Mineral exploration process generally starts out very preliminary and can become extremely in depth depending on what the preliminary explorations returns. Large companies tend to abandon small deposits because it is not deemed financially worthwhile. Hands-off strategies such as applying theories that take into account known deposits in the area, common formation patterns of the elements being sought as well as geological mapping of the area. Together this combination of information provides a reasonably reliable probability of the size of potential deposits in a specific area. Exploration is divided into two parts which are; preliminary and extensive explorations.
PRELIMINARY EXPLORATION Thermal Methods
This involves the primary study of the area to be explored in the office. It generally involves the studying the maps of the area, literature review, reconnaissance, mining method to be introduced.
EXTENSIVE This deals with the various mining technique involved inEXPLORATION
This deals with the various mining technique involved in exploration. They are mostly geophysical methods. Details of geophysical techniques are not emphasized; these are covered in standard texts and have been summarized in Hoover and others. Various geophysical methods are identified below:
Gravity measurements define anomalous density within the Earth; in most cases, ground-based gravimeters are used to precisely measure variations in the gravity field at different points. Gravity anomalies are computed by subtracting a regional field from the measured field, which result in gravitational anomalies that correlate with source body density variations.
Positive gravity anomalies are associated with shallow high density bodies, whereas gravity lows are associated with shallow low density bodies. Thus, deposits of high-density chromite, hematite, and barite yield gravity highs, whereas deposits of low-density halite, weathered kimberlite, and diatomaceous earth yield gravity lows.
The gravity method also enables a prediction of the total anomalous mass (ore tonnage) responsible for an anomaly. Gravity and magnetic (discussed below) methods detect only lateral contrasts in density or magnetization, respectively. In contrast, electrical and seismic methods can detect vertical, as well as lateral, contrasts of resistivity and velocity or reflectivity.
Applications of gravity to mineral deposit environmental considerations include identification of lithologies, structures, and, at times, ore bodies themselves . Small anomalous bodies, such as underground workings, are not easily detected by gravity surveys unless they are at shallow depth.
The magnetic method of exploration exploits small variations in magnetic mineralogy (magnetic iron and iron-titanium oxide minerals, including magnetite, titanomagnetite, titanomaghemite, and titanohematite, and some iron sulfide minerals, including pyrrhotite and greigite) among rocks. Measurements are made using fluxgate, proton-precession etc. See image below
Seismic techniques have had relatively limited utilization, due to their relatively high cost and the difficulty of acquiring and interpreting seismic data in strongly faulted and altered igneous terrain, in mineral assessments and exploration at the deposit scale. However, shallow seismic surveys employ less expensive sources and smaller surveys than are typical of regional surveys, and the cost of studying certain geo-environmental problems in the near subsurface may not be prohibitive. Reflection seismic methods provide fine structural detail and refraction methods provide precise estimates of depth to lithologies of differing acoustic impedance. The refraction method has been used in mineral investigations to map low-velocity alluvial deposits such as those that may contain gold, tin, or sand and gravel. Applications in geo-environmental work include studying the structure, thickness, and hydrology of tailings and extent of acid mine drainage around mineral deposits.
Two distinct techniques are included under thermal methods (a) borehole or shallow probe methods for measuring thermal gradient, which is useful itself, and with knowledge of the thermal conductivity provides a measure of heat flow, and (b) airborne or satellite-based measurements, which can be used to determine the Earth's surface temperature and thermal inertia of surficial materials, of thermal infrared radiation emitted at the Earth's surface. Thermal noise includes topography, variations in thermal conductivity, and intrinsic endothermic and exothermic sources. Borehole thermal methods have been applied in geothermal exploration, but have seldom been used in mineral exploration. However, this method has potential usefulness in exploration and in geo-environmental investigations. Causes of heat flux anomalies include oxidizing sulfide minerals and high radioelement concentrations.