2015 Barcelona Student Chapter’s workshop: Ultramafic Ronda & Ojén Massifs: petrology, geochemistry and Cr-Ni-PGE associated mineralizations

Instead of undergoing a workshop consisting of several introductive lectures and a one day fieldtrip the Barcelona Student Chapter’s workshop of 2015 consisted of a two day field-workshop entitled“Ultramafic Ronda & Ojén Massifs: petrology, geochemistry and Cr-Ni-PGE associated mineralizations”.  The whole field-workshop was developed in the two small massifs of Ronda and Ojén (Málaga) during the 11th and 12th of September.

The peridotite massif of the Serranía de Ronda comprise three massifs (Ronda, Ojén and Carratraca) located in the westernmost internal zone of the Betico-Rifean Cordillera, which constitutes the westernmost segment of the Alpine belt in Europe. These massifs are made up primarily of lherzolite and harzburgite with minor dunite and pyroxenite layers. They represent portions of subcontinental lithospheric mantle tectonically emplaced at high temperature and high pressures into Paleozoic metasediments during the 20/22 Ma Alpine orogeny. Peridotites are zoned into three main lithological domains: a) spinel ± garnet tectonic domain, b) granular peridotite domain and c) plagioclase tectonic domain.

A small group of members including undergraduate, master and PhD students was led by Prof. Fernando Gervilla; full professor of the University of Granada and Joaquin Proenza (advisor) during the whole fieldtrip (Fig. 1.). These students had the opportunity to learn from an invited professor who has dedicated years of his research on the study of the Ronda peridotites; and furthermore, recently co-authored “Liquid immiscibility between arsenide and sulfide melts: evidence from a LA-ICP-MS study in magmatic deposits at Serranía de Ronda (Spain)”.

Fig.1. Groupal photograph taken in an outcrop characterised by chromitite and niqueline altered to annabergite mineralisation. Close to this outcrop spinelites mineralisation.

The first day was devoted to a cross-section study of the orogenic lherzolites of the subcontinental mantle which crop out in the Ronda massif. Firstly observed; the garnet peridotites where graphite pseudomorphs after diamond have been described (Crespo et al. 2006). Later on; the spinel peridotite and finally the peridotites with plagioclase.


Fig.2; Left image: Local acid diques of granitic composition. Right image: Gallega mine. Observation of chromite and niqueline mineralisations. Some of these veins also containing cordierite. 

 During the second day small chromite and Ni arsenide mines were visited: ex) Gallega Mine (Fig.2) where students had the opportunity to search for interesting hand-samples and acquire the experience of discerning between the diverse mineralogies present.