16th May 2018. La Gallega mine (Ojén) site visit Laval university (Quebec) and Aula museo de geologia Málaga.
Key words : Internal zones, peridotites, Upper mantle, Alboran domain, spinel lherzolites, La Gallega mine, thrust faults, Alpujata massif, Alpujata border, catazone metamorphic sequences, crustal units, Lithosphere-asthenosphere boundary, chromium-nickel ores, underground exploration, mining survey, rock mechanics assessment, geological discussion
A brief summary of the last site visit to La Gallega mine and their related Cr-Ni mineralization hosted in alpine spinel lherzolites. The student of economic geology coming from the Laval University in Quebec (Canada) had the chance to understand a bit more on site the features related to Ronda peridotites (Málaga), in south Spain within the Alboran domain. The geo-visit undertook questions related to their violent tectonic emplacement within a plate tectonic collision scenario, the spinel-garnet lherzolites border to crustal unit which comprises high grade T-P kinzigite, cordierite gneis, leucogranites and metapelites. The peridotite massif at Alpujata site also includes relevant chromiun-nickel magmatic ores mineralization which were the biggest one in Spain during early 1940 to 1960 of XX century, as strategic mineral resources to military purposes. The entire area, an exceptional example of litosphere-astenosphere preserved boundary.
The contact of Sierra Alpujata peridotite massif with those crustal units are underlied by the Ojen nappe (marble-amphibolite-cordierite-biotite gneis sequence) to the west (formed by the Rio Real valley), and subsequently overlied by Los Reales metamorphic cover to the southeast, within a “sandwiched” structure of high complexity.
The geological visit within the massif and la Gallega underground works, comprised a rock mass quality survey and assessment, structural recognition regarding to mineralized Cr-Ni veins (strike, dip direction and shear zones), and underground mining development, following by discussion and technical appraisal since a mining engineering point of view of such items.
The visit was ending with a claimed technical geo-visit to el Peñoncillo mine (Marbella-Ojén), located to the south west of the site, close to the border of the Alpujata peridotite massif, and closely related Mg-skarn type mineralization. Students realized the complexity of such Fe (magnetite-pyrrothite-pyrite) mineralization where the entire Ojén nappe (marbles, amphibolites and cordierite-biotite gneis related to regional metamorphism) is strongly folded in a exposed syncline -anticline structure, overthrusted by the Alpujata peridotites.
Since our geological mission and targets, the Aula Minerales y Tesoros de la Tierra project is keen and proud to undertake such tasks as a way of spreading our local knowledge and importance of our natural resources and mining heritage. Thank you very much to Laval university, professors and such well-headed and intelligent students to trust in us, making possible the brief international understanding of our main local natural resources