Quasihydrostatic limit of LiF as a pressure transmitting medium is investigated by synchrotron radiation x-ray diffraction combined with the diamond anvil cells technique up to 60 GPa at room temperature. The equation-ofstate parameters of LiF are determined to be 𝑉0 = 65.7(2) Å 3 , 𝐵0 = 58(3) GPa and 𝐵 ′ 0 = 4.9(2) in the silicon oil environment; 𝑉0 = 67.4(3) Å 3 , 𝐵0 = 51(3) GPa and 𝐵 ′ 0 = 4.7(2) without pressure transmitting medium. The full width at half maximum of LiF ( 111) peak increases with the increase of pressure in two independent experiments. The pressure distribution in the sample chamber is estimated by line-scanning x-ray diffraction measurements across the chamber's center, which presents as homogeneous with 𝑃max − 𝑃min of about 1 GPa below 40 GPa.

No abstract

Early Cretaceous desert sedimentary system was developed in Northwest Ordos Basin. At present, the research degree of desert sedimentary paleogeography is low. The research on paleogeographic environment of Early Cretaceous sedimentary sandstone has guiding significance for the exploration of uranium resource and underground water resource in Northwest Ordos Basin. Based on the previous basic geological data of the lower Cretaceous in the Northwest of Ordos, through field geological survey, drilling core observation, and paleocurrent measurement, the sedimentary paleogeographic environments in different periods of Early Cretaceous had been studied. The results show that the lower Cretaceous in Northwestern Ordos Basin can be divided into two sedimentary cycles, the lower sedimentary cycle composed of Luohe Formation and Huachi-Huanhe Formation, and the upper sedimentary cycle composed of Luohandong Formation and Jingchuan Formation. Alluvial, Aeolian, and desert lake depositional systems were developed. The main sedimentary facies were alluvial fan, braided river, sand dune, dry valley, and dry lake. Alluvial fan and braided river facies had mainly developed in Luohe Formation. Braided fluvial facies mainly had developed in Huachi-Huanhe Formation, and alluvial fans locally developed around it. The deposits in Luohandong Formation were mainly aeolian sandstone, and the alluvial fan facies were inherently developed at Western and Northern margins. The depositional environment of Jingchuan formation is mainly river and lake. The tectonic evolution of lower Cretaceous had controlled the development of paleogeographic environment, and sedimentary facies had controlled the development of aquifer system. The paleogeographic environment of Early Cretaceous is conducive to the reduction and enrichment of uranium and the development of metallogenic units.