosting porphyry copper mineralization because the hydrothermal fluids associated with ore deposits obliterate the primary minerals and their initial geochemical signatures. Zircon is a common accessory mineral of igneous rocks that retains its original chemical composition from the time of crystallization, therefore provides information related to parental magmas. Several studies on PCDs worldwide have investigated the geochemical characteristics of zircons (e.g., Hf concentration, Ce4+/Ce3+, Eu/Eu*) as indicators of a high oxidation state, high magmatic water content and high degree of magma fractionation. Here, the petrographic and geochemical characteristics of zircons collected from Chuquicamata, Mirador, Esperanza and Escondida PCDs, located in the upper Eocene to lower Oligocene metallogenic belt of northern Chile, were determined in order to validate the use of zircon as a tracer for porphyry fertility. Our results show that zircon collected from all studied PCDs crystallized from monzogranitic to granodioritic magmas at temperatures below 750 °C and show euhedral morphologies mainly characterized by prismatic forms of type {110} and pyramidal forms of type {101}. Most zircons from PCDs have Hf concentrations > 8,750 (ppm) and Ce/Nd > 1, Eu/Eu* > 0.4, 10,000x(Eu/Eu*)/Y > 1, (Ce/Nd)/Y > 0.01, Dy/Yb < 0.3, Th/U 〈1−〉 0.1. From this group of geochemical values measured on zircon, we propose the Porphyry Indicator Zircon concept (PIZ), where each zircon from PCDs must comply with the previously mentioned geochemical framework. Our results show that studied PCDs have abundant zircons with PIZ characteristic (>54%); at Mirador and Esperanza porphyries the PIZ proportion exceeding 70%. On the other hand, the non-mineralized intrusive bodies have no zircons with PIZ characteristics. Therefore, these results combined with previously published studies from other porphyry belts worldwide, validate zircons as an indicator of metallogenic fertility and its use as a porphyry indicator mineral and a potential exploration tool in search for PCDs.

Agroecological techniques for protecting soybean crops from phytopathogens

The aim of this research was to study the influence of biofungicides and growth regulators on protecting soybean crops from fungal diseases, allowing the production of environmentally friendly and high-quality products. The main pathogens of soy diseases in the Khabarovsk territory are root rot and leaf-stem infections. The means of protection applied in this study reduced the intensity of development of these diseases. The greatest biological effectiveness against root rot was found when the drugs Zircon, Bisolbifit and Tetramethylthiuram Disulfide (TMTD) with Optimo were used. The use of Zircon, Extrasol and Nutri-Phite with water softener Spartan reduced the infection of soy plants with leaf-stem diseases. With these protection systems, the yield level ranged from 3.62 to 3.88 t/ha.

Experimental fluid-mediated alteration of zircon under lower greenschist facies conditions

ABSTRACT The use of zircon in the dating of geological processes and tectonic events has become a standard approach in many aspects of Earth science research. As a result, understanding how zircon interacts with aqueous fluids during metasomatism has become increasingly important. The alteration of natural zircon is driven primarily by coupled dissolution–reprecipitation or by ion-exchange with an aqueous fluid. In this study, whole and intact, euhedral light-brown zircon crystals (100–250 μm in length; 2 mg) from the Oligocene Fish Canyon Tuff (FCT) were experimentally reacted with an alkali-bearing reactive fluid and a REE + P source (0.5 mg CePO4 or 0.5 mg YPO4). Experiments were conducted in sealed Au metal capsules at 350 °C and 100 MPa for 182 days. During the experiment, the zircon became colorless, indicating annealing of the radiation damage in the crystal. Two-dimensional element maps of the outermost 3 μm of unpolished zircon crystal surfaces were produced using a grind of contiguous 7 μm analytical spots via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The chemical maps indicate that the surface of the zircon crystals from each experiment heterogeneously reacted with the fluid, such that the Ce and Y concentration of chemically modified areas increased (by an order of magnitude) in the CePO4-bearing and YPO4-bearing experiments, respectively, when compared with the chemical maps of unaltered zircon grain surfaces. Helium ion microscopy of polished crystals revealed discontinuous micron-scale altered domains at the crystal margin, consistent with the findings of the unpolished mapping technique. Interestingly, the Th and U concentration of the altered zircon grain surfaces were consistent with the unaltered zircon regardless of the experiment. Incorporation of REEs on the zircon grain surface likely occurred via the coupled substitution REE3+ + P5+ ↔ Zr4+ + Si4+. The results from these experiments imply that the surfaces of minimally metamict zircon can be chemically modified by alkali-bearing fluids via ion exchange under lower greenschist pressures and temperatures over relatively short time periods with respect to the geological time scale.

Complete metamorphic cycle and long‐lived anatexis in the c. 2.1 Ga Mistinibi Complex, Canada

AbstractSecular changes in the architecture, thermal state, and metamorphic style of global orogens are thought to have occurred since the Archean; however, despite widespread research, the driving mechanisms for such changes remain unclear. The Paleoproterozoic may prove to be a key era for investigating secular changes in global orogens, as it marks the earliest stage of an eon that saw the onset of modern‐style global tectonics. The 2.1 Ga granulite‐facies Mistinibi‐Raude Domain (MRD), located in the Southeastern Churchill Province, Canada, offers a rare exposure of Paleoproterozoic high metamorphic grade supracrustal sequences (Mistinibi Complex, MC). Rocks from this domain were subjected to petrochronological investigations to establish P–T–t–X evolutions and to provide first order thermal state, burial and exhumation rates, and metamorphic gradients for the transient Paleoproterozoic times. To obtain comprehensive insight into the P–T–t–X evolution of the MRD, we used multi‐method geochronology—Lu–Hf on garnet and U–Pb on zircon and monazite—integrated with detailed petrography, trace element chemistry, and phase equilibria modelling. Despite the extensive use of zircon and monazite as geochronometers, their behaviour in anatectic conditions is complex, leading to substantial ambiguity in interpreting the timing of prograde metamorphism. Our results indicate a clockwise metamorphic path involving significant melt extraction from the metasedimentary rocks, followed by cooling from &gt;815°C to ~770°C at ~0.8 GPa. The timing of prograde burial and cooling from supra‐ to subsolidus conditions is constrained through garnet, monazite, and zircon petrochronology at 2,150–2,120 Ma and at 2,070–2,080 Ma, respectively. These results highlight long‐lived residence of the rocks at mid‐crustal supra‐solidus conditions (55–70 Ma), with preserved prograde and retrograde supra‐solidus monazite and zircon. The rocks record extremely slow burial rates (0.25–0.30 km/Ma) along a high metamorphic gradient (900–1,000°C/GPa), which appears symptomatic of Paleoproterozoic orogens. The MC did not record any significant metamorphism after 2,067 Ma, despite having collided with terranes that record high‐grade metamorphism during the major 1.9–1.8 Ga Trans‐Hudson orogeny. The MC would therefore represent a remnant of a local early Paleoproterozoic metamorphic infrastructure, later preserved as superstructure in the large hot Trans‐Hudson orogen.

Zircon records multiple magmatic-hydrothermal processes at the giant Shizhuyuan W–Sn–Mo–Bi polymetallic deposit, South China

The supergiant Shizhuyuan W–Sn–Mo–Bi polymetallic deposit is located in the Nanling Range, and is intimately related to the Qianlishan granite complex intruded during the Late Jurassic period. The complex consists of three intrusive phases: porphyritic biotite granite (PBG), equigranular biotite granite (EBG), and porphyritic granite dyke. In this work, the distinct geochemical features of magmatic and hydrothermally-altered zircons from the Qianlishan complex are used to reveal the magmatic-hydrothermal evolution of the deposit. Whole-rock geochemistry and mineralogy show that EBG samples have experienced stronger fractional crystallization than PBG samples. Zircon U–Pb dating constrains the intrusive episodes at 155–153 Ma and ~152 Ma for the PBG and EBG, respectively, and subsequent hydrothermal events (revealed by hydrothermal zircon ages) at 154–153 Ma and 152–150 Ma. Hydrothermally-altered zircon and paragenetic mineral inclusions from EBG samples show textures and compositional properties suggesting they were intensely altered by a zirconium saturated aqueous fluid (Type 1), enriched in most trace and metallogenic elements (e.g., Zr, REEs, Hf, P, U, Th, Nb, Ta, Ti, Pb, Al, Fe, Mg, Ca, Mn, W, and Sn) and volatiles (F, Cl, Li, CO2 and H2O). This fluid was relatively lower in temperature, pressure and oxygen fugacity (average Ce4+/Ce3+ = 11.2). Type 2 fluid, represented by hydrothermally-altered zircons found in PBG, was depleted in trace elements and had a relatively higher temperature and pressure and low fO2 (Ce4+/Ce3+ = 2.12–29.16). Type 3 fluid, as evidenced by fluid-altered zircons from the greisenized granite, was likely a further evolved product of the Type 2 fluid, given its moderate cargo of most trace elements but also with exceedingly low Ce4+/Ce3+ values (2.9–33.45). The Type 3 fluids might be precursors of W–Sn mineralizing fluids, whereas the Type 1 fluids were likely to represent mature ore-forming fluids, which were activated during the late skarn stage but before the retrograde mineralization stage. Compared with the fO2 of PBG and EBG magmas calculated by non-altered magmatic zircons (average Ce4+/Ce3+ = 31.47 and 49.21), it seems that the hydrothermal fluids generated by them became more reduced during the further evolution. A progressive process can thus be divided: PBG → Type 2 → Type 3 → EBG → Type 1, with the gradual accumulation of ore-forming materials. The enrichment of most elements in hydrothermal zircons further indicates a substitution of Y, REEs, P, Hf, U, Th, Ti, Nb, Ta, Ca, K, Fe, and Mn for Zr4+ and Si4+ in the zircon lattice. Most fluid-altered zircons exhibit a similar 176Hf/177Hf distribution range (−11 to −6) but evidently elevated 176Lu/177Hf and 176Yb/177Hf ratios with magmatic ones. This indicates that three types of hydrothermal fluids were magmatic-derived, whereas Lu and Yb were highly mobile during the hydrothermal event. Based on the results, a magmatic-hydrothermal evolution model is presented for Shizhuyuan zircons. This research highlights the use of zircon as a powerful tool in revealing the complex magmatic-hydrothermal processes and perhaps mineralization potential in (highly evolved) granite-associated mineralization systems.

Stability of Zircon in the System MgO–SiO2–H2O at 2.5 GPa

Abstract —We report preliminary experimental data on the interaction of zircon with the peridotitic assemblage olivine + serpentine at 2.5 GPa and 1400 °C. In these conditions, zircon is unstable and decomposes with the formation of baddeleyite. Therefore, it is unlikely that zircon could survive in ultramafic rocks for a long time in the presence of a fluid phase at high temperatures. Thus, rigorous constraints on boundary conditions are required for the use of zircon in the dating of high-temperature geologic processes.

Detrital apatite U-Pb and trace element analysis as a provenance tool: Insights from the Yenisey Ridge (Siberia)

The use of zircon U-Pb geochronology to study the provenance of sediment is well-established, yet there are fundamental biases that are hard to avoid. These biases are due, in part, to the limited range of magmatic compositions from which zircon will crystallise. This can manifest as the over/under representation of particular age populations (i.e. sediment sources) in the data. The analysis of apatite, a mineral found in a wide variety of igneous rocks, can help to address this bias in detrital geochronology. In this study, we combine geochemical and U-Pb LA-ICP-MS analysis of individual apatite grains to characterise the potential source rocks. This information is integrated with zircon U-Pb data from the same samples in order to demonstrate the complementary provenance information that can be derived from apatite and zircon archives. The analysis of detrital apatite from sedimentary rocks in the Yenisey Ridge (Siberia) found two main U-Pb age populations. An apatite U-Pb population at 880–720 Ma corresponds to Neoproterozoic magmatism in the Yenisey Ridge, and a second at ~1800 Ma to magmatism related to the assembly of the Siberian Craton. Abundant Neoproterozoic apatites, many of which have chemistries indicative of crystallising from a mafic magma, are considerably more common than the relatively rare zircons of the same age. The ability of apatite analysis to detect mafic magmatic sources is one of the strengths of this approach that makes it particularly useful when used in combination with zircon U-Pb geochronology. This study shows that multi-method analysis of detrital apatite has the potential to be an important tool in conjunction with detrital zircon analysis in future efforts to understand the provenance of sedimentary rocks.

Zircon: The Metamorphic Mineral

A mineral that forms under conditions as variable as diagenesis to deep subduction, melt crystallization to low temperature alteration, and that retains information on time, temperature, trace element and isotopic signatures is bound to be a useful petrogenetic tool. The variety of conditions under which zircon forms and reacts during metamorphism is a great asset, but also a challenge as interpretation of any geochemical data obtained from zircon must be placed in pressure–temperature–deformation–fluid context. Under which condition and by which process zircon forms in metamorphic rocks remains a crucial question to answer for the correct interpretation of its precious geochemical information. In the last 20 years there has been a dramatic evolution in the use of zircon in metamorphic petrology. With the advent of in situ dating techniques zircon became relevant as a mineral for age determinations in high-grade metamorphic rocks. Since then, there has been incredible progress in our understanding of metamorphic zircon with the documentation of growth and alteration textures, its capacity to protect mineral inclusions, zircon thermometry, trace element patterns and their relation to main mineral assemblages, solubility of zircon in melt and fluids, and isotopic systematics in single domains that go beyond U–Pb age determinations. Metamorphic zircon is no longer an impediment to precise geochronology of protolith rocks, but has become a truly indispensable mineral in reconstructing pressure–temperature–time–fluid-paths over a wide range of settings. An obvious consequence of its wide use, is the rapid increase of literature on metamorphic zircon and any attempt to summarize it can only be partial: in this chapter, reference to published works are intended as examples and not as a compilation. This chapter approaches zircon as a metamorphic mineral reporting on its petrography and texture, deformation structure and mineral chemistry, including trace element and isotopic systematics. Linking this information together highlights the potential of zircon as a key mineral in petrochronology.

Mechanisms of deformation-induced trace element migration in zircon resolved by atom probe and correlative microscopy

The widespread use of zircon in geochemical and geochronological studies of crustal rocks is underpinned by an understanding of the processes that may modify its composition. Deformation during tectonic and impact related strain is known to modify zircon trace element compositions, but the mechanisms by which this occurs remain unresolved. Here we combine electron backscatter diffraction, transmission Kikuchi diffraction and atom probe microscopy to investigate trace element migration associated with a ∼20nm wide, 2° low-angle subgrain boundary formed in zircon during a single, high-strain rate, deformation associated with a bolide impact. The low-angle boundary shows elevated concentrations of both substitutional (Y) and interstitial (Al, Mg and Be) ions. The observed compositional variations reflect a dynamic process associated with the recovery of shock-induced vacancies and dislocations into lower energy low-angle boundaries. Y segregation is linked to the migration and localisation of oxygen vacancies, whilst the interstitial ions migrate in association with dislocations. These data represent the direct nanoscale observation of geologically-instantaneous, trace element migration associated with crystal plasticity of zircon and provide a framework for further understanding mass transfer processes in zircon.

Deformation-induced trace element redistribution in zircon revealed using atom probe tomography.

Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal–plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials.

The detrital zircon record: Supercontinents, parallel evolution—Or coincidence?

The interpretation of detrital zircon data is facing some important and potentially damaging inconsistencies that are commonly overlooked: combined U–Pb and Lu–Hf data from detrital zircon in sedimentary rocks have been used successfully to study global processes such as the extraction, growth and preservation of continental crust, suggesting generally similar patterns of evolution in different continents. Yet at the same time, such data are increasingly used to identify the source-rocks of individual clastic deposits, based on the implicit assumption that material from different source terranes carry distinct provenance signatures.For example, Precambrian detrital zircon age-fractions from late Mesoproterozoic to Recent sediments in Laurentia show patterns of U–Pb ages and initial Hf isotope composition indistinguishable from that of zircon from granitoids in Fennoscandia. This is perhaps not too surprising, as Fennoscandia and Laurentia have been near neighbours in three supercontinents (Nuna, Rodinia, Pangea). Transport and homogenization of clastic material in intracontinental basins and along a common continental margin would smooth out differences, and the two neighbouring continents may have closely parallel histories of internal growth.A stronger reason for concern is that Precambrian age fractions in detrital zircon suites from areas as distant as Australia and South Africa also show distribution patterns that cannot be distinguished with confidence from sources in Fennoscandia. These continents have not been near neighbours in post-Archaean supercontinents. Since exchange of detritus between such distant blocks is improbable, one is left with the alternative explanations of pronounced parallel evolution (perhaps related to the assembly of supercontinents in the geological past), or pure coincidence.Whatever the explanation: exchange, parallelism or coincidence, observations such as these challenge the main assumptions underlying the use of zircon as an indicator of sedimentary provenance: That a given age and initial Hf isotopic pattern of a population of detrital zircons can be unequivocally related to a specific first-generation source.

Petrogenesis of Ordovician Magmatism in the Pyrenees (Albera and Canigó Massifs) Determined on the Basis of Zircon Minor and Trace Element Composition

Zircon composition (U, Th, rare earth elements, and Hf) was tested as a tracer of petrogenetic processes in a set of metaigneous rocks from two pre-Ordovician massifs in the Pyrenees, Canigó and Albera. Two groups were differentiated after analyzing a number of elements in zircon: (1) Casemí gneiss and Marialles amphibolite and (2) subvolcanic metaporphyries and Cadí and Sureda orthogneisses. Casemí gneiss and Marialles amphibolite from the Canigó massif have high Th, Th/U, and Ce/Sm and low Yb/Gd and U/Ce that define linear trends in most of the plots used. The anomalous trend of the data in the Th/U-versus-Hf plot suggests mantle involvement in the origin of these rocks and the participation of fractional crystallization during their evolution. Zircon of the metaporphyries and the Cadí and Sureda orthogneisses exhibit similar characteristics despite a difference in age. Zircon has low Th, Th/U, Ce/Sm, and and high Yb/Gd and U/Ce, suggesting that this mineral grew in a melt formed by anatexis of a continental crust, with stable plagioclase. These petrogenetic data are consistent with the previously studied whole-rock geochemistry and Sr-Nd isotopes and confirm the use of zircon as a marker of petrogenetic processes in preference to a lithological tracer.