W9L2Carbonates and Evaporites

Question 1

Calcium carbonate polymorphs CaCO3

Answer 1

calcite: sedimentary rocks, marbles, oyster shells, most common
aragonite: most shells, HP metamorphic, sediments
Vaterite: rare
and many more carbonate minerals

Question 2

Igneous carbonate minerals

Answer 2

carbonatites

not as common but for ex carbonatite melts and carbonatite lavas

Question 3

Biominerlisation

Answer 3

is carbonate as biominerals

Question 4

Biomineralisation through

Answer 4

Saturation of the required elements is driven & controlled by . the secretions of plants and animals
Cell structure modifies crystal morphology

Question 5

common biominerals

Answer 5

CaCO3, SiO2 & calcium hydroxylapatite (calcium phosphate)
shells, eggshells, bone, coral

Question 6

Crystallisation in the sedimentary (surface) environment

Answer 6

growth of ‘authigenic’ minerals

• precipitation of carbonates
• evaporites
• crystallisation in hydrothermal regions

Question 7

commonest in marine environments

Answer 7

limestones

Question 8

freshwater limestones

Answer 8

travertines

Question 9

textural name: micrite

Answer 9

precipitates of finely crystalline carbonate

fine grined

Question 10

textural name: sparite

Answer 10

crystalline calcite cementing ooids , spiral shape

Question 11

textural name: ooids

Answer 11

ooids or ooliths= oolitic limestone

Question 12

Marble

Answer 12

Metamorphism of Carbonate Rock

Question 13

Metasomatism

Answer 13

hydrothermal fluids can move materials around or change there composition
happens in igneeous rocks and metamorphic terrians

Question 14

Skarns

Answer 14

Skarns - metasomatism of carbonates and/or evaporites by alkaline fluids; calc-silicate metamorphic rocks

Question 15

Evaporites occur when

Answer 15

salts precipitate from brines

Question 16

Brine dfinition

Answer 16

A brine is a low temperature, aqueous solution at the Earthʼs surface, saturated with dissolved salts

Question 17

crystal growth evaporites

Answer 17

crystal growth is initiated when brines become supersaturated as a result of evaporation of H2O → Therefore brines can only dissolve minerals that are water
soluble at 1 atmosphere pressure → Evaporite minerals typically contain Na, Ca, K, Mg, Cl, SO4, CO3

Question 18

common evaporite minerals

Answer 18

Halite NaCl, Aragonite CaCO3, Gypsum CaSO4.H2O, Anhydrite CaSO4

Question 19

Evaporite enviromnets and deposits

Answer 19

Halokinesis, Salt flows upwards to form domes
Messinian Salinity Crisis
Typical of arid alkaline lacustrine environments & some tropical shorelines (ʻsabkhasʼ)

Question 20

Fumarolie

Answer 20

a hole in a volcanic region from which hot gases and vapors issue

Question 21

Fumarole Activity

Answer 21

Incrustations of sublimates & products of acid-rock reactions occur on the throats of orifices and nearby surfaces.
activity where materials precipitate

Question 22

sulphates and sulphides

Answer 22

can also crystallize from gases