EARTH 232 Flashcards
(30 cards)
What is the difference between a eutectic and peritectic?
A eutectic is the lowest temperature at which all phases are in equilibrium, whereas a peritectic is a point on a phase diagram where a new solid phase forms due to a reaction between the mineral phase and the melt,
What is the difference between prograde and retrograde metamorphism
Prograde is an increase in metamorphic grade with time, whereas retrograde is a decreasing metamorphic grade with time
What is the difference between micrite and sparite
Micrite is a microcrystalline ooze, sparite is sparry calcite cement
What are terrigenous sediments?
Sediments that were eroded outside of the depositional area and transported as solid clasts
What are allochemical sediments?
Sediments that were chemically precipitated outside of the depositional area, but were transported as solid clasts
What are orthochemical sediments?
Sediments that were chemically precipitated directly in the depositional area
What does ‘periluminous’ mean?
Molecular proportion of Al2O3 > CaO+Na2O+K2O
What does ‘peralkaline’ mean?
Molecular proportion of Al2O3 < Na2O + K2O
What does ‘metaluminous’ mean?
Molecular proportion of Al2O3 > Na2O + K2O (but not Na2O, K2O and CaO combined)
What is the difference between sanidine and microcline?
Sanidine is monoclinic, microcline is triclinic
What is the difference between perthitic and antiperthitic texture?
Perthite is the growth of albite lamellae in a K-spar host, antiperthite is the growth of K-spar lamellae in an albite host
Which is the more effective process: ridge push or slab pull?
Slab pull
What are the main differences between basalt and andesite
Basalt has <52% SiO2, more mafic, andesite has >52% SiO2, is more felsic
Why are komatiites extinct?
Mantle is now too cool for them to form, was 100-250 degrees hotter during the Archaen
What are the main differences between mafic and felsic melts?
Mafic melts are less viscous than felsic melts, and have a lower silica saturation, felsic melts have more volatiles
How is a melt made?
Moving geotherm to the right (increase temperature), lowering pressure to modify geothermal gradient, adding fluids/volatiles
What is the difference between compaction and cementation?
Compaction is the sequeezing of sediments under the weight of sediments above them, cementation is when cement from fluids bind sediments together
What is ‘diagenesis’?
Physical and chemical processes that occur as sediment is converted to sedimentary rock
What are the main differences between the terms ‘arkose’ and ‘arenite’?
Arkose refers to feldspar-rich sediments, arenite refers to sandstone-like sedimentary rocks
What are the 8 igneous rock diversity mechanisms?
Fractional crystallization, filter differentiation, flow segregation, crystal zoning, liquid immiscibility, fluids, assimilation, magma-mixing
What is the different between leucocratic and melanocratic igneous rocks
Leucocratic rocks have <30% mafic minerals (light-coloured), melanocratic rocks have >60% mafic minerals (dark-coloured)
What is the starting temperature on the enstatite-ferrosilite phase diagram?
1115 degrees C
What is the ending temperature on the enstatite-ferroilite phase diagram?
975 degrees C
What is the crystal structure under the inversion curve of the enstatite-ferrosilite phase diagram?
Orthorhombic (OPX)
