Abstract
Residual clays that developed on Permian and Carboniferous glass-rich silicic volcanic rocks (pitchstones, ignimbrites) at the Seilitz and Kemmlitz kaolin deposits. Saxony, Eastern Germany, contain locally abundant lath-shaped illite-rich illite-smectite mixed-layer minerals (I-S). Analyses by XRD and TEM-AES reveal a large illite percentage (>∼90%) and R3 ordering in I-S from Seilitz (>∼90%) and smaller illite percentage (∼70%) and R1 ordering in I-S from Kemmlitz. The clays never suffered a deep burial and there is no geological, petrographic or fluid inclusion evidence for acolian input or hydrothermal origin of I-S at either deposit. The I-S formed exclusively at the expense of volcanic glass and not from K-feldspar. Residual quartz phenocrysts in the clays still preserve primary glassy silicate melt inclusions and lack secondary aqueous fluid inclusion trails. The δD and δ18O values of kaolinite and I-S are suggestive of low formation temperatures (<40°C). Rb-Sr and K-Ar dating of I-S-bearing clay separates yield Lower Cretaceous ages at Seilitz and indicates the presence of excess or inherited 40Ar in illite-rich I-S. In contrast, Triassic to Jurassic Rb-Sr ages are obtained for I-S from the Kemmlitz kaolin deposit.
Original language | English |
---|---|
Pages (from-to) | 95-112 |
Number of pages | 18 |
Journal | Clay Minerals |
Volume | 38 |
Issue number | 1 |
DOIs | |
State | Published - Mar 2003 |
Keywords
- Hydrogen isotope
- Illite-smectite
- K-Ar
- Kaolin deposits
- Kaolinite
- Kemmlitz
- Mesozoic
- Oxygen isotopes
- Rb-Sr
- Saxony
- Seilitz
- TEM