Geochemistry of pyroxene inclusions from the Warrumbungle Volcano, New South Wales, Australia

Ghorbani, Mohammad Reza; Middlemost, Eric A. K.

doi:10.2138/am-2000-1003

Cited by 18 publications

(13 citation statements)

References 54 publications

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“…Two groups of clinopyroxenes have geochemical features characteristic of Cr-diopsides (e.g., higher Cr 2 O 3 , MgO and lower TiO 2 , FeO than Al-augites; Irving, 1980;Griffin et al, 1984;Ghorbani and Middlemost, 2000): (a) clinopyroxene that (1996). C ϭ core; R ϭ rim of crystal.…”

Section: Group C: Lherzolite Xenoliths and Xenocrystsmentioning

confidence: 99%

Structure of the Ethiopian lithosphere: Xenolith evidence in the Main Ethiopian Rift

Rooney

Furman

Yirgu

et al. 2005

Geochimica et Cosmochimica Acta

109

130

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Section: Group C: Lherzolite Xenoliths and Xenocrystsmentioning

confidence: 99%

Structure of the Ethiopian lithosphere: Xenolith evidence in the Main Ethiopian Rift

Rooney

Furman

Yirgu

et al. 2005

Geochimica et Cosmochimica Acta

109

130

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“…Potassium-rich clinopyroxenes (KCpx) occur as inclusions in diamonds, in eclogitic and peridotitic xenoliths from kimberlites and lamproites (Bishop et al 1978;Harlow and Veblen 1991;Reid et al 1976;Jaques et al 1990), as rare megacrysts in some K-rich volcanics (Ghorbani and Middlemost 2000), and as inclusions in garnets of garnet-clinopyroxene rocks from the Kokchetav Ultra High Pressure (UHP) Complex, Northern Kazakhstan (e.g., Sobolev and Shatsky 1990). The concentration of K 2 O in natural clinopyroxenes (for example, inclusions in diamonds) does not usually exceed 1.7 wt% (Harlow and Veblen 1991).…”

Section: Introductionmentioning

confidence: 99%

Compressibility of synthetic potassium-rich clinopyroxene: In-situ high-pressure single-crystal X-ray study

Bindi

Downs

Harlow

et al. 2006

American Mineralogist

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The crystal structure of a synthetic potassium-rich clinopyroxene, (Ca 0.88 K 0.12 )(Mg 0.83 Al 0.17 )(Si 1.98 Al 0.02 )O 6 , was studied using high-pressure single-crystal X-ray diffraction methods. A four-pin diamond anvil cell with 4:1 methanol:ethanol pressure medium was used to achieve pressures to 9.72 GPa. Unit-cell data were measured at 17 pressures, and intensity data were collected at 6 pressures. Fitting the P-V data to the third-order Birch-Murnaghan equation of state yields V 0 = 435.49(3) Å 3 , K 0 = 129(1) GPa, K' = 2.7(3). Anisotropic compression was observed with unit strain axial ratios of 1:1.94:1.90. Unit-cell parameters decrease gradually as a function of pressure with axial compressibilities β b > β c ~ β a . They match those found for kosmochlor but are stiffer than those observed for synthetic diopside and hedenbergite. Compressibilities of the bond distances within the M2, M1, and T polyhedra show signifi cant anisotropy. The incorporation of K into the clinopyroxene structure has little effect on its compressibility, although the concomitant substitution of Al in M1 from the K-Jd component reduces its compressibility. The K atom is softer than the M2 polyhedron and thus shrinks enough at high pressure to fi t into the pyroxene structure.

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“…The gabbro contains two types of magnetite, individual grains and pyroxene-hosted exsolutions. The orientation of the exsolutions in pyroxenes is crystallographically controlled, typically with two groups of exsolutions subparallel to the [001] and [100] directions of the pyroxene (Bown & Gay, 1959;Feinberg et al, 2004;Fleet et al, 1980), leading to an oblate ferromagnetic fabric with the minimum susceptibility parallel to the clinopyroxene [010] axis (Biedermann et al, 2015;Hirt & Biedermann, 2019).…”

Section: -D: In-plane Anisotropy Of An Oxide Gabbromentioning

confidence: 99%

FinIrrSDA: A 3‐D Model for Magnetic Shape and Distribution Anisotropy of Finite Irregular Arrangements of Particles With Different Sizes, Geometries, and Orientations

Biedermann

2020

JGR Solid Earth

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The magnetic anisotropy carried by strongly magnetic particles such as magnetite or ferrofluid-filled pores is generally composed of shape anisotropy and distribution anisotropy. Their relative importance in rocks depends on numerous factors and has been discussed controversially. A major challenge in estimating their contributions so far has been that models for distribution anisotropy only exist for regular arrangements of equal particles along lines or in planes. Because magnetite grains or pores in rocks display wide ranges of orientations, shapes, and sizes in generally irregular arrangements, new models are needed to describe distribution anisotropy for more realistic grain and pore assemblies. The model presented in this study, FinIrrSDA, calculates shape and distribution anisotropy for finite irregular assemblies of unequal particles with different orientations. Input parameters are provided as a table with x, y, and z coordinates of the particle centers and the lengths and orientations of the major, intermediate, and minor axes of best fit ellipsoids. The model output consists of two susceptibility tensors: (1) the shape anisotropy tensor and (2) the total tensor combining shape and distribution anisotropies. FinIrrSDA can be applied to a wide range of input data sets, including known structures of synthetic samples, particle analyses from tomography data, and, subject to certain assumptions, 2-D images. The model will hopefully increase our understanding of the interplay between shape and distribution anisotropies in natural rocks and facilitate future interpretations of both the magnetic anisotropy carried by magnetite grains and magnetic pore fabrics. Plain Language Summary Models are helpful when we aim at understanding and interpreting measured data, provided that they are applicable to reality. This paper presents a new model to predict magnetic properties and their directional dependence (anisotropy) of strongly magnetic particles (e.g., magnetite or pores filled with strongly magnetic fluid) in rock samples. This model is applicable to irregular assemblies of particles of various sizes and orientations and thus helps close the gap between existing models and reality. The model helps us understand the sources of magnetic anisotropy and thus makes magnetic anisotropy an even more valuable tool to investigate preferred alignment of magnetite or pores in rocks.

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Geochemistry of pyroxene inclusions from the Warrumbungle Volcano, New South Wales, Australia

Cited by 18 publications

References 54 publications

Structure of the Ethiopian lithosphere: Xenolith evidence in the Main Ethiopian Rift

Structure of the Ethiopian lithosphere: Xenolith evidence in the Main Ethiopian Rift

Compressibility of synthetic potassium-rich clinopyroxene: In-situ high-pressure single-crystal X-ray study

FinIrrSDA: A 3‐D Model for Magnetic Shape and Distribution Anisotropy of Finite Irregular Arrangements of Particles With Different Sizes, Geometries, and Orientations

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