phospherites

Question 1

phospherites contain how many percent P2O5?

Answer 1

more than 15-20%

Question 2

other terms for phospherites

Answer 2

phosphate rock
rock phosphate
phosphates
phosphatites
phospherites

Question 3

sedimentary rocks with less than 20% however considered enriched in phosphorus are referred to as:

Answer 3

phosphatic

Question 4

ocean water contains what amount of phosphorus

Answer 4

70 ppb

Question 5

ancient phospherite deposits contain how many percent P2O5

Answer 5

30-40%

Question 6

in ancient phosphorite deposits, they typically occur interbedded with:

Answer 6

chert, carbonate rocks, carbonaceous mudrocks

Question 7

what is the characteristic feature of many major phosphorite accumulations?

Answer 7

triple association of phosphate, chert, and carbonaceous sediments

Question 8

grading of phosphatic rocks

Answer 8

grade regionally from phosphatic to non-phosphatic

Question 9

principal varieties of apatite:

Answer 9

chlorapatite [Ca5(PO4)3F]
flourapatite [Ca5(PO4)3Cl]
hydroxyapatite [Ca5(PO4)3OH]
francolite Ca10(PO4,CO3)6F2-3

Question 10

how is francolite yielded?

Answer 10

10 percent carbonate ions substituted for phosphate ions

Question 11

francolite is also known as

Answer 11

carbonate hydroxyl flourapatites;

carbonate flourapatite (CAF)

Question 12

other mineral associations of phosphorites

Answer 12

authigenic chert (Opal -CT)
dolomite
carbonates
carbonaceous shales
clay minerals

Question 13

common composition of phosphorites:

Answer 13

ooids, peloids, clasts, bioclasts

these grains are composed of apatite

Question 14

phosphorite that lack texture and composed of fine, micrite-like, textureless collophane

Answer 14

phospholutite

Question 15

t or f: phosphorites are cryptocrystalline

Answer 15

t

Question 16

what causes the brown/black color of phosphorites?

Answer 16

organic matter

Question 17

peloids of phosphorites may contain what kind of fossils?

Answer 17

foraminefera or radiolarian

Question 18

principal kinds of phosphate deposits

Answer 18

bedded
bioclastic
nodular
pebble-bed
guano

Question 19

the phosphorites in bedded phosphate occur as:

Answer 19

peloids
ooids
pisoids
phosphatized fossils and skeletal fragments
cements

Question 20

a special type of bedded phosphate deposit composed largely of vertebrate remains

Answer 20

bioclastic phosphorites

Question 21

bioclastic phosphorites contains remains such as:

Answer 21

fish bones, teeth, scales, comprolites

Question 22

composed of spherical to irregular-shaped nodules ranging in size from a few cms to meters or more

Answer 22

nodular phosphate deposits

Question 23

these may occur within nodules of phosphatic deposits

Answer 23

phosphatic grains, pellets, shark teeth, and other fossils

Question 24

are composed of phosphatic nodules, phosphatized limestone fragments, or phosphatic fossils

Answer 24

pebble-bed phosphorites

Question 25

explain how pebble-bed deposits are formed

Answer 25

pebble-bed deposits have been mechanically concentrated by reworking of earlier-formed phosphate deposits and has undergone diagenesis

Question 26

excerements of birds and bats leached to form an insoluble residue of calcium phosphate

Answer 26

guano deposits

Question 27

excrements of birds and bats leached to form an insoluble residue of calcium phosphate

Answer 27

guano deposits

Question 28

under what conditions is carbonate-apatite favored?

Answer 28

slightly reducing conditions

Question 29

t or f: the conditions that favor the precipitation of calcium carbonate also favor formation of carbonate apatite

Answer 29

t

Question 30

concentration of phosphorus in river water

Answer 30

20 ppb

Question 31

enumerate the ways in which phosphorus is removed from ocean water (inorganic process)

Answer 31

• precipitated with CaCO3
• biogenic concentration of vertebrates
• incorporation into metalliferous sediments as a result of absorption into metallic minerals (iron hydroxides)
• secondary sources

Question 32

limestones contain how many percent P2O5?

Answer 32

0.04%

Question 33

explain how phosphorus can be removed from ocean water through secondary sources

Answer 33

Upwelling in the oceans bring cold, deep, phosphate-rich waters onto the shallow shelf. Under this condition carbon dioxide will be lost in the water, decreasing the pressure and temp causing a rise in the pH thereby precipitation of carbonate-apatite occurs.

Question 34

on what pH does carbonate-apatite start to precipitate?

Answer 34

7

Question 35

explain the organic process of removal from seawater and precipitation of phosphorus as phosphorite

Answer 35

Organisms utilize phosphorus upwelled onto shallow shelf to build soft body tissues. After death, these organisms pile up on the ocean floor under reducing conditions where decay is inhibited. These tissues (phytoplankton, zooplankton, coprolites, bones, and scales) will then be preserved and buried into accumulating sediments. These buried tissues will start to slowly decay releasing phosphorus to the pore waters, increasing from 1440 ppb to as much as 7500 ppb. Phosphorite nodules then form within sediments during diagenesis.

Question 36

explain the two stages of physical processes in deposition and precipitation of phosphorite deposits.

Answer 36

The first stage involves upwelling of phosphate rich waters and utilization of organisms. This stage favors reducing conditions wherein phosphorus are precipitated as phosphorite nodules.

In the second stage under oxidizing and high energy conditions, these nodules are mechanically reworked by current and wave activity owing to sea level fall.