What type of mineralization are you referring to / interested in? The mineralization itself - e.g., Cu-Au, diamonds, etc - is very unlikely to be magnetic. The density contrast - I.e., the quantity responsible for any residual gravity response - depends not only on the mineralization but the surrounding host. Thus, any possible magnetic and gravity signatures are in large part related to indirect, associated circumstances. And these are extremely variable! Thus, the short answer to your question is "no, there is not any accepted range of gravity or magnetic anomaly associated with mineralization , nor is it necessary that there are any such anomalies at all".

... Richard

Just to expand what Richard Lane said:

The gravity anomaly depends on the difference between the density of the target and the density attributed to the reference effects removed from the data (normal Earth and Bouguer correction). The total field magnetic anomaly depends on the total magnetization (induced + remanent) of the target body.

Therefore, gravity and magnetic data do not "know" if the causative body is a mineralization. It merely shows that there is an anomalous density/magnetization. This anomaly can be due to a mineralization or something else entirely. Also, the density and magnetization of a geologic body depend on a variety of things and have very large, overlapping ranges.

What might distinguish between possible causes is other geophysical/geologic data. This is true for any geophysical method, e.g. seismology "sees" only impedance contrasts.

To reiterate, you cannot distinguish a mineralization (or anything) from the value of its gravity/magnetic anomaly alone.

The residual gavity and magnetic values can be used effectively when there is good control of the lithology and structure of a given area There is lot of such work done by the gravity and magnetic divisions of National Geophysical Research Institute, Hyderabad India which may be useful

there is no such value. The Bouguer gravity data is total of Regional and residual. the regional depends on surrounding host and can be assumed as a 2nd order polynomial or a cubic spline. The difference between Bouguer gravity and regional will give the residual data.

gravity values and magnetic values meaning nothing. they are relative measurements . give positive or negative anomalies, the positive anomalies are promising for mineral prospecting.