Open AccessMineralogical and geochemical characteristics of mudstones in the Jersovec chert deposit
Author(s) -
Simona Jarc,
Simon Jerina,
Miloš Miler,
Nina Zupančič
Publication year - 2017
Publication title -
geologija
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.187
H-Index - 7
eISSN - 1854-620X
pISSN - 0016-7789
DOI - 10.5474/geologija.2017.016
Subject(s) - geology , zircon , ilmenite , mineralogy , monazite , illite , chlorite , mineral , geochemistry , muscovite , clay minerals , quartz , rutile , sedimentary rock , terrigenous sediment , apatite , chemistry , paleontology , organic chemistry
Jersovec chert deposit is a part of the transitional zone between the internal and the external Dinarides.\udTethyan cherts are often interlaid with fie-grained material, as is also the case in Jersovec, where chert beds\udinterchange with several thin, up to 10 cm thick layers of fie-grained sedimentary rocks. The source of this\udmaterial is often questionable and interpreted to be terrigenous, volcanogenic or even combination of both. In\udorder to determine origin and depositional environment of fie-grained material, detailed mineralogical and\udgeochemical analyses were performed.\udFine-grained sedimentary rocks were characterised by X-ray diffraction (XRD), scanning electron microscopy/\udenergy dispersive X-ray spectroscopy (SEM/EDS) and inductively coupled plasma emission spectroscopy (ICPES) and mass spectroscopy (ICP-MS). All samples are mineralogically very similar but differ in mineral ratios.\udThey contain quartz and clay minerals, predominantly illite/muscovite and chlorite group minerals. SEM/EDS\udanalysis additionally revealed zircon, monazite, Ti-oxide (probably rutile) and iron oxides/hydroxides in all\udsamples, whereas chromite, ilmenite, xenotime, apatite and baryte were found only in some of them. The average\udsizes of accessory minerals range from 3–20 μm. Two samples differ from the others by their brown colour and\udhigher Fe2O3 and lower SiO2 contents. All other samples are green. Chemical analysis showed that they consist\udmostly of SiO2 (46.3–69.3 %), Al2O3 (15–24.1 %) and minor contents of K2O (2.8–3.4 %), Fe2O3 (2.1–8.4 %), MgO\ud(1.6–2.3 %), TiO2 (0.5–0.7 %), CaO (0.3–1.4 %), Na2O (0.1 %) and P2O5 (up to 0.5 %).\udPosition of all samples in the Zr/TiO2 vs. (V+Ni+Cr)/Al2O3 diagram points to terrigenous origin and\udsedimentation on the continental margin. According to the chemical weathering indices (CIA and CIW) material\udhas been subjected to the intense and long weathering, supported also by the index of compositional variability\ud(ICV), which corresponds to the compositionally mature material, and by rounded zircon and ilmenite grains