Summary:
The Trapiche deposit is classified as a Cu-Mo porphyry deposit. A minor zone of skarning, is recognized to the north of the Trapiche deposit.
Skarn deposits can be genetically related to porphyry systems. Skarn mineralization can be developed at the margin of the mineralizing intrusion and in to receptive lithologies such as carbonaceous sediments of the Piste Formation.
Mineralization
The Trapiche deposit is spatially and temporally related to the Breccia Pipe. Minor skarning is recognized in the Millocucho skarn area.
Disseminated copper sulfides, molybdenite and copper oxides are hosted in quartz stockwork and sheeted veining in the QMP and Breccia Pipe. Highest grade mineralization is hosted in the MQB. Mineralization extends 2.1 km NNE-SSE, 1 km across and to approximately 500 m depth, beyond the confines of the Breccia Pipe. Three mineralized zones, from east to west, are defined as; Trapiche East Porphyry, Breccia Pipe and Copper Oxide Zone.
Supergene processes, aided by brecciation in the Trapiche East Porphyry and Breccia Pipe have driven the redistribution of copper mineralization, leaching copper sulfides close to surface and forming sub-horizontal blankets of high-grade secondary sulfides at greater depth. Development of copper oxides in the Breccia Pipe is negligible, copper oxides are best developed in the Copper Oxide Zone to the west of the breccia pipe at lower elevations and in sedimentary lithologies.
Four important fracturing and faulting systems are recognized at the Property:
• NW-SE Andean System is considered the most important due to its great tectonic activity and favorable structuring for the development of magmatic and hydrothermal activity, is represented by the Cerro Colorado and Arpa Orco faults system, both considered as sinistral lateral movement faults (according to the Riedel model);
• NE-SW system represented by the El Abra and Central faults, both have played an important role in the location of the breccia pipe and late intrusive dikes, correspond to fractures and faults with dextral lateral movement;
• EW system represented by the Trapiche and Camp fault system, corresponds to faults and tension fractures that have controlled the development of quartz veins and micro-veins (sheeting type veins) and sulfides; they have normal conjugated and sinistral movement;
• NS System, of good development in the southern part of the breccia and in the Millocucho zone, they seem to correspond to an ancient tectonic with post-mineral reactivation, they have controlled the location of late dikes (dacite-andesite) post minerals, large NS oriented tectonic faults such as the Zeguiña River fault accompany this system.
The Trapiche deposit is surrounded by the Yura Group of sediments, including the Piste and Chuquibambilla Formations:
• The Upper Jurassic, Piste Formation, grades upwards from carbonaceous mudstone with lesser interdigitated sandstone and limestone to calcareous siltstone with sandstone and minor mudstone;
• The Lower Cretaceous Chuquibambilla Formation is dominated by sandstone with minor intercalations of siltstone and mudstone.
Granodiorite
Granodiorite appears broadly south of the Trapiche porphyry and it has an elongated shape with the following dimensions: 2.5 km in length on the N-S axis by 1.5 km in width. It has a porphyritic texture composed of quartz, orthoclase, plagioclase, biotite and few amphiboles, on a feldspathic quartz matrix. It contains very little pyrite dissemination and traces of chalcopyrite, it is mostly fresh. It contains 1-2 cm isolated megacrystals of orthoclase. It is related to the prograde phase of the skarn bodies and is considered to be the precursor of the location of the quartz monzonite porphyry. Its age according to radiometric dating is 29.17 ± 0.67 Ma (Colombo Tassinari, 2012), which frames it in the lower Oligocene age.
Quartz Monzonite Porphyry (QMP)
The Quartz Monzonite Porphyry (QMP) was introduced via a zone of dilation at the northern margin of the granodiorite stock between Colorado and Trapiche South fault. Potassic, argillic, intermediate argillic and phyllic alteration is recorded in the QMP have been strongly altered and multiple events of copper and molybdenum are recognized. Granular, sinuous (Type A) and sheeted (Type B) quartz veinlets with disseminate chalcopyrite and bornite, and quartz-sulfide (chalcopyrite, pyrite) veins with alteration halos (Type C) are recorded in the QMP.
Breccia Pipe (Main Mineralizing Event)
A mineralized hydrothermal breccia pipe (Breccia Pipe) is hosted in the Intrusive Centre. The Breccia Pipe is elongate to the northeastsouthwest and measures approximately 900 x 500 m.