Implementation of the Iterative Proportion Fitting Algorithm for Geostatistical Facies Modeling     

Yupeng Li  Clayton V. Deutsch 《Natural Resources Research》2012,21(2):221-231

In geostatistics, most stochastic algorithm for simulation of categorical variables such as facies or rock types require a conditional probability distribution. The multivariate probability distribution of all the grouped locations including the unsampled location permits calculation of the conditional probability directly based on its definition. In this article, the iterative proportion fitting (IPF) algorithm is implemented to infer this multivariate probability. Using the IPF algorithm, the multivariate probability is obtained by iterative modification to an initial estimated multivariate probability using lower order bivariate probabilities as constraints. The imposed bivariate marginal probabilities are inferred from profiles along drill holes or wells. In the IPF process, a sparse matrix is used to calculate the marginal probabilities from the multivariate probability, which makes the iterative fitting more tractable and practical. This algorithm can be extended to higher order marginal probability constraints as used in multiple point statistics. The theoretical framework is developed and illustrated with estimation and simulation example.  相似文献   

Two Artifacts of Probability Field Simulation   总被引：1，自引：0，他引：1  

Michael J. Pyrcz  Clayton V. Deutsch 《Mathematical Geology》2001,33(7):775-799

Probability field simulation is being used increasingly to simulate geostatistical realizations. The method can be faster than conventional simulation algorithms and it is well suited to integrate prior soft information in the form of local probability distributions. The theoretical basis of probability field simulation has been established when there are no conditioning data; however, no such basis has been established in presence of conditioning data. Realizations generated by probability field simulation show two severe artifacts near conditioning data. We document these artifacts and show theoretically why they exist. The two artifacts that have been investigated are (1) local conditioning data appear as local minima or maxima of the simulated values, and (2) the variogram model in range of conditioning data is not honored; the simulated values have significantly greater continuity than they are supposed to. These two artifacts are predicted by theory. An example flow simulation study is presented to illustrate that they affect more than the visual appearance of the simulated realizations. Notwithstanding the flexibility of the probability field simulation method, these two artifacts suggest that it be used with caution in presence of conditioning data. Future research may overcome these limitations.  相似文献   

The climate of crete in the sixteenth and seventeenth centuries   总被引：1，自引：0，他引：1  

Jean M. Grove  Annalisa Conterio 《Climatic change》1995,30(2):223-247

The climatic history of the eastern Mediterranean has been neglected; that of Crete is selected for initial investigation. The principal characteristics of twentieth century climate are surveyed. The most important documentary sources for the sixteenth and seventeenth centuries are introduced, their potentialities discussed and examples of documentary evidence given. Detailed consideration is given to the period 1548 to 1648, and its main climatic features tabulated. In some years, and groups of years, weather conditions occurred which were apparently anomalous by twentieth century standards, especially winter and spring droughts, exceptionally severe winters, and summer rain. Specific cases are discussed. Some winter droughts were longer-lasting and more extreme than any since instrumental measurements began. These could affect wide regions and are taken to have been caused by the extension of southerly air masses from the Sahara. The incidence of severe winters leads to consideration of evidence for snowfall having been heavier and longer lasting than in the nineteenth and twentieth centuries. Deluges seem to have been similar in intensity to twentieth century storm events, but some may have been more extreme and extended more widely. Records of summer rains were found to be rare compared with those of winter drought and severe winters. The period under review was one in which northern and central Europe experienced individual years and clusters of years in which weather conditions departed strongly from twentieth century means. It is surmised that climatic anomalies, which did not necessarily occur simultaneously in the eastern and western Mediterranean, were associated with low index situations, that is with weak circumpolar westerlies, and with blocking highs further north in Europe, causing diversion of depression tracks.  相似文献   

Glacial geological evidence for the medieval warm period   总被引：8，自引：0，他引：8  

Jean M. Grove  Roy Switsur 《Climatic change》1994,26(2-3):143-169

It is hypothesised that the Medieval Warm Period was preceded and followed by periods of moraine deposition associated with glacier expansion. Improvements in the methodology of radiocarbon calibration make it possible to convert radiocarbon ages to calendar dates with greater precision than was previously possible. Dating of organic material closely associated with moraines in many montane regions has reached the point where it is possible to survey available information concerning the timing of the medieval warm period. The results suggest that it was a global event occurring between about 900 and 1250 A.D., possibly interrupted by a minor readvance of ice between about 1050 and 1150 A.D.  相似文献   

Kriging with strings of data   总被引：1，自引：0，他引：1  

Clayton V. Deutsch 《Mathematical Geology》1994,26(5):623-638

The concept of a random function and, consequently, the application of kriging cells for the implicit assumption that the data locations are embedded within an infinite domain. An implication of this assumption is that, all else being equal, outlying data locations will receive greater weight because they are seen as less redundant, hence, more informative of the infinite domain. A two- step kriging procedure is proposed for correcting this siring effect. The first step is to establish the total kriging weight attributable to each string. The distribution of that total weight to the samples in the string is accomplished by a second stage of kriging. In the second stage, a spatial redundancy measure r_(n) is used in place of the covariance measure in the data-data kriging matrix. This measure is constructed such that each datum has the same redundancy with the (n)data of the string to which it belongs. This paper documents the problem of kriging with strings of data, develops the redundancy measure r_(n),and presents a number of examples.  相似文献   

Amphibole zoning in the Garland Peak Syenite,Red Hill complex,New Hampshire: camptonitic parental magmas and differentiation to silica-oversaturated syenites     

Michael J. Dorais  Neil D. MacRae  T. Grove 《Contributions to Mineralogy and Petrology》1994,117(1):76-86

The Garland Peak Syenite (GPS) of the Red Hill complex, New Hampshire, consists predominantly of amphibole, oligoclase, perthite, and quartz; amphiboles have homogeneous kaersutite cores with strongly zoned rims ranging in composition from pargasite to hastingsite to hornblende. The thin section scale association of kaersutite, an amphibole that typically crystallizes in silica-undersaturated magmas, with quartz suggests that the GPS magma experienced substanital changes in magmatic composition, including silica activity, during its crystallization history. Kaersutite-bearing camptonites are also associated with the Red Hill complex. The camptonite amphiboles are very similar in composition to the core kaersutites in the GPS, suggesting that the earliest GPS liquid may have had camptonitic affinities. In order to elucidate the process where-by silica-undersaturated magmas differentiate to saturation, amphiboles in these rocks were analyzed by electron and ion microprobe techniques. Amphiboles show a progressive increase in REE abundances from the camptonites to the GPS kaersutite cores to the GPS pargasite/hastingsite/hornblende rims. The systematic change in REE concentrations, and the variations in V, Ti, Sr versus Zr, Eu/Eu⁰ and La/Yb versus Ce, suggest a possible differentiation relationship for the amphiboles and imply that the GPS was derived from magmas similar to camptonites. Rimward depletions in Sr, Ti, V, and Eu/Eu⁰, and the increase in La/Yb values suggest that parental camptonites fractionated plagioclase, magnetite, and amphibole to produce the silica-oversaturated GPS. Bulk-rock modelling agrees with the trace element record preserved in the amphiboles, that plagioclase, magnetite, and amphibole fractionation caused silica saturation. Minor pegmatitic patches occur in the GPS. Ferrohornblendes in the pegmatites have REE abundances distinct from the other GPS amphiboles, and this difference may be due to open system processes.  相似文献   

Cristobalite-pyroxene in an L6 chondrite: implications for metamorphism     

Edward J. Olsen  Toshiko K. Mayeda  Robert N. Clayton 《Earth and Planetary Science Letters》1981

CRISPY is a cristobalite-pyroxene assemblage in the L6 chondrite ALHA 76003. It was formed by reaction of a very siliceous inclusion with the surrounding olivine-rich rock. Oxygen isotopes show that the inclusion was derived from a source with non-chondritic isotopic composition. The isotopes also show that the oxygen of the pyroxene reaction product was derived by simple mixing of oxygen from the inclusion and its immediately adjacent surroundings, with exchange with the bulk meteorite limited to a distance of about a millimeter. The persistence of cristobalite in close proximity to olivine, and the lack of isotopic equilibration, show that the metamorphic processes that form petrographic grade 6 chondrites involve transport of major elements over distances only on the order of millimeters.  相似文献   

Basalts as probes of planetary interiors: Constraints on the chemistry and mineralogy of their source regions     

A.E. Bence  T.L. Grove  J.J. Papike 《Precambrian Research》1980,10(3-4)

Basalt magmas, derived by the partial melting of planetary interiors, have compositions that reflect the pre-accretionary history of the material from which the planet formed, the planets, subsequent evolutionary history, the chemistry and mineralogy of the source regions, and the intensive thermodynamic parameters operating at the source and emplacement sites. Studies of basalt suites from the Earth, its Moon, and the eucrite parent body reveal compositional differences intrinsic to their source regions which are, in turn, a characteristic of the planet and its formational and evolutionary history.Major interplanetary differences are observed in iron, , TiO₂, Al₂O₃, Na₂O, Cr, Ni, and in volatile element abundances. The most primitive mare basalts have Mg#s 0.6, on the Earth they are 0.70–0.72 for mid-ocean ridge basalts (MORBs) and up to 0.9 for Archean peridotitic komatiites. Eucrites have Mg#s approaching 0.5 (excepting Binda). These differences reflect inherent differences in of their sources. Striking differences in the TiO₂ abundances of the planetary basalts reflect both inter- and intra-planetary variations in source chemistry. Primitive MORBs and primitive oceanic intraplate tholeiites have a factor of 2–3 difference in TiO₂ at comparable Mg# (0.7–1.2 vs 2–3 wt.% respectively). Three major titania groups are recognized in the mare suite; high TiO₂ (8–13 wt.%), low TiO₂ (2–5 wt.%) and very low TiO₂ (<1 wt.%). The eucrites have TiO₂ contents <1 wt.%.The mare basalts and eucrites have pronounced Na₂O depletion relative to all terrestrial basalts. This is a consequence of the preplanetary accretion loss of volatiles from the material that formed the Moon and the eucrite parent bodies.Mare basalts have consistently lower Al₂O₃ contents than the terrestrial basalts. This may be due either to an inherently lower content of Al₂O₃ in the mare sources or it may reflect Al₂O₃ retention in an aluminous phase.The transition metals are fractionated in all three basalt suites. For terrestrial basalts this may reflect core-separation; however, in the case of the Moon and eucrite parent bodies pre-accretionary separation of metal and silicates is a more reasonable explanation. A pronounced Cr anomaly is observed in terrestrial MORBs but not in the mare basalts. This appears to be related to f_O2 differences in the respective mantles.Overall rare earth element abundances are comparable between all three objects. Mare basalts have a pronounced negative Eu anomaly which is inherited from their source region and is record of plagioclase removal from crystallizing magma ocean early in lunar history (4.4–4.6 Ga). Early separation of plagioclase on the Earth appears to have been a relatively unimportant process.  相似文献   

Cosmoradiogenic ghosts and the origin of Ca-Al-rich inclusions     

Donald D. Clayton 《Earth and Planetary Science Letters》1977,35(3):398-410

The Ca-Al-rich inclusions within Allende are described as quickly frozen non-equilibrated partial melts arising from energetic collisions between centimeter-sized mechanical accumulations of cold presolar grains. The resulting minerals are refractory-rich because refractory supernova condensates are the most persistent components of the preheated accumulates. The shock heating drives off most of the more volatile matrix that had accumulated cold around the refractory cores, which quickly recrystallize while picking up isotopically homogenized trace elements. This picture is advanced to account for the isotopic anomalies in those elements for which fractionation of stardust from gas also fractionates a special isotope whose stellar condensation history can be expected to have been special.I call the anomaly that would have existed before the special component was added anisotopic ghost. These ghosts can be larger than the special anomaly surviving today in meteorites and planets. I argue that ghosts in²⁶Mg/²⁴Mg,⁸⁷Sr/⁸⁶Sr, and^206,207Pb/²⁰⁴Pb have caused erroneous cosmoradiogenic estimates of large age differences between meteorites, their special phases, and even the Moon.  相似文献   

Chemical and isotopic fractionation by grain size separates     

Donald D. Clayton 《Earth and Planetary Science Letters》1980,47(2):199-210

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