Lunar Mingled 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 (basalt-bearing fragmental 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). breccia predominantly feldspathic)
Found January 18, 2005 18° 54′ 52′ N., 54° 20′ 42′ E. A single elongated fusion-crusted stone, weighing 115.2 g, was found by Michael Farmer while searching for meteorites in Oman. A section of the 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 was submitted to Northern Arizona University (T. Bunch and J. Wittke) and Washington University in Seattle (R. Korotev) for analysis and classification, and Dhofar 1180 was determined to be a lunar meteorite unpaired to any other lunar 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..
Preliminary studies have determined that Dhofar 1180 is a polymict brecciaGeneral term for all breccias that are neither monomict nor dimict. Modified from image source: http://www.saharamet.com/meteorite/gallery/HED/index.html. comprised primarily of clasts consisting of feldspathic anorthositic material consistent with a highlands origin. Fe-enriched, chemically zoned, 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 (havingmineralInorganic 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 inclusions, which constitute ~33% of the breccia, are thought to represent late-stage fractionationConcentration or separation of one mineral, element, or isotope from an initially homogeneous system. Fractionation can occur as a mass-dependent or mass-independent process. products of a mareBroad low plains surrounded by basin-forming mountains, originally thought to be a sea (pl. maria). This term is applied to the basalt-filled impact basins common on the face of the Moon visible from Earth. basaltBasalt is the most common extrusive igneous rock on the terrestrial planets. For example, more than 90% of all volcanic rock on Earth is basalt. The term basalt is applied to most low viscosity dark silicate lavas, regardless of composition. Basalt is a mafic, extrusive and fine grained igneous rock. The Ti content of these minerals are consistent with very-low-Ti mare basalts. All of these components show evidence of a slight preferred orientation. In addition, clasts of granulite and crystalline impact-melt breccias are present, as well as grains of 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, 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., and 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 (Zhang and Hsu, 2006). This breccia is a rare mixture of mare material and feldspathic highlands material that is similar to that found in Calcalong Creek and Y-983885, although Dhofar 1180 is less magnesian and contains a much lower abundance of incompatible elements (no 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. was identified). The clasts identified in Dhofar 1180 consist primarily of ferroan anorthosites, together with more mafic gabbroic anorthosites, anorthositic gabbros, norites, troctolites, olivine gabbros, and impact-melt breccias (Bunch et al., 2006; Korotev et al., 2009).
Diverse glasses of both mafic and feldspathic composition are present, with and without mineral inclusions, which are consistent with multiple impact events. Other glasses resemble regolith agglutinates. Based on these observations it was inferred by Zhang and Hsu (2009) that NWA 1180 had a regolith origin. They found that some glasses are consistent with a highly fractionated mare basalt component. One P-rich glass clastA mineral or rock fragment embedded in another rock. initially described as KREEP has been more accurately described as a granite–quartz-monzogabbro immiscibleThe property of liquids that are mutually insoluble (won't mix together) such as oil and water or metallic and silicate melts. liquid by Korotev et al., (2009). With its Fe-rich mafic clasts and comparatively low Th abundance of 0.7–0.9 ppmParts per million (106)., the host rock likely originated on the lunar nearside from a location distant from the PKT region, and from a location distinct from any previously studied lunar rock.
In a diagram comparing Sc vs. Sm for the lithologies of the FHT, PKT, SPA, and mariaBroad low plains surrounded by basin-forming mountains, originally thought to be a sea (pl. maria). This term is applied to the basalt-filled impact basins common on the face of the Moon visible from Earth. , NWA 1180 plots as a mixture of feldspathic highlands material containing ~33% mare basalt (Korotev et al., 2009). However, a petrographic analysis of NWA 1180 determined that a mare basalt component was very rare, and therefore, they proposed that the low Sm and intermediate Fe and Sc contents of NWA 1180 are actually the consequence of a mafic, KREEP-poor component derived from 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 rocks of the FHT. In light of that finding, the use of the term ‘mingled’, typically used to describe the ternary mixture of FHT, PKT, and maria commonly found in the Apollo samples, might not be strictly accurate for this meteorite.
During a subsequent trip to the find area in February of 2005, Eric Olson found a small 3.1 g paired stone lying within 100 feet of the site of the original stone, and the following day Michael Farmer found two additional small paired stones weighing 2.04 and 0.78 grams. The specimen of Dhofar 1180 pictured above is a 0.304 g full slice, while the photo below shows an in situ photo of the complete 115 g main massLargest fragment of a meteorite, typically at the time of recovery. Meteorites are commonly cut, sliced or sometimes broken thus reducing the size of the main mass and the resulting largest specimen is called the "largest known mass"..
Photo courtesy of M. Farmer