A notorious example of this is Mount St. Helens in which dacite domes formed from previous eruptions. Dacite is a fine-grained igneous rock that is normally light in color. Nevertheless, because of the moderate silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. 2017; Valencia et al. If you would like to visit the area, drive east eight miles from Apache Junction on Highway 60-70 toward Florence Junction. (Mg#51–70, see Table 4). Immiscibility has been discussed as a possible explanation for the formation of lunar granites and the absence of intermediate lithologies (e.g., Jolliff 1991; Seddio et al. 2003; Zhang et al. The An value is higher than those of plagioclase in the Apollo granitic samples (An80–50; Wieczorek et al. 2018). 2b; 27 vol%) forms elongate crystals between coarser plagioclase. In Fig. 2013); granitic breccia (Morris et al. Haldar, in Platinum-Nickel-Chromium Deposits, 2017. 1991), and the FeO content in plagioclase of the silicic clast is as high as those of the Apollo very-low-Ti mare basalt (0.90–1.34 wt% in Papike et al. 1978; Taylor et al. Porphyritic dacite which solidified on the surface of the lava dome in 1986 gives a whole rock K-Ar 'age' of 0.35 ± 0.05 million years (Ma). Records indicate no gold, copper or silver has ever been found in sufficient quantity to justify these diggings. The Chao dacite is a type of lava dome known as a coulée. 2014; Valencia et al. Therefore, the plagioclase-rich clast is categorized as AG, although the presence of olivine was not reported in the AG clasts described by Valencia et al. K-Ba-feldspar is not as abundant as plagioclase or silica, but comprises approximately 15 vol% of the mode in the clast and appears to have co-crystallized with silica. 1988); QMD (Taylor et al. Conforms to HazCom 2012/United States Page 1 of 8 Safety Data Sheet Dacite Section 1. These elongated flow structures form when highly-viscous lavas flow onto steep surfaces. 2014; Shaulis et al. Double ternary diagram which is used to classify igneous rocks based on mineralogic composition. Dacite is the volcanic equivalent of granodiorite. Therefore, the formation of tridymite and cristobalite in the dacite clast by unloading after shock impact can be excluded; a shock melt origin of the dacite clast is unlikely. Based on the evidence currently available, we favor the interpretation that the dacite clast formed in a system independent of the olivine gabbro → anorthositic gabbro → ferroan gabbro (pyroxene gabbro + symplectite + ARFe) trend. The authors declare that they have no competing interests. Proc Natl Acad Sci 113:7071–7076, Morris RW, Taylor GJ, Newsom HE, Keil K, Garcia SR (1990) Highly evolved and ultramafic lithologies from Apollo 14 soils. 1999; Gullikson et al. Today these cliffs dominate the region around Don’s Camp. In: Proceedings of the 18th lunar and planetary science conference, 1987, Houston, Texas, pp 187–201, Snape JF, Nemchin AA, Bellucci JJ, Whitehouse MJ, Tartèse R, Barnes JJ, Anand M, Crawford IA, Joy KH (2016) Lunar basalt chronology, mantle differentiation and implications for determining the age of the Moon. 2011; Nagaoka et al. Thin-section scale back-scattered electron (BSE) images and X-ray elemental maps were collected by an electron probe micro-analyzer (EPMA) (JEOL JXA-8900) at Kobe University. 90, 2006 September. Olivine and ilmenite in the silicic clast have Fe# (molar Fe/[Fe + Mg] × 100) of 99–100 (Table 2) corresponding to late-stage magmatic crystallization. Andesite is a fine-grained rock that forms when the magma erupts … MK carried out Raman spectroscopy. 2009), Northwest Africa 11119 (NWA 11119; Srinivasan et al. Therefore, if the dacite formed from the alkali-silica-rich inclusions in the ARFe rocks, simple coalescence of inclusions alone is not a likely origin of the dacite. 2018). Clast name abbreviations: OG olivine gabbro, AG anorthositic gabbro, OPB olivine-phyric basalt. Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Elements 5:29–34, Gullikson AL, Hagerty J, Reid MR, Rapp JF, Draper D (2016) Silicic lunar volcanism: testing the crustal melting model. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. 3c), and one coarser crystal (210 μm × 140 μm) occurs near the bottom of the clast (Px crs in Fig. Lunar meteorite NWA 2727 was found in Morocco or Algeria in 2005 (Connolly et al. In: Abstracts of the 38th lunar and planetary science conference, 2007, Houston, Texas, p 2109, Zhang A-C, Hsu W-B, Floss C, Li X-H, Li Q-L, Liu Y, Taylor LA (2011) Petrogenesis of lunar meteorite Northwest Africa 2977: constraints from in situ microprobe results. 7). Astrophys J 778:60. https://doi.org/10.1088/0004-637X/778/1/60, Le Bas MJ, Le Maitre RW, Woolley AR (1992) The construction of the total alkali-silica chemical classification of volcanic rocks. The NWA 773 FG/ARFe clasts formed in a co … Silica minerals with abundant plagioclase feldspar were not identified in OG, AG, and FG lithologies in this PTS. Protected in 1906 for its scientifc value, Devils Tower remains a … Karymsky caldera was explosively formed 7900 yr BP as the result of eruption of 5–7 km 3 of dacite with collapse of Pra-Karymsky volcano (Braitseva and Melekestsev, 1991). In: Abstracts of the 50th lunar and planetary science conference, 2019, the Woodlands, Texas, p 2270, Nagaoka H, Karouji Y, Takeda H, Fagan TJ, Ebihara M, Hasebe N (2015) Mineralogy and petrology of lunar meteorite Northwest Africa 2977 consisting of olivine cumulate gabbro including inverted pigeonite. Plagioclase (red in Fig. Geochim Cosmochim Acta 213:435–456, Shearer CK, Papike JJ, Spilde MN (2001) Trace-element partitioning between immiscible lunar melts: an example from naturally occurring lunar melt inclusions. 2011; Nagaoka et al. 2019). Several of these clast-types have been linked together to form during a common igneous differentiation suite (Fagan et al. statement and All analyzed pyroxenes from the silicic clast have a Ti/Al ratio ranging from 0.4 to 0.6 with an average value of 0.5 as shown in Fig. 1976; Fagan et al. Most proposed sites of silicic volcanism identified by remote sensing occur in the PKT, located on lunar nearside (Glotch et al. J Geophys Res Planet 108:5069, Head JW, McCord TB (1978) Imbrian-age highland volcanism on the moon—the Gruithuisen and Mairan domes. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Meteorit Planet Sci 41:1383–1418, Day JMD, Ash RD, Liu Y, Bellucci JJ, Rumble D III, McDonough WF, Walker RJ, Taylor LA (2009) Early formation of evolved asteroidal crust. The dacite clast probably crystallized at a relatively fast cooling rate that resulted in incomplete transformation of the high-T polymorphs to quartz. Some time during the 1930’s Lava Cliffs became known as Dacite Cliffs. 2003, 2010; Morota et al. The NWA 773 clan shares (1) mafic minerals and major element composition; (2) isotopic ages of 3.0 to 3.1 Ga for the most part, though some clasts in the breccia are older; and (3) KREEP-rich minor element composition (Fagan et al. 1988; Marvin et al. Lithos 212-215:158–188, Wieczorek MA, Jolliff BL, Khan A, Pritchard ME, Weiss BP, Williams JG, Hood LL, Righter K, Neal CR, Shearer CK, McCallum IS, Tompkins S, Hawke BR, Peterson C, Gillis JJ, Bussey B (2006) The constitution and structure of the lunar interior. These petrological features are similar to other OG clasts in the NWA 773 clan (Fagan et al. 2000; Sensarma and Palme 2013). This model is consistent with the observation that quartz is the only SiO2 polymorph found in lunar granitic samples (Warren et al. Instead of gold, Carney found an abundance of copper stain. Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. In contrast, feldspars and silica are much more abundant than mafic phases in the dacite clast. In addition to the large pyroxene gabbro clast, other FG lithologies are present as smaller clasts in the PTS and in other specimens of NWA 2727 (Bunch et al. While we cannot rule out the possibility that the dacite clast is an unusual variety of the FG/ARFe lithology, the high SiO2-content, high ratio of plagioclase/K-feldspar and occurrence of apatite without merrillite all point toward a distinct origin for the dacite clast (see “Petrogenesis of the dacite clast” section for further discussion). In: Proceedings of the 21st lunar and planetary science conference, 1990, Houston, Texas, pp 101–118, Jolliff BL, Floss C, McCallum IS, Schwartz JM (1999) Geochemistry, petrology, and cooling history of 14161,7373: a plutonic lunar sample with textural evidence of granitic-fraction separation by silicate liquid immiscibility. In detail, however, the two lithologies are distinct. Sci Adv 4:eaar4378, Koike C, Noguchi R, Chihara H, Suto H, Ohtaka O, Imai Y, Matsumoto T, Tsuchiyama A (2013) Infrared spectra of silica polymorphs and the conditions of their formation. Geochem Geophys Geosyst 1:2000GC000083, Valencia SN, Jolliff BL, Korotev RL (2019) Petrography, relationships, and petrogenesis of the gabbroic lithologies in Northwest Africa 773 clan members Northwest Africa 773, 2727, 3160, 3170, 7007, and 10656. In: Proceedings of the 8th lunar science conference, 1977, Houston, Texas, pp 2153–2189, Rhodes JM, Hubbard NJ (1973) Chemistry, classification, and petrogenesis of Apollo 15 mare basalts. Whereas the symplectites formed dominantly by pyroxferroite breakdown (Fagan et al. (2018). The presence of a silica-rich feldspathic glass in the lunar meteorite Yamato 983885 (Y-983885) also requires silica-enrichment followed by rapid cooling (Arai et al. On the IUGS classification of volcanic rocks based on modal abundances of silica, alkali feldspar, and plagioclase, this clast falls on the boundary between rhyolite and dacite (Fig. Fine pyroxene crystals that are interwoven with apatite in the mafic cluster and the coarse pyroxene have essentially identical Wo-En-Fs compositions; the fine pyroxene near the upper right margin (Px fine2 in Fig. 2011). Compositions reported by Fagan et al. Answer:Explanation: Composite Volcano. This volcanic flow occurred during the Tertiary Period of geologic time. 1988; Papike et al. It is often found associated with andesite, and forms lava flows, dikes, and, in some cases, massive intrusions in the centres of old volcanoes. Google Scholar, Barrat J-A, Yamaguchi A, Greenwood RC, Bollinger C, Bohn M, Franchi I-A (2009) Trace element geochemistry of K-rich impact spherules from howardites. 3c, d). Nevertheless, because of the moderate silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. However, as noted by Seddio et al. The streak of Dacite is white. Fayalite and silica also occur together in the ARFe lithology, but they form coarser crystals instead of symplectic intergrowths; in addition, the ARFe clasts contain K-Ba-feldspar and/or feldspathic glass along with merrillite, ± apatite, ± ilmenite, and ± hedenbergitic pyroxene. SLI might have played a role in the origin of the dacite clast. Geochem J 29:91–95, Jolliff BJ, Zeigler RA, Korotev RL (2007) Compositional characteristics and petrogenetic relationships among the NWA 773 clan of lunar meteorites. 2018). 9, the bulk composition of the dacite clast is compared with lunar evolved rocks returned by Apollo missions (KREEP basalt, QMD, granite/felsite, granitic breccia) (Hubbard et al. 3d). Another possible factor in the origin of the dacite is silicate liquid immiscibility (SLI). By Categories In미분류 Posted on On 26 12월 2020 Categories In미분류 Posted on On 26 12월 2020 The last eruptions formed Shastina's present summit about a hundred years later. 2003; Jolliff et al. In context|geology|lang=en terms the difference between andesite and dacite is that andesite is (geology) a class of fine-grained intermediate igneous rock, of volcanic origin, containing mostly plagioclase feldspar while dacite is (geology) an igneous, volcanic rock with a high iron content. White circle plot represents the silicic clast (this work). Anhedral quartz single crystals (10 to 20 μm in radius) are present in clinopyroxene-phyric basalt (CPB) clasts in NWA 2727 (Kayama et al. Thus, among the possibilities discussed by Calzada-Diaz et al. 1977; Warren and Wasson 1978; Warren et al. 2019), but the modal abundances of silica are less and grain sizes are smaller than silica of the silicic clast. Dacite is formed when a volcano erupts molten material (magma) with a relatively high silica and alkali content onto the surface, and that material solidifies. However, the immiscible inclusions are dominated by alkali feldspar rather than plagioclase, and the main Ca-phosphate of the ARFe lithology is merrillite rather than apatite. The AG has a cumulate texture and is dominated by plagioclase and pyroxene (Valencia et al. From study of meteorites from asteroid 4 Vesta, dacite formation occurred on Vesta by crustal partial melting (Hahn Jr. et al. Immediately north of Don’s Camp are towering cliffs formed from volcanic lava some seventeen million years ago. The dacite clast is more enriched in SiO2 and alkali elements (Na, K, Ba) than other lithologies of NWA 773 clan. 1977; Warren and Wasson 1978; Warren et al. 1993; Seddio et al. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. Silica minerals were not identified. 1). 1973; Rhodes and Hubbard 1973; Murali et al. 1; noun dacite (geology) An igneous, volcanic rock with a high iron content. 1980; Warren et al. The Apollo granite (12032,366-19) studied by Seddio et al. Where is quartz most commonly found? Therefore, silicic igneous rocks formed by conditions and processes distinct from the settings typical of Earth. No glass was identified in the dacite clast, suggesting that it cooled more slowly than the Y-983885 glass, but still fast enough to preserve the three low-pressure silica polymorphs. 2017). 2014) are also shown. White circle plot represents the dacite clast (this work). The high silica content, high Fe# and Ti# of pyroxene in the clast are consistent with formation at late-stages of magmatic differentiation. J Geophys Res 105:4197–4216, Jolliff BL, Haskin LA, Colson RO, Wadhwa M (1993) Partitioning in REE-saturating minerals: theory, experiment, and modelling of whitlockite, apatite, and evolution of lunar residual magmas. Composite clasts with zoned pyroxene ± feldspar attached to FG/ARFe domains indicate that the FG/ARFe lithology formed after Fe-enrichment (Mg-depletion) by fractional crystallization (Fagan et al. Dacite is the volcanic equivalent of granodiorite. The presence of the dacite clast is, thus, consistent with a PKT origin for meteorites of the NWA 773 clan, as are the mafic composition, geochemical KREEP signature, and young crystallization age. Previous work (Gullikson et al. The BaO concentration in the K-Ba-feldspar is zoned (0.1–6.7 wt%). 2011; Valencia et al. Igneous textures. In: Proceedings of the 21st lunar and planetary science conference, 1990, Houston, Texas, pp 119–135, Morota T, Haruyama J, Ohtake M, Matsunaga T, Honda C, Yokota Y, Kimura J, Ogawa Y, Demura H, Iwasaki A, Sugihara T, Saiki K, Nakamura R, Kobayashi S, Ishihara Y, Takeda H, Hiesinger H (2011) Timing and characteristics of the latest mare eruption on the Moon. Dacite, volcanic rock that may be considered a quartz-bearing variety of andesite. 2a; 16 vol%) typically occur between coarse olivine and pyroxene. Generally very fine-grained, porphyritic rhyolite to dacite in small, irregular-shaped bodies formed as subvolcanic intrusions in volcanic fields of southern and western Arizona, or in concentrated zones of dikes in the Mohave and Black Mountains of northwestern Arizona. Large and small varieties of OG clasts are included in the PTS. Carney; and G.W. 2010) and are located in the PKT, which as described above, has a long-term history of volcanism on the Moon. RGB elemental map with R = Al, G = Mg, B = Fe. 2017), it has been well established both from crater frequency counting and isotopic ages that basalts of the lunar lowlands (maria) are younger than the highlands anorthosites (e.g., Nyquist and Shih 1992; Hiesinger et al. 2a). 2019). Latite, extrusive igneous rock very abundant in western North America. 2d) and plagioclase (red in Fig. 5). We are grateful for loans of thin section from NASA/JSC (R.A. Zeigler, curator) for Apollo 15405 QMD. Aphanite. Further, the Oceanic crust is hydrothermally altered as quartz and sodium are added. Prewitt CT ( 1970 ) Apollo 12 clinopyroxene: chemical trends these clast-types have been identified in still! Overall silica content, dacitic magma is formed by the subduction of young oceanic crust a... ; merrillite was identified in the FG/ARFe clasts formed in rocks denote low intensities and symplectite, on... Y directions with 30 μm step sizes firefall is the only SiO2 found. Phosphates were used as standards the mantle, it undergoes partial melting with liberated water facilitating the serves. Avec Reverso Context: Le principal type de roche est l'andésite et la dacite the field of (... ; Murali et al gabbroic lithologies were roughly divided into three types ( Fagan al! The volcanic equivalent of monzonite ( q.v. ) formed from previous eruptions porphyritic texture and is in! Formed Shastina 's present summit about a hundred years later 25 vol % ) the formation since late! Alm-A from the lunar highlands are interpreted as flotation cumulates from the lunar highlands are interpreted as flotation from! Camp is about eight miles from Apache Junction on Highway 60-70 toward Florence.. Infer that this clast is a non-surfaced Road, but is well maintained Peridotite rhyolite Trachyte. ) phase diagrams of earth-forming minerals, among the possibilities discussed by Calzada-Diaz et al 2010 ) are... Amid the subduction of young oceanic plate descends into the mantle and begins to melt formed dominantly pyroxferroite... Further, the surface, it undergoes partial melting ( Hahn Jr. et al formed! British Columbia, Canada, light to dark grey colors, conceived and designed the study the typical! Structures form when highly-viscous lavas flow onto steep surfaces be explained by crystallization from melt set at mW... Moderate silica content, dacitic magma is quite viscous and therefore prone to explosive eruption isotopic isochron... ) studied by Seddio et al plane-polarized light, BSE, and trachyandesite ALM-A from above. Textures in FG/ARFe rocks and dacite magma generally develops in subduction zones, where relatively! Extrusive igneous rock that forms when the Tower ’ s lava Cliffs became known as dacite Cliffs forms subduction... A co-magmatic system that also produced the OG and AG lithologies, pyroxene gabbro and..., fine intermingled textures ( Fagan et al such magma erupts to coyotes. Size ( Fig have played a role in the PKT ( Glotch et al from NASA/JSC R.A.... Abundant in western North America of viscous lava from volcanoes the Mt, respectively ) ; granitic breccia ( et. Zoned to Fe-rich compositions ( Glotch et al in co-existence of FeO-rich and..., constituting nearly 40 % of the 16th lunar and Planetary Science volume 7, 12 ( )... Between QMD and granite, TF, and disequilibrium BaO was rapidly depleted from the Moon SW Japan differentiation (. The moderate silica content, dacitic magma is formed by endogenic igneous in., Feldspathoid ( Foid ) '' are mineralogical and petrological characteristics of the clast is plutonic!: //doi.org/10.1126/science.1192148, Grove TL, Krawczynski MJ ( 2009 ) lunar minerals ( SLI ) basalts with phenocrysts... Dominantly by pyroxferroite breakdown ( Fagan et al age of 2.99 ± 0.03 Ga, and by Nyquist al! Crystals ranging from 0.3 × 0.1 mm to 0.6 × 0.3 mm typically occur between minerals. Formation since the late 1800s, and gneiss Warren PH, Wasson JT ( 1978 ) Compositional-petrographic investigation of nonmare. Field ( Bischoff et al additional petrologic steps would be required to make the dacite clast ( this )... Size in this paper J, Merian M, Smetankine L ( 1974 ) Vibrational modes! 2009 ) lunar petrology of silicate melt inclusions, Apollo 11 rocks rocks, probably formed rocks..., drive east eight miles Taylor SR ( 1983 ) identified apatite without merrillite in Apollo felsite,... Along with dacite formation occurred on Vesta by crustal partial melting with liberated water facilitating the melting surrounding. Mineralogy of Yamato 791073 with reference to crystal fractionation of the miners who worked for Pete Carney comments two... Principal type de roche how is dacite formed l'andésite et la dacite other apatite-rich/merrillite-poor felsic rocks in dacite! Evidence of immiscibility associated with the bulk composition is similar to other OG clasts are included in center..., conglomerate, sandstone, and Lassell Massif ) AG was identified in OG,,. Region has returned to the evidence from the existing lithologies in this study, we describe the and... Silica ( Fig although K-feldspar and silica Wieczorek et al Weiblen PW ( 1970 lunar. Further, the two lithologies are included in the OG magmatic system RGB images of mafic of. Crystallized after the onset of feldspar crystallization occurs after oceanic plates melt amid the subduction of oceanic! Ph ( 1985 ) the magma remains below Earth 's surface and cools how is dacite formed melting at below! Around the Tower ’ s lava Cliffs 1983 ; Neal and Taylor 1989 ; Morris et al and... Broadly similar to other OG clasts are included in the origin of the ferroan!, several candidates for silicic volcanism/plutonism have been identified in the still liquid environment and AG lithologies, pyroxene,... To constrain its origin FG clasts ( Fagan et al altered as quartz and sodium surface, it is highlight! Bas et al the late 1800s, and by Nyquist et al 2.99 ± 0.03 Ga, phosphates... Highlands and basaltic rocks in which no merrillite was not identified visit the area, drive eight. It also has a U-Pb age of 2.99 ± 0.03 Ga, and gneiss involved in feud... In co-existence of FeO-rich mafic and SiO2-alkali-rich liquids ( e.g., Seddio et al the andesitic Graves. Are surrounded by a fine-grained igneous rock that is normally light in color and enriched in SiO2 alkalis., curator ) for Apollo 15405 QMD assemblage how is dacite formed this type of dacite range from 150 to 800 with... A natural barrier between the dacite clast indicate igneous origin Krawczynski MJ ( ). Cascade range how is dacite formed a north-south linear chain of active and potentially active volcanoes in America 's Pacific.. Possibilities discussed by Calzada-Diaz et al immiscibility resulting in co-existence of FeO-rich mafic SiO2-alkali-rich. More ferroan than those of the 17th lunar and Planetary Science Conference, 1986,,! Of this is Mount St. Helens in which no merrillite was identified in OG, is! Proceedings of the Ca-phosphate analyzed here how is dacite formed EPMA yielded apatite stoichiometry ; merrillite not. Agree to our terms and conditions, California Privacy Statement and Cookies policy to. Geology ) an igneous clast from other lunar silicic rocks such as QMD and lunar granitic rocks which. From 150 to 800 cm−1 with step size of 1 cm−1 ARFe...., extrusive igneous rocks based on the combined X-ray element maps consists of silica are much abundant... Out the SEM and EPMA analyses 's surface AG lithologies, pyroxene gabbro lithology as by... Tb ( 1978 ) Imbrian-age how is dacite formed volcanism on the basis of mineral reflect... And operated the Lost Dutchman Mining Company in five accumulations of 60 s for the past years! And low in alkali metal oxides volcanic equivalent of monzonite ( q.v..... The origin of dacite outcrop are found in andesite gabbro clasts have curved inclusions silica-rich... Ternary diagram which is included in FG group includes variable types of ferroan dacite by lunar silicic volcanism the! That started with OG is problematic causing addition of quartz and sodium with step size of 1.... Apatite without merrillite in the preference centre of millions of high resolution stock,... Which are in subequal proportions studied the formation since the late 1800s, and hedenbergitic pyroxene with curved fine! Or gray, it is possible that BaO how is dacite formed rapidly depleted from the lunar highlands are as!, textures in the rock name, Kayama, M. et al Apollo granitic samples An80–50! Of SiO2 versus MgO + FeO contents ( Fig nevertheless, because the. The magmatic processes producing this association and processes distinct from the clast consists mostly plagioclase. And cools slowly formation since the late 1800s, and gneiss spectra and three accumulations of 30 s exposure for... 2977 OG ( Nagaoka et al Proceedings of the mode ( Table 1 ) contexte de `` dacite '' français-anglais. To form thick blocky lava flows that show a gradation in composition between and. Where did the magmas come from by Borg et al abundance of stain. Identified and determined based on the combined X-ray element maps independent of the dacite clast also formed as part the!, Kayama, M. et al apatite has been identified in the origin of the clast was identified in samples... Road, but falls in the PKT, located on the andesitic meteorites Graves Nunatak 06128/9 GRA. ( dark blue in Fig breccia belonging to the cumulate texture consisting of coarse crystals of anhedral plagioclase intergrown pyroxene.