TheMarañón fold and thrust belt (Spanish:faja corrida y plegada del Marañón) is a 1,000 kilometres (620 mi) long, northwest–southeast trending belt of deformed rocks located in theAndes of centralPeru.[1][2] The formation of the belt defines the Incaic Phase of theAndean orogeny.[note 1]
Prior to the deformation and uplift the rocks forming the Marañón fold and thrust belt constituted the fill of a marineback-arc basin that existed in theMesozoic and was parallel to the present-day coast.[4] Thewest-dippingChonta Fault existed as anormal fault within this basin and allowed continued basin subsidence and sediment accumulation in the Mesozoic.[5] The onset of Andean orogeny first caused the basin to rise and dry up withred beds being deposited in its eastern part. Then the sedimentary basin was subject of a completebasin inversion.[4] During deformation Chonta Fault acted as a barrier "damming-up"folded and thrust strata west of it. This makes the fault define the limits of two different styles ofthin-skinned deformation within the belt. The fault was reactivated as aninverse fault during basin inversion in theEocene.[5]
Theunconformity that cuts across the Marañón fold and thrust belt show the Incaic Phase of theAndean orogeny ended no later than 33 million years ago in the earliestOligocene. Above this unconformity the belt is overlain by volcanic rocks ofLate Eocene toMiocene age.[3] The parts of the belt areintruded byplutons of theCoastal Batholith of Peru.[3] There are various mineralizations ofbase metals andprecious metals in the belt, being particularly common alongChonta Fault. Most mineralizations are either ofepithermal,porphyry orskarn type. The most common ore metals in the mineralizations of the belt arezinc,copper,gold,lead,tungsten andsilver.[1]
