Organic geochemical and petrographic characteristics of the Cambrian-Ordovician organic-rich marine shales in Scandinavia

This work used organic geochemistry and organic petrology to study the depositional environment,organic matter characteristics,and thermal maturity of the Cambrian-Ordovician organic-rich marine shales in the Baltic Basin.The main macerals in Cambrian samples include alginite,bituminite and solid bitumen,while zooclastic macerals become the major proportion of organic matter in the Ordovician samples.As the maturity increase,solid bitumen becomes abundant and dispersed.Semifusinite-like maceral was observed only in Furongian of well DBH15/73,which probably indicates the local intrusion of Permo-Carboniferous dolerite dikes.The programmed pyrolysis results show that immature,early mature,and over-mature samples are developed.However,the data of high-uranium Furongian samples were greatly altered by igneous intrusives from local dikes.HIo calculation model is simulated based on pyrolysis data and fitted according to the least-square fitting method.The simulated fitting HIo:400mg HC/g TOC(369.5 mg HC/g TOC,430.5 mg HC/g TOC as 95%confidence bounds)is within the worldwide marine shale HI_(o)and indicates a marine anoxia and transgressive sea with shallow water column(organofacies B).

Geochemical indices of soil development on basalt rocks in arid to sub-humid climosequence of Central Iran

Quantitative weathering indices are efficient tools in determining the soil development from the underlying rocks.In order to evaluate the effects of climate on the soils developed under an arid to sub-humid climosequence in central Iran,twenty soil-development indices were compared.Twentyfour samples from six pedons were analyzed for routine physico-chemical and geochemical analyses using X-ray fluorescence(XRF).The lowest and highest calculated soil development indices were observed in the arid and sub-humid regions respectively.Among the studied indices,fifteen indices showed similar trends concerning the intensity of weathering.The consistency of such trends reveals the feasibility of using these indices to evaluate basalt weathering rate and soil development in arid,semi-arid and sub-humid regions.This study demonstrated that,among the evaluated weathering indices,the Weathering Index of Parker(WIP)and mass transfer coefficient(τ)were the most proper indices for predicting basalt weathering intensity.This is due to the fact that these indices use the highly mobile earth elements which are the most sensitive elements in basalt chemical weathering.The calculated indices were subdivided into three subgroups including the ratios of mobile/immobile,mobile/mobile and immobile/mobile elements based on the elements used in their calculation.The state of soil evolution was more accurately predicted compared to the other subgroups using the mobile/immobile subgroup of indices.Overall,the weathering indices calculated using the mobile elements are better indicators of weathering intensity,soil formation and the exogenous processes across the arid to sub-humid climosequence.

Geotechnical Study of the Aptian Limestone of the Kef Region,Northwestern Tunisia:Evaluation for Industrial Use

This study aims to the initial characterization of Aptian sedimentary limestones in the Kef region located in the North-West of Tunisia in order to use in industrial fields. The limestone samples were collected from three outcrops respectively named Jebel Jerissa, Jebel Hmeima and Jebel Harraba. A geochemical characterization highlights a variation of the weight percentage (wt%) as follows: CaO (53 - 55), MgO (0.04 - 0.28), Al2O3 (0.07 - 0.51), Fe2O3 (0.41 - 2.87), and a loss on ignition (41.62 - 43.35). The other oxides (K2O, SO3, Na2O) are in trace amounts. Mineralogical analysis revealed that limestones contain more than 95% of calcite and the clay impurities are the minor phases detected. Petrographic study showed that these limestones are packestone-wakestone type. The hardness of Aptian limestones crosses the upper limit of the hard domain. Geotechnical tests reveal a Dry Micro Deval (MDS) coefficient varying from 23% to 33%, a Wet Micro Deval (MDH) coefficient with values oscillating around 26% to 36%, a Los Angeles coefficient (LA) about 25% against a value of the compressive strength ranging from 593 Kg/cm2 to 866 Kg/cm2. The gravimetric tests highlighted a flexural strength value from 106 Kg/cm2 at 208 Kg/cm2, while the ultrasonic coefficient oscillates from 4876 m/s to 5233 m/s, indicating the low porosity of these limestone (0.5% to 1%). The density recorded an average value of 2.50 g/cm3. The various properties studied have proved that the limestone studied can be used in various industrial fields such steel industry, aggregate, cement industry and marble.