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By George Bain

SOME problems concomitant with commercial exploitation of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service depart-ment wants defects rectified and the cause determined to avoid recurrence. The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character.

Jan 1, 1940

By Jesus Garcia Iglesias, Jorge Loredo

"Abstract -The Asturian fluorspar district consists of vein and stratiform deposits where mineralization is controlled by a combination of lithological and tectonic factors.It is postulated that these fluorspar deposits have been formed under disequilibrium conditions created during circulation of ascending hydrothermal solutions along faults and other high permeability conduits. Mixing of solutions is inferred from fluid inclusion studies. Cavity filling and replacement processes are very important in localizing the ore deposits and in determining their morphology.Permian volcanic rocks in the area yield a regional positive geochemical anomaly in fluorine implying that Permian vulcanism may be a possible primary source of fluorine.On a regional scale a relationship can be established between some of the ore deposits and important tectonic lineaments. The stratiform deposits preferentially occur within a calcareous-detrital facies located at the margins of basins. These basin margins are related to important synsedimentary faults.Fluorite is the only economic mineral in these deposits. Quartz, carbonates, barite and pyrite are common minerals accompanying fluorite. Other minerals that may occasionally be present as minor components are: marcasite, chalcopyrite, fahlore, sphalerite, galena and related supergene minerals."

Jan 1, 1994

By Jorge Loredo, Jesús Garía Iglesias

"Abstract - The Asturian fluorspar district consists of vein and stratiform deposits where mineralization is controlled by a combination of lithological and tectonic factors.It is postulated that these fluorspar deposits have been formed under disequilibrium conditions created during circulation of ascending hydrothermal solutions along faults and other high permeability conduits. Mixing of solutions is inferred from fluid inclusion studies. Cavity filing and replacement processes are very important in localizing the ore deposits and in determining their morphology.Permian volcanic rocks in the area yield a regional positive geochemical anomaly in fluorine implying that Permian vulcanism may be a possible primary source of fluorine.On a regional scale a relationship can be established between some of the ore deposits and important tectonic lineaments. The stratiform deposits preferentially occur within a calcareous-detrital facies located at the margins of basins. These basin margins are related to important synsedimentaryfaults.Fluorite is the only economic mineral in these deposits. Quartz, carbonates, barite and pyrite are comnmon minerals accompanying fluorite. Other minerals that may occasionally be present as minor components are: marcasite, chalcopyrite, fahlore, sphalerite, galena and related supergene minerals."

Jan 1, 1994

By B. W. Smee

Glacial lake sediments or glaciolacustrine deposits form a significant portion of the Canadian, Scandinavian and Russian landscapes. Furthermore, 50 per cent of the Archean volcanic belts within the Canadian Shield area are covered wholly or in part by these deposits. Because of the high electrical conductivity and low hydraulic conductivity of these compact sediments, the application of geophysical (electrical) and geochemical techniques in such areas becomes a difficult task. The presence of these sediments has therefore hampered exploration for metallic sulphide deposits in some of the most important metallogenic environments of Canada. Similar problems exist in some tropical countries, such as Australia, where the overburden may be very conductive. In this paper, the extent and provenance of the glaciolacustrine deposits within the Canadian Shield are described. The geochemical and geophysical factors that hinder exploration in the clay belts are reviewed, with case histories of successful and unsuccessful applications of some of these techniques. The most successful geochemical technique used within glacial clay belts is the sampling of lodgement till beneath the clay cover, and the analysis of the heavy mineral fraction of that till. Surficial sampling has not been successfully applied. Some geophysical techniques, more specifically electromagnetic and magnetic induced-polarization techniques, have detected mineralization beneath substantially deep clay or saline overburden layers. Some suggestions have been made, such as the use of anions in hydrogeochemical surveys and the use of wide-band multi-frequency EM systems. When implemented, they will hopefully make the current geochemical and geophysical methods more effective in exploration for base metal sulphides within clay-covered terrains.

Jan 1, 1979

By M. G. Yalçin

Marbles commercially known as the Nigde- white crop out in the town of Gümü?ler, around the Çalkama Hill within the Gümü?ler Formation of the Nigde Masif of Paleozoic age. Marbles sporadically occur within the masif, however its prevalent occurrence is associated with the Gümü?ler Formation. Due mainly to its intense fractured nature, the Nigde-white marbles are used as dimension stones, crushed stones and most recently micronized calcite. Insignificant portion accounts for block use through a few quarries.

Jan 1, 2005

By S. Parker Gay

In 1967 Southern. Peru Copper Corp. was faced with the problem of developing a water supply for their new Cuajone open-pit copper mining and milling operation, at a time when the existing water system was inadequate for a proposed expansion of the producing Toquepala mine. The most probable source for additional water was considered to be the Pasto Grande basin lying 30 km north of the terminus of the pipeline. This source of supply could be developed only at substantial cost, after construction of a dam, tunnels, pumping plants, and several miles of canals. Investigation of other possible sources was undertaken, and one of these was the Huaitire alluvial fan which had been recognized on aerial photographs in 1961. Resistivity soundings on the fan provided isopach information for estimating the volume of fan sediments. In the course of carrying out these soundings, a high-resistivity layer at depth was indicated. The favored geological interpretation of this layer at the time was a tight impermeable volcanic formation, but an alternative explanation was a ground-water aquifer of high transmissibility. Geological studies just released by the Peruvian Geological Map Commission supported the latter interpretation. A diamond drill hole sunk to a depth of 725 ft on the Huaitire Pampa in June 1967 proved the absence of the expected volcanics, the presence of the sediments, and indicated that some sedimentary horizons carried artesian water. Subsequent well drilling and hydrological and geological studies show that the aquifer occurs principally in the Upper Tertiary Capillune formation, covers an extensive area on the Peruvian altiplano, discharges enormous quantities of water to a large number of canyons dissecting it, and will adequately supply most, if not all, water needs of the Cuajone operations.

Jan 1, 1973

By I. S. Parrish

As noted by McKinstry (1948), "How to deal with erratic high samples is one of the knottiest problems in ore estimation." He described a variety of approaches and methods to alleviate the problem through the averaging and weighing of assay data and by "cutting" or "clipping" of the erratic assays. Bird (1991) elaborated on ways of dealing with the nugget effect (erratics). He listed several procedures for cutting. Bird's list has been reproduced and/or added to by several authors including Vallee (1992) and Stone and Dunn (1993). Missing from each of these otherwise excellent reviews is a definition, description or guideline to recognition of an "erratic," or just where or when cutting is warranted or justified.

Jan 1, 1997

By Wayne Trudel, Lloyd McEvers, Lori Clarke, Eric Saderholm, Charles Lynn Bolin, Leroy Schutz

Newmont mine geologists in Nevada are most proficient when applying technical expertise with multi-departmental teams in three main settings. The first is value creation through near-mine discovery, development and reserve conversion. Since 1986, geologists have created substantial net asset value in developing more than 1.35 kt (43 million oz) into quality Nevada surface and underground gold reserves. The second setting is value realization by supporting mine operations with ore control, selective mining, reconciliation investigations and strategic planning. The investment of technical research on reconciliation investigations led to new concepts and practices that highlighted opportunities for large revenue and reserve gains. In 2002, more than $65 million in projected revenue was added to the Gold Quarry south layback. Kriged mine polygon construction and controlled blast heave at the Lone Tree Mine provided millions of dollars in mining efficiencies. High-quality geologic advice in selective mining at the Twin Creeks Mine helped obtain $4.3 million revenue gains throughout 2002-2003.

Jan 1, 2004

By Wayne Trudel, Eric Saderhold, Lloyd McEvers, Lori Clarke, Charles Lynn Bolin, Leroy Schutz

Editor’s note: This is the second part of a two-part series on how mine geologists added about 141t (4.53 million oz) at Newmont Mining’s gold operations in Nevada during 2003. Part one (ME, July2004, pp. 19-26) showed how cross-functional teamwork among mine geologists, engineers, metallurgists and operators added $65 million in revenues at Newmont’s Gold Quarry Mine. Part two deals with how this same cross-functional team added about 25.8 t (830,000 oz) of gold reserves and two years of life at the company’s LoneTree Mine. This was done through improved reconciliation methods, pit optimization designs and updated geotechnical parameters. Part two also discusses how Newmont’s Nevada mine personnel added about 62.2 t (2 million oz) of gold reserves at its Twin Creeks Mine, extending the mine’s life by several years. The Lone Tree Mine is a sediment-hosted, micron gold deposit. It is dominantly situated in the Golconda thrust footwall. The north-south trending Wayne Zone fault controls the highest-grade ores and

Jan 1, 2004

By K Ehrig, C Lower, V Liebezeit, M Smith, E Macmillan

"Minerals, minerals, minerals. Elements occur in the earth as minerals. If local physical, chemical and structural conditions are conducive to concentrating these minerals to sufficiently high abundances in the earth’s crust, a mineral deposit will form. If technology is available to extract metals from the minerals economically, then you have a mineral resource that will be mined and processed. Determining which minerals are present and quantifying their abundances, textural characteristics (grain size and shape) and how they are intergrown with each other is the realm of the mineralogist. Geologists use this mineralogical data to understand how the mineral deposit formed, how to find high-grade zones within the deposit and where to find other mineral deposits. Metallurgists use this data to design, operate and optimise processing facilities to extract metals from the minerals. The types, quantity and precision/resolution of the mineralogical data required by geologists and metallurgists are different, but are not mutually exclusive of each other. Fortunately, measurement technology is available that is relatively rapid, high volume and low cost, thus enabling ore and gangue mineral characterisation at a historically unprecedented scale of a mineral resource.CITATION:Ehrig, K, Liebezeit, V, Smith, M, Macmillan, E and Lower, C, 2014. Geologists and the value chain – how material characterisation by modern mineralogy can optimise design and operation of processing facilities, in Proceedings Ninth International Mining Geology Conference 2014, pp 5–14 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014

By WILLIAM BOWIE

IN most human endeavors a knowledge of the terrain is essential to the effective carrying out of projects, but no line of work is more dependent on maps than theoretical and applied geology. Maps of a kind do exist for all of the area of the United States, but most of them are crude affairs and of little use in engineering, planning, and scientific research. Topographic mapping in the United States was initiated on a national scale by the U. S. Geological Survey and the organizations that were merged in its creation to make base maps for geologists. Their work could not be effectively done then and cannot be effectively done now without maps that accurately delineate the earth's surface. The distribution of the rock masses that contain valuable mineral bodies, or that by their intrusion brought them into existence, is the first step in a study of the mineral resources of the nation. This work requires three-dimensional maps, that is, topographic maps on which the land forms are shown by contours.

Jan 1, 1938

By Kenneth N. Weaver

Portland cement can be made from relatively abundant industrial minerals and rocks, and this may explain why cement producers placed little emphasis on geology during the early days of the industry. After World War II, however, the industry began to recognize the need for geological exploration, and some of the larger companies began to build a permanent geological staff. This development had its roots in the following factors: Rapid expansion of the industry; closing of many cement plants due to inadequate raw materials; necessity for upgrading the quality of portland cement; and the increasingly large capital investment required to build new cement plants, which in turn, required a higher degree of accuracy in reserve calculations. Whereas the geologist's function during the active expansion of capacity was primarily in exploration, one of his major functions today is the development of existing reserves.

Jan 1, 1965

By J. J. Gresham

Homestake’s first links with Australia were established in 1934 but it wasn’t until 1961 that the company established a formal presence in the country. After involvement and success in iron ore and nickel, Homestake made a strategic investment in the Kalgoorlie gold operations in 1975 and now owns 50% of Kalgoorlie Consolidated Gold Mines, operators of Australia’s biggest gold mine. In 1998 Homestake acquired the major Australian gold producer Plutonic Resources, is now firmly established as Australia’s second largest gold producer and is actively seeking further opportunities for growth in the Austral-Asia region. Homestake’s success in Australia has been the result of important strategic alliances, timely investments, a long term commitment to the region and perseverance during periods of depressed commodity prices.

Jan 1, 2001

FREQUENTLY the careful engineer puts the word porphyry in quotation marks or precedes it with "so-called," when he writes of the Porphyry Copper mines. This is done by way of serving notice that he is aware that the term is not a precise one, though no one who is informed on the subject would in any event misinterpret it. The name originated from the fact that the rock containing the copper at Utah Copper, Morenci, Nevada Consolidated, and Braden-the first four to be developed-was in each instance known as porphyry. The term was convenient; and when Ray, Miami, and inspiration came along they fell into the Porphyry category even though the ore consisted essentially of a rock called schist instead of porphyry. The word is not inclusive enough; nor as a matter of fact is it sufficiently exclusive. Numerous copper deposits occur in porphyry rocks that are not Porphyry Coppers, paradoxical as it may seem. Desiring to be more accurate and at the same time to use a word that is in some degree descriptive, various engineers have adopted the expression "disseminated copper deposits." This alludes to the characteristic scattering of grains or specks of copper minerals more or less uniformly throughout the mass of the rock. Yet here again the implication is not entirely accurate, for the following reason: in some of the ores, the proportion of copper minerals "peppered" in the rock is small, compared with that which coats the walls of cracks and minute fissures; and that which is found as veinlets along planes of fracture. Many geologists have extended their interpretation of the term disseminated to include both types of mineral occurrence. One of the most striking features of the Porphyry ores is the intense shattering and fracturing that the rock underwent at some period or periods prior to the deposition of the copper

Jan 1, 1933

By Oscar F. Tangel

This paper outlines Canada's current status in world iron ore markets, and evaluates t he prospects for the future. Estimates for the production, export and consumption of iron ore are given. Canada's major market will continue to be the United States, with the European Common Market countries, Japan and the United Kingdom also forming important outlets. The advantages held by Canada's major competitors in these latter three market areas are briefly discussed

Feb 1, 1966

By Fred G. Hewett

The Cassiar orebody is located in a sill-like serpentinite body intrusive into the Devonian-Mississippian sedimentary rocks of northern British Columbia. Subsequent intrusion of the Cassiar batholith formed the McDame synclinorium and produced chrysotile asbestos. Present information indicates an orebody of approximately 16,277,000 tons amenable to open-pit mining, but continued diamond drilling will be needed to accurately define total tonnage and grade. A program has been developed at the mine to provide the required information on a daily basis, and work is continuing on more effective dollar-value prediction methods.

Jan 1, 1978

By V. D. Perry

Mineralized breccia pipes, because of their widespread occurrence and close structural relations to some of the world's great ore bodies, are objects of unusual interest for mining engineers and geologists. The literature contains many references to them, but it is questionable whether their genetic significance and economic importance have been sufficiently emphasized. The purpose here is to stress these features, relating them to the field facts, for the particular benefit of younger generations of geologists who, confronted with and sometimes confused by the growing flood of geochemical, geophysical, and other specialized research approaches, may be reassured that mappable field relations remain a foremost guide to a better understanding of ore deposits. A mineralized breccia pipe is a pre-mineral, breccia structure which has controlled the circulation and deposition of subsequently introduced mineralization. It is composed of relatively rotated angular or rounded rock fragments, set in a mineralized matrix. A pipe in plan outline may be circular, oval or approach polygonal form, with a steep to vertical axis proportionately much greater than its horizontal dimensions. The pipe is a steeply plunging, chimneylike mass of brecciated rock cemented with later minerals. Rock breaks in a variety of ways and complete fragmentation often occurs without rotation of individual pieces. A finely broken rock mass may fit into a tight jig-saw pattern, each fragment having mutually concordant boundaries with its neighbors. The result is a stockwork of innumerable reticulating cracks that, once cemented by mineralization, forms a complicated intersecting network of individually insignificant but collectively important seams and veinlets. Stockwork fracturing among its many forms takes the shape of domes of subsidence, fracture pipes, and related peripheral zones around and over breccia columns, or a combination of any of these structures. The significance of the mineralized breccia pipe is that it represents the extreme or climactic expression of a structural type which has a variety of mutations including subsidence domes, fracture pipes, and other stockwork zones all with related ancestry and similar to dissimilar characteristics. These allied and associated structures hold an answer to the fundamental question of the origin of many important ore deposits. CANANEA-TYPE LOCALITY FOR BRECCIA PIPES The Cananea district is characterized by an unusual development of mineralized breccia pipes. It is an important copper producer located in Sonora, Mexico, a short distance southwest of Bisbee, Arizona, and at the southerly limit of the great porphyry copper belt of the southwestern U.S. Cananea's rocks consist of Paleozoic quartzite and limestone capped unconformably by a thick series of volcanics including andesitic flows, tuffs, and agglomerates. These rocks have been intruded by a deep-seated granite with related basic and acid differentiates including dikes and plugs of quartz mon-zonite porphyry. Mineralization coincides with a northwesterly trending belt of these intrusives which break upward into and through the sedimentary-volcanic rock sequence. The district has weakly defined tectonic alignments in a northwesterly direction with subordinate intersecting fracture elements, but lacks important faulting or fissuring to provide throughgoing avenues for the upward circulation of mineralizing fluids. Thus, as will be discussed in subsequent paragraphs, the alternate way in which late magmatic and hydro-thermal derivatives of the parent magma reached the near-surface zone was by excavating their own breccia pipe channelways. There are numerous stages of breccia pipe development, related both in time and space to magmatic activity. A compilation of similarities and differences in various pipes suggests that proximity or remoteness of a demonstrable or inferred magmatic source provides an orderly genetic basis for describing the following representative types. Cananea Duluth Type: There are no intrusive rocks within or close to the Cananea Duluth pipe; therefore, the existence of any deep-seated magma that may have been related to its formation must be inferred. The structure is an oval-shaped ring 1200 x 300 ft in plan dimensions, cutting steeply across low angle, bedded tuffs, and other volcanics; it has been developed by drill holes to a depth of 2000 ft below the surface. The ore follows the periphery of the pipe and is composed of intensely brecciated rock which is cemented by minor galena, sphalerite, chalcopyrite, quartz, carbonates, and adularia. There is a definite vertical zoning of sulfides with less galena, continuing sphalerite, and increasing chalcopyrite at deeper levels. Within the interior of the ore ring, the brecciation becomes progressively weaker and coarser, the whole indicating relatively gentle slumping with broken, thin tuff beds pre-

Jan 1, 1961

By A. Long, A. Silverman, J. L. Kulp

Garth Crosby has written an excellent geologic description of the deposits surrounding the Gem stocks in the Coeur d'Alene district. The ore deposits in the area of the Gem stocks may hold the key to the age and mineralization history of the entire Coeur d'Alene district. A recent isotopic study10 of the Coeur d'Alene district in this laboratory illustrates that a classical geologic interpretation of these deposits, with its implications for the whole district, may lead to erroneous conclusions. For this reason it seems pertinent to submit a summary of these results and an interpretation of the mineralizing history of the Coeur d'Alene districts. Pitchblende from the Sunshine mine has been dated as 1100-1200 million years (m.y.) by Kerr and Kulp,11 and Eckelmann and Kulp.12 This pitchblende is known to predate the major sulphide introduction in the Sunshine mine, but it clearly follows the metamorphism and folding of the Belt Series. Recently, Goldich (personal communication) dated sericite from the Belt rocks as 1200 m.y. by the potassium-argon method. This date establishes a minimum Belt age if the sericite is of metamorphic origin and a maximum age if detrital. The Belt Series, therefore, is not latest Precambrian. Lead isotope ratios of galenas have been measured and model ages calculated by Bate, et all3 for the Sunshine mine, Farquhar and Cummingl4 or the Bunker Hill and Sullivan mine, and Cannonl6,18 for a few other deposits in the district. Galenas from similar deposits in Southern British Columbia have been measured by Bate, et al,23 Farquhar and Gumming,11 and Wanless and Leech." The new work in this laboratory includes leads from ten widely scattered mines north and south of the Osburn fault, and through a vertical distance of over 5000 ft (Star mine). Included in this group are the Hercules, Sunset, and Mountain Goat mines, which are adjacent to the Gem stocks. In addition, galenas from stringers which cut the Gem stocks in the Success and Sunrise mines and the Hercules hanging wall dike in the lower western portion of the Hercules mine, were included in the study. All of the above leads, except one, give model ages of 1300-1400 m.y. for the time of segregation from the parent material. The concordance of the common lead and U-Pb ages, the great horizontal and vertical uniformity of the lead ratios, the sulphur ratios of two Sunshine mine galenas and three galenas from the Edith, Page, and Hercules mines indicating average crustal sulphur, and the U23/Pb204 ratio inferred for the original lead environment, indicate that the entire mineralization of the Coeur d'Alene-British Columbia base metal belt was derived from a deep source and emplaced in the Precambrian. One sample of galena from sulphide stringers cutting the North Gem stock at the Sunrise Prospect mine gave a modern (i.e., Tertiary) lead ratio. This mine is located at the northern tip of the stock. The presence of modern lead suggests mobilization of some rock lead during the intrusion of the Gem stocks and their outliers. Larsen et al.l8 have dated the Gem stocks as Tertiary by the lead alpha method. If Coeur d'Alene mineralization was genetically related to Tertiary magma formation and intrusion

Jan 1, 1961

By F. A. Seward

A1though the expanding Eltran1 configuration has been used in induced polarization exploration for several years, there has been little application of this method to straight resistivity problems. A comparison of results of resistivity exploration by this technique versus those obtained from Wenner configuration surveys reveals a number of advantages in interpretative resolution as well as in field operation. The application of electrical resistivity to ground-water exploration is well known.= In the past a major portion of this work has been accomplished by use of one or more variations of a technique employing the Wenner3 electrode configuration. With the introduction of the frequency domain technique of induced polarization measurements, used primarily in the exploration for disseminated sulfide deposits, there arose the need for an electrode configuration by which potentials could be measured externally to the current electrode spread in order to minimize coupling between current sending and potential receiving circuits. It was also deemed desirable that the configuration would provide information laterally along profile as well as with depth. To reach these objectives the expanding dipole-dipole configuration (which probably first was used in the electrical transient method of exploration and from which the name 'Eltran' was derived) has been adapted to induced polarization exploration. The author has successfully applied the same techniques

Jan 1, 1963

By V. V. J. Sarma

Interpretation of earth resistivity data involves not only obtaining depth to interfaces but also determining the nature of formations from their resistivity characteristics. Moore's method of interpretation envisages obtaining depths to the interfaces alone. A simple method of estimating the true resistivity values of formations by applying Hummel's formula of average resistivities is proposed. The method would increase the interpretative value of Moore's method as originally proposed. For most of the earth resistivity measurements, the four-electrode configuration developed by Wennerl is employed. In principal, the method consists of energizing (Current I) the ground through two outer electrodes and measuring the resultant potential (v) between the two inner electrodes. The configuration is such that the separation (a) between any two successive electrodes is equal. The apparent resistivity (pa) for such a configuration is given by 2p- a (V/I). By increasing the electrode separation (pa vs a) curves are obtained. Ideally, a homogeneous isotropic formation underground has a characteristic resistivity. However, the field conditions do not present such ideal cases. Almost invariably, even in the same geological bed, the physical conditions are widely different at different parts in the bed. It is further shown that the penetration of the current into the ground for a given horizontal electrode separation, a, is roughly down to a depth, equal to a. It is therefore, evident that the apparent resistivity calculated from the field observations is a weighted average of the resistivities of the materials present down to this depth. With some prior knowledge about the relative dispositions of the geological formations and their physical conditions, it would be possible, by resistivity surveys, to obtain characteristic resistivities for these formations. It is, thus, that the apparent resistivity-electrode separation curves enable one to decipher the resis- tivity distribution at various depth levels and therefore the nature of the geological formations present. Both empirical and theoretical methods have been developed for determining resistivity characteristics of the various formations. The theoretical methods proposed by Tagg2 and Roman3 are derived from studies of the potential distribution on the surface due to the presence of layers of widely differing resistivities underground. The more recent methods of Wetzel and McMurry4 and Wetzel and Mooney5 are but extensions of the original Roman method of superposition. These methods suffer from lack of similarity of the actual field conditions with those of assumed conditions in developing the theory. The empirical methods such as the one developed by Gish and rooneY6 depend purely on personal observation and local peculiarities, and are applicable only for those limited areas. Out of the empirical methods, moore's7 cumulative resistivity method is still found to be applicable in several localities of differing conditions. While Reudy in 1945 adduced some theoretical justification for the method (Eve and Keys),8 Muskat9 and Mooney 10 tried to show the lack of theoretical basis for the same. It is, however, observed that the method in practice "forms a valuable means of successfully attacking the apparent resistivity curves which fail to respond to the Gish-Rooney, the Tagg or the Roman logarithmic methods" (Ramachandra Rao). 11 Comparatively good results are also reported by Melbyel2 by employing Moore's method in interpreting the resistivity results obtained for ground water in the city of Gunnison, Colo. MOORE'S METHOD As has already been pointed out, the application of the theoretical methods is time-consuming, laborious and sometimes not applicable for quick and accurate interpretation of the field data. moore7 has developed a quick method for obtaining depths to interfaces by plotting the cumulative sums of resistivities, against the corresponding electrode separations a instead of plotting the usual Pa — a curve. In this process of continuous integration, corrections for small variations in resistivities, arising due to local surface conditions or adjacent layers, are made, while large consistent variations are brought out

Jan 1, 1963