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The presence of … Clive R. Neal and ... grained Study of corresponding thin sections demonstrate heterogeneities in all except 12015 and 12038. Very little ilmenite is present. Find out why this happens and what it indicates when find in thin section. 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. ZAF 4 corrections were applied to the analyses. Click the microscope button to view a thin section for this sample. Breccia-in-breccia texture of fragmental breccia 72275. pigeonite, augite, and maskelynite. 15075 is a coarse-grained porphyritic pigeonite basalt with subophitic matrix. 2. Introduction to cumulus rock terminology and description in advance of practical. 15076 is a sister sample. 4). thick. thin section, with 0.2-0.5 mm crystals and a more granoblastic texture; this zone was found to be in optical continuity with the rest of the thin section, strongly suggesting its origin as a primary crystallization feature, possibly as a “nucleation burst” similar to those found in terrestrial cumulates. The clast consists mainly of olivine, with interstitial pigeonite and, locally, metal. Frc. the thin section and for the oriented pyroxene crystals by electron microprobe (JEOL, JCXA-733) were made by making FIG. For the inverted pigeonite (pigI), the crystallization temperature of the primary pigeonite prior to inversion, at ~1200 °C, was slightly higher than its PER temperature of 1140 °C, as shown in Fig. Microscope. This forms poikilitic, ... grained clays is pronounced giving the thin section and hand specimen a white speckled appearance when viewed with the naked eye. 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 … 15075 (42) Pigeonite Basalt. Hydration and other sub-solidus reactions to form secondary minerals in igneous rocks. Their size ranges from 10 to 150 µm (Fig. Figure 53. Image is from a thin section viewed in cross-polarized light at 10x magnification, field of view is about 2 mm. Phosphates (mainly merrillite) are widespread in these areas. The two twins then exsolved calcic pyroxene on (0 0 1) which formed the brightly colored chevron pattern. A focused 1-µm beam was used to analyze olivine and plagioclase. has Detailed electroll microprobe analyses were made on the thin section of the clast (15459,125). To the right of the clast is some of the reduced pigeonite lithology shown in Fig. The images were adjusted and combined by … "Small roughlv quadrilateral areas bounded by cleavages and augite lamellae have inverted to hy-persthene in a few of the pigeonite crystals." inclusions. Lecture 6: Introduction to Analytical Techniques for Igneous Petrology (Prof. P.F. 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 … Methods: A petrographic thin section and a polished chip of A 09545 were used. PPL image, 2x (Field of view = 7mm) Olivine, altered by Iddingsite, clinopyroxene and Plagioclase crystals. Note the clast of pigeonite basalt in this section. The formation temperature of other pigeonites (uninverted), at 1100 °C, was lower than each PER temperature. Analytical results … The pale brownish clinopyroxene displays simple twinning and in some cases distinct chevron-like inverted-pigeonite exsolution textures. Pigeonite and augite compositions were resolved with the microprobe in scan mode. 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. Microscope. The location of this clast in the thin section is indicated in Fig. #20 – Identify the large phenocrysts in this section and give a full description. Pigeonite. Maximum pyroxene grain size is 2.2x1.0 mm. Primary minerals olivine (Table T5), clinopyroxene (Table T6), plagioclase (Table T7), orthopyroxene, and inverted pigeonite (Table T6) were analyzed utilizing the JEOL 733 electron microprobe at the University of Houston (Texas, USA).Operating conditions included 15-keV accelerating voltage and 10-nA beam current. Noting that Fe-Mg diffusion rates in pyroxene are likely to be a factor of x lo3 slower than in olivine, JONES ( 1982) revised the cooling rates of DELANEY et al. K-5a – This section contains phenocrysts of olivine, plagioclase and pyroxene. It has beautifully de-veloped augite lamellae parallel to {001}." PPL image, 2x (Field of view = 7mm) Olivine, altered by Iddingsite, clinopyroxene and Plagioclase crystals. 5). We confirmed that the host phase is pigeonite by the x-ray ( 198 1) downward to 12”C/y at 900-l 100°C. Inverted Pigeonite. This fused crust is about 0.2 mm. The grain initially grew as a twinned monoclinic crystal. Inverted pigeonite (15 - 20 modal %) is developed in places. 2. A polished thin section (PTS) labeled PTS 01-1 was prepared from a 179-mg sample NWA 2977 01 and was examined by using petrographic microscopes (Nagaoka et al. Formula: (Mg,Fe,Ca)(Mg,Fe)Si 2 O 6 Monoclinic. 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. 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. White areas show pigeonite and dark areas show augite. . Pigeonite will invert to augite + opx. This is an inverted pigeonite (pyroxene) from the Bushveld Complex in South Africa. 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. Orthorhombic pyroxenes are referred to as orthopyroxenes, and monoclinic pyroxenes are called clinopyroxenes. Some grains appear zoned with darker, relatively birefringent cores and paler rims. #5 – This section contains inverted pigeonite. Classification of PigeoniteHide. "This hypersthene . Exsolution in inverted pigeonite. 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). 1. 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. Electron microprobe scans along specific crystallographic directions are discussed later in this report. This sample is feldspar rich. Blue and yellow crystals on the top left and lower center are augite, with thin pigeonite exsolution lamellae and twins. #9 – Identify the green mineral in this section. Natural oxides and minerals were used as standards. Single crystals for X-ray diffraction studies were separated from the same clast and microprobe analyses were also made on one crystal after the X-ray study. Dark glass of the crust on meteorite is shown on upper right hand edge. These Orthopyroxene habits frequently occur together in a single thin section. 2.2. Augite and inverted pigeonite fom Oikocrysts averaging between 3 and 5 cm in (maximum 30 cm). Pigeonite and its relation to other pyroxenes. Pyroxene - Pyroxene - Crystal structure: The pyroxene group includes minerals that form in both the orthorhombic and monoclinic crystal systems. The essential feature of all pyroxene structures is the linkage of the silicon-oxygen (SiO4) tetrahedrons by sharing two of the four … 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 DISTINCT OLIVINE & PIGEONITE SUITES, AND OPEN-SYSTEM EVOLUTION. PPL image, 2x (Field of view = 7mm) (100) section of Olivine. The next day a thin section was prepared in excited anticipation by Dr. Anthony Irving and David McDougall at the University of Washington and revealed the characteristic presence of maskelynite. The original pigeonite, represented by the large gray grain to the left, exsolved augite lamellae as it inverted to orthopyroxene. The augite, represented by the pinkish-yellow grain to the right, has pigeonite exsolution lamellae. This finding differs from the Leg 118 observation, in which the oxide-rich gabbros contained ubiquitous Ca-poor pyroxene. tion on the thin section of the Moore County meteorite as follows: "The bulk of the pvrorene present is pigeonite. Field width is 1.2 mm. inverted pigeonite, to discuss its formation conditions for a better understanding of the lunar igneous activ-ity of the young NWA 773 clan. Unlike other clinopyroxenes such as augite and diopside, pigeonite has space-group symmetry P2 1 /c at room temperature (at high temperatures it has space group C2/c). This rock is a gabbro which originally had crystals of homogeneous pigeonite and augite. (100) section of Olivine. The scattered, irregular black areas in the BSE image include both pores and carbon. They usually occur interstitially between olivine an d pyroxenes. XPL image, 2x (Field of view = 7mm) Olivine crystals partially altered by Iddingsite. The pigeonite has inverted to orthopyroxene with augite exsolution. Fact sheet. Blue bands of pigeonite in clinopyroxene with plagioclase feldspar (pale blue grains with barred patterns). Along grain boundaries with oxides, plagioclase may be altered to radiating chlorite, minor amphibole and biotite. The phase-transition temperature depends on Ca and Fe 2+ contents, as well as by cation ordering (Camara et al., 2003). Thrmlghout the subzone, plagioclase average grain size is variable, ranging to m. Anorthosite I: Textures thin this entire unit are uniform. Full confirmation required expert electron microprobe analysis by Dr. Scott Kuehner. Inverted pigeonite showing high birefringence augite exsolution lamellae in a (now) orthopyroxene host. Cross-polarized light view only. The composition of the igneous orthopyroxene did not change because high calcium (2.1 wt% of … Note augite lamellae in pigeonite are parallel to [100[ plane. … Microprobe analyses were determined using a SEM Cambridge S 360 electron microprobe equipped with EDS Link Analytical QX 2000. (Photo courtesy Alex Strekeisen; unauthorized reproduction is prohibited.) In some thin sections, the Fe in the silicate minerals is in the process of being reduced to metal . Backscattered electron microimage of pyroxene crystal oriented by the x-ray method. 2.5 mm plag opx h) plag opx cpx 2.5 mm g) 62 Fig. 9. was done because the thin section of Y-791538 was lost during thinning and because pigeonite was not present in the RKPA80239 thin section. 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. On the left edge of the thin section, there are some shock melt pockets (Fig. Click the microscope button to view a thin section for this sample. Figure 52. 2. In addition to point analysis on individual crystals, an inverted pigeonite crystal and an augite crystal in thin section 14082,6 were also analyzed. Methods A 382-mg slice of NWA 2977 was divided into two pieces labeled NWA 2977 01 and 02. It is crowded with … 2 in section on 77075). 1976). The thin section contains an estimated 54 volume percent clinopyroxene, 45% plagioclase feldspar and 1% opaque phases. Photomicrograph of thin section of Moore county, N. c. meteorite. The cause for this reduction is unknown. Demonstrate heterogeneities in all except 12015 and 12038 phase-transition temperature depends on Ca and Fe 2+ contents, well... 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Of Moore county, N. c. meteorite Alex Strekeisen ; unauthorized reproduction is prohibited. uninverted ), at °C.: the pyroxene group includes minerals that form in both the orthorhombic and pyroxenes... Textures thin this entire unit are uniform location of this clast in the thin section for this.. Of view is about 2 mm x-ray method 2977 01 and 02 Bushveld Complex in South Africa of the has. Except 12015 and 12038 contains phenocrysts of olivine, altered by Iddingsite, clinopyroxene and plagioclase for this sample areas... Study of corresponding thin sections demonstrate heterogeneities in all except 12015 and 12038 I: Textures thin entire! Analytical Techniques for igneous Petrology ( Prof. P.F Strekeisen ; unauthorized reproduction is prohibited. the microprobe scan... Occur together in a single thin section, there are some shock melt (!

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