Magmatic ore deposits Flashcards
What are some deposits formed during silicate melt/ fractional crystilization
Cr, Ti - V oxide deposits
What are deposits formed from immiscible sulphide melt phases
Ni, PGE deposits
Deposits formed through extreme fractionation of magma
Li, REE
Whats are REE’s
Rare earth elements
What is Metasomatism
refers to the process whereby a pre-existing rock undergoes compositional and mineralogical transformations associated with chemical reactions triggered by the reaction of fluid or melt
What are examples of layered mafic intrusions
PGE’s, Ti, V (oxide) deposits
What are examples of ultramafic lavas - komatites
Ni-Cu sulphide rich deposits
What type of rock are PGE deposits concentrated in
Igneous rock called Chromatite
what is chomatite formed of
70% chromite mineral (Fe-Cr oxide) and 50-30% silicates (pyroxene and plagioclase)
Where is the target deposit of platinum in the world
Bushveld complex in South Africa
What is one of the problems with PGM deposits
They are quite small
What is an example of a layered mafic intrusion
Skaergaard intrusion, East Greenland
what is modal layering
Layering resulting from variations in the modal abundance of minerals
Characteristic of a closed system layered intrusion
Chamber is filled from single magma influx, example Skaergaard intrusion, Greenland
Characteristic is open system layered intrusions
A chamber is filled from multiple magma influxes, example, Rum intrusion, Scotland, Bushveld complex, South Africa
What are cumulate rocks
Formed during fractional crytsilisation from magma
What are cumulus crystals or primocryststs
Crystal that crystallised the first from the melt
What are intracumulus or interstitial crystals
Crystals that crystallised subsequently
Explain 1st process in formation of layering
1) Dynamic processes - occur during the filling of the magma chamber or during crytilization
Explain 2nd formation of layering
Non-dynamic processes - including rapid changes in intensive conditions of crystallisation (e.g. P, oxygen fugacity) that disrupts and change the stable liquids assemblages
explain 3rd processing of layering
Processes of equilibration of crystal mush - compaction of the crystal mush, grain coarsening an changing liquid composition
