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The Bengge biotite aegirine‐augite syenite (BAS) is located in the southern part of Yidun Arc, eastern margin of the Tibetan Plateau area. It is an integral part of the Bengge ultrapotassic rocks (UPR), an alkalic complex mainly consisting of BAS, biotite pyroxene syenite (BPS), and biotite syenite (BS). Geochronological studies including zircon LA‐ICPMS U–Pb dating and biotite 40Ar/39Ar dating have been conducted on the Bengge BAS to constrain its emplacement age. The zircon U–Pb dating yields a wide range of ages from 209 ± 2 Ma to 239 ± 2 Ma, with the concordia 206Pb/238U age being 228 ± 8.9 Ma (MSWD = 0.13). Meanwhile, the biotite 40Ar/39Ar dating yields a plateau age of 205.7 ± 1.5 Ma. The whole‐rock Zr‐saturation temperature (Tzir‐sat) of the Bengge BAS has shown to be very low (86 ± 13°C to 634 ± 13°C), which is much lower than Ti‐in‐zircon temperature (>758°C) of the zircons used for U–Pb dating. This indicates that the zircons in the Bengge BAS are inherited, and they were already present in the BAS melts before the melts became Zr‐saturated. Similarly, the Tzir‐sat of the Bengge BPS and BS are 346 ± 14°C ~ 549 ± 13°C and 281 ± 14°C ~ 525 ± 13°C, respectively, which is also too low for magmatic zircon crystallization in the melts. The inherited zircons of Bengge BAS have typical features of magmatic zircon, with high (Sm/La)N ratios (2.54–819), Ce/Ce* ratios (4.77–304) and low La concentration. Low εHf (T) values (−5.0 to 0.42) and high U/Yb (0.67–12.6) values imply that the inherited zircons (209–239 Ma) in the Benge BAS are derived from an early arc‐magma system of the Yidun Arc. The biotite 40Ar/39Ar dating constrains the Bengge BAS emplacement age at 205.7 ± 1.5 Ma, the time when the arc‐magma activity had ceased, and a regional geodynamic transition in the Yidun Arc from convergence to back‐arc spreading had started. [ABSTRACT FROM AUTHOR]

Dating the timing of motion on crustal shear zones is of tremendous importance for understanding the assembly of orogenic terranes. This objective is achieved in this paper by combining petrological and structural observations with novel developments in in situ U-Th-Pb geochronology of allanite. A greenschist facies shear zone within the Mont Blanc Massif is documented. Allanite is synkinematic and belongs to the mylonitic assemblage. LA- ICP- MS U-Th-Pb isotope analyses of allanite reveal high contents and highly radiogenic isotopic compositions of the common-Pb component. The use of measured Pb-isotope compositions of associated minerals (feldspars and chlorite) is critical for accurate common-Pb correction, and provides a powerful mechanism for linking allanite growth to the metamorphic assemblage. A mean 208Pb/232Th age of 29.44 ± 0.95 Ma is accordingly taken for synkinematic allanite crystallisation under greenschist facies conditions. This age reflects the timing of the Mont Blanc underthrusting below the Penninic Front and highlights the potential of directly dating deformation with allanite. [ABSTRACT FROM AUTHOR]

The Maizuru terrane, distributed in the Inner Zone of southwest Japan, is divided into three subzones (Northern, Central and Southern), each with distinct lithological associations. In clear contrast with the Southern zone consisting of the Yakuno ophiolite, the Northern zone is subdivided into the western and eastern bodies by a high-angle fault, recognized mainly by the presence of deformed granitic rocks and pelitic gneiss. This association suggests an affinity with a mature continental block; this is supported by the mode of occurrence, and petrological and isotopic data. Newly obtained sensitive high mass-resolution ion microprobe (SHRIMP) zircon U–Pb ages reveal the intrusion ages of 424 ± 16 and 405 ± 18 Ma (Siluro–Devonian) for the granites from the western body, and 249 ± 10 and 243 ± 19 Ma (Permo–Triassic) for the granodiorites from the eastern body. The granites in the western body also show inherited zircon ages of around 580 and 765 Ma. In addition, electron probe microanalysis (EPMA) monazite U–Th–total Pb dating gives around 475–460 Ma. The age of intrusion, inherited ages, mode of occurrence, and geological setting of the Siluro–Devonian granites of the Northern zone all show similarities with those of the Khanka Massif, southern Primoye, Russia, and the Hikami granitic rocks of the South Kitakami terrane, Northeast Japan. We propose that both the Siluro–Devonian and Permo–Triassic granitic rocks of the Northern zone are likely to have been juxtaposed through the Triassic–Late Jurassic dextral strike-slip movement, and to have originated from the Khanka Massif and the Hida terrane, respectively. This study strongly supports the importance of the strike-slip movement as a mechanism causing the structural rearrangement of the Paleozoic–Mesozoic terranes in the Japanese Islands, as well as in East Asia. [ABSTRACT FROM AUTHOR]

The article offers a study on zircon U-Pb dating of the rhyolitic tuff and rhyolite within the Manketouebo Formation in the southern Manzhouli area, with the aim to constrain the timing of the Manketouebo Formation. Topics discussed include Zircon U-Pb dating was performed using the Sensitive High-Resolution Ion Microprobe; and concludes that the rhyolitic tuff and rhyolite from the Manketouebo Formation was dated by the Sensitive high-resolution ion microprobe U-Pb method.

The article presents a study on the progress on zircon uranium-lead (U-Pb) isotopic geological dating technique. Topics discussed include benefits of zircon U-Pb dating in comparison to other isotope dating techniques; the ongoing development of zircon U-Pb isotope dating technique in the high time resolution (high-precision) and high spatial resolution; and the use of isotope dilution-thermal ionization mass spectrometry (ID-TIMS) by the high time resolution.