Requirements of the data to be used for resource appraisal

General principles in evaluation and selection of data to be included in computer processible files intended for use in assisting regional resources appraisal are discussed against the background of activities related to file assembly at the Geological Survey of Canada. Some of the principles discussed are currently being implemented in the assembly of files at the GSC where they apply to the specific data being collected. Others are apparent from our analysis and would be applied if different data were being collected. The files currently being assembled at the Survey are intended to assist the commodity geologists in all project-related activities, one of which is regional resource appraisal. Prior to the commencement of data assembly, each data item considered for inclusion in the data files was scrutinized by members of the Economic Geology Subdivision in order to establish how it would contribute to the overall objectives of the file. At the same time strict definitions of each item were established. The main criteria applied to each data item considered for inclusion in the files were (a) the necessity of the item to satisfy the objectives of the file within the practical limitations of the resources available and (b) the general availability of the item. The characteristics found necessary to ensure integrity of the data files were (a) uniformity—the same definitions must apply to each item of similar type, (b) consistency—analytical results should be of the same method or differences noted in order that the data may be compared, and (c) mutual exclusiveness—especially when dealing with data referring to size. Such data should never be repeated in another part of the file or be included as part of another item.This paper was presented at the International Geological Correlation Program (IGCP) Project 98 entitled Standards for Computer Applications in Resource Studies held at Loen, Norway, September 27–October 1, 1976.     

Mineral resource appraisal and mineral deposits computer files in the Geological Survey of Canada

The Geological Survey of Canada (G.S.C.) has been involved in national appraisal of resources of certain commodities for nearly two decades beginning with a national study of iron deposits in 1955. In 1972, the first national appraisal to rapidly estimate total resources of Cu, Pb, Zn, Ni, Fe, Mo, and U in Canada was carried out largely by economic geologists. This exercise produced, among other things, a better definition of G.S. C. needs for building computer files in support of mineral deposits studies and mineral resource appraisal. Objectives of this paper are threefold: (1) to outline general methodology for the kind of mineral resource appraisal carried out by the G.S.C. in 1972; (2) to identify types of information required in that appraisal; and (3) to indicate types of information on mineral deposits for which it seems advantageous for the G.S.C. to construct computer files, and how these files relate to mineral resource appraisal. Methodology is fairly straightforward for appraisal of reserves (known, measured resources), but is much more problematic for appraisal of undiscovered resources. For the latter, G.S.C. economic geologists make use of two basic concepts: the deposit model, which is a generalized deposit type, distinguished by its geological attributes and host rock environment, and containing characteristic amounts of specified commodities; and the metallogenic region, which is a geographic area of more or less homogeneous geology deemed favorable for the presence of a particular deposit model. Background information required for appraisal of undiscovered resources includes the following: (a) data on distribution and geology of Canadian deposits and occurrences; (6) data on geology of important, foreign deposits; (c) knowledge of Canadian geology, commensurate with metallogenic requirements; (d) knowledge of current theories of ore-forming processes; and (e) appreciation of the amount, location, and effectiveness of past exploration in Canada. At present, only identity, location, and certain simple geological features of Canadian deposits are considered practical for a general computer file of mineral deposits. The fundamental activity of the G.S.C. in the sphere of mineral deposits is a number of broad studies on the geology of certain commodities in Canada carried out by economic geologists. Appraisal of mineral resources is based directly on the results of those studies, and is done by the same economic geologists. Construction of G.S.C. computer files is in response to needs defined by economic geologists, mainly in the context of their broad studies.This paper was presented at the International Geological Correlation Program (IGCP) Project 98 entitled Standards for Computer Applications in Resource Studies held at Loen, Norway, September 27–October 1, 1976.     

Human perceptions of environmental degradation in a part of the Kalahari ecosystem

This paper is based on data on human perceptions of environmental degradation generated using the rapid rural appraisal approach in a part of Botswana's Kalahari environment. The data revealed a high level of respondent awareness of local resource use problems related to negative environmental change. However, respondent perceptions of the causes of, and solutions to, to environmental degradation were found to be mainly outward oriented; the possibility of local human contribution to the problem and its solution was widely down-played. The data point to the need for measures to bring about correct perceptions so that people can see where their own activities fit in the causal nexus of environmental degradation and acknowledge their power to contribute to solutions thereof.     

Preliminary isotopic studies in the Bida basin,central Nigeria

The area of the Bida basin is lacking in essential data for effective groundwater management. Hydrological studies using environmental isotopes (²H,³H,¹³C,¹⁸O) were carried out in the basin during the 1987–1988 hydrological year on samples of rainfall, streams, springs, and groundwater. The results obtained results do not indicate the presence of paleowaters; rather all groundwaters in the basin are found to be of meteoric origin as bothD and ¹⁸O values of the samples, plotted in the conventional way, align with the meteoric water line (MWL). Moreover, these data show the deeper, and apparently older, groundwater to be more depleted in the heavy stable isotopes than the shallower, relatively younger groundwaters, indicating recharge under cooler climatic conditions for the former. Measured tritium values range from 0.7 to 23.8 TU and show a variation with both depth and lithology, while at the same time indicating that active recent recharge is taking place basin-wide. The few¹³C data available were used to illustrate the effect of pumping on the carbonate geochemistry of the groundwaters. Also, the stable isotope data from the basin were compared with similar data from other parts of the country to show the continental effect.     

Semi-empirical Gibbs free energy formulations for minerals and fluids for use in thermodynamic databases of petrological interest

The P–T partition function in statistical thermodynamics can be used to derive semi-empirical formulations of the Gibbs free energy G for minerals and fluids. Parameterization of these equations includes simultaneous regression of experimental heat capacity and molar volume data, allowing fitting, appraisal and optimization of various data sources, as required in the construction of internally consistent petrological data bases. This approach can also be extended to minerals with -transitions and to fluids by considering the Gibbs free energy as a function of pressure P, temperature T and an ordering parameter X, so that accurate modelled representation and extrapolation of the thermodynamic properties of large numbers of petrologically significant minerals and coexisting fluids can be attained. The ordering parameter is chosen to denote the equilibrium mole fraction (thermodynamic probability) of ordered clusters (structural units) in a substance when G(T,P, X)=min. The procedure is tested on existing experimental data for the system MgO–SiO₂–H₂O. The proposed Gibbs free energy formulation permits thermodynamic properties of minerals, fluids and phase equilibria to be described and extrapolated over a wide range of pressure (0–800 kbar) and temperature (20–3000 K), thus allowing effective use in thermodynamic data bases of petrological interest.     

Toward an expert system for identification of minerals in thin section

Minerals may be identified by optical inspection and x-ray diffraction analysis. Full and correct identification, however, requires experience and extensive knowledge of mineral characteristics and association. Computer systems designed to approach levels of human expertise in similarly complex identification tasks have become increasingly effective with the application and refinement of various Artificial Intelligence (AI) techniques. These knowledge-based systemsuse the skills, knowledge, and rules of thumb that distinguish the expert from the knowledgeable layman to emulate human expertise. They also may be modified to serve a tutorial role whereby a nonexpert's approach to the task may be compared with that of the expert (system), and criticized accordingly. Such a knowledge-based system capable of identifying minerals from their optical characteristics is being developed at the University of Reading.     

A petrological and geochemical reappraisal of the Mesoproterozoic diamondiferous Majhgawan pipe of central India: evidence for transitional kimberlite – orangeite (group II kimberlite) – lamproite rock type

Summary The Mesoproterozoic diamondiferous Majhgawan pipe of central India is re-examined in the light of new and recently published petrological, geochemical and isotope data. This investigation reveals that its tectonic setting is similar to that of lamproites and orangeites (Group II kimberlite of southern Africa) and not that of a typical kimberlite. The petrography and mineralogy are comparable to lamproite and to some extent to orangeite, whereas the major element geochemistry is more akin to that of kimberlite. Trace element geochemistry is closer to that of lamproite but Nd isotope systematics are atypical of lamproite or orangeite. The inferred petrogenesis of the Majhgawan pipe is also similar to that of other such potassic metasomatised mantle magmas without any strong affinity to a particular clan/group.It is demonstrated in this study that the Majhgawan pipe shares the petrological, geochemical and isotope characteristics of all three rock types. It is therefore suggested to constitute a transitional kimberlite–orangeite (Group II kimberlite)–lamproite rock. The existence of such transitional magmas in space and time in other cratons, outside India, is also highlighted. The name majhgawanite is proposed for this rock – keeping in mind the antiquity of the Majhgawan pipe, its intriguing petrological and geochemical characteristics and also on the basis of Indias legacy for introducing diamond to the world – to designate such mafic potassic-ultrapotassic transitional rock types so as to distinguish them from the classical kimberlite, lamproite or orangeite.It is concluded that the correlations between kimberlite petrography, geochemistry and isotopic types (viz., Group I and II), as established for kimberlites in southern Africa, need not be necessarily valid elsewhere. Hence, the recommendations of I.U.G.S. on classification of kimberlite, orangeite and lamproite are clearly inadequate when dealing with the transitional mafic potassic ultrapotassic rocks. It is further stressed that mineralogical, geochemical and isotopic aspects of mafic potassic-ultrapotassic rocks need to be considered in unison before assigning any name as the nomenclature of such exotic and rare alkaline rock types invariably implies economic and tectono-magmatic (regional) significance.     

The Geochemistry of Ultramafic to Mafic Volcanics from the Belingwe Greenstone Belt, Zimbabwe: Magmatism in an Archean Continental Large Igneous Province

The evolution of the late Archean Belingwe greenstone belt,Zimbabwe, is discussed in relation to the geochemistry of theultramafic to mafic volcanic rocks. Four volcanic types (komatiite,komatiitic basalt, D-basalt and E-basalt) are distinguishedin the 2·7 Ga Ngezi volcanic sequence using a combinationof petrography and geochemistry. The komatiites and D-basaltsare rocks in which isotopic systems and trace elements are depleted.Chemical variations in komatiites and D-basalts can be explainedby fractional crystallization from the parental komatiite. Incontrast, komatiitic basalts and E-basalts are siliceous anddisplay enriched isotopic and trace element compositions. Theirchemical trends are best explained by assimilation with fractionalcrystallization (AFC) from the primary komatiite. AFC calculationsindicate that the komatiitic basalts and E-basalts are derivedfrom komatiites contaminated with 20% and 30% crustal material,respectively. The volcanic stratigraphy of the Ngezi sequence,which is based on field relationships and the trace elementcompositions of relict clinopyroxenes, shows that the leastcontaminated komatiite lies between highly contaminated komatiiticbasalt flows, and has limited exposure near the base of thesuccession. Above these flows, D- and E-basalts alternate. Thekomatiite appears to have erupted on the surface only in theearly stages, when plume activity was high. As activity decreasedwith time, komatiite magmas may have stagnated to form magmachambers within the continental crust. Subsequent komatiiticmagmas underwent fractional crystallization and were contaminatedwith crust to form D-basalts or E-basalts. KEY WORDS: komatiite; crustal assimilation; Belingwe greenstone belt; continental flood basalt; plume magmatism     

Guidelines for international data collection and resource assessments and analyses

The ever-increasing world interdependency required to provide the basic energy and mineral commodities needed by society, has created a need to assess, on a common basis, the location, number, and quality of deposits of natural resources. In order to evaluate and compare the resource potential of any area, two major factors must be considered: (1) the type of commodity being evaluated and (2) the specific parameter (reserves or resources) which is being defined. Each commodity or parameter being studied requires a separate methodology for analysis and different basic data. Porphyry copper deposits must be treated differently from stratabound copper deposits or massive sulfide deposits of copper. Similarly, oil and gas deposits associated with stratigraphic traps must be treated differently from those associated with salt domes. Resource assessments attempt to estimate the aggregate resource potential of an area whereas resource analyses attempt to define the specific characteristics of the individual occurrences which comprise the aggregate resource potential. Assessment programs may range from a national inventory of known deposits and occurrences to detailed studies which require an extensive integration of geological, geochemical, and geophysical data. Examples of national inventories are the small mine inventory of Bolivia and presently operating resource programs in Turkey and Argentina. Detailed programs of assessment include the AMRAP (Alaska Mineral Resource Appraisal Program) program and studies in the Coeur d'Alene district and Ely, Nevada. Worldwide resource analysis is a rapidly expanding field of endeavor necessitated by the need to more clearly define the characteristics of known deposits and to provide quantitative estimates of hypothetical and speculative resources. Studies presently underway deal with the development of search and occurrence models, field size distributions of energy resources, tonnage and grade relationships of mineral deposits, the zone of influence of exploratory drill holes, and models of the exploration process.This paper was presented at the International Geological Correlation Program (IGCP) Project 98 entitled Standards for Computer Applications in Resource Studies held at Loen, Norway, September 27–October 1, 1976.     

CO2-CO fluid inclusions in a composite peridotite xenolith: implications for upper mantle oxygen fugacity

Fluid inclusions occur in a composite xenolith from the Lunar Crater Volcanic Field, Nevada, U.S.A. The xenolith is an amphibole-bearing wehrlite that is cut by an andesine-amphibole vein. The compositions of individual fluid inclusions in both portions of the xenolith have been determined using microthermometry and micro Laser-Raman spectroscopy. Fluids in the host wehrlite are nearly pure CO₂ (>99 mol%) whereas those in the vein contain from 8.5 to 12.0 mol % CO in CO₂. Chemical modelling shows that the composition of the vein fluids at T _room is representative of the composition at the high P, T conditions of trapping. Graphite has not been observed by optical microscopy in any of the fluid inclusions. Graphite is probably absent (although stable at T<800° C) most probably because of the kinetically unfavorable CO decomposition reaction and rapid quenching. By combining the measured fluid compositions with fluid P-V-T data and the chemical equilibrium CO₂CO +1/2 O₂, we have calculated the oxygen fugacity of the fluid inclusions at 1200° C: log 8.6 (vein) and –6 (host). If the of the fluid in the vein represents that in equilibrium with the magma that crystallized to produce the vein, then the of the basalt magma is near QFM at 1200° C and 10.3 kbar. This is similar to values reported for extrusive basaltic lavas. If the much lower intrinsic oxygen fugacity-values for divines and spinels from alkali basalt nodules are representative of upper mantle conditions, then oxidation of basaltic magmas must occur in the upper mantle prior to ascent to the surface. Implications for the origin of CO₂-rich fluids and carbon isotope geochemistry are also discussed.     

Three-dimensional graphic display of disconnected bodies

Lett= (x, y, z) be an ore grade function sampled at the nodes of a three dimensional regular grid. Ift ₀ is a given cut-off, the ore deposit may be considered to be constituted by all the points (x, y, z) such that (x, y, z)>t ₀. In fact, the ore deposit may be constituted by one or several disconnected bodies and two algorithms to display these bodies may be considered. The first consists in drawing intersections of the bodies with a series of equidistant parallel planes. The second consists in covering their surface with painted triangles. In both cases, how to remove hidden parts of the drawing is shown. An interactive approach of the problem also is considered.This paper presented at Emerging Concepts, MGUS-87 conference, Redwood City, California, 13–15 April 1987.     

On the occurrence of eclogite in Western Norway

Recent experimental data show that eclogites may form in the crust under conditions where total pressure exceeds water pressure. The regional distribution of eclogites in Western Norway and their association with crustal rocks makes their formation in the crust the most attractive hypothesis. Before a mantle origin should be assigned to any rock within this eclogite and garnet peridotite area it should be demonstrated that their country rocks are in a metamorphic state incompatible with the load pressures required for eclogite stability. Criteria for ascertaining eclogite formation in the crust are discussed.Publication no. 8 in the Norwegian geotraverse project.     

Evaluation of ferrous and ferric Mössbauer fractions

The Mössbauer fractions f for various ferrous- and/or ferric-containing oxides and oxyhydroxides, silicates and carbonates were evaluated from the experimental temperature dependence of their center shifts, using the Debye approximation for the second-order Doppler shift. It is concluded that ferrous ions exhibit a lower fraction as compared to ferric ions. Using standard mixtures of -Fe₂O₃ with selected Fe²⁺ or Fe³⁺ compounds, it is found that the calculated Fe³⁺ f values are somewhat overestimated with respect to those of Fe²⁺. Possible explanations for this shortcoming are discussed and it is suggested that a different temperature dependence of the intrinsic isomer shift is the most likely reason. This suggestion is corroborated by analyses of hematite and hedenbergite data which are available for temperatures up to 900 K and 800 K respectively.     

Nd and Sr isotopic systematics of central Australian granulites: chronology of crustal development and constraints on the evolution of lower continental crust

Nd and Sr isotopic data are reported for a granulite terrain in the Proterozoic Arunta Block of Central Australia. Sm-Nd data from a wide range of rock types define a crust formation age of 2,070±125 Ma and provide further evidence for voluminous crustal growth in the Proterozoic. An _Nd value of +1.5±0.8 indicates a depleted mantle source for this crustal segment and there is no evidence for a large component of significantly older sialic crust. Field relationships, geochemistry and Rb-Sr data for mafic and felsic granulites indicate that intracrustal differentiation and polyphase deformation were followed by granulite facies metamorphism (Rb depletion) at 1,800 Ma. Rb-Sr data for strongly retrogressed granulites define an age of 1,700 Ma which is interpreted as the time of retrograde biotite growth. Partial melting at the presently exposed crustal level and anatexis at deeper crustal levels were broadly coeval with the retrograde metamorphism. Sm-Nd and Rb-Sr isotopic systematics of minerals indicate that the terrain cooled slowly, did not experience significant uplift until 1,000 Ma and remained at temperatures above 320° C until the late Palaeozoic. The mineral data are consistent with geological relationships and petrological evidence for a prolonged period of isobaric cooling followed by uplift late in the metamorphic evolution of the terrain. The granulite protoliths appear to have formed in a rift which closed within 280 Ma of initial separation. Deformation and granulite facies metamorphism at 1,800 Ma are interpreted to be a consequence of collision between the continental blocks which defined the rift. Regional retrogression and granitoid magmatism at 1,700 Ma are attributed to underthrusting of the granulites by lower grade rocks in the final stages of collision. Subsequent events in the cooling and uplift history appear to have been controlled by the presence of long-lived major faults in the crust and a prolonged history of episodic compression in the continental lithosphere. The results of this study suggest that granulite terrains, in general, cannot be equated with lower continental crust but instead represent assemblages of (mainly) supracrustal rocks which in some instances have been involved in major collision events.Abbreviations Opx orthopyroxene - Cpx clinopyroxene - Plag plagioclase - Hb hornblende - Ox opaque oxide - Bi biotite - Ap apatite - Zir zircon - Gt garnet - 2°CA secondary clinoamphibole - Qtz quartz - Ol olivine - Sp spinel - Se serpentine - Ep epidote - Kf alkali feldspar - Mz monazite - Sph sphene - Sill sillimanite - Rut rutile - Cd cordierite - Sphal sphalerite - Ms muscovite - Act actinolite - Cc calcite - Scap scapolite - Cor corundum - Xen xenotime - Sapph sapphirine - Ged gedrite - All allanite - Clh clinohumite - Dol dolomite - Mt magnetite - Ghn gahnite - Gal galena     

Comparison of size effect for different types of strength tests

SummaryComparison of Size Effect for Different Types of Strength Tests Different theories have been proposed to explain and predict size effect. Notable is Weibull's Weakest link theory. In addition various theories have been founded on strain energy consumption at failure. The present paper suggests a theoretical approach, based on energy considerations and mode of failure, which holds for diverse types of mechanical testing. Maximum size effect is assumed to be associated with failure through development of a single fracture plane and a lack of size effect is associated with failure affecting a volume of material. The quantitative expression of the theoretical approach is based on the relationship between load at failure (P) and cross sectional area of the specimen (A):P=KA ⁿ wheren expresses size effect andK is a constant.The theoretically lowestn-value equals 0.75 expressing maximal size effect whereas the theoretically highestn-value is 1.00 expressing lack of size effect.n-values evaluated from published data for various mechanical tests indeed lie between these limits and appear to be related to type of test, material properties and specimen shape. Point load tests and Brazilian tests are generally associated with large size effects. This may be attributed to the test conditions which promote development of single fracture planes. On the other hand relatively small size effects are generally found for uniaxial compression tests. Failure in these tests characteristically occurs through multiple fracturing and crushing and therefore affects a volume of material rather than a single plane. Brittleness seems to be associated with large size effects and ductility with small size effects.With 4 Figures     

Refined relationship between the position of the fundamental OH stretching and the first overtones for clays

The aim of this paper is to determine a relationship between the wavenumbers of the first OH-stretching overtones (W_2OH) and the wavenumbers of the OH-stretching fundamentals (W_OH) to help to interpret the near-infrared (NIR) spectra. The first overtone (2OH) bands appear at wavenumbers less than twice those of the fundamental bands (OH), due to the anharmonic character of vibrations, X = W_2OH/2 - W_OH, with X being the anharmonicity constant. Talc samples with various crystal chemistries are used to solve the equation and the experimental data are well fitted with X = –85.6 cm^–1. As far as the authors are aware, it is the first time that the anharmonicity constant for the OH-stretching vibrations is determined for phyllosilicates. The anharmonicity constant remains almost unchanged for several types of clay samples. Therefore the relation, established from talc samples because their absorption bands are narrow and their wavenumber range of OH vibrations is wide, can be used for any other clay minerals.     

Areal value assessment of the mineral resources endowment of Israel

The achievements of the mineral industry of Israel and an overall reconnaissance of the natural resources endowment of the country have been evaluated by the areal value estimation method, using the COMOD software package. In broad terms, the evaluation relies on geological variables obtained from quantifying the geological map of a region and on cumulative past production records, which, when prorated per unit area, yield a series of unit regional values (u.r.v.)measurements for individual commodities, resource sectors, and total resources. The two groups of variables facilitate conducting comparisons with other well-developed and/or geologically similar regions from which the future potential of the region, with respect to both overall endowment and individual commodities, can be assessed. The model underlying this appraisal method assumes that all regions above a size of about 5,000 sq kms are equally valuable with respect to total endowment in natural resources, regardless of inherent geological characteristics. To date, several areal value estimation studies have been carried out for 11 different countries, encompassing a total of 111 politically-administratively defined regions. These studies provide an adequate information base for between-region comparisons. The individual states of the United States, constituting what can be regarded as well-developed regions, may serve as an expectation for all such comparisons. The distribution of the u.r.v. of total resources of the individual states is lognormal with a geometric mean of 54,954 1967 U.S. dollars per square kilometer. Based on the above assumption, this value can serve as a conservative estimate for the total output any region can be expected to produce. Thirty different mineral commodities are known to exist in Israel. Of these, 19 are economically exploited and the remaining 11 are at present uneconomical mineral occurrences. Past production records have been obtained and assembled for 14 of the exploited commodities. From these records, a number of statistics were computed to evaluate the development of the mineral industry of the country and its future potential. In absolute figures, the overall cumulative production has been rather small, amounting to only 1,679.8 million deflated 1967 U.S. dollars (equivalent to 2,082 million current U.S. dollars or 10,260 million current Israeli pounds). Only bromine, potash, and phosphate are of worldwide significance, amounting respectively to 10, 2.9, and 1 percent of the world production in 1977. Construction materials, with the longest production history, have been the most valuable, accounting for 53.6 percent of the total cumulative output. They are followed by nonmetals (34.7 percent),metals (8 percent)and fuels (3.7 percent).The value-ranking of individual commodities and their respective contribution to the total cumulative output is: cement, 35 percent; potash, 19 percent; stone, 15 percent; phosphate, 11 percent; copper, 8 percent; sand and gravel, 4 percent; bromine, 3 percent; petroleum, 2.5 percent; natural gas, 1 percent; periclase, 0.7 percent; salt, 0.4 percent; and glass sand, 0.2 percent. Total annual output for the period 1948–1977 exhibited a constant growth with no indication of approaching a plateau of diminishing returns. As new commodities became exploited, the share of constructional materials in the total output gradually declined from 100 percent in 1948 to 45 percent in 1977. The contribution of the mineral industry to the annual gross national product rose steadily from 0.55 percent in 1951 to 2.2 percent in 1964. Thereafter, it fluctuated around an average of about 1.8 percent. Total output and production of constructional materials correlate very highly with both gross national product (GNP)and population size. However, when only the annual changes in these variables are considered, the correlation coefficients are found to be insignificant. The u.r.v. of Israel (with an area of 20,700 sq kms and a population of 3,653,000)is 81,154 deflated 1967 U.S. dollars per sq km. It exceeds the expected value for well-developed regions. It can therefore be concluded that Israel is not exceptionally poor in natural resources, as is commonly felt. On the other hand, its high u.r.v. also implies (unfortunately)that the development potential of its mineral industry is rather limited. The u.r.v. estimates, which are based on area alone, can be refined to some degree by considering the geological characteristics of the investigated area. The geological composition of the country was quantified by point counting the geological map, using a grid network of 40.3 sq km cells. Each map unit was assigned to one of 65 standard time-petrographic units. This sampling density results in the recognition of 11 time-petrographic units (instead of 15, which are actually present).Based on linear statistical association between mineral resource diversity and geological diversity established for the states of the United States, Israel can be expected to possess 31 different commodities. Since only 19 have thus far been exploited, Israel can be expected to produce 12 additional commodities. The identity of these missing resources can be inferred by examining the inventory of commodities produced in other regions with a similar geological framework and by evaluating the potential of the 11 noneconomical mineral occurrences, which have already been discovered in the country. The geology of Israel was compared to 12 other regions; of these Egypt, Libya, Sudan, and Sinai were found to be most similar to Israel, each having 8 or 9 time-petrographic rock types in common with Israel, 7 of which are identical. Based on these comparisons and on additional information from other sources, it appears that the commodities that are more likely to be produced in the foreseeable future include manganese, feldspar, uranium (from phosphates),lignite, oil shale, and iron. The mineral industry of Israel accomplished quite significant achievements in the course of its modern history of only 35 years. These resulted from concerted national exploration and development efforts, which were supported by massive governmental capital investments. The areal value method of mineral resources appraisal is based on a cybernetic black box system model in which the degree of commitment derived from the socioeconomic infrastructure is viewed as the driving agent in converting the inherited geological characteristics of the region into economic marketable mineral commodities. The case history of Israel provides a strong substantiation for this generalized system model.     

Estimating quartz fabrics from piezoelectric measurements

An aggregate of piezoelectric minerals may itself be piezoelectric if the minerals are suitably aligned. Thus quartz-bearing rocks may be piezoelectric, since quartz is one such mineral. It has been shown that some rocks do possess this effect, termed a piezoelectric fabric (Bishop, 1981). The type of piezoelectric fabric may be determined by matching experimental data to theoretical models of piezoelectric fabrics. These theoretical models of pure quartz aggregates are derived by considering the symmetry of the preferred crystallographic directions of the aggregate grains. From the symmetry, the piezoelectric matrix of the model may be determined. The best-fitting model and the orientation of its fabric is obtained by equating the experimental data to each model in turn. For each model, the best fitting fabric orientation is determined by using an inversion routine. If the experimental data are due to a piezoelectric fabric and not to some random or nonpolar distribution of grains, the fabric type (c-axis point maximum or large-circle girdle) and its orientation with respect to the specimen may be determined. The positions and polarities of the quartz a-axes are also specified. A statistical examination of results from a quartz-mylonite shows that the problem of piezoelectric model fitting is well posed, in that the Eulerian angles that specify the fabric orientation are fairly independent important parameters and a sufficiently close fit of the model to the data can be obtained to determine the fabric.     

Origin and evolution of 2 Ga old carbonatite complex (Ihouhaouene,Ahaggar, Algeria): Nd and Sr isotopic evidence

Associated syenitic rocks and carbonatites from Ihouhaouene, Algeria, have been investigated for their Sr and Nd isotope and trace element geochemistry. A zircon U-Pb emplacement age (1994 +22 -17 Ma) has been obtained from the carbonatites. The REE characteristics, among which the significant and approximately constant negative Eu anomaly and the evolution of (La/Ce)N and (Yb/Lu)N ratios which increase sympathetically with total REE abundances, are considered to be of purely magmatic origin. They are used to constrain the genetic links between syenites and carbonatites. Sr and Nd isotopes suggest a similar source for carbonatites and syenites, which is enriched compared to a chondritic reference: Nd(T)=-6.4 to -8.6 and ISr(T)=0.7097. These features are interpreted as evidence of contamination of a mantle-derived magmatic precursor by continental crust, occurring in a magmatic chamber.