Earth Planets Space, Vol. 61 (No. 1), pp. 61-69, 2009
M. Calvo-Rathert1, A. Goguitchaichvili2, and N. Vegas-Tubía3
1Departamento de Física, EPS, Universidad de Burgos, c/ Francisco de Vitoria, s/n, 09006 Burgos, Spain
2Laboratorio Interinstitucional de Magnetismo Natural, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Campus Morelia, Michoacan, Mexico
3Departamento de Geodinámica, Universidad del País Vasco, 48080 Bilbao, Spain
(Received November 19, 2007; Revised April 17, 2008; Accepted May 5, 2008; Online published January 23, 2009)
Thirteen middle-Miocene to Pliocene volcanic sites, belonging to four different types of volcanism (calc-alkaline volcanism, potassic calc-alkaline and shoshonitic volcanism, lamproitic volcanism and basaltic alkaline volcanism), have been sampled in south-eastern Spain for paleointensity determinations. Rock-magnetic studies yield low-Ti titanomagnetite as the main carrier of remanence, showing also the presence of titanohematites in several cases. Analysis of hysteresis parameters indicates a PSD domain structure. Paleointensity determinations were performed with the Coe (1967) method. Of the 90 paleointensity determinations carried out, 29 provide successful determinations which fulfil selection criteria; most of these were in samples of lamproitic volcanism. Only four lamproitic sites out of the 13 studied ones yield reliable results. All have a similar age of approximately 7 M.y. Virtual dipole moments (VDM) of three of these display values between approximately 4·1022 A m2 and 8·1022 A m2, thus providing new paleointensity data for a time interval (between 4 and 8 M.a.), with a lack of Thellier-type paleointensity determinations. The fourth site shows a much lower paleointensity of 1.6·1022 A m2, and may correspond to a polarity transition, in accordance with its paleo-directional results.
Key words: Paleointensity, rock magnetism, Neogene, volcanic rocks, Betic region.