The mineralogy of the Yaringie Hill meteorite —A new H5 chondrite from South Australia Item Type Article; text Authors Tappert, R.; Foden, J.; Pring, A. Citation Tappert, R., Foden, J., & Pring, A. (2009). The mineralogy of the Yaringie Hill meteorite—A new H5 chondrite from South Australia. Meteoritics & Planetary Science, 44(11), 1687-1693. DOI 10.1111/j.1945-5100.2009.tb01199.x Publisher The Meteoritical Society Journal Meteoritics & Planetary Science Rights Copyright © The Meteoritical Society Download date 03/10/2021 21:14:20 Item License http://rightsstatements.org/vocab/InC/1.0/ Version Final published version Link to Item http://hdl.handle.net/10150/656634 Meteoritics & Planetary Science 44, Nr 11, 1687–1693 (2009) Abstract available online at http://meteoritics.org The mineralogy of the Yaringie Hill meteorite—A new H5 chondrite from South Australia Ralf TAPPERT1*, John FODEN1, and Allan PRING2 1University of Adelaide, Geology and Geophysics, School of Earth and Environmental Sciences, Adelaide, South Australia 5005, Australia 2South Australian Museum, Science Centre, Adelaide, South Australia 5000, Australia *Corresponding author. E-mail: [email protected] (Received 26 May 2009; revision accepted 24 July 2009) Abstract–The Yaringie Hill meteorite is a new H5 ordinary chondrite found in the Gawler Ranges, South Australia. The meteorite, which shows only minor signs of terrestrial weathering, is predominantly composed of olivine (Fa17.2), orthopyroxene (Fs15.1Wo1.1), and three distinct phases of nickeliferous iron metal (kamacite, taenite, tetrataenite). Other minerals include troilite, plagioclase (Ab81An16Or3), clinopyroxene (En52Wo42Fs6), chlorapatite, merrillite, ilmenite, and native copper. Three types of spinel with distinctive textures (coarse, skeletal aggregates, rounded aggregates) and with compositions close to the join MgAl2O4-FeCr2O4 are also present. Chondrules within the Yaringie Hill meteorite, which often have poorly defined boundaries, are placed in a recrystallized matrix. Shock indicators suggest that the meteorite experienced only weak shock metamorphism (S3). INTRODUCTION nickeliferous iron metal. Minor phases are plagioclase, troilite, and clinopyroxene. Accessory minerals include The Yaringie Hill meteorite was found by entomologist Dr. chlorapatite, merrillite, ilmenite, spinel, and native copper. Peter Hudson, during a fauna survey of the South Australian Chondrules composed of olivine, pyroxene or both minerals Museum on October 18, 2006, in the Gawler Ranges, South occur throughout the meteorite. The chondrules include types Australia (32°04.972′S, 135°38.991′E; Fig. 1). The discovery with porphyritic, non-porphyritic (radial pyroxene, barred site is located about 15 km east of the eastern shore of Lake olivine, cryptocrystalline), and granular textures (see Gooding Acraman, which coincidentally marks the location of a large and Keil 1981). Chondrule sizes range from ~300 µm to a Neoproterozoic meteorite impact (Williams 1986). The maximum of ~4 mm. The largest chondrule consisted of Yaringie Hill meteorite is the first meteorite found within radially aligned barred olivine with interstitial feldspar the Gawler Ranges; however, nine other meteorites were (Fig. 3). The boundaries of the chondrules are often poorly recovered from the adjacent Eyre Peninsula to the south defined, and the interchondrule matrix is recrystallized. (Fig. 1). Weathering features of the Yaringie Hill meteorite are restricted to minor oxide rims around most of the metal and PHYSICAL DESCRIPTION AND PETROGRAPHY troilite grains, and staining of the adjacent silicate minerals. These weathering characteristics are consistent with stage W1 The Yaringie Hill meteorite was recovered as a single on the weathering scale devised by Wlotzka (1993). Meteorite mass and was entirely covered by a thin brownish-black finds with similar weathering characteristics, from regions fusion crust. The stone is roughly tetrahedral shaped with two with arid climate conditions comparable to South Australia, roughly planner faces at right angles to each other; the other were found to have terrestrial ages of less than 5000 years sides of the tetrahedron are less regular. The approximate (Jull et al. 1990; Wlotzka 1993). dimensions of the meteorite are 18 × 13 × 12 cm, and the original weight was 5.75 kg. A conspicuous feature of the MINERALOGY meteorite is a thin (~0.5 mm) vein of metal that crosscuts the entire specimen (Fig. 2). The interior of the meteorite is The composition of the mineral phases were analyzed light colored, with some patchy brown oxidized areas (Fig. 2). with a CAMECA SX-51 electron microprobe at the The Yaringie Hill meteorite is a recrystallized chondrite, University of Adelaide, using a 15 kV acceleration voltage predominantly composed of olivine, orthopyroxene, and and a beam current of 20 nA. Counting times for each 1687 © The Meteoritical Society, 2009. Printed in USA. 1688 R. Tappert et al. Fig 1. Map of the Eyre Peninsula and the Gawler Ranges (South Australia) with the location of the sites of the Yaringie Hill and other meteorite finds. element ranged from 40 to 60 seconds (including Clinopyroxene is a rare component of the Yaringie Hill background counts). Representative mineral analyses are meteorite. It occasionally occurs as distinct grains of up to presented in Table 1. 50 µm, but more commonly forms thin overgrowths (≤20 µm) Olivine occurs both within chondrules and as of larger orthopyroxene crystals. The average composition of granoblastic matrix grains. The average fayalite component clinopyroxene is En51.9, Wo42.0, Fs6.1. Minor elements include σ = ) % % of the olivines is Fa17.2 (range: Fa16.6–Fa19.4, 1 : 0.45, n 54 titanium (0.47 wt TiO2), aluminium (1.65 wt Al2O3), and % (Fig. 4). chromium (1.12 wt Cr2O3) (Table 1). Like olivine, orthopyroxene also occurs within Minerals belonging to the spinel group are chondrules and as granoblastic matrix grains. compositionally variable and show a range of textures. The Orthopyroxenes have an average ferrosilite content of Fs15.1 maximum size of all types of spinel group minerals is around σ = µ (range: Fs14.5–Fs15.9, 1 : 0.34, n 28), and an average 200 m. Most abundant are coarse Cr-spinels (Ramdohr σ wollastonite content of Wo1.1 (range: Wo0.6–Wo2.9, 1 : 0.53) 1973), which are rather uniform in composition (Fig. 6, Table (Fig. 4). 1), and commonly occur in association or as inclusion in Fe- Despite the fact that plagioclase feldspar comprises a Ni metal or troilite (Fig. 5B). Aggregate spinels, which often significant part of the matrix and of the interstitial phases of have distinctive skeletal crystal shapes (skeletal aggregate chondrules within the Yaringie Hill meteorite (Fig. 5A), spinels, Fig. 5C) are more variable in composition but have discrete and inclusion-free crystals of sizes >10 µm are lower chromium and iron and higher aluminium and uncommon. Most of the very fine-grained to magnesium contents than coarse Cr-spinels (Fig. 6, Table 1). cryptocrystalline feldspar forms intergrowths with other The skeletal aggregate spinels are commonly rimmed by fine-grained minerals. Compositionally the plagioclase plagioclase (Fig. 5C). Other spinels, which are also associated feldspar of the Yaringie Hill meteorite is oligoclase with an with plagioclase, form conspicuous rounded aggregates approximate average composition Ab81An16Or3 (Table 1). (rounded aggregate spinels, Fig. 5D). These spinels have even This feldspar composition falls into the range which is typical lower chromium and iron and higher aluminium and for H chondrites (Van Schmus and Ribbe 1968). magnesium contents. Rubin (2003) suggested that the The mineralogy of the Yaringie Hill meteorite—A new H5 chondrite 1689 Fig. 2. Photograph of the Yaringie Hill meteorite after cutting. The prominent metal vein (white arrow) and a single large chondrule (black arrow) are visible on the cut surface. Scale bar is in centimeters. Fig. 3. Photomicrograph (crossed polars) of a large chondrule (Ø ~4 mm) from the Yaringie Hill meteorite. The chondrule consists of radially aligned barred olivine, rimmed by coarse recrystallized matrix. 1690 R. Tappert et al. Table 1. Representative compositions of minerals from the Yaringie Hill meteorite (analyses given in wt%). Orthopy- Spinel Spinel Olivine roxene Clinopy- Spinel (skeletal (rounded Mineral (n = 54) (n = 28) roxene Feldspar Apatite Merrillite Ilmenite (coarse) agg.) agg.) ≤ ≤ ≤ ≤ P2O5 0.04 0.04 0.04 0.04 41.2 46.4 – – – – SiO2 38.7 56.1 53.6 66.1 0.24 0.11 0.18 0.09 0.12 0.15 ≤ ≤ ≤ TiO2 0.06 0.13 0.47 0.04 0.04 0.04 54.8 1.47 1.09 0.21 ≤ ≤ ≤ ≤ Al2O3 0.04 0.18 1.65 22.7 0.04 0.04 0.04 6.11 14.7 40.9 ≤ V2O3 –– – – –– 0.04 0.92 0.47 0.29 ≤ ≤ ≤ ≤ ≤ Cr2O3 0.04 0.14 1.12 0.04 0.04 0.04 0.04 58.4 51.0 26.6 MgO 44.0 31.9 18.2 0.43 0.12 3.58 4.76 2.70 6.37 12.3 CaO ≤0.04 0.56 20.5 2.97 53.5 47.4 0.07 ≤0.04 0.07 0.07 MnO 0.46 0.49 0.27 ≤0.04 ≤0.04 ≤0.04 3.62 0.84 0.68 0.31 FeO 16.3 10.3 3.81 0.48 0.29 0.48 37.0 28.8 25.8 18.8 NiO ≤0.04 ≤0.04 ≤0.04 ≤0.04 ≤0.04 ≤0.04 0.13 ≤0.04 ≤0.04 ≤0.04 ZnO – – – – – – 0.05 0.47 0.43 0.63 ≤ ≤ Na2O 0.04 0.04 0.59 8.31 0.32 2.73 – – – – ≤ ≤ ≤ ≤ K2O 0.04 0.04 0.04 0.48 0.04 0.05 – – – – F – – – – 0.46 0.06 – – – – Cl – – – – 4.38 ≤0.04 – – – – Total 99.5 99.8 100.3 101.5 100.4 100.8 100.6 99.8 100.9 100.2 P 0.00 0.00 0.00 0.00 13.4 14.0 – – – – Si 2.95 3.96 3.89 2.86 0.09 0.04 0.02 0.01 0.01 0.01 Ti 0.00 0.01 0.03 0.00 0.00 0.00 3.98 0.12 0.08 0.01 Al 0.00 0.02 0.14 1.16 0.00 0.00 0.00 0.77 1.72 4.14 V – – – – – – 0.00 0.08 0.04 0.02 Cr 0.00 0.01 0.06 0.00 0.00 0.00 0.00 4.91 4.00 1.81 Mg 5.00 3.35 1.97 0.03 0.07 1.90 0.69 0.43 0.94 1.57 Ca 0.00 0.04 1.60 0.14 22.0 18.0 0.01 0.00 0.01 0.01 Mn 0.03 0.03 0.02 0.00 0.01 0.01 0.30 0.08 0.06 0.02 Fe2+ 1.04 0.60 0.23 0.02 0.09 0.14 2.99 2.57 2.14 1.35 Ni 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Zn – – – – – – 0.00 0.04 0.03 0.04 Na 0.00 0.00 0.08 0.70 0.24 1.88 – – – – K 0.00 0.00 0.00 0.03 0.00 0.02 – – – – Cation tot.