13 Mechanical and Chemical Diagenesis
13.1 General Aspects ofMechanical and
647
Chemical Diagenesis
13.1.1 Introduction, Definitions
13.1.2 Various States of Sediment Consolidation
13.1.3 Mechanical and Chemical Compaction
(Overview)
13.2 Compaction, Compaction Flow, and
Other Flow Mechanisms
653
13.2.1 Analytical Equations to Describe Compaction
13.2.2 Compaction Ratio and
Differential Compaction
13.2.3 Compaction Flow
Model Calculations
Compaction Flow as Function of
the Sedimentation Rate
Velocity of Ascending Pore Water
13.2.4 Pore Water Pressure, Overpressure
13.2.5 Refraction ofPore Water Flow
13.2.6 Other Subsurface Flow Regimes
13.2.7 Significance ofthe Various Flow Regimes
13.2.8 Evolution ofPore Water Flow in
Various Depositional Systems
13.2.9 Summary (Compaction and
Subsurface Flow Regimes)
13.3 General Processes in Chemical Diagenesis
668
13.3.1 Introduction
13.3.2 Solute Transport by Subsurface Flow Systems
General Aspects
Meteoric Water Circulation
Compaction Flow
Redistribution of Solutes by
Convective Fluid flow
Combination ofVarious Processes of
Solute Transport
13.3.3 Pressure Solution
13.3.4 Solute Transport by Diffusion
13.3.5 Hydrodynarnic Dispersion
13.3.6 Formation Waters
13.3.7 Mineral Reactions and
Major Diagenetic Regimes
Mineral Reactions
Major Diagenetic Regimes (Overview)
13.3.8 Porosity and Permeability ofSandstones and
Carbonate Rocks
13.4 Early Diagenesis ofMajor Sediment Types
685
13.4.1 Marine Muds under Oxic and Anoxic
Conditions
13.4.2 Biogenic Carbonates (Muds and Grainstones)
13.4.3 Biosiliceous Sediments
13.4.4 Early Diagenesis of Sands
13.5 Late, Deep-Burial Diagenesis
689
13.5.1 Trend to a Final, Inactive Stage?
13.5.2 Reactivation ofLate-Stage Diagenesis
13.5.3 Large-Scale Fluid System and
Late Dolomitization
13.5.4 Geohistory and Diagenesis (Case Studies)
13.5.5 Cement Sources and Cement Mineral
Sequences
13.6 The Transition from Diagenesis to Metamorphism
697
13.7 Thermal History ofBasin Fills
13.7.1 Subsiding Basins Affected by Conductive
HeatFlow
697
13.7.2 Thermal Effects ofSubsidence Followed by
Uplift
13.7.3 Thermal Effects ofMeteoric Water Circulation
13.8 Special Methods and Processes in Diagenesis
700
13.8.1 Age, Temperature, and Degree of
Diagenetic Reactions
13.8.2 Diagenetically Controlled Ore Deposits
13.8.3 Pore Water Expulsion and Hydrothermal
Systems at the Sea Floor
13.9 Summary (Chernical Diagenesis)
13.1 General Aspects of Mechanical
and Chemical Diagenesis
3.1.1 Introduction, Definitions
705
Freshly deposited sediments are commonly unconsolidated, have a relatively low bulk density and high
permeability and, if accumulated under water, a high
water content. However, with increasing burial depth
under younger sediments, and occasionally shortly
after deposition, the sediments become denser and
more solid or lithified. All the processes involved in
such a change of sediment state are summarized under the term diagenesis. It comprises both mechanical and chemical-mineralogical processes.
Some authors, particularly those dealing with the transformation of organic matter into hydrocarbons and coal
(Sects. 14.2 and 14.4), distinguish a zone of catagenesis or
an anchimetamorph zone (anchizone) between diagenesis
and metamorphism. At this depth range, most sediments
have become lithified, shales and claystones are transformed into slates, smectite and mixed-Iayer clay minerals
13.1 General Aspects ofMechanical and
647
Chemical Diagenesis
13.1.1 Introduction, Definitions
13.1.2 Various States of Sediment Consolidation
13.1.3 Mechanical and Chemical Compaction
(Overview)
13.2 Compaction, Compaction Flow, and
Other Flow Mechanisms
653
13.2.1 Analytical Equations to Describe Compaction
13.2.2 Compaction Ratio and
Differential Compaction
13.2.3 Compaction Flow
Model Calculations
Compaction Flow as Function of
the Sedimentation Rate
Velocity of Ascending Pore Water
13.2.4 Pore Water Pressure, Overpressure
13.2.5 Refraction ofPore Water Flow
13.2.6 Other Subsurface Flow Regimes
13.2.7 Significance ofthe Various Flow Regimes
13.2.8 Evolution ofPore Water Flow in
Various Depositional Systems
13.2.9 Summary (Compaction and
Subsurface Flow Regimes)
13.3 General Processes in Chemical Diagenesis
668
13.3.1 Introduction
13.3.2 Solute Transport by Subsurface Flow Systems
General Aspects
Meteoric Water Circulation
Compaction Flow
Redistribution of Solutes by
Convective Fluid flow
Combination ofVarious Processes of
Solute Transport
13.3.3 Pressure Solution
13.3.4 Solute Transport by Diffusion
13.3.5 Hydrodynarnic Dispersion
13.3.6 Formation Waters
13.3.7 Mineral Reactions and
Major Diagenetic Regimes
Mineral Reactions
Major Diagenetic Regimes (Overview)
13.3.8 Porosity and Permeability ofSandstones and
Carbonate Rocks
13.4 Early Diagenesis ofMajor Sediment Types
685
13.4.1 Marine Muds under Oxic and Anoxic
Conditions
13.4.2 Biogenic Carbonates (Muds and Grainstones)
13.4.3 Biosiliceous Sediments
13.4.4 Early Diagenesis of Sands
13.5 Late, Deep-Burial Diagenesis
689
13.5.1 Trend to a Final, Inactive Stage?
13.5.2 Reactivation ofLate-Stage Diagenesis
13.5.3 Large-Scale Fluid System and
Late Dolomitization
13.5.4 Geohistory and Diagenesis (Case Studies)
13.5.5 Cement Sources and Cement Mineral
Sequences
13.6 The Transition from Diagenesis to Metamorphism
697
13.7 Thermal History ofBasin Fills
13.7.1 Subsiding Basins Affected by Conductive
HeatFlow
697
13.7.2 Thermal Effects ofSubsidence Followed by
Uplift
13.7.3 Thermal Effects ofMeteoric Water Circulation
13.8 Special Methods and Processes in Diagenesis
700
13.8.1 Age, Temperature, and Degree of
Diagenetic Reactions
13.8.2 Diagenetically Controlled Ore Deposits
13.8.3 Pore Water Expulsion and Hydrothermal
Systems at the Sea Floor
13.9 Summary (Chernical Diagenesis)
13.1 General Aspects of Mechanical
and Chemical Diagenesis
3.1.1 Introduction, Definitions
705
Freshly deposited sediments are commonly unconsolidated, have a relatively low bulk density and high
permeability and, if accumulated under water, a high
water content. However, with increasing burial depth
under younger sediments, and occasionally shortly
after deposition, the sediments become denser and
more solid or lithified. All the processes involved in
such a change of sediment state are summarized under the term diagenesis. It comprises both mechanical and chemical-mineralogical processes.
Some authors, particularly those dealing with the transformation of organic matter into hydrocarbons and coal
(Sects. 14.2 and 14.4), distinguish a zone of catagenesis or
an anchimetamorph zone (anchizone) between diagenesis
and metamorphism. At this depth range, most sediments
have become lithified, shales and claystones are transformed into slates, smectite and mixed-Iayer clay minerals