R3.9, rumurutiiteMember of a rare group of chondrites, formerly named the Carlisle Lakes group, after a meteorite found in Australia in 1977. It is now named for the type specimen Rumuruti that fell in Kenya, Africa, in 1934. Rumuruti is the only witnessed fall of this group and only one small
Found January 2000 coordinates not recorded Multiple fragments weighing together 12 kg were purchased in Rissani, Morocco, while the actual 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. Click on Term to Read More location was probably the Kem Kem region of the Sahara. Classification was performed at the Institut für Planetologie in Münster, Germany. Northwest Africa 753 is a brecciated, very weakly shocked (S2) 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 Click on Term to Read More that is relatively fresh compared to most other R 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 Click on Term to Read More finds—designated W2 on the Wlotzka weathering scale (1993). Abundant sulfides, typically pyrrhotites, attest to a S-rich environment of formation (Jackson and Lauretta, 2010). It has been established through laboratory analyses that several pairings to NWA 753 exist, including NWA 1472, 1476, 1477, 1478, and 1566.
Results of Mn–Cr isotopic systematics have established an initial age for NWA 753 of 4.561 (±2) m.y., which is a few m.y. younger than the age established for carbonaceous 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 Click on Term to Read More (~4.566 m.y.) (Jogo et al., 2006). A possible correlation of Cr-isotopic compositions with O-isotopic variations for ordinary and R chondrites has been demonstrated.
In their search for 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 Click on Term to Read More and other Al-rich objects in R chondrites, Rout and Bischoff (2008) and Rout et al. (2009) discovered a high abundance of such objects in unequilibrated clasts from NWA 753. They determined that the abundance of CAIs in R chondrites is less than it is in carbonaceous chondrites, but greater than in ordinary and 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). Click on Term to Read More chondrites. These CAIs in R chondrites are significantly smaller than those in CM and CV chondritesMeteorite class named after the Vigarano meteorite that fell in Italy in 1910. They have abundant large, well-defined rimless (?) chondrules of magnesium-rich olivine (~0.7 mm diameter; 40-65 vol. %), often surrounded by iron sulfide. They also contain 7-20 vol. % CAIs. The often dark-gray matrix is dominated by Fe-rich Click on Term to Read More, but similar in size to those in CH, O, and E chondrites. Based on Δ17O values, the CAIs in R chondrites were divided into 16O-rich (~ –23‰ to –26‰), 16O-depleted (~ –2‰), and heterogeneous (–25‰ to +5‰). As with CAIs of other chondrite groups, R chondrite CAIs were likely formed in an 16O-rich nebular region, with some sustaining subsequent isotopic exchange with an 16O-depleted nebular gas or through metasomatism on the parent asteroid. Taking into account the differences in mineralogy between the majority of R chondrite CAIs and those from other groups, R chondrites contain a unique subset of CAIs. That said, the investigators argue that certain types of CAIs present in R chondrites strongly resemble some of those found in the CO-chondrite group, especially those present in the more highly metamorphosed meteorites like Ornans, Moss, Isna, and Lancé. Other Al-rich objects in R chondrites share similarities to those from the O- and E-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 Click on Term to Read More groups.
Kita et al. (2013) employed the same technique for NWA 753 that is applied to ordinary chondriteWork in Progress Ordinary chondrites (OCs) are the largest meteorite clan, comprising approximately 87% of the global collection and 78% of all falls (Meteoritical Society database 2018)1. Meteorites & the Early Solar System: page 581 section 6.1 OC of type 5 or 6 with an apparent shock stage of S1, Click on Term to Read MorechondrulesRoughly 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 Click on Term to Read More for determination of the petrologic subtype from 3.00 to 3.2, which is based on the alteration resistant Cr content in ferroan 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 Click on Term to Read More (Grossman, 2004; Grossman and Brearley, 2005). They determined that the corresponding petrologic subtype for the least equilibrated material in NWA 753 is 3.15–3.20, the lowest subtype found among R chondrites. Crowther et al. (2015) utilized I–Xe chronometry in a preliminary study of four samples of NWA 753 having a petrologic typeMeasure of the degree of aqueous alteration (Types 1 and 2) and thermal metamorphism (Types 3-6) experienced by a chondritic meteorite. Type 3 chondrites are further subdivided into 3.0 through 3.9 subtypes. range of 3.15–3.9. They found that a correlation exists between the closure age and the petrologic type of a sample, with a younger age being correlated with a higher degree of metamorphism. This range of petrologic types reflects a difference in age of ~5 m.y. years and is consistent with cooling within an onion-shell structure on the R-chondrite 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. Click on Term to Read More.
Consistent with the absence of solar gases, NWA 753 is not thought to have been part of a regolithMixture of unconsolidated rocky fragments, soil, dust and other fine granular particles blanketing the surface of a body lacking an atmosphere. Regolith is the product of "gardening" by repeated meteorite impacts, and thermal processes (such as repeated heating and cooling cycles). Click on Term to Read More for any significant length of time. Evidence gathered thus far indicates that NWA 753 experienced a relatively rapid transfer from the asteroid 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 Click on Term to Read More to the Earth, having a 21Ne-based CRE age of 12.8 m.y. (Schultz et al., 2005). Subsequent 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. Click on Term to Read More analyses of the known Northwest Africa R chondrites were conducted by Vogel et al. (2014). Their ~16 groupings vary slightly from the previous pairings suggested by other investigators, and they propose an ~14 m.y. CRE age group representing possible common source craters and/or 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 Click on Term to Read More events which includes R chondrites with the NWA series designations 753, 1472, 1476, 1477, 1478, 1566, 4360, 4419, and 5606.
This unique chondrite group was originally named for the Carlisle Lakes, Australia (49.5 g) specimen, but has since been renamed for the only fall of the group from Rumuruti, Kenya (67 g) in 1934. Two views of a 0.54 g partial slice of NWA 753 are shown above: the right photo shows the melted fusion-crusted surface, while the left photo shows the abundant tiny chondrules characteristic of this chondrite group.