Geology Of the Mantle Flashcards
Ultramafic Xenoliths
chunks of solid mantle carried upward as inclusions in lava
Chemical reactions and quantum mechanics
Ultramafic Xenoliths
Ophiolite
a chunk of seafloor that has been pushed up on land, we can detrmine the composition of the mantle by averaging it’s layers
a chunk of seafloor that has been pushed up on land, we can detrmine the composition of the mantle by averaging it’s layers
Ophiolite
layers of an ophiolite (bottom to top)
Hartzburgite, dunite, gabbro, sheet dikes, pillow bassalts
Hartzburgite, dunite, gabbro, sheet dikes, pillow bassalts
layers of an ophiolite (bottom to top)
Lherzolite
the forbidden rock we know exists, but can’t see, that makes up the upper mantle. Composed of Olovine, Orthopyroxine, and clinopyroxine
the forbidden rock we know exists, but can’t see, that makes up the upper mantle. Composed of Olovine, Orthopyroxine, and clinopyroxine
Lherzolite
Aluminum in the mantle
can’t be incorporated int Lherzolite, so insted it forms either plagioclase, spinel, or garnet depending on the conditions
can’t be incorporated int Lherzolite, so insted it forms either plagioclase, spinel, or garnet depending on the conditions
Aluminum in the mantle
Olivine collor in hand
olive green to greenish grey
olive green to greenish grey
Olivine collor in hand
olivine cleavage
poor cleavage, in both hand sample and thin section, thin section shows fracturing
poor cleavage, in both hand sample and thin section, thin section shows fracturing
olivine cleavage
Olivine habbit
either massive or drusty
either massive or drusty
Olivine habbit
olivine XPL
second order collors like a stained glass window
second order collors like a stained glass window
olivine XPL
clinopyroxene in thin section
bright 2nd order olors in XPL, has obvious cleavage
bright 2nd order olors in XPL, has obvious cleavage
clinopyroxene in thin section
Orthopyroxene in thin section
1st order colors n XPL with obvious cleavage
1st order colors n XPL with obvious cleavage
Orthopyroxene in thin section
pyroxenes in hand sample
nerely impossible to tell orthopyroxine and clinopyroxine appart, forms augite, tends to have hard to see 90 degree cleavage and never has twinning
nerely impossible to tell orthopyroxine and clinopyroxine appart, forms augite, tends to have hard to see 90 degree cleavage and never has twinning
pyroxenes in hand sample
Plagioclase in thin section
first order collros with high probability of twinning
first order collros with high probability of twinning
Plagioclase in thin section
plagioclase in hand sample
grey to black, twinning is visible in larger crystals, such as in abrodorite, as streaks when held up to light.
grey to black, twinning is visible in larger crystals, such as in abrodorite, as streaks when held up to light.
plagioclase in hand sample
Garnet in thin section
constantly extinct in XPL, clear in PPL with high relief
constantly extinct in XPL, clear in PPL with high relief
Garnet in thin section
Garnet in hand
has hackley fracture and a distinctive crystal shape, usualy red, but not reliably so
has hackley fracture and a distinctive crystal shape, usualy red, but not reliably so
Garnet in hand
spinel hand sample
Magnetite, easily identified by magnetic properties and oxidized metalic luster, tends to grow in oxtahedral shapes
Magnetite, easily identified by magnetic properties and oxidized metalic luster, tends to grow in oxtahedral shapes
spinel hand sample
Pyroxene silicate structure
single chains bound together by octahedral groups of the smaller catioic membe (Usualy magnesium) Larger cations glue the layers together
single chains bound together by octahedral groups of the smaller catioic membe (Usualy magnesium) Larger cations glue the layers together
Pyroxene silicate structure
exsolution in thin section (lamelle)
fracture lines appear large/bold, because that is where the unwanted stuff is being shoved
fracture lines appear large/bold, because that is where the unwanted stuff is being shoved
exsolution in thin section (Lamelle)
orthopyroxene composition
(Mg,Fe) Si2O6, also known as pidgeonite when a little calcium is added in
(Mg,Fe) Si2O6, also known as pidgeonite when a little calcium is added in
orthopyroxene composition
clinopyroxine composition
(Mg,Ca) Si2O6, also known as augite, may include some iron
(Mg,Ca) Si2O6, also known as augite, may include some iron
clinopyroxine composition
Lhersolite
a dense mixture of clino/.orthopyrocine and olivine that forms under high pressure, the olivine alighns it’s c axis along with the direction of mantle convection
a mix of clino/.orthopyrocine mixed with olivine
Lhersolite
Olivine structure
(Mg,Fe)SIO4 Has a TOT structure similar to pyroxene, alhtough it’s an ortosylicate instead of a chain. calcium glues the structures together
(Mg,Fe)SIO4 Has a TOT structure similar to pyroxene.alhtough it’s an ortosylicate instead of a chain. calcium glues the structures together
Structure of Olivine
Structure of Garnet
(Ca, Fe, Mg,)3Al2(SiO4)3. has a TOT arrangement
(Ca, Fe, Mg,)3Al2(SiO4)3. has a TOT arrangement
Structure of Garnet
