[SCG59-P04] The Lower Cretaceous groups in the Khabarovsk Krai, Far East Russia: Detrital-zircon-age spectra and tectonics
Keywords:detrital zircon, Lower Cretaceous, Far East Russia, Amur Complex, Zhuravlevka Complex
Materials The Amur and Zhuravlevka Cs. consist mainly of turbidite with rare occurrences of bivalve fossils. The Amur C. partly contains pelagic–hemi-pelagic siliceous rocks that have downward-younging age-polarity7). The Amur C. occurs on both sides of the Central Sikhote-Alin Fault (CSF), whereas the Zhuravlevka C. occurs to the east of CSF. We collected six sandstone samples from the Amur C. and seven sandstone samples from the Zhuravlevka C. along the Khabarovsk–Lidoga–Vanino Road. The two complexes in the study area strike NNE to NE and dip steeply westward. Here we make a very short description of collected samples in apparent ascending order.
Am1 [49°24′43.99″N, 136°42′39.57″E]: Quartzose arenite of the Gornoprotoka Formation.
Am2 [48°43′45.43″N, 135°48′27.76″E], Am5 [48°39′47.12″N, 135°29′59.98″E], and Am6 [48°39′57.41″N, 135°29′54.77″E]: Quartzose arenite from the interbedded sandstone and mudstone of the Pivan Formation.
Am3 [48°28′30.15″N, 135°27′50.92″E] and Am4 [48°39′43.18″N, 135°30′14.83″E]: Feldspathic arenite from the interbedded sandstone and mudstone of the Pivan Formation.
Zh1 [49°12′2.9″N, 139°6′49.5″E] and Zh2 [49°11′0.7″N, 139°4′19.9″E]: Feldspathic arenite of the Primanka Formation.
Zh4 [49°9′30.2″N, 138°54′35.9″E] and Zh5 [49°11′42.9″N, 138°52′59.4″E]: Feldspathic arenite from the sandstone-rich alternations of the Katalevka Formation.
Zh6 [49°11′58.3″N, 138°52′49.9″E]: Schistose feldspathic arenite of the Ust' Kolumbe Formation.
Zh7 [49°12′37.9″N, 138°52′7.3″E]: Feldspathic arenite from the interbedded sandstone and mudstone of the Ust' Kolumbe Formation.
Zh8 [49°15′29.8″N, 138°49′58.3″E]: Baked muddy sandstone of the Ust' Kolumbe Formation, cut by a 56-Ma rhyolitic dike.
Method We separated zircon from each sandstone sample, measured their U-Pb isotopic ratios with the laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) equipped in the Graduate School of Environmental Studies, Nagoya University, and calculated 238U-206Pb and 235U-207Pb ages from the isotopic ratios. Then we chose concordant grains with the %conc value (100 (238U-206Pb age)/( 235U-207Pb age)) between 90 and 110 and drew a probability density plot, a histogram, and a component bar chart (Fig. 1).
Results Figure 1 summarizes the result of our measurements.
The age of sedimentation The age of the youngest zircon of each sample (YZ; Fig. 1) constrains the maximum (oldest) age of sedimentation. Three samples of the Amur C. have the YZ corresponding to the Late Jurassic, suggesting that the Amur C. near Khabarovsk City may contain the Upper Jurassic. The Zhuravlevka C. except Zr5 have Early Cretaceous youngest zircons, and the YZs roughly have downward- (eastward-) younging age polarity. The Zhuravlevka C. along the Lidoga–Vanino Road has a similar geochronologic structure with the typical accretionary complex.
Provenance analysis In northeast Asia, 450–900 Ma plutons are distributed along the northeastern margin of the Heilongjiang Province, China, in the Khanka–Jiamusi Block1). Permian plutons widely occur on the southwest of the 450–900 Ma plutons6). Further to the southwest, Early Jurassic plutons occur from northeastern Jilin Province to the Korean Peninsula4). The sandstone provenance of the Amur and Zhuravlevka complexes, having abundant Jurassic–Permian and 450–900 Ma zircons, most likely covered both the Khanka–Jiamusi Block and the northeastern part of the present-day Korean Peninsula.
References 1) Bi et al., 2014: J. Asian Earth Sci., 96, 301–; 2) Khanchuk et al., 2016: J. Asian Earth Sci., 120, 117–; 3) Liu et al., 2017: Tectonics, 36, 2555–; 4) Sagong et al., 2005: Tectonics, 24, TC5002; 5) Tamaki et al., 2008: J. Geol. Soc. Jpn, 114, 207–; 6) Wu et al., 2011: J. Asian Earth Sci., 41, 1–; 7) Zyabrev et al., 2015: Geotectonics, 49, 533–.