Rock Determination HydroGeo Flashcards
The three types of rocks
igneous, metamorphic, sedimentary
What are the two types of igneous rocks and how were they formed?
intrusive - formed in earth, solidified slowly, small minerals
extrusive - cooled quickly outside the earth, coarser minerals
What is the basic silica structure?
SiO4 - this has a charge of -8 and is often compensated by Fe or Mg. This is known as the olivine group
What is the pyroxene group?
one line of SiO4 minerals
What is the amphibole group
a layer of double structures
What are phyllosilicates?
platy minerals
What is the tectosilicate group?
a 3D structure
What are felsic igneous rocks?
extrusive rocks formed from explosive volcanoes - higher SiO2
What are mafic igneous rocks?
Extrusive rocks formed from fluid volcanoes - lower SiO2
When does weathering occur more quickly with rocks?
When there are more metals - these are easier to weather than chemical bonds - van der Waals forces are easier to break than chemical bonding
Granite
intrusive igneous rock. Lightly coloured with a mix of light and dark silicates. Mainly light minerals. The darker minerals weather first. Same chemical composition as rhyollite. Weathers slower than rhyollite, unless fractured
Diorite
Intrusive Igneous Rock. 50/50 distribution of light and dark silicates. Doesn’t weather fast. Same chemical composition as Andesite
Gabbro
Intrusive igneous rock. Predominantly large dark minerals. Same chemical comp. as basalt , but weathers slower (larger minerals) unless fractured.
Rhyolite
light extrusive igneous rock. Small minerals, high viscosity when forming. Rare, so usually solidifies inside the earth. Weathers faster than granite –> smaller minerals
Andesite
50/50 extrusive igneous rock. Has more dark minerals than rhyolite. Twins with diorite
Basalt
dark extrusive igneous rock. Lots of metal ions. Rock forms in polygones during cooling and solidification process. The scrambled egg on top has higher porosity, volcanic gas causes bubbles.
Tuff
volcanic ash and lava bombs fall back on the earth. When it cools in the air, aquifer, when it cools on the surface, aquitard.
Two types of diagenesis
reduction of volume (compression/compaction at large depth), mineralogical change (chemical processes between core and water minerals)
eg. consolidated coarse clastic sediment
conglomerate
eg. consolidated moderately coarse clastic sediment
sandstone
eg. consolidated fine clastic sediment
siltstone, shale
arenite
consolidated rocks constructed from sand size particles.
lutite
consolidated rocks with smaller than sand size grains
rudite
consolidated rocks with larger than sand size grains
organic vs. clastic limestone
organic - chalk skeletons of algae, sea shells and organisms, clastic is from transported skeleton gragments or from calcite crystals.
slate
fine grained rock, developed from clayk strong cleavage preference in one direction.
Phyllite
slightly coarser rock than slate with silvery or greenish lustre, minerals not visable, developed from low graded metamorphosed clay
Schist
coarse grained rock with parallel structures and clearly visible micas.
Gneiss
coarse grained with clearly visible parallel structures of micas and fedspars, characterized by coarse layering. High grade metamorphose. no porosity or conductivity
Granite to sand (types of sand)
monocyclic sand - darkest minerals weather fter - weaker van der Waals forces.
polycyclic sand - multiple cycles of weathering - even fewer darker minerals.
sand to sandstone
poorly consolidated - still has porosity- to highly consolidated (no pores). high pressure and temp required. sandstone weathers faster than rain.
you can still see sand in sandstone
quartzite to magma
make it hotter
silt to siltstone
silt –> consolidated siltstone (sedimentary) –>highly consolidated siltstone (metamorphic)
gravel to conglomerate to quartzite
gravel –> burial and lithification –> conglomerate –> breccia –> quartzite
Metamorphic -> high temp, pressure, long time.
clay to shale
burial and lithification - pushed in same direction
shale to phyllite to slate
metamorphic formation, dull colours
shale to schist
metamorphic –> colourful.
granite to gneiss
metamorphic
carbonate sequencing
calcium carbonate –> cretaceous chalk –> carboniferous limestone
hardness
on a scale of 10 - silica dominated is roughly 6-7, chalk is 3
limestone –> marble
no porosity or hydraulic conductivity anymore, still on chalkboard :)
metamorphic transformation
Flintstone
silica skeleton creatures, found in chalk
gypsum
calcium sulphate
