avelines-butt:

i don’t know what’s funnier the pun or the fact that there’s no crayola products

(via luke-hole)

herochan:

Batman: Arkham Origins Trailer

 In stores October 25th, 2013

okay so this should be some sort of film or something

(via luke-hole)

thoseanythings:

Sorry, I’m going to leave this porn right here.

(via brontozaurus)

commanderspock:

seafarers

Lava Flow at Dawn by Tom Kualii

(via hammerforscale)

titsmcgrits:

rebeccalouder:

Laughing so hard it hurts.

Crying

(via evaporites)

The thought of finishing my undergraduate degree with my last exam tomorrow is sending me a bit crazy.

This effect is added with my youtube playlist which has some crackers in it, this song being one of the beasts that lie within.

Skarns

These are metasomatic deposits characterised by calc-silicate minerals e.g. garnet, amphibole, diopside, and wollastonite.

They are often irregular masses, and occur close to or at intrusion margins. They commonly replace existing lithologies e.g. limestones, carbonate-cemented shales.

Exo- vs endo-skarns: Endoskarns replace intrusion rocks, and exoskarns replace country rocks.

They can be a source of a variety of ores which are targeted for the following elements: Fe, Cu, W, Zn, Pb, Mo, Sn, U. They are also mined for industrial minerals (aka the boring ones).

(sorry for using symbols for elements, but build a bridge).

Formation:

Initial isochemical metamorphism of the country-rock by intrusions, followed by multiple stages of metasomatism caused by magmatic and/or hydrothermal fluids, whose temperatures range from 400-800 centigrade. Minerals are precipitated due to decreasing temperatures of transporting fluid and reaction with country-rocks.

On top of this you can have retrograde alteration and destruction of early skarn minerals by infiltrating meteoric fluids.

Greisens - epigentic deposit (formed after host rock formed)

These are granoblastic aggregates formed by post-magmatic metasomatic alteration of granite. They can appear irregular or sheet like, as they do in this picture.

They are predominantly quartz and muscovite rich (or lepidolite, which is a Li-mica) plus/minus topaz, tourmaline, and fluorite.

They can be a source of Tin and Tungsten (Sn and W respectively). 

The residual fluorine-rich magmatic fluids are capable of scavenging Sn and W from the magma and wallrock, and (hopefully) depositing them in nice concentrated deposits. 

This photo is from the South-West of England, an area where there are lots of granites and an area where tin mining was prevalent (which is a nice way for me to remember what target elements are in greisens). 

Pegmatites

(the whiteish dykes in the picture)

These are coase grained igneous mineral assemblages, and often contain uncommon minerals (hence their economic potential).

They may have crystallised from a magma in the prescence of a magmatic aqueous fluid, and commonly contain quartz, feldspars, and micas, which can be mined for industrial uses.

The classical model for formation is that they precipitate late-stage magmatic minerals due to extreme fractional crystallization.

They have a large variety of target elements, depending on the type/locality. Some include Sn, W, U, Th, Li, Be, plus a whole lot more.

Depending on the type of granite, there are two groups of elements that are of use.

If it’s formed from an I-type granite, that is to say a granite where the parental magmas were produced by partial melting of predominantly igneous source rock, then the target elements are Nb-Y-F.

If it’s formed from a S-type granite, that is to say a granite where the parental magmas were formed by partial melting of predominantly sedimentary source rock (think crustal contamination) then the target elements are Li-Cs-Ta-(B).

Jahns and Burnham model for pegmatite development: they attribute the transition from granite to pegmatite due to H20 saturation in the magma. They say that pegmatites form in the presence of a separate aqueous/volatile fraction of the magma, which explains the large crystal size. This is because volatiles lower the solidus temperature of the granite AND allows more efficient diffusion (migration of the major-elements into the H20-saturated fraction).

Brief side-note on I- and S-type granites.

I-type: as stated above, come from a magma produced by partial melting of predominantly igneous source rock. They are more oxidised, and produce Cu-Mo-Au mineralisation and form porphyry/epithermal deposits.

S-type: formed by partial melting of predominantly sedimentary material, and are less oxidised due to the presence of graphite. These produce Sn-W (-U) and are granophile deposits, that is to say a granitoid-related mineral deposit

Carbonatities

Na carbonate-silicate magmas (when I first heard about these I was like “whoa, carbonate magmas? This goes against a lot of shit”)

These types of magmas are exploiited for a variety of metal-bearing minerals and industrial minerals e.g. REE oxides, copper, vemiculite, magnetitie.

These magmas are capable of crystallizing >50% carbonate minerals.

Carbonatite complexes are intrusive assemblages of carbonate rocks (calcite dominated) and silicic rocks, and can occur as ring intrusions (typically <1km^2). The complexes can be significantly altered (and often are) by metasomatism (alteration by hydrothermal fluids).

They typically occur in rift settings e.g. E. African Rift, Oslo Graben, Rhine Graben, St. Lawrence rift.

The sodium often ends up in alkali-rich waters as the Na carbonates are very unstable, and the sodium goes into solution.