CHAPTER 6 METHODS OF URANIUM EXPLORATION
| Jurisdiction | United States |
(Nov 1976)
METHODS OF URANIUM EXPLORATION
Rocky Mountain Energy Company
Denver, Colorado
INTRODUCTION
Uranium exploration is profit motivated; it has but one objective: to find uranium ore. Successes are infrequent but the return can be high. Financiers are often loath to fund this often inadequately explained phase of the mining business in which results are uncertain and, at best, will not return a profit for years. But it provides the essential base for a mining venture, for with no reserves there can be no production. It is the aim of this paper to explain the operating philosophies, strategies and methodologies of this preliminary phase of uranium mining.
Exploration geology is not a primary science but a combined use of chemistry, physics, geography, hydrology and mathematics guided by imaginative extrapolation. The essential ingredients of any exploration program are imagination, experience, planning, time and money.
In the United States, most major companies conduct both "grass roots" and district exploration. "Grass roots," or reconnaissance exploration, is the prospecting and evaluation of frontier areas removed from producing districts or mines. A typical program involves identifying a uranium-rich area or province and, using one or more "working hypotheses," gather evidence of uranium migration and deposition. District exploration is the search for similar deposits near a producing mine or mines, or the detailed exploration following a discovery in a "grass roots" program.
The major districts of the United States were discovered in the 1950's, and since that time the great majority of exploration has been in or near these sandstone-type districts of south Texas; the Colorado Plateau in Colorado, Utah and New Mexico; and in the Wyoming basins. Working hypotheses or ore-genesis concepts have been progressively
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derived from empirical evidence as the districts became better known through mining and exploration. Virtually all of the limited "grass roots" exploration in the United States has been in other sandstone areas using these same conceptual models.
Recent major discoveries in very different granite * and metamorphic host rocks in Canada, Australia and South Africa have caused somewhat of a revolution in the conceptual thinking of U. S. uranium geologists. No longer are sandstones the only environment considered; vast new horizons of potential have become apparent. The concern caused by declining discovery rates in the traditional sandstonetype districts is being mitigated by optimism that new environments and new districts will be discovered in the United States as well.
Now let us examine how this mix of philosophies and concepts combines with an exploration organization and its techniques to create a meaningful program.
OBJECTIVES, STRATEGY AND PLANNING
An individual company's approach to exploration is dependent upon a number of key factors. Short and long-range objectives, finances, experience, staff, degree of risk acceptance and company background will determine strategy—a quicker return through the usually greater expenditures in a known district (look for elephants in elephant country), or, if time, patience and experience permit, a "grass roots" program.
Contrary to what you may have been told, it is important to plan exploration! Although the time and form of specific events and phases cannot be predicted, there is a logical sequence of study, data collection and evaluation that considerably improve the odds of success over haphazard exploration. Later I will discuss the important elements of each phase, but first let's look at the progression of a well-founded "grass roots" exploration program to provide a background for understanding procedures and techniques:
I. Research-----Concepts, potential regions, methodology
II. Reconnaissance-----Uranium source, possible host rocks or structures.
III. Prospecting-----Evidence of uranium migration and deposition on regional scale. Outline broad anomalies.
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IV. Regional Exploration-----Evaluate anomalies, identify high potential situations.
V. Prospect Exploration-----Evaluate selected prospects, DISCOVERY
VI. District and Deposit Exploration-----Evaluate trends, configuration, type, size and grade.
Note that ore discovery is shown way down in Phase V. Obviously, this pleasant event could happen at any time; luck is a factor here, but the point is that the odds are infinitely bad if one depends heavily on luck in the search for obscured deposits. An analogy would be searching for a needle in the wrong haystack! While planning is essential, it is also just as essential that the program be kept flexible— old data must be frequently reexamined in the light of new ideas. Exploration consists of a few facts tied together by a generous amount of extrapolation. Early suppositions, therefore, are usually ephemeral, but necessary to provide a framework for further testing.
RESEARCH
An intelligent exploration effort must begin, and continue, with research into three basic subjects:
1). Working hypotheses or ore emplacement concepts which can be used to guide exploration
2). Areas and environments likely to contain the type of deposits being sought
3). Methodology and techniques of exploration that will most efficiently develop the data needed to evaluate the selected areas
Development of a working hypothesis involves the identification of criteria critical to the source, migration and deposition of uranium in a particular set of environments. Data come from a geologist's own experience, extensive literature research and examination of known deposits. A good concept is developed through trial and error, and is generally based on empirical evidence supported by a thorough understanding of the geologic history of the area and some theories of ore genesis. Most importantly, a working hypothesis is not static; it must continually evolve as new facts come to light; preconceived views must be disposable.
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Inasmuch as most of us have been involved in deposits hosted by sandstones, I will outline some of the primary criteria in this...
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