Metallogenic features of Miocene porphyry Cu and porphyry-related mineral deposits in Ecuador revealed by Re-Os, 40Ar/39Ar, and U-Pb geochronology

Abstract

Mineralization and alteration events at ten Miocene porphyry Cu and porphyry-related epithermal mineral deposits in southern, central, and northern Ecuador were dated by means of molybdenite Re-Os, biotite and alunite 40 Ar/ 39 Ar, and titanite U-Pb geochronology. Most of these hydrothermal events show a spatio-temporal correlation with porphyry intrusion emplacement as constrained by zircon U-Pb ages. The total age range for these events spans the 23.5-6.1 Ma period, without displaying systematic along-or across-arc age distribution trends. While epithermal deposits tend to be spatially associated with volcanic rocks of a similar age, porphyry Cu deposits in Ecuador are frequently spatially associated with deeper-seated basement units and batholith-scale precursor intrusive systems assembled over ≥5 m.y. time periods. In most cases, formation of the porphyry Cu deposits is related to the -011-0378-z youngest magmatic (-hydrothermal) event in a given area, postdating batholith construction at a regional scale. The majority of Miocene deposits occurs in southern Ecuador where areally extensive, post-mineralization (late Miocene to recent) volcanic sequences with the potential to conceal mineralization at depth are lacking. Only few Miocene deposits occur in northern-central Ecuador, where they mainly crop out in the Western Cordillera, west of the productive present-day volcanic arc. The surface distribution of post-mineralization arc volcanism reflects along-arc variations in subducting slab geometry. Porphyry Cu and epithermal deposits in Ecuador define a Miocene metallogenic belt broadly continuous with its coeval counterpart in northern-central Peru. Although both belt segments were formed in an overall similar tectonomagmatic and metallogenic setting, their respective metal endowments differ significantly.Miner Deposita (2012) 47:383-410 DOI 10.1007/s00126

Magmatic sulphides in high-K calc-alkaline to shoshonitic and alkaline rocks

“…Available data on whole rocks indicate that mineralisation is spatially and temporally associated with high Sr/Y porphyritic stocks(Schütte et al, 2012). Investigation of these rocks under a reflected petrographic microscope confirmed previous observations fromSchütte et al (2012) that the rocks contain abundant hydrothermal sulphides, rendering these samples inadequate for the scope of the present study. For this reason,Georgatou et al (2018) have investigated fresh volcanic rocks from the Quaternary 365 arc of Ecuador.…”

Physiographic and tectonic settings of high-sulfidation epithermal gold–silver deposits of the Andes and their controls on mineralizing processes

“…Quimsacocha is located in the northern Andean block (sensu Gansser, 1973), about 20 km NW of the NE-trending Girón fault which constitutes an important terrane boundary separating the Upper Cretaceous Piñón terrane to the northwest, from the Lower Creteaceous Anaime terrane to the southeast (Ramos, 2009;Schuette et al, 2012). The Quimsacocha deposit adheres closely to the model for high-sulfidation epithermal deposits (MacDonald et al, 2011).…”

Quantitative and Qualitative Assessment of the “El Sexmo” Tourist Gold Mine (Zaruma, Ecuador) as A Geosite and Mining Site

“…The "El Sexmo" Tourist Mine is part of an intermediate sulphidation vein system of Au ± Ag ± Cu [31], have been related to propylitic, argillic, silica, and sericitic alterations type [42,[46][47][48], and that is regionally located in the extension of the southwestern segment of the Miocene metallogenic belt (mineral deposits from the Azuay-El Oro district) in Ecuador [49] (Figure 3a). This district contains tertiary granitoids [50], such as the Cangrejos-Zaruma intrusive complex [49]. The complex has an ESE tendency near the Piñas-Portovelo regional fault, and it is hosted in volcanic rocks of the Oligocene-Early Miocene Saraguro Group.…”

“…The process consisted of the collection of historical and cultural information (e.g., [15,30,32,[35][36][37]39,41,43,45]). In addition, the mining geological context of the mine and its setting was defined based on previous studies [31,42,46,[49][50][51][52][53][54][55] as a basis for subsequent assessment. The potential geotouristic interest presented by the study area was described.…”