Ages of Silurian radiolarians from the Kurosegawa terrane, southwest Japan constrained by U/Pb SHRIMP data

Upper Silurian and Devonian pelagic deep-water radiolarian chert from the Khangai–Khentei belt of Central Mongolia: Evidence for Middle Paleozoic subduction–accretion activity in the Central Asian Orogenic Belt

“…Assemblage 2 was collected from Uubulan, 350 m west of section 20040813B (sample 2004/5) and section 20050819G (sample 081929). Aitchison et al (1996) carried out SHRIMP dating of zircons extracted from tuffaceous rocks containing D. solidum (sample Kh-22 of Wakamatsu et al, 1990) from Konomori in the Kurosegawa terrane, Southwest Japan, yielding a U/Pb age of 408.9 ± 7.6 Ma, which was thought to be latest Silurian based on the geological time scale in use at that time (Odin, 1994). Based on a re-evaluation using the latest geologic time scale (see Gradstein et al, 2004), this U/Pb age is equivalent to the late Pragian (middle Early Devonian), with error bars extending from the latest Pridolian into the Emsian (late Early Devonian).…”

Mid-Paleozoic arc granitoids in SW Japan with Neoproterozoic xenocrysts from South China: New zircon U–Pb ages by LA-ICP-MS

“…By dating U-Pb age of zircon grains by ion microprobe (SHRIMP) from the felsic tuff that unconformably overlies the Mitaki igneous rocks at 427.2 ± 7.6 Ma (midSilurian; Gradstein et al, 2012), the Mitaki igneous rocks were interpreted to have formed at ca. 430 Ma (Aitchison et al, 1996). Later, Hada et al (2000) obtained high-precision U-Pb ages by TIMS from three samples of the Mitaki igneous rock at the type locality, i.e., 441.9 ± 4.5, 441.5 ± 4.4, and 439.7 ± 10 Ma, confirming the traditional age assignment.…”

“…These ages are mostly consistent with the previously reported U-Pb zircon ages of ca. 470-435 Ma (e.g., Aitchison et al, 1996;Hada et al, 2000;Osani et al, 2014), in particular, with the TIMS U-Pb upper intercept ages of 445-435 Ma for the zircon grains from the type Mt. Mitaki area (Hada et al, 2000).…”

Ambiguous biogeographical patterns mask a more complete understanding of the Ordovician to Devonian evolution of Japan

“…It possesses an Ordovician igneous and metamorphic basement succeeded unconformably by the volcaniclastic succession of the Yokokurayama Group in Shikoku Island (Aitchison et al 1996). Conglomerates within the sedimentary succession contain clasts of rhyolite, granite and acid tuff that may have been derived from an island arc or continental arc, and Umeda (1998a) considered the setting to be a forearc basin related to the South China palaeocontinent (the 'Yangtze Massif ').…”

“…The last group is particularly important for the stratigraphical interpretation of the succession (e.g. Aitchison et al 1996) as radiolarians can be recovered from a wide variety of rock types, including volcanogenic sedimentary units that are common in Japan (e.g. Umeda 1998a, fig.…”