Crystallization thermometers for zircon and rutile
03 Mar 2006-Contributions to Mineralogy and Petrology (Springer-Verlag)-Vol. 151, Iss: 4, pp 413-433
TL;DR: In this article, the authors present the combined results of high pressure-temperature experiments and analyses of natural zircons and rutile crystals that reveal systematic changes with temperature in the uptake of Ti in zircon and Zr in Rutile.
Abstract: Zircon and rutile are common accessory minerals whose essential structural constituents, Zr, Ti, and Si can replace one another to a limited extent. Here we present the combined results of high pressure–temperature experiments and analyses of natural zircons and rutile crystals that reveal systematic changes with temperature in the uptake of Ti in zircon and Zr in rutile. Detailed calibrations of the temperature dependencies are presented as two geothermometers—Ti content of zircon and Zr content of rutile—that may find wide application in crustal petrology. Synthetic zircons were crystallized in the presence of rutile at 1–2 GPa and 1,025–1,450°C from both silicate melts and hydrothermal solutions, and the resulting crystals were analyzed for Ti by electron microprobe (EMP). To augment and extend the experimental results, zircons hosted by five natural rocks of well-constrained but diverse origin (0.7–3 GPa; 580–1,070°C) were analyzed for Ti, in most cases by ion microprobe (IMP). The combined experimental and natural results define a log-linear dependence of equilibrium Ti content (expressed in ppm by weight) upon reciprocal temperature:
$$\log ({\text{Ti}}_{{{\text{zircon}}}}) = (6.01 \pm 0.03) - \frac{{5080 \pm 30}}{{T\;(\hbox{K})}}.$$
In a strategy similar to that used for zircon, rutile crystals were grown in the presence of zircon and quartz (or hydrous silicic melt) at 1–1.4 GPa and 675–1,450°C and analyzed for Zr by EMP. The experimental results were complemented by EMP analyses of rutile grains from six natural rocks of diverse origin spanning 0.35–3 GPa and 470–1,070°C. The concentration of Zr (ppm by weight) in the synthetic and natural rutiles also varies in log-linear fashion with T
−1:
$$\log ({\text{Zr}}_{{{\text{rutile}}}}) = (7.36 \pm 0.10) - \frac{{4470 \pm 120}}{{T\;(\hbox{K})}}.$$
The zircon and rutile calibrations are consistent with one another across both the synthetic and natural samples, and are relatively insensitive to changes in pressure, particularly in the case of Ti in zircon. Applied to natural zircons and rutiles of unknown provenance and/or growth conditions, the thermometers have the potential to return temperatures with an estimated uncertainty of ±10 ° or better in the case of zircon and ±20° or better in the case of rutile over most of the temperature range of interest (∼400–1,000°C). Estimates of relative temperature or changes in temperature (e.g., from zoning profiles in a single mineral grain) made with these thermometers are subject to analytical uncertainty only, which can be better than ±5° depending on Ti or Zr concentration (i.e., temperature), and also upon the analytical instrument (e.g., IMP or EMP) and operating conditions.
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TL;DR: In this article, the first finding of continental crust-derived Precambrian zircons in garnet/spinel pyroxenite veins within mantle xenoliths carried by the Neogene Hannuoba basalt in the central zone of the North China Craton (NCC).
Abstract: We present the first finding of continental crust-derived Precambrian zircons in garnet/spinel pyroxenite veins within mantle xenoliths carried by the Neogene Hannuoba basalt in the central zone of the North China Craton (NCC). Petrological and geochemical features indicate that these mantle-derived composite xenoliths were formed by silicic melt^lherzolite interaction. The Precambrian zircon ages can be classified into three age groups of 2·4^2·5 Ga, 1·6^2·2 Ga and 0·6^1·2 Ga, coinciding with major geological events in the NCC. These Precambrian zircons fall in the field of continental granitoid rocks in plots of U/Yb vs Hf and Y. Their igneous-type REE patterns and metamorphic zircon type CL images indicate that they were not crystallized during melt^peridotite interaction and subsequent high-pressure metamorphism.The 2·5 Ga zircons have positive eHf(t) values (2·9^10·6), whereas the younger Precambrian zircons are dominated by negative eHf(t) values, indicating an ancient continental crustal origin.These observations suggest that the Precambrian zircons were xenocrysts that survived melting of recycled continental crustal rocks and were then injected with silicate melt into the host peridotite. In addition to the Precambrian zircons, igneous zircons of 315 3 Ma (2 ), 80^170 Ma and 48^64 Ma were separated from the garnet/spinel pyroxenite veins; these provide evidence for lower continental crust and oceanic crust recycling-induced multi-episodic melt^peridotite interactions in the central zone of the NCC. The combination of the positive eHf(t) values (2·91^24·6) of the 315 Ma zircons with the rare occurrence of 302^324 Ma subduction-related diorite^granite plutons in the northern margin of the NCC implies that the 315 Ma igneous zircons might record melt^peridotite interactions in the lithospheric mantle induced by Palaeo-Asian oceanic crust subduction. Igneous zircons of age 80^170 Ma generally coexist with the Precambrian metamorphic zircons and have lower Ce/Yb and Th/U ratios, higher U/Yb ratios and greater negative Eu anomalies.The eHf(t) values of these zircons vary greatly from ^47·6 to 24·6.The 170^110 Ma zircons are generally characterized by negative eHf(t) values, whereas the 110^100 Ma zircons have positive eHf(t) values.These observations suggest that melt^peridotite interactions at 80^170 Ma were induced by partial melting of recycled continental crust. The 48^64 Ma igneous zircons are characterized by negligible Ce anomalies, unusually high REE, U and Th contents, and positive eHf(t) values.These features imply that the melt^peridotite interactions at 48^64 Ma could be associated with a depleted mantle-derived carbonate melt or fluid.
2,753 citations
Additional excerpts
...(b) Temperatures calculated with theTi-in-zircon thermometer (Watson et al., 2006)....
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TL;DR: In this paper, the authors show that the Zr content of rutile coexisting with zircon increases with decreasing the activity of SiO2 and demonstrate that the substitution of Ti in Zircon is primarily for Si.
Abstract: The models recognize that ZrSiO4, ZrTiO4, and TiSiO4, but not ZrO2 or TiO2, are independently variable phase components in zircon. Accordingly, the equilibrium controlling the Zr content of rutile coexisting with zircon is ZrSiO4 = ZrO2 (in rutile) + SiO2. The equilibrium controlling the Ti content of zircon is either ZrSiO4 + TiO2 = ZrTiO4 + SiO2 or TiO2 + SiO2 = TiSiO4, depending whether Ti substitutes for Si or Zr. The Zr content of rutile thus depends on the activity of SiO2
$$(a_{\text{SiO}_{2}})$$
as well as T, and the Ti content of zircon depends on $$a_{\text{SiO}_{2}}$$
and
$$a_{\text{TiO}_{2}}$$
as well as T. New and published experimental data confirm the predicted increase in the Zr content of rutile with decreasing $$a_{\text{SiO}_{2}},$$
and unequivocally demonstrate that the Ti content of zircon increases with decreasing $$a_{\text{SiO}_{2}}$$
. The substitution of Ti in zircon therefore is primarily for Si. Assuming a constant effect of P, unit $$a_{\text{ZrSiO}_{4}},$$
and that $$a_{\text{ZrO}_{2}}$$
and $$a_{\text{ZrTiO}_{4}}$$
are proportional to ppm Zr in rutile and ppm Ti in zircon, [log(ppm Zr-in-rutile) + log
$$a_{\text{SiO}_{2}}$$
] = A1 + B1/T(K) and [log(ppm Ti-in-zircon) + log
$$a_{\text{SiO}_{2}}$$
− log
$$a_{\text{TiO}_{2}}$$
] = A2 + B2/T, where the A and B are constants. The constants were derived from published and new data from experiments with $$a_{\text{SiO}_{2}}$$
buffered by either quartz or zircon + zirconia, from experiments with $$a_{\text{SiO}_{2}}$$
defined by the Zr content of rutile, and from well-characterized natural samples. Results are A1 = 7.420 ± 0.105; B1 = −4,530 ± 111; A2 = 5.711 ± 0.072; B2 = −4,800 ± 86 with activity referenced to α-quartz and rutile at P and T of interest. The zircon thermometer may now be applied to rocks without quartz and/or rutile, and the rutile thermometer applied to rocks without quartz, provided that $$a_{\text{SiO}_{2}}$$
and $$a_{\text{TiO}_{2}}$$
are estimated. Maximum uncertainties introduced to zircon and rutile thermometry by unconstrained $$a_{\text{SiO}_{2}}$$
and
$$a_{\text{TiO}_{2}}$$
can be quantitatively assessed and are ≈60 to 70°C at 750°C. A preliminary assessment of the dependence of the two thermometers on P predicts that an uncertainty of ±1 GPa introduces an additional uncertainty at 750°C of ≈50°C for the Ti-in-zircon thermometer and of ≈70 to 80°C for the Zr-in-rutile thermometer.
1,578 citations
Cites background or methods from "Crystallization thermometers for zi..."
...1 Calibration of the Zr-in-rutile thermometer based on data from experiments and natural samples in Watson et al. (2006) and on experimental results in Table 1....
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...quartz nor zirconia (and hence with undefined aSiO2Þ from Table 4 of Watson et al. (2006) were not used in the calibration....
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...titanate, (Zr,Ti)2O4, in these experiments and in Runs 57 (Watson et al. 2006) and 101 (Table 1) could be explained in two ways....
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...The Ti content of zircon coexisting with rutile or other Ti-rich phases and the Zr content of rutile coexisting with zircon or other Zr-rich phases has a strong dependence on temperature (T) (Degeling 2003; Troitzsch and Ellis 2004, 2005; Zack et al. 2004; Watson et al. 2006)....
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...(3), was quantitatively calibrated from data in Tables 2 and 3 of Watson et al. (2006) and the results of one new experiment (Table 1)....
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TL;DR: In this article, an in situ method for simultaneous measurement of U-Pb-Hf isotopes and trace element compositions of zircons using a quadrupole and multiple-collector inductively-coupledplasma mass spectrometer (Q-ICP-MS and MC-ICP-MS, respectively) connected to a single excimer laser-ablation system was described.
797 citations
Cites background from "Crystallization thermometers for zi..."
...The zircon thermometer also provides important information on the formation and evolution of the continental crust (Watson and Harrison, 2005; Watson et al., 2006)....
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TL;DR: In this paper, the Qinghu zircon is used as a reference for microbeam analysis of the U-Pb age and Hf and O isotope geochemistry.
Abstract: Zircon is the most useful mineral for studies in U-Pb geochronology and Hf and O isotope geochemistry. Matrix effect is a major problem of the microbeam techniques such as SIMS and LA-(MC)-ICPMS. Therefore, external standardization using well-characterized natural zircon standards is fundamental for accurate microbeam measurements. While the isotopic geochronology and geochemistry laboratories equipped with microbeam analytical facilities have been increasingly established in China during the past decade, applications of the isotopic microanalysis are still limited due to shortage of available standards. We report here the Qinghu zircon as a potential new working reference for microbeam analysis of zircon U-Pb age and O-Hf isotopes. This zircon was separated from the Qinghu quartz monzonite from the western Nanling Range, Southeast China. It is fairly homogeneous in U-Pb age and Hf and O isotopes in terms of large amounts of mircobeam measurements by LA-MC-ICPMS and SIMS at the scales of 20-60 mm. SIMS measurements yield consistent 206Pb/238U age within analytical uncertainties with that obtained by ID-TIMS. Precise determinations of O isotopes by IRMS and Hf isotopes by solution MC-ICPMS are in good agreement with the statistical mean of microbeam measurements. We recommend U-Pb age of = 159.5 ± 0.2 Ma (2SE), δ 18O = 5.4‰ ± 0.2‰ (2SD) and 176Hf/177Hf = 0.283002±0.000004 (2SD) as the best reference values for the Qinghu zircon.
601 citations
TL;DR: In this paper, the temperature dependence of substitution for silicon in the form of a new geothermometer was described, and the Ti contents of quartz (in ppm by weight) from 13 experiments increase exponentially with reciprocal T as described by.
Abstract: Titanium is one of many trace elements to substitute for silicon in the mineral quartz. Here, we describe the temperature dependence of that substitution, in the form of a new geothermometer. To calibrate the “TitaniQ” thermometer, we synthesized quartz in the presence of rutile and either aqueous fluid or hydrous silicate melt, at temperatures ranging from 600 to 1,000°C, at 1.0 GPa. The Ti contents of quartz (in ppm by weight) from 13 experiments increase exponentially with reciprocal T as described by:
$$ {\text{Log}}{\left( {X^{{{\text{qtz}}}}_{{{\text{Ti}}}} } \right)} = (5.69 \pm 0.02) - \frac{{(3765 \pm 24)}} {{T(K)}}. $$
Application of this thermometer is straightforward, typically requiring analysis of only one phase (quartz). This can be accomplished either by EPMA for crystallization temperatures above 600°C, or by SIMS for temperatures down to at least 400°. Resulting temperature estimates are very precise (usually better than ±5°C), potentially allowing detailed characterization of thermal histories within individual quartz grains. Although calibrated for quartz crystallized in the presence of rutile, the thermometer can also be applied to rutile-absent systems if TiO2 activity is constrained.
574 citations
References
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TL;DR: In this paper, the results of a study to develop natural zircon geochemical standards for calibrating the U-(Th)-Pb geochronometer and Hf isotopic analyses are reported.
Abstract: We report here the results of a study to develop natural zircon geochemical standards for calibrating the U-(Th)-Pb geochronometer and Hf isotopic analyses. Additional data were also collected for the major, minor and trace element contents of the three selected sample sets. A total of five large zircon grains (masses between 0.5 and 238 g) were selected for this study, representing three different suites of zircons with ages of 1065 Ma, 2.5 Ma and 0.9 Ma. Geochemical laboratories can obtain these materials by contacting Geostandards Newsletter.
4,845 citations
"Crystallization thermometers for zi..." refers methods in this paper
...Isotope standard 91500 During the course of this study, interlaboratory zircon standard 91500 (Wiedenbeck et al. 1995) was repeatedly analyzed for Ti using the IMP calibration based on zircons from experimental runs 57 and 59 and a Ti-free synthetic sample (see Ion microprobe (IMP): general…...
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...Isotope standard 91500 During the course of this study, interlaboratory zircon standard 91500 (Wiedenbeck et al. 1995) was repeatedly analyzed for Ti using the IMP calibration based on zircons from experimental runs 57 and 59 and a Ti-free synthetic sample (see Ion microprobe (IMP): general operating conditions)....
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TL;DR: The importance of zircon in crustal evolution studies is underscored by its predominant use in U-Th-Pb geochronology and investigations of the temporal evolution of both the crust and lithospheric mantle as discussed by the authors.
Abstract: Zircon is the main mineral in the majority of igneous and metamorphic rocks with Zr as an essential structural constituent. It is a host for significant fractions of the whole-rock abundance of U, Th, Hf, and the REE (Sawka 1988, Bea 1996, O’Hara et al. 2001). These elements are important geochemically as process indicators or parent isotopes for age determination. The importance of zircon in crustal evolution studies is underscored by its predominant use in U-Th-Pb geochronology and investigations of the temporal evolution of both the crust and lithospheric mantle. In the past decade an increasing interest in the composition of zircon, trace-elements in particular, has been motivated by the effort to better constrain in situ microprobe-acquired isotopic ages. Electron-beam compositional imaging and isotope-ratio measurement by in situ beam techniques—and the micrometer-scale spatial resolution that is possible—has revealed in many cases that single zircon crystals contain a record of multiple geologic events. Such events can either be zircon-consuming, alteration, or zircon-forming and may be separated in time by millions or billions of years. In many cases, calculated zircon isotopic ages do not coincide with ages of geologic events determined from other minerals or from whole-rock analysis. To interpret the geologic validity and significance of multiple ages, and ages unsupported by independent analysis of other isotopic systems, has been the impetus for most past investigations of zircon composition. Some recent compositional investigations of zircon have not been directly related to geochronology, but to the ability of zircon to influence or record petrogenetic processes in igneous and metamorphic systems.
Sedimentary rocks may also contain a significant fraction of zircon. Although authigenic zircon has been reported (Saxena 1966, Baruah et al. 1995, Hower et al. 1999), it appears to be very rare and may in fact be related to …
3,777 citations
"Crystallization thermometers for zi..." refers background in this paper
...The numerous impurities in zircon (e.g., Speer 1982; Belousova et al. 2002; Hoskin and Schaltegger 2003) suggest several possibilities for temperaturedependent uptake that could be calibrated for use as a thermometer....
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TL;DR: In this article, the saturation behavior of zircon in crustal anatectic melts as a function of both temperature and composition has been studied and a model of Zr solubility given by: In D Zr Zircon/melt = −3.80−[0.85(M−1)]+12900/T where T is the absolute temperature, and M is the cation ratio (Na + K + 2Ca)/(Al · Si).
3,330 citations
"Crystallization thermometers for zi..." refers background in this paper
...The BT phenocrysts have Ti distributions indicative of an abrupt increase in temperature at a late stage of growth (see Wark et al. 2004)....
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...As noted, we ignore the apparent late heating event recorded by Ti in quartz phenocrysts (Wark et al. 2004), because zircon would likely dissolve slightly during this event, and because the capacity of a magma to crystallize zircon at this late stage is exceedingly small due to the low solubility…...
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TL;DR: In this paper, a good approximation is obtained by relating τ to the slope of the cooling curve at the closure temperature of a geochronological system, which is defined as its temperature at the time corresponding to its apparent age.
Abstract: Closure temperature (Tc) of a geochronological system may be defined as its temperature at the time corresponding to its apparent age. For thermally activated diffusion (D=Doe−E/RT it is given by
$$T_c = R/[E ln (A \tau D_0 /a^2 )]$$
(i) in which R is the gas constant, E the activation energy, τ the time constant with which the diffusion coefficient D diminishes, a is a characteristic diffusion size, and A a numerical constant depending on geometry and decay constant of parent. The time constant τ is related to cooling rate by
$$\tau = R/(Ed T^{ - 1} /dt) = - RT^2 /(Ed T/dt).$$
(ii) Eq. (i) is exact only if T−1 increases linearly with time, but in practice a good approximation is obtained by relating τ to the slope of the cooling curve at Tc.
2,338 citations
"Crystallization thermometers for zi..." refers background or result in this paper
...Our overall data set (experiments + natural samples) is in good agreement with experimental results reported by Degeling (2003), who measured Zr contents of rutile crystals coexisting with zircon and quartz (or SiO2-rich melt) at 0.0001, 1.0 and 2.0 GPa and 1,000 to 1,500 C....
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...Exolution of baddeleyite from the rutile lattice (possibly followed by reaction with nearby quartz to form zircon) is another possible response of a high-Zr rutile grain to cooling (Degeling 2003; Bingen et al. 2001)....
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2,058 citations
"Crystallization thermometers for zi..." refers methods in this paper
...The crystallization temperature of 1,070 C reported by Lee and Rudnick (1999) is based on the two-pyroxene thermometer of Brey and Köhler (1990) and the CaO-inorthopyroxene thermometer, also of Brey and Köhler (1990)....
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