Magmatic differentiation a factor in the occurrence of ore shoots [Pachuca district, Hidalgo, Mexico]

Frederick J. Pope
1911 Economic Geology and The Bulletin of the Society of Economic Geologists  
The full name of the author should be attached to all communications. M.4GM.4TIC DIFFERENTIATION .4 F.4CTOR IN THE OCCURRENCE OF ORE-SHOOTS. While engaged in the examination of various mines, in the Pachuca (including Real del Monte) district, Hidalgo, Mexico, it appeared to the writer that the occurrence of the ore-shoots was closely associated with certain phases of the country rock and that these phases were the result of magmatic differentiation. It is the purpose of this paper to give in a
more » ... paper to give in a general way the data upon which this opinion is based. As the mines were examined while under professional engagement I do not, at the present time, feel at liberty to go into any detail concerning them. Briefly the geological sequence of the district may be outlined as follows: ß I. The most recent sedimentary rocks in the district belong to the Cretaceous period. 2. The Cretaceous rocks were penetrated by large intrusions closely related to andesites. These intrusions occur as large elliptical dome-shaped masses striking northwest-southeast. Their exposures are from ten to eighteen miles long, from eight to twelve miles wide and they probably have a much larger extent. The ore-bodies of the'Pachuca and of the Real del Monte districts occur within one of these dome-shaped masses. A consideration of the macroscopic and microscopic characteristics of 503
doi:10.2113/gsecongeo.6.5.503 fatcat:gjj336bc2rhrneboufzgciwbuy