Structure

Geology

 - Property Geology - 

Structure

(last updated 09/08/2009)

The Haquira deposit is located within the Abancay Deflection, an east-west kink in the general NW trend of the Central Andes and the Andahuaylas-Yauri Belt (Figure 1).

Figure 1: Regional geological location of the Haquira deposit within the Abancay Deflection.

Jurassic-Cretaceous rocks of the Andahuaylas-Yauri Belt have undergone significant orogenic events, mostly N-S compression during various pulses of the Andean Orogeny (Incaic to Quechua). This orogeny produced tight folds, thrusts, and widespread overturning of strata. The Oligocene-Miocene intrusions responsible for the porphyry copper style mineralization at Haquira were emplaced into these already strongly deformed Jurassic-Cretaceous sedimentary rocks.

Early formed Andean orogeny related folds and thrust faults have been rotated into an east-west orientation within the Abancay Deflection andsubsequently overprinted by broad, open folds with axes oriented roughly north-south.

Within the Haquira property the Jurassic-Cretaceous sedimentary rocks are folded into series of major folds with wavelengths of 1-3 km. The folds are periclinal (i.e., doubly plunging) and the tightness varies tremendously along strike. The major folds are generally tight to isoclinal with hinges that vary from rounded to chevron (kink band) style. Many of these folds become thrust faults along strike. Parasitic folds are confined to ductile lithologies; they are widespread in the Chuquibambilla Formation. Relatively rigid sandstone beds within ductile mudstones were the focus for folding; these folds are tight, verge north, have wavelengths of ~100 m, and are generally overturned. Major folds and thrust faults identified include: a) Cintapata Anticline / Cintapata Thrust, and b) Tocone Syncline / Tocone Thrust. Figures 2 and 3 show the approximate locations of the various thrust faults and folds within the main Haquira West and East areas. Photos 1 and 2 show various field views of these structural features.

The suites of porphyry intrusions were intruded under broadly east-west extension with the dominant controlling faults being sub-vertical and striking roughly north-south. The porphyries occur in at least three north- to north-northwest-striking, sub-vertical corridors that have a monoclinal appearance, with downthrows to the west. 

Higher-grade copper mineralization appears to be controlled by the confluence of thrust faults, north-south structural corridors, reactive finer-grained sedimentary units, and proximity to mineralized porphyry intrusions.

Figure 2: Property-scale location of the various thrust faults and fold structures within the main Haquira West and East areas.

Figure 3: North-South cross-section showing the location and geometry of the thrust faults and fold structures within the Haquira East area.

Photo 2: Various thrust and fold structures as seen in the field at the Haquira deposit.