Los sulfuros masivos volcanogénicos de la Cuenca Lancones (Perú)

Abstract

The Lancones basin is located on the north west coastal belt area of Peru, in the Department of Piura. It is bordered to the west by the Palaeozoic Amotapes coastal massif and to the east by the Western Andes pre-mountain range region. This basin extends to Ecuador, where it is called Celica basin. The Lancones basin contains arc-related felsic and mafic volcanic rocks, which make it an excellent target for exploration for volcanogenic massive sulphide (VMS) deposits in Peru. Actually the Lancones basin hosts the Tambogrande VMS group of deposits, which constitute the most advanced VMS project in Peru. This group consists of three world-class massive sulphide deposits TG1, TG3 and B5. The Lancones basin is part of a first-order extensive rift, in which tholeiitic oceanic-arc crust was generated. This extensional basin developed between the late Jurassic and the early Cretaceous period. The breakup of Laurasia and Gondwana, which began in the middle Jurassic, resulted in the north-west movement of what is presently the South American continent. The rift formed along a subduction zone on the western side of this continent. The stratigraphy of the submarine volcanic sequences is composed of a basal formation, the Basal Volcanic Group or GBV, which is disconformably overlain by a volcano-sedimentary formation, the Volcanic Sedimentary Group or GVS. These two formations contain two distinct metallogenic suites within the Lancones basin. Each is distinguished by specific lithogeochemical, petrographic and mineral attributes, age determinations and VMS deposit types. The pre-Albian mafic bimodal GBV contains high grade, large tonnage Cu-Zn type VMS deposits (Tambogrande type) associated to dacitic domes formed in second – or third-order extensional basins. The middle to upper Albian GVS contains low tonnage Zn-Pb-Cu type VMS mineralizations (Kuroko type). These are associated with felsic sequences of rhyolitic to dacitic composition, associated with a felsicdominated arc setting. The rocks of the GBV, which contain the polymetallic Tambogrande deposits, are tholeiitic. The rocks of GVS are mainly transitional between calc-alkaline and tholeiitic