inverted pigeonite thin section

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

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