EucriteMost common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after Monomict, noncumulate (Stannern trend)
Fell May 22, 1808 49° 17′ N., 15° 34′ E.
Following detonations, about 300 stones fell in Jihomoravsky, Czechoslavakia at approximately 6:00 A.M.. Sixty-six of these stones were subsequently recovered, having a combined total weight of ~52 kg, with the largest weighing 6 kg.
Stannern is a moderately equilibrated monomict brecciaType of breccia whose clasts are composed of a single (mono-) rock type, possibly all from a single rock unit (e.g., L6 with L6). Monomict breccias are rare on the Moon because meteoroid impacts tend to mix different kinds of rocks. The example is a terrestrial granite breccia. Image Source: with a degree of metamorphism consistent with type 4 in the metamorphicRocks that have recrystallized in a solid state due to changes in temperature, pressure, and chemical environment. sequence of Takeda and Graham (1991). As with the other Stannern Trend eucritesMost common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after, which are all included in the lower metamorphic types of 1–4, Stannern’s relatively low degree of metamorphism is considered to be indicative of a late lavaHot molten or semifluid rock derived from a volcano or surface fissure from a differentiated and magmatically active parent body. eruption which was not deeply buried thereafter.
Stannern has a composition that defines a separate trend among eucrites, one that is enriched in incompatible elements and exhibits a high Mg# (defined as molar 100×MgO/[MgO+FeO]). This is reflected in its plot on a TiO vs. FeO/MgO diagram, as well as in its major and trace elementSubstance composed of atoms, each of which has the same atomic number (Z) and chemical properties. The chemical properties of an element are determined by the arrangement of the electrons in the various shells (specified by their quantum number) that surround the nucleus. In a neutral atom, the number of ratios. Although the incompatible element abundances for Stannern Trend eucrites are the highest found, they are not linked to the Mg# in the way they are in the Nuevo Laredo Trend eucrites. Instead, the incompatible trace elements have been decoupled from the major elements during in situcrystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. from a residual melt. The composition is analogous to lunar KREEPLunar igneous rock rich in potassium (K), rare-earth elements (REE), phosphorus (P), thorium, and other incompatible elements. These elements are not incorporated into common rock-forming minerals during magma crystallization, and become enriched in the residual magma and the rocks that ultimately crystallize from it. basalts produced during late-stage fractional magmatism.
An alternate petrogenesis of the Stannern Trend eucrites has been proposed by Barrat et al. (2007). They envisage a region of 10% partial meltingAn igneous process whereby rocks melt and the resulting magma is comprised of the remaining partially melted rock (sometimes called restite) and a liquid whose composition differs from the original rock. Partial melting occurs because nearly all rocks are made up of different minerals, each of which has a different melting at depth within the equilibrated eucritic crustOutermost layer of a differentiated planet, asteroid or moon, usually consisting of silicate rock and extending no more than 10s of km from the surface. The term is also applied to icy bodies, in which case it is composed of ices, frozen gases, and accumulated meteoritic material. On Earth, the, and the subsequent assimilation of a portion of this crustal partial melt by an ascending magmaMolten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. plume with Main Group composition in a ratio of approximately 15:85, respectively. They demonstrate that this would result in the enrichment of the incompatible trace elements, including REEOften abbreviated as “REE”, these 16 elements include (preceded by their atomic numbers): 21 scandium (Sc), 39 Yttrium (Y) and the 14 elements that comprise the lanthanides excluding 61 Promethium, an extremely rare and radioactive element. These elements show closely related geochemical behaviors associated with their filled 4f atomic orbital., similar to that observed in Stannern and other members of this trend, along with the corresponding negative anomalies observed for Eu, Sr, and Be. This model is also consistent with other elemental abundances; the increased W content in Stannern Trend eucrites is consistent with the behavior of W as an incompatible element when it is associated with a metal-free, crustal partial melt. The degree of variation observed among non-cumulate eucrites is commensurate with the degree of crustal melt contamination they experienced during ascent. Significant complications with the relationships among established chemical trends were elucidated by Castle et al. (2012), and it was concluded that each geochemical trend may have originated on separate but similar parent bodies.
Stannern has an unusually young crystallization age for eucrites of 4.434 b.y., which is consistent with a late-stage initiation caused by an impact event. Another impact event occurred ~3.7 b.y. ago, which reset some isotopic clocks such as Ar–Ar. This event corresponds to the Late Heavy BombardmentPeriod between ~4.0 to 3.8 Ga ago when the Moon and other objects in the Solar System were pounded heavily by wayward asteroids. The evidence for the Late Heavy Bombardment (LHB) includes the lunar maria basins and similar structures elsewhere, such as the Caloris Basin on Mercury and the great period on the Moon ~3.8–4.1 b.y. ago. Both lunar and VestaThird largest and fourth brightest asteroid; it was discovered in 1807 by Heinrich Olbers and named for the ancient Roman goddess of the hearth. 4 Vesta has a basaltic surface composition and an average density not much less than that of Mars. Evidently lava once flowed here indicating that the chronometer resetting events likely represent the same population of impactors, with impacts on Vesta continuing for a longer time. Stannern has a cosmic-ray exposure ageTime interval that a meteoroid was an independent body in space. In other words, the time between when a meteoroid was broken off its parent body and its arrival on Earth as a meteorite - also known simply as the "exposure age." It can be estimated from the observed effects of 35.1 (±0.7) m.y.
The Stannern Trend comprises a small number of eucrites including the falls of Stannern, Bouvante, and Pomozdino, together with the Saharan findMeteorite not seen to fall, but recovered at some later date. For example, many finds from Antarctica fell 10,000 to 700,000 years ago. NWA 4523 and several Antarctic finds; the newly found eucriteMost common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after Bluewing 001 also shares close similarities with this trend. The specimen of Stannern shown above is a 2.58 g partial slice with fusion crustMelted exterior of a meteorite that forms when it passes through Earth’s atmosphere. Friction with the air will raise a meteorite’s surface temperature upwards of 4800 K (8180 °F) and will melt (ablate) the surface minerals and flow backwards over the surface as shown in the Lafayette meteorite photograph below. along the upper edge.
Thanks to Shawn Alan for sharing the following historical account of Stannern: Encyclopaedia Metropolitana; or, Universal Dictionary of Knowledge, Volume XXV, edited by Rev. Edward Smedley, Rev. Hugh James Rose, and Rev. Henry John Rose (London, 1845)
STONES, METEORIC. by William Hallows Miller (p. 82)
The next event of the kind which we shall describe deserves notice on account of the care with which the circumstances attending it were investigated by von Schreibers and von WidmanstattenCharacteristic cross-hatched pattern visible on the surface of octahedrites, pallasites and even large metal blebs in chondrite melts and mesosiderite nodules after polishing and etching with an acid solution like nital (nitric acid in solution with ethanol). The acid will preferentially etch the iron based on its nickel content - on the spot, a week after it occurred. At Stannern, a small town in Moravia about ninety-two miles from Vienna on the post road to Prague, between half-past five and six A.M. on the 22d of May, 1808, the air, which had previously been clear, was suddenly obscured by a thick mist. A very loud explosion was then heard, followed by fainter reports and a noise like that of carriages drawn over a rough pavement. These sounds appeared to proceed from a point moving from north-west to south-east, and lasted about eight minutes. In the mean time a number of stones fell on the ground, scattering themselves over an oval surface about eight English miles and a half long, from north north-west to south south-east, and three miles and a quarter wide, having Stannern for its middle point. They formed three principal groups: one in and about Stannern; another, containing two of the largest stones, two of which weighed sixteen and fourteen pounds respectively, at the north end of the oval; the third, composed of the smallest, at the south end. Hence, as at L’Aigle, the largest stones appear to have fallen first. They were found to be hot a short time after their 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. One of them weighing a little more than four pounds made a hole two feet deep in a newly ploughed field. The number of stones actually gathered amounted to sixty-six, and their joint weight to one hundred and eighteen pounds avoirdupois. After the first explosion the mist became so dense that objects could not be discerned at the distance of twelve paces. It extended thirty-seven miles to the south, and nearly half that distance in other directions, and did not wholly disappear for four hours. About the time the explosion was heard, a fire-ball emitting sparks and leaving a train of fire behind it was seen from Triesch, four miles to the west of Stannern, and also from the Bohemian frontier, twenty miles to the north. The stones have a very uneven surface coated with a pitch-black crust. Their interior resembles a fine-grained porous white sandstone traversed by veins of a greyish substance. They contain small quantities of sulphuret of iron and oxide of iron, but no iron in a metallic state, and do not affect the magnetic needle. Their specific gravityRatio of the density of a substance to the density of a standard substance. The standard is usually liquid water for solids and liquids and air for gases. The density of liquid water under typical conditions is ~1000 kg/m3. The density of air at room temperature near the surface of varies from 2.95 to 3.16, which is less than that of most other meteoric stones. According to the analysis of Moser, a portion of one of them contained, in 100 parts, silicaSilicon dioxide, SiO2. 46.25, lime 12.12, alumina 7.62, magnesia 2.50, oxide of iron 27, oxide of manganese 0.75, with traces of chrome, water, sulphur, and neutral hydrochlorates.