lecture 10, 12
Terms
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-
oceanic crust recycled by?
continental crust? -
plate tectonics
weatherng, erosion, deep melting - oceanic crust age
- 200 my, avg 70 my
- continental crust age
- 3800 my, avg 650 My
- abyssal plains
- cool, subsided
- active margin
- convergent or transform fault, earthquakes, volcanism
- passive margin
- tectonically quiet
- cont. shelf
- submerged continental crust, 25%, gently sloping
- cont. slope
- steep slope, overjoin with cont. and oceanic crust
- cont. rise
- gently slope
- proton
- pos, ~ 1 amu
- neutron
- 0, ~1 amu
- electron
- neg, ~.00055 amu
- nucleus
-
protons, neutrons,
very small, dense - electrons in orbitals
- organized by energy shells
- electrically neutral
- electrons=protons
- element
-
unaltered in chemical reaction
- fundamental substances into which matter can be separated by chemical means - atom
- smalles unit with properties of an element
- Z
-
number of protons in nucleus
, 1<Z<92 - Atomic mass
-
Z + N
1,A,238 - isotopes
-
atoms of same element (Z number)
- same chem. behavior
- diff, nuclear behavior
different number of neutrons - radioactive decay
- spontaneous, nucleus of one element > nucleaus of another
- periodic table
-
elements arranged by Z number
- rows- energy level
- columns- groups, same electron configuration, chemical similarities - inert/ noble gas
-
no tendancy to react
fall energy - continental crust, elements
- O, Si, Al, Fe, Ca, Mg, Na, K
- whole earth, elements
- Fe, O, Si, Mg, Ni, S, Ca, Al
- abundant elements are
- light
- compounds
- elements chemically bonded in definite proportions
- bonding
- electrons attracted to each other
- pure elements in nature
-
gas- h2, n2, o2, he
liquid- Hg
solid- au, ag, pt, cu, s, c - ion
- atom which has gained or lost one electron
- cation
- loss of election- + charge
- anion
- add election- - charge
- complex ion-
-
bonded group of atoms with net positive or net negative charge
CO3-2 - ionic bonding
-
complete e- transfer
attraction of opposite charges - covalent bonding
-
equal e- sharing
ex. some pure elements like N2, Diamond - real bonds
- incomplete transfer, unequal sharing
- regularities in periodic table
-
noble gases, no ions
o group, f group- anions
otherwise- cations - continental crust made up of
- O-2 and Si+4
- mineral
- natural, solid, specific chemical composition, characteristic crystal structure
- polymorph
- same compostiion, different structures
- minderal properties
-
- crysatl form
- cleavage
- color, streak
- hardness
- density, specific gravity - cleavage
-
tendancy to break along planar surfaces
- preferred orientation
- relatively weak bonding
NaCl - color
- reflects composition
- hardness
- releative resistance to scratching
- moh scale
-
measures harness
10- diamond
1- talc - density
- mass/ volume
- most cont. crust minderals are
- 2.5-3 g/cm^3
- specific gravity=
- mass/mass of equal vol. of water
- silicate minerals
-
classification by anion
- based on SiO4 4- tetrahedron - reduce net negative charge by O sharing
- polymerization
- silicate mineral classes
-
single tetrahedron(no O sharing)
ring structures (+ cations)
single chains (+cations)
double chains
sheet structures
3 d networks - single tetrahedron
-
no O sharing, cations,
olivine, garnets - ring structures
-
cations
beryl, ore of Be - single chains
-
cations
pyroxenes
rockforming - double chain
-
cations besides Si 4+
amphiboles
rock forming - sheet structures
-
cations besides si 4+
micas- fillers, insulators
clay minerals- fillers, ceramics, absorbents - three dimensional networks
- quartz, felspars
- as single tetrahedron moves towards a 3-d network
-
0 sharing increases (polymerization)
atom ratio decreases
electrical charge per Si(-4-0) - ferromagnesian minerals
-
high Fe, dark, dense
olivine, pyroxene, amphibole, biotite - non silicate minerals (by anion)
- sulfides, oxides, halides, carbonates, sulfates
- sulfides
-
galena- ore of Pb, batteries
spahalerite- ore of zn, brass
chalcopurite- ore of Cu - oxides
-
hematie
magnetite
al oxide - halides
- NaCl, evaporation of seawater
- carbonates
- calcium carbonates- calcite, aragonite
- sulfates
- evap of seawater, second most abundant anion
- phosphates
-
ca phosphate, apatite
vertebrate bones, teeth
ionic substitution
fertilizer phosphoric acid - pyroxens
- rock forming minerals
- mineral deposit
- volume of rock enriched in one or more minerals
- ore
- mineral deposit from which minerals can be extracted profitably
- profitability
-
grade of deposit, concentration of mineral/element of interest
- require enrichment relative to avg. - costs of production
- mining, benefication (removal), gangue(worthless mineral components), refinery, transporation to market
- gold stable from:
-
1935-1971
35$ a troy oz. - depletion allowance
- deducaiton from taable income based on eventual exhaustion of resource
- resource
- concentration of material currently or potentially economically feasable
- reserves
- exonomically extractable at present
- hypothetical resource
- known mining distric undiscoveresd deposits
- speculative resource
- geologic settings similar to known deposits
- rock
- naturally formed, non living, firm, coherent, solid
- 2 elements of rock classification
-
mode of origen, properities of specimen
- minerals, chem composition
- ttexture- grains, grain size, shape orientation - lithification
-
interlocking grains, growth from fluid
cement mineral in spaces between grains -
rocks strong in
rocks weak in -
compression
tension - sediment
- regolith that has been transported and deposited
- metamorphism
- changes due to elevated T,P
- magma
- molen rock, suspended grains, dissolved gases
- total cont. crust
- 95% igneous, 5 % sedimentary
- surface crust
- 75% sedimentary, 25% igneous
- intrusive
- cooled within crust, slowly
- extrusive
- colled at surface or seafloor, rapidly
- phaneritic
-
visible to the eye
- intrusive=large grains - aphanitic
-
visible only with magnification
extrusive, obsidian - porphyritic
-
large grains in fine matrix
slow-phenocrysts, rapid- matrix - grain packing
- lithification by interlocking grains
- common minerals:
- silicates such as olivines, pyroxens, amphiboles, micas feldspars, quartz
- pyroclast
- rock ejected during volcanic eruption
- tephra
- unlithified cumulation of pyroclasts
-
bomb
lapilli
ash - >64 mm in diameter fall close in
- lithification of igneous particles
- particles fuse together while still hot, ementation
- minerals typical of extreme compostitions
-
granite- Na feldspar
basaltic- Ca feldspar