Ein Lateritprofil auf klastischen Sedimenten des Mittelmiozäns von Neyveli (Madrasstate — Indien)     

Prof. Dr. Ida Valeton 《Contributions to Mineralogy and Petrology》1967,14(3):163-175

Zusammenfassung Mittelmiozäne Deltasedimente aus kaolinitischen Quarzsanden, in die sich Kaolinitlagen, Lignit-Linsen und Lateritoidhorizonte einschalten, werden als Aufarbeitungsdetritus des praemiozän lateritisierten Grundgebirges gedeutet. An ihrer Oberfläche befindet sich ein postmittelmiozäner Laterithorizont. Unter Auflösung von Quarz und Zerstörung eines Teiles der Schwerminerale und Tonminerale wurden Eisen-Konkretionen, Kaolinit und Spuren von AI-Hydroxiden und -Oxidhydraten neu gebildet.Diese hier ausgebildete Delta-Fazies — Verknüpfung von lateritischem Umlagerungsschutt mit autochthonen Lateritisierungsvorgängen — kann verglichen werden mit den Bauxiteinschaltungen in klastische Coastal-plain-Serien von Guiana und Queensland und schließlich mit Sidérolitique- und Wealdenfazies.Als ähnliche klastische Serie ist die Tambo Group der Cape York-Halbinsel in Queensland, die nach Evens (1959) ins Tertiär gestellt wird, zu betrachten. Durch Lateritisierung und Bauxitisierung der kaolinitischen Sandsteine (Loughnan u. Bayliss, 1961) bildeten sich hier die wichtigsten derartigen Verwitterungslagerstätten der Welt.Zahlreiche ähnliche Sedimentserien — vorwiegend aus dem Tertiär (Sidérolitique), aber auch aus der Unterkreide (Wealden) und dem Karbon (Millstone grit. Schottlands) werden von Millot (1964, p. 170–183) in dem Kapitel Faciès sidérolitique sehr anschaulich geschildert.

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Middle miocene deltaic sediments forming kaolinitic quartz sands with intercalations of kaolinitic clay layers, lignite lenses and lateritoid horizons are interpreted as reworked detritus of premiocene lateritic soils on the cristallin basement. On top of this series a lateritic horizon of post middle miocene age is developped. The neoformation of iron concretions, kaolinite and traces of Al- hydroxides and -oxidhydrates is accompanied by solution of quartz and destruction of heavy minerals and clay minerals.This deltaic facies — demonstrating a combination of reworked lateritic detritus with autochthonous lateritic soil formation is compared with bauxite intercalations in clastic coastal plain series of Guiana and Queensland and last not least with Sidérolithique and Wealden facies.

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Zur Petrographie der Bauxitlagerstätten auf der „Charnockite-suite“ im Salemdistrikt und in den Nilgiri-Hills,Südindien     

Ida Valeton 《Mineralium Deposita》1968,3(1):34-47

Three profils of fossil Bauxites probably of Early Tertiary age in the Shevaroy Hills and in the Nilgiri Hills, South India, are examined. They are formed by isovolumetric transformation of charnockites under conservation of relict structures. The chemical and mineralogical composition of the bauxites depends on the petrology of the source rock. Na, K, Ca, Mg and the main quantity of silica are extracted, Al and Fe have been enriched relatively and in certain places even absolutely. The mineral transformation in the beginning of the weathering developped in two phases:

1. Leaching and precipitation within the cleavage pattern of the minerals,
2. Leaching and precipitation in the places of the former mineral relicts.

Different later phases of weathering produced Fe- and Al-rich solutions, which are precipitated in the intervals of porous rocks.  相似文献   

Electron spin resonance of stabilized free radicals in sedimentary organic matter     

Zeev Aizenshtat  Ida Pinsky  Baruch Spiro   《Organic Geochemistry》1986,9(6)

Electron spin resonance (ESR) is evaluated as a method to study the thermal degradation of sedimentary organic matter which consists mainly of kerogen. Whole rock and separated kerogen samples were pyrolysed stepwise (ambient to 700°C at 50°C increments), extracted and analysed for elemental composition and ESR spectra at each step. Whole rock samples give rise to complex spectra which include those of paramagnetic metals and are therefore unsuitable in most cases for this purpose.The ESR parameters g value, ΔH and N_g differ for different types of immature organic matter. An increase in N_g,shift of g value to 2.0026–2.0028 and reduction in h are the main trends during pyrolysis and in natural heating of sedimentary organic matter.The peak generations of liquid and gaseous hydrocarbons coincide with maxima of free radical density. ESR spectroscopy in combination with complementary geochemical characterization of the sedimentary organic matter can serve to indicate maturity with respect to peak oil-gas generation.  相似文献   

Low frequency electrical impedance of partially molten gabbro: The effect of melt geometry on electrical properties     

Hiroki Sato  Yoshiaki Ida 《Tectonophysics》1984,107(1-2)

Electrical impedance of partially molten gabbro was measured as a function of the frequency of the applied electric field. The impedance of the partially molten gabbro was mainly controlled by the volume and geometry of partial melt, which were observed with an optical microscope study of the quenched sample. The experimental results are interpreted by a theory that formulates the electrical property of rocks containing partial melt, taking ionic diffusion in the melt into account. The theory evaluates the contributions from two types of melt-geometry distributed in the rock matrix, namely:

1. (a) nearly isolated melt pockets, and

2. (b) connected melt along grain boundaries.

According to the theory, connected melt mainly contributes to the increase of net conductivity, while melt pockets increase displacement current and cause the frequency dependence of impedance. The characteristic ionic diffusivity in melt pockets was determined from the peak frequency of the imaginary part of impedance. The magnitude of diffusion coefficient is estimated to be of the order of 10⁻⁷ to 10⁻⁶ cm²/sec. This suggests that sodium, iron, magnesium and/or calcium ions mainly carry the electric charge in partial melt. The observed frequency dependence of impedance is considered to reflect ionic polarization in melt pockets due to the migration of these alkali ions toward solid-melt interfaces.The present experimental and theoretical work suggests that electrical properties of the earth's upper mantle may involve an intrinsic frequency dependence associated with ionic diffusion in the frequency range of geomagnetic observation, if a partial melt zone exists. The analysis of the earth's conductivity structure may be inadequate if such intrinsic frequency dependence of mantle media is neglected.  相似文献   

Porosity in chalk – roles of elastic strain and plastic strain     

Ida Lykke Fabricius 《Sedimentology》2020,67(7):3451-3470

Chalks originate as Cretaceous to Recent pelagic or hemipelagic calcareous ooze, which indurate via burial diagenesis to chalk and limestone. Because they accumulate in pelagic settings with high environmental continuity, chalks may form thick formations and even groups. For this reason, and because chalks have a simple mineralogy (low magnesium calcite, silica and clays), they are ideal for the study of diagenetic processes including the depth-related decrease of porosity. It is the aim of this study to illustrate how the evaluation of in situ elastic strain can help in understanding these processes including the interplay between stress-controlled diagenetic processes and processes furthered by thermal energy. Petrophysical core and well data can be used for analyses of how porosity reduction via pore collapse and pressure dissolution is related to in situ elastic strain. The data in question are: depth, density of overburden, pore pressure, ultrasonic P-wave velocity and dry density/porosity. The analysis reveals that the transition from ooze to chalk is associated with high elastic strain and consequent pressure dissolution at calcite–particle contacts causing contact cementation. The transition from chalk to limestone is also associated with high elastic strain, especially at clay–calcite interphases causing development of stylolites via pressure dissolution, and consequent pore-filling cementation. Following each transformation the elastic strain drops rapidly. The observation of this diagenesis-related pattern in elastic strain of the sedimentary rock is novel and should not only be helpful in understanding the porosity development in sedimentary basins, but also add basic scientific insight.  相似文献   

Obliquity variations of terrestrial planets in habitable zones     

Keiko Atobe  Shigeru Ida 《Icarus》2004,168(2):223-236

We have investigated obliquity variations of possible terrestrial planets in habitable zones (HZs) perturbed by a giant planet(s) in extrasolar planetary systems. All the extrasolar planets so far discovered are inferred to be jovian-type gas giants. However, terrestrial planets could also exist in extrasolar planetary systems. In order for life, in particular for land-based life, to evolve and survive on a possible terrestrial planet in an HZ, small obliquity variations of the planet may be required in addition to its orbital stability, because large obliquity variations would cause significant climate change. It is known that large obliquity variations are caused by spin-orbit resonances where the precession frequency of the planet's spin nearly coincides with one of the precession frequencies of the ascending node of the planet's orbit. Using analytical expressions, we evaluated the obliquity variations of terrestrial planets with prograde spins in HZs. We found that the obliquity of terrestrial planets suffers large variations when the giant planet's orbit is separated by several Hill radii from an edge of the HZ, in which the orbits of the terrestrial planets in the HZ are marginally stable. Applying these results to the known extrasolar planetary systems, we found that about half of these systems can have terrestrial planets with small obliquity variations (smaller than 10°) over their entire HZs. However, the systems with both small obliquity variations and stable orbits in their HZs are only 1/5 of known systems. Most such systems are comprised of short-period giant planets. If additional planets are found in the known planetary systems, they generally tend to enhance the obliquity variations. On the other hand, if a large/close satellite exists, it significantly enhances the precession rate of the spin axis of a terrestrial planet and is likely to reduce the obliquity variations of the planet. Moreover, if a terrestrial planet is in a retrograde spin state, the spin-orbit resonance does not occur. Retrograde spin, or a large/close satellite might be essential for land-based life to survive on a terrestrial planet in an HZ.  相似文献   

Stress field change around the Mount Fuji volcano magma system caused by the Tohoku megathrust earthquake, Japan     

Eisuke Fujita  Tomofumi Kozono  Hideki Ueda  Yuhki Kohno  Shoichi Yoshioka  Norio Toda  Aiko Kikuchi  Yoshiaki Ida 《Bulletin of Volcanology》2013,75(1):1-14

Crustal deformation by the M _w 9.0 megathrust Tohoku earthquake causes the extension over a wide region of the Japanese mainland. In addition, a triggered M _w 5.9 East Shizuoka earthquake on March 15 occurred beneath the south flank, just above the magma system of Mount Fuji. To access whether these earthquakes might trigger the eruption, we calculated the stress and pressure changes below Mount Fuji. Among the three plausible mechanisms of earthquake–volcano interactions, we calculate the static stress change around volcano using finite element method, based on the seismic fault models of Tohoku and East Shizuoka earthquakes. Both Japanese mainland and Mount Fuji region are modeled by seismic tomography result, and the topographic effect is also included. The differential stress given to Mount Fuji magma reservoir, which is assumed to be located to be in the hypocentral area of deep long period earthquakes at the depth of 15 km, is estimated to be the order of about 0.001–0.01 and 0.1–1 MPa at the boundary region between magma reservoir and surrounding medium. This pressure change is about 0.2 % of the lithostatic pressure (367.5 MPa at 15 km depth), but is enough to trigger an eruptions in case the magma is ready to erupt. For Mount Fuji, there is no evidence so far that these earthquakes and crustal deformations did reactivate the volcano, considering the seismicity of deep long period earthquakes.  相似文献   

Vp‐Vs relationship and amplitude variation with offset modelling of glauconitic greensand‡     

Zakir Hossain  Tapan Mukerji  Ida L. Fabricius 《Geophysical Prospecting》2012,60(1):117-137

The relationship between V_p and V_s may be used to predict V_s where only V_p is known. V_p/V_s is also used to identify pore fluids from seismic data and amplitude variation with offset analysis. Theoretical, physical, as well as statistical empirical V_p‐V_s relationships have been proposed for reservoir characterization when shear‐wave data are not available. In published work, the focus is primarily on the V_p‐V_s relationship of quartzitic sandstone. In order to broaden the picture we present V_p‐V_s relationships of greensand composed of quartz and glauconite by using data from the Paleocene greensand Nini oil field in the North Sea. A V_p‐V_s relationship derived from modelling is compared with empirical V_p‐V_s regressions from laboratory data as well as from log data. The accuracy of V_s prediction is quantified in terms of root‐mean‐square error. We find that the V_p‐V_s relationship derived from modelling works well for greensand shear‐wave velocity prediction. We model the seismic response of glauconitic greensand by using laboratory data from the Nini field. Our studies here reveal that brine‐saturated glauconitic greensand can have a similar seismic response to that from oil‐saturated quartzitic sandstone and that oil‐saturated strongly cemented greensand can have a similar amplitude variation with offset response to that from brine‐saturated weakly cemented greensand.  相似文献