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Sedimentære bjergarter Flashcards

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1
Q

Hvilke otte typer af sedimentære bjergarter er der

A

Siliciclastic (terrigenous)
Carbonate
Siliceous
Coal
Evaporites
Pyroclastics
Ore stones
Phosphates

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2
Q

Hvordan inddeles siliciclastiske sten

A

Pelites - Arenites - Rudites

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3
Q

Hvad kende tegner pelites

A

Siliciclastic (terrigenous)
silt - mud
claystone - siltstone

under 63 mikrometer

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4
Q

Hvad kendetegner Arenites

A

Siliciclastic (terrigenous)
Sand
Sandstone

under 2 mm

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5
Q

Hvad kendetegner Rudites

A

Siliciclastic
Gravel >33%
Conglomorate + breccia

Under 4000 mm

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6
Q

Hvordan inddeler man arenites

A

Arenites (feldspatic or lithic arenite)
Wackes (feldspatic or lithic wacke)
Mudstones

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7
Q

Hvordan inddeler man rudites

A

Runded gravels = conglomorate
Angular gravel = breccia

Monomict: One type of gravel
Oligomict: Few (2 – 3) types of gravel
Polymict: Numerous types of gravel

Type of matrix (matrix can be a sandstone for instance!)

Matrix-supported conglomerate: Diamictite

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8
Q

Hvilke typer kalksten er der

A

Kalkssten = HCl
CaCO3
Dolomit = varm HCl
CaMg(CO3)2

Hvis det er blandet kalksten bruger man samme inddeling som i siliciclastiske, men det hedder
Conglomorate = rudite
Sandy calcarenite = arenite
Marl (calcipelite) = pelite

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9
Q

Hvad er de primære allochemes i carbonates?

A

(components)

Bioclasts (skeletal material)
- Ooids
- Peloids
- Intraclasts

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10
Q

Hvilke tre slags ooids findes der

A

Peloids <1mm
Ooids <2mm
Pisoid >2mm

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11
Q

What is the difference between an ooid and a
peloid?

A

peloid er meget små - micrite - inden internal struktur

ooid - runde - dannet af flere lag uden på hinanden - større end peloids

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12
Q

What is sparite

A

Carbonate cement

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13
Q

Biogenic siliceous

A

SiO2

Diatomite, sponge spicules, radiolaria

Chert, flint

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14
Q

Rækkefølge af evaporitter

A

Calcit (CaCO3) + dolomit (CaMg(CO3)2)
Gips (CaSO4∙2H2O)+Anhydrite(CaSO4)
Halit (stensalt, NaCl)
Sylvite (KCl)

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15
Q

Rækkefølge af evaporitter

A

Calcit (CaCO3) + dolomit (CaMg(CO3)2)
- 1/2

Gips (CaSO4∙2H2O)+Anhydrite(CaSO4)
- 1/3

Halit (stensalt, NaCl)
- 1/10

Sylvite (KCl)
- 1/20

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16
Q

Hvilken type pyroclast findes der

A

> 64 mm Pyroclastic breccia
2–64 mm Lapillituff
< 2 mm Coarse-grained tuff
< 1/16 mm Fine-grained tuff

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17
Q

Hvor meget metal skal der være i en ore stone

A

> 15%
Ofte jern

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18
Q

Hvad karakteriserer phosphater

A

P2O5 5-37%

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19
Q

På hvilken måde påvirker vand sedimentdannelse

A

Temperatur (2x pr 10 C)
Mængde nedbør
Syrligheden af nedbør
Draniage bassins hældning
Vegetation

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20
Q

Hvad er rækkefølgen for stabile mafiske mineraler

A

Olivin
Augit
Hornblende
Biotit
K-feldspar
Muskovit
Kvarts

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21
Q

Hvad er rækkefølgen for stabile felsiske mineraler

A

Ca-plagioklas
Na-Ca-plagioklas
Na-plagioklas
K-feldspar
Moskovit
Kvarts

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22
Q

Hvad betyder at en bjergart er congruent

A

Proportionen mellem elementer i opløsningen er den samme som proportionen mellem elementer i bjergarten

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23
Q

Hvilke bjergarter er congruent

A

Carbonater + evaporitter

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24
Q

Hvilke bjergarter er incongruent

A

Siliciclastiske

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25
Weathering af siliciclastiske bjergarter
Acid hydrolysis Sker især i sprækker Danner både faste og opløste stoffer til dannelse af nye bjergarter Især lermineraler
26
Hvilken effekt har flodens transport på sedimenter
Sorterer dem og afrunder dem
27
Hvad er Sorby Pricippet
Mere end 90% af carbonater fundet i morderne miljøer er af biologisk oprindelse
28
Hvilke forskelle er der i fersk og marint sammensætning af ioner
Mere Na+ i havvand Mere Ca2+ i fersk vand
29
Hvilke forbindelser er optræder i et system med opløsning af CO2 i vand
CO2 HCO3- CO3 2-
30
Hvilken forbindelse mellem vand og CO2 er der mest af ved havoverfladens pH på ca 8,2
HCO3 -
31
Ved hvilken pH vil man se CO2
4,5
32
Ved hvilken pH vil man se CO3 2-
11
33
Hvad står DIC
dissolved inorganic carbon
34
Hvilke carbon partikler har ikke biologisk oprindelse
Ooids
35
Hvilke tre kilder er der til dannelse af micrite
fysisk eller biokemisk precipitation døde alger lavet af caco3 fysisk eller biologisk slid på skeletmaterialer
36
Hvilke former kan fordampede søer have
Bulls eye Teardrop Evaporitter der dannes først vil ligge yderst i lukkede søer -
37
Hvad er Goldichserien
Viser hvor stabile mafiske og felsiske mineraler er - hvor lette er de at forvitre
38
Hvordan dannes lermineraler
Kommer ofte fra forvitring af silicat mineraler Forskellige lermineraler dannes under forskellige klima og weathering miljøer Kaolinite: warm & humid, acid weathering conditions from the alteration of feldspar-rich rocks. Illite: weathering of feldspars and micas under alkaline weathering conditions where significant leaching of mobile cations such as potassium does not occur. Smectites: drier climate, weathering of igneous rocks under alkaline conditions
39
Hvad er forskellellen på fysisk erosion og kemisk forvitring
Fysiske processer Kemisk nedbrydning af stof Mere erosion = mere forvitring Friske overflader skabt af fysisk erosion har potentiale for mere forvitring Forvitring gør overflader svagere, så de nemmere kan eroderes
40
Hvad er lermineraler lavet af
Lag af Si og O - thetraheder Lag af O og hydroxyl med Al i midten - octrahedral Kationer inde mellem lagene Evt også vandmolekyler mellem lagene
41
Hvad er siliciclastiske mineraler lavet af
Mafiske - Olivin, augit, hornblende, biotit Felsiske - Ca-plagioklas, Na-Ca-plagioklas, Na-plagioklas Begge dele - K-feldspar, Muskovit, Kvarts
42
Hvilken formlen viser Carbonate saturation state
Omega Når O >1 - mineraler dannes Når O < 1 - mineraler opløses
43
Hvad er carbonater lavet af
Carbonat = CO3 2- Langt mest biologisk oprindelse CaCO3 - cacit CaMg(CO3)2
44
Hvad står DIC for
dissolved inorganic carbon CO2 + HCO3- + CO3 2-
45
Sedimentary bassins
Dannes af tektonisk aktivitet Rift basins – divergent plader Passive margin basins – non-plate-boundary continental edge - havet shelf Intracontinental basins – interiors far from margins - inde i lande Foreland basins – ved bunden af bjergside
46
Hvad kaldes et matrix-supported konglomarat
Diamictite
47
Hvad bruges Dunhams klassifikation til
Opddele carbonater Inddeles efter tekstur Mudstone - wacke - packstone - grainstone Boundstone
48
Hvad er en boundstone
En sten hvor de originale sedimenter er bundet sammen da de deposeres
49
Hvad er diagenese
Processen der binder sedimenter sammen
50
Kan der være diagenese når en bjergart allerede er dannet
Ja Mineralogien og teksturen kan stadig ændres
51
Hvilke typer diagenese finde der
Eogenesis: early diagenesis that occurs between deposition and burial, at or near the surface. Mesogenesis: middle-stage diagenesis that occurs after burial. Telogenesis: late stage diagenesis that occurs after reexposure of formely buried rocks.
52
Hvilke generelle ting sker der under diagense
- Compaction - Recrystallization - Solution (including pressure solution) - Cementation - Authigenesis (neocrystallization) - Replacement (including neomorphism) - Bioturbation
53
Hvad sker der i ler og muddersten under diagenese
compaction, authigenesis and replacement with lesser amount of solution, recrystallization, and cementation.
54
Hvilken effekt har compaction på sedimenter
Reducerer tykkelse op til en faktor 10 Op til 60-70 volumen% af vand fjernes Porøsiteten mindskes Forskellige slags sedimenter påvirkes mere eller mindre af compaction - også i samme bjergart
55
Hvad sker med lermineraler ved dybere begravelse
Kaolin bliver til smectite bliver til illite
56
Hvilke processer mindsker porøsiteten i konglomarater og sandsten
Cementation, authigenesis, pressure solution and replacement are the most significant processes of porosity reduction. Kun lille effekt af tryk
57
The main cementation processes in siliciclastic and carbonate sediments
Lithification Opløsning Vand
58
Hvad er hardground (diagenese)
Evidence for early lithification
59
Clastic rocks are
formed from particles of other rocks. Volcaniclastic, Terrigenous and carbonates
60
Which rocks belongs to the non-clastic rocks?
Carbonates, evaporites, coal, phosphates and ironstones
61
Monomict, Oligomict, Polymict
One type of gravel (mono) Few (2-3) types of gravel (oligomict) Numerous types of gravel (Polymict)
62
What type of matrix does a rudite have?
Often sandstone
63
Main types of carbonates
Limestone and Dolomite
64
Allochem
Components
65
What are the main allochems?
Bioclasts, ooids, peloid, intraclasts
66
Which ways do we classify carbonate rocks?
Folk classification (Composition) and Dunham classification (texture)
67
Ortochems
Cement or Micrite (cement is a recrystallization of micrite, or cement can be a precipitation of ions from fluids in pores)
68
What characterises wackestone?
A matrix-supported rock with more than 10 % clasts, and less than 10% of grains >2mm. Has a graded structure, where grain size gets smaller upward.
69
Bioherm
Mound- or lens-shaped structures composed mainly of the skeletons or shells of carbonate-secreting organisms. Some are true, in situ reefs, whilst others formed as banks of loose, transported skeletal material. (for example corals and bryozoans). These structures create topography.
70
Biostrom
Ribbon or sheet-shaped structures, made largely of skeletal material, either in growth position (reefs in the strict sense) or transported. (for example Oysters)
71
Controls on sediment and dissolved loads
Temperature Precipitation (ca. runoff - Provides water for weathering and eases erosion) Seasonality of precipitation Acidity of precipitation Average elevation of the drainage basin Vegetation
72
Weathering of silicate minerals
produces insoluble iron oxides and clay minerals Acid hydrolysis
73
Eogenesis
Early diagenesis that occurs between deposition and burial, at or near the surface.
74
Mesogenesis
Middle-stage diagenesis that occurs after burial
75
Telogensis
Late stage diagenesis that occurs after reexposure of formely buried rocks
76
What factors dictate at which degree the different diagenesis processes operates?
? Composition of sediments, pressure, temperature, compositions of intergranular fluids, amount of fluids
77
What factors dictate at which degree the different diagenesis processes operates?
? Composition of sediments, pressure, temperature, compositions of intergranular fluids, amount of fluids
78
Creation of Cement
Quartz or calcite Made from precipitation of minerals within porespaces. It takes place by growth of cement on a small grain (syntaxial overgrowth)
79
What is the link between clay minerals and climate?
Erosion happens faster when it is warm. And at the equator, we find monsoon rain, which moves clay minerals to the coast.

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