Chemical and Biochemical Rocks

8/3/2019 Chemical and Biochemical Rocks

http://slidepdf.com/reader/full/chemical-and-biochemical-rocks 1/17

Keenan

Veneracion

Kristia

Alcantara

CHEMICAL AND

BIOCHEMICAL ROCKS



Minerals INSOLUTION

Not dependent on

currents or energyParticle size is not

important inclassification

Classified on thechemistry of thedominant minerals

CHEMICAL AND BIOCHEMICAL

ROCKS



- forms when minerals that are dissolved in

a solution crystallize.

Examples:

Inorganic limestone

Chert

Rock salt

Gypsum

CHEMICAL ROCKS



Composed of the mineral calcite (CaCO3 -

calcium carbonate), and are thus all known ascarbonates.

F

ormed when calcite that is dissolved in lakes,seas, or underground water comes out of solution and forms crystals

Tends to be mixed together in variouscombinations in the rocks.

Are extremely abundant and important(ex:construction materials, abrasives, agriculturalsoil treatments, construction aggregates,pigments, pharmaceuticals and more)

INORGANIC LIMESTONE



Limestone Dolomite

IMAGES OF CARBONATES



Composed of SiO2

Forms from the recrystallized skeletons of

"animals" (single celled radiolarians, and glass

sponges) or single celled "plants" (diatoms,silicoflagellates)

Although the silica comes from skeletons, to

become chert it must be chemically recrystallized,

thus putting it in the chemical category

CHERT



CHERT



Rock salt (hali te; NaCl) and gypsum/alabaster (CaSO4 .

H2O)

Originally are dissolved in the sea water, making the sea

salty

When sea water evaporates in a closed area, such as a

lagoon, the salt concentration becomes very high,

supersaturated, and precipitates out

The process is common in desert areas, with examples

today in the Red Sea and Dead Sea in the Middle East, both

highly saline.

Normal ocean waters conta in about 34,500 ppm TDS (Total

Dissolved Solids). If the concentration reaches about

100,000 ppm TDS, then gypsum wil l begin to precipitate

from the water. At a salinity of 350,000 ppm, Halite wil l

begin to precipitate.

EVAPORITE ROCKS



Rock Salt (halite) Gypsum

IMAGES OF EVAPORITES



- Forms when the remains of plants andanimals are deposited in thick layers. Theterm organic refers to substances that were

once part of living things or were made byliving things.

- Examples:

Biochemical limestone

Peat

Coal

BIOCHEMICAL ROCKS



The hard shel ls of l iv ing th ings produce some k inds of l imestone.

In the ocean, many l iv in g things including coral, c lams, oysters, andsnai ls , have shel ls or skeletons made of calc i te. W hen these animalsdie, their shel ls p i le up as sediments on the ocean f loor.

Over mil l ions of years, these layers of sedim ents can grow to a depth of hundreds of meters.

Slowly the pressure of overlying layers compacts the sedim ents.

Some of the shel ls d issolve, forming a solut ion of calc i te that seeps intothe spaces between the shel l f ragments.

Later, the dissolv ed material comes out of solut ion forming calci te.

The calc i te cements the shel l par t ic les together forming inorganicl imestone.

BIOCHEMICAL LIMESTONE



BIOCHEMICAL LIMESTONE

An organic limestone

organisms with shells or

skeletons

death

Shells or skeletons piling up as

sediments; compacted by pressure

of overlying layers



A plant matter that is par tially decomposed under conditions of no oxygen.

When dug from the ground, peat is about 75 percent

water by weight; once dried it is about 60 percentcarbon and makes a useful fuel in many regions.

Peat forms large and widespread deposits in thenorthern latitudes, where wet ground (peat bogs andfens) and abundant plant growth favor its preservation.

Peat turns slowly into coal with burial and pressure asgentle heat drives out light hydrocarbons. Thesevolatile compounds become petroleum.

PEAT



Uses of Peat: horticultural and agricultural uses; energy

uses

Unlike all the other chemical/biochemical rocks, peat and

coal always form in the presence of clastic rocks -

sandstones and shales

PEAT



Forms from the remains of swamp plants buried in water

As layer upon layer of the plant remains build up, the weight of the layers squeezes the decaying plants.

Then over mill ions of years, they slowly change into coal.

Uses of Coal: energy uses (mainly as fossil fuel)

Bituminous coal

COAL



http://www.windows2universe.org/earth/geology/sed_chemic

al.html

http://cmsc.minotstateu.edu/Labs/rockslab/sedimentary/Che

mical%20sedimentary%20rocks.html

http://csmres.jmu.edu/geollab/fichter/SedRx/sedclass.html

'Prentice Hall Exploring Earth Science '

(1995; Prentice Hall)

SOURCES



THANK YOU!

Chemical and Biochemical Rocks

Documents

Transcript of Chemical and Biochemical Rocks