:)

I think, this is obvious reaction (boiling, changing of color) rather than "silent", running without such visible signs.

Just kidding...

Serious now :

a precipitate
....

The Sr isotope ratio is a passive tracer of the bulk solid reactivity. The individual
mineral dissolution rates are assumed to be independent of the isotopic ratios, and
governed by departures from equilibrium involving the major chemical constituents of
the rock. The driving potential for metamorphic reactions is provided by some
combination of the overall chemical affinity (see Aagaard and Helgeson, 1982; Lasaga,
1998) and the strain energy (Stunitz, 1998). The overall chemical affinity is a measure
of the sum, over all independent chemical reactions, of the free energy departure from
equilibrium. The assumption that the isotopic exchange is passive stems from the fact
that the contribution of isotopic exchange reactions to the overall chemical affinity is
negligible (see Cole and Chakraborty, 2001).
A note about “net” versus “gross” reaction rates.—Transition state theory dictates that
metamorphic reactions proceed towards equilibrium at a rate, Rnet, which is the
difference between a gross forward reaction rate (Rf) and a gross backward reaction
rate (Rb). Gross forward (and backward) dissolution and precipitation are driven by
the free energy difference between reactants (or products) and the activated complex
(Lasaga, 1998). At dynamic equilibrium, Rf  Rb and there is no net reaction progress
in the system with time (that is, Rnet  0). Rnet and Rf are related to each other by
transition state theory according to the relation (Lasaga, 1998):
Rnet
Rf

1  eGr/
T (5)
In general, the net reaction rate is smaller than the gross forward rate. The passive
isotopic exchange responds to the gross reaction rates. Thus, the isotopic method used
here essentially measures the gross forward rate (that is, R  Rf) as immediate
dissolution of product minerals has a reduced effect on the isotopic composition of the
ITM. Therefore, if the departure from equilibrium (Gr) is small relative to
T, then
Rnet may be much smaller than Rf. However, for Gr 
T, Rf and Rnet will differ only
by a factor of about 1.6.

Either the forward reaction (e.g. dissolution) or the backward reaction (e.g. precipitation) considered separately. The net reaction is the difference between the two gross reactions. Please see link p. 451.