science

Lherzolite

Lherzolite is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lherzolite rather than just read about it. In short: Lherzolite is a type of peridotite. It is a coarse-grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser amounts of calcic chromium-rich clinopyroxene.

Key takeaways

Lherzolite belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lherzolite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lherzolite from memory before moving on to harder problems.

Reference excerpt

Lherzolite is a type of peridotite. It is a coarse-grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser amounts of calcic chromium-rich clinopyroxene. Minor minerals include chromium and aluminium spinels and garnets. Plagioclase can occur in lherzolites and other peridotites that crystallize at relatively shallow depths (20 – 30 km). At greater depth plagioclase is unstable and is replaced by spinel. At approximately 90 km depth, pyrope garnet becomes the stable aluminous phase. Garnet lherzolite is a major constituent of the Earth's upper mantle (extending to ~300 km depth). Lherzolite is known from the lower ultramafic part of ophiolite complexes (although harzburgite is more common in this setting), from alpine-type peridotite massifs, from fracture zones adjacent to mid-oceanic ridges, and as xenoliths in kimberlite pipes and alkali basalts. Partial melting of spinel lherzolite is one of the primary sources of basaltic magma. Lherzolite can also form as cumulates within layered intrusions. 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 meteorites 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.

Asteroid 4 Vesta and HED parent body Geochemical analyses have identified a suite of unbrecciated ultramafic meteorites such as NWA 12217, NWA 12319, and NWA 12562 as lherzolite and dunite cumulates from the deep crust or upper mantle of the asteroid 4 Vesta (or a highly similar differentiated protoplanet). Historically, the Howardite-Eucrite-Diogenite (HED) suite provided samples of Vesta's upper volcanic basaltic crust (eucrites) and lower crustal orthopyroxenites (diogenites), leaving a "missing mantle problem" regarding the asteroid's predicted olivine-rich interior. These Vestan lherzolite cumulates consist primarily of magnesium-rich olivine alongside orthopyroxene and minor clinopyroxene, representing crystal settling from an early Vestan magma ocean. High-precision oxygen (Δ¹⁷O) and chromium (ε⁵⁴Cr) isotopic fingerprints match the HED suite, while highly depleted siderophile element concentrations confirm these lherzolites formed after core segregation was complete on the parent body.

References

Blatt, Harvey and Robert J. Tracy, 1996, Petrology: Igneous, Sedimentary and Metamorphic, 2nd ed., Freeman, ISBN 0-7167-2438-3

Illustrations

Worked examples

Example 1 — a first encounter with Lherzolite

Start with the simplest possible case. Write down what Lherzolite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lherzolite before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lherzolite ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lherzolite

In research: Lherzolite appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lherzolite in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lherzolite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Achondrite meteorites, Meteorites, Ultramafic rocks, so understanding it makes those chapters shorter.
In everyday life: Look for Lherzolite outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Lherzolite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lherzolite means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lherzolite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lherzolite in simple terms?

Lherzolite is a type of peridotite. It is a coarse-grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser amounts of calcic chromium-rich clinopyroxene.

Why does Lherzolite matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lherzolite?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lherzolite.