Academic literature on the topic 'Pearce Element Ratio'

It has been nearly fifty years since Tom Pearce devised a type of element ratio diagram that isolates the effects of crystal fractionation and accumulation (sorting) hidden in the chemistry of a suite of igneous rocks. Here, we review the guiding principles and methods supporting the Pearce element ratio paradigm and provide worked examples with data from the Mauna Ulu lava flows (erupted 1970–1971, Kilauea Volcano, Hawaii). Construction of Pearce element ratio diagrams requires minimum data; a single rock analysis can suffice. The remaining data test the model. If the data fit the model, then the model is accepted as a plausible or likely explanation for the observed chemical variations. If the data do not fit, the model is rejected. Successful applications of Pearce element ratios require the presence and identification of conserved elements; elements that remain in the melt during the processes causing the chemical diversity. Conserved elements are identified through a priori knowledge of the physical-chemical behaviour of the elements in rock-forming processes, plots of weight percentages of pairs of oxides against each other, or by constant ratios of two elements. Three kinds of Pearce element ratio diagrams comprise a model: conserved element, assemblage test, and phase discrimination diagrams. The axial ratios for Pearce ratio diagrams are combinations of elements chosen on the basis of the chemical stoichiometry embedded in the model. Matrix algebra, operating on mineral formulae and analyses, is used to calculate the axis ratios. Models are verified by substituting element numbers from mineral formulae into the ratios. Different intercepts of trends on Pearce element ratio diagrams distinguish different magma batches and, by inference, different melting events. We show that the Mauna Ulu magmas derive from two distinct batches, modified by sorting of olivine, clinopyroxene, plagioclase and, possibly, orthopyroxene (unobserved).RÉSUMÉIl y a près de cinquante ans Tom Pearce a conçu un genre de diagramme de ratio d’éléments qui permet d’isoler les effets de la cristallisation fractionnée et de l'accumulation cristalline (tri) au sein de la chimie d'une suite de roches ignées. Dans le présent article, nous passons en revue les principes et les méthodes étayant le paradigme de ratio d’éléments de Pearce, et présentons des exemples pratiques à partir de données provenant de coulées de lave du Mauna Ulu (éruption 1970–1971 du volcan Kilauea, Hawaii). La confection des diagrammes de ratio d’éléments de Pearce requière un minimum de données; une seule analyse de roche peut suffire. Les données restantes servent à tester le modèle. Si les données sont conformes au modèle, alors le modèle est accepté comme explication plausible ou probable des variations chimiques observées. Si les données ne correspondent pas, le modèle est rejeté. Les applications réussies des ratios d’éléments de Pearce requièrent la présence et l'identification d’éléments conservés; éléments qui demeurent dans la masse fondue au cours des processus causant la diversité chimique. Les éléments conservés sont identifiés par la connaissance a priori du comportement physico-chimique des éléments dans les processus de formation des roches, le positionnement sur la courbe des pourcentages pondérés de pairs d'oxydes les uns contre les autres, ou par des ratios constants de deux éléments. Trois types de diagrammes de Pearce de ratio d’éléments constituent un modèle: élément conservé, test d'assemblage, et diagrammes de phase discriminant. Les ratios axiaux pour les diagrammes de ratio d’éléments de Pearce sont des combinaisons d'éléments choisis sur la base de la stœchiométrie inhérente au modèle. L’algèbre matricielle, appliquée à des formules minérales et à des analyses, est utilisée pour calculer les ratios axiaux. Les modèles sont vérifiés en utilisant les nombres d’élément des formules minérales dans les ratios. Différentes intersections dans les diagrammes de ratios d’éléments de Pearce distinguent différents lots de magma et, par inférence, différentes coulées. Nous montrons que les magmas de Mauna Ulu proviennent de deux lots distincts, modifiés par l’extraction de l'olivine, de clinopyroxène, de plagioclase et, éventuellement, orthopyroxène (non observé).

Exploration companies commonly rely on geochemistry to identify alteration of distinctive geochemical and mineralogical character, surrounding metal sulphide deposits that were precipitated from hydrothermal fluids. However, examination of raw analytical data is prone to error due to closure effects and the difficulty in removing the effects of background variation in unaltered rocks from the variations imposed by later hydrothermal alteration. Closure can be avoided by using ratios, or by utilising mass balance approaches based on fixing volume, mass or concentration changes between samples of parent and daughter lithologies. Using a parent-daughter approach is limiting, because only pairs of samples can be compared at any one time and because an unaltered equivalent must be produced for each sample examined in this way. Pearce Element Ratio analysis and General Element Ratio analysis (PER and GER) are not restricted in this fashion, and are more amenable to interrogation of large data sets. PER and GER are also capable of decoupling background variation from that variation due to hydrothermal alteration. Furthermore, these ratio methods are readily applied to commercially derived lithogeochemical assays. In this study, various analytical methods and interpretive techniques (including PER and GER) have been applied to identify alteration in rocks around the Century and Elura Zn-Pb-Ag deposits, and to assess whether primary ore-related alteration effects can still be identified once altered rocks have been subjected to weathering. Ratios of trace elements over a conserved element have been used to generate a suite of pathfinder elements for each deposit. Elements enriched in host rocks around both deposits include the economic metals Zn, Pb and Ag, along with Rb and Tl. Sodium is ubiquitously depleted in altered rocks. Other elements in the pathfinder suites are distinctive to each deposit type, and include a number of major and trace elements that are added or removed from the rocks around the mineralised zones. For example, Sb and As are enriched in rocks around Elura mineralisation while Ge and Cd are enriched in samples around Century deposit. Iron carbonate development accompanied by potassic alteration, the destruction of albite and the absence of chlorite are the dominant mineral alteration effects at both deposits. PER and GER diagrams have been used to quantify the intensity of this alteration and allow lithogeochemistry to be used to vector towards high intensity alteration, which is adjacent to Century and Elura mineralisation. These ratio methods are applied to both visibly and cryptically altered rocks at both deposits, and have a very high degree of success in classifying alteration in unweathered rocks. The following simple PER ratios indicate proximity to Elura mineralisation: Ca/C, K/Al for shales, K/(Al-Na) for siltstones/sandstones. The following simple PER ratios indicate proximity to Century mineralisation: Mn/Ti, Mg/Ti and Fe/Ti vs C/Ti, K/Ti vs Al/Ti, K/Ti vs (Al-Na)/Ti. Pathfinder elements can be overlain onto PER and GER diagrams to aid in ranking the prospectivity of samples, and to assess mineral hosts for individual pathfinder elements. Weathering destroys most indicators of alteration in the Elura area, while alteration signatures are better preserved in host rocks around the Century deposit.

Data Warehouses are widely used for supporting decision making. On Line Analytical Processing or OLAP is the main vehicle for querying data warehouses. OLAP operations commonly involve the computation of multidimensional aggregates. The major bottleneck in computing these aggregates is the large volume of data that needs to be processed which in turn leads to prohibitively expensive query execution times. On the other hand, Data Analysts are primarily concerned with discerning trends in the data and thus a system that provides approximate answers in a timely fashion would suit their requirements better. In this chapter we present the Prime Factor scheme, a novel method for compressing data in a warehouse. Our data compression method is based on aggregating data on each dimension of the data warehouse. Extensive experimentation on both real-world and synthetic data have shown that it outperforms the Haar Wavelet scheme with respect to both decoding time and error rate, while maintaining comparable compression ratios (Pears and Houliston, 2007). One encouraging feature is the stability of the error rate when compared to the Haar Wavelet. Although Wavelets have been shown to be effective at compressing data, the approximate answers they provide varies widely, even for identical types of queries on nearly identical values in distinct parts of the data. This problem has been attributed to the thresholding technique used to reduce the size of the encoded data and is an integral part of the Wavelet compression scheme. In contrast the Prime Factor scheme does not rely on thresholding but keeps a smaller version of every data element from the original data and is thus able to achieve a much higher degree of error stability which is important from a Data Analysts point of view.

This paper provides a roadmap of development in the thermal and fabrication aspects of microchannels as applied in the microelectronics and other high heat-flux cooling applications. Microchannels are defined as flow passages that have hydraulic diameters in the range of 10 to 200 micrometers. The impetus for microchannel research was provided by the pioneering work of Tuckerman and Pease [1] at Stanford University in the early eighties. Since that time, this technology has received considerable attention in microelectronics and other major application areas, such as fuel cell systems and advanced heat sink designs. After reviewing the advancement in heat transfer technology from a historical perspective, advantages of using microchannels in high heat flux cooling applications is discussed, and research done on various aspects of microchannel heat exchanger performance is reviewed. Single-phase performance for liquids is expected to be still describable by the conventional equations; however the gas flow may be influenced by the rarefaction effects. Two-phase flow is another topic that is still under active research. The evolution of research into microchannel heat sinks has paralleled the advancements made in microfabrication technology. The earliest microchannels were built using anisotropic wet chemical etching techniques based on alkali solutions. While this method has been exploited successfully, it does impose certain restrictions on silicon wafer type and geometry. Recently, anisotropic dry etching processes have been developed that circumvent these restrictions. In addition, dry etching methods can be significantly faster and, from a manufacturing standpoint, create fewer contamination and waste treatment problems. Advances in fabrication technology will continue to fuel improvements in microchannel heat sink performance and cost for the foreseeable future. Some fabrication areas that may spur advances include new materials, high aspect ratio patterning techniques other than dry etching, active fluid flow elements, and micromolding.