Pb/Pb geochronology, petrography and chemistry of Zr-rich accessory minerals (zirconolite, tranquillityite and baddeleyite) in mare basalt 10047

Rasmussen, Birger; Fletcher, Ian R.; Muhling, Janet R.

doi:10.1016/j.gca.2008.09.010

Cited by 53 publications

(42 citation statements)

References 46 publications

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“…The method for the analysis of titanite follows that given in Williams (1996) and Rasmussen et al (2008). Data reduction and image manipulation used software from Moran Scientific.…”

Section: Empa-wdsmentioning

confidence: 99%

GRENVILLE SKARN TITANITE: POTENTIAL REFERENCE MATERIAL FOR SIMS U-Th-Pb ANALYSIS

Kennedy¹,

Kamo²,

Nasdala³

et al. 2010

The Canadian Mineralogist

132

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We have investigated the homogeneity, chemical composition, structure, degree of radiation damage, and post-formation evolution of titanite crystals from skarns of the Grenville Province of the Canadian Shield using SHRIMP, TIMS, Raman and PL spectroscopy, EBSD, and EPMA-WDS. These results are used to assess the potential of the titanite as Reference Material (RM) for micro-analytical U-Th-Pb age dating. The SHRIMP data show that these megacrysts (5-31g) have concordant U-Pb isotope systematics, 60 to 500 ppm U, 120 to 1200 ppm Th , 206 Pb/ 204 Pb between 500 and 2500, ages of ~1 Ga, and excellent homogeneity at the scale of the analytical volume of the ion probe. The ID-TIMS titanite data for OLT1, OLT2 and TCB show that these crystals are essentially concordant. Data for OLT1 and OLT2 show slight scatter (i.e., in excess of that expected from the uncertainty in an individual analysis). For OLT1, one of seven analyses shows Pb loss or, possibly, a younger period of growth. Crystals OLT1 and OLT2 have respective TIMS concordia ages of 1014.8 ± 2.0 Ma (2s, n = 6, MSWD = 1.8) and 998.0 ± 4.5 Ma (2s, n = 3, MSWD = 3.3) for domains that have not lost Pb. The TIMS analyses of TCB are tightly clustered and give a concordia age of 1018.1 ± 1.7 Ma (2s, n = 4, MSWD = 0.92). Raman and PL spectra show a low to moderate degree of accumulated radiation-induced damage in the Grenville Skarn Titanite crystals and uniform internal distributions of this damage. The EDSB contrast images indicate little or no crystallographic misorientation. The EMPA-WDS data show that the outer 50-100 mm of the OLT1 and TCB crystals are enriched in Al and F, and depleted in Fe and Nb, when compared with the interior. In spite of the variation in composition and degree of radiation damage amongst samples, there are no identifiable matrix effects in our SHRIMP data. Some Grenville skarn titanite (GST) crystals have potential as RM for micro-analytical U-Th-Pb age dating. Crystal TCB has excellent homogeneity of U-Th-Pb isotopic composition. Crystals OLT1 and OLT2 have minor TIMS age heterogeneity. However, this heterogeneity is smaller than that of the Khan titanite, our current in-house titanite standard. Careful selection of analysis areas during SIMS, and of chips for TIMS analysis, allows high-quality isotopic data to be obtained from these large crystals of titanite.

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“…The method for the analysis of titanite follows that given in Williams (1996) and Rasmussen et al (2008). Data reduction and image manipulation used software from Moran Scientific.…”

Section: Empa-wdsmentioning

confidence: 99%

GRENVILLE SKARN TITANITE: POTENTIAL REFERENCE MATERIAL FOR SIMS U-Th-Pb ANALYSIS

Kennedy¹,

Kamo²,

Nasdala³

et al. 2010

The Canadian Mineralogist

132

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“…Therefore, a reliable dating method is crucial to understand thermal history recorded in lunar meteorites and possible pairing among different samples. In lunar basalts, Zr-rich minerals, such as zirconolite, baddeleyite, and tranquillityite, usually occur as late-stage magmatic phases [4] and therefore their ages could represent crystallization ages of mare basalts. Compared to those silicate minerals that are used for Sm-Nd and Rb-Sr isochron and Ar/Ar dating, Zr-rich minerals (e.g., zircon, baddeleyite) have more stable crystal structures and their ages could be closer to pristine igneous crystallization ages.…”

Section: Introductionmentioning

confidence: 99%

SIMS Pb/Pb dating of Zr-rich minerals in lunar meteorites Miller Range 05035 and LaPaz Icefield 02224: Implications for the petrogenesis of mare basalt

Zhang

Hsu

et al. 2010

Sci. China Earth Sci.

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Miller Range (MIL) 05035 and LaPaz Icefield (LAP) 02224 are unbrecciated lunar basalt meteorites. In this report, we studied their petrography and mineralogy and made in situ uranogenic Pb/Pb dating of Zr-rich minerals. Petrography and mineralogy of these two lunar meteorites are consistent with previous investigations. The zirconolite Pb/Pb age of MIL 05035 is 3851±8 Ma (2σ), in excellent agreement with previous reports. This age suggests that MIL 05035 could be paired with Asuka 881757, a low-Ti mare basalt meteorite. The magmatic event related to MIL 05035 was probably due to the late heavy impact bombardment on the moon around 3.9 Ga. One baddeleyite grain in LAP 02224 shows a large variation of Pb/Pb age, from 3109±29 to 3547±21 Ma (2σ), much older than the whole-rock age of the same meteorite (~3.02±0.03 Ga). The other baddeleyite grain in LAP 02224 has an age of 3005±17 Ma (2σ). The result indicates that the minimum crystallization age of LAP 02224 is ~3.55 Ga and the younger ages could reflect late thermal disturbance on U-Pb system. Pb/Pb dating, SIMS, zirconolite and baddeleyite, lunar meteorite, low-Ti mare basalt Citation: Zhang A C, Hsu W B, Li Q L, et al. SIMS Pb/Pb dating of Zr-rich minerals in lunar meteorites Miller Range 05035 and LaPaz Icefield 02224: Implications for the petrogenesis of mare basalt.

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“…These published results indicate a profound resetting of the system during the 3.9 Ga cataclysm (Grange et al 2009;Nemchin et al 2009b). Rasmussen et al (2008) demonstrated that at least some lunar basalts contain a suite of Zr minerals, such as zirconolite, tranquillityite, and baddeleyite. All these minerals also concentrate U in the quantities sufficient for a precise U-Pb dating.…”

Section: U-pb Ages Of Lunar Samplesmentioning

confidence: 72%

Uranium–Lead, Extraterrestrial, Planetary Materials

Nemchin

2013

Encyclopedia of Scientific Dating Methods

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Pb/Pb geochronology, petrography and chemistry of Zr-rich accessory minerals (zirconolite, tranquillityite and baddeleyite) in mare basalt 10047

Cited by 53 publications

References 46 publications

GRENVILLE SKARN TITANITE: POTENTIAL REFERENCE MATERIAL FOR SIMS U-Th-Pb ANALYSIS

GRENVILLE SKARN TITANITE: POTENTIAL REFERENCE MATERIAL FOR SIMS U-Th-Pb ANALYSIS

SIMS Pb/Pb dating of Zr-rich minerals in lunar meteorites Miller Range 05035 and LaPaz Icefield 02224: Implications for the petrogenesis of mare basalt

Uranium–Lead, Extraterrestrial, Planetary Materials

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