Ti-in-zircon thermometry: applications and limitations (original) (raw)

Abstract

The titanium concentrations of 484 zircons with U-Pb ages of ∼1 Ma to 4.4 Ga were measured by ion microprobe. Samples come from 45 different igneous rocks (365 zircons), as well as zircon megacrysts (84) from kimberlite, Early Archean detrital zircons (32), and zircon reference materials (3). Samples were chosen to represent a large range of igneous rock compositions. Most of the zircons contain less than 20 ppm Ti. Apparent temperatures for zircon crystallization were calculated using the Ti-in-zircon thermometer (Watson et al. 2006, Contrib Mineral Petrol 151:413–433) without making corrections for reduced oxide activities (e.g., TiO2 or SiO2), or variable pressure. Average apparent Ti-in-zircon temperatures range from 500° to 850°C, and are lower than either zircon saturation temperatures (for granitic rocks) or predicted crystallization temperatures of evolved melts (∼15% melt residue for mafic rocks). Temperatures average: 653 ± 124°C (2 standard deviations, 60 zircons) for felsic to intermediate igneous rocks, 758 ± 111°C (261 zircons) for mafic rocks, and 758 ± 98°C (84 zircons) for mantle megacrysts from kimberlite. Individually, the effects of reduced \( a_{{\rm TiO}_{2}}\) or \( a_{{\rm SiO}_{2}}\), variable pressure, deviations from Henry’s Law, and subsolidus Ti exchange are insufficient to explain the seemingly low temperatures for zircon crystallization in igneous rocks. MELTs calculations show that mafic magmas can evolve to hydrous melts with significantly lower crystallization temperature for the last 10–15% melt residue than that of the main rock. While some magmatic zircons surely form in such late hydrous melts, low apparent temperatures are found in zircons that are included within phenocrysts or glass showing that those zircons are not from evolved residue melts. Intracrystalline variability in Ti concentration, in excess of analytical precision, is observed for nearly all zircons that were analyzed more than once. However, there is no systematic change in Ti content from core to rim, or correlation with zoning, age, U content, Th/U ratio, or concordance in U-Pb age. Thus, it is likely that other variables, in addition to temperature and \( a_{{\rm TiO}_{2}}\), are important in controlling the Ti content of zircon. The Ti contents of igneous zircons from different rock types worldwide overlap significantly. However, on a more restricted regional scale, apparent Ti-in-zircon temperatures correlate with whole-rock SiO2 and HfO2 for plutonic rocks of the Sierra Nevada batholith, averaging 750°C at 50 wt.% SiO2 and 600°C at 75 wt.%. Among felsic plutons in the Sierra, peraluminous granites average 610 ± 88°C, while metaluminous rocks average 694 ± 94°C. Detrital zircons from the Jack Hills, Western Australia with ages from 4.4 to 4.0 Ga have apparent temperatures of 717 ± 108°C, which are intermediate between values for felsic rocks and those for mafic rocks. Although some mafic zircons have higher Ti content, values for Early Archean detrital zircons from a proposed granitic provenance are similar to zircons from many mafic rocks, including anorthosites from the Adirondack Mts (709 ± 76°C). Furthermore, the Jack Hills zircon apparent Ti-temperatures are significantly higher than measured values for peraluminous granites (610 ± 88°C). Thus the Ti concentration in detrital zircons and apparent Ti-in-zircon temperatures are not sufficient to independently identify parent melt composition.

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Acknowledgments

We thank Brian Hess for preparation of zircon mounts, and Ilya Bindeman, Mike Hamilton, Liz King, and Robert Zartman for providing some of the zircon separates. Lance Black, Chris Foudoulis and Keith Sircombe provided a rock sample of the Temora gabbroic diorite. Bruce Watson provided a synthetic Ti-rich zircon for standardization of SIMS data. John Craven and Richard Hinton assisted in analysis of Ti in Jack Hills zircons. Doug Morrison and Louise Edwards assisted with MELTs. Constructive reviews by John Eiler and an anonymous referee led to improvement of this manuscript and are gratefully appreciated. This work was supported by the National Science Foundation (EAR-0509639), Department of Energy (93ER14389) and NASA Astrobiology Institute (NO7-5489). Wisc-SIMS, the UW Ion Microprobe Lab, is supported by the University of Wisconsin, Madison and the National Science Foundation (EAR-0319230 and EAR-0516725).

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Author notes

  1. Bin Fu
    Present address: School of Earth Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia
  2. F. Zeb Page
    Present address: Geology Department, Oberlin College, Oberlin, OH, 44074, USA

Authors and Affiliations

  1. Department of Geology and Geophysics, University of Wisconsin, Madison, WI, 53706, USA
    Bin Fu, F. Zeb Page, John Fournelle, Noriko T. Kita & John W. Valley
  2. Department of Geology, University of Puerto Rico, Mayagüez, PR, 00681-9017, USA
    Aaron J. Cavosie
  3. Geology Department, Pomona College, Claremont, CA, 91711, USA
    Jade Star Lackey
  4. Department of Applied Geology, Curtin University of Technology, Perth, WA, 6845, Australia
    Simon A. Wilde

Authors

  1. Bin Fu
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  2. F. Zeb Page
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  3. Aaron J. Cavosie
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  4. John Fournelle
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  5. Noriko T. Kita
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  6. Jade Star Lackey
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  7. Simon A. Wilde
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  8. John W. Valley
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Corresponding author

Correspondence toJohn W. Valley.

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Communicated by T. L. Grove.

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Appendix : Sample description

Appendix : Sample description

In total, 365 zircons from 45 igneous rock samples including localities in Nain, Adirondack Mountains, Sierra Nevada, Temora, and three well-known zircon standards were analyzed in this study. Detrital zircons from the Jack Hills and zircon xenocrysts from kimberlite were also studied.

Of seven anorthosite-leuconorite samples analyzed for titanium in zircon, four were collected from the Nain Anorthosite Complex, Labrador (Hamilton et al. 1994; Clechenko et al. 2003); three from the Woolen Mill locality, northeastern Marcy anorthosite massif, Adirondack Highlands, New York (McLelland et al. 2004). U-Pb ion microprobe ages of Nain anorthosite are 1,319–1,305 Ma (Hamilton et al. 1994). The Adirondack Mountains AMCG suite (anorthosite-mangerite-charnockite-granite) was intruded at 1,155 ± 10 Ma (McLelland et al. 2004), which establishes a coeval (but bimodal) origin for the AMCG suite. The Adirondack Mountains anorthosite was metamorphosed at granulite-facies conditions at about 1,050 Ma (McLelland et al. 2004).

Three samples of gabbro and fine-grained gabbroic dikes in serpentinite were collected from drill core (ODP Leg 153), located at the Mid-Atlantic Ridge near the Kane Transform (MARK area) (Cavosie et al. 2005a). Both δ18O and REE distribution pattern indicate that zircons in serpentinite and gabbro are of magmatic origin.

Ten other gabbro samples were investigated from a variety of localities. Metagabbros include the Archean Pike Lake gabbro in Sturgeon Lake and the Kakagi Lake volcanics gabbro pegmatite, Wabigoon Subprovince (Davis et al. 1980, 1985; Davis and Edwards 1982; Davis and Trowell 1982; King et al. 1998); and Paleoproterozoic metagabbro sills at Prairie Creek and Bogus Jim Creek, Central Black Hills, Pennington County in South Dakota (Redden et al. 1990); Mesoproterozoic Woolen Mill metamorphosed ferrogabbro, northeastern Marcy massif, Adirondack Highlands, New York (McLelland et al. 2004); Neoproterozoic Palermo monzogabbro from the Serra do Mar Alkaline-Peralkaline Suite, Brazil (Valley et al. 2005); Cretaceous gabbro-norite in Western Sierra Nevada (Lackey 2005) and metagabbro-metadiorite from the Mount Stuart Batholith, Big Jim Mountain, Washington (Tabor et al. 1987). It is noteworthy that only the granulite-facies Woolen Mill metagabbro also yielded a metamorphic age, ∼100 m.y. younger than the intrusive age, by ion microprobe U-Pb dating (McLelland et al. 2004), while the other metagabbros (or enclosed granophyre, see below) from both the Black Hills and Big Jim Mountain record only intrusive ages (Tabor et al. 1987; Redden et al. 1990).

Six other samples from mafic intrusions include a felsic segregation in gabbro from the Outer Eucrite Series in the Cullins and an alkaline segregation (feldspathic pegmatite) within the margin of the layered mafic/ultramafic complex, Isle of Skye, Scotland (Hamilton et al. 1998; Monani and Valley 2001); a trondhjemite pod within the Silurian Preston gabbro, an unmetamorphosed, stock-like intrusion in Griswold, New London County, Connecticut (Zartman and Naylor 1984); Mesoproterozoic greenish gray, medium-grained granophyre phases within a gabbro sill at the Crossport quarry, Eastport, Boundary County, Idaho (Zartman et al. 1982); and Paleoproterozoic coarse-grained granophyre in the upper part of the Nemo sill (i.e., 1,000-m-thick, gravity differentiated Blue Draw metagabbro), Black Hills, Lawrence County, South Dakota (Redden et al. 1990).

Eleven granitic samples were collected from the central part of the Sierra Nevada batholith, California (Lackey 2005; Lackey et al. 2005, 2006).

Five zircon samples were collected from volcanic rocks: basanite at Chantaburi, Thailand (Lee Silver pers. comm. 2000), and rhyolites from Yellowstone Plateau: Lava Creek Tuff, Mesa Falls Tuff and Huckleberry Ridge Tuff A and C (Bindeman and Valley 2001; Bindeman et al. 2001). One pegmatite sample was collected from the Central Adirondack Highlands, New York which yielded an ion microprobe U-Pb age of ∼900 Ma (Valley et al. 2005).

Ti analyses were made on 42 detrital zircons obtained from quartzite and conglomerate from the Jack Hills, Western Australia with U/Pb ages >3,900 Ma. Additional information on these grains, including field locations, CL images, U/Pb and δ18O, REE data can be found in Cavosie et al. (2004, 2005b, 2006).

In addition, commonly used zircon standards for stable or radiogenic isotopes were assessed for Ti concentration and homogeneity. Zircon CZ3 is a detrital crystal from Sri Lanka (Pidgeon et al. 1994). Zircon 91500 is a megacryst from a titanite-bearing syenitic pegmatite in Ontario (Wiedenbeck et al. 2004). KIM-5 is a megacryst in kimberlite from the Kimberley Pool, South Africa (Valley et al. 1998; Valley 2003; Cavosie et al. 2005b). Temora-1 and Temora-2 are gabbroic diorites from the Lachlan Fold Belt, SE Australia (Black et al. 2004).

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Fu, B., Page, F.Z., Cavosie, A.J. et al. Ti-in-zircon thermometry: applications and limitations.Contrib Mineral Petrol 156, 197–215 (2008). https://doi.org/10.1007/s00410-008-0281-5

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