We are grateful for loans of thin section from NASA/JSC (R.A. Zeigler, curator) for Apollo 15405 QMD. 2013). 2c). 2013). (2014) and Valencia et al. RGB elemental map with R = Al, G = Mg, B = Fe. These three gabbros (OG, AG, FG) formed from a co-magmatic sequence of crystallization (Fagan et al. All Fe is calculated as Fe2+. Anhedral crystals of plagioclase (red in Fig. The incorporating officers were: J. Trincano; Carney’s brother, T.G. Where is quartz most commonly found? The FeO content in plagioclase (1.15 wt%) is higher than those in the Apollo granite/felsite (0.06–0.79 wt%: Warren et al. 2003; Jolliff et al. Quartz was identified only where silica is intergrown with K-Ba-feldspar, whereas cristobalite and tridymite were found where the silica has a more massive texture (Fig. Some of these tunnels are more than three hundred feet in length. noun dacite an igneous, volcanic rock characteristically light in colour with relatively high silica content 3; noun dacite A volcanic rock resembling andesite but containing free quartz. Meteorit Planet Sci 54:2083–2115, Warren PH (1985) The magma ocean concept and lunar evolution. In: Proceedings of the 21st lunar and planetary science conference, 1990, Houston, Texas, pp 137–150, Salpas PA, Taylor LA, Lindstrom MM (1987) Apollo 17 KREEPy basalts: Evidence for the non-uniformity of KREEP. Compositions of ARFe clasts in NWA 773 (Fagan et al. 2019). 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. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. Silica occurs as (1) massive to elongate grains up to 550 μm in long diameter (labeled Si(1) in Fig. Dacite definition is - an extrusive rock that is sometimes partly glassy and is composed of plagioclase and quartz with biotite, hornblende, or pyroxene. Fe-oxides occur in trace abundances in the OG clast, and are located between coarse minerals. In contrast to basalts and anorthosites, granitic rocks are rare on the Moon, comprising well under 0.1% by mass of the Apollo collection as reported by Seddio et al. IUGS Classification of volcanic rocks (Streckeisen 1979). (2015), the high-temperature polymorphs of silica have more open structures than quartz and thus, may accommodate elevated concentrations of minor elements. Quartz is the most abundant and widely distributed mineral found at Earth’s surface. Am Mineral 101:2312–2321, Gust DA, Arculus RJ (1986) Petrogenesis of alkalic and calcalkalic volcanic rocks of Mormon Mountain volcanic field, Arizona. 2019). Dacite is a fine-grained igneous rock that is normally light in color. 2011; Snape et al. 1974; Ling et al. Nevertheless, because of the moderate silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. Carney believed the Dacite Cliffs contained a fortune. (1993) reported apatite but no merrillite in Apollo felsite 14161,7269, and likewise, Warren et al. 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. The difference in alkalis reflects the lower mode of K-feldspar and the low albite content (Ab11) of plagioclase in comparison with the Apollo granitic samples and in the terrestrial andesite/dacite. Prog Earth Planet Sci 7, 12 (2020). 2006; Zeigler et al. Slow cooling facilitates the growth of large mineral crystals in the rock. 1980; Warren et al. The clast consists mostly of plagioclase and pyroxene, which are in subequal proportions. Am Mineral 84:821–837, Jolliff BL, Gillis JJ, Haskin LA, Korotev RL, Wieczorek MA (2000) Major lunar crustal terranes: surface expressions and crust-mantle origins. 2009), Northwest Africa 11119 (NWA 11119; Srinivasan et al. 1988; Papike et al. Petrological descriptions of each lithology in the PTS are summarized below. Although much of the Tower’s geologic story is agreed upon, theories differ on certain details. On Earth, igneous processes in diverse geochemical settings have resulted in wide compositional ranges of mafic to silicic rocks which form the crust. 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. Conforms to HazCom 2012/United States Page 1 of 8 Safety Data Sheet Dacite Section 1. In the Raman maps, the integral intensities of the main bands for each mineral were extracted from the spectral data of each measuring point to observe distributions of minerals. 2003; Jolliff et al. 1970; Fagan et al. The authors declare that they have no competing interests. 2005). 5 and 6). In: Proceedings of the 7th lunar science conference, 1976, Houston, Texas, pp 1723–1740, Ryder G, Martinez RR (1991) Evolved hypabyssal rocks from station 7, Apennine front, Apollo 15. Haldar, in Platinum-Nickel-Chromium Deposits, 2017. Historically this precipice has served as a natural barrier between the lower desert and the mountainous region of the Superstition Wilderness. Total alkali-silica (TAS) diagram (Le Bas et al. 1983; Salpas et al. Aphanite. Silverthorne. As a whole, the NWA 773 clan consists of a coarse-grained regolith breccia with variable abundances of gabbroic and basaltic lithologies (Valencia et al. Part of Oceanic crust is hydrothermally altered causing addition of quartz and sodium. HN, TF, and MK analyzed the data and helped in their interpretation. 1983; Morris et al. Today these cliffs dominate the region around Don’s Camp. These elongated flow structures form when highly-viscous lavas flow onto steep surfaces. Warm colors (red) indicate high peak intensities and dark (blue) colors denote low intensities. The presence of olivine phenocrysts and fine-grained groundmass consisting of pyroxene and plagioclase of this basaltic clast are similar to the olivine-phyric basalt (OPB) described by Valencia et al. 2011; Valencia et al. 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. Fayalite, silica, and hedenbergitic pyroxene also occur in the dacite clast, but feldspars also are abundant in the clast, and the textures and formation processes are distinct. 2014) are also shown. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. 3c, d. In this part of the clast, fine pyroxene crystals (< 100 μm; Px fine1 in Fig. Earth Planet Space 54:217–229, Hawke BR, Lawrence DJ, Blewett DT, Lucey PG, Smith GA, Spudis PD, Taylor GJ (2003) Hansteen alpha: a volcanic construct in the lunar highlands. Mafic mineral crystals in the silicic clast are much finer-grained (0.3 mm in maximum dimension) than those of three gabbros (OG, AG, FG), and similar in size to olivine phenocrysts in the OPB. Olivine and pyroxene in the clast have high Fe/Mg ratios (olivine Fe# > 99, pyroxene Fe# > 99; with Fe# = molar Fe/(Fe + Mg) × 100), suggesting crystallization from a residual liquid after fractionation of more magnesian silicates. 1980; Ryder and Martinez 1991; Jolliff et al. The dacite clast plots between QMD and lunar granitic rocks in terms of SiO2 versus MgO + FeO contents (Fig. dacite - a grey volcanic rock containing plagioclase and quartz and other crystalline minerals oligoclase, plagioclase - any of a series of triclinic feldspars that form rocks volcanic rock - extrusive igneous rock solidified near or on the surface of the Earth Nonetheless, the presence of granitic rocks is an indicator of compositional evolution by igneous processes in the Moon. Icarus 211:101–113, Marvin UB, Lindstrom MM, Holmberg BB, Martinez RR (1991) New observations on the quartz monzodiorite-granite suite. Meteorit Planet Sci 45:1929–1947. The polished thin section (PTS) of NWA 2727 was investigated by a combination of petrographic and chemical microanalyses including electron microprobe spectroscopy and scanning electron microscope imaging and mapping. © 2021 BioMed Central Ltd unless otherwise stated. 2b; 35 vol%) occurs as elongate-appearing crystals, with grain sizes up to 2.1 × 0.5 mm. Oceanic crust is hydrothermally altered causing addition of quartz and sodium. 1). 1991; Snyder et al. Although FG is variable in mineral assemblage, mineral zoning, and texture, the ferroan composition of mafic minerals is common in the FG lithology. Only data with analytical totals of 98–102 wt% with close fits to the mineral stoichiometries were selected in this paper. Share. Dacite usually forms as an intrusive rock such as a dike or sill. The following ferroan lithologies are included in FG group (Valencia et al. 2010). 2c), which are characteristic of the pyroxene gabbro lithology as defined by Fagan et al. 1978; Salpas et al. On the other hand, the possibility that the dacite might have formed by immiscibility of other magmatic system involving large-scale gravity separation of silica-rich melt from a parent melt remains plausible in view of the fact that the dacite composition plots on the edge of the miscibility gap of Roedder (1951) (see Appendix). Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Information block about the term. The bulk composition of the dacite clast is compared with those of other clast lithologies (OG, AG, FG, OPB) in NWA 773 clan and the Apollo quartz monzodiorite (QMD), granite, and felsite in Table 4. 1991; Marvin et al. Today the region has returned to the coyotes, desert and the wind. 2006; Zeigler et al. 1977; Quick et al. Large olivine crystals with pyroxene and plagioclase filling interstices indicate the cumulate texture. Dacite Dacite, from Dacia, a Roman province, Transylvania, Romania, is a volcanic rock that may be considered a quartz-bearing variety of andesite. Thus, the dacite clast, like other apatite-rich/merrillite-poor felsic rocks, probably formed in setting that was relatively volatile-rich on the Moon. Geochim Cosmochim Acta 56:2213–2234, Nyquist LE, Shish C-Y, Reese YD, Irving AJ (2009) Sm-Nd and Rb-Sr ages for Northwest Africa 2977, a young lunar gabbro from the PKT. The presence of the dacite lithology provides additional support for an origin in or around PKT for meteorites of the NWA 773 clan, and for complex igneous activity in PKT region. When such magma erupts to the surface, it creates a fine-grained rock that crystallizes quickly. 2b; 36 vol%) shows some euhedral crystal faces, with grain sizes ranging from 0.3 to 2 mm across. S.K. Domes undergo various processes such as growth, collapse, solidification and erosion.. Lava domes grow by endogenic dome growth or exogenic dome growth. The host rock is dacite –quartz-feldspar porphyry intruded into volcanic andesite, andesite breccia, conglomerate, sandstone, and tuff. The glass in Y-983885 apparently represents a case of silica-enrichment followed by rapid cooling distinct from the origin of the dacite clast in NWA 2727. The presence of ferroan mafic silicates, silica, feldspar, and Ca-phosphates are common to the FG/ARFe lithology (combining the classification schemes of Fagan et al. Latites contain plagioclase feldspar (andesine or oligoclase) as large, single crystals (phenocrysts) in a fine-grained Mineral Petrol 46:1–22, Lindstrom MM, Marvin UB, Vetter SK, Shervais JW (1988) Apennine front revisited: diversity of Apollo 15 highland rock types. (2019), the origin of the dacite clast is broadly similar to the origin of the FG/ARFe lithology. The clast is 4.4 × 4.3 mm in size in this PTS (Fig. Latite, extrusive igneous rock very abundant in western North America. Meteorit Planet Sci 44(S7):A15–A229, Papike J, Taylor L, Simon S (1991) Lunar minerals. MK carried out Raman spectroscopy. Oceanic crust is hydrothermally altered causing addition of quartz and sodium. Earth Planet Sci Lett 451:149–158, Snyder GA, Taylor LA, Liu Y-G, Schmitt RA (1992) Petrogenesis of the western highlands of the Moon: evidence from a diverse group of whitlockite-rich rocks from the Fra Mauro formation. As described above, the high Fe# of mafic silicates and the general mineral assemblage of the dacite are similar to the glass and feldspar + silica-bearing immiscible inclusions in FG/ARFe rocks. 2018). Anorthosites of the lunar highlands are interpreted as flotation cumulates from the lunar magma ocean (Warren 1985). Pyroxene quadrilateral compositions from the silicic clast (this work). Silverthorne wrote daily while he sat beneath the towering Dacite Cliffs. (2005), the Si, Al, K-rich glass was derived from rapid cooling of an immiscible felsic liquid that separated from parent liquid before the crystallization of silica (Arai et al. 2013). Raman bands of tridymite at 207, 301, 351, and 432 cm−1, cristobalite at 228 and 411 cm−1, and quartz at 199 and 464 cm−1 (e.g., Etchepare 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. noun. All pyroxenes in the silicic clast are more ferroan than those in the ARFe clasts analyzed by Fagan et al. The CPB clasts have anhedral quartz single crystals on the order of ≤ 40 μm across and have abundant pyroxene + feldspar-rich groundmass, distinct from the dacite clast (Kayama et al. In both cases, the clast is similar to some of the terrestrial ferroan andesite/dacite samples. Geol Soc Am Bull 125:1079–1113, Bunch TE, Wittke JH, Korotev RL, Irving AJ (2006) Lunar meteorites NWA 2700, NWA 2727 and NWA 2977: Mare basalts/gabbro breccias with affinities to NWA 773. Dacite Dacite is a felsic extrusive rock, intermediate in composition between andesite and rhyolite. 2017; Valencia et al. Search for the legendary Lost Dutchman Goldmine. 2017; Valencia et al. 7). 9c. PubMed Google Scholar. 2013); granitic breccia (Morris et al. 9–11 of FG-A, FG-B, FG-C, FG-D, FG-F, FG-I). Dacitic magmas tend to erupt explosively, thus also ejecting abundant ash and pumice. The coexistence of multiple polymorphs of silica in the NWA 2727 dacite clast distinguishes the dacite from the Apollo 12032,366-19 granite, though the quartz in the Apollo 12 granite has a hackle pattern suggestive of contraction after crystallization and may have recrystallized from a higher-temperature silica polymorph (Seddio et al. 2019): olivine gabbro (OG, an olivine-pyroxene-plagioclase-rich rock); anorthositic gabbro (AG, a plagioclase-rich rock with some pyroxene); and ferroan gabbro (FG, a group of lithologies all having high Fe# = molar Fe/[Fe + Mg]; see below). 1988); QMD (Taylor et al. Lunar basalts form by volcanic eruptions from the interior after partial melting in the mantle and are concentrated on the nearside of the Moon, in and near the Procellarum-KREEP Terrane (PKT, with KREEP indicating enrichment in K, rare earth elements, and P) (Jolliff et al. https://doi.org/10.1186/s40645-020-0324-8, DOI: https://doi.org/10.1186/s40645-020-0324-8. Representative Raman spectra of a tridymite and cristobalite and b quartz in the silicic clast. However, the low Ab-content of plagioclase and high Fe# of mafic silicates of the dacite clast are distinct from the terrestrial and most of the lunar samples plotted in Fig. 2016). The highly ferroan and silica-rich composition of dacite clast formed at least in part by crystallization from residual liquid after Mg-depletion by fractional crystallization of a parental melt. The dacite clast is isolated in breccia: there are no spatial or zoning relationships that show a genetic relationship with lithologies of the NWA 773 clan OG magmatic system. 2003, and grouped within the FG lithology of Valencia et al. QAPF diagram. 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. Some of the silica in the clast is intergrown with feldspars, suggesting co-crystallization of silica with plagioclase and alkali feldspars during stages of crystallization from liquid. (2018). If the clast has disproportionately high modes of silica or low modes of feldspars, then the calculated Na2O + K2O vs. SiO2 content could fall along the lunar variation trend shown in Fig. Comparisons of bulk compositions between the silicic clast (Dacite; this work), Apollo evolved samples and several terrestrial andesite/dacites (see text): a SiO2 vs. MgO + FeO, b SiO2 vs. Al2O3, c SiO2 vs. Na2O + K2O, d SiO2 vs. Mg#. He, too, was a dreamer. statement and An igneous clast from the Northwest Africa 773 (NWA 773) clan of lunar meteorites formed by silicic volcanism on the Moon. Dacite is primarily associated with andesite and trachyte and forms lava flows, dikes, and sometimes massive intrusions in the centres of old volcanoes. (2015) observed hackle fracture patterns in quartz in Apollo samples of lunar granites, and inferred that the fractures formed by a volume reduction during recrystallization from cristobalite or tridymite to quartz. Igneous textures. 2018). 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. 3c), and one coarser crystal (210 μm × 140 μm) occurs near the bottom of the clast (Px crs in Fig. 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. Nature 477:70–72, Borg LE, Gaffney AM, Shearer CK, DePaolo DJ, Hutcheon ID, Owens TL, Ramon E, Brennecka G (2009) Mechanisms for incompatible-element enrichment on the Moon deduced from the lunar basaltic meteorite Northwest Africa 032. Prior to 1930 this cliff was known as Lava Cliffs. The FG group includes variable types of ferroan lithologies (described above; also see Fagan et al. Privacy Several candidates for silicic volcanism/plutonism have been identified in the PKT (e.g., Gruithuisen Domes, Hansteen alpha, Lassell Massif). However, the high silica concentration and dominance of apatite as the main Ca-phosphate (no merrillite was identified) are distinct from the FG/ARFe clasts.