evaporites

Question 1

are chemical sedimentary rocks derived from a precipitation of mineral ions in response to evaporation of water in a solution

Answer 1

evaporites

Question 2

evaporites starts precipitating from _________ to _________ to ________

Answer 2

dilute to saltwater to supersaturated (brine)

Question 3

how are brine solution formed?

Answer 3

if there is no recharge in the water

Question 4

evaporite forms on:

Answer 4

marine to marginal to non-marine

Question 5

t or f: continental evaporites are from a dilute solution

Answer 5

t

Question 6

which of the following has the slowest depositional rates? explain why.

a. marine
b. marginal
c. non-marine

Answer 6

c. non marine

because of the dilute nature of its solution

Question 7

evaporites are mostly composed of:

Answer 7

halides and sulfates

Question 8

what causes alkaline mixes in lake evaporites?

Answer 8

dissolved feldpsars

Question 9

between lakes and seawater evaporites, which of the two precipitates much earlier?

Answer 9

sea water

Question 10

evaporation sequence of lake evaporites:

Answer 10

1. CaCO3 (Calcite)
2. CaSO4 (Gypsum and Anhydrite)
3. NaSO4 (Hanksite)
4. NaCO3 (Trona and Natron)
5. MgSO4 (Epsom salts)
6. NaCl
7. MgCl2 and CaCl2 lakes are rare (bitterns Dead Sea)
8. If all water evaporates - bed of salt (NaCl) usually results

Question 11

evaporation sequence of seawater evaporites:

Answer 11

1. CaCO3 (calcite)
2. CaSO4 (gypsum and anhydrite)
3. NaCL (halite) - precipitates if 86-94% of original seawater has been removed
4. Potassic salts - if >94% of original seawater has been removed

Question 12

temperature where gypsum and anhydrite precipitates:

Answer 12

gypsum - <42 degrees celsius
anhydrite - >42 degrees celsius

Question 13

which compound precipitates first?

a.) high solubility
b.) medium solubility
c.) low solubility

Answer 13

low solubility

Question 14

types of anhydrite

Answer 14

nodular
laminated
massive

Question 15

lumps of mosaic anhydrite are separated by:

Answer 15

dark carbonates / mud / clay

Question 16

chickenwire anhydrites are separated by:

Answer 16

thin dark stringers

Question 17

evaporite sequence with percentage

Answer 17

CaCo3 100%
CaSO4 19%
NaCl 9.5%
NK and Mg salts 4%

Question 18

arrangement of environments in increasing salinity

Answer 18

open marine basin
euxinic basin
shallowing basin
playa/salina

Question 19

ephemeral lake

Answer 19

playa

Question 20

three basin models for evaporites and explain each:

Answer 20

1. deep water; deep basin model
   - produces more CaCO3 because mas diluted sya and slow and rate ng precipitation because hindi masyado ma initan. may presence ng lamination among different evaporites because of periodic recharge and gravity influence
2. shallow water; shallow basin
   - brine ang solution so most likely may NK and Mg salts, meron din presence ng prograding sediment deposition
3. shallow water; deep basin
   - brine din ang water so shallow water evaporites din and ma deposit

Question 21

two deposition models and explain

Answer 21

1. bulls-eye pattern
   - wala masyadong recharge because isolated yung basin, first to deposit is outside the rim, the most saturated solution evaporites is in the center
2. teardrop pattern
   - may recharge so the depth of water in the center is maintained. center ang pinka diluted so dun ang first evaporites na mag deposit, sa outer rim naman ang pinaka saturated

Question 22

ephemeral river

Answer 22

sabkhas

Question 23

three depositional environments of evaporites:

Answer 23

1. subaerial evaporites - sabkhas, playas, salt flats, both marginal and continental
2. shallow subaqueous evaporites - salinas, marginal marine environment/coastal,
3. deep-water evaporites - thin bedding and lamination

Question 24

The process of erosion and oxidation that occurs when sedimentary rocks undergo uplift quotations

Answer 24

telogenesis

Question 25

explain how diagenesis affects gypsum and anhydrite

Answer 25

burial diagenesis dehydrate gypsum and transform it into anhydrite

telogenesis rehydrate anhydrite (exhumation) and transform it to gypsum

Question 26

pressure dissolution

Answer 26

stylotization

Question 27

explain the conditions of aral sea:

Answer 27

aral sea was once a lake that dried up because the level of extraction is greater than the recharge, thereby resulting in a very brine solution that eventually precipitated