Sedimentary Mineral Associations

8/13/2019 Sedimentary Mineral Associations

1/18

The Rock Cycle


2/18

Sedimentary Processes1

2) & 3)

Sediments aretransported and

deposited

4


3/18

Products of weather ing

Primary Residual Dissolved

Minerals Minerals Ions

Feldspar Clay minerals K+, Ca+2, Na+

Aluminum hydroxide

Fe-Mg minerals Hematite & Mg+2

Limonite

Quartz Quartz Silica

Primary Solids that Ions that are carried

Minerals remain in soil away in water

----------Detrital sediments------------------ Chemical & biochemical sediments


4/18

Types o f sediment

Detritalmineral & rock fragments Chemicalhalite (NaCl)crystalsthat precipitate from water

Biochemicalshells made ofcalcite (CaCO3) by organisms

that extract the ions from water


5/18

Detrital sedimentary rocks- classified by

grain size differences

Conglomerate

Breccia

Sandstone

Shale

All these rocks have clast ictexturesthe rocks are composed ofparticles (fragments) that are cemented together


6/18

Detr i tal sediments are so rted by the pro cesses of

transportat ion and deposi t ion

Well sorted Poorly sorted


7/18

Sands and sandstones can be used to interpret the erosional

history of an area and the kinds of rocks that were eroded

Well-

sorted

Poorly

sorted

Mature sediments have little feldspar. This means that the sediment was

derived from weathered rocks or that the feldspar decomposed during

transportation in water.


8/18

The same

diagram is

used to

interpret the

provenance(source rocks)

of sediments


9/18

Placer depositaccumulation of sand or gravel containing minerals that are

highly resistant to chemical attack and economically valuable - gold, platinum,

ilmenite, rutile, zircon, diamond, garnet, magnetite, corundum, monazite.

These and other chemically resistant minerals are widely used to indicate theprovenanceof sediments, e.g. kyanite, sillimanite, staurolite

indicate that metamorphic rocks were eroded. Diamonds indicate kimberlite;gold indicates hydrothermal veins, etc.


10/18

Chemical and biochemical sedimentary rocks

Limestonescomposed of calcite

Travertine Coquina

Chalk


11/18

Deep ocean sedimentsare mainly fine-grained biochemical

sediment called oozes, with some hydrogenous(chemical)

and terr igenous (wind or water borne) detrital sediment


12/18

Calcareous & siliceous ooze

Manganese nodules are

hydrogenous - they

precipitate from deep ocean

water when the Mn oxidizes:

Mn+2(dissolved) + O2+ 2e- =

MnO2(pyrolusite)


13/18

Banded Iron Format ionsancient (>2.5 billion year old) sedimentary deposits of iron-

bearing minerals. These indicate that Earths early atmosphere was too poor in oxygen to

oxidize iron at the site of weathering. Dissolved iron was transported in water:

4Fe+2(dissolved) + 3O2= 2Fe2O3(hematite)


14/18

Phosphates form in shallow marine environments where dissolved PO4-3

is carried by upwelling of deep ocean water. These areas are biologically

productive - many fossils are found, especially bone material.


15/18

Phosphate Mining of the Bone Valley Formation in Florida


16/18


17/18

Evapori tes

Gypsum

Halite

Seawater evaporation:

1) Calcite

2) Gypsum

3) Anhydrite

4) Halite (95% evaporation)

5) Sylvite

6) Other rare minerals

Dolomite may form afterward by

reaction of Mg+2with calcite

Continental waters:Borax & borates

Nitrates


18/18

Salt

dome

Sulfur is

produced by

sulfate

reducingbacteria

which

consume the

oxygen in

gypsum oranhydrite

Sedimentary Mineral Associations

Documents

Transcript of Sedimentary Mineral Associations