The Jumilla lamproite revisited: a petrological oddity
Venturelli, Giampiero; Capedri, Silvio; Barbieri, Mario; Toscani, Lorenzo; Salvioli Mariani, Emma; Zerbi, Marco
European Journal of Mineralogy Volume 3 Number 1 (1991), p. 123 - 146
published: Feb 21, 1991
manuscript accepted: Sep 1, 1990
manuscript received: Apr 7, 1990
ArtNo. ESP147050301006, Price: 29.00 €
Abstract Among the Mediterranean lamproites, the Jumilla occurrence deserves particular interest since it contains significant amounts of carbonates and an apatite deposit. Jumillites (olivine-richterite madupitic lamproites) contain olivine (Mg# 89-93), phlogopite (Mg# 72-93), Fe-rich sanidine, spinels, K-rich richterite, clinopyroxene, fluorapatite and analcite (probably derived from leucite). Analcite can be locally very abundant (up to 40 % vol). The magmas were mostly peralkaline with high MgO (13-17 %), Cr (740-930 ppm), Ni (560-670 ppm), P205 (1.15-2.26 %), Ba, REE (Ce/Yb up to 160), Th (93-161) contents and high 87Sr/86Sr ratios (0.71378-0.71680). The rocks exhibit wide chemical variations which cannot be explained by fractional crystallization or by prograde partial melting of the same source. Carbonate-bearing assemblages are also present in the form of late crystallized aggregates in the groundmass (CARB-i) and as thin veins and infiltrates (CARB-ii) in the jumillite rocks. The carbonate assemblages and the jumillite magma are in some degree genetically related as suggested, for instance, by the Sr isotope data of the apatite.