Mica Minerals Research Articles

Petrophysical Properties of Clastic Reservoirs Using NMR Relaxometry and Mercury Injection Data: Bahariya Formation, Egypt

The Bahariya Formation is a sedimentary sequence, which was deposited under fluvial to shallow marine conditions at the beginning of the Upper Cretaceous (Cenomanian) transgression in the Western Desert of Egypt. Thirty sandstone core samples, obtained from the Bahariya Formation, are conducted to NMR measurements and the relaxation time T2 = 100 μs and 600 μs were estimated. Application of a model related core-porosity and transverse relaxation time (T2) measured from NMR spectrum; the cementation exponent of Wyllie's type is outlined with high accuracy. Consequently, the water saturation and hydrocarbon saturation will be significantly enhanced. The irreducible water saturation (Swirr) calculated from the mercury injection capillary pressure (MICP) measurements is related to the normalized area under < 4 μs of transverse relaxation time (T2) and a regression model is calculated with a reliable coefficient of correlation permitting calculation of (Swirr) with high accuracy. Lithologic laminations presented in some intervals of the Bahariya Formation have great consequences on both the Mercury injection capillary pressure (MICP) measurements and nuclear magnetic Relaxometry (T2) as well. Thin sections and SEM-micrographs were made for some selected core samples in order to recognize petrography and mineralogy of the Bahariya sandstones. Glauconitic, mica, zircon, rutile and pyrite minerals are predominant in the laminated sandstones intervals.

Mineralogical and Petrographical Characteristics of Hornfels from Kowary (The Lower Silesia)

Abstract Hornfels from the closed “Wolność” mine (Kowary, the Lower Silesia) are recognized as thermally metamorphosed rocks belonging to hornblende-hornfels facies or locally a facies of pyroxene hornfels. Their texture reveal the traces of some deformations such as folding or fractures. Their protholit is described as a pelitic deposit enriched with clay minerals. The sediment was altered into meta-pelities-aleurites after the diagenesis, and later the rock was intensely thermally metamorphosed at the contact with the intrusion of the Karkonosze granitoid. Three varieties are distinguished based on their colour: green, grey and black. Green and black colours result from the predominance of hornblende and biotite over other rock components, respectively. Whereas grey hornfels are composed of similar amounts of both mafic minerals: biotite and hornblende. Quartz, mica minerals (biotite and muscovite), amphibole, (hornblende), acid plagioclase and andalusite, epidote group (clinozoisite), orthoclase and pyroxene make up hornfels components. Locally, andalusite is accompanied by sillimianite, which indicates a higher degree of contact metamorphism alterations. Three generations of minerals are distinguished in the rocks: allogenic (I), metamorphic (II) and hydrothermal (III). The allogenic phases are represented by heavy minerals such as zircon, apatite and monazite, which are characteristic of the protholit. The main components of the rocks (e.g. quartz, hornblende, feldspars, andalusite, sillimanite, mica minerals) belong to metamorphic minerals. Chalcopyrite, pyrite and fluorite are surely hydrothermally originated phases. Granitoides found at the contact zone with hornfels indicate traces of metasomatic alteration as a result of endomorphism in this region.

The reclamation of mica flakes from tailing disposal using gravity separators and flotation

A sample from the small-sized tailing pile of an Iranian mica processing plant was subjected to a series of mica recovery experiments. Mineralogical and microscopic investigations indicated that the dominant mica mineral was phlogopite which was accompanied by plagioclase feldspars. Before beneficiation studies, the particle size distribution of the representative sample was obtained, and the specifications of each size fraction were investigated in detail. It was observed that the largest portion of mica (31%) is accumulated in the size range of 0.3 to 2.0 mm. Afterward, gravity concentration and flotation experiments were carried out. Results proved that shaking table could produce a mica concentrate with grade of 74%. Also, according to the flotation tests, it seemed the best size fraction was -150+75, and after that, -100+150. Flotation in combination with attrition scrubbing produced a concentrate with 92% mica content and 70% recovery. Finally, with respect to the results of all implemented experiments, a processing flow sheet was proposed for mica reclamation from the mentioned waste disposal.

Geochemical characteristics of major and trace elements in Sahinali Coals, Aydin, Turkey

ABSTRACTIn this study, geochemical behavior of elements is investigated in 25 coal samples collected at 10 locations of Şahinli coaliferous units at southeast of Aydın, Turkey. In all the samples, X-ray powder diffraction and inductively coupled plasma mass spectrometry analyses were performed and element and mineral compositions were determined. Total organic carbon (TOC) values of coals are between 14.6 and 37.7 wt% with average of 28.5 wt%. Samples are composed of quartz, calcite, feldspar, dolomite, mica, gypsum, and salt minerals which are accompanied by illite-, kaolinite-, and smectite-type clay minerals. Comparison of average element contents of world coals and studied samples yields that K > Fe > As > U > Cs > Y > Er > Al > Th > Rb > Yb > W > Tb > Dy > Lu > Ce > Sm > La > Ho > Si > Nd > Gd > Tm > Eu > Nb > Pr > Pb > Sn > Ni > Cu > Ga > Ta > Sb > Zr > Cd > V > Zn > Co > Mo > P > Hf > Ba are found to be enriched, while Mn > Be > Ca > Sr > Bi > Mg are found to be depleted. Statistically elements are correlated with TOC.

Chemical effects of carbon dioxide sequestration in the Upper Morrow Sandstone in the Farnsworth, Texas, hydrocarbon unit

Numerical geochemical modeling was used to study the effects on pore-water composition and mineralogy from carbon dioxide (CO2) injection into the Pennsylvanian Morrow B Sandstone in the Farnsworth Unit in northern Texas to evaluate its potential for long-term CO2 sequestration. Speciation modeling showed the present Morrow B formation water to be supersaturated with respect to an assemblage of zeolite, clay, carbonate, mica, and aluminum hydroxide minerals and quartz. The principal accessory minerals in the Morrow B, feldspars and chlorite, were predicted to dissolve. A reaction-path model in which CO2 was progressively added up to its solubility limit into the Morrow B formation water showed a decrease in pH from its initial value of 7 to approximately 4.1 to 4.2, accompanied by the precipitation of small amounts of quartz, diaspore, and witherite. As the resultant CO2-charged fluid reacted with more of the Morrow B mineral matrix, the model predicted a rise in pH, reaching a maximum of 5.1 to 5.2 at a water–rock ratio of 10:1. At a higher water–rock ratio of 100:1, the pH rose to only 4.6 to 4.7. Diaspore, quartz, and nontronite precipitated consistently regardless of the water–rock ratio, but the carbonate minerals siderite, witherite, dolomite, and calcite precipitated at higher pH values only. As a result, CO2 sequestration by mineral trapping was predicted to be important only at low water–rock ratios, accounting for a maximum of 2% of the added CO2 at the lowest water–rock ratio investigated of 10:1, which corresponds to a small porosity increase of approximately 0.14% to 0.15%.

Mineralogical, isotopic (K-Ar) and structural-textural characteristics of the Jurassic terrigenous complex in different paleotectonic settings (Greater Caucasus, Chechnya - Georgia)

The variations in structural, textural, mineralogical and geochemical (radiometric) characteristics in the lower to middle Jurassic siliciclastic sediments of the transect across Chanty-Argun R., Mountain Chechnya and Georgia are considered. This transect crosses areas of different types of deformations from northern zone of weak deformation to southern zone of intensive deformation and cleavage. The southward change in clay mineral associations, polytypical modifications of mica minerals, their crystallinity index, a.o. are observed along the transect. The increase of intensity of secondary alternations of the rocks and dimensions of cleavage enabled the change in K-Ar-system. This is resulted in significantly younger values of measured radiologic age corresponding to older stratigraphic age.

Geology and environments of subglacial Lake Vostok.

The reconstruction of the geological (tectonic) structure and environments of subglacial Lake Vostok is based on geophysical surveys and the study of mineral particles found in cores of accreted ice and frozen lake water (sampled after the lake was unsealed). Seismic reflection and refraction investigations conducted in the southern part of Lake Vostok show very thin (200-300 m) sedimentary cover overlying a crystalline basement. Most of this thin veneer is thought to have been deposited during temperate-glacial conditions in Oligocene to Middle Miocene time (ca 34-14 Ma). The composition of the lake-bottom sediments can be deduced from mineral inclusions found in cores of accreted ice. Inclusions are represented by soft aggregates consisting mainly of clay-mica minerals and micrometre-sized quartz grains. Some of these inclusions contain subangular to semi-rounded rock clasts (siltstones and sandstones) ranging from 0.3 to 8 mm in size. In total, 31 zircon grains have been identified in two rock clasts and dated using SHRIMP-II. The ages of the studied zircons range from 0.6 to 2.0 Ga with two distinct clusters between 0.8 and 1.15 Ga and between 1.6 and 1.8 Ga. Rock clasts obviously came from the western lake shore, which is thus composed of terrigenous strata with an age of not older than 600 Ma. The sedimentary nature of the western lake shore is also confirmed by seismic refraction data showing seismic velocities there of 5.4-5.5 km s(-1) at the bedrock surface. After Lake Vostok was unsealed, its water (frozen and sampled next season) was also studied with scanning electron microscopy and X-ray microprobe analysis. This study showed the existence of calcium carbonate and silica microparticles (10-20 μm across) in frozen water.

Oxygen isotope perspective on crustal evolution on early Earth: A record of Precambrian shales with emphasis on Paleoproterozoic glaciations and Great Oxygenation Event

We present stable isotope and chemical data for 206 Precambrian bulk shale and tillite samples that were collected mostly from drillholes on all continents and span the age range from 0.5 to 3.5 Ga with a dense coverage for 2.5–2.2 Ga time interval when Earth experienced four Snowball Earth glaciations and the irreversible rise in atmospheric O2. We observe significant, downward shift of several ‰ and a smaller range of δ18O values (7 to 9‰) in shales that are associated with the Paleoproterozoic and, potentially, Neoproterozoic glaciations. The Paleoproterozoic samples consist of more than 50% mica minerals and have equal or higher chemical index of alteration than overlying and underlying formations and thus underwent equal or greater degrees of chemical weathering. Their pervasively low δ18O and δD (down to −85‰) values provide strong evidence of alteration and diagenesis in contact with ultra-low δ18O glacial meltwaters in lacustrine, deltaic or periglacial lake (sikussak-type) environments associated with the Paleoproterozoic glaciations. The δDsilicate values for the rest of Precambrian shales range from −75 to −50‰ and are comparable to those for Phanerozoic and Archean shales. Likewise, these samples have similar ranges in δ13Corg values (−23 to −33‰ PDB) and Corg content (0.0 to 10 wt%) to Phanerozoic shales. Precambrian shales have a large range of δ18O values comparable to that of the Phanerozoic shales in each age group and formation, suggesting similar variability in the provenance and intensity of chemical weathering, except for the earliest 3.3–3.5 Ga Archean shales, which have consistently lower δ18O values. Moreover, Paleoproterozoic shales that bracket in age the Great Oxidation Event (GOE) overlap in δ18O values. Absence of a step-wise increase in δ18O and δD values suggests that despite the first-order change in the composition of the atmosphere, weathering cycle was not dramatically affected by the GOE at ∼2.4–2.3 Ga. Shales do not show comparable δ18O rise in the early Phanerozoic as is observed in the coeval δ18O trends for cherts and carbonates. There is however a sharp increase in the average δ18O value from the Early Archean to the Late Archean followed by a progressively decelerating increase into the Phanerozoic. This decelerating increase with time likely reflects declining contribution of mantle-extracted, normal-δ18O crust and lends support to crustal maturation and increasing 18O sequestration into the crust and recycling of high-δ18O (and 87Sr/86Sr) sedimentary rocks. This secular increase in the δ18O composition of the continental crust could have also had a mild effect on seawater δ18O composition.

Geochemical, Sedimentological and Mineralogical Characterization of Surficial Sediments in Eynak Marsh (North of Iran)

A multidisciplinary study of the sedimentology, geochemistry and mineralogy has been conducted to understand the linkage between marsh and alluvial sediments and also their potential sources in Eynak marsh, North of Iran. The influence of the upstream potential sources on recent sediment geochemistry has been discussed based on geochemical, sedimentological and mineralogical results. A spatial grain size distribution study was carried out to investigate the hydrodynamic and deposition system of the marsh. So, the surficial sediment sampling was carried out to describe the sedimentological parameters and elemental geochemistry of sediments in Eynak marsh. Mineralogical complexes are mainly made up of felsic minerals such as quartz, calcite, feldspar, pyrite, mica, and clay minerals (in very low values) indicated by high amounts of Al, Ca, and Ni. As expected, the mineralogy of sediments is controlled mainly by the rock formations. Also sediment textures are controlled by the hydrodynamic condition in the marsh. So its distribution has been influenced by distance from the entrance sediments to Eynak marsh. The results showed that there are no enrichments related to fine grain sediment distributions. An association of Al with the trace elements such as Sc, Y, La, Ce, and Zr indicates that their distributions are mainly controlled by the felsic rocks in the upstream. On the other side, due to the waste water entrance to the marsh, Ni and Pb concentration could be under the effects of anthropogenic activities around the marsh. Results represented high values for Mn concentration (min 462, max 1784 and average 1037 ppm) and it showed a significant correlation with Ca, Sr, and Mg. A redox habitat and constantly calm hydrodynamic circumstance in the study area, likely cause high concentration of Ca, Sr, and Mg, and Mn. And they are representing negative correlations with some elements such as Al, Be, Fe, K, and Na.

Petrofacies and tectonic setup of Kaimur Group of rocks, Son Valley, India

The paper embodies results of petrofacies and detrital mineralogical aspects of Scarp and Dhandraul sandstones of Upper Kaimur Group, Son Valley. These sandstones are medium to coarse grained and moderately to well sorted. The constituent mineral grains are subangular to subrounded. These sandstones consisting of various types of quartz, rock fragments, mica, feldspar and heavy minerals. The plots of petrofacies in Qt–F–L, Qm–F–Lt, Qp–Lv–Ls and Qm–P–K ternary diagrams reveal that these sandstones belong to the continental block, recycled orogen, rifted continental margin tectonic regime and maturity and stability of the source region. These sandstones were derived from Palaeoproterozoic and Mesoproterozoic granite, granodiorite, gneiss and metasedimentary rocks of Mahakoshal Group and Chotanagpur granite–gneiss. The sediment composition extensively modified during weathering warm humid climate at the surface area and weathering during transport before burial thereby providing mineralogical maturity to the Upper Kaimur Sandstone.

OPTIMIZATION OF MEASUREMENT SPEED FOR SPECTRAL GAMMA RAY AND CLAY MINERAL IDENTIFICATION

Gamma ray log is a logging tool to capture the radioactive level of a rock or formation measured in API units. This logging tool generally has a capability to differentiate between permeable and impermeable layers. Usually the impermeable layer tends to have higher radioactivity compared to the permeable one except for the feldspar bearing formation. In addition, another capability of this logging tool is to determine the kind of clay mineral, by using ratio data between Thorium and Potassium. This laboratory experiment used Spectral Gamma Ray (SGR) equipment at LEMIGAS Routine Core Laboratory. The quality of gamma ray log measurement is significantly affected by the speed of the conveyor belt. During the experiment, the measurement speed of 30 m/hour is the optimum speed to achieve good quality data and time efficiency with the data amount of 169 points/meter. The result of SGR measurement gives the reading on the content of Uranium, Thorium and Potassium. The Thorium and Potassium content are compared and plotted in Quirein graphic which was modified by Schlumberger in 1985. Using this crossplot, we can identify the presence of Chlorite, Montmorillonite, Kaolinite, Illite, mixed layer Feldspar, Mica, and Glauconite minerals. A case study conducted on Wells A1, A2, A3 and A4, indicated that the result of this crossplot were similar to the measurement using XRD.

Removal of Gangue Minerals Containing Major Elements from Karlıova–Derinçay (Bingöl) Lignite Using a Reverse Flotation Method

The removal of gangue minerals containing major elements was investigated using a reverse flotation method. Experiments were conducted on lignite samples, with high-ash and low-sulphur contents taken from a lignite field in Karliova–Derincay (Bingol), Turkey. Predominant gangue minerals in the samples were found to be quartz, gypsum, feldspar minerals, mica minerals, and clays (smectite group). Preliminary flotation studies showed that gangue materials are more buoyant than the lignite sample. Some parameters that markedly influence the effectiveness of reverse flotation, such as grinding time, pH, collector type and volume, frother type and volume, and salt, were investigated. Quartz was found to cause a major problem in terms of reverse flotation. Flotation measurements showed that anionic collectors in an acidic medium result in the following element reduction order: sulphur trioxide > ferric oxide > magnesium oxide > calcium oxide > silicon dioxide > aluminium oxide.

Petrographic characteristics of intrusive rocks as an evaluation tool of their technical properties

Abstract The main petrographic variables of intrusive rocks that influence the technical test methods common used within the aggregate industry were identified and evaluated, the aim being to investigate whether petrographic description could be used as a tool for the preliminary quality evaluation of different rock groups. Evaluation of the dependence of the technical test methods on petrographic variables covered 26 intrusive rocks, including some of their altered varieties (orthogneisses), divided into two groups: 17 granitoids and 9 gabbroids. The selective designated samples were analysed to determine their petrographic characteristics and resistance to fragmentation, wear and wear by abrasion from studded tyres. In order to identify the complicated associations between the petrographic and technical properties, multivariate statistical evaluation was performed. The results of statistical evaluation highlighted that mean grain size of mica minerals, grain size distribution, content of mica minerals and mean grain size were the main variables influencing the technical properties of granitoid rocks, while for gabbroid rocks, the main influences were the frequency of microcracks, mica content, grain size distribution and mean grain size.

Deposition of the Upper Rewa Sandstone Formation of Proterozoic Rewa Group of the Vindhyan Basin, M.P., India: A Reappraisal

Abstract The Upper Rewa Sandstone Formation of the Rewa Group in the Vindhyan basin is composed mainly of medium to very fine grained, iron pigmented arenaceous rocks variously interpreted as fluvial, marine or continental deposits. The Upper Rewa Sandstone Formation consists of channelized, laterally shifting sand bodies comprising 1-2 m thick fining upward (FU) sharply/erosionally based cycles. Each shoaling bar cycle is characterized by presence of large scale planar and trough cross-bedding, horizontal bedding showing primary parting lineation, wave and current ripples, herringbone cross-bedding and tidal bundles with double mud-drapes and indicates marine environment of deposition and rule out the possibility of continental sedimentation. However, channelized nature of sand bodies composed of shoaling bar cycles with signatures of wave modification and exposure in the lower part of the succession and well developed horizontally bedded lithofacies showing primary parting lineation and well sorted character of sandstones in the upper part of the succession may imply deposition under subtidal to intertidal setting in estuarine to bordering beach environments. The palaeocurrent study shows polymodal to bimodal and unimodal palaeocurrent patterns. The dominant polymodal palaeocurrent patterns with temporal trends directed towards NW, N and SW also corroborate marine origin and sediment dispersal under combined action of wave and currents. Petrographically, sandstone is quartzarenite and consists of mostly monocrystalline quartz, feldspar, mica, rock-fragments and heavy minerals such as hypersthene, zircon, hornblende, tourmaline, rutile, augite, kyanite and andalusite indicating sediment contribution from mixed sedimentary/metamorphic and igneous source terrain. Qm-F-Lt and Qt- F-Lt plots reveal that the Upper Rewa Sandstone Formation shows continental block province with stable craton (C) and in uplifted basement (B) where C&amp;gt;B.

A novel purification technique for noble gas isotope analyses of authigenic minerals

Noble and active gases are released from geological samples during gas extraction for noble gas isotope analyses. The active gases should be removed before inletting to mass spectrometers for the analyses. The normal noble gas preparation systems can clean up most geological samples. However, authigenic minerals from sedimentary rocks in oil/gas fields contain organic matter, which cannot be cleaned up by the normal preparation systems and thus influence the noble gas analyses. We introduce a novel gas purification system (PRC patent No. ZL201320117751.2), which includes several reversible purification pumps with different absorbing and degassing temperatures. It can well clean up water steam, carbon dioxide and organic gases. Mica minerals are often used for 40Ar/39Ar dating. A muscovite sample (2082MS) which could not be cleaned up by the normal preparation system with two SAES NP10® getters, becomes the test sample for a comparative experiment in this study. The experiment is assigned into 4 sections with the organic gas removal system (OGRS) “Closed/Opened” in turn. When the OGRS is closed only with two NP10 getters for purification, the 40Ar intensities increase in curves with inlet time because of impurities, the 40Ar/39Ar dating results yield age errors about ±2%–±1% (2σ). When the OGRS is opened for purification, in contrast, the 40Ar intensities decrease linearly with inlet time. This indicates that the gases have been cleaned up effectively, and the 40Ar/39Ar results yield ages with errors in ±0.4%. The OGRS is very helpful to obtain high-quality analysis data.

Investigation of meso-failure behaviors of Jinping marble using SEM with bending loading system

In this study, the meso-failure mechanism and fracture surface of Jinping marble were investigated by means of scanning electron microscope (SEM) with bending loading system and laser-scanner equipment. The Yantang and Baishan marbles specimens from Jinping II hydropower station were used. Test results show that the fracture toughness and mechanical behaviors of Yantang marble were basically higher than those of Baishan marble. This is mainly due to the fact that Baishan marble contains a large percentage of dolomite and minor mica. Crack propagation path and fracture morphology indicated that the direction of tensile stress has a significant effect on the mechanical behaviors and fracture toughness of Baishan marble. For Yantang and Baishan marbles, a large number of microcracks around the main crack tip were observed when the direction of tensile stress was parallel to the bedding plane. Conversely, few microcracks occurred when the direction of tensile stress was perpendicular to the bedding plane. The presence of a large number of microcracks at the main crack tip decreased the global fracture toughness of marble. The results of three-point bending tests showed that the average bearing capacity of intact marble is 3.4 times the notched marble, but the ductility property of the defective marble after peak load is better than that of the intact marble. Hence, large deformation may be generated before failure of intact marbles at Jinping II hydropower station. The fractal dimension of fracture surface was also calculated by the cube covering method. Observational result showed that the largest fractal dimension of Yantang marble is captured when the direction of tensile stress is parallel to the bedding plane. However, the fractal dimension of fracture surface of Yantang and Baishan marbles with tensile stress vertical to the bedding plane is relatively small. The fractal dimension can also be used to characterize the roughness of fracture surface of rock materials.

Exsolution of rutile or apatite precipitates surrounding ruptured inclusions in garnet from UHT and UHP rocks

AbstractThis study describes halos of rutile ± apatite needles and/or plates centred on quartz (inferred former coesite) inclusions or multiphase inclusions in garnet. Both types of central inclusions are surrounded by cracks. The multiphase inclusions contain mica or carbonate minerals and are interpreted to represent decrepitated fluid inclusions. Examples from two localities are examined: (i) ultrahigh‐temperature (UHT) metapelitic gneisses from the southern end of the Central Maine Terrane in northeastern Connecticut, USA (rutile only) and (ii) ultrahigh‐pressure (UHP) diamondiferous saidenbachite from the Saxonian Erzgebirge (rutile and apatite). The needles of apatite or rutile are typically oriented in three directions within garnet. Chemical zonation in garnet shows clear Ti or P depletion halos corresponding spatially with the rutile or apatite inclusion halos. The radii of the inclusion halos, when measured from the centre of the central inclusions, are about two to several times the radii of the central inclusions. We propose that the inclusion halos of rutile ± apatite formed by exsolution out of Ti‐bearing and/or P‐bearing garnet during retrogression. Because of its strength, garnet can internally maintain higher pressures than the surrounding matrix. Nonetheless, if the inclusion pressure is significantly greater than the confining lithostatic pressure, then deformation of the host garnet can occur. During exhumation, high internal pressures relative to the matrix can result from retention of fluid entrapment pressure or a phase change with a large positive volume increase (e.g. coesite → quartz). The differential stress imposed on the garnet adjacent to the central inclusion preceding and during mechanical failure would create dislocations and other crystalline defects which are ideal sites for exsolved precipitates to nucleate and grow. The strain‐induced exsolution hypothesis is consistent with observations. (i) The radii of the halos are roughly consistent with the pressure vessel model or the multi‐anvil model for an inclusion, which predict that differential stress will drop off sharply away from the boundary of the central inclusion into the host garnet. (ii) The rutile or apatite inclusions formed in Ti‐ or P‐bearing garnet adjacent to ruptured central inclusions; rutile or apatite are rare or absent elsewhere in garnet, even in areas of high‐Ti or high‐P concentration. In addition, rutile is absent in areas surrounding the central inclusion that were depleted in Ti prior to rupturing (e.g. garnet rims that lost Ti during retrogression). Thus, both elevated Ti ± P concentrations and proximity to inclusions which deformed the host garnet were necessary for halo formation. (iii) Reintegrated garnet Ti or P contents in and adjacent to the halos obtained using wide‐beam electron probe microanalysis are consistent with local derivation of the Ti or P necessary to form rutile and apatite from garnet. Elevated Ti ± P concentrations in aluminous garnet are mostly found in UHT, HP/UHP, granulite and mantle environments. Consequently, the phenomena described will most likely occur in such settings.

New Route of Utilization of Pegmatites Tailings to Application as a Ceramics Raw Materials

The proposal to obtain a new route for exploitation of tailings from pegmatite emerged from the need of many companies that showed to reuse of these tailings as raw materials ceramics. The pegmatites represent a large part of available industrial minerals. These can be classified into: kaolin, feldspar, mica, quartz and metallic minerals such as tantalite / columbite and others. The consumer markets for these minerals are glassmaking, ceramic industries, paper, pulp, metallurgy, etc. Order for the product is fit for sale ceramics and metals companies must be of high purity of this raw material. Therefore, the process of separation of these minerals must be carried out as effectively as possible. In this study, surveys have been made to the development of a new process route which facilitates, an optimized manner, separation from pegmatite, concentrated in the waste process of extracting companies, so that a better product shall be passed through the ceramic industry.

Effects of moisture content on the strength of tropically weathered granite from Malaysia

The strength of rock is significantly affected by weathering and moisture content. Due to climate conditions in the tropics, rock is weathered significantly and produces a thick weathering profile. Designing structures in rock with varying degrees of weathering creates problems due to varying material properties. This study was carried out to investigate the effects of moisture content on weathered Malaysian granite of various grades, focusing on strength which is an essential parameter in designing engineering rock structures. Weathering identification tests, Schmidt hammer tests, and impact index tests were performed at the site as part of the field study. In the laboratory, samples were analyzed for durability, point load index, moisture content, density, and X-ray diffraction (XRD), and underwent petrographic analysis to examine the mineralogy. The results revealed that the degree of feldspars weathering and the amount of clay minerals are good weathering grade identifiers. The amount of fresh feldspar decreased from 72 % in grade I specimens to 0 % in grade V specimens, with an increase of altered feldspar and clay minerals from 0 to 60 %. The presence of feldspar and mica minerals above 1 % tended to increase the susceptibility of rock to the influence of water. It was also found that the reduction in strength becomes greater with an increasing weathering grade. In addition, the discolouration of rock material from greyish to brownish red also can be a good indicator of strength reduction due to moisture content. Based on the results, the extent of strength reduction depends upon the weathering grade, petrographic constituents and duration of water immersion.

Distribution of Diagenetic Alterations in Fluvial Channel and Floodplain Deposits in the Triassic Narrabeen Group, Southern Sydney Basin, Australia

Abstract In the Narrabeen Group, floodplain shale and siltstone are abundant in the Wombarra Claystone, Stanwell Park Claystone and Bald Hill Claystone whereas the Newport Formation is a fine-grained lagoonal deposit. Medium-and coarse-grained fluvial channel sandstone is common in the Coalcliff, Scarborough and Bulgo. Sandstone composition includes mostly lithic grains with minor quartz, feldspar, mica and heavy minerals; litharenites and sublitharenites are common and quartzarenites are rare. The diagenetic alterations include compaction, quartz overgrowths, authigenic clay minerals, carbonate cement and authigenic feldspar. Quartz overgrowths are present in the channel, floodplain, lagoonal and shallow marine facies but are more common in the channel facies. Also, the channell facies are characterised by pore-filling carbonate cement, grain-coating carbonate cement and carbonate replacement of grains. Carbonate cement, pore-filling clays and grain-coating clays occur in all the channel, floodplain, lagoonal and shallow marine facies. Fluvial channel and floodplain facies contain feldspar overgrowths which disappear in the lagoonal and shallow marine facies. Dissolution of unstable grains is observed in the channel, floodplain and lagoonal facies but is more abundant in the channel facies in the Narrabeen Group. Mechanical and chemical compaction is conspicuous in the channel facies but also occurs in the floodplain and lagoonal facies.