13.3 Chemical Diagenesis
a AQUEOUS DIFFUSION
I ON
WATER
A B
SEDIMENT
~ OPEN ·
{ , : r
,
SYSTEM
7:*-:
T
1-"
I
, . I f r . ., I I
, ~I
-.,.
I
CLOSED
I
I
100
SYSTEM
I
TO
gSO'
I
I
HEMICAL I
I
m
DIAG.)
KI
I
/
I ~ t
I
.1.
DECREASING
SEDIMENT
MULTI·
DIFFUSION
DIRECTIONAL
COEFFICIENT
TRANSPORT
C MIXED SOLUTE TRANSPORT
METEORIC FLOW
+DIFFUSION
EMERGED
:!:OPEN
SYSTEM t
(ALLO·
~
.
T
I I \
I
'''~.U. _ ..,/1.,,/1.
->
CHEM.
DIAG.)
~- ____ -
500
:!:CLOSED f
SYSTEMS l
PREDOMINANTLY
DIFFUSION, SOME
COMPACTION FLOW
.
TO
DIFFUSION
b COMPACTION FLOW (ADVECTION)
ION A+ B
WATER'
l"' t
.,.
I
I ENHANCED
:!:CLOSED
SYSTEM
/
' :
~FLOW'
r, • __
.': .' . LEACHING OR
I I
~ CEMENTATION
I I t
I
I I
I
I
ASYMMETRIC
~
CEMENTATION
I...
? t I OR LEACHING
I
I
DECREASE
IN FLOW
VELOCITY
'7777r77777~ BASEMENT
:!:UNIDIRECTIONAL
TRANSPORT
f
EXCHANGE OF
SSOLVED SPECIES
FUSION)
SOLUTION AND
RECRYSTAL·
LlZATION
PRIMARY
UNSTÄBLE
eAATiCLES
tE. G.,
ARAGONITE}
NEW, STABLE
MINERAL
INTRAGRANULAR MICROPORE,
AQUEOUS SOLUTION, DIFFUSION ONLY
DISSOLUTION OF CARBONATE,
CUMULATION OF QUARTZ AND
SUBSURFACE
CONVECTIVE FLUID FLOW
SHALE
HYDROCARBONS
--7--------ISOTHERMS "DISSOLUTION
OF QUARTZ,
ACCUMULATION
OF CARBONATES
--~-----".
SAND/SANDSTONE
SHALE
671
Fig. 13.16. a-c Various mechanisms of solute transport in sediments reflecting more or less "closed" or
"open" chernical systems. d Solution-recrystallization
via thin film of pore fluid in rnicropore of closed
(isochemical) system. e Same as d but in open
(allochemical) system. f Convective pore fluid flow
in folded sand sheet intercalated with shales. (After
Wood and Hewett 1984). Quartz is dissolved in the
hotter synclinal trough and precipitated in the cooler
anticline, while carbonate behaves vice versa