Development and Evolution of the Size of Polygonal Fracture Systems during Fluid-Solid Separation in Clay-Rich Deposits  

作　　者：Teodolina Lopez Raphael Antoine JoséDarrozes Michel Rabinowicz David Baratoux 

机构地区：[1]CESBIO,Universite de Toulouse,CNES/CNRS/IRD/UPS,loulouse,Prance [2]International Space Science Institute(ISSI),Bern,Switzerland [3]CEREMA,Laboratoire Regional de Rouen,Groupe Sciences de la Terre,CS 90245,F-76121 Le Grand Quevilly,France [4]GET,Universite de Toulouse,UPS/CNRS/IRD/CNES,Toulouse,France [5]Institut Fondamental d'Afrique Noire(IFAN),Cheikh Anta Dio,Dakar,Senegal

出　　处：《Journal of Earth Science》2018年第6期1319-1334,共16页地球科学学刊（英文版）

基　　金：support by the French Space Agency CNES,PNP(Programme National de Planétologie);TOSCA(Terre,Océan,Surfaces Continentales,Atmosphère)

摘　　要：In continental and oceanic conditions, clay-rich deposits are characterised by the development of polygonal fracture systems（PFS）. PFS can increase the vertical permeability of clay-rich deposits（mean permeability ≤10-16 m2） and are pathways for fluids. On continents, the width of PFS ranges from centimeters to hundreds of meters, while in oceanic contexts they are up to a few kilometers large. These structures are linked to water-solid separation during deposition, consolidation and complete fluid squeeze of the clay horizon. During the last few decades, modeling of melt migration in partially molten plastic rocks led to rigorous quantifications of two-phase flows with a particular emphasis on 2D and 3D induced flow structures. The numerical modeling shows that the melt migrates on distances almost equal to a few times the compaction length L that depends on permeability and viscosity. Consequently, polygonal structures in partially molten plastic rocks are resulted from the melt-rock separation and their sizes are proportional to L. Applying these results to fluid-solid separation in clay-rich horizons, we show that（1） centimetric to kilometric PFS are resulted from the dramatic increase of L during compaction and（2）, this process involves agglomerates with 100 μm to 1 mm size.In continental and oceanic conditions, clay-rich deposits are characterised by the development of polygonal fracture systems（PFS）. PFS can increase the vertical permeability of clay-rich deposits（mean permeability ≤10-16 m2） and are pathways for fluids. On continents, the width of PFS ranges from centimeters to hundreds of meters, while in oceanic contexts they are up to a few kilometers large. These structures are linked to water-solid separation during deposition, consolidation and complete fluid squeeze of the clay horizon. During the last few decades, modeling of melt migration in partially molten plastic rocks led to rigorous quantifications of two-phase flows with a particular emphasis on 2D and 3D induced flow structures. The numerical modeling shows that the melt migrates on distances almost equal to a few times the compaction length L that depends on permeability and viscosity. Consequently, polygonal structures in partially molten plastic rocks are resulted from the melt-rock separation and their sizes are proportional to L. Applying these results to fluid-solid separation in clay-rich horizons, we show that（1） centimetric to kilometric PFS are resulted from the dramatic increase of L during compaction and（2）, this process involves agglomerates with 100 μm to 1 mm size.

关 键 词：COMPACTION clay deposit AGGLOMERATES polygonal fractures desiccation cracks 

分 类 号：P619.231[天文地球—矿床学]