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