Brief overwiew
Gravimetry is the measurement of the strength of a gravitational field. Measurements of this field allow the estimation of rocks density and, consequently, the identification of geological structure. The density of rocks varies great and it is determined by their mineral composition, porosity, fracturing and fluid content.
Gravimetry is used for geological mapping, solid mineral prospecting, oil & gas prospecting etc. It is direct detection method for the prospecting of chromite and polymetallic ores.
Gravimetry has one of the biggest investigation depths amongst geophysical methods. Gravity anomalies have more smooth shape than magnetic ones over the same geological bodies, so it is easier to provide the geological interpretation of gravimetry data. Gravity surveys fulfilled in complex with other geophysical methods allow us to investigate the deep structure of the survey area. Even weak gravity anomalies, caused either by small deposits or ore-bearing tectonic dislocations, can be detected by gravimery if it has been done with necessary accuracy and survey scale (1:10 000 & more).
An instrument used to measure gravity is known as a gravimeter. Most of such instruments are based on principle of “spring balance” which are equipped by special tools in order to provide high precision of measurements. Besides of spring sensors, modern gravimetry systems include thermo-stabilized vacuum tank, advanced optical recording system, etc. The gravimeters are susceptible to extraneous vibrations including noise that tend to cause oscillatory accelerations.
Modern gravity surveys require detailed digital topography model of the area of interest with precise elevation determination ( ±1 – 5 cm).
The necessity of ground topography surveys makes the gravimetry expensive enough.
