A5.- Construction of the Andean Mesozoic plutonic arc
(Chañaral-Copiapó-Vallenar traverses)


App. cost:
November 9-13 2004 (5 days)
C. Arévalo (SERNAGEOMIN-Chile)
J. Grocott (Kingston University-UK)
D. Welkner (SERNAGEOMIN-Chile)
App. cost: US $ 650

Subject: Construction of the Mesozoic plutonic arc: pluton geometry, emplacement mechanisms and relationship with the overiding plate tectonics
Main goals:
Whereas the study of the volcanic products of the Cenozoic and modern Andean chain allows indirect inferences on lithospheric processes, the eroded roots of the Mesozoic arcs offer a unique opportunity to examine, in the field, the processes of arc building, emplacement of magmas and their interaction with deformation in the arc and the associated processes of mineralisation. In this field trip we will make three traverses across the Coastal Cordillera of the Atacama region (Chañaral-Copiapó, Quebrada Carrizal and Quebrada Agua Grande). On the face of new concepts on magma transport and emplacement we will examine field evidence of 3D geometry of plutons, emplacement mechanisms and the respective relationships with the overall tectonics regime of the overiding plate.

Preliminary Programme:
Day 1 (Nov. 9):
Flight Santiago-Copiapó. Transport from Copiapó to Vallenar (by coach). Overnight at Vallenar.
Day 2 (Nov. 10):
Vallenar (departure). (1) Road to Canto del Agua (general overview). (2) Carrizal Bajo (plutonic architecture, feeder dykes and mingling breccias). (3) Quebrada La Higuera (feeder dykes, lowermost plutonic layer). (4) Quebrada del Carrizo (metamorphics-pluton interfase, migmatites). Overnight at Vallenar.
Day 3 (Nov. 11):
Vallenar (departure). (1) Portezuelo Sosita (general overview). (2) Quebrada Agua Grande (plutonic architecture, lower plutonic layer, marginal mylonites). (3) Quebrada Aguilar (upper plutonic layer). (4) Sierra La Bandera (Los Colorados fold-thrust belt). (5) Los Colorados Fe mine. Overnight at Vallenar.
Day 4 (Nov. 12):
Vallenar (departure).(1) Quebrada Jilguero (general overview). (2) Quebrada El Carbón (emplacement v/s post emplacement contractional structures). (3) Camino Los Morteros (plutonic layering). Overnight at Copiapó.
Day 5 (Nov. 13):
Return flight Copiapó-Santiago.

Note: Participants to this field trip are recommended to take their own health and travel insurance. The organising committee will not be responsible of any possible accident occurred during the trip.