major elements Flashcards
what is a major elements
referred as rock forming minerals e.g. quartz
> 1wt% of rocks composition
commonly reported as oxide
major elements examples
SiO2
MgO
FeO
Fe2O3
CaO
Al2O3
Na2O
why analyses major elements
understand processes and condition of melting and crystallization
how to present major element analyze
harker diagrams
what use harker diagram
allow trends between different elements to be observed
allow trends to be interpreted in terms of magma differentiation processes
what does an inflection point show
new mineral being crystallised
if trend then goes down this means that mineral is being removed from melt
afm diagram
alkaline(k20+na2o)/fe/mg
used to further subdivide and characterize subalkaline igneous rocks or magma series
cipw norm
calculates ‘idealised’ mineralogy from a major element analysis of an igneous rock
mode
(modal mineralogy)
vol% of minerals seen in a rock or thin section
type of rocks that have quartz in their norm
silica-oversaturated
type of rocks that have feldspathoids in their norm
silica-undersaturated
feldspathoids examples:
naphthalene
sodalite
lucite
