Neogene magmatism and its possible causal relationship with hydrocarbon generation in SW Colombia |
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| Authors: | Mónica Vásquez Uwe Altenberger Rolf L Romer |
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| Institution: | (1) Department of Geosciences, University of Potsdam, Karl-Liebknecht-Str. 24, Haus 27, D-14476 Potsdam-Golm, Germany;(2) Geoforschungszentrum Potsdam (GFZ), Telegrafenberg, Potsdam, 14473, Germany |
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| Abstract: | The Cretaceous oil-bearing source and reservoir sedimentary succession in the Putumayo Basin, SW Colombia, was intruded by
gabbroic dykes and sills. The petrological and geochemical character of the magmatic rocks shows calc-alkaline tendency, pointing
to a subduction-related magmatic event. K/Ar dating of amphibole indicates a Late Miocene to Pliocene age (6.1 ± 0.7 Ma) for
the igneous episode in the basin. Therefore, we assume the intrusions to be part of the Andean magmatism of the Northern Volcanic
Zone (NVZ). The age of the intrusions has significant tectonic and economic implications because it coincides with two regional
events: (1) the late Miocene/Pliocene Andean orogenic uplift of most of the sub-Andean regions in Peru, Ecuador and Colombia
and (2) a pulse of hydrocarbon generation and expulsion that has reached the gas window. High La/Yb, K/Nb and La/Nb ratios,
and the obtained Sr–Nd–Pb isotopic compositions suggest the involvement of subducted sediments and/or the assimilation of
oceanic crust of the subducting slab. We discuss the possibility that magma chamber(s) west of the basin, below the Cordillera,
did increase the heat flow in the basin causing generation and expulsion of hydrocarbons and CO2. |
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| Keywords: | Colombia K/Ar dating Magmatism Putumayo Basin Radiogenic isotopes Oil generation Oil expulsion |
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