Angrite

Type of evolved achondriteAn achondrite is a type of stony meteorite whose precursor was of chondritic origin and experienced metamorphic and igneous processes. They have a planetary or differentiated asteroidal origin where the chondritic parent body reached a sufficient size that through heating due to radioactive decay of 26Al (aluminum isotope) and gravitational meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and that represent some of the earliest stages of asteroidal differentiationA process by which a generally homogeneous chondritic body containing mostly metal, silicates and sulfides will melt and form distinct (differentiated) layers of different densities.   When the melting process continues for a long enough period of time, the once chondritic body will re-partition into layers of different composition including and magmatism in our solar systemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids.. Angrites are named for the Angra dos Reis meteorite, which fell in Rio de Janeiro, Brazil, in early 1869. They are basaltic (maficOne of the two broad categories of silicate minerals, the other being felsic, based on its magnesium (Mg) and/or iron (Fe) content. Mafic indicates silicate minerals that are predominantly comprised of Mg and/or Fe.The term is derived from those major constituents: Magnesium + Ferrum (Latin for iron) + ic (having) rocks, often containing porous areas, and vesicles that can sometimes reach 2.5 cm in diameter. They are thought to have formed on one of the earliest differentiated asteroids, and generally fallMeteorite seen to fall. Such meteorites are usually collected soon after falling and are not affected by terrestrial weathering (Weathering = 0). Beginning in 2014 (date needs confirmation), the NomComm adopted the use of the terms "probable fall" and "confirmed fall" to provide better insight into the meteorite's history. If into one of the following two categories: coarse-grained plutonicGeology: Igneous intrusive body that forms when magma is injected into host rocks and solidifies. Plutons occur in the crust of asteroids undergoing differentiation or planets. Named after Pluto, the Roman god of the underworld. Plutonic rocks are the rocks found within a pluton. Astronomy: Category of planet including all angrites or fine-grained volcanicIgneous rock that forms from cooling magma on the surface of a planet or asteroid. (quenched) angrites. Due to the wide distribution of cosmic ray exposure ages, the angrite parent bodyThe body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. (or bodies) may still exist. By comparing the reflectance spectra of angrites to that of several main beltBelt located between 2.12 and 3.3 AU from the Sun and located between the orbits of Mars and Jupiter containing the vast majority of asteroids. The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such asteroids, three potential parent bodies have been identified: 5261 Eureka (~1.3 km across), 289 Nenetta and 3819 Robinson. Siderophile elementLiterally, "iron-loving" element that tends to be concentrated in Fe-Ni metal rather than in silicate; these are Fe, Co, Ni, Mo, Re, Au, and PGE. These elements are relatively common in undifferentiated meteorites, and, in differentiated asteroids and planets, are found in the metal-rich cores and, consequently, extremely rare on depletion and remnant magnetization suggest that the original parent body was >70 km in diameter before it was broken apart.¹

Angrites are notable for their depletion in silicaSilicon dioxide, SiO2. and volatileSubstances which have a tendency to enter the gas phase relatively easily (by evaporation, addition of heat, etc.). alkali (Na and K), and enrichment in calcium. Their mineralogy generally consists of almost equal proportions of Ca-rich plagioclaseAlso referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite (An_99.6), high Al-Ti diopside pyroxeneA class of silicate (SiO3) minerals that form a solid solution between iron and magnesium and can contain up to 50% calcium. Pyroxenes are important rock forming minerals and critical to understanding igneous processes. For more detailed information, please read the Pyroxene Group article found in the Meteoritics & Classification category. (fassaite), and a distinctive Ca‐rich olivineGroup of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion (kirschsteinite). Surprisingly, Angra dos Reis, differs from the others and is composed almost entirely (93 vol%) of pyroxene.¹

Angrites are the most ancient igneous rocks known in our solar systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with. Various chronometers based on isotopes of Mn-Cr, Hf-W and U-Pb have been used to successfully validate the starting crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. age of angrites to 4563.2 ± 0.3 Ma, i.e., 4.1 Myr after CAIsSub-millimeter to centimeter-sized amorphous objects found typically in carbonaceous chondrites and ranging in color from white to greyish white and even light pink. CAIs have occasionally been found in ordinary chondrites, such as the L3.00 chondrite, NWA 8276 (Sara Russell, 2016). CAIs are also known as refractory inclusions since they formation² (condensation from the solar nebulaThe primitive gas and dust cloud around the Sun from which planetary materials formed.). Crystallization continued for another 8 Myr after that. As would be expected, the volcanic angrites crystallized first and quickly over the first ~2 Myr, while the plutonic angrites cooled second and over a much longer period of ~6 My.