Semi-quantitative X-ray Diffraction Analysis Research Articles

Lowering of the kinetic barrier of clay-mineral reactions along a seismogenic fault: Example from the Nankai subduction zone, Japan

An analysis of clay minerals in core samples around the megasplay fault of the Nankai Trough, Japan, recovered during the Integrated Ocean Drilling Program Nankai Trough Seismogenic Zone Experiment reveals a local progression of the smectite-to-illite conversion (S–I) reaction in the slip zone, possibly associated with local thermogenesis caused by seismic slip on the fault. Our semiquantitative X-ray diffraction analysis demonstrates that the illite content in mixed-layer illite/smectite is ∼15% higher in the gouge than in the host sediments. The thermal history of the fault, constrained in a previous study, requires a reduction of the apparent activation energy by 20–30% compared with the literature value to explain the observed illitization. The Shirako Fault in the Miura–Boso accretionary complex, which is thought to have been activated in a tectonic setting similar to that of the megasplay fault of the Nankai Trough, also shows a 20–30% reduction in the apparent activation energy. These results suggest that the kinetic barrier of the smectite–illite reaction is lowered as a result of mechanochemical processes in seismogenic fault zones.

The starting stoichiometry, keys parameter to enhance the intrinsic microstructural and functional properties of synthesized hybrid nanocomposites chitosan/Na-montmorillonite/ZnO nanoparticlest type

To improve the intrinsic qualities of hybrid nanocomposite (NC), polymer, clay, and metallic oxide are combined. This study investigates the effects of starting stoichiometry variation on the microstructural and functional properties of synthesized hybrid NC composed of chitosan (CTS), Na-montmorillonite (MMT), and ZnO nanoparticles (NPs). To carry out the synthesized process, a solution blending approach is used. A correlation of the outcomes from the several analyses methods such as X-ray diffraction (XRD), Fourier Transform InfraRed spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Impedance spectroscopy (IS), and UV–VIS spectrophotometry ensures the accuracy of the analysis. Regardless of the initial stoichiometry rate, the microstructural analysis shows that NC can be successfully synthesized. The growth and changes in the intensity and sharpness of the characteristic reflections shown by the semiquantitative XRD analysis suggest that the synthesis process was certainly successful. The apparent structure aberration, caused by the stoichiometry fluctuation, is manifested as an XRD reflection position shift and varied intensity strength.The intercalation process and the exfoliation of "clay-particles" enclosing the organic fraction, according to TEM/EDX experiments, occurred as the clayey fraction's abundance surged. Despite the variable ratio approved at the start of the synthesis process, FTIR spectroscopy displays the polymer fraction's characteristic absorption bands. Synthesized NC has significant UV blocking properties while retaining good transparency in the visible range. This behavior may have its roots throughout the fact that the CS surface modification has induced the bandgap energy fluctuation of ZnO NPs. The photocatalytic activity of the produced NC is evaluated using MB degradation measurements. The outcomes are extremely positive for the sample with a starting stoichiometry almost equally distributed between CTS and ZnO (NPs). Results from the IS, for the selected sample, shows that synthesized NC exhibits semiconductor behavior,and as a dielectric material, the sample is dispersive with a power loss over a specific frequency range.

Fabrication of Ni, Si and Mg Supersaturated Solid Solutions in Al by Mechanical Alloying

In this work, a comparison between the synthesis process of nanostructured Al base alloys modified with Si, Ni and Mg and the formation of their respective supersaturated solid solution is presented. The samples were obtained via Mechanical Alloying (MA) at a speed of 300 RPM for 2, 5, 10, 20 and 30 h under an inert Ar atmosphere. Lattice parameter evolution, semiquantitative X-Ray Diffraction Analysis and SEM micrographs were correlated to determine the attained solubility in the Al matrix. The results showed that powder refinement and solubility rates are directly affected by the hardness of the solute element and the limiting solubility in equilibrium state respectively. Therefore the Al-Mg alloy achieved the highest solubility of the samples after 10 h of milling, meanwhile, the Al-Si alloy showed the lowest solubility even after 20 h of milling. Microstructural analyses by X-Ray Diffraction revealed that the lattice parameter showed different behavior depending on the alloy system, in some cases showing a deviation from the behavior predicted by Vegard's law. Finally, this work demonstrates that the successful synthesis of supersaturated solid solutions via MA is dependent on the alloy system as well as milling conditions.

주성분분석법을 활용한 황해 남동 이질대 퇴적물의 기원지 연구

황해 남동 이질대에서 채취된 51개의 표층퇴적물 시료와 황해로 유입되는 한국과 중국의 하천퇴적물 시료 33개에 대해서 반정량 X선회절분석법을 통한 점토광물의 상대적인 함량을 토대로 주성분분석을 도입하여 해양표층퇴적물의 기원지를 연구하였다. 전체 자료의 98% 이상을 반영하는 제1주 성분과 제2주성분을 이용하여 R 프로그램을 통해 주성분분석을 수행하였다. 황해 남동 이질대 퇴적물의 점토광물 함량은 남부 지역과 북부 지역에서 거의 차이가 나지 않으며, 성분도표상에서의 해양퇴적물 분포는 중국의 황하, 양쯔강 퇴적물보다 한국의 하천퇴적물과 더욱 근접한 양상을 보였다. 이러한 통계적 분석 결과를 바탕으로 황해 남동 이질대는 거의 모두가 한국 하천퇴적물로부터 유래했다는 것을 추정할 수 있다. 또한, 황해 남동 이질대에 한국 하천에서 유출되는 양보다 더 많은 퇴적물이 축적된 이유로는 퇴적물의 침식과 재동에 의한 것으로 판단된다. 주성분분석은 한반도 주변 해역 퇴적물의 기원지 연구에 유용하게 사용될 것으로 기대된다. In this study, we tried to determine the origin of fine-grained sediments in Southeastern Yellow Sea Mud patch (SEYSM) using principal component analysis coupled with semi-quantitative X-ray diffraction analysis for 4 major clay minerals. We used 51 marine surface sediments from SEYSM and 33 surface sediments of rivers flowing into the Yellow Sea. We made bioplot diagram using R program with principal component 1 and component 2 because the two components might contain about 98% of all data. The content of each clay mineral in the south and north regions of SEYSM are almost similar. In the biplot, SEYSM sediments distribute close to Korean rivers sediments than Huanghe and Changjiang sediments. Based on these results, we suggest that SEYSM is originated from the Korean rivers sediments. The higher accumulation rate in the SEYSM compared to the sediment discharge from neighboring Korean rivers can be explained by erosion and reworking of surface sediments in this area. The principal component analysis can be used for the provenance research of marine sediments around the Korean Peninsula.

통계적 주성분분석법을 활용한 제주 남서 이질대 퇴적물의 기원지 연구

제주 남서 이질대에서 채취된 138개의 해양표층퇴적물 시료와 황하와 양쯔강 하천퇴적물 시료에 대하여 반정량 X선회절분석법에 의한 점토광물 상대조성을 바탕으로 주성분분석을 이용하여 퇴적물의 기원지를 연구하였다. 제1주성분과 제2주성분이 전체 자료의 90% 이상을 설명하기 때문에 두 주성분만을 가지고 R프로그램을 이용하여 주성분분석을 실시하였다. 제주 남서 이질대 내 각각의 점토광물의 분포양상은 매우 복잡하지만, 전체적인 분포양상을 고려할 때, 스멕타이트와 카올리나이트는 서부지역에서 높은 함량을 보였고 일라이트와 녹니석은 동부지역에서 상대적으로 높은 값을 나타냈다. 제주 남서 이질대의 동부지역에서 보여주는 상대적으로 높은 일라이트와 녹니석 함량은 양쯔강 퇴적물과, 서부지역에서의 높은 스멕타이트와 카올리나이트 함량은 황하 퇴적물과 더 유사한 양상을 나타낸다. 이러한 통계 처리 결과를 바탕으로 제주 남서 이질대의 동부지역은 양쯔강에서 유래하였고 서부지역은 황하로부터 기원했음을 추정할 수 있다. 추후 퇴적물 기원지 연구에 주성분분석이 유용하게 활용될 것으로 기대한다. In this study, we tried to define the origin of fine-grained sediments in Southwestern Cheju Island Mud (SWCIM) using principal component analysis. We used relative clay mineral compositions using 138 marine surface sediments, 4 Huanghe sediments and 3 Changjiang river sediments by the semi-quantitative X-ray diffraction analysis. We made bioplot diagram using R program with principal component 1 and component 2 because they might contain more than 90% of all data. Although the distribution pattern of each clay minerals in SWCIM is so intricate, smectite and kaolinite contents are high in the west region, but illite and chlorite contents are rich in the east region. In the biplot, the east region of SWCIM distribute around Changjiang river, whereas west region of SWCIM disperse around Huanghe. Our results might reveal that west region of SWCIM is mainly originated by Huanghe, but east region of SWCIM by Changjiang River.

Authigenic, detrital and diagenetic minerals in the Laguna Potrok Aike sediment sequence

The ∼100 m-long Laguna Potrok Aike sediment sequence yielded a record spanning the Last Glacial period to the Holocene. This paper presents and discusses two aspects of the mineralogy of the lake. The first aspect is based on a semi-quantitative X-ray diffraction analysis of bulk and clay mineralogical assemblages. Minor mineralogical changes are observed throughout the glacial section suggesting relatively uniform sediment sources. The transition into the Holocene is characterized by increasing fluxes of endogenic calcite thought to relate to lower lake levels. The second aspect is based on analysis of uranium-series disequilibria in diagenetic vivianite from the glacial section. U-series ages were expected to yield minimum ages for the host-sediment. Unfortunately, very little authigenic U is present in vivianite grains. The low primary productivity of the lake and thus low organic carbon fluxes might have prevented the development of strong redox gradients at the water-sediment interface and thus reduced diagenetic U-uptake into the sediment. One vivianite sample, at a 56.9 m composite depth, yielded enough authigenic uranium to calculate a 230Th-age of 29.4 ± 5.9 ka (±2σ). This age is younger than the one indicated by the radiocarbon chronology. It is thus concluded that a relatively late diagenetic evolution of the U–Th system characterizes the recovered vivianite minerals. The authigenic U displays a very high excess in 234U (over 238U) with an activity ratio of 4.58 ± 0.58 (±2σ). It suggests that it originates from the transfer of highly fractionated U from surrounding detrital minerals through very low U-content pore waters.

황해 남동 이질대 퇴적물의 점토광물분포 및 특성

황해 남동 이질대 51정점(북부 25정점, 남부 25정점)에서 채취된 표층퇴적물과 황해로 유입되는 하천퇴적물 30정점에 대해서 반정량 X선회절분석법에 의하여 점토광물의 상대조성을 구하였으며 일라이트의 광물학적 특성에 대해서도 조사하였다. 점토광물 조성은 일라이트(61~75%), 녹니석(14~24%), 카올리나이트(9~14%), 스멕타이트(1~7%) 순으로 존재한다. 황해 남동 이질대의 북부 지역에서 카올리나이트 함량이 약간 높고, 스멕타이트 함량이 낮은 점을 제외하면, 북부와 남부 지역에서 점토광물 조성은 특별한 차이가 없다. 스멕타이트 함량은 일라이트 함량과 대체적으로 음의 상관관계를 가진다. 일라이트의 광물학적 특징들인 일라이트 결정도(0.18~0.24 <TEX>${\Delta}^{\circ}2{\theta}$</TEX>) 역시 북부와 남부 사이에 차이가 없으며, 매우 좁은 범위 내에 속한다. 이번 연구 결과는 황해 남동 이질대의 북부와 남부 퇴적물은 점토광물조성과 일라이트 특성이 거의 유사함을 지시한다. 황해 남동 이질대 퇴적물은 중국의 황하퇴적물보다 한국의 하천퇴적물과 유사한 특성을 가지지만, 추후 양쯔강 퇴적물을 포함한 조사가 필요할 것으로 판단된다. 점토광물 조성으로부터 황해 남동 이질대 퇴적물은 한국 서해안으로 유입되는 하천으로부터 매우 많은 양이 유래한 것으로 판단된다. 황해 남동 이질대의 매우 많은 퇴적물 공급량과 높은 퇴적 속도는 퇴적물들의 침식과 재동에 의한 것으로 간주된다. 황해 남동 이질대 주변의 조류와 지역적인 해류가 이 지역의 침식과 퇴적 과정에 중요한 영향을 미친 것으로 판단된다. In this study, we determined the relative clay mineral composition of 51 surface sediments from SEYSM (Southeastern Yellow Sea Mud) (northern part 25, southern part 26) and 30 river sediments inflow to Yellow Sea using the semi-quantitative X-ray diffraction analyses. In addition to we analyzed illite characteristics of the same samples. The clay-mineral assemblage is composed of illite (61~75%), chlorite (14~24%), kaolinite (9~14%), and smectite (1~7%), in decreasing order. The average composition of each clay mineral is not different from northern part to southern part of SEYSM except a little higher kaolinite and lower smectite content in northern part. Smectite content generally has reverse relationship with illite content. Mineralogical characteristics of illite such as illite crystallinity index also is not different between two areas and show very narrow range (0.18~0.24 <TEX>${\Delta}^{\circ}2{\theta}$</TEX>). Our results reveal that clay mineral composition and illite characteristics are nearly the same between northern and southern part of SEYSM. Characteristics of surface sediments in SEYSM is closer to Korean river sediments than Chinese Hanghe sediments, however it is necessary to investigate further study including Yangtze river sediments. This study conclude that most of surface sediments in SEYSM attribute to the supply of considerable amount of sediments from the nearby Korean rivers. The large sediment budget and high accumulation rate in the SEYSM can be explained by erosion and reworking of surface sediments in this area. Tidal and regional current system around SEYSM might contribute these erosional and depositional regimes.

Analysis of Mineralogical Component of Palm Oil Fuel Ash with or without Unburned Carbon

The purpose of this paper is to investigate the mineralogical components of palm oil fuel ash (POFA) with or without unburned carbon by using semi-quantitative X-ray diffraction (XRD). Original POFA taken from palm oil mill was ground in ball mill, producing ground POFA (GPOFA). Unburned carbon was removed by heating the GPOFA at 500 °C for 1 h, producing treated POFA (TPOFA). Neither glassy phase crystallization nor agglomeration of GPOFA particles occurred during the heat treatment. The content of crystalline phase and glassy phase in GPOFA or TPOFA was determined using semi-quantitative XRD analysis internal standard method. The results showed that GPOFA and TPOFA contained 67.22% and 73.89% of glassy phase, respectively, which could be used as pozzolanic materials. The presence of P2O5, K2O and Na2O in POFA was the reason of reducing the melting point of POFA in boiler.

Effect of NaOH on the vitrification process of waste Ni–Cr sludge

This study investigated the effect of NaOH on the vitrification of electroplating sludge. Ni, the major metal in the electroplating sludge, is the target for recovery in the vitrification. Sludge and encapsulation materials (dolomite, limestone, and cullet) were mixed and various amounts of NaOH were added to serve as a glass modifier and a flux. A vitrification process at 1450 °C separated the molten specimens into slag and ingot. The composition, crystalline characteristics, and leaching characteristics of samples were measured. The results indicate that the recovery of Ni is optimal with a 10% NaOH mass ratio; the recoveries of Fe, Cr, Zn, Cu, and Mn all exhibited similar trends. The results of the toxicity characteristic leaching procedure (TCLP) show that leaching characteristics of the slag meet the requirements of regulation in Taiwan. In addition, a semi-quantitative X-ray diffraction analysis revealed that the main crystalline phase of slag changed from Ca 3(Si 3O 9) to Na 4Ca 4(Si 6O 18) with a NaOH mass ratio of over 15%, because the Ca 2+ ions were replaced with Na + ions during the vitrification process. Na 4Ca 4(Si 6O 18), a complex mineral which hinders the mobility of metals, accounts for the decrease of metal recovery.

Comparative study of microwave and conventional processing of MgAl 2O 4-based materials

A comparative study of microwave and conventional processing of ceramic materials based on MgAl 2O 4 is presented in this paper, in particular sinters obtained from MgO and Al 2O 3 with 1 wt.% of CaO as an additive, and Al 2O 3–MgAl 2O 4 composites. Microwave processing took place under air at 800 W and 2.45 GHz during 4.5 min, conventional processing in an electrical resistance furnace, also on air, was conducted at 1400 °C for 96 h. The MgO:Al 2O 3 weight ratio employed for the synthesis of MgAl 2O 4 was 1:2.45. According to semi-quantitative X-ray diffraction analysis, approximately 90% of MgAl 2O 4 was produced with both processing methods. Scanning electron microscope (SEM) images of the microstructure revealed a similar morphology for the two methods, nevertheless the grain size was different. The Al 2O 3:MgAl 2O 4 weight ratios for the production of the composites were 9:1, 1:1, and 1:9 using the two methods and the conditions already described. A heterogeneous microstructure was observed in the specimen processed by microwaves. Due to the different nature of the processes, an extensive property was compared against an intensive one, therefore, the aim of this work was to have a realistic comparison between the materials obtained with these processes by taking into account energetic as well as kinetic aspects.

Semiquantitative XRD analysis with the aid of reference intensity ratio estimates

Estimation of reference intensity ratios (ki or RIR) can be made on the basis of an atomic scattering function. Tests of regression equations for 50 compounds that predict an approximate reference intensity ratio from the easily computed scattering function have shown usefulness in multicomponent semiquantitative X-ray diffraction analysis. The method is best applied whenever only one or two minor components of a multicomponent sample have no readily measurable or calculable ki values and must be estimated. Where the difference between observed and predicted constants is large, these tests show that the ratios of true- to test-weight fractions are proportional to the corresponding ki ratios. The largest absolute errors occur whenever the ki must be predicted for components with medium weight fraction values. Estimation of ki for components of less than 10 weight percent results in only small errors in both predicted component and the other components of the sample. Where more than two components require predicted ki in a given sample, unacceptable errors for all components may result.

Diagenesis of mudrocks from the Kimmeridge Clay Formation of the Brae Area, UK North Sea

Kimmeridge Clay Formation mudrocks from two boreholes in the Brae Area on the western edge of the Viking Graben, North Sea, have been examined using X-ray diffraction (XRD) and backscatter electron microscopy techniques (BSEM). The Lower Cretaceous-Upper Jurassic samples from the Central Brae well were more carbonate-rich than the Upper Jurassic samples from the North Brae well. Semi-quantitative XRD analyses show that there are also significant differences in the clay mineral assemblages of the mudrocks from the two wells. Smectite-rich random mixed-layer illite-smectites are present in the Central Brae well whereas the slightly deeper samples from the North Brae well have illite-rich regular mixed-layer illite-smectites. These differences are considered to reflect differences in the detrital input into the two areas rather than being predominantly the result of illitization reactions during burial diagenesis. The BSEM data provide detailed information on the petrofabrics of the mudrocks and illustrate their complexity and heterogeneity. The mudrocks have undergone a complex diagenetic history involving the formation and dissolution of clay and non-clay phases. These include an early localized carbonate cementation of microfossil tests with later partial dissolution and infilling by clay and non-clay diagenetic phases (e.g. microcrystalline quartz, chlorite, illite, illite-smectite, kaolinite, pyrite). Authigenic illite, illite-smectite and kaolinite are also found in the ‘matrix’ of the mudrocks. The feldspars, and to a lesser extent the quartz grains, show evidence of corrosion. The mudrocks have undergone multiphase diagenesis in a complex association of microenvironments. Processes of dissolution and neoformation have occurred as the detrital phases responded to the changing physico-chemical environment.

Semi-quantitative X-ray diffraction analysis of size fractionated atmospheric particles

Semi-quantitative X-ray diffraction analysis of size fractionated atmospheric particles

Semi-quantitative x-ray diffraction analysis of size fractionated atmospheric particles

We describe the development of a simple standardization technique for the x-ray diffraction (XRD) analysis of atmospheric particulate matter, using aluminium oxide as an internal standard. Accuracy and precision were better than ± 25% for nearly all the typical atmospheric crystalline compounds studied. Good agreement was found with elemental analyses. Detection limits were around 40–75 μg, depending on the compound, for scan times of about 1-h. This represents a considerable improvement in speed of analysis over previous studies. The suitability of various filters for XRD analysis was assessed. Efforts were made to minimize potential sample modification during and after sampling, and tests made to examine hydration effects. The representativity of the collected samples to actual atmospheric conditions is discussed. The technique was applied to size-fractionated atmospheric samples collected in suburban Toronto, Canada. Around half the collected mass was XRD identifiable, of which about half evidently originated from blown dust (soil, building materials, road salt, etc.) with the remainder comprising some eight pollution derived compounds of NH 4 +, SO 4 2−, NO 3 −, Cl − and Pb. The distribution of the major ions between different compounds was determined. XRD identifiable lead was related to total Pb concentrations. We conclude by considering our results in a wider context by examining the similarities and discrepancies between other related studies worldwide.

Semi-quantitative X-ray diffraction analysis of size fractionated atmospheric particles

Semi-quantitative X-ray diffraction analysis of size fractionated atmospheric particles

Evolution of Lime and Microstructural Development In Fly Ash-Portland Cement Systems

AbstractThe evolution and distribution of calcium hydroxide, CH, and the development of microstructure during the hydration of three low-calcium fly ash-Portland cement blends with water-solids ratio (w/s) of 0.40 have been investigated. During the first month of hydration, the CH content of the blends was found to be relatively higher than the plain mix, if a dilution effect due to replacement of cement by an inert material is taken into account. After 28 days of hydration the CH content in the blends began to decrease. SEM observations of specimens revealed the occurrence of large, well-crystallized CH plates in intimate contact with some of the fly ash particles at younger ages and even after six months of aging. The study also showed that the chemistry of the pore solution in contact with the hydrating cement system and the characteristics of the fly ashes, such as the glass content and the fineness of the ash particles seem to exert major influences on the rate of evolution of CH in the fly ash blends. Semi-quantitative X-ray diffraction analyses performed on specimens cast against polypropylene plastic plates used to “model coarse aggregates” showed reduction in the thickness of the interfacial zone for the fly ash-Portland cement pastes from about 60μm to less than 15μm within one month of hydration. In the case of the plain Portland cement paste no significant change was observed. The degree of orientation of CH crystals within the interfacial region also was significantly affected by the fly ashes, although by this age of hydration the CH data showed little or no evidence of pozzolanic reaction.

Quantitative X-ray diffraction analysis of urinary calculi by use of the internal-standard method and reference intensity ratios.

The internal-standard method and the powder diffractometer have been applied here to the quantitative determination of urinary stone constituents by x-ray diffraction (XRD). Reference intensity ratios determined for six stone substances were used in the reduction of intensity data. Constituent concentrations calculated for 21 stones were compared with values obtained from an element-sensitive technique. We conclude that XRD analysis alone cannot be regarded as a routine technique for the quantitative characterization of uroliths, but that semiquantitative XRD analysis supplemented by accurate quantitative elemental data is more suitable for the precise determination of true stone composition.

Semi-Quantitative X-Ray Diffraction Analysis of Fly Ash by the Reference Intensity Ratio Method

ABSTRACTA protocol for relatively inexpensive and rapid semi-quantitative x-ray diffraction analysis of fly ash mineralogy by the Reference Intensity Ratio (RIR) method is described. RIR's for the common crystalline phases in fly ashes derived from low rank and bituminous coal are given. The method is semi-quantitative for some phases because of unavoidable overlaps of the stronger peaks suitable for quantitation. Use of the protocol is illustrated with the four fly ash Standard Reference Materials supplied by the National Institute of Standards and Technology. Recommendations for implementation of this protocol in other laboratories and for improvements in quantitation of fly ash mineralogy are given.

Depositional environment and facies relationships of the Cretaceous ironstone of the Agbaja Plateau, Nigeria

The Maastrichtian oolitic ironstone examined caps the mesas of the Agbaja Plateau, which covers an area approximately 150 km 2 and is situated NW of Lokoja, near the confluence of the Benue and Niger rivers, in the Cretaceous Middle Niger Basin of Nigeria. This basin is one of six depositional (Mesozoic to Recent) basins in Nigeria and is a shallow trough filled with Campanian to Maastrichtian, marine to fluviatile strata on the Pre-Cambrian basement. Four major lithofacies of ironstone may be discerned on the basis of semi-quantitative X-ray diffraction analyses of borehole samples. These are from oxidized to more dehydrated and reduced conditions: (1) goethite + kaolinite; (2) hematite + geothite + kaolinite; (3) maghemite/magnetite + goethite + kaolinite; (4) siderite + magnetite + kaolinite. The maghemite/magnetite + geothite + kaolinite facies is dominant. The ironstone was deposited during a major transgression. It overlies either a carbonaceous mudstone/shale or clay/sandstone, which is underlain by a fluviatile sandstone. Primary oxidized ironstone minerals were formed in nearshore fluviatile environment, and transported into deeper water. Through re-working and diagenesis, ironstone deposition continued under estuarine and reducing conditions with evidence of low energy wave action at the top of the ironstone.

Clays and Clay Minerals of the Santa Ana River Drainage Basin, California

ABSTRACT Semiquantitative X-ray diffraction analysis was performed on the clay fraction (<2 µm) of riverbed samples from the Santa Ana River Drainage Basin, California. Bedrock sources were also analyzed. Results show that addition from older sedimentary deposits is more important to riverbed composition than is weathering in transit. Major minerals in the riverbed are montmorillonite, mica, plagioclase, K-feldspar and quartz. Present in lesser amounts are kaolinite, chlorite, calcite, amphibole and gypsum. These minerals are all present in the bedrock samples, in highly variable amounts. The composition of the coastal riverbed sediments is similar to that of marine sediments near the mouth of the river, possibly indicating recent marine transgressions in the coastal area.