#harzburgite

[rock-swag-tournament]

Rock Swag Tournament Round 1: Igneous Rocks Part 8

Once again we have some rocks named after minerals! This time, they're both ultramafic. Also this time, we also have a fun diagram to look at.

Ternary plots, very useful but sometimes difficult to plot on (at least for me. I always confuse myself, even now). But we're not plotting anything, we're just looking at trends!

If you look at the three corners of this triangle, you will see they are labelled Ol for olivine), Opx for orthopyroxene, and Cpx for clinopyroxene. These corners tell us what three things we are comparing the proportions of. In this case, we are comparing what percent of olivine, orthopyroxene, and clinopyroxene are in a rock (and what we call that rock based on the relative amounts of these minerals).

Ternary diagrams can have any three things in the corners, but you'll often see QFL (Quartz, Feldspar, Lithics) diagrams to classify sedimentary rocks, or sand-silt-clay diagrams for soil texture. You can also stick two triangles together to make a diamond for something like a QAPF diagram where the four points are quartz, alkali feldspar, plagioclase, and feldspathoids. QAPF diagrams are also used to classify igneous rocks (you can plot syenite and monzonite on them, as well as your granites).

The closer you get to the top corner of the triangle, the more olivine you have. The closer you get to the right corner of the triangle, the more clinopyroxene you have, and the closer you get to the left corner of the triangle, the more orthopyroxene you have.

If your rock sample plots in the top half (ish) of the triangle (at least 40% olivine), your rock is a peridotite. Now, depending on the relative amounts of pyroxene minerals, you may have different types of peridotite like lherzolite, wherlite, harzburgite, or dunite.

In the picture of peridotite above, the peridotite is actually the xenolith (the green rock embedded in the black rock) and it would be considered dunite because it is more than 90% olivine. The reason a rock full of olivine is called peridotite is because peridot is another name for olivine (specifically gemstone-quality olivine).

As for pyroxenites, if you have less than 40% olivine, the rock would be a pyroxenite. If it's almost all pyroxene (no more than ~5% olivine, at the bottom of the pyramid), it would be called websterite.

As for other facts about the rocks, both peridotite and pyroxenite are typically intrusive, phaneritic rocks derived from the mantle. Peridotite is going to be some shade of green because of the olivine, and pyroxenite is usually black or at least dark in color.

I'm also thinking of making an informational post about volcanoes, partial melting (and magma composition) and how these rocks/magmas get from the mantle to the surface, so look out for that at some point (I know myself better than to name a specific timeline).

[butchharrydalton]

I will now recite the rocks in alphabetical order:

adamellite

amphibolite

andesite

anorthosite

anthracite

appinite

aphanite

arenite

argillite

arkose

basalt

basanite

blueschist 

biomicrite

biosparite

boundstone

breccia

carbonatite

cataclasite

chalk

chert

claystone

clinopyroxenite

coal

conglomerate 

coquina

dacite

diamictite

diatomite

diorite

dolomite 

dunite

eclogite

essexite

evaporite

flint

foidite

gabbro

gabbronorite

gneiss

gossan

granite

granodiorite 

granophyre

granulite

graywacke

gritstone

greensand

greenschist

harzburgite

hornblendite

hornfel

hyaloclastite

icelandite

ignimbrite

ijolite

itacolumite

jadeitite

jasperoid

jaspillite

kenyte

kimberlite

komatiite

lamproite

lamprophyre

larvikite

laterite

latite

lherzolite

lignite

limestone

litchfieldite

litharenite

llanite

luxullianite

mangerite

marble

marl

metapelite

metapsammite

migmatite

minette

monzodiorite

monzogranite

monzonite

mudstone

mylonite

nepheline syenite

nephelinite

norite

novaculite

obsidian

oil shale

oolite

pantellerite

pegmatite

peridotite

phonolite

picrite

porphyry

phyllite

pseudotachylite

pumice

pyrolite

pyroxenite

quartzarenite

quartzite

rhyolite

sandstone

schist

scoria

shale

siltstone

serpentinite

shonkinite

skarn

slate

suevite

soapstone

syenite

syenogranite

taconite

tephrite

teschenite

theralite

tholeiite

tonalite

trachyte

travertine

tuff

turbidite

urtite

variolite

wackestone

websterite

wehrlite

whiteschist

xenolith

[drrockclub]

Rock from inside of the Earth

Top and bottom image is of the same feature but using different light filters in the microscope.

Inside of our planet known as mantle is made of rather fewer rock types than what we get on the surface, and likewise for the minerals that constitute them. Here, is a microscope image of one of those rocks called harzburgite which is made of just olivine also known as peridot in gem community (green-blue-pink) and orthopyroxene (orange).

Under the microscope this very thin slice of rock refracts the light what gives these minerals spectacular colours when the light is polarized to help with mineral identification (top image). Whereas, when the light is not polarized, the minerals are left looking plain, which is helpful in identifying the texture of the rock (bottom image).

Image taken with the petrographic microscope.

[earthstory]

Step 1 in geochemical analysis once you’re back in the lab - rock crusher. Rock described as a “waruite-bearing serpentinized harzburgite “

[xxlying-from-y0u]

There’s nothing wrong with admitting you were once toxic. there’s nothing wrong with admitting you made a couple people feel like shit. there’s nothing wrong with admitting you fucked up and were horribly arrogant and parasitic. there’s nothing wrong with admitting you did anyone wrong, especially if you’ve learned from it. If you’re humble enough to admit it, I guarantee there’s a bit of a good person inside of you.

harzburgite, via Tumblr

[studying-geology-blog]

Fibrous asbestos veins in serpentinised mantle harzburgite from the Troodos Mountain Ophiolite Sequence, Cyprus.  (main vein is ~70 m thick) Credits : @drrhcmadden . #geology #amazing #cool #fibrous #mantle #harzburgite https://www.instagram.com/p/BsQ0e3XBglA/?utm_source=ig_tumblr_share&igshid=wub943fpq6o5

[politicsandwhatnots]

Diamonds Show Earth Still Capable of ‘Superhot’ Surprises

Diamonds may be ‘forever’ but some may have formed more recently than geologists thought.

A study of 26 diamonds, formed under extreme melting conditions in the Earth’s mantle, found two populations, one of which has geologically ‘young’ ages. The results show that certain volcanic events on Earth may still be able to create super-heated conditions previously thought to have only existed early in the planet’s history before it cooled. The findings may have implications for diamond prospecting.

Diamonds can be categorized by their inclusions: minerals trapped within the carbon crystal structure that give clues about the conditions and the rocks in which they formed. The studied diamonds contain harzburgitic inclusions, a type of peridotite ‒ the most common rock in Earth’s mantle ‒ which have experienced extreme temperatures and undergone very large amounts of melting.

More: [X]

[morganites-realgar]

It’s a Geological Life: Spain Edition

Day 4: to Etang de Lers and FREAKING MANTLE ROCKS!!

July 21, 2016

Oh, the mantle was beautiful!

The Mantle in Etang de Lers

In the central Pyrenees, France, is the Lherz Massif, which displays one of the best exposures of the subcontinental lithospheric mantle. These Pyrenean orogenic peridotites are comprised of 40 distinct ultramafic bodies of  intermingling harzburgites and spinel lherzolites. The massifs are associated with crustal granulites and are embedded within carbonate rocks of Jurassic age. The carbonate rocks are affected by the low-pressure/high-temperature metamorphism. The exhumed mantle rocks are located within the North Pyrenean Matamorphic Zone. 

During the Lower Cretaceous, the Iberian plate (Spain) was experiencing regional rifting, which was localized along the North Pyrenean Fault Zone. The fault zone created extensional basins by transcurrent movement (strike-slip) activity. 

(Not my photos and I do not know where my professor got it. If anyone know, please tell me. I would like to give credit.)

In these basins, there was crustal thinning and resulted in the Low P-High T metamorphism. Ganolithic and ultramafic mantle rocks were emplaced in the upper crust. After the strike-slip activity, convergence between the Afro-Iberian and European plates formed an inversion of Late Jurassic and Earth Cretaceous extensional basins. The collision formed a doubly verging collisional mountain belt and pushed the mantle rocks to the surface. 

(From: “Active Tectonics of the Pyrenees: A review”)

The lovely J.D. is hammering away at the carbonate host rock.

The mighty Clark is delicately holding a beautiful sample of lherzolite

[pamirtimesblog]

Mineral Potential in Diamer District

Mineral Potential in Diamer District

Muhammad Yaqub Shah It is already established by the earlier researchers that the Chilas complex, Pakistan is a huge mafic-ultramafic intrusive complex, with ultramafic suit of rocks composed of  dunites, harzburgites, troctolites, hornblende gabbros, pyroxenites, and anorthosites. Whereas the ultramafic rocks including chrome spinel + olivine dunites, show spectacular gravity-settling layered…