Chapter 1 - “Dolomitization” reconsidered
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C H A P T E R O N E
" DOLOMITIZATION" RECONSIDERED
WHAT DIAGENESIS ?
There has been no lack of speculation concerning the process of dolomite formation at low
temperatures. Early publications on the subject often contained the view, that dolomite would have
been formed through the action of "magnesia-rich volcanic vapors" on pre-existing limestones (e.g.,
Von Buch, 1822 A; Karsten, 1848). Such volcanic vapors are not often found in the sedimentary
environment. Therefore the magnesia-rich volcanic vapors of Von Buch(1822 A) and the
"dolomitisirende Gase" of Karsten(1848) have gradually been substituted by percolating magnesia-
rich solutions. Nowadays these percolating solutions seem to have many adherents, even though the
actual relations between such solutions and the low-temperature nucleation of dolomite have yet to
be demonstrated in reproducible laboratory experiments.
This is not the only objection against the suggested low-temperature conversion of pre-
existing limestone into dolomite (= "dolomitization"). The main argument against "dolomitization"
is, that the assumed chemical reaction will not take place at low temperature (around 298 K) and
atmospheric pressure. Calcium carbonate does not react with magnesium cations in solution at room
temperature: no conversion of limestone into dolomite is therefore possible under conditions typical
of the earth's surface. The reverse reaction does take place: a solution of calcium sulfate will change
dolomite powder into calcium carbonate plus a solution of magnesium sulfate (Von Morlot, 1847
A,B,C). No reaction can be measured to take place at room temperature between calcium carbonate
and magnesium sulfate or magnesium chloride in solution (Von Morlot, 1847 A,B,C; Liebe, 1855;
Van Tuyl, 1916 B). Despite these basic observations the concept of "dolomitization" still persists
today. It seems that the remark of Delanoüe(1854), that there is no such thing as "dolomitization"