Geochemistry of subsurface Late Quaternary ironstones in Rajshahi and Bogra Districts, Bangladesh: implications for genetic and depositional conditions

The present study deals with the geochemistry of Late Quaternary ironstones in the subsurface in Rajshahi and Bogra districts, Bangladesh with the lithological study of the boreholes sediments. Major lithofacies of the studied boreholes are clay, silty clay, sandy clay, fine to coarse grained sand, gravels and sands with(fragmentary) ironstones. The ironstones contain major oxides, Fe_2 O_3*(*total Fe)(avg. 66.6 wt%), SiO_2(avg. 15.3 wt%), Al_2 O_3(avg. 4.0 wt%), MnO(avg. 7.7 wt%), and CaO(avg. 3.4 wt%). These geochemical data imply that the higher percentage of Fe_2 O_3* along with Al_2 O_3 and MnO indicate the ironstone as goethite and siderite, which is also validated by XRD data. A comparatively higher percentage of SiO_2 indicates the presence of relative amounts of clastic quartz and manganese-rich silicate or clay in these rocks. These ironstones also have significant amounts of MnO(avg. 7.7 wt%) suggesting their depositional environments under oxygenated condition. Chemical data of these ironstones suggest that the source rock suffered deep chemical weathering and iron was mostly carried in association with the clay fraction and organic matter. Iron concretion was mostly formed by bacterial build up in swamps and marshes, and was subsequently embedded in clayey mud.Within the coastal environments, the water table fluctuates and goethite and siderite with mud and quartz became dry and compacted to form ironstone.

Origin of iron-rich minerals,ooids and pisoids in the Jurassic ooidal ironstones of the Labino-Malkin region(Caucasus)

This study investigates the Middle Jurassic rocks of the Labino-Malkin zone(Caucasus),represented by ooidal ironstones,biogenic limestones,and nodular phosphorites.All rocks contain ooids/pisoids.Based on the mineral composition,nine types of ooids and three possible scenarios for their formation have been identified.The mineral composition of ooids indicates the variable conditions of their deposition and repeated changes in physical and chemical conditions of the environment,including fluctuations in theredox regime.The access of oxygen in the bottom environment as a factor of increasing oxic conditions was associated with the regression of the sea and/or the inflow of meteoric waters.The main sources of ooids are the drift of material from the continent and convecting metal-bearing meteoric and/or deep solutions.

New Data on Coal, Gypsum, Iron and Silica Sand Deposits and Geochemical Exploration (Pakistan): Revision of 25 Years History of Dinosaur Discoveries from Pakistan

Discoveries of many coal seams at depths by drilling carried by Geological Survey of Pakistan in Sor Range and Harnai Gochina, extended the coal seams at depth which is challenge for mine owners to exploit feasibly. Bed to bed gypsum samplings (and their chemical analyses) of huge gypsum deposits from Sulaiman foldbelt is a base for industrialist and also planers to develop cement and gypsum industries to increase export and foreign exchange for the development of area and Pakistan. Low and high grade sedimentary iron deposits, silica sand and uranium host rocks and their extensions in Sulaiman and Kirthar foldbelts are presented. Anomalies of a few base metals arise as a result of geochemical exploration carried at part of Loralai District of Balochistan. Theropod dinosaurs were frequent in India, while Poripuchian titanosaurs (Sauropoda, Dinosauria) were frequent in Pakistan. Besides some ichnotaxa, many bone taxa such as 1 titanosauriform, 14 titanosaurian sauropod (including one new titanosaur), and 3 theropod dinosaurs are established from Pakistan. Among these 12 titanosaur species and 3 theropod species are named in about 10 km2 area of Vitakri dome and 2 titanosaur species are named in about a few hundred square meter area of Mari Bohri (Kachi Bohri) which is about 10 km westward from Vitakri dome. Pakistan is a unique country which discoverd 14 diversified titanosaurs in a short area and also in a short period (67 - 66 million years ago/Ma). About 400 bones found from a few meter thick upper part of upper shale horizon of latest Maastrichtian Vitakri Formation which is base for titanosaur taxa. Cranial material is in low fraction (but include significant diverse snouts), caudal vertebrae are prominent, the cervicals, dorsals and sacrals have significant numbers, forelimb and hind limb bones have balanced fraction. Humeri, femora and tibiae are most common. To know the position of Pakistani titanosaurs among titanosaurs and sauropods, there is a need to extend list of characters for phylogenetic analyses. This broad feature list should include main characters of titanosaurs from Pakistan and also from global world.

Ooidal ironstones in the Meso-Cenozoic sequences in western Siberia: assessment of formation processes and relationship with regional and global earth processes

This study investigates the process of formation of ooidal ironstones in the Upper Cretaceous-Paleogene succession in western Siberia.The formation of such carbonate-based ironstones is a continuing problem in sedimentary geology,and in this study,we use a variety of data and proxies assembled from core samples to develop a model to explain how the ooidal ironstones formed.Research on pyrite framboids and geochemical redox proxies reveals three intervals of oceanic hypoxia during the deposition of marine ooidal ironstones in the Late Cretaceous to the Early Paleogene Bakchar ironstone deposit in western Siberia;the absence of pyrite indicates oxic conditions for the remaining sequence.While goethite formed in oxic depositional condition,chamosite,pyrite and siderite represented hypoxic seawater.Euhedral pyrite crystals form through a series of transition originating from massive aggregate followed by normal and polygonal framboid.Sediments associated with goethite-chamosite ironstones,encompassing hypoxic intervals exhibit positive cerium,negative europium,and negative yttrium anomalies.Mercury anomalies,associated with the initial stages of hypoxia,correlate with global volcanic events.Redox sensitive proxies and ore mineral assemblages of deposits reflect hydrothermal activation.Rifting and global volcanism possibly induced hydrothermal convection in the sedimentary cover of western Siberia,and released iron-rich fluid and methane in coastal and shallow marine environments.This investigation,therefore,reveals a potential geological connection between Large Igneous Provinces(LIPs),marine hypoxia,rifting and the formation of ooidal ironstones in ancient West Siberian Sea.

Mechanical Properties and Compression Sensibility of Ironstone Aggregate Concrete

Radiation-shielding concrete was made with ironstone aggregate. The compressive strength is affected by multi factors. The electrical conductive properties and smart performance was discovered and investigated. Experimental results show that concrete conductivity rapidly declines with increasing loading, and the conductivity is much lower than the initial value of conductive aggregate of concrete, which may be related to special characters of ironstone. This kind of concrete has widely potential applications due to its special characters and low cost.

The formation of authigenic deposits during Paleogene warm climatic intervals:A review

Although Paleogene warm climatic intervals have received considerable attention for atmospheric and oceanographic changes,the authigenic mineralization associated with these time spans remains overlooked.An extensive review of the literature reveals a close correspondence between the high abundance of glauconite and warm climatic intervals during the Paleogene period.The abundance of phosphorite,ironstone,lignite and black shale deposits reveals similar trends.Although investigated thoroughly,the origin of these authigenic deposits is never understood in the background of Paleogene warming climatic intervals.A combination of factors like warm seawater,hypoxic shelf,low rate of sedimentation,and enhanced rate of continental weathering facilitated the glauconitization.The last factor caused the excess supply of nutrients,including Fe,Si,K,Mg and Al through the rivers,the cations needed for the formation of glauconite.The excessive inflow of nutrient-rich freshwater into the shallow seas further ensured high organic productivity and stratification in shallow shelves,causing hypoxia.The consequent rapid rise in sea-level during the warm periods created extensive low-relief shallow marine shelves starved in sediments.Oxygen-deficiency in the shallow marine environment facilitated the fixation of Fe into the glauconite structure.The inflow of nutrient-rich water during the warm climatic intervals facilitated the formation of phosphorite,ironstone,and organic-matter-rich sedimentary deposits as well.Although global factors primarily controlled the formation of these authigenic deposits,local factors played significant roles in some of the deposits.Therefore,phosphorites formed in marine conditions with open circulation within the tropical zone.While lush growth of rainforest covers in the tropical belt facilitated the formation of coastal lignite.