%0 Journal Article
%A Tornos Arroyo, Fernando
%A Galindo Francisco, María Del Carmen
%A Casquet Martín, César
%A Rodríguez Pevida, Luis
%A Martínez Chaparro, César
%A Martínez Colado, Enrique
%A Velasco Roldán, Francisco
%A Iriondo, Alexander
%T The Aguablanca Ni–(Cu) sulfide deposit, SW Spain:geologic and geochemical controls and the relationshipwith a midcrustal layered mafic complex
%D 2006
%@ 0026-4598
%U https://hdl.handle.net/20.500.14352/49443
%X The Aguablanca Ni–(Cu) sulfide deposit ishosted by a breccia pipe within a gabbro–diorite pluton.The deposit probably formed due to the disruption of apartially crystallized layered mafic complex at about 12–19 km depth and the subsequent emplacement of melts andbreccias at shallow levels (<2 km). The ore-hosting brecciasare interpreted as fragments of an ultramafic cumulate,which were transported to the near surface along with amolten sulfide melt. Phlogopite Ar–Ar ages are 341–332 Ma in the breccia pipe, and 338–334 Ma in the layeredmafic complex, and are similar to recently reported U–Pbages of the host Aguablanca Stock and other nearby calcalkalinemetaluminous intrusions (ca. 350–330 Ma). Oredeposition resulted from the combination of two criticalfactors, the emplacement of a layered mafic complex deepin the continental crust and the development of smalldilational structures along transcrustal strike-slip faults thattriggered the forceful intrusion of magmas to shallowlevels. The emplacement of basaltic magmas in the lowermiddle crust was accompanied by major interaction withthe host rocks, immiscibility of a sulfide melt, and theformation of a magma chamber with ultramafic cumulatesand sulfide melt at the bottom and a vertically zoned maficto intermediate magmas above. Dismembered bodies ofmafic/ultramafic rocks thought to be parts of the complexcrop out about 50 km southwest of the deposit in atectonically uplifted block (Cortegana Igneous Complex,Aracena Massif). Reactivation of Variscan structures thatmerged at the depth of the mafic complex led to sequentialextraction of melts, cumulates, and sulfide magma. Lithogeochemistryand Sr and Nd isotope data of the AguablancaStock reflect the mixing from two distinct reservoirs, i.e.,an evolved siliciclastic middle-upper continental crust and aprimitive tholeiitic melt. Crustal contamination in the deepmagma chamber was so intense that orthopyroxenereplaced olivine as the main mineral phase controlling the early fractional crystallization of the melt. Geochemicalevidence includes enrichment in SiO2 and incompatibleelements, and Sr and Nd isotope compositions (87Sr/86Sri0.708–0.710; 143Nd/144Ndi 0.512–0.513). However, rocksof the Cortegana Igneous Complex have low initial87Sr/86Sr and high initial 143Nd/144Nd values suggestingcontamination by lower crustal rocks. Comparison of thegeochemical and geological features of igneous rocks in theAguablanca deposit and the Cortegana Igneous Complexindicates that, although probably part of the same magmaticsystem, they are rather different and the rocks of theCortegana Igneous Complex were not the direct source ofthe Aguablanca deposit. Crust–magma interaction was acomplex process, and the generation of orebodies wascontrolled by local but highly variable factors. The modelfor the formation of the Aguablanca deposit presented inthis study implies that dense sulfide melts can effectivelytravel long distances through the continental crust and thatdilational zones within compressional belts can effectivelyfocus such melt transport into shallow environments.
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