Geothermometry - inorganic bench-marks

Transcription

1 Beckenanalyse 2: Analytic tools for basin analysis: thermometers and geochronometers [M.Geo.136b] Part 2b: How to measure the paleo-tempearture? (by inorganic methods) University of Göttingen István Dunkl Sedimentology, University of Göttingen 1) Heat flow in basins 2) Geothermometry in basins by: vitrinite-, bitumen-, graptolite reflectance, Raman spectroscopy, conodont alteration index, spore colour, fluorescence, Rock-Eval, molecular ratios, clay mineralogy... 3) Fission track thermochronology (nuclear physics, statistics) 4) Dating volcanic events (= formation ages) and basement exhumation (= cooling ages) 5) Complex thermal histories of basins & thermal modelling 6) Detrital geochronology (provenance by single-grain ages) 7) (U-Th)/He thermochronology 8) K/Ar, Ar/Ar, Luminescence, ESR and cosmogenic dating of sediments 9) U-Pb and U-series dating of sediments Geothermometry - inorganic bench-marks Zeolite mineralogy Two-carbonate thermometry Illite smectitite "thermometry" Illite "crystallinity" (IC, Kübler index) b0-parameter Chlorite "crystallinity" Fluid inclusion

2 Inorganic mineral -coexistence geothermometry [Kristmannsdottir, 1982] Inorganic thermometry - two-carbonate method X Fe in dolomite C 350 C 400 C 450 C 500 C 550 C X Mg in calcite [Powell et al., 1984]

3 Compilation of inorganic thermometry methods Thermometry Illite / smectite thermometry

4 XRD patterns of glycol-saturated oriented preparations of <0.2 mm fractions, illustrating the full range of expandabilities of illite-smectite (%S) encountered in the investigated tuffite rocks [S'rodon' et al., 2006] Illite / smectite ratio vs. K content [S'rodon' et al., 2006]

5 Smectite content of different basins [S'rodon' et al., 2006] Thermometry Illite smectite thermometry [Schegg, 1993]

6 Thermometry Definition of illite crystallinity indices [Swierczewska, 2005] Thermometry Definition of illite crystallinity indices

7 Thermometry [Árkai et al., 2003] Is it true? [Underwood et al., 1993]

8 Kübler index --- Applied at mapping and along profiles [Warr & Robinson, 1990] Thermometry - illite crystallinity vs. vitrinite reflectance [Bonazzi et al., 1987]

9 Thermometry - illite crystallinity vs. vitrinite reflectance Thermometry --- sensitivity of illite crystallinity to deformation

10 Illite b0 lattice parameter - a pressure indicator [Underwood et al., 1993] Thermobarometry using b0 --- Estimation of approximate metamorphic peak pressure [Paudel & Arita, 2005]

11 'Chlorite crystallinity' = Árkai Index (ÁI) [Árkai et al., 2003] Kübler Index vs. Árkai Index --- (illite vs. chlorite) [Potel et al., 2006]

12 Thermometry Determination of pt conditions by fluid inclusions and vitrinite reflectance [Sakaguchi, 1999] Thermometry Determination of pt conditions by fluid inclusions and vitrinite reflectance [Sakaguchi, 1999]

13 Metapelitic zones [Merrimann & Peacor, 1999] Synopsis of major geothermometers Organic and inorganic geothermometers Vitrinite reflectance (Rm %) Rock-Eval pyrolysis Fluorescence of org. m. Molecular maturity parameters (hopan & MPI-1) Raman spectroscopy of carbonaceous mat. Calcite-Dolomite Metapelite thermobaro. Metabasite thermobaro. Thermochronometers Semiquantitative thermometers Thermal alteration index (TAI) Conodont alteration index (CAI) 'Low temp.' (apatite, zircon FT,He) 'Medium temp.' (Bt, Ms K/Ar, Ar/Ar, Rb/Sr) Zones in the major classifications Illite Kübler-index (KI) zone Mineral facies Metamorphic grade Temperature [ C] source: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10, 11] [12] [12] [13] ~4.4 1 yellow 1 yellow 2 orange 2 light brown 3 brown 3 brown 4 dark 4 black brown 5 black AHe AFT ZFT ZHe [14] [15] [15] [15] diagenetic zone (KI > 0.42) VR: anchizone (KI: ) VR: 4-5 epizone (KI < 0.25) zeolite f. prehnitpumpellyite f. greenschist f. diagenesis very low-grade low-grade 500 amphibolite f.

14 Questions - Organic geothermometers - optical methods? - Organic geothermometers - non-optical methods? - Inorganic geothermometers? (materials used, sensitivity, advantages, drawbacks)