Day 2 Purgatory Flashcards
can determine whether a suite of rocks is related through a process such as magmatic differentiation or mixing.
Major element geochemistry
is used to identify the role various minerals may have played as either crystallizing phases or residual phases in a suite of rocks.
Trace element geochemistry
and stable isotopes, can determine whether a suite of rocks formed from a single magma, or whether a more complex, multisource process was involved.
Isotope geochemistry
What does the AP line in the QAPF plot represent
line of SiO2 saturation
contain complete crystal faces that are not impinged upon by other crystals
Euhedral
contain partially complete crystal forms in which at least one of the crystal faces is impinged upon by adjacent rock material
Subhedral
crystals lack any observable crystal faces
Anhedral
contain small crystals less than 1 mm in diameter that are not generally discernible to the eye
Aphanitic
characterized by large crystals averaging more than 30 mm in diameter
Pegmatite
igneous rock that consist of two distinctly different size crystals
Porphyritic
frequently used to refer to volcanic materials ejected from a volcanic vent
Pyroclastic
fragments form by mechanical friction during movement of lava and breakage of cool brittle
outer margins, or gravity crumbling of spines and domes Reworking
Autoclastic Fragments
Volcaniclastics that are formed by magma-water interaction
Hydroclasts
clasts of volcanic composition derived from erosion of volcanoes or ancient volcanic terrane with no volcanic edifice
Epiclasts
Nearly molten bombs, usually basaltic, that readily weld upon impact to form agglutinate
Splatter
Less vesicular than pumice sinks in water more mafic than pumice no size limitations
Scoria
Lapillus size particles formed by concentric accretion of ash
Accretionary Lapilli
Particles ( lithic, vitric) derived from new magma
Essential (juvenile)
Particles derived from earlier eruptions at same volcanic center
Accessory (Cognate)
Particles of any origin or composition from rocks through which the vent penetrates
Accidental
grains with rectangular tablet shapes
tabular
if the rock contains numerous holes that were once occupied by a gas phase, then
vesivular
a texture consisting of intergrowths of quartz and alkali feldspar wherein the orientation of the quartz grains resembles cuneiform writing
Graphic
grains that have all of their boundaries of approximately length
Equant