Characterizing a weathering profile over the Kuantan Basalt

Three broad morphological zones can be differentiated; the top pedological soil (Zone I) being 3.60 m thick and comprising brown, soft to stiff, clays. The intermediate saprock (Zone II) is 1.12 m thick and consists of brown, very stiff, sandy silt with many lateritic concretions, whilst the bottom bedrock (Zone III) is an outcrop of vesicular olivine basalt with weathering along joints. Constant volume samples show the saprolite (sub-zone IC) to have dry unit weights of 11.78 to 12.80 kN/m3, whilst the solum (sub-zones IA and IB), and saprock, have values ranging from 10.65 to 11.09, and from 11.35 to 11.50, kN/m3, respectively. Porosities are variable; the saprolite with the lowest values of 52 to 56% and the solum and saprock with values of 57 to 60%. Clay and silt contents increase up the profile with a corresponding decrease in sand and gravel contents. Colloid (<1 μm size) contents especially increase up the profile from 10 to 15% in saprock through 30 to 40% in saprolite and exceeding 57% in the solum, These increasing colloid contents point to the increasing effects of pedological processes. Thin-sections of weathered rims (1-2 cm thick) show alteration of basalt to start with formation of micro-cracks (Stage 1) that become stained by secondary iron oxides and hydroxides. Decomposition of the essential minerals then occurs in the order: olivine (Stage 2), augite (Stage 3), and plagioclase feldspar (Stage 4). An increase in apparent porosity, but a decrease in unit weights and specific gravity, reflect these stages of weathering; the boundary between ‘rock’ and ‘soil’ material occurring when all olivine and augite crystals have decomposed. It is concluded that the weathering profile results from in situ alteration of basalt due to lowering of an unconfined groundwater table; pedological processes giving rise to further alteration.

Origin of alkali olivine basalts and hawaiites in the western Mexican arc: Evidence of rapid phenocryst growth and magma mixing during ascent along fractures

A detailed petrological study is presented to constrain the origin of a suite of alkali olivine basalt and hawaiite (&gt;5 wt% MgO) lavas that were erupted in a rift zone within the western Mexican arc (Trans-Mexican Volcanic Belt), adjacent to the Sangangüey andesitic stratovolcano, together with more evolved lavas (mugearites and benmoreites; &lt;5 wt% MgO). As previously documented in the literature, the Sangangüey mafic lavas are devoid of any arc geochemical signature, despite their location within an arc. In this study, a new olivine-melt thermometer/hygrometer, based on the partition­ing behavior of Ni2+ and Mg2+, was applied to the Sangangüey basalts (SB). The results show that the high-MgO (&gt;9 wt%) SB crystallized at higher temperatures and lower melt-water contents (0–1.3 wt%) compared to high-MgO arc basalts (≤5.7 wt% H2O) erupted in the west-central Mexican arc. The Sangangüey lavas with 5–8 wt% MgO display evidence of mixing between high-MgO alkali olivine basalts and low-MgO mugearites. It is proposed that the unique composition of the mugearites (i.e., low SiO2 contents and elevated FeO and TiO2 contents) is the result of partial melting of mafic lower crust driven by the influx of high-MgO intraplate basalts under relatively hot, dry, and reduced conditions. On the basis of crystal textures and compositional zoning patterns, it is shown that both phenocryst growth and magma mixing occurred rapidly, most likely during ascent along fractures, and not slowly during prolonged storage in a crustal magma chamber.

Saturated hydraulic conductivity (Ks) of earth materials in a weathering profile over the Kuantan Basalt, Pahang, Malaysia

Three broad morphological zones can be differentiated at the weathering profile; the top, 3.80 m thick, pedological soil (zone I with sub-zones IA, IB and IC) comprising soft to stiff, brown clays and the bottom bedrock (zone III) being an outcrop of vesicular olivine basalt. The intermediate zone II (saprock) is 1.12 m thick and consists of brown, very stiff, sandy clayey silt with many lateritic concretions. Laboratory constant head permeability tests show the saturated hydraulic conductivity (Ks) to vary with depth; sub-zone IB having a conductivity of 0.007 cm/hr, and sub-zone IC (saprolite), and zone II (saprock), having conductivities of 0.147, and 0.447, cm/hr, respectively. The conductivity values show no correlation with physical properties of the earth materials, but increase with increasing sand, gravel, and silt, contents. The conductivity values also decrease with increasing clay and colloid contents. The low hydraulic conductivity of sub-zone IB will lead to surface runoff and ponding over natural ground surfaces during rainfall events, though over disturbed ground surfaces, infiltration is anticipated in view of exposed saprolite and saprock earth materials with relatively high conductivity

Nuclear Radiation Shielding Characteristics of Some Natural Rocks by Using EPICS2017 Library

Radiation leakage is a serious problem in various technological applications. In this paper, radiation shielding characteristics of some natural rocks are elucidated. Mass attenuation coefficients (µ/ρ) of these rocks are obtained at different photon energies with the help of the EPICS2017 library. The obtained µ/ρ values are confirmed via the theoretical XCOM program by determining the correlation factor and relative deviation between both of these methods. Then, effective atomic number (Zeff), absorption length (MFP), and half value layer (HVL) are evaluated by applying the µ/ρ values. The maximum μ/ρ values of the natural rocks were observed at 0.37 MeV. At this energy, the Zeff values of the natural rocks were 16.23, 16.97, 17.28, 10.43, and 16.65 for olivine basalt, jet black granite, limestone, sandstone, and dolerite, respectively. It is noted that the radiation shielding features of the selected natural rocks are higher than that of conventional concrete and comparable with those of commercial glasses. Therefore, the present rocks can be used in various radiation shielding applications, and they have many advantages for being clean and low-cost products. In addition, we found that the EPICS2017 library is useful in determining the radiation shielding parameters for the rocks and may be used for further calculations for other rocks and construction building materials.

Melilite-olivine neрhelinites of Mt. Tabaat (Makhtesh Ramon, Israel): Geological, petrographic and geochemical characteristics and conditions of genesis

Research subject. The melilite-olivine nephelinite subvolcanic body Tabaat, which includes melilite rocks found for the first time on the territory of Levant.Materials and methods. The chemical composition of minerals (about 400 analyzes) was determined out on a CAMECA SX-100 microanalyzer equipped with five wave spectrometers with crystal analyzers TAP, LPET and LLIF. The elemental composition was measured at an accelerating voltage of 15 kV, an electron beam current of 40 nA. The oxygen concentration was calculated from the condition of stoichiometric composition of silicate minerals and chromite. In addition, the results of earlier studies of minerals (150 analyses) and data on melt inclusions were used.Results. The Tabaat subvolcanic body, which is part of the Early Cretaceous olivine-basalt-basanite-nephelinite association Makhtesh Ramona (Negev, Israel), has a complex concentrically-zonal structure, with olivine melanephelinites in the peripheral zone, melilite-olivine melanephelinites in the central and connecting zones normative and, less often, melilite-containing melanephelinites. Prismatic separation is widely manifested in the rocks. The fold-like bending and concave-curved edges of the prisms are a reflection of the plastic state of the cooling body and its ability to compress and accommodate a high fluid pressure, which develops during the formation of melilite nephelinites.Conclusion. All mineral diversity of rocks of the Mt. Tabaat is a derivative of a single portion of magmatic melt under conditions of its adiabatic cooling at the place of stabilization. A special role in the course of crystallization of the massif belongs to minerals with a high water content – analcime, zeolites, iddingsites, bowlingites and saponite-celadonites, which indicate the deuteric stage of its development. The study of melt inclusions in olivine and clinopyroxene showed the continuity of their composition with the composition of host melilite nephelinites and the importance of incongruent melting during the formation of melilite, which is a product of the reaction of nepheline with olivine or clinopyroxene.

Effect of different pH levels on adsorption and desorption of Pb in contrasting parent materials of south eastern agro climatic zone of Nigeria

Lead adsorption and desorption at different pH levels in acid soils of diverse parent materials were evaluated. The soil samples were collected from soils underlain by olivine basalt (Ikom), coastal plain sands (Ihiagwa) and false bedded sandstone (Ishiagu). The collected samples were air -dried, crushed, sieved with a 2 mm sieve and analyzed in the laboratory. The adsorption of lead (Pb) increased with increasing solution pH. At pH 3, 4 and 6, the adsorption of Pb was higher in false bedded sandstone than the other soils. At pH 5, adsorption of Pb was higher in olivine basalt than the other soils. Except at pH 3, desorption of Pb was higher in coastal plain sands than the other soils. At the same time it was lower in false bedded sand stone than the other soils at all pH. At pH 5, adsorption of Pb had a significant positive correlation with organic matter (r =0.774481, p≤ 0.05), while at pH 6, it had a significant positive correlation with soil pH (r =0.738401, p ≤ 0.05). Organic matter and soil pH are the most critical soil properties affecting adsorption-desorption of Pb on these soils.

Influences of CO2 on the Microstructure in Sheared Olivine Aggregates

Shear deformation of a solid-fluid, two-phase material induces a fluid segregation process that produces fluid-enriched bands and fluid-depleted regions, and crystallographic preferred orientation (CPO) characterized by girdles of [100] and [001] axes sub-parallel to the shear plane and a cluster of [010] axes sub-normal to the shear plane, namely the AG-type fabric. Based on experiments of two-phase aggregates of olivine + basalt, a two-phase flow theory and a CPO-formation model were established to explain these microstructures. Here, we investigate the microstructure in a two-phase aggregate with supercritical CO2 as the fluid phase and examine the theory and model, as CO2 is different from basaltic melt in rheological properties. We conducted high‐temperature and high-pressure shear deformed experiments at 1 GPa and 1100&ordm;C in a Griggs-type apparatus on samples made of olivine + dolomite, which decomposed into carbonate melt and CO2 at experimental conditions. After deformation, CO2 segregation and an AG-type fabric occurred in these CO2-bearing samples, inconsistency with basaltic melt-bearing samples. The SPO-induce CPO model was used to explain the formation of the fabric. Our results suggest that the influences of CO2 as a fluid phase on the microstructure of a two-phase olivine aggregate is similar to that of basaltic melt and can be explained by the CPO-formation model for the solid-fluid system.

Mineralogy and Chemical Composition of Basalt Stone Tools in Some Iraqi Archaeological Sites

Basalt stone tools were collected from some Iraqi Archaeological Sites. Twenty-one samples were studied petrographically, mineralogically, and chemical composition. Five samples were from the Gaara Depression north of Rutba town, seven samples from Tarmiya, north Baghdad, seven samples from Dalmij site, east of Diwaniya city, and two samples from Jordan, which were used for comparison. The studied samples were classified into three groups, according to their mineralogy and texture: Group A: Vesicular Basalt, Group B: Dolerite, and Group C: Olivine Basalt. These stones most probably were used as a hand axe, grinder, hammer, and other uses, as well as for buildings, like those used in Qasar Al- Azraq and Umm Al- Jamal archaeological sites in Jordan. These basalt rocks most probably were transported by an ancient man from Harrat Al-Sham, which extends through Syria-Jordan-Saudi Arabia, or from NE Syria through a trade route that connected between source areas and the studied archaeological sites in Iraq.

Rhönite in Cenozoic alkali basalt from Changle, Shandong Province, China, and its significance

Four Cenozoic, rhönite-bearing alkali-olivine basalt samples from the Changle area (Shandong Province, China) show an intracontinental character and were generated in an extensional setting. Petrographic studies document different generations of rhönite. In three samples, rhönite occurs either as a reaction product surrounding coarse-grained corundum, spinel and phlogopite or along cleavage planes in phlogopite. In one sample rhönite forms disseminated crystals in a mantle xenolith, possibly formed by a reaction of coarse-grained orthopyroxene or spinel with a melt. Rhönite exhibits a wide range of compositions: 22.9 wt %–33.0 wt % SiO2, 13.3 wt %–19.0 wt % Al2O3, 9.4 wt %–19.9 wt % MgO and 10.210.2 wt %–24.5 wt % FeO. The derived primary substitutions include (1) SiIV + NaVII = (Al, Fe3+)IV + CaVII, (2) MgVI = (Fe2+, Mn2+)VI and (3) TiVI + (Mg + Fe2+ + Mn2+)VI = 2Fe3+VI. Rare-earth-element (REE) patterns of euhedral rhönite crystals from the mantle xenolith (sample SS17) and those surrounding spinel (sample CL04) have a concave-upward shape for the heavy rare-earth elements (HREEs) and are slightly enriched in the light rare-earth elements (LREEs). These patterns resemble those of kaersutitic amphibole and kaersutite reported from basanite, olivine nephelinite, transitional alkali-olivine basalt and hawaiite. In contrast, REE patterns of the other two samples containing fine-grained, anhedral and acicular rhönite crystals (samples CL01 and EGS03) are relatively steep, with lower HREE and higher LREE abundances, similar to those of ocean island basalts (OIBs). All types of Changle rhönite show positive Nb, Ti and V anomalies in spidergrams normalized to primitive mantle. Mineral assemblages of the studied samples indicate that rhönite crystallized at different stages within a temperature range from about 950 to 1180 ∘C and at pressures below 0.5 kbar, with fO2 below the NNO buffer. The chemical composition of Changle rhönite is interpreted to depend on the composition of the initial silicate melt, the redox conditions during crystallization and the composition of the minerals involved in reactions to form rhönite. Similar to metasomatic mantle amphibole, the compositions of Changle rhönites cover the I-Amph (I-amphibole) and S-Amph (S-amphibole) fields, indicating that they may have formed due to an intraplate metasomatic event, overprinting an older metasomatic subduction episode.