Chemical and mineralogical composition of Triassic mudstonesform the Brembana Valley (Lombardian Basin) have been determinedto characterize their sedimentary history and the relationships betweensource area and depositional basin. Mudstones include abundantphyllosilicates, while quartz, carbonates (calcite and dolomite) andfeldspars (plagioclase and K-feldspar) are minor. Clay fractionincludes illite, kaolinite and chlorite with minor amounts of I/S mixedlayer.The order of interstratified I/S suggests a temperature of 160-180°C, typical of the deep diagenesis/anchizone. The CIA value is onaverage 66, suggesting a low-moderate alteration of the source area.The 15Al2O3-Zr-300-TiO2 diagram show a trend of mixing in thedirection of the Zr apex typical of sediment recycling. The ICV valuesfor the studied samples are <1 (on average 0.84) suggesting thatmudstones are compositionally mature; these values are probablyrelated to recycling processes as shown by the Al-Zr-Ti plot. Thestudied samples have Al2O3/TiO2 values ranging from 17 to 34; thesevalues suggest that the mudstones were formed in environmentscharacterized by humid and semi-arid climates. The Al2O3 vs. TiO2and Cr/V vs. Y/Ni plots indicates that the source areas are mainlycomposed of felsic rocks with minor/negligible mafic-ultramaficsupply.
Geochemistry and mineralogy of the Triassic mudstones from the Brembana Valley (Lombardian Basin, northern Italy)
Perri F;CRITELLI, Salvatore;
2015-01-01
Abstract
Chemical and mineralogical composition of Triassic mudstonesform the Brembana Valley (Lombardian Basin) have been determinedto characterize their sedimentary history and the relationships betweensource area and depositional basin. Mudstones include abundantphyllosilicates, while quartz, carbonates (calcite and dolomite) andfeldspars (plagioclase and K-feldspar) are minor. Clay fractionincludes illite, kaolinite and chlorite with minor amounts of I/S mixedlayer.The order of interstratified I/S suggests a temperature of 160-180°C, typical of the deep diagenesis/anchizone. The CIA value is onaverage 66, suggesting a low-moderate alteration of the source area.The 15Al2O3-Zr-300-TiO2 diagram show a trend of mixing in thedirection of the Zr apex typical of sediment recycling. The ICV valuesfor the studied samples are <1 (on average 0.84) suggesting thatmudstones are compositionally mature; these values are probablyrelated to recycling processes as shown by the Al-Zr-Ti plot. Thestudied samples have Al2O3/TiO2 values ranging from 17 to 34; thesevalues suggest that the mudstones were formed in environmentscharacterized by humid and semi-arid climates. The Al2O3 vs. TiO2and Cr/V vs. Y/Ni plots indicates that the source areas are mainlycomposed of felsic rocks with minor/negligible mafic-ultramaficsupply.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
