Zakłodzie (Zaklodzie)

Primitive Enstatite AchondriteUsed in past as synonym for Aubrites. Present definition from the Meteoritical Bulletin states that this rare class is an "enstatite-rich  achondrite  that has not yet been classified into a group". or
EL melt rock or E chondriteChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such IMB
(E achondrite-ung in MetBull 84)

Found September 1998
50° 45′ 46′ N., 22° 51′ 58′ E. Zakłodzie is an 8.68 kg enstatite-rich 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 Al (aluminum isotope) and gravitational that was found beside a dirt road by Mr. Stanislaw Jachymek, a mineralInorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous and fossil collector. This extremely weathered 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 with remnant 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. was found about 40 km west of Zamosc, Poland, near the small village of Zakłodzie. Its meteoritic nature was first verified by Dr. Lukasz Karwowski of the Silesian University Geology Department. The mineralogical analysis and classification were performed at the Max-Planck-Institut für Chemie (Dr. Frank Wlotzka), the Polish Geological Institute (Dr. Marian Stepniewski), and the Bartoschewitz Meteorite Laboratory (Rainer Bartoschewitz).

Zakłodzie has a fine-grained, granular texture similar to that of several other recrystallized EL chondritesChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such, including Happy Canyon, MIL 090807, and Ilafegh 009 (Boesenberg et al. (2014). It is composed of ~60 vol% orthoenstatite with ~20 vol% Si-bearing FeNi-metal, along with ~10 vol% of both troiliteBrass colored non-magnetic mineral of iron sulfide, FeS, found in a variety of meteorites. and feldsparAn alumino-silicate mineral containing a solid solution of calcium, sodium and potassium. Over half the Earth’s crust is composed of feldspars and due to their abundance, feldspars are used in the classification of igneous rocks. A more complete explanation can be found on the feldspar group page.. It also contains accessory schreibersiteNi-Fe phosphide mineral, (Fe,Ni)3P, yellowish in color and predominantly found in iron and stony-iron meteorites. Schreibersite can also be found in a variety of other meteorites including some acapulcoites, aubrites, enstatite chondrites and achondrites, lunars, ureilites, winonaites and a smattering of other meteorite types like CM, CO and CB. Schreibersite, tridymiteSilica group mineral in which the tetrahedra occur in sheets. Tetrahedra alternately point up or down to share oxygen with tetrahedra of other sheets, forming six-sided rings perpendicular the sheets. Tridymite has a fairly open structure and accommodates Na+, K+ and Ca2+; charge balance is achieved by Al3+ ↔ Si4+., cristobaliteHigh temperature polymorph of silicon dioxide (SiO2). Has the same chemical composition as coesite, stishovite, seifertite and tridymite but possesses a different crystal structure. This silica group mineral occurs in terrestrial volcanic rocks, martian and lunar meteorites, chondrites and impact glasses like Libyan Desert Glass. Cristobalite has a very open, oldhamiteMn-Ca sulfide, (Mn,Ca)S, is a pale to dark brown accessory mineral found in minor amounts in highly reduced meteorites such as many enstatite chondrites, and some aubrites and enstatite achondrites. Oldhamite in enstatite chondrites likely formed by solar nebular gas condensation. CaS Oldhamite was also found in the most fresh, albandite, amphibole, and ubiquitous graphiteOpaque form of carbon (C) found in some iron and ordinary chondrites and in ureilite meteorites. Each C atom is bonded to three others in a plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons. The two known forms of graphite, α (hexagonal) and β (rhombohedral), have. Keilite [(Fe,Mg)S], a mineral phase associated with strongly reducingOxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons,  while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants conditions, has been observed in Zakłodzie (Karwowski et al., 2007; Uribe et al., 2017). Sinoite, a silicon nitride associated with crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. of an impact melt, has been identified as inclusions within the keilite. While there are no visible chondrulesRoughly spherical aggregate of coarse crystals formed from the rapid cooling and solidification of a melt at  ~1400 ° C. Large numbers of chondrules are found in all chondrites except for the CI group of carbonaceous chondrites. Chondrules are typically 0.5-2 mm in diameter and are usually composed of olivine, some elongated enstatiteA mineral that is composed of Mg-rich pyroxene, MgSiO3. It is the magnesium endmember of the pyroxene silicate mineral series - enstatite (MgSiO3) to ferrosilite (FeSiO3). grains arranged in an oval configuration might represent extremely metamorphosed relict chondrules. There are abundant metalElement that readily forms cations and has metallic bonds; sometimes said to be similar to a cation in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. A diagonal line drawn flakes, interspersed gas vesicles, and various light and dark inclusions present as well. While 0.1–4 mm (rarely as large as 9 mm; Przylibski et al., 2011) spherical graphite nodules containing metal inclusions (and vice versa), are present in the innermost portion of the meteorite, finely dispersed graphite producing a dark coloration occurs in the outer portion. Raman analysis shows that the graphite has a semi-ordered to ordered structure.

Zakłodzie shows similarities to the QUE 94204 pairing group. The bulk composition and petrography of both meteorites, especially the zoned and skeletal feldspar, unequilibrated anorthiteRare compositional variety of plagioclase and the calcium end-member of the plagioclase feldspar mineral series with the formula CaAl2Si2O8. Anorthite is found in mafic igneous rocks such as anorthosite. Anorthite is abundant on the Moon and in lunar meteorites. However, anorthite is very rare on Earth since it weathers rapidly contents in the feldspar, and polysynthetically twinned enstatite grains, suggests a possible rapid cooling at some stage. Moreover, the retention of abundant opaque phases, FeNi-metal surrounding enstatite laths, and relict chondrules, are all features consistent with impact melting and rapid cooling. In addition, the mineral keilite is only stable in conditions of rapid cooling of impact melts. All of these features taken together are considered by some investigators (Burbine et al. [2000], Keil [2007], and Keil and Bischoff [2008]) to best represent a classification for Zakłodzie as an E chondrite impact-melt brecciaWork in Progress ... A rock that is a mechanical mixture of different minerals and/or rock fragments (clasts). A breccia may also be distinguished by the origin of its clasts: (monomict breccia: monogenetic or monolithologic, and polymict breccia: polygenetic or polylithologic). The proportions of these fragments within the unbrecciated material.

This classification is contrary to that proposed by Przylibski et al. (2005), who argue that rapid cooling from an impact-melt is inconsistent with the characteristics of Zakłodzie (e.g., cumulateIgneous rock composed of crystals that have grown and accumulated (often by gravitational settling) in a cooling magma chamber. texture, relict chondrules, triple junctions, slow cooling rate, silicaSilicon dioxide, SiO2. content, and 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 enrichment). They believe instead that the features best fit a scenario in which Zakłodzie experienced initial slow cooling during cumulate processes, all the while undergoing fractional crystallizationA crystallization process in which minerals crystallizing from a magma are isolated from contact with the liquid. It is a key process in the formation of igneous rocks during the process of magmatic differentiation. Also known as crystal fractionation. of forsteritePure* magnesium end-member (Mg2SiO4) of the olivine solid solution series and an important mineral in meteorites. When magnesium (Mg) is completely substituted by iron, it yields the the pure Fe-olivine end member, fayalite (Fe2SiO4). The various Fe and Mg substitutions between these two end-members are described based on their forsteritic (Fo) sequentially forming protoenstatite ⇒ orthoenstatite ⇒ clinoenstatite, and also silica, feldspar, FeNi-metal, and sulfides. This rock is the residual material resulting from rapid 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 of enstatite chondriteType of meteorite high in the mineral enstatite and also referred to as E-chondrites. Although they contain substantial amounts of Fe, it is in the form of Ni-Fe metal or sulfide rather than as oxides in silicates. Their highly reduced nature indicates that they formed in an area of the material. They propose that Zakłodzie subsequently experienced a rapid cooling phase as it was entrained in a rising magmaMolten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. column, assimilating chondrule-bearing rock as it rose. Following this stage, the low-melting-point components such as feldspar, metal, and sulfides were partially remelted in a subsequent impact event. Given this scenario, Przylibski et al. (2005) favor a classification for Zakłodzie as a primitive enstatite achondrite. In addition, they favor this classification for the enstatite meteorites Happy Canyon, Ilafegh 009, QUE 94204, and Y-8404. A study of Zakłodzie by Krzesińska et al. (2015) revealed micro-textural features and a mineralogy which suggests that the source rock experienced a severe shock event. This was followed by burial under an ejecta blanketGenerally symmetrical apron of ejecta surrounding a crater; it is thick at the crater's rim and thin to discontinuous at the blanket's outer edge. where recrystallization and annealing occurred.

Zakłodzie has a K–Ar closure age of ~4.50 (+0.02, –0.01) b.y. (Bogard et al., 2010). Other radiometric chronometers reveal that a melting event occurred ~2.1 b.y. ago, possibly reflecting the remelting impact event. The Al–Mg age of Zakłodzie was determined to be 5.4 (±0.4) m.y. 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 (4.5671 b.y.), or an absolute age of ~4.5617 b.y. (Sugiura and Fujiya, 2008). This age is consistent with other basaltic meteorites that experienced early melting and 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 due to radioactive decayProcess in which an isotope's nucleus changes ('decays') to produce another isotope. The original atom is called the 'parent' and the resulting atom, the 'daughter'. There are three modes of radioactive decay: • Emission of a particle (He nucleus) that decreases the atomic number (Z) by 2 and the atomic of short-lived radionuclides such as 26Al.

The cosmogenic nuclides in Zakłodzie, including 4He, 40Ar, 129Xe, and Q-type noble gasesElement occurring in the right-most column of the periodic table; also called "inert" gases. In these gases, the outer electron shell is completely filled, making them very unreactive., indicate a CRE age of 55.3 (±5.5) m.y. This high 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 is also characteristic of the aubritesAubrites are named for the Aubres meteorite that fell in 1836 near Nyons, France. They are an evolved achondrite that is Ca-poor and composed mainly of enstatite (En100) and diopside (En50Wo50) with minor amounts of olivine (Fa0) and traces of plagioclase (An2-8).  They contain large white crystals of enstatite as, which cluster around 50 m.y. Noble gasElement occurring in the right-most column of the periodic table; also called "inert" gases. In these gases, the outer electron shell is completely filled, making them very unreactive. studies indicate that Zakłodzie is distinct from equilibrated E chondrites. During its terrestrial residence, considered to be >100 years, Zakłodzie experienced very high oxidationOxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons,  while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants of Fe throughout much of its mass. The Fe in the outer 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 has progressed to hematiteFe-oxide mineral (Fe2O3) that may be the major cause of the red color on Mars. Coarser-grained gray hematite has the same chemical formula as the red variety, but a different crystalline structure. Deposits of gray hematite found in the Terra Meridiani region of Mars may suggest that water once circulated, with an admixture of the loessAn unconsolidated, clay-rich sediment deposited by the wind. minerals in which the mass was found; nevertheless, 14C results indicate that Zakłodzie is a relatively recent 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.

Despite the very close similarities in O-isotope compositions between Zakłodzie and the ungroupedModifying term used to describe meteorites that are mineralogically and/or chemically unique and defy classification into the group or sub-group they most closely resemble. Some examples include Ungrouped Achondrite (achondrite-ung), Ungrouped Chondrite (chondrite-ung), Ungrouped Iron (iron-ung), and Ungrouped Carbonaceous (C-ung). enstatite achondrite Itqiy, their chemical and mineral compositions, noble gas contents, and terrestrial ages exclude an origin from a common 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.. Likewise, differences between Zakłodzie and enstatite achondrites in some elemental ratios such as Mn/Cr exclude a common origin. The parent body was most likely a member of the enstatite chondrite group of asteroids, and the chemistry is most similar to the EL group (Stepniewski et al., 2000)—the Si concentration in kamaciteMore common than taenite, both taenite and kamacite are Ni-Fe alloys found in iron meteorites. Kamacite, α-(Fe,Ni), contains 4-7.5 wt% Ni, and forms large body-centered cubic crystals that appear like broad bands or beam-like structures on the etched surface of a meteorite; its name is derived from the Greek word of 1.5 wt% is more consistent with the EL group (EH: 1.9–3.8 wt%; EL: 0.3–2.1 wt%).

In 2006, the 685 g achondrite NWA 4301 was found in Algeria. Because this meteorite is almost identical to Zakłodzie in petrologyScience dealing with the origin, history, occurrence, chemical composition, structure and classification of rocks. and mineral composition, and since the two stones have similar young terrestrial ages of ~300 years, scientists have deduced that these two ungrouped enstatite meteorites could be source-crater paired (Irving and Kuehner, UWS). Micro-computed tomography (µCT) scans performed on samples of both of these meteorites indicate differences in their degree of weathering and in their metal abundances, with NWA 4301 exhibiting more weathering and more abundant and interconnected metal veining (Uribe et al., 2015). Continued comparative studies of both meteorites by Uribe et al. (2015) revealed some textural differences in these two meteorites, and they suggest that NWA 4301 might have experienced slower cooling than Zakłodzie. The specimen of Zakłodzie shown above is a 0.74 g partial slice showing a portion of a metal vein. The top photos below show a large mass of Zakłodzie shown courtesy of Marcin Cimala. The middle photo is a thumbnail image to a high-resolution photo shown courtesy of Tomek Jakubowski. The bottom photo is an excellent petrographic thin sectionThin slice or rock, usually 30 µm thick. Thin sections are used to study rocks with a petrographic microscope. micrograph of Zakłodzie shown courtesy of Peter Marmet.


Photos courtesy of Marcin Cimala—PolandMET.com
 

click on image for a magnified view
Photo courtesy of Tomek Jakubowski
 

click on image for a magnified view
Photo courtesy of Peter Marmet