Geochemistry, Mineralogy, and Genesis of Kaolin Deposits of Kachchh, Western India and Its Possible Industrial Application

New insights on mineralogy and genesis of kaolin deposits: The Burela kaolin deposit (Northwestern Spain)

Kaolin samples from the Jari deposit (Amazon region) were studied using various techniques to characterize its structural and crystallochemical aspects, and to establish its origin and evolution. A profile 60 m thick was selected in a kaolin mine (Morro do Felipe) located at the banks of the Jari river. Despite the great thickness of the deposit and the variety of kaolin types, the mineralogical composition is rather homogeneous and is mainly kaolinite associated with gibbsite and small amounts of quartz, anatase, goethite and hematite. The field observations and the morphological analysis indicate the existence of sedimentary features throughout the whole profile except for the upper aluminous clayey layer (Belterra Clay). This is evidence that the Rio Jari kaolin deposit originated from sedimentary material, the Alter do Chão Formation. The presence of alternating clay and sandy layers is explained by sedimentation processes with great depositional energy variation. Thus, the accumulation of thick clay layers was related to a low-energy phase, and during the high-energy phases, the deposition process led to the accumulation of sandy materials, constituted essentially of quartz and showing strong textural and structural variation. Later on, periods of hydromorphy were responsible for iron removal and consequently for the bleaching of the sedimentary formation. The crystallinity data show an increase of the structural disorder toward the surface associated with an increase in the amount of structural Fe in the kaolinite. The Rio Jari kaolin deposits should be considered as having originated from kaolinitic clay sediments of the Alter do Chão formation (protore) that was submitted to intensive lateritic weathering processes.

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For optimum bauxitisation conditions a relatively stable geomorphological history is essential. On the Gove and Mitchell Plateaux therefore, the adverse effects of land emergence and ensuing planation are counteracted by associated mild synclinal warping, so that the deposits constituted coastal hinge zones of at least two successive land (erosion) cycles. Nevertheless, following the main Cretaceous and Tertiary period of bauxitisation by leaching, the deposits were partially submerged by the sea and, particularly at Mitchell Plateau, extensively reworked. Assisted by quantitative heavy mineral studies distinct unconformities within several bauxite profiles can be established. Finally, the quantitative mineralogy of both deposits is discussed in some detail and an origin (supported by experimental studies) proposed.

Mineralogy, geochemistry, and fluid action process of uranium deposits in the Zhiluo Formation, Ordos Basin, China

-Some kaolin deposits representing the primary and secondary deposits from Malaysia were analyzes for their mineralogical composition to examine the effect of source rock on the mineralogy of the primary kaolin deposits and to compare the nature and mineralogy of the secondary with the primary deposits. The clay minerals of the primary deposits from the Ipoh and Sarawak areas that formed by the weathering of granites and diorites respectively are dominated by kaolinite, while the primary deposit from the Bidor area that formed as a result of weathering of schist is composed of a mixture of kaolinite, muscovite, and smectite. Assuming that the primary deposits in these areas were formed under the same paleoclimatic conditions, the variations in the mineralogy of these deposits reflect mainly the compositions of primary source rocks. Predominance of kaolinite in the Ipoh and Sarawak deposits is due to the relative abundance of feldspar minerals (more Al) in the granite and diorite source rocks in these two areas. On the other hand, occurrence of smectite and muscovite in the primary kaolin deposits from Bidor area reflect the mineralogical composition of the parent rock in this area, which is mica-schist. Abundance of illite in the secondary kaolin deposits from the Mersing area suggests a marine depositional setting of these deposits where illlite formed due to the K uptake by clay minerals from the seawater. The less quartz (sand fraction) and more clay minerals (silt and clay fractions) in the secondary kaolin deposits are due to the relative enrichments of the fine fractions during the transportation of these deposits from the source to the depositional site.

The present study deals with the isolation and characterization of the moderately halophilic-alkaliphilic bacteria from a saline habitat in western India. Eight different bacterial strains were isolated using enrichment techniques at 20% (w/v) NaCl and pH 10. The isolates exhibited diversity towards gram's reaction, colony and cell morphology. They were able to grow and produce alkaline protease over a broad range of NaCl, 5-20% (w/v) and pH, 8-10. None of the isolates could grow at pH 7, and one could not grow even at pH 8. Crude and partially purified proteases from strain S5 were subjected to characterization with reference to pH, salt stability and protein folding. Optimum protease activity and stability was recorded at 10% salt and pH 9-9.5. Denaturation kinetics of S5 alkaline protease along with a reference protease was studied at 8M urea followed by renaturation. The S5 alkaline protease could be partially renatured up to 32% of the original activity. Despite of the fact that all the 8 isolates were from the same site, they displayed significant diversity with respect to their salt requirement for growth and enzyme secretion. While the effect of pH was less demarcated on growth, the protease production was significantly affected. Isolate S5 produced substantial amount of halotolerant and alkaline protease. The activity and stability of the alkaline protease in a broader range of pH and salt would definitely make this enzyme an important candidate for various industrial applications.

Mineralogy and genesis of secondary uranium deposits, Um Ara area, south eastern desert, Egypt

Cites recent evidence from investigations of the geochemistry and mineralogy of platinum-bearing deposits in Siberia and South Africa which indicates that platinum-group metals are not necessarily products of early crystallization from basic magmas, but in some cases may have been deposited at much lower temperatures than was formerly considered possible.In addition, processes other than simple crystallization differentiation of sulfide and silicate melts may have been involved.

The Kolar schist belt, one of the auriferous Archean schist belts in the Dharwar craton, includes two types of gold deposits: (1) a stratiform sulfide type, associated with amphibolites and banded ferruginous quartzite, and (2) a gold quartz-carbonate vein type associated with light rare earth element (LREE)-enriched komatiitic and tholeiitic amphibolites on the eastern part of the belt. Many lodes of the former are banded and show deformation similar to that of their host rocks. The latter type consists of veins localized within shear zones. Both types have only a few inches of altered border rock characterized dominantly by biotite with minor diopside and garnet.The sulfide lodes contain 5 to 30 vol percent sulfides which include dominantly pyrrhotite and arsenopyrite. The lodes also contain variable amounts of magnetite and ilmenite. No systematic variation in ore minerals is discernible among the lodes of the entire belt. However, in the Kolar gold fields area, a set of four parallel sulfide lodes exhibit certain textural and mineralogical zoning. Ore minerals show metamorphic equilibrium textures and the temperature of final equilibration of sulfides is 500 degrees C or higher.Sulfide lodes have low but variable abundances of base metals. No correlation among total sulfide contents, sulfide minerals, and abundances of base metals and gold is observed. Nor is there any geochemical coherence between gold and arsenopyrite in the several lodes studied. Major oxides, particularly Al 2 O 3 , TiO 2 , and K 2 O also show a large variation. The REE abundances of the sulfide lodes vary widely, but their patterns are similar, with enrichment in both light REE and heavy REE. Normalized Eu shows strong to negligible enrichment. The REE patterns are similar to those of the banded ferruginous quartzite or iron-formation. Samples with high REE abundances also have high base metals, Al 2 O 3 , TiO 2 , and K 2 O abundances and low arsenopyrite contents. Based on these observations and limited Nd and O isotope data it is suggested that the sulfide lodes were originally auriferous, complex interflow sediments formed from submarine hydrothermal exhalations, seawater, and detrital sediments.The vein-type mineralization has only trace amounts of sulfides with galena as the dominant phase (Narayanaswami et al., 1960). The veins consist dominantly of quartz with minor amounts of calcite and alkali feldspar and trace amounts of scheelite and tourmaline. The gold content of the veins is generally > 10 ppm. The veins are also unusually enriched in Cr and Ni. These observations and the fluid inclusion studies on vein quartz (Santosh, 1986) suggest the presence of CO 2 -bearing ore fluids.One sample of the ore vein has a strongly fractionated, light REE-enriched pattern with an epsilon Nd value of +2.8 at 2,600 Ma. Galena from the ore samples have Pb isotope ratios, reported by Venkatasubramanian et al. (1977) and Chernyshev et al. (1980), that are similar to those of the 2,600-Ma intrusive granodioritic gneisses present on the west side of the schist belt (Krogstad et al., 1989). The delta 18 O of vein quartz is 11.6 + or - 0.7 per mil (Golding, 1982). These geochemical data suggest that the gold quartz veins were formed dominantly from magmatic fluids derived from the crystallization of granitic rocks. A contribution from metamorphic fluids is also conceivable as indicated by the abundance of Ni and Cr in the veins.

In the Poturge (Malatya, Turkey) area pyrophyllite occurrences are common in the shear zones, mostly in the form of lenses along faults. Mineralogical investigations (XRD, FTIR and SEM) revealed that pyrophyllite, kaolinite (dickite) and quartz are present in the form of major phases and muscovite (sericite), kyanite, chlorite, and alunite are only present in the form of minor phases.

Geochemistry, mineralogy and genesis of pyrophyllite deposits in the Pötürge region (Malatya, Eastern Turkey)

Alteration in the subaqueous basaltic rock of the Lam Narai volcanic belts, Lop Buri province, central Thailand has resulted in the formation of bentonite deposits. The bentonite deposits have been geological, mineralogical and geochemical studied to determine their genesis. The characteristics of the bentonites were examined by using X-ray Diffractometer and Scanning Electron Microscope with Energy Dispersive Spectroscopy. The mineralization zone of bentonite shown X-ray diffraction patterns of montmorillonite as the major constituent with minor hematite and calcite. Morphology of the minerals and groundmass in the bentonite deposits display the “cornflake,” “oak leaf,” or “cellular” textures that are typical and representative of montmorillonite in smectite group and composed of Si, Al, O, Ca, Mg and Fe in their chemical compositions. Geochemistry of the bentonite and their parental volcanic associations were analyses by using X-ray Fluorescence Spectrometry for major and trace elements. The representative samples were selected for the analysis of the rare-earth elements by using Inductively Coupled Plasma-Mass Spectrometry. The AI–CCPI alteration box plot revealed that the bentonite is mainly altered by hydrothermal alteration associated with basaltic layer in the Lam Narai volcanic belt. The basaltic layers in this area are composed of pillow lavas, inter-pillow and basic glassy inter-pillow (hyaloclastite) that indicated the subaqueous environment. The smectite formed by hydrothermal alteration from altered basic glassy inter-pillow (hyaloclastite) in the basaltic layers. Hydrothermal fluids in this area are possibly derived from the major fault along Pa Sak River or the youngest intrusive rocks in the Lam Narai volcanic terrain.

Mineralogy, technological properties, and industrial application of kaolin deposits at Nivasht and Kabudkamar areas, northwest of Saveh, Central Province

The demand for kaolinitic clays for various industrial applications is increasing globally. The present study evaluated the potential industrial applications of kaolins from the Eastern Dahomey and Niger Delta Basins, Nigeria. The colour, pH, electrical conductivity (EC), particle size distribution (PSD), plastic limits and liquid limits of the kaolins were determined. Mineralogical properties were assessed using X-ray diffractometry (XRD), scanning electron microscopy (SEM), and differential thermal analysis (DTA). The chemical compositions of the kaolins were determined using X-ray fluorescence spectrometry (XRF). The kaolins were generally acidic, with pH less than 7 with low EC. The moderate plasticity indices (PI ≥ 10%) for the kaolins suggested their potential use in the manufacturing of structural clay products without extrusion. Kaolinite was the only kaolin mineral present with anhedral–subhedral–euhedral crystals. The platy morphology of the kaolinites in the Cretaceous kaolins are very important in paper production. Other minerals present in the kaolins were quartz, muscovite, anatase and goethite. The major oxide contents of the kaolins were dominated by SiO2, Al2O3, Fe2O3 and TiO2. Based on chemical specifications, the raw kaolins are not suitable for most industrial applications except for the Cretaceous Lakiri kaolins in the paper and ceramic industries (except for TiO2 and K2O content). The study concluded that the kaolin deposits would require beneficiation for large-scale industrial applications.