Average Mineral Composition Research Articles

Karakteristik Dan Petrogenesa Batuan Beku Granit Di Daerah Sibayu, Kecamatan Balaesang, Kabupaten Donggala, Provinsi Sulawesi Tengah

The tectonic history of Sulawesi is closely related to the activities of the three major world plates that surround it. This results in the complexity of geological conditions on the island of Sulawesi, including the diversity of rock types. One of the most common types of rock is igneous granite, which is widespread in the Sibayu area, Donggala Regency, Central Sulawesi Province. This study aims to determine the characteristics and petrogenesis of igneous granite using megascopic and microscopic or petrographic observation methods. The results showed that the rock has a megascopic appearance in the form of a grayish-white fresh color and a brownish weathered color, a holocrystalline texture, a massive structure, and a mineral composition consisting of orthoclase, amphibole, and quartz. Its microscopic appearance shows a brownish-transparent color on parallel nikol, on brown cross-linked nikol, light gray to dark gray, mineral size 0.15-0.05 mm, the average mineral composition is orthoclase (41.25% ), quartz (43.75%), biotite (11.25%) and plagioclase (3.75%). Based on these data, it can be concluded that the rocks are Late Miocene to Late Pliocene, which proves that the Palu-Koro fault was still active during the Late Miocene to Late Pliocene. The presence of biotite in granitic rocks characterizes S-Type granite which is formed deep below the earth's surface which is characterized by euhedral-subhedral forms.

Major Characteristics of Surface Sediments Within the Shallow Water of the Cat Ba Island, North Vietnam

The Cat Ba is one of the largest Islands offshore North Vietnam, which is characterized by an abundance of coral reefs in the East and Southeast of the island. The surface sediments are considered the basic elements for the coral ecosystem development. In this study, the authors present some new results studying pH, Eh, mineral composition, and grain size as the basic information for environmental assessment of this area. The results show that the pH value of the surface sediment varies from 6.90 to 8.09, with an average of 7.24 while the Eh value of the sediment ranges from -121.10 to -48.20mV, an average of -68.39mV, demonstrating a reducing environment. The surface sediments have been classified into 8 size classes: the coarse silt > very coarse silt > medium sand, very fine sand > very coarse sand, fine sand > coarse sand, very fine gravel. Most of the sediments are poorly sorted - very poorly sorted, only a few sedimentary samples are well sorted, moderately sorted, and moderately well sorted. The average mineral composition of the surface sediments consists of: 25% quartz, 17% illite, 16% aragonite, 13% kaolinite, 10% calcite, 5% chlorite, 4% gothite, 3% halite, 2% feldspar and less montmorillonite, and dolomite. These results allowed the researcher to interpret that the sediments have been deposited in a relatively calm environment and the terrigenous sediment sources are dominant over the marine sources. Source marine sediment groups are characterized by coarse grains, high pH, and are rich in carbonate minerals, which have been produced by biological materials. In contrast, the terrigenous sediment group is dominated by fine-grained sediments, rich clay minerals, quartz, and gothite. These fine-grained sediments are commonly distributed in the area and are favorable places for pollutant accumulation.

Rock physics modelling for determination of effective elastic properties of the lower Paleozoic shale formation, North Poland

This paper presents an application of rock physics templates constructed with the use of the granular effective medium theory and the shale model to estimate the elastic properties of the Silurian and Ordovician shale formations from the Baltic Basic, Poland. The author uses available logging data from three nearby wells and their petrophysical interpretation to distinguish various lithologies and to determine average matrix mineral composition of each lithology group, essential in further rock physics modelling. Anisotropy estimation and investigation of the relation between various petrophysical parameters precede the rock physics modelling. The logging data cross-plotted in Vp/Vs ratio–acoustic impedance domain reveals distinct compaction trend for shales, which is not followed by shales with increased organic matter and calcareous deposits. These two lithology groups present own trends, which are related to increasing kerogen and carbonate minerals contents, respectively. The trends are the subject of rock physics modelling. Granular effective medium rock physics templates are constructed for each lithology group. The rock physics analyses reveal that the elastic properties of strongly compacted shales, including shales with organic matter, might be successfully described by the lower modified Hashin–Shtrikman bound, which is useful in compaction trend modelling. Marly deposits can be modelled in a similar way to shales. The upper modified Hashin–Shtrikman bound provides a better template for carbonates as it models the cementation process. The shale model provides independent rock physics template for shales. Comparison of these two approaches shows that the granular effective medium method better describes the elastic properties of the analysed formations. The paper includes also the proposition of the final rock physics template constructed for the Silurian and the Ordovician formation from the Baltic Basin that can contribute to a better understanding of the elastic properties of the lower Paleozoic shale plays in Poland.

Geology of the Chang 7 Member oil shale of the Yanchang Formation of the Ordos Basin in central north China

We present a review of the Chang 7 Member oil shale, which occurs in the middle–late Triassic Yanchang Formation of the Ordos Basin in central north China. The oil shale has a thickness of 28 m (average), an area of around 30 000 km 2 and a Ladinian age. It is mainly brown-black to black in colour with a laminar structure. It is characterized by average values of 18 wt% TOC (total organic carbon), 8 wt% oil yield, a 8.35 MJ kg −1 calorific value, 400 kg t −1 hydrocarbon productivity and kerogen of type I–II 1 , showing a medium quality. On average, it comprises 49% clay minerals, 29% quartz, 16% feldspar and some iron oxides, which is close to the average mineral composition of global shale. The total SiO 2 and Al 2 O 3 comprise 63.69 wt% of the whole rock, indicating a medium ash type. The Sr/Ba is 0.33, the V/Ni is 7.8, the U/Th is 4.8 and the FeO/Fe 2 O 3 is 0.5, indicating formation in a strongly reducing, freshwater or low-salinity sedimentary environment. Multilayered intermediate-acid tuff is developed in the basin, which may have promoted the formation of the oil shale. The Ordos Basin was formed during the northwards subduction of the Qinling oceanic plate during the Ladinian–Norian in a back-arc basin context. The oil shale of the Ordos Basin has a large potential for hydrocarbon generation. Supplementary material: Tables of oil-shale geochemical composition, proximate and organic matter analyses from the Chang 7 Member oil shale, the Ordos Basin, Central north China are available at https://doi.org/10.6084/m9.figshare.c.4411703

Contrast Characteristics of the Muscovitic Quartzite from Karelia, Russia - Determining the Possibility of Intensification of the Beneficiation Process

The use of muscovite is determined by its industrial look and quality. Sheet mica is traditionally used as electrically insulating material. Crushed mica dry or wet grinding and scrap (waste from the production of sheet mica) are used as electrical insulating material (for example, mica paper), filler in the manufacture of various kinds of fillers, grout and paint etc. In addition, today there is a steady demand for micronized muscovite for the production of decorative coatings and cosmetics.On the territory of the Republic of Karelia (Russian Federation) there is a significant number of deposits and occurrences moscoviticarum rocks. Promising target small iron-poor Muscovite is the manifestation of the Eastern Hitware identified in 1999. The average mineral composition of rocks of the productive series: quartz – 10-71%; Muscovite – 8-42%; plagioclase – 1,5-28%; kyanite – 2-13,5%; biotite, and 0.1-8%; ore (pyrite, sphalerite) and 1.5 – 11%.Enrichment of this type of mineral raw materials may be carried out using traditional methods – gravity, magnetic separation, flotation. Textural-structural and mineralogical features, a high degree of secondary changes (thin intergrowths of muscovite with graphite, ferritization, the decrease of the strength characteristics) and the availability of areas and dedicated silicification abundant pyrite mineralization and its vein type significantly impoverish muscovite ore, necessitate the adjustment of technological schemes and modes of enrichment. Possibilities of improvement of processes of pretreatment and subsequent enrichment is possible using the methods of pre-sorting that represent rational and cost-effective alternative to traditional beneficiation processes. To explore the possibility of using the optical methods being preconcentration, experimental study of the contrast of properties of samples of the original ore. The study was carried out on crushed material, graded by size: -10+5; -20+10; -40+20 -60 and+40 mm. the results revealed the main search area colour shades in images of mineral samples in the colour system HLS – grey, brown, bright yellow-orange and purple. The correlation between the colour characteristics of the individual pieces and the content of muscovite. To implement the sort method of photometric separation, the threshold separation can be determined by one of the highlighted areas of the gamut or in their entirety. Next, the sorted ore with the same mineralogical and structural properties can effectively be enriched with gravitational methods. In the complex process of enrichment, it is possible to obtain, in addition to muscovite, quartz and kyanite products, which undoubtedly will increase the output of marketable products.

The relationship between mineral content and acoustic velocity of sandstone reservoirs in Junggar basin

Sandstone reservoirs have generally high porosity in the Shawan formation of the Chunguang oil field, Junggar basin, because they developed in geological conditions of shallow and weak compaction. High porosity always links lower acoustic velocities in sandstone. However, when it is more than a certain value (approximately 27.5%), the porosity is not in accordance with acoustic velocities. In addition, cast thin sections illustrated incoherence between pore types and porosity. Fluids and mineral content are the two main factors changing acoustic velocities. This means that acoustic velocities of the high-porosity sandstone are mainly affected by the mineral content and fluid properties. Hence, data from litho-electric analysis are used to measure velocities of the compression shear waves, and thin sections are used to identify the mineral content. By the application of cross-plot maps, relations of acoustic velocities and mineral contents are proposed. Mineral contents include mainly quartz, feldspar, and tuff. In normal rock physical models, the shale content is calculated from well logs. The mineral grain is often regarded as pure quartz grain or average mineral composition. However, the application of the normal rock physics model will be inaccurate for high-porosity sandstone. Experience regression functions of the velocity model are established to estimate acoustic velocities. Also, mineral content logs could be predicted by using the P-wave acoustic log, and the rock physics model would be enhanced by using these logs of dynamic mineral contents. Shear wave velocity could also be estimated more accurately.

Viscosity predictions of the slag composition of gasified coal, utilizing FactSage equilibrium modelling

Agglomeration of ash particles provides the desired porosity of the ash bed for adequate agent (steam and oxygen) flow and distribution, whereas excessive slagging inside the gasifier can cause channel burning, pressure drop problems or unstable operation, resulting in cut backs on gasifier load, which implies a direct loss in gas production. The ash flow temperature (AFT) is one property that specifically gives more information on the suitability of a coal source for combustion or gasification purposes. However, normal AFT analyses give an average flow property and do not indicate exactly at what temperature the first melt/slag is occurring or what the properties of the slag is at a specific temperature. Operating experience indicates that even when the gasifiers are operated at temperatures above the flow temperature as given by AFT analysis, a low percentage of slag is formed. In this study, the focus will be on the application of viscosity determinations together with FactSage modelling. Conventional AFT analyses take the bulk chemical composition of the mineral phase into account, and does not differentiate between the composition in the slag–liquid phase and the composition of the crystalline phase. It is therefore important to describe the viscosity of not only the completely molten phase, but also the partly crystallised slag and liquid portion. The combination of viscosity predictions together with FactSage modelling will result in viscosity predictions of the actual liquid component, rather than just an average or pseudo-viscosity prediction of the total mineral system at a specific temperature. Based on the fact that the Urbain model assumes the composition as 100% liquid or molten, which is not the case for example during fixed bed gasification where the mineral structure is of a heterogeneous nature with partial melting and crystalline material, viscosity predictions of the slag or molten portion can be more accurately determined by using the FactSage results. The viscosities, as determined from specific slag compositions at specific temperatures between 1000 °C and 1250 °C, differ from the average viscosity prediction and is highly likely to be a more accurate prediction of the slag viscosity than just based on the average mineral composition. The viscosity of the actual slag composition also remains fairly constant up to temperatures >1200 °C. This can also be related back to the initial deformation temperature onset of the coal, where the slag properties are cumulative enough for the onset of deformation to start. The specific decrease of the viscosity at the temperature between 1200 °C and 1250 °C correlates with the slag formation trend as obtained with FactSage modelling. During the gasification process the viscosity of the slag portion decreases to ±3.5 cp, which is on the border between a weak deposit and strong deposit. With increasing temperature above 1250 °C, for this specific coal source the viscosity moved into the strong deposit region. After the gasification zone, the viscosity increased again as the material crystallised in the combustion process. For a specific coal source, the viscosity of the slag portion can thus be calculated. The major source of glass is derived from included minerals in carbon rich particles. It is clear that a focus on the modification of the unclassified/amorphous phase, to increase the viscosity (decrease slag formation or have a higher concentration of crystalline phases) at a certain temperature, is important. An AFT analyses only supplies information on the temperature where a mass of material, enough to deform the structure of the cone, starts to slag and does not give information on the properties of the slag below that point. The use of viscosity predictions together with FactSage modelling supplies a better understanding of slag and ash properties at specific temperatures.

CAS-1 lunar soil simulant

Lunar soil simulant is a geochemical reproduction of lunar regolith, and is needed for lunar science and engineering researches. This paper describes a new lunar soil simulant, CAS-1, prepared by the Chinese Academy of Sciences, to support lunar orbiter, soft-landing mission and sample return missions of China’s Lunar Exploration Program, which is scheduled for 2004–2020. Such simulants should match the samples returned from the Moon, all collected from the lunar regolith rather than outcrops. The average mineral and chemical composition of lunar soil sample returned from the Apollo 14 mission, which landed on the Fra Mauro Formation, is chosen as the model for the CAS-1 simulant. Source material for this simulant was a low-Ti basaltic scoria dated at 1600 years from the late Quaternary volcanic area in the Changbai Mountains of northeast China. The main minerals of this rock are pyroxene, olivine, and minor plagioclase, and about 20–40% modal glass. The scoria was analyzed by XRF and found to be chemically similar to Apollo 14 lunar sample 14163. It was crushed in an impact mill with a resulting median particle size 85.9 μm, similar to Apollo soils. Bulk density, shear resistance, complex permittivity, and reflectance spectra were also similar to Apollo 14 soil. We conclude that CAS-1 is an ideal lunar soil simulant for science and engineering research of future lunar exploration program.

Bulk and single‐particle mineralogy of Asian dust and a comparison with its source soils

The mineralogical properties of Asian dust have been examined in detail, and the results have been compared with the Chinese source soils using high‐resolution scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and chemical analysis. Mineralogical classification of Asian dust particles showed that the most common single particles were clay aggregates (48%) that were often mixed with nanosized calcite, followed by particles of quartz (22%), plagioclase (11%), coarse calcite (6%), K‐feldspar (5%), muscovite, chlorite, kaolinite, amphibole, gypsum, Fe and Ti oxides which were either partly or entirely attached with clay‐size mineral grains. The clay minerals in Asian dust were mostly illite and interstratified illite‐smectite. The average mineral composition of the bulk dust samples by X‐ray diffraction was quartz (28%), plagioclase (11%), K‐feldspar (8%), calcite (8%), illite (19%), interstratified illite‐smectite (22%), chlorite (2%), smectite (1%), and kaolinite (1%). In the silty soils from the source regions, the clay minerals and nanosized pedogenic calcite aggregated and covered silt‐size minerals, while the sands were mostly composed of quartz and feldspars and were lined with clay minerals. The mineralogy of Asian dust was similar to that of the silty soil from the loess plateau, but the total phyllosilicate content increased from desert sands (7%), silty soil (23%), to Asian dust (45%), fining eastward. The optical properties of Asian dust and its interaction with atmospheric gases and cloud are probably affected by the clay‐rich mineral composition, the aggregation and attachment of the clay minerals on the coarser minerals, and the nanosized calcite.

Heat flow and matter composition of the lithosphere of the World Ocean

An analysis of the geothermal data on the World Ocean, including those obtained by the author from research vessels of the Russian Academy of Sciences, shows that the heat flow depends on the petrological composition of the oceanic lithosphere. Mean heat flow values are observed in the regions with a lherzolite lithosphere (300–500 mW/m2 depending on the age of the floor). The regions where the lithosphere contains harzburgite enriched with olivine are characterized by high heat flow values, while those with a lithosphere with an average mineral composition feature minimal heat flow values (∼20–30% of the average heat flow). The intermediate contents of olivine correspond to intermediate heat flow values. Based on the calculations performed and on a combined analysis of the thermal and physical parameters of the mantle rocks of the ocean, we inferred that the dependence of the heat flow values on the petrological composition of the lithosphere is valid for marginal basins as well, including basins characterized by diffuse spreading. The results of the geothermal studies in the Tyrrhenian Sea, whose central part is formed due to diffuse spreading, indicate that, in the region of the Vavilov Seamount, the lithosphere is composed of rocks with a lherzolite composition, while the lithosphere in the region of the Marsili Seamount consists of harzburgites of an average mineral composition.

A Review and Prospect for Developing of Lunar Soil Simulants

Lunar soil simulants are geochemical copycats of lunar sample.They have similar chemi-cal composition,mineralogy,particle size distribution,and engineering properties with lunar sample.Simulants of lunar rocks and soils have been developed to satisfy the requirements of a variety ofscientific and engineering investigations.They are essential to meet the system requirements forlunar exploration and in support of future human activities on the Moon.Such studies include ma-terial handling,construction,excavation,and transportation.The simulants is also appropriate forresearch on dust control,spacesuit durability,and agriculture.Five lunar soil simulants,JSC-1,MLS-1,MLS-2,MKS-1,FJS-1 are reviewed in the paper.Theirstarting materials,preparation,and characterization(chemical composition,mineralogy,particle sizedistribution,specific gravity,angle of internal friction,and cohesion)are also listed.China will realize the first lunar exploration before 2007.So it is an essential and pressing taskto develop lunar soil simulants series corresponding to average chemical and mineral composition oflunar sample at Apollo and Luna landing sites.The tentative ideas of developing new lunar simuantsseries based on geologic investigations were brought forward in the end.

MINERAL COMPOSITION OF ASPARAGUS GREEN SPEARS AND THEIR RELATION TO THEIR POST HARVEST LIFE

Mineral content in green asparagus spears from six different farms were evaluated at three times during harvest period (harvest initiation, middle and end of harvest) trying to find out if there was a relationship between mineral nutrient content and period of shelf life. Spear average mineral composition was N 4.63 %, P 0.57 %, K 3.41 %, Ca 0.36 %, Mg 0.16 %, Fe 400 ppm, Zn 75 ppm, Cu 20 ppm, Mn 28 ppm, B 27 ppm. Average spear dry matter content was 6.5 %. Average post harvest shelf life under 2 oC and 95 % relative humidity was 19 days. It was found some relationship between mineral content and post harvest shelf life. Positive correlation coefficients were found for Ca (0.283), Mg (0.325), Fe (0.302) and Cu (0.3). B showed a negative correlation coefficient (-0.39) with decreasing concentration throughout harvest season. Correlation coefficient for dry matter content was –0.484.

Modal mineralogic distribution in the regolith at Apollo landing sites

We have reduced published petrographic data on 90 surface soils from Apollo sample return sites in terms of olivine, pyroxene, plagioclase, and opaques (mostly ilmenite) for a “best estimate”. To do so, we have recast the best estimates of modal mineralogy of mare and highland lithic fragments to add to the monomineralic population of soils. We have assumed that agglutinates and regolith breccias mimic those of local soils. We have thus arrived at a working summary of mineral distribution in areas traversed by Apollo astronauts. In addition, we have proportioned these averages to geologic units in the premission maps to estimate the average mineral composition of areas up to 30 km × 30 km around the landing sites. The calibration and testing of remote sensing signals for planetary exploration depend largely on the ground truth provided by lunar samples. Chemical compositions and the modal distribution of petrologic constituents of most lunar soils are known. These can be grouped spatially to represent areas that coincide with pixels of remote sensing observations and measurements. Signals from certain petrographic constituents such as lithic fragments, breccias, and agglutinates, however, are understandably ambiguous. Petrologic inference from remote sensing signals would be facilitated if petrographic data from actual samples were to be reduced and expressed as sums of single phases occurring in each pixel of observation.

A phytogeochemical survey of the flora of ultramafic and adjacent normal soils in North Morocco

Variation in plant elemental composition (Ni, Ca, Mg, Mg/Ca ratio) in relation to soil composition was investigated in a poorly studied ultramafic area in the north of Morocco. A total of 142 leaf samples representing 36 species from 9 sites (5 ultramafic and 4 normal soils from adjacent areas) were analysed. The soil was richer in Mg and Ni and had a higher Mg/Ca ratio in the ultramafic sites than in the control sites, and these differences were qualitatively reflected in the average mineral composition of the plants. However, there were considerable differences in mineral composition among species within serpentinic sites, indicating that species with contrasting mineral nutrition strategies can cope with the mineral element imbalance characteristic of ultramafic soils. Particularly noteworthy was the finding that species with high requirements of Ca are not excluded from serpentinic soils. In view of their high responsiveness to soil nickel and magnesium concentration, Dittrichia viscosa and Lavandula dentata are proposed as bioindicators of these elements in the soil in the Rif area. By contrast, two local serpentine endemics, Halimium atriplicifolium and Notholaena marantae were excluders of nickel and magnesium.

Mordenite tuff from the Itaoroshi zeolite deposit, Miyagicho, Miyagi Prefecture.

Fourteen specimens of mordenite tuff from the Itaoroshi zeolite deposit, Miyagi-cho, Miyagi Prefecture, were investigated by means of cation exchange, carbon dioxide gas adsorption, X-ray diffraction, chemical analyses and Hunter's whiteness measurement. The specimens were collected from a column of the Shirasawa formation at the vicinity of the zeolite deposit. The bulk chemical composition of them is fairly homogeneous, and ranges in Si/Al ratio from 4.28 to 5.63, averaging 4.81. Equivalent content of Ca2+ surpasses those of Na+, K+ and Mg2+. The content of calcium has good correlation with that of mordenite. Also the significant correlations were recognized among mordenite content, carbon dioxide amount adsorbed, cation exchange capacity (CEC) and total value of cations leached by NH+4. The upper part of the column which is highly mordenitized bed is about 80 meters in thickness. While in the lower part, the mordenite content decreases as the depth increases. Average mineral composition of the 8 specimens collected from the highly mordenitized bed is as follows: mordenite=65.8wt.%, quartz=5.8wt.%, α-cristobalite=1.6wt.%, feldspar=3.3wt.% and amorphous materials=23.5wt.%. Their average CEC is 140.3meq./lOOg.

An inceptisol formed in calcareous loess on the 'Dast-i-Esan Top' plain in North Afghanistan. Fabric, mineral and trace element analysis.

The calcixerollic xerochrept described has a low bulk density (1.1 g/cm3) which is attributed to faunal activity. The average mineral composition was 25% quartz, 20% CaCO3, 15% feldspars, 15% micas, 15% chlorites, 2-3% other minerals and 10% amorphous material and there was a clear relationship between minerals and particle size fractions. Trace element contents were 0.6, 11.0, 23.2, 49.1; 19.4, 75.9, 18.7 and 525 mg/kg for V, Cr, Co, Ni, Cu, Zn, Sr and Ba, respectively. Sr and Ba contents were related to carbonate redistribution. (Abstract retrieved from CAB Abstracts by CABI’s permission)

A Chemically Defined Medium for the Study of Growth, Sporulation, And Presumptive Sporogenic Substances in Alternaria Tomato

Aragaki (1, 2) has reported that 10% vegetable juice (Campbell's V-8 Juice) agar is a suitable medium for studying the effects of light on sporulation. This medium is not suitable for studies on the production and mode of action of sporogenic substances since its chemical composition is not known and since the commercial product is somewhat variable. Use of a chemically defined medium is essential in this type of work but such a synthetic medium must support growth, sporulation, and the production of sporogens at or near the level of a suitable substrate such as 10% vegetable juice. The use of Czapek's sucrose-nitrate medium has proved satisfactory for nutritional studies of many fungi, and Leach and Trione (3) found it to be useful in growing Ascochyta pisi for the production and extraction of P310, a sporogenic substance. Attempts to use Czapek's, or Trione's (4), media resulted in poor growth and sporulation. Consequently, we have prepared a synthetic chemically defined medium based on a detailed chemical analysis of commercial vegetable juice. Analytical values for the average mineral composition and the average vitamin content were provided by the manufacturer. Amino acid analyses were performed by the authors.

The petrology of some Pennsylvanian black "shales" [Iowa-Nebraska

Black fissile shales, from some Missourian and Virgilian cyclothems of central Iowa and eastern Nebraska have been analyzed to determine their chemical and physical properties, the stratigraphic, petrographic, and paleontologic successions over wide geographic areas, and the environment of deposition suggested by these parameters. The stratigraphic succession commonly consists of 3 basic elements: a lower black fissile siltstone; a medial black varved siltstone; and, an upper gray to gray-green shaly siltstone. Organic contents range from 2 to 26%. Acid-soluble contents range from 11 to 38%. An inverse relationship between organic content, fissility, and radioactivity occurs. Petrographically, the silts are predominantly quartz, with lesser amounts of illite, kaolinite, vermiculite, pyrite, and carbonates. The siltstones have an average mineral composition within the range of sub-graywacke to graywacke. Sorting coefficients range from 1.9 to 4.3. No general trend in the degree of sorting is apparent. A definable stratigraphic, petrographic, and paleontologic succession occurs and can be traced over a wide geographic range. The stratigraphic and paleontologic characteristics, as well as many other features, have their closest association with modern tidal flat deposits. The deposits apparently accumulated in both regressive and transgressive seas. The cyclothem boundary occurs within these black silt intervals.

Sandstone Types: Their Abundance and Cementing Agents

A selected sample of 277 sandstones (183 from thin sections and 94 from descriptions in the literature) were classified into five general classes on the basis of detrital mineral composition. The relative abundance of each of these classes was determined, as well as the average mineral composition of each class. A comparison of the carbonate-cemented sandstones with the silica-cemented varieties showed an increase in carbonate in later geologic periods. In the carbonate-cemented sandstones, partial replacement of the detrital grains was almost universal.

Frequency Distribution of the Minerals in Two Petrographic Provinces

The frequency distribution of the major rock-forming minerals in the Oslo petrographic province and in the intra-Pacific province has been determined. In a concluding section several ways to arrive at the average mineral composition of igneous rocks are presented for consideration.