Page 70 - Petrology of Sedimentary Rocks

RELATIVE ABUNDANCE OF MINERALS IN THE SEDIMENTARY ROCKS

TERRIGENOUS MINERALS, derived from 3HEMICAL MINERALS, precipitated
erosion of source lands; comprise 60% to from solution within the basin of
80% of the stratigraphic column. deposition; comprise 20% to 40% of
the stratigraphic column.
QUARTZ, **35-50%

:ARBONATES,** 70%-85%
CLAY MINERALS 25-35% (Authigenic al- Calcite 2/3 to 3/4; dolomite l/3 to
teration common). Main types: I /4; aragoni te, sideri te, ankerite
“Sericite”* (impure fine minor
grai ned muscovi te,
HKA I SiO). SILICA IO-I 5%
III i te group* (HKA I SiO) (mostly quartz and chert; a little
Montmorillonite group* opal)
(HMgAISiO)
Chlorite group* (HMgFeA I SiO SULFATES AND SALTS** 2-7%
with Si low, FeMg high). (Chiefly gypsum, anhydrite, halite;
Kaolin group* (HAISiO) some sylvi te and other K salts; a
Bauxite group* (HAIO) (not little barite, etc.)
strictly a clay)
MISCELLANEOUS 2-7%
METAMORPHIC ROCK FRAGMENTS 5- (Feldspar, hematite, limonite, leu-
15%
(not a mineral; includes detrital par- coxene, pyrite,** phosphates, glau-
ticles of slate, phyllite, schists, coni te, manganese, tourmal ine, zir-
zeolites
and a
con,
anatase,
rutile,
metaquartzi te)
good many others).
FELDSPAR** 5- 15%
(K feldspar considerably more abun-
dant than plagioclase)
CHERT** l-4%
(mostly reworked from older cherty
limestones)
COARSE MICAS” 0. I-0.4%
(Muscovite HKAI SiO by far most
common; some Biotite
HKMgFeA I SiO and Chlorite You are required to know the exact
HMgFeA I SiO) chemical formulae of the minerals
marked **, and of all the minerals
CARBONATES I .2- I % named under the groups marked **.
(reworked fragments of older lime- Know the chief elements listed for each
stones)
mineral marked *. A good knowledge of
ACCESSORY (HEAVY) MINERALS 0. I - the chemistry of earth minerals is vital
1.0% to understanding their behavior in the
Opaques**: sedimentary environment.
Magnetite, Ilmenite, Hema-
tite, Limonite and Leucoxene
U I trastable group
Zircon**, Tourmaline, Rutile
Less stable group:
Garnet, Apati te, Kyanite,
Stauroli te, Epidote, Horn-
blende, Pyroxene and about
IO0 others of minor impor-
tance volumetrically.
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