Minerals In Sedimentary Rocks Research Articles

Ikaite, the parent mineral of jarrowite-type pseudomorphs

The pseudomorphs known as jarrowite which were found during the middle part of the last century in muds at Jarrow Slake on the River Tyne are now identified as being pseudomorphs after crystals of the mineral ikaite. Ikaite, CaCO3.6H2O, is a metastable mineral in sedimentary rocks. It crystallizes at near to zero Celsius, but breaks down at normal temperatures to form calcium carbonate and water. Jarrowites are pseudomorphed in calcite which appears to have been generated by redistribution of the calcium carbonate formerly present in the parent ikaite. The high porosity of the jarrowites is the result of the decrease in volume which accompanied the change. The paper reviews the known occurrences of pseudomorphs of jarrowite-type (pseudogaylussite, thinolite, White-Sea hornlets, glendonite, gersternkorner, gennoishi, fundylite and others), the discovery of ikaite and the ways in which the pseudomorphs alter ikaite may have a role as palaeothermometers.

Dielectric Log-A Logging Method for Determining Oil Saturation

Summary This paper presents the principles of dielectric logging by describing measurement of phase shift. laboratory experiments, theoretical calculations for determining the vertical resolution and depth of investigation, and results of application in field practice. Introduction Measurement of oil saturation is an important pan of well logging in the development of- an oil field. It is an important basis for evaluating watered-out reservoirs, estimating the residual oil, and redividing and combining the productive zones. In the development of an oil field by water injection, the salinity of injected water always differs greatly from that of original formation water. For example, the salinity of original formation water in Daqing oil field is about 6,000 to 8,000 ppm, and the salinity of the injected water is as low as 500 to 800 ppm. Thus, the formation water gradually becomes less saline as the amount of injected water is increased. However, the resistivity log and the Neutron Lifetime Log- cannot be used to measure oil saturation in such strata. To solve this problem, it is necessary to introduce other logging methods for measuring oil saturation that are less influenced by the salinity of formation water. Dielectric constant logging is one method to solve this problem and has been described in U. S. and Soviet literature. In the late 1960's, the study of dielectrologs was launched in Daqing oil field. Both theoretical and experimental studies on dielectrologs were carried out. Since 1974, the dielectrolog tool has been used in the field and has been run in more than 100 downhole operations. Field practice has proved that the accuracy for interpreting water saturation of formation and watered-out zones with dielectrolog is +/-8. 8% and +/-5. 7%, respectively. Laboratory Experiment For Determining Dielectric Constant of Rocks The dielectric constants for crude oil and minerals of sedimentary rocks are small (2 to 8), and that for water is very high (80). Therefore, the dielectric constant for water-bearing rocks depends mainly on its water volume. To verify the fundamental principle of this logging method, a laboratory study of main factors affecting the dielectric constant of rocks was performed with core samples from different oil-beefing zones in Daqing oil field. The frequency used here is 60 MHz. Fig. 1 gives the relationship between the dielectric constant and formation water volume of sandstone samples from different regions of Daqing oil field. Air saturation is used instead of oil saturation in these experiments. In Fig. 1 the dielectric constants of rocks correspond very well with the water volume. The dielectric constants of dry samples range from 4 to 7; those of rock matrix, oil, and air are rather small because they depend on shift polarization. JPT P. 1797^

Detrital remanent magnetization in hematite

Heavy mineral placer layers within channel sandstones of the Morrison Formation (western United States) have been shown to contain a very stable, accurate record of the Jurassic geomagnetic field. These laminae are composed almost entirely of hematite grains; in particular, they are largely the hematite pseudomorph of magnetite, martite. The laminae record the correct geomagnetic field direction during a period of rapid apparent polar wander, which suggests an early acquisition of the remanence. Several other remanence characteristics imply that the remanance is probably a detrital remanent magnetization (DRM): (1) there is large directional dispersion in one lamina which had been heavily burrowed by organisms (measurement of individual burrows shows that the burrowing disrupted and randomized the magnetization held in the martite grains), (2) directions of laminae that were deposited on sloping surfaces are significantly deflected from the directions of the flat–lying laminae, (3) more than 50% of the martite grains have high‐temperature oxidation features, suggesting that they may have been martite at the time of deposition. These characteristics, in particular the burrowing disturbance, strongly suggest that the martite was deposited as martite and that the remanence is a DRM, as opposed to deposition of magnetite grains which were altered to hematite after deposition. Examination of recent weathering debris on igneous outcrops shows a substantial amount of martite on these outcrops. This observation provides further evidence in support of the idea that hematite, and in particular, martite, can be a deposited mineral in sedimentary rocks and thus can carry a DRM.

The Olympic Dam copper-uranium-gold deposit, Roxby Downs, South Australia

A new type of stratabound sediment-hosted ore deposit. The deposit is estimated to contain in excess of 2,000 million metric tons of mineralized material with an average grade of 1.6 percent copper, 0.06 percent uranium oxide, and 0.6 g/metric ton gold. Proterozoic. Graben fill sediments were deposited in an arid subaerial environment during rifting or strike-slip faulting. The stratabound sulfide mineralization is syngenetic or syndiagenetic and is probably related to local volcanism. Uranium and rare earths were deposited during and after the sulfide mineralizing phase. Unusual features are the association of copper, uranium, rare earths, and gold; the association of reduced sulfur species such as chalcocite and bornite with high hematite concentrations; and the occurrence of stratabound copper and uranium minerals in sedimentary rocks deposited in a very high-energy environment.--Modified journal abstract.

Numerical Dating in Stratigraphy, 1 and 2

Geology is a historical science, and geologists always have been fascinated with deciphering complex geologic histories by unraveling the relations of rock units where ages were established by fossils or, more recently, by isotopic dating methods. The most direct way to date stratified rocks is by measuring the ages of authigenic minerals in sedimentary rocks. This approach, however, is fraught with such problems as the presence of detrital minerals, the determination of whether authigenic minerals formed at the same time as accumulation of the sedimentary rocks, and whether suitable minerals for age measurements are present. This new book shows that although there has been significant progress, the problems of directly dating sedimentary rocks by isotopic methods persist.

FISSION TRACK ANALYSIS: A NEW TOOL FOR THE EVALUATION OF THERMAL HISTORIES AND HYDROCARBON POTENTIAL

Fission track dating is a new approach to the interpretation and quantitative modelling of thermal histories of sedimentary basins for hydrocarbon resource evaluation. This technique depends on the observation that annealing of fission tracks in minerals, like the generation and maturation of hydrocarbons, is a function of temperature and time. The temperature interval over which track annealing occurs in the mineral apatite, a common detrital mineral in sedimentary rocks, is virtually identical (60° to 125°C) with that required for the maximum generation of liquid hydrocarbons. Fission tracks in apatite separated from a rock sample thus contain a record of its heating in the oil generation window. The pattern of apatite fission track ages, together with detailed analyses of the distributions of track lengths, will yield information on thermal history unobtainable by other methods. The unique advantage of the fission track method is that it can give information not only on maximum palaeotemperatures, but also their variation through time.Fission tracks in detrital zircon and sphene are stable to higher temperatures (200° - 300°C) than in apatite enabling limits to be placed on maximum temperatures reached in sedimentary basins, as well as giving important information on sedimentary provenance.In the Otway and Gippsland Basins fission track ages and lengths determined on apatites, and ages determined on sphenes and zircons, have been used to reconstruct the thermal histories of different areas. Ages and track lengths of apatites from deep wells in the Otway Basin show the expected down hole decrease reaching zero apparent age where present well temperatures are about 125°C. The shape of the track length distribution is characteristic of the position of a sample within the track annealing zone and hence the oil generation window. Flaxmans-1 in the Otway Basin has an age profile indicating that present temperatures are at or very near the maximum experienced. In Eumeralla-1 sediments that lie above the present-day track annealing zone show clear evidence of track annealing in the past, indicating that temperatures have decreased. This is consistent with the relatively small amount of post-Early Cretaceous sedimentation observed in this well compared to Flaxmans-1.Fission track analysis thus has the potential of giving a new, quantitative perspective on the temperature history of rocks, which should have an important impact on techniques of petroleum exploration.

Relation between Authigenic Mineral Zones and Maturation of Organic Matters in Sedimentary Rocks of Hokkaido, Akita and Niigata Oil Fields in Japan

The authigenic minerals in sedimentary rocks commonly consist of zeolites, silica minerals and clay minerals as shown in Fig. 2. These minerals are mainly formed by burial diagenesis. The reaction temperatures to form these minerals are particularly affected by physical factors; heating time and geothermal gradient. The transformation of the authigenic minerals is similar to the progress of maturation of organic matters in sediments.From this study, the variations of the authigenic mineral zones in the Cretaceous and Tertiary sediments of Hokkaido, Akita and Niigata fields are correlative with the various parameters for determining maturation levels in organic matter. The parameters include vitrinite reflectance, elemental analysis and colouration of kerogen, the ratio of extractable hydrocarbon to organic carbon and carbon preference index. For example, the first occurrences of clinoptilolite, analcime, albite and montmorillonite-illite mixed layer mineral are 0.35, 0.53, 0.68 and 0.50% in vitrinite reflectance, respectively.The oil generation zone, which corresponds to vitrinite reflectance of 0.5 to 1.3% and is defined by a large ratio of extractable hydrocarbon to organic carbon, approximately belongs to the analcime to the albite or the mixed layer mineral to the illite zone. The maximum of the oil generation zone is distributed in the albite and/or the illite zone.The authigenic minerals are considered to be an important parameter to indicate the maturation levels of organic matter in sediments.

Silica Mineral Diagenesis in Neogene Tertiary Shales in the Tempoku District, Hokkaido, Japan

ABSTRACT Mineralogical and chemical studies of silica minerals from shales of Neogene Tertiary age in the Tempoku district, Hokkaido, Japan lead to a proposed mechanism of diagenesis and transformation of silica minerals in sedimentary rocks. A zonal distribution of amorphous silica, opalcristobalite, low-cristobalite and low-quartz is recognized successively from the younger to older strata. In particular, the value of d(101) and the peak width of 50% intensity in cristobalite show a progressive decrease with increasing depth of burial. It is suggested that most of the silica minerals in the samples studied originated by alteration of diatoms rather than any other source. The studied sequences have fairly uniform muddy facies with rare intercalation of pyroclastic sediments and show no evidence of hydrothermal alteration or metamorphism. Under the microscope amorphous silica is usually associated with abundant diatom fossils whereas cristobalite and diatoms rarely occur together. We interpret the zonal distribution of the neoformed silica minerals as an induction of diagenetic alteration of biogenic silica,

Subdivision and petrology of the Mesozoic rocks Of Coromandel (Manaia Hill Group)

Abstract The original unconformable threefold subdivision of the sedimentary Mesozoic basement rocks of Coromandel is redefined as two conformable formations (Moehau and Tokatea Hill) within Manaia Hill Group on the basis of gradational detrital content and structural continuity; the new sequence is inverted with respect to previous subdivision. Standard sections are described for both formations (Moehau 520–610 m minimum; Tokatea Hill 530 m maximum). The older formation (Moehau) is characterised by a lithic volcanic greywacke and sub-greywacke suite derived from calc-alkaline volcanic and plutonic rocks, and minor sedimentary rocks, whereas the younger formation (Tokatea Hill) is a feldspathic greywacke suite, almost devoid of volcanic detritus except near the base, derived from a more mature calc-alkaline plutonic landmass with minor sedimentary rocks. Moehau Formation and the lower part of the Tokatea Hill Formation are slope-deposited turbidites, whereas the upper Tokatea Hill Formation resulted from ...

Length-slow Chalcedony after Sulphate Evaporite Minerals in Sedimentary Rocks

IN a study of authigenic silica in the Cretaceous Edwards Limestone of Travis County, Texas, J. S. P.1 noted in passing that some of the chalcedony had a peculiar 60° grid structure and was also length-slow as tested by insertion of the gypsum plate; this is in contrast to normal chalcedony which is length-fast. (In this context, “length-slow” means that the slower polarized light component produced in double refraction is the one vibrating parallel to the crystal length; “length-fast” can be defined similarly for the faster component.) These chalcedony masses, which grade outward into megaquartz, came from an area of collapse structures apparently caused by solution of gypsum/anhydrite- nodules with some replacement by authigenic silica. West2 has also found length-slow chalcedony in Jurassic evaporitic deposits in England. It therefore seemed possible that there was a connexion between length-slow chalcedony and sulphate evaporite minerals and comprehensive literature search revealed more examples of length-slow chalcedony—all associated with evaporites.

Polytypism of Chlorite in Sedimentary Rocks

AbstractFour chlorite polytypes of Bailey and Brown (1962) have been identified by X-ray diffraction in clay-size chlorites of soils, sediments, and sedimentary rocks: (1) IIb, the polytype of common metamorphic and igneous chlorites; (2) Ib(ß = 90°); (3) Ib(ß = 97°); (4) Ia. An additional stacking arrangement. Iba, is defined herein as disordered chlorite which lacks an h0l diffraction band in the 2.4–2.5 Å region.Most type-I chlorites are authigenic, as demonstrated by thin-section petrography. Type-I chlorites form during diagenesis, or less commonly during halmyrolysis, at temperatures and pressures less than those of low-grade metamorphism. A type-1 crystallization sequence is proposed, from least to most stable: Iba → Ib(ß = 97°) → Ib(ß = 90°). Conditions of low-grade metamorphism usually are necessary to cause conversion of Iba(ß = 90°) to IIb, the most stable and common polytype. Chemical composition has little or no influence upon polytype relative stabilities; temperature is much more important.Sediment source areas with high relief, abundant rainfall, cold climate, and which contain IIb-chlorite-bearing metamorphic rocks, may yield essentially unweathered IIb chlorite to sites of deposition. Thus, clay-size IIb chlorite in unmetamorphosed sedimentary rocks can be interpreted as detrital. Caution is required, however, because IIb may be able to form authigenically at submetamor-phic temperatures, because it is the most stable polytype. Petrographic evidence is useful in such cases.Chlorite polytypism as a geothermometer can be applied to several geologic problems: (1) the authigenic versus detrital origin of clay minerals in sedimentary rocks, particularly in graywacke matrix; (2) the recognition of diagenetic facies or gradients, areally and stratigraphically, within given geologic provinces; (3) the detection of hydrothermal and incipient metamorphic effects. Chlorite polytypism merits general application as an interpretive tool.

Origin of Banded Iron Formations

It is concluded from the present-day geochemistry of iron, and its probable paleogeochemistry that a primary accumulation of this element cannot arise in a marine environment. The Precambrian banded iron formations are, therefore, suggested to have been formed in a lacustrine or closed-basin environment. Known limnological processes are invoked to provide a mechanism for the common rhythmic banding of iron and silica. The difference between the dominantly nondetrital, low-alumina, banded Early-Middle Precambrian and the dominantly detrital, high-alumina, oolitic Late Precambrian and post-Precambrian iron formations is linked to the effects upon weathering processes of a change in the character of the earth9s crust and of the development of biotic systems. Hematite is considered to be the only primary iron mineral in sedimentary rocks; other iron minerals, particularly the ferrous silicates, are regarded as essentially diagenetic (although probably preconsolidation) in origin. Organic matter has an important influence on both weathering and diagenetic processes.

Occurrence of Talc as a Clay Mineral in Sedimentary Rocks

TALC is a metamorphic and hydrothermal mineral which is found typically in the greenschist facies of metamorphic rocks, and in shear zones where it is an alteration product. Talc has recently been found to be widespread in lime stones of many formations ranging in age from Devonian through Recent. Where present, it is almost invariably accompanied by chlorite; other clay minerals may or may not be present. The occurrence of talc has also been noted in sandstones and shales, but in these rocks it is extremely uncommon.

γ-ray Irradiation Effects on Porphyrin Compound

In consideration of the radiation effects on the origin of petroleum, the writers irradiated with γ-ray on Cu chlorophyrin Na salt, which is a primary derivative of chlorophyll(a source material of petroleum).The results are discussed from geochemical point of view. Desaltization of Cu chlorophyrin Na salt by γ-ray irradiation is the first order reaction of radiation dose. A portion of Cu chlorophyrin Na salt transferred to pheoporphyrin, pheocrythrin and a similar of chlorin. Gaseous products consisting of hydrogen, methane, ethylene, ethane, propane and carbondioxide are obtained. The presence of rocks and water has an influence on radiolysis, and the effects are more pronunced than those obtained during irradiation in bulk.From these experimental results, the writers suggest that natural radioactivity from minerals in sedimentary rocks might play an important role for the formation of petroleum.

Studies on Clay Minerals in the Oil-bearing Neogene Tertiary Sedimentary Rocks of Northwest Honshû, Japan, with a Proposal of Criteria for Analysis of Clay Minerals in Sedimentary Rocks

The author has been studying on clay minerals in the oil-hearing Neogene Tertiary sedimentary rocks of Northwest Honshû, Japan. In this paper he describes his provisional criteria for analysis of clay minerals in sedimentary rocks, with his basic considerations and laboratory experiments, which he conducted. He adds supplementary notes on the qualitative analysis to his preceding paper20). He also summarizes some noteworthy sedimentological relations, which have been considered by him to exist in sedimentary sequences of many geological basins. Contents of this paper are as follows: 1) Progress of basic experiments for the establishment of the criteria and some result of qualitative analysis are described. a) X-ray diffraction analysis applied to centrifugal fractions of mudstones due to random powder method. b) X-ray diffraction analysis combined with various reagent-treatments and heat-treatment, applied to centrifugal fractions of mudstones due to powder orientation method. 2) He determined clay mineral suit of montmorillonite-illite-chlorite (± minor amount of montmorillonite-illite mixed layer), for the oil-bearing Neogene Tertiary sedimentary rocks in Northwest Honshû, Japan. 3) He proposed a classification of mudstones due to relative amount of clay minerals and quartz. 4) He found the striking negative correlation between the montmorillonite log (or clay mineral log) and the log of “Cl'-concentration of interstitial water” in mudstones, prepared for the exploration well Mitsuke SK. 1 (or Tamugiyama SK. 1). Based on consideration of it, he interpreted that a part of the so-called interstitial water, is composed of that delivered from interlayer water of montmorillonite crystals, through the pretreatment or heating up to 110°C of core samples. This interpretation is supported by the result of another experiment of his own, in which the oscillation method of X-ray diffraction analysis during heating up to 900°C, is applied to a centrifugal fraction of a mudstone cored from the depth of 1098m of the well Tamugiyama SK. 1. 5) The author determined clay-mineralogical divisions on the montmorillonite log, and he found that these divisions coincide with fossil foraminiferal subzonules. 6) On the Q-M (quartz-montmorillonite) diagrams characteristic distribution curve can be drawn for each fossil foraminiferal biotope unit in the Mitsuke and Tamugiyama sections. Existence of a kind of sedimentological relation is suggested by the comparison of relative positions of these characteristic distribution curves on Q-M diagrams with their corresponding foraminiferal faunal assemblages. 7) The author describes the possibility to determine characteristic distribution curves on the M-I-Chl (montmorillonite-illite-chlorite) triangular diagrams for geological formations or members. 8) The criteria for analysis of clay minerals in sedimentary rocks, which he proposed, are described. 9) In conclusion, present status and future problems of the sedimentary clay mineralogy, especially that concerning petroleum exploration and exploitation, are summarized.

Studies on Clay Minerals in the Oil Tertiary Formations of Northeast Honshu, Japan, with a Proposal of Provisional Standards of Analysis of Clay Minerals in Sedimentary Rocks

The writer has been studying on clay mineral composition of some of the tertiary sedimentary rocks in Northeast Honshu, Japan, for the purpose of organization of new method to be useful for petroleum exploration based on mineralogy and sedimentology. Fundermental problems and experiments to determine standard conditions of pre-treatment and X-ray diffraction measurement, are described and some of the results of analysis is considered.

Geochemical Method for Determining Paleosalinity

AbstractThe boron content of sea water increases linearly with salinity within the range tested. The boron content of the illite minerals in the clay mineral size fraction of many types of sedimentary rocks has been shown to increase with the “geologically known” salinity prevailing during deposition of the rocks. It is believed that boron is abstracted by the illitic clay minerals from sea water in proportion to the salinity of the sea water. This boron content is not substantially changed by other geological processes normally operative in sedimentary rocks. It is concluded that the boron content of illite minerals in sedimentary rocks can be used to evaluate the salinity of the sea prevailing at the time the sediment was deposited.

The environmental control of sedimentary iron minerals

An Eh-pH stability diagram is developed for hematite, magnetite, siderite, pyrite, and iron sulfide that indicates the relative position of their stability fields in a normal sea water system. With the exception of the magnetite-siderite relationship, Eh is much more critical than pH. In general terms, hematite is stable under oxidizing conditions, siderite and magnetite under intermediate to moderately reducing conditions, pyrite under moderate to strongly reducing conditions, and iron sulfide under still stronger reducing conditions. Because of numerous variables involved the relative positions of the stability fields are stressed rather than their limits on the Eh and pH scales. The inclusion of a magnetite field suggests that magnetite should be much more important as a primary or diagenetic mineral in sedimentary rocks than has been commonly recognized. This is in accord with numerous recent suggestions to that effect. The importance of thermodynamic equilibrium is stressed and it is suggested that differences in rates of formation of the various minerals and the persistence of some metastable phases are among the commonest causes of lack of equilibrium.

Geologic Interpretation of Argillaceous Sediments: Part I. Origin and Significance of Clay Minerals in Sedimentary Rocks

X-ray analyses of the clay minerals from thousands of sediments indicate that any of the major clay minerals can occur in abundance in any of the major depositional environments and there is no consistent coincidence between specific clay minerals and specific depositional environments. It is concluded that the great majority of clay minerals in sedimentary rocks are detrital in origin, strongly reflect the character of their source material, and are only slightly modified in their depositional environments. The most common process acting on the clay minerals in marine environments is cation adsorption. The modifications produced by this process are secondary but because of the overemphasis of names rather than processes, they have been considered fundamental changes and the process has been called diagenesis. From the geologist's viewpoint, the basic clay mineral lattice, which is inherited from the source material, is the most significant parameter of the clay minerals, and modifications caused by the adsorbed cations are secondary, derived parameters reflecting the character of the depositional environment. This concept of dualism is essential to the understanding of clay genesis and the significance of the two parameters must be understood before a genetic classification can be constr cted and before clays can be used for geologic interpretation.

A Discussion on the Origin of Clay Minerals in Sedimentary Rocks

AbstractX-ray analyses of the clay minerals from thousands of sediments indicate that any of the major clay minerals can occur in abundance in any of the major depositional environments and there is no consistent coincidence between specific clay minerals and specific depositional environments. It is concluded that the great majority of clay minerals in sedimentary rocks are detrital in origin, strongly reflect the character of their source material, and are only slightly modified in their depositional environments.The most common process acting on the clay minerals in marine environments is cation adsorption. The modifications produced by this process are secondary but because of the overemphasis of names rather than processes, they have been considered fundamental changes and the process has been called diagenesis. From the geologist’s viewpoint, the basic clay mineral lattice, which is inherited from the source material, is the most significant parameter of the clay minerals and modifications caused by the adsorbed cations are secondary, derived parameters reflecting the character of the depositional environment. This concept of dualism is essential to the understanding of clay genesis, and the significance of the two parameters must be understood before a genetic classification can be constructed and before clays can be used for geologic interpretation.