scholarly journals Middle Jurassic - Early Cretaceous drastic paleoenvironmental changes in the Ordos Basin: Constraints on sandstone-type uranium mineralization

2021 ◽  
pp. 104652
Author(s):  
Tianfu Zhang ◽  
Xianyu Cheng ◽  
Shaoyi Wang ◽  
Peisen Miao ◽  
Cong Ao
1993 ◽  
Vol 30 (10) ◽  
pp. 2128-2138 ◽  
Author(s):  
Donald B. Brinkman ◽  
Jiang-Hua Peng

Ordosemys leios, n.gen., n.sp., from the Early Cretaceous Luohandong Formation, Zhidan Group, Ordos Basin, Inner Mongolia, is a primitive aquatic turtle with a reduced, fenestrated plastron. It shares with the members of the Centrocryptodira the presence of well-formed articular surfaces on the cervical and caudal vertebrae. Within the Centrocryptodira, characters of the cervical vertebrae suggest it is more closely related to the Polycryptodira than is the Meiolaniidae. Ordosemys shares with the Chelydridae the presence of two procoelous anterior caudals, but this character may be primitive for the Polycryptodira. Characters of the basicranial region of the braincase shared by Ordosemys and the Chelonioidea support a sister-group relationship between these two taxa, but a sister-group relationship between Ordosemys and the Polycryptodira is more strongly supported by characters shared by the Chelonioidea and other members of the Polycryptodira.


Palaeoworld ◽  
2018 ◽  
Vol 27 (2) ◽  
pp. 188-201 ◽  
Author(s):  
Yun-Feng Li ◽  
Chun-Lin Sun ◽  
Hongshan Wang ◽  
David L. Dilcher ◽  
Xiao Tan ◽  
...  

1993 ◽  
Vol 30 (10) ◽  
pp. 2163-2173 ◽  
Author(s):  
Dale A. Russell ◽  
Zhi-Ming Dong

An articulated skeleton of a 1 m long theropod from Early Cretaceous strata in Inner Mongolia is clearly referrable to the Troodontidae, representing the most complete specimen known of this group of small carnivorous dinosaurs. The tail and neck of the animal were curled next to its body upon burial; the upper surface of the skeleton was badly damaged by erosion. Previously unknown details of troodont morphology include a quadratic contact with the braincase wall (forming part of a channel leading to the lateral depression), a presacral vertebral count possibly similar to that of most theropods, absence of ossified caudal tendons, presence of a rod-like clavicle, and absence of sternal ossifications. A new genus and species (Sinornithoides youngi n.gen., n.sp.) is established for the specimen on the basis of its short skull, laterally directed orbital rim of the frontal, and elongated hind limb. A reassessment of character distributions in other small theropods and primitive birds must be completed before troodontid affinities can be established with greater precision.


China Geology ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 52-66
Author(s):  
Ruo-shi Jin ◽  
◽  
Xiao-xi Feng ◽  
Xue-ming Teng ◽  
Feng-jun Nie ◽  
...  

2020 ◽  
Author(s):  
Dengfa He

<p>Craton is the stable unit of the lithosphere. The cratonic basin is thus the sedimentary basin developed upon craton. It has long been recognized as a kind of basin characterized by minor tectonic deformation and stable architecture. With the increasing evidences in the recent years, it is noticed that it has much more mobility, and is controlled not only by the lithospheric plate movements but also by the deep mantle activation. To explore the mobile behaviour of cratonic basin is an important window to address the intra-continental deformation mechanism. Taking the Ordos basin as an example, based on the new deep boreholes, the high-resolution seismic reflection profiles, cores, and the outcrops around the basin, the paper establishes the chronology of tectonic movement around the Ordos basin utilizing the integrated method of the isotopic dating, the bio-stratigraphy, and the sequence stratigraphy. It shows that, the basin developed the ten regional unconformities, underwent multi-period volcanic activities during the Middle Proterozoic, the late Early Paleozoic, the Late Triassic, and the Early Cretaceous. It was subjected to multi-stage compression, such as the Late Ordovician to Devonian, the Late Triassic, the Late Jurassic to Early Cretaceous, and the Neogene to Quaternary. Upon the crystalline basement of the Archaean and the Lower Proterozoic, the basin underwent five distinct extension-compression cycles, such as the extension in middle Proterozoic and compression in late Proterozoic, the extension in Cambrian to early Ordovician and compression in late Ordovician to Devonian, the extension in Carboniferous to middle Triassic and compression in late Triassic, the extension in early to middle Triassic and compression in late Jurassic to Cretaceous, and the extension in Paleogene and compression in Neogene to Quaternary, with a charter of a much longer period of the earlier cycle and a shorter period of the later cycle, and a longer period of extension and a shorter period of contraction in each cycle. The extension-compression cycle controlled the formation and evolution of the Ordos oil and gas super basin.</p>


2017 ◽  
Vol 54 (8) ◽  
pp. 893-901 ◽  
Author(s):  
Mingjian Dai ◽  
Yunbiao Peng ◽  
Chenjun Wu ◽  
Yangquan Jiao ◽  
Lu Liu ◽  
...  

The Ordos Basin is one of the top oil-, gas-, and coal-producing basins in China and is increasingly recognized as an important uranium mineralization province. Uranium deposits occur near the margin of the basin and are mainly hosted in the sandstones of the Jurassic Zhiluo Formation. The Daying uranium deposit in the Ordos Basin is one of the most important large sandstone-type uranium deposits in China. Based on thin section analysis and electron microprobe measurements, we used analytical chemical data to study the characteristics of the Daying uranium deposit, including the type, structure, particle size, material composition, chemical composition, form, and valence state of the uranium. The uranium mainly exists in three forms: an absorbed form, independent minerals, and uranium-bearing minerals. Most of the uranium in the ore is U4+, and the proportion of U6+ ranges from 18% to 55%, with an average of 33%. The proportion of U6+ is relatively high in the cores containing low-grade ore. This study provides a reference for determining the best smelting technology with which to further develop this deposit.


2015 ◽  
Vol 60 (21) ◽  
pp. 1858-1865 ◽  
Author(s):  
Chunlin Sun ◽  
Yunfeng Li ◽  
David L. Dilcher ◽  
Hongshan Wang ◽  
Tao Li ◽  
...  

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