Detrital zircon U–Pb ages of the Murui Formation in the Zhalantun area: Implications for the Early Cretaceous tectonic setting of the southern Great Xing’an Range, NE China

This paper reports U–Pb ages of detrital zircons from a series of clastic and pyroclastic rocks from the Murui Formation in the southern Great Xing’an Range (GXR), NE China, with the aim of constraining the depositional age of this poorly dated unit. These data, combined with the petrographic and sedimentology characteristics of the rocks, are used to constrain the sediment sources and tectonic setting of the provenance and provide wider insight into the tectonic evolution of the southern GXR during the Late Mesozoic. Two lithic arkose samples have dominant age groups at 249–250, 159–160, 136–147, and 394–415 Ma, and 301–323, 278–288, 209–237, and 142–163 Ma, respectively. The U–Pb zircon data constrain the maximum depositional age of the Murui Formation to 136 ± 1 Ma, that is, the Early Cretaceous. A lithic–crystal tuff from the upper Murui Formation yielded zircons with a weighted mean U–Pb age of 136 ± 1 Ma (n = 47, mean square weighted deviation (MSWD) = 2.2), indicating that volcanic activity was contemporaneous with sedimentation of the Murui Formation. U–Pb dating of zircons from a pyromeride in the Baiyingaolao Formation that was erupted unconformably onto the Murui Formation yielded a peak age of ~120 Ma, which constrains the depositional age of the Murui Formation to 120–136 Ma. Further dating of detrital zircons shows a range of ages, indicating the various of sediment origins. The Late Jurassic to Early Cretaceous volcanic rocks in the GXR served as the principal detrital sources for the Murui Formation in the southern GXR. Grain size and modal analysis of the sediments shows that the depositional environment was a stable intracontinental fluvial setting, and the provenance of the detritus was most likely a magmatic arc. According to stratigraphic contact relations, the Baiyingaolao Formation is supposed to have obvious intervals with lower volcanic strata, which combined with disparities between the southern and northern GXR in terms of the duration of volcanism, magmatic events, and the depositional age of the Murui Formation. We can conclude that the restricted occurrence of the Early Cretaceous detritus between the earlier and later phases of volcanism suggests progressive exhumation of the southern GXR in the Early Cretaceous. These may relate to post-orogenic extension related to oceanic subduction. The southern GXR remained a site of active sedimentation during the continental extension period across the whole of NE China in the Late Jurassic to Early Cretaceous.

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Neotectonic movement in the southern margin of the Ordos Block inferred from the Qianhe River terraces near the north of the Qinghai–Tibet Plateau

The Qianhe River flows between the Liupanshan Orogen and the Ordos Block, with the river valley controlled by the southern margin fault of the Ordos Block. Five asymmetrical terraces exist on the banks of the Qianhe River, which correspond to the five terraces of the Wei River. Each terrace is composed of alluvial deposits at the bottom beneath loess deposits, which are characterized by alternating loess (L) and paleosol (S) layers, with the basal layers of the loess deposits being S0, S1, S53, S8, and L15 from T1 to T5. The heights of the five terraces T5, T4, T3, T2, and T1 are 220 to 260 m, 130 to 160 m, 60 to 80 m, 20 to 30 m, and 8 to 10 m, respectively, above the present valley, and their ages are 1.2, 0.8, 0.5, 0.13, and 0.01 Ma, respectively. These ages are generally consistent with the several uplift periods of the Qinghai–Tibet Plateau in the medium and late stages. Therefore, neotectonic movement is the controlling factor of river terrace formation in the periphery of the Ordos Block. According to the south-west movement of the river channel in the lower reaches of the Qianhe River, it can be estimated that the Ordos Block rotated about 20° counterclockwise in the Pleistocene.

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Mkango Announces Exercise Of Warrants

London / Calgary: January 12, 2018 – Mkango Resources Ltd. (AIM/TSX-V: MKA) (the \’Company\’ or \’Mkango\’) announces that following the exercise of warrants over 2,156,060 common shares without par value in the share capital of the Company (\’New Shares\’), it has received an aggregate cash consideration of £137,650 and is issuing the equivalent number of New Shares. The warrants being exercised comprise 2,006,060 warrants at 6.6 pence each and 150,000 warrants at 3.5 pence each. The

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Collaboration between scientists and stakeholders vital to climate readiness in Alaska

Alaskan residents rely on sustenance species like salmon, caribou, and moose, but their needs can be at odds with companies mining natural resources and conservationists. The state’s future will depend on collaboration between these various stakeholders, and scientists can help bridge the gap between these groups, according to researchers at Southern Oregon University.

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Study suggests heavy rains from tropical cyclones distort the ground below

Earth’s surface is constantly shifting, expanding and compressing in response to atmospheric and hydrologic forces from aboveground. A new study finds that compression of Earth’s crust is correlated with heavy rainfall from hurricanes and typhoons, known collectively as tropical cyclones. The added weight of all that water likely causes the ground underneath the storm to deform, according to the study’s authors.

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