non terrigenous sediments and rocks
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Non-Terrigenous Sediments and Rocks. Carbonate-Chemical-Volcaniclastic Sediments and Rocks. No “Simple” Classification Scheme. Orthochemical Sediment: Evaporites. Stratified rock consisting of minerals precipitated from highly concentrated brines, typically hypersaline sea water

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non terrigenous sediments and rocks

Non-Terrigenous Sediments and Rocks

Carbonate-Chemical-Volcaniclastic

Sediments and Rocks

orthochemical sediment evaporites
Orthochemical Sediment:Evaporites
  • Stratified rock consisting of minerals precipitated from highly concentrated brines, typically hypersaline sea water
    • Anhydrite (CaSO4)
    • Gypsum (CaSO4 )*H2O
    • Halite (NaCl)
    • Others
evaporites
Evaporites
  • Indicative of unusual climatic or oceanographic conditions
    • Severe circulation restriction
    • Climatic aridity
  • Highly subject to secondary alteration/solution
    • Anhydrite<--->gypsum due to hydration/dehydration
    • Physical deformation: enterolithic structure
  • Occurrence
    • Bedded
    • Nodular
    • Chicken wire
siliceous sediments rocks
Siliceous Sediments/Rocks
  • Chert/diatomite (SiO2 );
    • Opaline tests
    • Chalcedony
    • microcrystalline quartz
siliceous sediments rocks6
Bedded chert (most)

Pelagic sediment consisting of siliceous zoo- and phytoplanktonic tests

Siliceous sediment experience apredictable transformation from amorphous opal to chalcedony and eventually to microcrystalline quartz due to time/temperature dependant chemical reaction

Siliceous Sediments/Rocks

C= lam chert, s= sandstone layers, f= fractures

siliceous sediments rocks7
Siliceous Sediments/Rocks
  • Nodular Chert; diagenetic origin (typical)
    • Silica derived from the solution of siliceous fossil material in predominantly carbonate rich successions
      • Sponge spicules and other siliceous bioclasts

N=chert nodules, b=bedded chert

organic rich sedimentary rock
Organic Rich Sedimentary Rock
  • Organic compound-rich rocks
    • Coal
      • Humic coal
        • vascular {land} plant derived organic compounds altered by elevated temperature and burial pressure
      • Sapropelic coal
        • Formed from non-vascular (algal) plant material
organic rich sedimentary rock9
Organic Rich Sedimentary Rock
  • Oil (black) Shale
    • Primary, organic carbon (OC)-rich shale (>2% to > 10% OC)
    • Formed in low energy environments through suspension and deposition in stagnant (anaerobic) conditions
      • Most common source of long chain, liquid and gaseous hydrocarbons that can migrate into porous reservoir rocks and from economic accumulations of petroleum

Spontaneous combustion of

Kimmeridge oil-shale, Dorset, UK.,

probable source for most North Sea oil

importance of volcaniclastics
Importance of Volcaniclastics
  • Recognition of contemporaneous volcanism
    • Pyroclastic rocks and volcaniclastics with admixtures of proclasts
  • Voluminous strata at plate boundaries and hot spots
classification of volcaniclastic rocks
Volcanic particulate material

Any fragmentation mechanism

Any transport process

Any environment

Pyroclastic

Particles broken by volcanism

Epiclastic (epiclasts)

Any fragment of volcanic (composition) origin

Classification of Volcaniclastic Rocks
classification of volcaniclastic rocks12
Pyroclastic rock or sediment

>75% material fragmented by volcanic eruptions

Tephra: unconsolidated pyroclastic deposit

Hydroclastic rocks or sediment

Water interaction fragmentation

Classification of Volcaniclastic Rocks

Pyroclastic Ejecta

classification of pyroclastic rocks
Classification of Pyroclastic Rocks
  • Basic classification otbo (on the basis of) particle size
    • Blocks (solid) and bombs (molten) (>64mm)
      • Volcanic breccia deposits
    • Lapilli (2-64mm)
      • Lapillistone
    • Ash (<2mm)
      • Tuff
  • Additional Classification otbo composition
    • Crystals
    • Lithic
    • Vitric fragments
composition of tuffs
Composition of Tuffs
  • Crystals (intratelluric)
    • Euhedral +/- broken
    • Compositional zoning
  • Vitric (glassey) fragments
    • Bubble wall shards
composition of tuffs15
Composition of Tuffs
  • Vitric (glassy) fragments
    • Bubble wall shards
    • Hydroclastic shards
  • Lithic fragments
    • Volcanic rock fragments (cognate?)
fragmentation processes
Fragmentation Processes
  • Explosive (gas expansion) comminution (fragmentation): mainly intermediate to silicic (high silica) magmas.
    • Ash fall; Laterally extensive air fall; Typically silicic and vitric rich.
      • Mantles topography.
      • Consists of glass (bubble-wall) shards.
volcanic fragmentation processes and products
Volcanic Fragmentation Processes and Products
  • Continental silicic (high silica) magmas; Calderas and pyroclastic sheet deposits
    • Ash flow {nuee ardante or ignimbrite, as in “great flaming ignimbrites”.
      • Follow topographic lows (high density fluid).
      • Create gigantic pyroclastic sheet deposits
      • Can be hot enough after deposition to weld, annealed vitric fragments welded tuff

Kaguyak volcano, Alaska

volcanic fragmentation processes and products18
Volcanic Fragmentation Processes and Products
  • Hydroclastics; Water interaction fragmentation (typically basaltic lavas)
    • Great volumes of hydroclastics on the sea floor and in the edifice (sticky-up topographic/bathymetric feature) of submarine volcanoes
    • Highly subject to alteration –> clay minerals, microcrystalline silica, and zeolite
significance of volcaniclastic rocks
Subject to extensive diagenetic alteration during burial

Typically occur in high heat flow geological settings

Typically poor fluid reservoir rocks

Significance of Volcaniclastic Rocks
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