Genesis of tuff interval and its uranium enrichment in Upper Triassic of Ordos Basin, NW China

Recently measured high gamma ray values in the Yanchang Formation of the Upper Triassic in the Ordos Basin have added an interesting and controversial twist to the study of the formation’s uranium enrichment and genesis.High uranium and thorium contents in the tuffaceous layer cause high gamma ray values in the Yanchang Formation.Petrographic studies,major elements,rare earth elements(REEs),and trace elements have been systematically analyzed to determine the composition,geochemical environment,and diagenetic processes of the layer.The observed color of the tuffaceous layer in the study area varies from yellow to yellowish brown.The tuff consists of matrix supported with sub-rounded to sub-angular lithic fragments.These lithic fragments probably derived from pre-existing rocks and incorporated into the tuffaceous layer during volcanic eruption.Quartz,plagioclase,and biotite were observed in well to poorly sorted form,in addition to framboidal pyrite and organic laminae.Measured ratios of SiO_2/Al_2O_3 ranged from 3.277 to 6.105 with an average of 3.738.The ratio of TiO_2/Al_2O_3 varied from 0.037 to 0.201 with an average of 0.061,indicating that the sediments of the tuffaceous layer originated from an intermediate magma.REE distribution patterns show sharp negative Eu anomalies,indicating a reducing environment,which is suitable for uranium deposition.A reducing environment was confirmed by black shale in the base of the Yanchang Formation.Such black shale has high organic matter content that can take kerogene from mudstone and provide a reducing environment for uranium enrichment in the tuffaceous layer.Moreover,negative Eu anomalies and the REE patterns indicate a subduction-related volcanic arc environment as the magma source of the tuffaceous layers.High values of Rb,Ba,and Sr might be the result of fluid phase activities;low values of Hf and Eu indicate the involvement of crustal material during diagenesis of the tuff.Discrimination diagrams(Th/Yb vs Ta/Yb,Th/Hf vs Ta/Hf)suggest an active continental margin as the tectonic setting of source volcanoes.Plots of Nb versus Y,Rb versus Y+Nb,TiO_2 versus Zr,and Th/Yb versus Nb/Yb of the tuffaceous content point to calc-alkaline continental arc-related magmatism.We concluded that uranium enrichment in the tuffaceous layer was supported by oxidation–reduction.

Mortality characteristics during the two waves of COVID-19 in India:A retrospective observational study

Objective:To evaluate patient demographic characteristics and risk factors for mortality during the first and the second wave among COVID-19 patients in a tertiary care hospital of India.Methods:Data were taken from the hospital’s electronic system for COVID-19 patients from August 2020 to December 2020,and the second from January 2021 to May 2021.The mortality rate,demographic and clinical characteristics,laboratory profile,and reasons for the death of the two waves were retrieved and compared,and the risk factors of the two waves were determined.Results:In the first wave,1177 COVID-19 cases visited the hospital and 96(8.2%)died.In comparison,the death rate in the second wave was significantly higher(244/2038,12.0%)(P<0.001).No significant difference in age[60(50-69)vs.60.5(53-70),P=0.11]or gender(P=0.34)was observed between the two waves.Compared to the first wave.there were significantly more cases with fever,cough,weakness,loss of taste and smell,and sore throat during the second wave(P<0.05),but significantly fewer cases with kidney disease(6.6%vs.13.5%,P=0.038)and diabetes mellitus(35.7%vs.50.0%,P=0.015).Besides,during the second wave,more patients had abnormal X-ray findings,higher levels of lymphocytes and serum ferritin(P<0.05).In addition,there were significant differences in the rate of death cases with acidosis,septic shock,acute kidney injury,diabetes mellitus,cardiovascular events,hypothyroidism(P<0.05).Multivariate regression showed that during the first wave,age(OR:1.10;95%CI:1.02-1.21),diabetes mellitus(OR:3.16;95%CI:2.08-3.53),and abnormal X-ray(2.67;95%CI:2.32-2.87)were significant independent risk factors of mortality;while in the second wave,age(OR:1.13;95%CI:1.12-1.28),diabetes mellitus(OR:8.98;95%CI:1.79-45.67),abnormal X-ray(OR:12.83;95%CI:2.32-54.76),high D-dimer(OR:10.89;95%CI:1.56-134.53),and high IL-6(OR:7.89;95%CI:1.18-47.82)were significant independent risk factors of mortality.Conclusion:Overall mortality and incidence of severe diseases are higher in the second wave than the first wave.Demographic characteristics,co-morbidities,and laboratory inflammatory parameters,especially D-dimer and IL-6,are significant risk facors of mortality during the COVID-19 pandemic.

The Uranium Prospects in Mika Region, Northeastern Nigeria

Uranium exploration especially in currently non-producing countries like Nigeria possesses high economic prospect. This study investigates a new uranium prospect in Mika, Northeastern Nigeria. The Mika uranium mineralization is located in Mika, Taraba State. Two lodes were identified and additional nine (9) trenches were added. The main lode in the west extends about 10 m, ore vein strikes 348&deg;, inclination 42&deg;and the strike of the lode 306&deg;with average uranium content of 18%. The eastern trench is about 8 × 4 × 6 m which exposes a veinlet of pitchblende. From the petrography, one can deduce that the granitic host rock has suffered deformation resulting in crushing of quartz crystals and stretching of plagioclase. The uraninite and chalcedony in the late phase filled up the fractures along the crystal grain boundaries as veinlets. The laboratory gamma ray analysis of the samples showed that the secondary uranium content is 0.1%, while the primary uranium ore grade is 1.5%. Radiometric in situ measurements showed that Th and K ranges from 47.3 - 3654 ppm and 4.26% - 6.26% respectively. From the survey, a strong radiometric zone extends 800 × 35 m in an NW-SE direction and has highest radiation content of 1200 cpm against the background count rate of 30 cpm. Generally, the uranium concentrations in the ores in Mika area range from 0.03% - 0.12%. Since only the surface occurrences have been explored, the study area is a good prospect for future development when properly explored. The North-eastern Nigeria has been roughly explored by Nigeria Uranium Mining Company (NUMCO) in 1980, but no formal exploration had been followed after that, especially near the site of this article. The company (ACE Mines, Ltd) of the first author was among the few uranium mining companies approved in the list of Nigerian Geological Survey agency of Abuja in Nigeria. The authors determined the coordinates of the site in their first survey which formed the prospect area in the licence.

Stratigraphy and Structure of Dhamtaur Area, District Abbottabad, Eastern Hazara, Pakistan

Pre-Cambrian to Paleocene age sedimentary rocks predominantly characterize the fold and thrust belt of eastern Hazara division. The Hazara Slate Formation is the oldest rock unit which represents the Precambrian sequence. The Permian and Triassic sequences are missing. The Jurassic sequence comprises Samana Suk Formation whereas the Cretaceous exposed is Chichali and Lumshiwal formations. The Eocene sequence consists of Nammal and Sakessar formations. The structural fabric of the area is mainly attributed to a series of northwest trending parallel to en echelon anticlines and synclines. Most of these folds are found to be asymmetric and are Northwest facing. Several thrust faults verging both to the north have been mapped that generally dissect the forelimbs of the anticlinal structures. But the following study going to be focus on surface structural features as well as subsurface projections of folds and faults. Study of such structural features has get prime importance in economic geology such as petroleum geology, mining geology and engineering geology. In our study area subsurface projection of folds and faults along the structural transects of the area suggests that these structures have formed as a result of shortening associated with ramping from a regional basal decollement. All the structures clearly demonstrate that the eastern Hazara area has been subjected to compressional deformation/stresses oriented northeast southwest. The repetition of rock units indicates, folding in the area and thrusting of Pre-Cambrian Hazara Formation over younger Paleocene Lockhart Formation, evidence of thrust fault. There are unconformable contacts between Hazara and Samana Suk, Chichali and Lumshiwal, Kawagarh and Hangu and Lockhart formations indicate fluctuation in the environment of deposition. The Bagnotar Fault, Dhamtaur syncline and Thai anticline are the major structural features identified and reported in the study area.