(South Ray Crater?) The mineral composition of the quartzite, anorthosite, rhomb porphyry, dacite, quartz diorite and hornfels samples was determined by XRD analysis and is presented as percentages. If the quantity of pyroxene increases in . Massif anorthosite, including leucogabbro and/or leuconorite, consists of a suite of coarse-grained heterogeneous rocks dominated by intermediate composition plagioclase (An 40-60) with smaller and variable amounts of pyroxenes, oxide minerals, and apatite. The lherzolites are upper-mantle rock exposed by faulting. Sixty percent of the fluorine added to the leach remained in the pregnant liq uor; 40 pct was converted to an insoluble form and exited in the tailing. Contact zone between gabbroic anorthosite gneiss and marble. Plagioclase is a very common mineral group, more than half of the Earth's crust is composed of it. It was collected near the Lunar age of 3.5 b.y.
1.2.2 Compound Content. The Central Indian Ridge is mantled with flows of low-potassium basalt of uniform composition. [] suggested that this crust formed very early in lunar history, by crystallization of material rich in Ca-rich feldspar from a global magma ocean.By this model, a hot early Moon was mostly or entirely molten. The composition of Gabbro and Anorthosite consists of mineral content and compound content. The compositions of the spinels produced in the experiments using the hypothetical magnesian suite parent magma are close to those estimated remotely for the pink spinel . anorthosite, composed predominantly of plagioclase laths with intergranular olivine. Mao and Bell (1976) show that the metal composition is the result of reaction. VARIATIONS IN COMPOSITION Hematite in anorthosite. (1979) determined the composition of the basalt clast in 60639 (figure 8). Troctolitic anorthosite clast. Chemistry A lot of chemical and isotopic analyses have been published for 60015 (Tables 1 and 2). 9) near ferrosalite in composition. Modal composition, texture and a limited zonation in plagioclase indicate that Bu-5/5 anorthosite is a nearly perfect adcumulate. The anorthosite clast (Figure 2a) is 1.5 × 0.5 mm in size and consists of 70 vol.% plagioclase and 30% vol.% olivine with minor accessory minerals Al-Ti-chromite and ilmenite. The fine grained, nearly mono mineral composition and light color anorthosite resemble both marble and quartzite in hand specimen. The study area forms a part of the granulite terrane of south India. The petrogenesis of magmatic Fe-Ti oxide ores associated with massif-type andesine anorthosites is investigated through detailed studies of the world-class Tellnes ilmenite deposit (SW Norway), the Grader layered intrusion (Quebec, Canada) and Fe-Ti ores from the Suwalki anorthosite (NE Poland). Thus age, composition and magmatic texture distinguish . ANORTHOSITE: plagioclase only QUARTZ GABBRO: with quartz. Abbreviations: Pl, plagioclase; Opx, orthopyroxene; Cpx . The skarn pyroxene and the pyroxene of the contaminated anorthositic sill are similar to some of the pyroxenes of the normal anorthosite, particularly that (4) of the pegmatitic facies. New age (ca. The lithologies studied are: sodic ferrogabbro, pristine troctolitic anorthosite (67915,26), and granulitic troctolitic anorthosite (67915,67).
anorthosite and leuconorite, similar to the rocks in the western part of the valley, but here dikes and bodies of jotunite, farsundite, and char- nockite cut across the anorthositic and leuconoritic rocks.
The composition and chronology of clasts representing three minor lithologies in consortium breccia 67915 are discussed. High Pressure Phases: HPP may be present and should be looked for! Therefore it isn't really surprising that there is a rock type that is almost . The plagioclase may be labradorite, bytownite, or anorthite. Lunar anorthosites, however, are quite fine-grained.
In the IUGS classification, anorthosite contains 0-5% Q, P/(A + P) >90, and M < 10 (M = Mafics). The particle size distributions for the stone particle samples are presented in Table . The low Ir content shows that it was a pristine volcanic liquid. 72.6~74) (Figure 3) and are enclosed in the plagio-clase. Wood et al. Abstract. (although it is probably older). Oli-vine grains exhibit limited chemical composition (Fo. Small inclusions in other rock types (xenoliths and composition of An >95), sodic anorthosites (An 92-95), mafi c ferroan rocks (plagioclase abundance is still high, typically >80%, with An >95), and mafi c magnesian rocks (plagioclase abundance is >75%, with An >95).
Wikipedia. Most anorthosites formed during Precambrian times. Anorthosite is an igneous monomineralic rock that is composed of plagioclase feldspar (over 90% of the rock is composed of this mineral). interior anorthosite is ferroan and chemically "pristine" ANORTHOSITE - Intrusive igneous, plutonic. Anorthosite is often composed of mineral labradorite which is famous for an iridescent effect called labradorescence. We used the Scanning Electron Microscope (SEM) to analyze the elemental composition of the gabbro, anorthosite, and the intermediate phase (near the contact and within fractures). The composition, petrology and field relations of the lenticles are consistent with their being xenoliths of anorthosite, and inconsistent with other possible origins for Ca and Al rich rocks. Keywords: anorthosite, gabbroic anorthosite, leucotroctolite, plagioclase, layering, magmatic stratigraphy, magma mixing, filter What is Anorthosite? Archean anorthosite plutons 2. The data, from 69 different locations, reveal the widespread existence of virtually pure —100% plagioclase — anorthosite. Warren and Wasson (1977) termed 60025 "pristine" because of its coarse grain size and low meteoritic siderophiles (Ni, Ir). Data obtained in a trace element analysis of some anorthosite and anorthositic fragments are presented. Warren and Wasson (1978) studied the anorthosite clast and reported analyses indicating it is also meteorite-free. This lithology, which is mineralogically and geochemically the most primitive in the LAC, forms dikes and small intrusions that cross cut monzonitic and anorthositic rocks. High-Al gabbro is characterized by high Al2O3 (15-19 wt%), REE patterns with . Hematite in the same meta-anorthosite from Minnesota, which developed in fractures around and inside plagioclase (the large crystals with albite twinning). Lunar anorthosites are light-colored, while some terrestrial anorthosites are dark. These EL can be determined using in-situ trace element compositions from plagioclase and partition coefficients derived for each . Dixon and Papike (1973), Sclar and Bauer (1974) and . Applying this principle throughout the core . Noun (wikipedia anorthosite) (-) (geology) A phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar. and an Ar/Ar bulk composition. %, and Na2O + K2O contents around 5 wt. Or, rather, it is a mixture of pieces from a related sequence of anorthosites, because the mafic minerals vary in composition (Ryder 1982, James et al. A geochemical investigation of the Laramie anorthosite complex determined that monsonite associated with the complex are characterized by positive Eu anomalies and display a regular variation in composition with distance from the monzonite/county rock contact.
The results confirm that reaction between basalt melt and anorthosite can change the composition of the melt so that it precipitates spinel, as shown in the image above. The crystals which show labradorescence are often very large, even pegmatitic (more than an inch in length).
Anorthosite is a coarse-grained, light-coloured containing rich elements of plutonic rock. An alternative approach might be to take the most An-rich composition obtained from any sample, rather than the average, and assume that it represents the nearest approach to the true cumulus .
The chemical formula of pure anorthite is Ca Al 2 Si 2 O 8. For cooler anortho-site, assimilation will produce olivine- and/or pyroxene-bearing rocks. [] and Smith et al. 2.
Template:Refimprove Anorthosite /ænˈɔr/ is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar (90-100%), and a minimal mafic component (0-10%). Intermediate rocks are also characterized by an increased CaO content . cataclastic anorthosite (figure 1). The Sittampundi complex belongs to the metamorphosed Archean layered anorthosite complex. Anorthosite is a phaneritic, intrusive igneous rock which is characterized by a predominance of plagioclase feldspar which is almost 90-100%, and a minimal mafic component. Proterozoic "massif-type" anorthosite plutons 3.
%. Similar in composition to rocks on the moon, anorthosite is a coarse-grained, intrusive igneous rock composed almost entirely of a single mineral—plagioclase feldspar. The composition of the plagioclase in the lamellae is commonly reported to be somewhat more calcic than that of the host anorthosite (Emslie 1975) or even inversely zoned (Owens and Dymek 1995). A coarse-grained crystalline rock consisting mostly of calcic plagioclase (>90%, usually labradorite) with <10% mafics. Figure 1. So the composition of this plagioclase crystal is Ab 38 An 62, which is labradorite. Venus - Venus - Surface composition: A number of the Soviet landers carried instruments to analyze the chemical composition of the surface materials of Venus. This contrasts to previous estimates of 82 to 92 vol% plagioclase . Typical samples sizes are generally 1 . , with an average plagioclase abundance of 93 and 95 wt %, respectively. Anorthite is rare on the Earth but abundant on the Moon. Thin cumulate layers in ophiolites/oceanic crust 5. 1.2.1 Mineral Content. The host orthopyroxene is typically depleted in Al and Si but has unchanged Fe and Mg adjacent to the plagioclase lamellae (Emslie 1975 ).
The Module but was not "oriented" by surface photography. Indeed, only the central peaks of Aitken and Keeler (Figures 11a and 11c) have an anorthosite composition, by the definition of Stöffler et al. Anorthite.
composition of the magmas, which are modelled as equilibrium liquids (EL). Marble (light-
Gabbro, anorthosite, and garnet-bearing lherzolite are exposed in cross fractures, and lherzolite is the bedrock at the center of the ridge. Anorthosite is considerably less abundant than either basalt or granite, but the complexes in which it . These lithologies were presumed to represent samples of the ancient lunar crust. 8 g/cm 3 to define anorthosite, then anorthosite layer -17 in Fig. Compared with bulk composition of the DaG 400 and PCA 02007 feldspathic lunar meteorites , the MAC 88104/05 meteorite is more ferroan and aluminous, indicating that it contains a higher modal ferroan anorthosite clast and mineral component. Major rock types are chromitite-bearing meta-anorthosite, amphibolite, basic granulite, two-pyroxene granulite, leptynite, biotite gneiss and pink granite. It . 2970 Ma), mantle source composition and geodynamic constraints on the Archean Fiskenaesset anorthosite complex, SW Greenland Ali Polat, Robert Frei, Anders Scherstén , Peter W. U. Appel 1.1 Formation. Hematite is isotropic, so it's opaque (black) in both PPL and XPL. Not to be confused with Anorthosite. 1b) is a The unique composition was not recognized in remote sensing data or in the lunar samples previous to this discovery in M 3 data. Because only the relative proportions of a few elements were measured, no definitive information exists concerning the rock types or minerals present. 1.2 Composition. Phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar , with a minimal mafic component (0-10%). 1. Here on Earth the cooling of anorthositic magma bodies took very long time. In Minnesota, anorthosite was intruded into the lowermost lava flows that formed during the opening of the Midcontinent Rift. Several pure anorthosite clasts have been found in the Dhofar samples, and 60015 is an anorthosite with high abundance of plagioclase and uniform composition in comparison with other FAN samples. The composition of plagioclase feldspar in Proterozoic anorthosites is most commonly between An 40 and An 60 . . Mineralogical Mode for 15415 . This implies that the rocks of the Maria and Highlands cooled at different rates from the molten state and so were formed under different conditions.
they are pure solid phases (not mixtures). Anorthosite has a coarse-grained texture due to slow cooling underground.