You should review papers by Robert Moritz and Groves (1998) and decide for yourself, I think. There is a history of name usage for the reasons given and you are right, it is confusing in a way, but it looks like both names refer to similar deposits.

Dear Mr. Xaba

The term 'mesothermal' refers to a hydrothermal mineral deposit, formed at considerable depth and in the temperature range of 200-300 degrees Celsius (Park & MacDiarmid, 1970, p.317).

The term 'orogenic' includes thrusting, folding, and faulting in the higher levels of the earth crust, and ductile deformation, metamorphism and plutonism in the deeper layers (Glossary of Geology, 2.ed.).

Now you can decide whether these two terms or complexes are interchangeable itself.

Best regards,

G. Grundmann

Dear Mr. Xaba,

Dr. Grundmann is right. But unfortunately the classical terms "epithermal" and "mesothermal" ( supplemented with katathermal and telethermal on the way up and down in the temperatur range) have become a jargon decoupled from their constraining the temperature of formation of an ore deposit and often are used as a "booster" for the type of deposit under consideration.

Best regards

H.G.Dill

The simple answer is that they are commonly apllied to the same group of deposits but are not very satisfactory names although well entrenched. For example, as Lindgren originally used mesothermal and epithermal, some orogenic gold deposits are epithermal. And as Guenter says, they are classifications based on quite different variables, so there will always be things outside a common grouping of both. However I disagree slighty, as "orogenic gold" is not the same term as "orogenic" and is more specifically defined - see papers by Groves, Goldfarb etc. and is useful if you use these author's classification, and is genetic. Mesothermal is mostly P-T specific and yet some have made it largely genetic and fudged the P-T rigidity, so it is possibly better shelved (unless one specifies whose definition is being used), and has been much less used in the English-langiage literature since about 2000. One problem is that it can be a bit journal and nationality-specific (so if you didn't include both in a key word search, many references would be missed). And what is a deposit with a metamorphic overprint - often there will be other clues to genesis (but not many!) despite P-T being indeterminate (in some eyes - in others it is formed at the P-T that others would see as post-ore metamorphic - see papers by Phillips, Powell, Groves re Groves' Continuum Model.