inverted pigeonite thin section

McDermott) Introduction to the main analytical methods for geochemical analysis of igneous rocks. Examinations of thin sections from the different dyke types make it clear that all dykes examined underwent successive ... and pyroxenes with exsolution structures: inverted pigeonite and augite (Figure 18.11B). This fused crust is about 0.2 mm. 2. They usually occur interstitially between olivine an d pyroxenes. Methods: A petrographic thin section and a polished chip of A 09545 were used. ZAF 4 corrections were applied to the analyses. 2.5 mm plag opx h) plag opx cpx 2.5 mm g) 62 Fig. Inverted Pigeonite. Microscope. was done because the thin section of Y-791538 was lost during thinning and because pigeonite was not present in the RKPA80239 thin section. A thin section-scale backscattered electron (BSE) image and X-ray elemental maps were obtained by using a JEOL JXA-8900 electron probe microanalyzer (EPMA) at Waseda University. TABLE OF CONTENTS: Some Fundamental Properties of Minerals in Thin Section: Relief ; Cleavage ; Absorption and Pleochroism ; Extinction Angle ; Twinning ; Interference Colours of a Quartz Wedge Microprobe analyses were determined using a SEM Cambridge S 360 electron microprobe equipped with EDS Link Analytical QX 2000. 1. Image is from a thin section viewed in cross-polarized light at 10x magnification, field of view is about 2 mm. The original pigeonite, represented by the large gray grain to the left, exsolved augite lamellae as it inverted to orthopyroxene. The cause for this reduction is unknown. The grain initially grew as a twinned monoclinic crystal. Their size ranges from 10 to 150 µm (Fig. A focused 1-µm beam was used to analyze olivine and plagioclase. Elemental maps of Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, and Fe Kα were collected with a 15-kV, 5.0 × 10 −8 A, 1-μm-diameter electron beam with a 5-μm step size. It is crowded with … Thrmlghout the subzone, plagioclase average grain size is variable, ranging to m. Anorthosite I: Textures thin this entire unit are uniform. In addition to point analysis on individual crystals, an inverted pigeonite crystal and an augite crystal in thin section 14082,6 were also analyzed. 77215 is probably a brecciated pigeonite-anorthite cumulate (figure 3), but the small size of the remnant lithic clasts prevents any certain determination of cumulate origin (Chao et al. XPL image, 2x (Field of view = 7mm) Olivine crystals partially altered by Iddingsite. English: Pigeonite, Albite-Anorthite Series, Augite (FOV ~ 4.5 x 3 mm) Locality: Tipogorree Hills, Tasmania, Australia Original description: A thin section of a dolerite with cross polarised light, showing brighly coloured pyroxenes (augite and pigeonite) and … #9 – Identify the green mineral in this section. Backscattered electron microimage of pyroxene crystal oriented by the x-ray method. . Photomicrograph of thin section of Moore county, N. c. meteorite. 2. Pyroxene - Pyroxene - Crystal structure: The pyroxene group includes minerals that form in both the orthorhombic and monoclinic crystal systems. Introduction to cumulus rock terminology and description in advance of practical. Full confirmation required expert electron microprobe analysis by Dr. Scott Kuehner. between orthopyroxene and inverted pigeonite overgrowths, but they made the incorrect assumption that the Fe-Mg dif- fusion coefficient in pyroxene was similar to that in olivine. The phase-transition temperature depends on Ca and Fe 2+ contents, as well as by cation ordering (Camara et al., 2003). The two twins then exsolved calcic pyroxene on (0 0 1) which formed the brightly colored chevron pattern. Some grains appear zoned with darker, relatively birefringent cores and paler rims. Blue bands of pigeonite in clinopyroxene with plagioclase feldspar (pale blue grains with barred patterns). 15075 is a coarse-grained porphyritic pigeonite basalt with subophitic matrix. Phosphates (mainly merrillite) are widespread in these areas. Augite and inverted pigeonite fom Oikocrysts averaging between 3 and 5 cm in (maximum 30 cm). 2 in section on 77075). Composite grains with orthopyroxene at the core, which is mantled, in turn, by inverted pigeonite, a second generation orthopyroxene and, on the outer margin, clinopyroxene in a reaction relation with the orthopyroxene, are sporadically developed. Find out why this happens and what it indicates when find in thin section. Pigeonite and augite compositions were resolved with the microprobe in scan mode. Very little ilmenite is present. This forms poikilitic, ... grained clays is pronounced giving the thin section and hand specimen a white speckled appearance when viewed with the naked eye. K-5a – This section contains phenocrysts of olivine, plagioclase and pyroxene. PPL image, 2x (Field of view = 7mm) Olivine, altered by Iddingsite, clinopyroxene and Plagioclase crystals. Breccia-in-breccia texture of fragmental breccia 72275. Pigeonite is totally lacking in the thin sections of Leg 179 gabbros we examined, and orthopyroxene is present in only four out of 20 oxide-rich samples. the thin section and for the oriented pyroxene crystals by electron microprobe (JEOL, JCXA-733) were made by making FIG. tion on the thin section of the Moore County meteorite as follows: "The bulk of the pvrorene present is pigeonite. Inverted pigeonite (15 - 20 modal %) is developed in places. The augite, represented by the pinkish-yellow grain to the right, has pigeonite exsolution lamellae. 1976). Along grain boundaries with oxides, plagioclase may be altered to radiating chlorite, minor amphibole and biotite. The thin section contains an estimated 54 volume percent clinopyroxene, 45% plagioclase feldspar and 1% opaque phases. 1.4 APOLLO 12 MARE BASALT PETROGENESIS-A plot of Ti02 .Q a: 1.2 1.0 0.8 0.6 D ++ ® D ~ QJ •• &1 • •• e 01tv11w Basah C ~ttBasah + 111Mr11t Basall • Feldspalllc Basalt against Al203 … The images were adjusted and combined by … Detailed electroll microprobe analyses were made on the thin section of the clast (15459,125). Frc. 15076 is a sister sample. Maximum pyroxene grain size is 2.2x1.0 mm. (100) section of Olivine. 15075 (42) Pigeonite Basalt. ( 198 1) downward to 12”C/y at 900-l 100°C. This finding differs from the Leg 118 observation, in which the oxide-rich gabbros contained ubiquitous Ca-poor pyroxene. 9. Formula: (Mg,Fe,Ca)(Mg,Fe)Si 2 O 6 Monoclinic. 2. This rock is a gabbro which originally had crystals of homogeneous pigeonite and augite. The clast consists mainly of olivine, with interstitial pigeonite and, locally, metal. In some thin sections, the Fe in the silicate minerals is in the process of being reduced to metal . Inverted pigeonite showing high birefringence augite exsolution lamellae in a (now) orthopyroxene host. DISTINCT OLIVINE & PIGEONITE SUITES, AND OPEN-SYSTEM EVOLUTION. thick. Click the microscope button to view a thin section for this sample. Scanning electron microscopy (SEM) was performed with a FEI Inspect S50 instrument, equipped with an energy-dispersive spectrometry (EDS) detector, at the Royal Belgian Institute of Natural Science, and with awith a JEOL 6400 at the Vrije Universiteit Brussel, Brussels, Belgium. Field width is 1.2 mm. Exsolution in inverted pigeonite. Natural oxides and minerals were used as standards. … Pigeonite will invert to augite + opx. Clive R. Neal and ... grained Study of corresponding thin sections demonstrate heterogeneities in all except 12015 and 12038. Between 3 and 5 cm in ( maximum 30 cm ) to m. Anorthosite I Textures. 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inverted pigeonite thin section 2021