Zircon Oxygen Research Articles

Origin of the Yinshan epithermal-porphyry Cu–Au–Pb–Zn–Ag deposit, southeastern China: insights from geochemistry, Sr–Nd and zircon U–Pb–Hf–O isotopes

The Yinshan deposit is a large epithermal-porphyry polymetallic deposit, and the timing and petrogenesis of ore-hosting porphyries have been hotly debated. We present new results from geochemical, whole-rock Sr–Nd and zircon U–Pb–Hf–O isotopic investigations. Zircon U–Pb data demonstrate that the quartz porphyry, dacitic porphyry, and quartz dioritic porphyry formed at ˜172.2 ± 0.4 Ma, ˜171.7 ± 0.5 Ma, and ˜170.9 ± 0.3 Ma, respectively. Inherited zircon cores show significant age spreads from ˜730 to ˜1390 Ma. Geochemically, they are high-K calc-alkaline or shoshonitic rocks with arc-like trace element patterns. They have similar whole-rock Nd and zircon Hf isotopic compositions, yet an increasing trend in ϵNd(t) and ϵHf(t) values typifies the suite. Older (inherited) zircons of the three porphyries display Hf compositions comparable to those of the Jiangnan Orogen basement rocks. In situ zircon oxygen isotopic analyses reveal that they have similar oxygen isotopic compositions, which are close to those of mantle zircons. Moreover, a decreasing trend of δ18O values is present. We propose that the ore-related porphyries of the Yinshan deposit were emplaced contemporaneously and derived from partial melting of Neoproterozoic arc-derived mafic (or ultra-mafic) rocks. Modelling suggests that the quartz porphyries, dacitic porphyries, and quartz dioritic porphyries experienced ˜25%, ˜10%, and ˜10% crustal contaminations by Shuangqiaoshan rocks. Our study provides important constraints on mantle–crust interaction in the genesis of polymetallic mineralization associated with Mesozoic magmatism in southeastern China.

Zircon U-Pb isotope, 18O and trace element response to 80 m.y. of high temperature metamorphism in the lower crust: Sluggish diffusion and new records of Archean craton formation

Coordinated cathodoluminescence (CL) imaging and ion microprobe (SHRIMP and CAMECA 1280) analysis document micron-scale U-Pb-O isotope and trace element zoning in zircons from deep crust exposed to 80 m.y. of high temperature and pressure metamorphism. Three, along-strike paragneiss samples across the amphibolite to granulite facies transition in the Kapuskasing Uplift crustal cross-section in the Archean Superior province yield detrital, originally igneous zircon cores overgrown by progressively larger volumes of metamorphic zircon with increasing grade. The cores generally retain primary age (2.85±0.03 to 2.67±0.02 Ga), oxygen isotope (5.1 to 7.0‰) and trace element compositions similar to those reported for magmatic arc sources. Dark CL, metamorphic zircon rims record nearly continuous overgrowth events for ∼80 m.y. from 2.66±0.01 to 2.58±0.01 Ga during uppermost amphibolite to granulite facies regional metamorphism. These rims have significantly higher δ18O values (8.4 to 10.4‰) and trace element compositions quite distinct from those of the cores; these differences indicate that their δ18O and trace element compositions were not inherited from the igneous cores, consistent with extensive textural evidence for rim formation as metamorphic overgrowths. Multi-spot traverses record steep oxygen isotope discontinuities (4‰ over <10 μm) at core-rim boundaries, confirming the extremely sluggish rates of volume diffusion of O in non-metamict zircon during extended (∼80 m.y.) granulite-grade metamorphism (peak T=750-800 °C) at substantial f(H2O) but water-undersaturated (fluid-absent) conditions. Likewise no evidence of significant diffusive exchange of δ18O could be detected along deformation microstructures such as annealed fractures in cores infilled with high δ18O zircon. Application of simple diffusion models to detailed δ18O profiles in a large number of zircon grains constrain maximum values of the diffusivity of oxygen in zircon (logDZrcox) to the range −27.5 to −26.4 m2/s. For the estimated 80 m.y. and 700 to 800 °C time-T window of rim formation, these maximum values are similar to or slower than values reported by [Page and others (2007][1], [2010)][2] and the experimentally-determined “dry” diffusivity of oxygen in zircon ([Watson and Cherniak, 1997][3]), but are markedly slower than the experimentally-determined “wet” diffusivity of oxygen in zircon ([Watson and Cherniak, 1997][3]). Fast diffusion of oxygen in zircon predicted by hydrothermal experiments may, in nature, require the presence of a hydrous fluid rather than a threshold value of f(H2O). Our test demonstrates that unrecrystallized metamorphosed igneous zircons and metamorphic zircons will retain the geochemical (U-Pb age, trace element and δ18O) record of their origin and evolution despite prolonged, high-grade metamorphism at significant f(H2O) but water under-saturated (fluid-absent) conditions. Such zircons, particularly those that exhibit δ18O zoning, are micron-scale records for the T-time-fluid interaction history of deep crustal rocks. Such records will not be preserved in less refractory phases and promise new insights into the processes of continent formation and evolution. [1]: #ref-64 [2]: #ref-65 [3]: #ref-96

Evidence from Dwyka tillite cobbles of Archaean basement beneath the Kalahari sands of southern Africa

We have found a new source of information about what lies beneath the Kalahari sands. The Kheis and Rehoboth Provinces of southern Africa were thought to be underlain by either an ~1800Ma orogenic belt, or a northern branch of the ~1200Ma Namaqua–Natal Province. Glacial diamictites of the Permocarboniferous Dwyka Group exposed at Rietfontein west of the Kalahari sands carry cobbles plucked from the bedrock by the ice sheet which covered the Gondwana supercontinent about 300Ma ago. Despite altered mineralogy, the cobbles are not severely altered geochemically. Their normative mineral compositions give classifications as trondhjemites and granites, supported by rare earth element diagrams. Microbeam U–Pb zircon dating of the granitic cobbles shows that they contain no evidence of crustal growth or orogeny at either 1800 or 1200Ma. Rather they testify to the presence of 2500 to 2900Ma Archaean trondhjemitic and granitic crust beneath the Kalahari, with a lesser ~2050Ma granite component. The pebble assemblages from the diamictites we sampled lack the diagnostic banded iron formation (BIF), stromatolitic limestone and other supracrustal pebbles which characterise diamictites derived from the Kaapvaal Craton, thus we envisage shorter transport distances and derivation from the region now beneath the Kalahari sands. Three of the Archaean granite cobbles have unusual less-than-mantle zircon oxygen isotope values around +3 (δ18O VSMOW), which may reflect interaction of their source with high-temperature, originally meteoric water before melting to produce the granites. The mafic cobbles described in a companion paper are much younger and are related to intrusions of the 1.1Ga Umkondo Large Igneous Province, probably located on the Kalahari Line or Rehoboth Province.Five trondhjemitic granites from the westernmost outcrops of the Kaapvaal Craton were dated, the oldest being 3061±9Ma and four others between 2882±7Ma and 2854±7Ma, reflecting the cratonisation of the Kimberley Terrane. Four of the Archaean Dwyka cobbles we dated are younger than the 2.7Ga Kaapvaal cover sequence and are thus too young to be derived from the craton.All the Dwyka cobbles described here are most likely derived from either the Rehoboth Province or the Kalahari Line with origins from the Kheis Province, Kaapvaal Craton, or further afield considered unlikely. We envisage the Rehoboth Province to consist of an Archaean core supplemented by Palaeoproterozoic granitoids, which was joined to the Kaapvaal Craton at an early stage of crustal development and played an important role during later tectonic events. This has important implications not only for the tectonic framework and assembly of Southern Africa, but also for exploration for diamonds and other ore deposits.

Archaean fluid-assisted crustal cannibalism recorded by low δ18O and negative εHf(T) isotopic signatures of West Greenland granite zircon

The role of fluids during Archaean intra-crustal magmatism has been investigated via integrated SHRIMP U–Pb, δ18O and LA-MC-ICPMS 176Hf isotopic zircon analysis. Six rock samples studied are all from the Nuuk region (southern West Greenland) including two ~3.69 Ga granitic and trondhjemitic gneisses, a 3.64 Ga granitic augen gneiss, a 2.82 Ga granodioritic Ikkattoq gneiss, a migmatite with late Neoarchaean neosome and a homogeneous granite of the 2.56 Ga Qôrqut Granite Complex (QGC). All zircon grains were thoroughly imaged to facilitate analysis of magmatic growth domains. Within the zircon analysed, there is no evidence for metamictization. Initial εHf zircon values (n = 63) are largely sub-chondritic, indicating the granitic host magmas were generated by the remelting of older, un-radiogenic crustal components. Zircon from some granite samples displays more than one 207Pb/206Pb age, and correlated with 176Hf/177Hf compositions can trace multiple phases of remelting or recrystallization during the Archaean. Model ages calculated using Lu/Hf arrays for each sample indicate that the crustal parental rocks to the granites, granodiorites and trondhjemites segregated from a chondrite-like reservoir at an earlier time during the Archaean, corresponding to known formation periods of more primitive tonalite–trondhjemite–granodiorite (TTG) gneisses. Zircon from the ~3.69 Ga granite, the migmatite and QGC granite contains Eoarchaean cores with chondritic 176Hf/177Hf and mantle-like δ18O compositions. The age and geochemical signatures from these inherited components are identical to those of surrounding tonalitic gneisses, further suggesting genesis of these granites by remelting of broadly tonalitic protoliths. Zircon oxygen isotopic compositions (n = 62) over nine age populations (six igneous and three inherited) have weighted mean or mean δ18O values ranging from 5.8 ± 0.6 to 3.7 ± 0.5‰. The 3.64 Ga granitic augen gneiss sample displays the highest δ18O with a mildly supra-mantle composition of 5.8 ± 0.6‰. Inherited Eoarchaean TTG-derived zircon shows mantle-like values. Igneous zircon from all other samples, spanning more than a billion years of Archaean time, record low δ18O sub-mantle compositions. These are the first low δ18O signatures reported from Archaean zircon and represent low δ18O magmas formed by the remelting and metamorphism of older crustal rocks following high-temperature hydrothermal alteration by meteoric water. Meteoric fluid ingress coupled with crustal extension, associated high heat flow and intra-crustal melting are a viable mechanism for the production of the low δ18O granites, granodiorites and trondhjemites reported here. Both high and low δ18O magmas may have been generated in extensional environments and are distinct in composition from Phanerozoic I-type granitic plutonic systems, which are typified by increasing δ18O during intra-crustal reworking. This suggests that Archaean magmatic processes studied here were subtly different from those operating on the modern Earth and involved extensional tectonic regimes and the predominance of remelting of hydrothermally altered crystalline basement.

Determining high precision, in situ, oxygen isotope ratios with a SHRIMP II: Analyses of MPI-DING silicate-glass reference materials and zircon from contrasting granites

The development of new techniques and instrumentation on the ANU SHRIMP II ion microprobe has made it possible to measure the oxygen isotope ratios of insulating and conducting phases (e.g. silicates, carbonates, phosphates and oxides) on a 25 µm scale with better than 0.4‰ precision and accuracy at 95% confidence. Instrumentation changes include the installation of a multiple collector, charge neutralization using an oblique-incidence low-energy electron gun, and the addition of Helmholtz coils to counter mass dispersion by the Earth's magnetic field. A redesign of sample mounts and mount holders has effectively eliminated differences in variable isotope fractionation across the mount surface during analysis. Techniques have been developed to minimize the effect of electron-induced secondary ionization of oxygen. During a 6-minute analysis involving 100–140 s of data collection, δ 18O values can be measured on one 25 µm spot with an internal precision of better than 0.2‰ (2 standard errors). Analyses of MPI-DING silicate-glass reference material demonstrate that the external reproducibility of single spots can be better than 0.4‰ at 95% confidence, and that for matrix-matched samples and reference material, accuracy is commensurate with precision. MPI-DING glasses are acceptable ion microprobe reference materials for oxygen isotope measurements of glasses, although KL2-G is possibly heterogeneous. Zircon reference materials TEMORA 2 and FC1 appear to be acceptable as preliminary oxygen isotope reference materials. SHRIMP II analyses of FC1 indicate that it has a δ 18O value of 5.4‰ (VSMOW). Analyses of zircon oxygen isotopic compositions from a gabbro, a tonalite and a granodiorite from southeastern Australia are presented. Zircon from the gabbro has a δ 18O value of 5.6‰, the tonalite has an I-type affinity and slightly heterogeneous δ 18O values around 6.6‰, and the granodiorite has an S-type affinity and a range of igneous, melt precipitated zircon δ 18O values between 8.2 and 10.2‰. These results suggest that the gabbro is mantle-derived and slightly contaminated with crustal material, and that the I-type granodiorite has evolved in a similar manner from a mantle-derived source. The δ 18O values of the zircon from the S-type granodiorite are not only higher than from the I-type, but also more heterogeneous, consistent with partial melting of a poorly-mixed, metasedimentary source.

Zircon oxygen isotopic constraint on the sources of late Mesozoic A-type granites in eastern China

A-type granites are usually derived from partial melting of the lower crust and/or the upper mantle within extensional settings, but their exact sources for specific plutons are required to unravel. A systematic laser fluorination analysis of oxygen isotopes was carried out for five well-documented late Mesozoic A-type granites in eastern China. Zircon from 41 samples was separated and 109 aliquots of fresh zircon were analyzed along with whole-rock powder and quartz from the same samples. Hydrothermally altered whole-rock samples show scattered δ 18O values of − 2.3 to 7.4‰, with a total variation up to 9.7‰. In contrast, zircon δ 18O values vary only from 3.1 to 5.4‰, with a range of 2.3‰. Most available zircon δ 18O values of A-type granites are lower than normal mantle zircon values of 5.3 ± 0.6‰ (2SD), and high-temperature equilibrium fractionations are well preserved between quartz and zircon in most cases. The above lines of evidence suggest that the low δ 18O zircons in A-type granites were crystallized from low δ 18O magmas. Because low δ 18O magmas cannot be derived entirely from the mantle, reworking and/or recycling of crustal igneous rocks are involved for their petrogenesis. The low δ 18O zircons in this study thus offer evidence for a dominantly crustal origin of the late Mesozoic A-type granites in eastern China.

The onset and origin of differentiated Rhine Graben volcanism based on U-Pb ages and oxygen isotopic composition of zircon

Ion microprobe U-Pb zircon ages for late (phase II) syenite dikes of the Katzenbuckel (SW Germany) average 69.6 ± 1.9 Ma (mean square of weighted deviates MSWD =0.36; number of spot analyses n =9; 2σ error) and represent a minimum age for the emplacement of earlier, volumetrically dominant phonolites and nepheline syenites (phase I). This age is ~ 13 and 6 Ma older than previously published K-Ar whole-rock and bulk biotite ages for phase I rocks, respectively. Because of close chemical affinities in magma composition and the small volume of the Katzenbuckel subvolcanic intrusion, zircon crystallization in phase II syenite dikes presumably only shortly postdates phase I magmatism. Trachytes from the Northern Upper Rhine Graben (Sprendlinger Horst, Wetterau) yielded similar U-Pb zircon ages of 68.1 ± 1.4 Ma (MSWD =2.2) and 70.3 ± 1.6 Ma (MSWD =0.4), respectively. Zircon oxygen isotopic ratios of Katzenbuckel indicate primitive mantle-like compositions, whereas Sprendlinger Horst and Wetterau trachytes zircons show minor crustal contamination. The investigated differentiates rank among the oldest known post-Permian igneous rocks in the Northern foreland of the Alpine collisional belt, and are contemporaneous with recently dated lamprophyres in the Northern Rhine Graben area. This suggests that a short (<1–2 Ma) but regionally widespread magmatic pulse occurred along the E and NE flanks of the nascent Rhine Graben rift as early as Late Maastrichtian.

Mobility of trace elements and oxygen in zircon during metamorphism: Consequences for geochemical tracing

This study addresses the mobility of the rare earth elements (REE), O, U and Pb during the formation of metamorphic zircon by overgrowth and coupled dissolution–reprecipitation. For this purpose, the texture and REE, δ18O and U–Pb compositions of zircon crystals from a metabasite, an anatectic granite and a metapelite sampled on Naxos Island (Greece) have been characterised. The behaviour of O and REE during the formation of the zircon metamorphic domains shows that two end-members can be distinguished:(i)Closed (or partially closed) system behaviour for oxygen and trace elements in zircon formed by coupled dissolution–reprecipitation. Metamorphic domains partially preserve the textural and geochemical characteristics of the precursor zircon. Chemical or isotopic equilibrium between the metamorphic zircon and the matrix is not completely reached for all the elements. Such zircons have to be used with caution for geochemical tracing. When re-equilibration is not complete, the U–Pb system is also not completely reset and the metamorphic domains yield old, scattered ages.(ii)Open system behaviour for oxygen and trace elements in zircon formed by overgrowth. These metamorphic zircons do not show an inherited shape and are devoid of relic magmatic zoning. Their composition reflects growth in an open system at the scale of the zircon grain with the fluid phase and the surrounding minerals. Because equilibrium between the metamorphic zircon and the matrix was thus favoured, zircon crystallisation can be more confidently related to the P–T history and fluid circulation events by geochemical tracing.

Early Earth Mirrored in Zircon

GEOLOGY The oldest minerals on Earth—a few dating as much as 4.4 billion years ago—are igneous zircons that have been eroded and incorporated into comparatively younger 3.8-billion-year-old sedimentary rocks. Several studies have examined the geochemistry of these zircons and inferred conditions on early Earth and the composition of its early crust. Initial results based on the zircon oxygen isotopic compositions and trace element chemistry have implied that liquid water was abundant and that some magmas were cool and water-rich. Two related studies provide expanded data and additional constraints. Harrison et al. examined the titanium content of zircons, which can be related to the crystallization temperature and thus the water and silica content of a magma. Through a comparative study of zircons in younger granites, they argue that the overall distribution of data in the very old zircons is most consistent with derivation from magmas that formed by remelting of water-rich crust. Trail et al. examined the oxygen isotope compositions and confirmed that several grains have high 18O/16O ratios, implying derivation of the host magma from water-altered crust or sediments. Together the data imply that early Earth had a vigorous rock cycle involving water, erosion, and burial and heating of sediments, like that operating today. — BH Geology 35 , 635 (2007); Geochem. Geophys. Geosyst. 8 , 10.1029/2006GC001449 (2007).

Constraints on Hadean zircon protoliths from oxygen isotopes, Ti‐thermometry, and rare earth elements

We report zircon oxygen isotope ratios and reconnaissance Ti‐in‐zircon concentrations, guided by cathodoluminescence image studies, for detrital zircons up to 4.34 Ga from the Narryer Gneiss Complex of Western Australia. Zircon oxygen isotope results bolster the view that some Hadean (&gt;3.85 Ga) zircon source melts were enriched in heavy oxygen, a sensitive proxy for melt contamination by sediments altered in liquid water. Zircon crystallization temperatures calculated from Ti concentration in pre‐3.8 Ga zircons yield values around 680°C in all cases except for one lower value in a 4.0 Ga grain. Elevated zircon δ18O values reported here and elsewhere, combined with low minimum‐melt crystallization temperatures, and analysis of zircon/melt partitioning of rare earth elements (REEs) provide mutually consistent lines of evidence that the Hadean Earth supported an evolved rock cycle which included formation of granitic water‐saturated melts, extensive continental crust, hydrosphere‐lithosphere interactions, and sediment recycling within the first 150 million years of planet formation.

Short- and medium-range structure of amorphous zircon from molecular dynamics simulations

We have obtained new insights into the structure of amorphous zircon using classical molecular dynamics simulations with a partial charge model. We present detailed structural characterizations of the simulated high and low density amorphous zircon and compare our results with available neutron diffraction, EXAFS, NMR and other experimental results. The results show that amorphization leads to polymerization of the silicon-oxygen network and the formation of regions rich in zirconium. The average n value of Qn species is 1.6-1.8. A considerable percentage of the oxygen ions (around 20%) have only zirconium in the first coordination shell (free oxygen) in amorphous zircon. The Zr-O bond length (around 2.10?) is shorter and the oxygen coordination number around zirconium smaller (6-7) than those in crystalline zircon, in good agreement with the EXAFS results. The total structure factors of simulated amorphous zircon also agree well with neutron diffraction results. We have examined the effects of the simulation cell size and relative density on the amorphous structure. The general features such as polymerization of silicon-oxygen network and the formation of clustered zirconium rich regions appear to be independent of system size and volume expansion in the range of 11 to 18%. Based on the obtained amorphousmore » zircon structure, experimentally observed lower chemical durability of amorphous zircon compared to its crystalline form can be explained by the existence of the silicon-oxygen networks and zirconium rich regions in amorphous zircon that provides diffusion channels and eases dissolution processes. Battelle operates PNNL for the USDOE« less

Oxygen isotopic signature of 4.4–3.9 Ga zircons as a monitor of differentiation processes on the Moon

We report oxygen isotopic compositions for 14 zircon grains from a sample of sawdust from lunar breccia 14321. The zircons range in age from ∼4.4 to 3.9 Ga and in U and Th content from a few to several hundred ppm. As such these grains represent a range of possible source rocks, from granophyric to mafic composition, and cover the total age range of the major initial lunar bombardment. Nevertheless, results show that the oxygen isotopic compositions of the zircons fall within a narrow range of δ 18O of about 1 per mil and have δ 18O values indistinguishable from those observed for terrestrial mid-ocean ridge basalts confirming the coincidence of lunar and Earth oxygen isotopic compositions. In the δ 17O vs. δ 18O, coordinates data form a tight group with a limited trend on the terrestrial fractionation line. The zircon oxygen isotopes show minimal evidence of the extreme and variable mineral differentiation and element fractionation that have contributed to the formation of their parent rocks.

Magmatic zircon oxygen isotopes of 1.88–1.87 Ga orogenic and 1.65–1.54 Ga anorogenic magmatism in Finland

Oxygen isotope ratios of igneous zircon from magmatic rocks in Finland provide insights into the evolution and growth of the Precambrian crust during the Svecofennian orogeny. These data preserve magmatic δ18O values and correlate with major discontinuities in the lower crust. Oxygen isotope ratios of zircon across the 1.88–1.87 Ga Central Finland granitoid complex (CFGC) range from 5.50‰ to 6.84‰, except for three plutons in contact with the adjacent greenstone and metasedimentary belts (δ18O(Zrc) = 7.60‰–7.78‰). There is a systematic variation in δ18O(Zrc) with respect to geographic location in the CFGC, ranging from 6.60±0.23‰ (σ) in the northeast to 5.90±0.40‰ in the west-southwest. These values correlate with a change in crustal thickness and shift in geochemical composition. The oxygen isotope composition of the 1.65–1.54 Ga rapakivi granites and related rocks in southern Finland show a decreasing trend from north to south, independent of their emplacement age. The southern anorogenic granite group has an average δ18O in zircon of 6.14±0.07‰ and the northern anorogenic group has an average δ18O in zircon of 8.14±0.59‰. This difference reflects the boundary between island arc terrains accreted during the Paleoproterozoic.

Diffusion in Zircon

Despite its low abundance in most rocks, zircon is extraordinarily useful in interpreting crustal histories. The importance of U-Th-Pb isotopic dating of zircon is well and long established (Davis et al., this volume; Parrish et al., this volume). Zircon also tends to incorporate trace elements useful as geochemical tracers, such as the REE, Y, and Hf. A number of characteristics of zircon encourage the preservation of internal isotopic and chemical variations, often on extremely fine scale, which provide valuable insight into thermal histories and past geochemical environments. The relative insolubility of zircon in crustal melts and fluids, as well as its general resistance to chemical and physical breakdown, often result in the existence of several generations of geochemical information in a single zircon grain. The fact that this information is so frequently retained (as evidenced through backscattered electron or cathodoluminescence imaging that often reveal fine-scale zoning down to the sub-micron scale) has long suggested that diffusion of most elements is quite sluggish in zircon. In this chapter, we present an overview of the findings to date from laboratory measurements of diffusion of cations and oxygen in zircon. Because of its importance as a geochronometer, attempts have been made to measure diffusion (especially of Pb) for over 30 years. But only in the last decade or so have profiling techniques with adequate depth resolution been employed in these studies, resulting in a plethora of new diffusion data. These findings have important implications for isotopic dating, interpretation of stable-isotope ratios, closure temperatures, and formation and preservation of primary chemical composition and zoning in zircon. Efforts have been made for some time to quantify and characterize diffusion in zircon, most notably of Pb, in deference to its significance in interpreting Pb isotopic signatures and refining understanding of thermal histories. As is evident from …

Theoretical study of point defects in crystalline zircon

We present a numerical study of point defects in crystalline zircon (ZrSiO4). Vacancies and interstitials of all the constituents of zircon have been considered. For each defect, the structure and the formation energies have been calculated. Calculations, using the supercell method, are based on the Density Functional Theory in the Local Density Approximation. Empirical potentials have also been considered for comparison with electronic structure results. We find a formation energy for the oxygen interstitial of 1.7 eV. This value is compatible with the experimental activation energy for oxygen diffusion in zircon, which proves an interstitial mechanism for the diffusion of oxygen in zircon. For all other defects the calculated formation energies lead to negligible thermal concentration at equilibrium.

Eclogites in California

Previous articleNext article FreeEclogites in CaliforniaRuliff S. HolwayRuliff S. Holway Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 12, Number 4May - Jun., 1904 Article DOIhttps://doi.org/10.1086/621162 Views: 277Total views on this site Citations: 8Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Cyril Chelle-Michou, Anders McCarthy, Jean-François Moyen, Peter A. Cawood, Fabio A. Capitanio Make subductions diverse again, Earth-Science Reviews 226 (Mar 2022): 103966.https://doi.org/10.1016/j.earscirev.2022.103966Loren A. Raymond A metasomatic setting, the Russian River Arch, and gravitational emplacement in the history of eclogites at the classic eclogite locality of Jenner, California, USA, International Geology Review 59, no.5-65-6 (Jul 2016): 577–598.https://doi.org/10.1080/00206814.2016.1213143F. Zeb Page, Eric J. Essene, Samuel B. Mukasa, John W. Valley A Garnet–Zircon Oxygen Isotope Record of Subduction and Exhumation Fluids from the Franciscan Complex, California, Journal of Petrology 55, no.11 (Nov 2013): 103–131.https://doi.org/10.1093/petrology/egt062F. Zeb Page, Lora S. Armstrong, Eric J. Essene, Samuel B. Mukasa Prograde and retrograde history of the Junction School eclogite, California, and an evaluation of garnet–phengite–clinopyroxene thermobarometry, Contributions to Mineralogy and Petrology 153, no.55 (Dec 2006): 533–555.https://doi.org/10.1007/s00410-006-0161-9Gaston Godard Eclogites and their geodynamic interpretation: a history, Journal of Geodynamics 32, no.1-21-2 (Aug 2001): 165–203.https://doi.org/10.1016/S0264-3707(01)00020-5S. S. Sorensen,, J. N. Grossman, M. R. Perfit Phengite-hosted LILE Enrichment in Eclogite and Related Rocks: Implications for Fluid-Mediated Mass Transfer in Subduction Zones and Arc Magma Genesis, Journal of Petrology 38, no.11 (Jan 1997): 3–34.https://doi.org/10.1093/petroj/38.1.3M. J. Giaramita, S. S. Sorensen Primary fluids in low-temperature eclogites: evidence from two subduction complexes (Dominican Republic, and California, USA), Contributions to Mineralogy and Petrology 117, no.33 (Aug 1994): 279–292.https://doi.org/10.1007/BF00310869Charles F. Davidson II.—The Archæan Rocks of the Rodil District, South Harris, Outer Hebrides, Transactions of the Royal Society of Edinburgh 61, no.11 (Jul 2012): 71–112.https://doi.org/10.1017/S0080456800018056