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Chapter 13 Diagenesis
MAJOR MINERAL REACTIONS IN DIAGENESIS
(SIMPLIFIED, NOT BALANCED)
SILICATES
UPTAKE OF
RELEASE OF
I K-FELDSPAR
- ? 1 KAOLINITE I
+ K + Si02
2
I Ca-PLAGIOCLASE I + Na + Si0 2 ~ I ALBITE I
+ Ca
3
I SMECTITE 1
+ K
- ? MIXED-LAYER + Si0 2 + (Ca, Mg, Na)
OR ILLITE
+ H 2 0
4
I SMECTITE I + Fe, Mg ~ I CHLORITE I
5 I KAOLINITE I +1 K-FELDSPAR I --?-IILLITE I
+ Si0 2 + (Ca, Na)
+ H20
6 I MAFIC MINERALS I + H 2 0
7
I VOLC. GLASSI + H 2 0
---;::. I CLAY MINERALS I + Si0 2 + (Mg, Fe)
CARBONATES
8
I CALCITE I
~ ZEOLITES,
SMECTITE
+ Mg ~ I DOLOMITE I
+ Si0 2 + (Na, K, Ca)
+ Ca
9
[CALCITE I
+ Fe, Mn, Mg --? Fe-CALCITE, Fe-DOL.,
ANKERITE, SIDERITE
+ Ca
REACTIONS WITH ORGANIC MATTER
10 ORGANIC MATTER + O 2
(trom bacterial reduction of Fe 2 0 3 , S04--' etc.)
--;.. CO 2
11
ORGANIC MATTER + THERMOCATALYSIS
~ CO 2 + CH 4
Remarks: The aid of organic acids in dissolving minerals in meteoric flow systems is
omitted. Reactions 2, 4 and 5 occur mainly at deep burial. Reaction 9 requires reducing conditions; the new minerals may form directly from solution without aprecursor
calcite. Pressure solution of carbonate and quartz as weil as redox processes affecting
sulfates and sulfides are not induded in the list.
Fig. 13.19. Major mineral reaetions in diagenesis,
simplified and not balaneed. For more speeifie information see text and referenees eited in text. Note that
the transformation of calcite to dolomite ean also
oeeur without the release ofCa++ ifbesides Mg++ also
suffieient C0 3 ++ is added