The genesis of giants: lessons from the Tambogrande VMS district, Perú

CIM Vancouver 2006
Lawrence S. Winter, Richard M. Tosdal, James M. Franklin,
Abstract The Tambogrande VMS deposits in the Cretaceous Lancones basin of northwestern Perú constitute a distinctive district due to unusually large tonnages (>50 to 100 Mt) and include the TG1 (56 Mt @ 1.6% Cu, 1.0% Zn, 0.5 g/t Au & 26 g/t Ag), TG3 (82 Mt 1.0% Cu, 1.4% Zn, 0.8 g/t Au & 25 g/t Ag) and B5 (no resource data) deposits. The bi-modal mafic type Tambogrande deposits are akin to active deposits on the modern day seafloor (e.g., TAG mound, mid-Atlantic ridge) and have ancient analogues in Canadian Archean (e.g., Noranda camp). However, unique geological processes are required to generate multiple ‘giant’ deposits.
The Tambogrande deposits formed during a relatively short-lived arc volcanic event (104-92 Ma) during Gondwana break-up and a major plate motion readjustment. Additionally, the volcano-structural setting acted as a direct controlling factor in the geometry and size of the Tambogrande VMS deposits as (i) seafloor paleotopography caused a trapping effect for hydrothermal fluids; low volume but abundant bimodal lavas associated with the sulphide lenses indicate (ii) a replenishment of a composite subvolcanic magma chamber that supplied sustained heat and fueled a longer-lived hydrothermal system, and (ii) frequent volcanic eruption-related seismic activity likely re-initiated permeability in the substrata and helped sustain steady hydrothermal flow.
Keywords: Tambogrande, VMS, giant, Gondwana break-up, paleotopography
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