K ar dating example
The Rb-Sr isotope system is another applicable geochronometer for illitic clays.
The basin is divided into eleven units, including six depressions (Manjiaer, Kuqa, Awati, Tangguzibasi, Southwestern and Southeastern) and five uplifts (Tadong, Tabei, Tazhong, Bachu and Tanan) (Fig. Multiple Phanerozoic tectonic events, related to global episodes, including Caledonian (Ordovician–Devonian), Hercynian (Carboniferous–Permian), Indosinian (Triassic), Yanshanian (Jurassic–Cretaceous) and Himalayan movements (Paleogene–Quaternary), have affected the basin (Fig. The 0.3–0.15 μm fraction was selected for the Rb-Sr isotopic study based on the following considerations: (1) detrital minerals are generally coarser in size, whereas they may be mixed in the 0.5–0.3 and 1–0.5 μm size fractions also confirmed the purity and authigenic origin of this size fraction.
The Sr ratio of clays is fractionated mainly by the addition of Rb during the illitization of mixed-layer illite/smectite (I/S), which is the dominant clay species in the Tarim Basin samples.
The subsample-scale Rb/Sr isotope values suggest that each subsample may contain I/S particles of slightly variable degrees of illitization.
(C) Honeycomb I/S and filamentous illites (I) in TZ67.
I/S particles contain high proportions of expandable smectite layers (IR = 30%); (D) Honeycomb ordered I/S particles in TZ67.