Drilling in Hole U1309D (3010.12N, 4207.11W; 1645 mbsl) took place over four periods for a total of 15 days during IODP Expedition 304 and 34 days during IODP Expedition 305. Jennifer Kung. 2. 6. Clinopyroxenes hosting the intergrowths of brown amphibole + orthopyroxene near the high-temperature microscopic veins are clearly lower in TiO 2 than those of magmatic clinopyroxenes. In this way and taking into account all the pyroxene spectra found during the sample characterization, the chemical composition range of orthopyroxene goes from En 61.0 Fs 33.2 Wo 5.8 to En 62.9 Fs 35.1 Wo 2.0, whereas the chemical range for clinopyroxene goes from En 50.5 Fs 22.2 Wo 27.3 to En 53.3 Fs 25.8 Wo 20.9. Single Scaup Lake clinopyroxene crystals with intact, euhedral faces were hand-picked under stereo microscope from a 1 mm size fraction of mineral separates to mitigate compositional heterogeneity due to subtle intracrys - talline zoning. The pyroxene group includes minerals that form in both the orthorhombic and monoclinic crystal systems. Yanbin Wang. These clinopyroxene were used as seed crystals in the whole-rock powder. Large photo is1.7 mm wide. This rock is made up of about 5% Olivine, 5% Clinopyroxene and 90% Orthopyroxene. If X and Y are the same small-radius divalent cation like Fe or Mg or (syntheytically Co) the resultant structure is commonly orthorhombic, giving us the orthopyroxene group. Orthopyroxene to clinoplroxene transition The results from the two previous experimental studies of the MgGeO, orthopyroxene to clinopyroxene phase transition are presented in Figure 5A. Kirfel and Neu-haus's (1974) experiments were synthesis runs using poly- 500 400 1 000. Orthopyroxene uncommon. A mineral of the pyroxene group crystallizing in the orthorhombic system. This section contains two ideas for synthesis assignments that require students to pull skills and knowledge together to create resources and apply what they have learned. Clinopyroxene. Image by Elizabeth Thomas. At 2 GPa, the solidus of Px1 is located between 1250 and 1280 C, at a temperature about 70 C lower than the solidus of fertile lherzolite. and areas Plagioclase . Partially ionised curves for Si and 2.5+oxygen (Si and O1.5-) were adopted for clinopyroxene, orthopyroxene and olivine, and partial ionisation for oxygen (O0.9-) was used in spinel. calcium ferromagnesian silicate. In the XP view, the orthopyroxene shows only first-order interference colors-- the clinopyroxene ranges up to upper second order orange to pink (near the top center of the photo). O. sites of orthopyroxene and olivine; completely neutral Mg vs. Fe and Al vs. Cr in spinel T and M sites, respectively. Sample SIC-3. Orthopyroxene - Sample SIC-3. A mineral with inclined extinction will go extinct with the cleavage at an angle to these directions as the stage is rotated. The Low-Al OPX occurs in two It encompasses a range of solid solutions from (Mg,Fe)2[Si2O6] to Ca (Mg,Fe) [Si2O6]. Prominent igneous layers are found within the cumulate unit. The sample is blocky, subrounded, gray, and tough, with prominent exterior right hand side). In situ measurements of sound velocities and densities across the orthopyroxene high-pressure clinopyroxene transition in MgSiO 3 at high pressure. Pyroxene Group. 3 - Histogram showing orthopyroxene compositions in heavy mineral samples at each locality. Pyroxene is almost exclusively clinopyroxene and norite is conversely rich in orthopyroxene. The silicates contain small inclusions of troilite and chromite. If you need end member-specific information, please see the forsterite and fayalite pages. Difference between clinopyroxene and orthopyroxene in hand sample? Chemical formula. Clinopyroxene - XYZ2O6. Pyroxene 2 Feldspars, Amphiboles, and Sheet Silicates Each student will be given a hand sample and a thin section. It is easily distinguished from amphiboles by the nearly 90 o cleavage angles, and is distinguished from Opx by inclined extinction relative to the {110} cleavage, as discussed above. Garnets form as blebs around pyroxene in PPL (Bi) and CPL (Bii) in sample JS Kim. Back scattered electron (BSE) images Colour - colourless. This page concerns itself with olivine in general. On the other hand, as mentioned earlier, the secondary Extinction - inclined, complete . Note: the so-called "Ca-Tschermak molecule" is now known as kushiroite. Peridotite (US: / p r. . d o t a t, p r d. -/ PERR-ih-doh-tyte, p-RID--) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene.Peridotite is ultramafic, as the rock contains less than 45% silica.It is high in magnesium (Mg 2+), reflecting the high proportions of magnesium-rich olivine, with appreciable iron. Los Vientos (LoV) 263 was determined to be an ungrouped pallasite consisting of metal, olivine, and orthopyroxene in approximately equal proportions. Twinning distinctive - otherwise process of elimination. Students should first complete Sections 2.1 2.8, and should understand how to Specific Gravity: 3.2 - 3.6 : Hardness: 5-6 : Color: Black to dark green in hand sample. monoclinic (+,-) Relief - moderate. 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. Several orthopyroxene grains are present in these views, all showing these pleochroic colours. Diogenites are commonly brecciated, but there are unbrecciated samples as well (e.g., GRO 95555; Figure 2). Olivineorthopyroxeneclinopyroxene triangular plot for the Songling peridotites (red) and Majiayu peridotites (green). Compare UM2004-50-SiO:AlFeGd. pyroxene, any of a group of important rock-forming silicate minerals of variable composition, among which calcium-, magnesium-, and iron-rich varieties predominate. Hole U1309D. Note the thin overgrowths of hornblende (hbl), granular garnet (g) and biotite (bi), the result of secondary metamorphic recrystallization. Often zoned: usually An-rich cores and Ab-rich rims. It can have up to a few percent of olivine and clinopyroxene . Reference materials for H 2 O cover ranges from 52 to 328 ppm and from 9 to 559 ppm in orthopyroxene and clinopyroxene, respectively, covering most of the observed range of mantle water contents. (ASU) (Table 1). An-rich cores may alter more easily to sericite - a fine-grained turbid mica. PETROLOGY: 15418 is considered an important sample as a unique aluminous breccia the clinopyroxene and orthopyroxene analyses). All samples were stable under high laser power. Also if anyone could elaborate on which rock types may be richer in one of the pyroxenes. Pitchston e: resinous. In igneous rocks often with clinopyroxene and or olivine. Trace element distribution between orthopyroxene and clinopyroxene in peridotites from the Gakkel Ridge: a SIMS and NanoSIMS study to Mineralogy and , 2005. Usually Orthopyroxene composition range from En85 to En60 (Bronzite and Hypersthene). Cleavage: typical pyroxene cleavages parallel to {110}, which intersect at ~90. Was wondering if anyone could help me on this, there seems to be very little about it online. Yanbin Wang. Lab 1b Olivine . These 18 O values are among the highest ever recorded in mantle phases (see Supplementary Material). CaO vs. Cr 2 O 3 classification plot for mantle garnets in equilibrium with orthopyroxene and/or clinopyroxene, after Sobolev et al. Mineral. The Bushveld Igneous Complex ( BIC) is the largest layered igneous intrusion within the Earth's crust. The classification scheme for plutonic rocks, including mafic and ultramafic rocks, is included in this weeks lab handout (also posted on the web page). ) and clinopyroxene (Fs 8-13 Wo 45-49; Mg# 78-84) phenocrysts. synthetic sample: 0.0001: 293: Wang, Y.B., Neuville, D., Liebermann, R.C. Sample WC 297 is also a harzburgite, containing olivine (largely serpentinised) and orthopyroxene with an average grain size around 2 mm, and small amounts (~2%) of spinel and phlogopite. Physics of The Earth and Planetary Interiors, 2004. (2004) In situ measurements of sound velocities and densities across the orthopyroxene - high-pressure clinopyroxene transition in MgSiO3 at high-pressure. Daniel Neuville. Less than any other sample and occurs mostly in glomerocrysts. consisting of lamellar intergrowth of clinopyroxene and orthopyroxene, were measured. 3 wt %, respectively, and are distinctively lower than those in orthopyroxene porphyroclasts. Ti Scoria: coarsely cellular, dark colored. Early plagioclase common. These photos show mostly clinopyroxene (augite). Furthermore, grains of diameters less than 0.1 mm cannot be identified, thus the abundance of any mineral that occurs in a sig-nificant amount in grains of so small a diameter will be estimated too low. Pyroxene colour and pleochroism in metabasic gneiss. They are customarily designated by Kink banding is quite frequent in both olivine and orthopyroxene. Compare Orthopyroxene Subgroup. The peridotites are highly depleted, clinopyroxene-poor, harzburgites. At an initial pressure of 0.25 GPa the sample was heated to 400 0.81) (Fig. The Mg 2 / (Mg 2 s Fe as Fe 2 ) (Mg-number) of orthopyroxene in the orthopyroxenites is comparable with accepted mantle values, ranging from 0 88 to 0 91. Olivine. Koepke et al. In silica-saturated systems, the major phases are Al-bearing plagioclase and alkali 68 feldspar, and clinopyroxene have relatively low CaO; consequently, these clinopyroxene 69 crystallize with almost all tetrahedral sites filled with Si rather than Al (Salviulo et al. Figure 1. Diogenites are coarse-grained orthopyroxene-rich rocks, generally ~ 90% orthopyroxene, and contain minor amounts of olivine, chromite, plagioclase, clinopyroxene, and opaque minerals such as troilite and metal. laser for sample excitation (Mao et al., 1985). and Grtter et al. of short run times used in several studies and the slower kinetics of olivine vs. diopside melting. This Paper. Ultramafic plutonic rocks are rare. Occurrence and Distinction of the Pyroxenes. Jonathan Snow. Pyroxene (hand specimen) Type. The crystal above seen in XPL, and rotated so that the orthopyroxene is in (straight) extinction, whilst the clibnopyroxene, with inclined extinction is fully illuminated. Vitrophyre: porphyritic. Most samples are olivine gabbros with >5% olivine, >20% clinopyroxene, <1% orthopyroxene and <1% FeTi oxides. Residual spinel, orthopyroxene and clinopyroxene in these harzburgites are extremely depleted in Al O , and plot at the 23 most depleted end of the abyssal peridotite array defined by samples from slow-spreading ridges including samples from The molar ratio Mg/(Mg+Fe) in the sample is 0.91 and 5 wt % of A120 3 and 1 wt % of CaO are present. Clinopyroxene (Cpx) phenocrysts have the potential to record magmatic water contents and magma ascent rates through their concentration of H 2 O (incorporated as H + and commonly referred to as water). The solidus phases include olivine, orthopyroxene,high-CaclinopyroxeneandAl-richphasesthatchangefromspinel+amphibole(1.2 1.8GPa)tospinel+chloriteoverthe pressure range Clinopyroxene = titaniferous augite with reddish rims Kimberlite and lamproite magmas sample diamonds deep in the mantle and depending on the rapidity of ascent and emplacement, bring them to the surface in various Perido Pk Orthopyroxene Nahlin Sloko Nimbus Feather Mg/(Mg+Fe) Fig. Comments - may show simple twins and zoning . The low Al in the octahedral position is compensated for by the presence of Ti, Mn, Cr, Ni, and Fe 3+ in this crystallographic position. Distinguished by its lack of pleochroism, higher Very few sample localities are found in tectonic provinces that represent hand specimen, and in thin section have scat-tered phenocrysts (90% olivine and 10% clino-pyroxene). Image by Elizabeth Thomas. Clinopyroxene = pale brown augite: Olivine common, zoned. This was the case, for instance, for orthopyroxene, clinopyroxene and hornblende. clinopyroxene and brown spinel (isodiametric to holly leaf in shape). XYZ. The photo on the right (Figure 6.120) shows a sample of pyroxenite, composed of large crystals of orthopyroxene and clinopyroxene. Data from clinopyroxene Sr and Nd isotopes from lava sample ALIA-D115-18 of this study, together with major and trace element and isotopic constraints from other Samoan whole rock lavas from the same submarine dredge as ALIA-D115-18 (referred to as the ALIA-D115 dredge), are used to constrain the composition of the magma Some of the plagioclases have a . The subsolidus assemblage consists of clinopyroxene, orthopyroxene, and garnet. The most widespread members include aegirine, augite, hedenbergite and diopside. Abstract Subduction-related volcanic rocks are widespread in the Central Pontides of Turkey, and represented by the Hamsaros volcanic succession in the Sinop area to the north. If clinopyroxene is present it is often the variety diallage which shows well-developed parting parallel to {100} in the augite-diopside composition range. mass noun. Chayes, 1956, Interstitial alkali feldspar or feldspathoid: Phenocrysts: Olivine rare, unzoned or orthopyroxene rims. Pyroxenes have the general components is XY (Si,Al)2O6. Optical properties: Colour and Pleochroism: Usually colourless, gray, pale green or pale brown, darker colours associated with Fe-rich varieties titanaugite is more distinctly coloured from brown/pink to violet. Crystal structure. Birefringence - 0.002-0.022. university of cape town some aspects of the geochemistry of high-temperature peridotites and megacrysts from the jagersfontein kimberlite pipe, south africa clinopyroxene of garnet and orthopyroxene exsolution of clinopyroxene in plane polarised light (PPL) (Ai) and cross polarised light (CPL) in sample PA 7x1. The field of view is 4.5 mm. Scanned thin section of sample BDN03 showing metasomatic garnet (Grt), orthopyroxene (Opx), phlogopite (Phl) and clinopyroxene (Cpx). Augite - is commonly found in both plutonic and volcanic igneous rocks, as well as high grade meta-igneous rocks like gneisses and granulites. The compositions are shown for garnets exsolved in orthopyroxene megacrysts and orthopyroxenes found in mantle peridotites entrained by various kimberlite pipes from the Kaapvaal craton. Augite is a clinopyroxene, part of a solid solution series. Extrusive: Hand Sample: For the extrusive hand sample, I chose Sample 128. Grains that have the same shade of green in both images are augite, a clinopyroxene, and both varieties of pyroxene have high positive relief relative to enclosing plagioclase. Note the different extinction positions of the two phases. A large grain of orthopyroxene , with slightly greater relief than the clinopyroxene, is on the left edge of the photos, and several grains of green (PP) isotropic (XP) spinel can be seen in the upper right. English dictionary definition of ORTHOPYROXENE along with additional meanings, example sentences, and different ways to say. Full PDF Package Download Full PDF Package. More example sentences. Orthopyroxene - XYZ2O6. It has been tilted and eroded forming the outcrops around what appears to be the edge of a great geological basin: the Transvaal Basin. pyroxenes; Single-chain Silicates. They were cast into epoxy disk with reference zircons (Pleovice and Temora-2), ground and polished to expose the midsection of the grains. Pumice: finely cellular, light colored. Three samples plot as alkalic basalt on a TAS diagram, and one sample plots as trachy-basalt. This variation in mineral grain size They mostly contain combinations of olivine, clinopyroxene, and orthopyroxene. Crystal structure and typical site o ccupancies for (a) clinopyroxene and (b) orthopyroxene. Hornblende, clinopyroxene and plagioclase crystals in a Andesite. Generation of isotopic heterogeneity. Data from clinopyroxene Sr and Nd isotopes from lava sample ALIA-D115-18 of this study, together with major and trace element and isotopic constraints from other Samoan whole rock lavas from the same submarine dredge as ALIA-D115-18 (referred to as the ALIA-D115 dredge), are used to constrain the composition of the magma PPL image, 2x (Field of view = 7mm) The evidence of strain and deformation in these crystals, together with the absence of cumulate textures, rules out Form: crystals form stubby prisms elongate along the c-axis, basal sections are 4 or 8 sided and show two cleavages at 90. Based on textures, orthopyroxene can be divided into four categories: magmatic rims, blebs in the interfingering clinopyroxene, blebs near the high-temperature microscopic veins, and filling high-temperature microscopic veins penetrating olivine grains. A subgroup name for monoclinic Pyroxene Group minerals. The rock illustrated in these images contains both clinopyroxeneand orthopyroxene, and the significantly higher Cr2O3content of the clinopyroxene in this sample gives it a pale green colour in plane polarized light, whereas the Cr-poor orthopyroxene is colourless (A). A diagnostic feature of. Common Forms/Occurences. Here we investigate three issues related to the fidelity and utility of the Cpx water record: the partitioning of water between Cpx and melt, the diffusivity of water in natural Some of the special terms used are: Gabbro (sensu stricto) = plagioclase and clinopyroxene Norite = plagioclase and orthopyroxene Pyroxene is a set of essential rock-forming inosilicate minerals discovered in many igneous and metamorphic rocks. Figure 2 Multi-phase solid inclusions in BDN03 garnet. < Menu. Orthorhombic pyroxenes are referred to as orthopyroxenes, and monoclinic pyroxenes are called clinopyroxenes.The essential feature of all pyroxene structures is the linkage of the silicon-oxygen (SiO 4) tetrahedrons by sharing two of the four corners to form Far-infrared, mid-infrared, and Raman spectra of MgGeO, orthopyroxene, clinopyroxene, and ilmenite are shown in Figures 2,3 and 4, respectively, and peak positions are listed in Table 2. The types of minerals that are calculated by this chart are Olivine, Orthopyroxene, and Clinopyroxene. 2000). Rocks that contain less than 10% plagioclase are ultramafic (pyroxenite if pyroxenes are the dominant minerals). Under cross polarized light, a mineral with parallel extinction will go extinct (dark) when the cleavage direction is parallel to the north-south and east-west directions as the stage is rotated. BE-12-01-11 Hand sample and billet showing layers of host rock with sulfide mineralization Pyroxenes are the most significant and abundant group of rock-forming ferromagnesian silicates. The bulk modulus, in gigpascals, expressed 17% orthopyroxene, 13% clinopyroxene, and 10% garnet [see McDonough, 1990]. Only one well developed cleavage is visible in this orthpyroxene grain. Note: Large orthopyroxene has pale pink to pale green pleochroism, and typically less well developed cleavage than clinopyroxene (pale green, slightly cloudy appearance above). S-75-33763 . Advanced Notes. Short, 8-sided prisms. Clinopyroxene and amphibole are the main constituents of the rock and the only minerals showing complex zoning patterns. Orthopyroxene absent. Image (B) shows garnet mineral relationships within the granulites in the Pitcairn xenoliths. They are found in almost every variety of igneous rock and also occur in rocks of widely different compositions formed Bronzite is named for the noticeable bronze reflection (Schiller luster) that may be seen in hand specimen. The hole was spudded using a hammer drill with 13 inch casing in an effort to provide stable reentry for a deep hole. Crystal System. Photomicrograph of orthopyroxene (low birefringence, skinny lamellae) surrounded by clinopyroxene (higer birefringence, coarse lamellae). A focused 1-m beam was used to analyze olivine Physical Properties. To prepare the matrix, plagioclase grains were hand-picked from a sample of partially crushed gabbro from the Bamble Sector, SE Norway. Phase-equilibria experiments The Si and Al of orthopyroxene range between 1.837 and 1.936 and 0.0640.163 apfu, respectively, whereas clinopyroxene vary between 1.847 and 1.977 and 0.0230.153 apfu, respectively. Magmatic clinopyroxene has exsolution lamellae of Fe-Ti oxide, and therefore the primary TiO 2 content would have been even higher. Figure generated with CrystalMaker. Because unambiguous identification of orthopyroxene requires careful thin section observation, the amount of orthopyroxene-bearing gabbro is a minimum estimate (see Igneous petrology). Robert Liebermann. Both orthopyroxene and clinopyroxene variety are present. A review of literature data on natural samples and experiments suggests that orthopyroxene clinopyroxene veins primarily form between 750950 C and over a large pressure range from 0.83.4 GPa. Pyroxene. Perlite: concentric fractures. The physical and optical properties detailed above refer to augite, a clinopyroxene common in mafic igneous rocks. The O 2 product was collected in a sample vessel containing a molecular sieve at -196C and measured on They have homogeneous water contents, defined as a standard deviation of <10% for analyses across multiple grains. The most common member in rocks is enstatite. RI - 1.674-1.764. Quartz = q. This sample shows alternating layers On the other hand, partial melting of gabbro cumulate produces a Ti-, Cr- and REE-poor melt with high Mg#. Two are gabbros (15R-1W-112/116 and 25R-1W-93/100) with 1% olivine and <1% FeTi oxides. The Cougar Divide unit exhibits mingling textures in hand sample and both Si-poor Orthopyroxene is found in many Andesite, and in basaltic Andesite, the appearance of orthopyroxene usually heralds the disappearance of Olivine. Partially ionised curves for Si and oxygen (Si2.5+ and O1.5-) were adopted for clinopyroxene, orthopyroxene and olivine, and Olivine is a solid solution series mineral whose two most common end members are forsterite (Mg) and fayalite (Fe). Generation of isotopic heterogeneity. 8. Normally it is not possible to determine the composition of these rocks. For clinopyroxene, final Fourier difference Gabbronorites show the same textural relationships as the associated gabbros. orthopyroxene host with blebs of clinopyroxene in PPL (left) and XPL (right). Gabbroic rocks the gabbros (sensu lato) of QAPF field 10, may be further subdivided according to the relative abundances of their orthopyroxene, clinopyroxene, olivine and hornblende as shown in Fig. Optical properties: Colour and Pleochroism: Colourless. l 360 experiments (Table 1) indicate clinopyroxene is the phase of lower enthalpy and is stable energetically relative to orthopyroxene at 913 K, which is consistent with Ozima and Akimoto's (1983) study. However, the calorimetric value of Af{ j3, -3440 + 661 J. The minerals forming the veins preserve the highest 18 O values (sample TL112: 18 O opx + 9.84, 18 O pl + 10.56; sample TL5: 18 O pl + 9.63, 18 O opx + 8.02). rocks are classified on the basis of the modal abundances of olivine, orthopyroxene, clinopyroxene, and plagioclase. been determined to a pressure of 12.5 GPa. It is an intermediate member of diopside and hedenbergite. Brugman 4 66 experimental studies tend to explore Mg-rich augite to diopside, and in mafic rather than silicic 67 systems. BE-12-01-4 Hand sample and billet with layer of sulfide accumulation.. 24 10. Amphibole in the sample has much darker green colour, stronger pleochroism and cleavages that intersect at 120 o. The largest orthopyroxenes sometimes show clinopyroxene exolution lamellae. Also in high-grade meta rocks. A phenomenon similar to the Holmes effect (e.g. Crystal System: Monoclinic 2/m: Luster: Vitreous, translucent. It is from the layered ultramafic Stillwater Complex of Montana; two other photos of Stillwater rocks appeared earlier in this chapter (Figures 6.20 and 6.21 ). The pyroxene group is composed of minerals of the general formula XYSi 2 O 6, where X and Y are two divalent cations or a monovalent and a trivalent cation. grained granulite facies texture in the form of partly recrystallized orthopyroxene (opx), clinopyroxene (cpx), and primary garnet (g). An overview of samples and their localities is given in Table 1. A Pyroxene Group. Gabbronorite and orthopyroxene-bearing gabbro are included in this group. The fundamental methods for naming mafic and ultramafic plutonic rocks are based on the proportions of clinopyroxene, orthopyroxene, olivine, and plagioclase that a rock contains. Orthopyroxene - Sample SIC - 4. The presence of clinopyroxene in lherzolite allows us to use clinopyroxene-orthopyroxene geothermometers of Brey and Khler (1990) and Wells (1977) which show the temperature of 1200-1250 and 1050-1150C, respectively. Regionally, Sugarloaf alkalic basalts are generally similar to the nearby (< 10 km) Stewart Mountain alkalic basalts but are slightly more enriched in incompatible trace elements. Cpx is clinopyroxene, Opx is orthopyroxene, Plag is plagioclase. Baosheng Li. Veins of orthopyroxene 1-3 mm wide cut BF-484-5 Hand sample and billet showing sulfide mineralization in rhyolite host rock .. 22 9. Plagioclase less common, appears later. Zircons were hand-picked from a trondhjemitic dyke sample SL4. Some edenitic hornblende crystals contain cores of orthopyroxene.. The black groundmass contains nely orthopyroxene is 12 mm, clinopyroxene is 0.251 mm, and spinel is ~0.15 mm. Clinopyroxene contains calcium. Clinopyroxene -. Download Download PDF. Crystals in igneous rocks often rectangular laths. The abundance of these minerals indicates that the that the rock is an Olivine Websterite. Compare Clinopyroxene Subgroup. The sample is a weakly foliated granulite formed of plagioclase, orthopyroxene, clinopyroxene and minor hornblende.. clinopyroxene M1 and M2 sites, respectively; fully ionised Mg2+ vs. Fe2+ in both M1 and M2 sites of orthopyroxene and olivine; completely neutral Mg vs. Fe and Al vs. Cr in spinel T and M sites, respectively. Plagioclase, Olivine, Orthopyroxene, and Clinopyroxene Lab 1a . The dacite of Cougar Divide (plagioclase, clinopyroxene, orthopyroxene, Fe-Ti oxides, olivine) and the andesite of Mazama Lake (plagioclase, clinopyroxene, orthopyroxene, Fe-Ti oxides, olivine) are more Si-poor, and exhibit evidence for magma mixing. (b) Photomicrograph showing exsolved needles of Cpx and Opx in the garnet crystal, testifying to a majoritic precursor. (2004). Clinopyroxene 3 0.25-1.25mm subhedral to anhedral rounded grains of low integrity that occur as both small crystals within groundmass, and as glomerocrysts with each other (up to 2mm), plagioclase, and Fe-Ti oxides. Clinopyroxene is the principal macrocryst phase, reaching 15% volume fraction of the rock in the centre of the sill (Ubide et al., 2012).Clinopyroxene macrocrysts show complexly zoned subhedral to anhedral cores and in some cases, aligned Found as blocky crystals in basalts, gabbro, and andesites. In C, a virtually monomineralic orthopyroxene rock in which the pyroxene is relatively Mg-rich, pleochroism is 9). (Sample Q114; Station 15+90; 2 mm field of view.) Interference colours - 3rd order. On the other hand, the portion in the Maku- Kamjong stretch (latitudes 2457N- 2553N and longitudes 9428E- 9431E) consists of Orthopyroxenite is an ultramafic and ultrabasic rock that is almost exclusively made from the mineral orthopyroxene, the orthorhombic version of pyroxene and a type of pyroxenite. Sample WC 296 is a highly tectonised spinel harzburgite, containing orthopyroxene porphyroclasts up to 1 cm in diameter. Chemical Formula. No orthopyroxene.