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 Click on Term to Read More
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:, noncumulate
(Main Group–Nuevo Laredo trend)
Found February 2000
29° 14′ N., 8° 22′ W.
A 1,470 g 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
was recovered in several pieces in Morocco. Igdi is composed of 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 Click on Term to Read More
, pigeoniteLow-Ca clinopyroxene, (Ca,Mg,Fe)SiO3, found as a major mineral in eucrites and shergottites. In order to be considered pigeonite, the clinopyroxene must contain 5 to 20 mol % of calcium (Wo5 - 20). Chondrites of petrologic types 4 and below contain significant low-Ca clinopyroxene. During metamorphism to higher temperatures, all existing
with exsolved clinopyroxene, silicaSilicon dioxide, SiO2.
, ilmeniteTi-Fe oxide, TiFeO3, found in achondrites, lunar mare basalts, and shergottites. Ilmenite forms as a primary mineral in mafic igneous rocks. It crystallizes relatively early out of a magma before most of the other minerals, and as a result, the heavier crystals of ilmenite precipitate to the bottom of the magma Click on Term to Read More
, chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More
, and troiliteBrass colored non-magnetic Fe sulfide, FeS, found in a variety of meteorites.
. The Nuevo Laredo 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 Click on Term to Read More
are thought to be the product of in situ crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. Click on Term to Read More
of residual melts in a differentiating magma oceanCompletely molten surfaces of terrestrial planets or moons that formed soon after accretion. Samples returned by the Apollo missions provide evidence of a lunar magma ocean, crystallization of which produced a stratified Moon with a low-density crust formed by accumulation of the mineral plagioclase overlying a higher density mantle of Click on Term to Read More
. This origin is consistent with the decoupling between major elements and incompatible trace elements; i.e.
, for an increase in incompatible 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 Click on Term to Read More
abundances there is a decrease in Mg/(Mg + Fe). On a plot of Mg# versus an incompatible element such as Ti, Igdi falls comfortably within the Nuevo Laredo trend meteorites. The Nuevo Laredo trend has been combined with the Main Group eucrites in the currently recognized classification scheme (Barrat et al.
In a study of several Antarctic non-cumulate basaltic eucrites by Bermingham et al.
(2008), a possible new subgroup was identified. In contrast to the other eucrites studied, members of this new subgroup exhibit LREE-depleted patterns with positive Eu anomalies, and other incompatible trace element abundances are lower than those in the other non-cumulate basaltic eucrites studied. Moreover, in contrast to the plagiophile elements in the other eucrites studied, the new subgroup contains higher Sr/Nd ratios when plotted against the magnitude of the Eu anomaly. It was proposed that this new subgroup might represent a parental source which was enriched in a plagioclase melt. It should be considered that high Sr, Ba, and Pb concentrations could be the result of severe weathering. The specimen of Igdi shown above is a 2.2 g complete slice.