(E) Sediment geochemistry chemical composition of common arenites Pettijohn et al. 1987 p.59 classification based on geochemistry Herron 1988 Pettijohn 1963, 1987
Example: Swiss Molasse Basin 1. CE 1% calclithite 33% 9% NCI-rich sandstone NCI-bearing sandsto dstone sandstone s.str. NCI glauconitic greensand oolithic ironstone reworked phosphorite gypsarenite CI rich NCI-ric hybrid arenite NCI-bearing N hybrid arenite hybrid arenite CI calcarenite 2. subarkose lithic subarkose arko kose 25% 5% lithic arkose Q quartzarenite feldspathic litharenite sublitharenite litharenite NCE quartzarenite, arkose, litharenite F Lincl. CE /K O) 2 2 3 / lo og(fe O 1-1 Fe-shale shale litharenite wacke arkose Fe-sandstone sublitharenite subarkose 1 2 log(sio 2/Al2O 3) renite quartz ar classification based on geochemistry classification based on petrography Pettijohn et al. 1987 p.59
Rollinson 1993 Tectonic Setting Discrimination diagrams (1) Major elements: Rollinson 1993 p.28
Rollinson 1993 p.27 discrimination of tectonic setting by major elements does it work properly? Armstron-Altrin & Verma 25, Sed Geol 177
success rate Armstron-Altrin & Verma 25 be very careful with such discrimination diagrams!!! the problem of grain-size D G-m O-m O-f O-g G-g G-f A C B A increasing grain size B C D Bhatia 1983, Bhatia & Crook 1986, Roser & Korsch 1988 greywackes from type-locality Oberharzer Grauwacke
Bivariate Ca / Mg / LOI-plots of Swiss Molasse sandstones (litharenites) 6 6 5 5 4 4 CaO 3 CaO 3 2 2 1 1 2 3 4 5 6 7 8 2 SiO 2 1 2 3 4 2 LOI 16 16 MgO 12 8 MgO 12 8 4 4 1 2 3 4 5 6 CaO 1 2 3 4 LOI Ma G S % 6 3 13 15 17 19 21 23 25 27 29 31 WSW ENE 8 7 6 5 4 3 2 1
framework composition vs. wr-geochemistry von Eynatten 23 (2) Trace elements: Rollinson 1993 p.28
detection of various processes such as recycling, sorting, etc. Th/Sc monitors the compositional variation of the source area, and Z/S Zr/Sc monitors zircon enrichment due to sedimentary (sorting and) recycling 1 Th / Sc 1.1 Sediment Recycling Active Margin Turbidites.1 Trailing Edge Turbidites.1 Zr / Sc Andean Foreland Loess.1 1 1 1 1 McLennan 1993, GSA Spec Pap 284 Cr-spinel chemistry cling recy TiO 2 [Gew.-%] 2. 1.5 IPB 1..5 MORB IAB.5.1.15 Fe III /(Cr+Al+Fe) group I TiO 2 [Gew.-%] 2. group II group III 1.5 1..5 MORB IPB IAB.5.1.15 % L u (serpentinite clasts) Fe III /(Cr+Al+Fe) von Eynatten 23, Sedimentology 5
Ma 13 15 17 19 21 23 25 27 SEDIMENTE WSW > > > edimente e dimente e (Ultra-)basite > 75% 5-75% 25-5% 1-25% Flysch Metasedimente Granitoide? recycling? ~ 2 Ma Metas Sedimente Granitoide ~ 25 Ma? recycling? 29 SEDIMENTE WSW 31 (Ultra-)basite 8 7 Sedimente 6 5 4? Se (Ultra-)basite ~ 21 Ma Sedimente Granitoide ENE (Ultra-) basite SEDIMENTE 3 2 1 toide Grani ENE von Eynatten 23 Contribution of mafic to ultramafic (ophiolitic) source rocks ( Mixing! ) McLennan 1993
Rare earth patterns of sediments from different sources McLennan 1993 Alteration (weathering, diagenesis,...) Chemical Index of Alteration: Al 2 O 3 CIA = 1 Al2 O 3 + CaO* + Na 2 O + K 2 O (with CaO* = CaO from silicate phases) increasing alteration Nesbitt & Young 1989
Leeder 1999 Nesbitt & Young 1989
chemical weathering of granitoid rocks Toorongo granodiorite (Nesbitt et al. 198, GCA 44) A 1 Ka C I A Chemical Index of Alteration: Al 2 O 3 +CaO*+Na 2 O+K 2 O 1 Al 2 O 3 5 Pl + Kf CN K chemical weathering of granitoid rocks Toorongo granodiorite p(a) s k = (k p w1 ) g p w1 = (.49,.13,.38) 99.5% g + von Eynatten et al. 23 p(cn) p(k)
chemical weathering of granitoid rocks Toorongo granodiorite 1.8 Al O 2 3 normalized to Al 2 O 3 = 1.6 2 3.4.2 CaO* Na O KO 2 2 k 1 2 3 4 5 6 7 8 9 1 von Eynatten et al. 22, Math. Geol. 34 chemical weathering at global scales suspended sediment load of the world s major rivers (McLennan 1993, J. Geol. 11) s = cc (k p w2 ) p w2 = (.51,.13,.36) 97.1% p w1 = (.49,.13,.38) river k St. Lawrence.13 p(a) Danube.25 Niger Ganges.75 Indus.78 Orinoco 1.1 Mekong 1.87 Congo Congo 2.15 Niger 3.49 99.5% Orinoco Indus Mekong Ganges p(cn) cc g Danube St. Lawrence Mackenzie p(k) von Eynatten et al. 23, Math. Geol. 35
Observed trends often due not correlate with predicted trends She et al. 26, Chem Geol. X 1 superposition of processes 1 2? von Eynatten 24, Sed Geol a X 2 X 3 Trace elements such as Rb, Ba, Sr, U, Th, Zr, etc. may provide valuable additional information on weathering processes McLennan 1993