The Erongo subvolcanic center in Namibia is the largest composite, bimodal complex in the Mesozoic Etendeka igneous province of Namibia. This study of 40Ar/39Ar and high spatial resolution U-Pb zircon dating demonstrates that emplacement of the various igneous units at Erongo took place within a time span equivalent to or shorter than geochronologically resolvable age differences (ca. 2 Ma), and at the peak of regional flood-basalt activity in the Etendeka-Paraná province. The Erongo complex comprises a series of felsic volcanic and intrusive units that overlie or intrude basaltic lavas attributed to the Etendeka Group. The stratigraphically oldest rhyodacite (Erongorus unit) yielded U-Pb zircon ages of 131.8±1.1 Ma (1σ). The overlying Ombu rhyodacite was previously dated at 135.0±1.6 Ma and our new ages for a resurgent intrusion of the same magma type (Ombu granodiorite) in the vent area are 132.6±1.1 Ma (40Ar/39Ar) and 132.3±1.9 Ma (U-Pb zircon) respectively. The youngest felsic magmas at Erongo are the high-silica Ekuta rhyolite and compositionally equivalent Erongo granite. These units yielded U-Pb zircon ages of 131.9±2.9 and 130.3±1.4 Ma, respectively. Concordant 40Ar/39Ar biotite ages from two samples of the granite average 132.2±0.8 Ma. The final stage of magmatism at Erongo involved emplacement of basic alkaline plugs and dikes. Phlogopite and kaersutite from foidite plugs of this series yielded 40Ar/39Ar ages of 130.8±1.0 and 132.0±1.0 Ma. In a regional context, these age results indicate that silicic magmatism in the largest complexes of the Damaraland (Erongo, Brandberg, Paresis, Messum) began simultaneously with the peak of flood-basalt effusion at about 132 Ma throughout the Etendeka province and ceased by about 130 Ma. The silicic magmas are hybrid, with varying contributions of crustal and mantle-derived melts, and the age constraints suggest that crustal melting was caused by a short-lived thermal pulse related to the main flood-basalt event. Basic magmatism in the Damaraland complexes continued sporadically thereafter to about 123 Ma, but lacked the power to create further crustal melting. © 2003 Elsevier B.V. All rights reserved.

Wigand, M., Schmitt, A., Trumbull, R., Villa, I., Emmermann, R. (2004). Short-lived magmatic activity in an anorogenic subvolcanic complex: 40Ar/39Ar and ion microprobe U-Pb zircon dating of the Erongo, Damaraland, Namibia. JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 130(3/4), 285-305 [10.1016/S0377-0273(03)00310-X].

Short-lived magmatic activity in an anorogenic subvolcanic complex: 40Ar/39Ar and ion microprobe U-Pb zircon dating of the Erongo, Damaraland, Namibia

VILLA, IGOR MARIA;
2004

Abstract

The Erongo subvolcanic center in Namibia is the largest composite, bimodal complex in the Mesozoic Etendeka igneous province of Namibia. This study of 40Ar/39Ar and high spatial resolution U-Pb zircon dating demonstrates that emplacement of the various igneous units at Erongo took place within a time span equivalent to or shorter than geochronologically resolvable age differences (ca. 2 Ma), and at the peak of regional flood-basalt activity in the Etendeka-Paraná province. The Erongo complex comprises a series of felsic volcanic and intrusive units that overlie or intrude basaltic lavas attributed to the Etendeka Group. The stratigraphically oldest rhyodacite (Erongorus unit) yielded U-Pb zircon ages of 131.8±1.1 Ma (1σ). The overlying Ombu rhyodacite was previously dated at 135.0±1.6 Ma and our new ages for a resurgent intrusion of the same magma type (Ombu granodiorite) in the vent area are 132.6±1.1 Ma (40Ar/39Ar) and 132.3±1.9 Ma (U-Pb zircon) respectively. The youngest felsic magmas at Erongo are the high-silica Ekuta rhyolite and compositionally equivalent Erongo granite. These units yielded U-Pb zircon ages of 131.9±2.9 and 130.3±1.4 Ma, respectively. Concordant 40Ar/39Ar biotite ages from two samples of the granite average 132.2±0.8 Ma. The final stage of magmatism at Erongo involved emplacement of basic alkaline plugs and dikes. Phlogopite and kaersutite from foidite plugs of this series yielded 40Ar/39Ar ages of 130.8±1.0 and 132.0±1.0 Ma. In a regional context, these age results indicate that silicic magmatism in the largest complexes of the Damaraland (Erongo, Brandberg, Paresis, Messum) began simultaneously with the peak of flood-basalt effusion at about 132 Ma throughout the Etendeka province and ceased by about 130 Ma. The silicic magmas are hybrid, with varying contributions of crustal and mantle-derived melts, and the age constraints suggest that crustal melting was caused by a short-lived thermal pulse related to the main flood-basalt event. Basic magmatism in the Damaraland complexes continued sporadically thereafter to about 123 Ma, but lacked the power to create further crustal melting. © 2003 Elsevier B.V. All rights reserved.
Articolo in rivista - Articolo scientifico
geochronology, Namibia
English
2004
130
3/4
285
305
none
Wigand, M., Schmitt, A., Trumbull, R., Villa, I., Emmermann, R. (2004). Short-lived magmatic activity in an anorogenic subvolcanic complex: 40Ar/39Ar and ion microprobe U-Pb zircon dating of the Erongo, Damaraland, Namibia. JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 130(3/4), 285-305 [10.1016/S0377-0273(03)00310-X].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/4148
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