Paleocene Adakite Bearing Au-Fe Intrusive Rocks, Mezcala, Mexico: Evidence from Geochemical Characteristics - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Geochemical Exploration Année : 2003

Paleocene Adakite Bearing Au-Fe Intrusive Rocks, Mezcala, Mexico: Evidence from Geochemical Characteristics

Résumé

The Au–Fe mineralized granitoids at Mezcala district have a porphyry texture with a quartz+feldspar microcrystalline matrix and phenocrysts of plagioclase, quartz (with reaction rims), hornblende and biotite. The primary minerals are oligoclase–andesine, microcline and β-quartz. The accessory minerals are biotite, hornblende and, in minor amounts, apatite+zircon+sphene+titanomagnetite. Some intrusive rocks present abundant hornblende autoliths. Based on the petrography and bulk geochemistry of these granitoids, they are classified as monzonite, tonalite (the most abundant) and granodiorite with a strong calc-alkaline trend in potassium (K2O=3.8% average). The bulk and trace elements chemistry is SiO2=63.8%, Al2O3=15.83%, Fe2O3+MgO+MnO+TiO=6.52%; V=76.7 ppm, Cr=50.2 ppm, Ni=19.7 ppm, Sr=694 ppm. These granitoids show a strong depletion in heavy rare-earth elements (HREE), with average values of Yb=1 ppm and Y=13 ppm, this being the characteristic geochemical signature for adakite. The trace elements content suggests that the adakite granitoids from Mezcala were formed within a tectonic framework of volcanic arc related to the interaction between the Farallon and North America plates. This interaction occurred during the Paleocene after the Laramide Orogeny (post-collision zone) in a fast convergent thick continental crust (>50 km) subduction regime. The original magma is interpreted as being the product of partial melting of an amphibolite–eclogite transition zone source with little contribution of the mantle wedge. Along with the hydration processes, a metallic fertility also took place in the area. The geochemical signature of the adakites within the granitoids rocks represents a characteristic guide for further exploration for Au-rich skarn-type ore deposits in southern México.

Dates et versions

hal-00117326 , version 1 (01-12-2006)

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Citer

E. Gonzalez-Partida, G. Levresse, A. Carrillo-Chávez, A. Cheilletz, Dominique Gasquet, et al.. Paleocene Adakite Bearing Au-Fe Intrusive Rocks, Mezcala, Mexico: Evidence from Geochemical Characteristics. Journal of Geochemical Exploration, 2003, 80, pp.25-40. ⟨10.1016/S0375-6742(03)00180-8⟩. ⟨hal-00117326⟩
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