Lherzolite

The name is derived from its type locality, the Lherz Massif (an alpine peridotite complex, also known as orogenic lherzolite complex), at Étang de Lers, near Massat in the French Pyrenees; Étang de Lherz is the archaic spelling of this location.

The Lherz massif also contains harzburgite and dunite, as well as layers of spinel pyroxenite, garnet pyroxenite, and hornblendite. The layers represent partial melts extracted from the host peridotite during decompression in the mantle long before emplacement into the crust.

The Lherz massif is unique because it has been emplaced into Paleozoic carbonates (limestones and dolomites), which form mixed breccias of limestone-lherzolite around the margins of the massif.

The Moon's lower mantle may be composed of lherzolite.

Lherzolitic shergottites

Lherzolitic shergottites are a rare subclass of Martian meteorites within the shergottite group. Named for their mineralogical similarity to terrestrial lherzolite rocks, these specimens are coarse-grained, primitive magmatic rocks that originated deep within the subsurface of Mars. They represent some of the most mafic components of Martian magmatism discovered on Earth.

Mineralogy and texture

Lherzolitic shergottites are characterized by a distinct poikilitic-to-non-poikilitic texture. The primary rock-forming minerals include:

• Olivine: Typically making up 50% to 55% of the total volume.
• Pyroxene: Comprising roughly 35% of the volume, consisting of both low-Ca (pigeonite) and high-Ca (augite) varieties.
• Maskelynite: A shock-melted plagioclase feldspar glass (roughly 5% to 8%) resulting from the impact event that ejected the rock from Mars.

Accessory minerals commonly include chromite, ilmenite, and calcium phosphates such as merrillite.

Impact metamorphism

Due to the high-energy impact required to achieve escape velocity from the Martian gravitational field, all known lherzolitic shergottites exhibit signs of severe shock metamorphism. This includes extensive fracture networks, the formation of localized melt pockets, and the complete transformation of crystalline plagioclase into maskelynite. High-pressure mineral phases such as stishovite and tuite (γ-Ca₃(PO₄)₂) are often found inside these shock-melt zones.

Notable specimens

• ALHA77005: Found in the Allan Hills of Antarctica in 1977, this was the first meteorite classified under this group.
• LEW 88516: A 13.2-gram specimen found in the Lewis Cliffs region that shares almost identical ejection timelines with ALHA77005.
• NWA 1950: Discovered in the Moroccan Atlas Mountains in 2001, providing researchers with larger, non-Antarctic mass profiles to study.