No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Andean copper province: Tectonomagmatic settings, deposit types, metallogeny, exploration, and discovery
... This rapid rise of the rock column possibly triggers magma decompression causing fluid generation and release (Richards 2013), and/or opening of fluid pathways along faults and lineaments (Skewes and Stern 1994;Richards 2003Richards , 2013Sillitoe 2010) and/or facilitates telescoping, whereby early porphyry-style mineralization at depth is overprinted and enriched by high-sulfidation mineralization at shallower crustal levels as exhumation continues (Masterman et al. 2005;Sillitoe et al. 2019). Examples of such telescoped alteration-mineralization are seen in the Southwest USA, Central Andes, New Guinea and the Philippines Masterman et al. 2005;Rohrlach and Loucks 2005;Sillitoe and Perelló 2005). Rapid cooling and reactive host rocks promote metal precipitation, creating focused, high grade ore shells, rather than diffuse, spread-out ore zones (Sillitoe 2010;Richards 2013). ...
... The region hosts many well-developed metallogenic belts (Fig. 5) (Sillitoe 2010), which have been linked with periods of anomalously high compression and host PCD (Loucks 2021). The most well-endowed belt in the Central Andes is the middle Eocene to early Oligocene belt (Sillitoe and Perelló 2005). ...
... The cessation of supergene enrichment as MAR fell below 120 mm is also diachronous across the region, terminating at 21 Ma in the Coastal Cordillera, 10 Ma along the western margin of the As these climatic conditions migrated diachronously across the Andes, the region of supergene enrichment also migrated (Evenstar et al. 2023), with enrichment starting in the late Eocene along the western margin of the Andes and substantially later in the Miocene in the Altiplano and Eastern Cordillera (Fig. 6D). These conditions favored enrichment of newly formed PCD, but also of older deposits such as Late Eocene deposits at Ccalla, Peru, enriched Sillitoe and Perelló (2005). (G) Conditions integrated into the ideal environment for the formation, supergene enrichment, and preservation of PCDs in the Central Andes the timing of supergene activity dated by alunite, jarosite or cryptomelane using 40 Ar/ 39 Ar and K-Ar or U-Pb of copper minerals (Fig. 7B). ...
Currently, 60% of the world’s copper production comes from porphyry copper deposits, often significantly enriched by surface weathering. This paper uses new global datasets and previous work to review the critical processes required for porphyry copper formation and supergene enrichment. Porphyry copper formation requires a subducting arc to create a source magma which traverses a thickened crust subject to high exhumation rates during formation, ranging from 100’s to 1,000’s m/m.y. High exhumation rates potentially trigger magma decompression, causing fluid release, opening fluid pathways along faults and lineaments and/or facilitating telescoping, whereby early porphyry-style mineralization is overprinted and enriched by high-sulfidation mineralization at shallower crustal levels. Later supergene enrichment of the deposit requires precipitation rates > 120 mm/yr and exhumation rates ranging from 10’s to 100’s m/m.y. This allows copper sulfide sources to be continually refreshed for weathering but restricts the amount of erosion. Using the Central Andes, one of the world’s most critical porphyry copper provinces, the understanding gained from analyzing these global databases can explain the temporal and spatial pattern of known deposits. These constraints were used to inform mappable target criteria and data required for mineral exploration at a range of different scales, from orogen (> 100,000 km²), to terrane (100,000–1,000 km²) to arc (1,000–100 km²). The results can be used to help illustrate and inform global exploration strategies for supergene-enriched porphyry copper deposits.
... In northern and central Chile and contiguous northwestern Argentina, these deposits define a series of orogen-parallel metallogenic belts and corresponding epochs that are hosted by spatially and temporally coincident, subduction-related, magmatic arcs. The belts become progressively younger eastward from Early Cretaceous (143-104 Ma) through Late Cretaceous (98-87 Ma), Paleocene to early Eocene (63-52 Ma), and middle Eocene to early Oligocene , to Miocene through early Pliocene (19-4 Ma) (Sillitoe, 1988;Sillitoe and Perelló, 2005; Fig. 1). However, this eastward progression is complicated by several isolated porphyry Cu centers in the Eocene-Oligocene back arc (Fig. 1). ...
... The eastward migration of the magmatic arcs and contained porphyry Cu mineralization may be attributed at least in part to episodic subduction erosion at the leading edge of the overriding South American plate (Rutland, 1971;Stern, 2020). The exception to this systematic array is a composite belt of late Paleozoic to Triassic (~318-213 Ma) porphyry Cu occurrences, which is obliquely overlapped by the three Cenozoic belts (Sillitoe, 1988;Sillitoe and Perelló, 2005; Fig. 1). This composite pre-Andean belt occupies part of an areally extensive Late Carboniferous-Triassic magmatic province, including the Choiyoi Group (Kay et al., 1989;Sato et al., 2015), whose volcanic and intrusive rocks acted as hosts for many of the Cenozoic porphyry Cu deposits and prospects in northern Chile and northwestern Argentina. ...
... The various metallogenic belts and corresponding epochs have very different Cu endowments, with the middle Eocene-early Oligocene belt in northern Chile and southwesternmost part of the Mioceneearly Pliocene belt in central Chile and contiguous Argentina being preeminent and containing >80% of the region's Cu resources. In stark contrast, the late Paleozoic to Triassic porphyry Cu mineralization is everywhere subeconomic (Sillitoe and Perelló, 2005). ...
Porphyry Cu deposits in the Chilean and Argentinian central Andes occur in a series of orogen-parallel magmatic arcs, which migrated episodically eastward since the Early Cretaceous. The three Cenozoic belts, corresponding to Paleocene-early Eocene, middle Eocene-early Oligocene, and Miocene-early Pliocene epochs, cut obliquely across a composite belt of subeconomic porphyry Cu mineralization formed at several times during the Late Carboniferous to Triassic interval. Based mainly on U-Pb zircon and Re-Os molybdenite ages, 10 Cenozoic porphyry Cu centers, including major deposits in all three of the Cenozoic belts, occupy the same sites as late Paleozoic-Triassic porphyry Cu mineralization where their respective magmatic arcs cross one another. The sites of recurrent porphyry Cu mineralization are believed to be underlain by long-lived dike conduits that were utilized at least twice—first in the late Paleozoic-Triassic and then again in the Cenozoic—to rapidly transmit hydrous magma from deep to shallow levels of the crust. Contenders for preferential dike localization include arc-oblique fault and subjacent ductile shear zones—transcrustal discontinuities—long hypothesized to be present in the region, particularly where they intersect magmatic arcs and associated porphyry Cu belts. Regardless of the controls on porphyry Cu recurrence, alteration zones hosted by late Paleozoic-Triassic volcanic and plutonic rocks in the central Andes of Chile and Argentina must be considered prime exploration targets for potentially large, high-grade Cenozoic porphyry Cu deposits.
... Indeed, one of the main shortcomings of predictive power seems to lie in the lack of understanding the causative relationships between spatial, temporal, and genetic processes within broader geodynamic contexts. Whereas the importance of first-order, arc-or greenstone belt -parallel faults as primary, trans-lithospheric pathways for metalbearing magmas and ore-fluids is commonly accepted (e.g., Neumayr et al., 1998;Haeberlin et al., 2002;Sillitoe and Perello, 2005;Bierlein et al., 2006;Goldfarb et al., 2008;Groves et al., 2018), the along-strike spatial distribution of deposits commonly remains poorly studied or controversial (e.g., Angerer et al., 2018). Various studies attest to the presence of major deposit clusters located at sites of structural complexity along, and/or in vicinity to, their first-order fault system (e.g., Eisenlohr et al., 1989;Neumayr et al., 1998;Thébaud et al., 2018;Piquer et al., 2021a;Wiemer et al., 2021a;. ...
... This review paper summarizes the general endmember models for the spatial distribution of ore deposits, while keeping in mind the possibility of syn-mineralization structure development, followed by a critical review on the tectonic and metallogenic evolution of South America, focussing on gold-rich porphyry, intrusion related and orogenic mineral systems along the western Gondwana margin and subsequent Andean belt. The distribution of ore deposits and deposit clusters along the western South American margin was used previously to demonstrate both endmember modes of spatialgenetic control, as the region represents a suitable natural laboratory to test respective hypotheses, due to the presence of extensive and well-preserved ore-rich arc segments (i.e., metallogenic belts) on the one hand (e.g., Sillitoe, 1976;Sillitoe and Perello, 2005;Carlotto et al., 2009;Hayward et al., 2018), and the notion of cryptic ancient lineaments and inherited Andean cross-faults, on the other hand (e.g., Chernicoff et al., 2002;Richards, 2003;Love et al., 2004;Ramos, 2008;McCuaig and Hronsky, 2014;Wiemer et al., 2022). ...
... Across the transverse boundaries, there are subtle changes in the distribution, lateral width, metal endowment, and overall presence or absence of metallogenic belts of a specific mineralization episode. Furthermore, it was noted that deposits cluster in vicinity to these transverse boundary structures (Sillitoe, 1976;Sillitoe and Perello, 2005). Meanwhile, other studies focussing on Cu and Cu-Au porphyry and related epithermal deposits in northern Chile found that major deposits are located at intersections between principal arc-parallel structures and other, cryptic major lineaments of supposedly more ancient origin (e.g., Salfity, 1985;Chernicoff et al., 2002;Richards, 2003;Gow and Walshe, 2005). ...
We present a review of frontier research advances in the investigation of cryptic structures that transect the South American Andes at oblique strike directions. The intersections between these cryptic structures and the superimposed Andean belt correlate with the spatial distribution of gold-rich mineral deposit clusters. The deposit clusters can be described as superclusters, as they comprise various gold deposit types that formed at multiple times throughout the Phanerozoic, impinging repeatedly on the structural intersections. However, the cryptic inherited fault structures are difficult to detect, because their deeper-seated roots are often overlain by younger supracrustal successions, and/or their exposed surface manifestations are structurally obscured by subsequent tectonic-magmatic activity. Thus, it also remains a challenge to constrain the nature and timing of formation, and the respective subsequent evolutionary path, of these proposed pre-Andean structures. Based on various case studies, we demonstrate that the localization of identified Phanerozoic gold deposit superclusters along the western South American margin is fundamentally controlled by structural inheritance often dating back to at least the Mesoproterozoic. Integration of multi-approach observations and datasets allows insights into a larger-scale tectonic history that showcases the successive inheritance of major structures originating from the Amazonian Craton, over the Paleozoic Gondwana margin, into the Cenozoic magmatic belts of the Andes, and even into recent fractures within the subducting oceanic Nazca plate, recording >1.2-billion-years of progressive structural inheritance and growth at one of the longest-lived tectonic margins in Earth history. In contrast to previous models of the spatial distribution of gold deposits, based on statistical approaches and spatial periodicity in self-organized systems focusing on single subduction and/or accretion episodes and belts, we propose that the structural inheritance and intersections are key to the localization of gold deposits in the Andes. In combination with bulk-geochemical data from magmatic rocks, we suggest that inherited structures maintained a trans-lithospheric connectivity to pre-fertilized gold enriched upper mantle reservoirs, which were tapped during multiple tectono-magmatic reactivation episodes.
... The central Andes, between 14°S and 35°S latitude, is the most important copper province on the planet, accounting for approximately 40% of the world's annual copper mine production (U.S. Geological Survey [USGS], 2021). The decades leading up to the year 2000 saw numerous greenfields porphyry copper discoveries in the central Andes (Sillitoe and Perelló, 2005); however, since 2000, few significant new greenfields porphyry discoveries have been reported (e.g., Sillitoe, 2010a;Rode et al., 2015;Schodde, 2019;Sillitoe et al., 2019). Declining discovery rates in the central Andes are likely a function of increasing exploration maturity and extensive postmineralization cover, issues that affect many other mineral belts worldwide (McCuaig and Hronsky, 2014). ...
... Giant porphyry copper deposits (>3.1 Mt of contained copper; Clark, 1993) in the central Andes align within linear, orogen-parallel belts that spatially and temporally coincide with the magmatic arc ( Fig. 1; Cooke et al., 2005;Sillitoe and Perelló, 2005;Sillitoe, 2010b) and have been noted to exhibit marked along-arc spatial periodicity that is not explained by upper crustal or stochastic processes alone (Yáñez and Maksaev, 1994;Richards, 2003;Tomlinson and Cornejo, 2012;Hayward et al., 2018). At the district scale, giant deposits tend to occur as discrete, multideposit clusters of similar age (Fig. 1B-D;Sillitoe, 2010b;Hayward et al., 2018). ...
... The locations of interpreted suture zones between basement terranes are shown as dashed lines (see text for discussion). Giant porphyry copper deposits are colored by metallogenic age (after Sillitoe and Perelló, 2005). B) Middle Miocene-Pliocene metallogenic belt of central Chile; five deposit clusters as defined by Hayward et al. (2018) are separated by 90 ± 15 km. ...
In the central Andes, giant porphyry copper deposits of similar ages group into discrete geographic clusters that are regularly spaced and aligned within orogen-parallel belts. This clustering highlights how exceptional geologic processes affected localized regions of the lithosphere during mineralization and that the spatial and temporal distribution of giant porphyry deposits is non-random. Development of favorable regions of lithosphere for significant metal concentration are linked to the overlap of structural pathways that focus fluid and magma flow from the mantle to upper crust during high horizontal compressive strain events. These structural pathways are notoriously difficult to identify in the field due to their often-subtle surficial manifestations and continental scale. Field mapping at multiple scales in northwest Argentina and southern Peru, as well as regional structural traverses throughout the central Andes, indicate the presence of regional-scale structural corridors 5 – 25 km wide and hundreds of kilometers long that consist of myriad fault planes. The variable width and diffuse surface expression of these corridors is interpreted to reflect the upward propagation of underlying zones of basement weakness through younger supracrustal sequences in the over-riding plate. Such structural corridors are: (i) apparent at multiple scales of investigation; (ii) long-lived; (iii) preferentially reactivated though time; and (iv) evident in geophysical datasets. This structural architecture formed in response to the interplay of pre-Cenozoic tectonics and the orientation of inherited structural weaknesses. These fault systems persist in the upper crust as steep zones of enhanced permeability that can preferentially reactivate as pathways for ascending hydrous magmas and fluids during major deformation events. Linear orogen-parallel structural belts cogenetic with the magmatic arc, provide the first order control to giant porphyry copper deposit distribution. The second order control is the intersection of orogen-oblique structural corridors with the orogen parallel belts, localizing deposit clusters at these intersections. Such regions are inferred to have been zones of deep permeability, with vertical translithospheric pathways activated during high strain tectonic events that affected the intra-arc stress field.
... data, 2016), broadly simultaneous with the Veladero (~12-10 Ma) and before formation of the Pascua-Lama (9-8 Ma) high-sulfidation epithermal Au deposits (Bissig et al., 2001;Charchaflié et al., 2007;Holley et al., 2016). Together, these deposits demonstrate metallogenic continuity between the Vicuña, Maricunga, and El Indio belts, a concept anticipated two decades earlier (Mpodozis and Kay, 2003;Sillitoe and Perelló, 2005; Fig. 1a). ...
... An epithermal overprint was rapidly established in what was previously a deeper-level potassic alteration zone, and several pulses of high-sulfidation mineralization as well as intervening phreatic (and likely phreatomagmatic) breccia bodies were emplaced (Fig. 13). This situation is reminiscent of the giant porphyry Cu deposits of the middle Eocene to early Oligocene belt of northern Chile, some of which display telescoping of structurally localized high-sulfidation mineral assemblages over deeper alteration types (Sillitoe and Perelló, 2005). ...
... Similarly, the lack of coeval volcanism of 14 to 12-Ma age along the Vicuña belt is consistent with the contractional tectonism during porphyry Cu-Au formation along the Filo del Sol alignment. Indeed, suppression of volcanism during compression accompanied by high rates of surface uplift and rapid exhumation are considered to provide the optimal con-ditions for accumulation of fluid-rich magma in large, shallowlevel reservoirs propitious for giant porphyry Cu development (e.g., Sillitoe, 1998), as exemplified by the most productive porphyry Cu belts of the central Andes (Sillitoe and Perelló, 2005). ...
Filo del Sol is a composite porphyry-epithermal deposit, straddling the frontier between Argentina and Chile at latitude 28°29′ S, that has attracted a great deal of recent attention because of several drill intersections in excess of 1 km long with unusually high Cu, Au, and Ag grades. The deposit is part of the 8.5-km-long, N- to NE-trending Filo del Sol alignment of porphyry and high-sulfidation epithermal centers, which, in turn, is located in the newly defined Vicuña metallogenic belt that unites the well-known late Oligocene to middle Miocene Maricunga and El Indio belts. The deposit is hosted by Permian felsic volcanic rocks intruded by Triassic monzogranite and, nearer the surface, by shallowly dipping Late Cretaceous volcano-sedimentary rocks. These lithologic units were intruded by several generations of mafic dikes and high-level sills and, in the middle Miocene, by a parallel swarm of composite diorite porphyry dikes. An intermineral magmatic-hydrothermal breccia body is closely associated with the porphyry dikes and subsequently cut at shallow levels by a smaller, finer-grained breccia of phreatic and, possibly, phreatomagmatic origin. Early Cu-Au mineralization, mainly as chalcopyrite, is associated with K-feldspar- and biotite-bearing potassic alteration and accompanying A-type quartz-veinlet stockworks. The potassic zone was massively overprinted and extensively reconstituted by a zone of vuggy residual quartz and silicification in the core of the deposit, flanked by quartz-alunite as part of a more extensive lithocap. These alteration types host high-sulfidation Cu-Au-Ag mineralization as pyrite with early enargite and later bornite, chalcocite, covellite, and numerous Ag-bearing sulfosalts, with the highest grades typically confined to vuggy residual quartz. Largely barren, steam-heated alteration is preserved above and overprinted on the lithocap. The results of radiometric dating (six U-Pb and 22 Re-Os ages) show that porphyry intrusion and potassic alteration began at ~15 Ma and lasted for nearly 1 m.y., although most of the molybdenite samples reported ages from 14.7 to 14.4 ± 0.06 Ma. This short interval coincided with a pulse of regional compressive tectonism accommodated by high-angle, thick-skinned, reverse faulting of basement-cored blocks, and concomitant uplift and exhumation. This uplift gave rise to ~1 km of erosion during formation of the Filo del Sol deposit, thereby accounting for the extreme telescoping of high-sulfidation over porphyry mineralization. Spatial association of these middle Miocene intrusion centers with dated middle Permian and Eocene mineralization suggests deep-seated structural control of the Filo del Sol alignment. Ongoing supergene processes under low-pH conditions produced a near-surface resource dominated by chalcanthite, with minor underlying chalcocite enrichment, as well as partially oxidizing a shallow zone of high-grade Ag mineralization.
... The east-dipping subduction of the Farallon and Nazca plates beneath the South American continent from the Mid to Late Jurassic onward has led to orogenesis, arc magmatism and porphyry copper formation in the Andes 21 . Porphyry copper deposits are aligned in arc-parallel belts along the western South American Andean margin, with each belt corresponding to a distinct metallogenic epoch 22 . In northern Chile, porphyry mineralization is associated with two main pulses of magmatic activity from the Paleocene to Early Eocene and from the Late Eocene to Early Oligocene 3,22 . ...
... Porphyry copper deposits are aligned in arc-parallel belts along the western South American Andean margin, with each belt corresponding to a distinct metallogenic epoch 22 . In northern Chile, porphyry mineralization is associated with two main pulses of magmatic activity from the Paleocene to Early Eocene and from the Late Eocene to Early Oligocene 3,22 . Even though the Paleocene-Eocene copper belt is economically less relevant than the younger, eastern, Eocene-Oligocene copper belt associated with the N-S trending Domeyko fault system ( Fig. 1), it hosts a number of large deposits in northern Chile, such as Spence and Cerro Colorado (Fig. 1), and becomes the dominant copper province in southern Peru 23 . ...
... This orogen-parallel, 40-60 km wide zone of deformation stretches for more than a 1000 km along the Precordillera of northern Chile, and consists of an array of strike-slip, normal, and reverse faults, associated with folds and thrusts 21,33 . While the exact origin and deformation history of the Domeyko fault system are debated, a major tectonic pulse took place in the Middle Eocene to Early Oligocene, coinciding with the Incaic tectonic event, and the formation and emplacement of Eocene-Oligocene porphyry copper deposits in northern Chile 21,22 . In our study area, two main branches of the Domeyko Fault System striking roughly northward enclose the ~ 38 Ma Queen Elizabeth prospect 34 exposed along the Quebrada Minacucho about 30 km to the northeast of Cerro Colorado. ...
An essential part of the world's remaining mineral resources is expected to reside deep in the crust or under post-mineralization cover. For porphyry copper deposits, the world’s primary source of Cu, Mo, and Re, identifying the dynamic processes that control their emplacement in the upper crust can guide future exploration. Seismic tomography can constrain these processes through imaging deep-seated structures at the regional scale. Here we construct a three-dimensional model of the Vp/Vs ratio, based on arrival times of P and S seismic waves, beneath the Cerro Colorado porphyry Cu–(Mo) deposit in northern Chile. Our images show that low Vp/Vs (~ 1.55–1.65) anomalies, extending to ~ 5–15 km depth, coincide with the surface expression of known porphyry copper deposits and prospects, as well as delimit structures that host orebodies and related hydrothermal alteration zones. Medium Vp/Vs (~ 1.68–1.74) and high Vp/Vs (Vp/Vs ~ 1.85) bodies correspond to intermediate-felsic plutonic precursors for porphyry intrusions and mafic magma reservoirs that underlie shallower orebodies, respectively. Imaging these precursor and parental plutons is crucial to the identification of orebodies as they act as the source of fluids for porphyry copper generation. This study demonstrates the potential of local earthquake tomography as a tool to identify future deep mineral resources with minimal environmental impact.
... Rapid synmineral uplift and concomitant erosion can result in highly telescoped porphyry Cu systems, in which advanced argillic lithocaps overprint and reconstitute deeper alteration, including quartz-veined potassic zones (Sillitoe, 1994;Sillitoe and Perelló, 2005;Tosdal and Dilles, 2020;Figs. 1b, 3d, e). ...
... Nonetheless, several regional-scale geologic features may be used as proxies. Favorable arc segments for telescoped porphyry systems are likely to be characterized by thickskinned, high-angle reverse faulting, confinement of porphyry intrusions to fault-bounded basement blocks, and little or no volcanism contemporaneous with porphyry Cu formation (Sillitoe and Perelló, 2005;Perelló et al., 2023;Fig. 1b). ...
Hypogene porphyry Cu deposits, unaffected by supergene enrichment, are generally perceived as relatively low-grade orebodies, in keeping with a current average production grade of 0.53% Cu. Nonetheless, all or large parts of some deposits exceed 1% Cu, and smaller deposit components can be much higher in grade, locally >6% Cu. In view of the major economic and environmental benefits afforded by high grades, we briefly review geologic features and factors conducive to development of >1% hypogene Cu ore in porphyry Cu systems. Intense quartz veinlet stockworks, magmatic-hydrothermal breccias, vuggy residual quartz or vein systems in telescoped lithocaps, proximal skarns, carbonate-replacement mantos and pipes, low-permeability barriers, and reactive mafic host rocks—either alone or in various combinations—are identified as particularly favorable features because they enhance rock permeability and/or reactivity; most of them may be taken into account when planning and conducting exploration programs, thereby maximizing the chances of high-grade porphyry Cu discoveries.
... La Franja Metalogénica del Cretácico se ubica entre los 21 y 34°S en la Cordillera de la Costa del norte de Chile, la cual alberga depósitos minerales tipo magnetita-apatito o iron oxide-apatite (IOA) o tipo Kiruna, óxidos de hierro-cobre-oro o iron oxide-copper-gold (IOCG) y tipo pórfido Cu-(Mo)-(Au) de edad Jurásica-Cretácica (e.g., Sillitoe, 2003;Sillitoe y Perelló, 2005; Figura 1). Actualmente, los depósitos IOA son la fuente más importante de hierro en Chile, mientras que los depósitos tipo IOCG y pórfido Cu-Mo corresponden a la segunda y primera fuente de Cu del país, respectivamente. ...
... La Cordillera de la Costa del norte de Chile hospeda depósitos estratoligados Cu-Ag o "tipo Manto", magnetita-apatito o iron oxide-apatite (IOA), óxidos de hierro-cobre-oro o iron oxide-copper-gold (IOCG) y pórfidos Cu-(Au-Mo) (e.g., Sillitoe y Perelló, 2005). La formación de una variedad de depósitos estratoligados Cu-(Ag), IOA e IOCG se relaciona con el desarrollo de un arco magmático bajo un régimen extensivo de subducción entre el Jurásico tardío al Cretácico Inferior (Oyarzún et al., 2003;Barra et al., 2017;Richards et al., 2017;Figura 4b). ...
El Distrito Peñablanca se encuentra emplazado en la Franja Metalogénica del Cretácico, Región de Coquimbo. Esta franja se caracteriza por la ocurrencia de depósitos estratoligados Cu-Ag, iron oxide-apatite (IOA), iron oxide-copper-gold (IOCG) y pórfido Cu-(Mo)-(Au).
En este trabajo se presenta una caracterización de la geología en profundidad mediante la descripción de muestras de mano y secciones transparentes-pulidas obtenidas de testigos de sondajes, y de la geología superficial a partir de la integración de estudios anteriores, incluyendo observaciones de terreno, geoquímica y geofísica, lo cual fue sintetizado en una sección y modelo geológico esquemático para el Distrito Peñablanca.
El Distrito Peñablanca corresponde a una serie de vetas mineralizadas del tipo IOCG e IOA hospedadas en rocas intrusivas Cretácicas de composición diorítica a granodiorítica. Se identifican cinco eventos de alteración hidrotermal y mineralización. El Evento I corresponde a una alteración sódica (albita). El Evento II corresponde a una alteración potásica (biotita, cuarzo, magnetita, calcopirita ± pirita), mientras que el Evento III a una alteración clorita-esmectita (± epidota ± calcita ± pirita). El Evento IV corresponde a una alteración calco-sódica (actinolita, apatito, albita, escapolita, titanita, magnetita, pirita, calcopirita, ilmenita, hematita). El evento V, de carácter supérgeno, incluye crisocola, malaquita, atacamita, antlerita, hematita (martita) y limonitas (goethita, hematita y jarosita).
Las vetas mineralizadas del Distrito Peñablanca se asemejan a las del tipo Montecristo emplazadas en intrusivos del Jurásico, y a las de la Higuera emplazadas en intrusivos del Cretácico, las cuales representarían una transición entre un depósito IOA en profundidad a un depósito IOCG hacia la superficie. Adicionalmente, la presencia de vetillas de cuarzo con mineralización de calcopirita asociada a alteración potásica (Evento II), la presencia de contenidos de Mo en superficie, así como la relación directa con cuerpos intrusivos, sugieren la ocurrencia de un posible evento tipo pórfido cuprífero dentro de la zona de estudio. Esto último es consistente con la relación genética que algunos autores han propuesto para los depósitos IOCG y los pórfidos Cu-(Mo)-(Au) de la Franja Metalogénica del Cretácico.
... However, only one porphyry deposit (Shaxi Cu-Au deposit; Figure 1B) has been discovered in the MLYRMB as the middle stage of porphyry Cu-Au mineralization. Since porphyry deposits are characterized by linear clusters and 10-20 Ma periodic mineralization, e.g., deposits at the Andes, South America; Gangdese, Tibet [35,36], there is thus great exploration potential for porphyry Cu-Au deposits (between 133-125 Ma) in this area [11,19,37,38]. ...
... Interestingly, the porphyry deposits in the MLYRMB have the same characteristics of linear cluster and periodic mineralization as typical porphyry deposits [19,35,36]. Furthermore, relatively high contents of the platinum-group element (PGE) have developed in the porphyry Cu-Au systems, for instance, Santo Tomas II in Philippines [80] and Dexing in China [81], especially in the magnetite-bearing assemblages of potassic alteration zones [82]. ...
Different ore deposit types may evolve from a common magmatic-hydrothermal system. Establishing a genetic link between different deposit types in an ore cluster can not only deepen the understanding of the magmatic-hydrothermal mineralization process but can also guide exploration. Both the Nihe iron-oxide-apatite (IOA) deposit and the Shaxi porphyry Cu-Au deposit in the Lower Yangtze Valley, Anhui, Southeast China, formed in the Luzong Cretaceous volcanic basin at~130 Ma. We examined a temporal-spatial and potential genetic link between these deposits based on stratigraphic lithofacies sections, biotite and clinopyroxene mineralogical chemistry, zircon chronology, Hf isotopes, and trace elements. Stratigraphy, petrology, mineralogical chemistry, and available fluid inclusion results support that the emplacement depth of the Nihe ore-related porphyry is shallower than that of the Shaxi porphyry. The magmatic zircon and hydrothermal zircon from Nihe provided U-Pb ages of 130.6 ± 0.7 Ma and 130.7 ± 0.7 Ma, respectively. The magmatic zircon U-Pb age (130.0 ± 0.8 Ma) of Shaxi overlaps with its molybdenite Re-Os age (130.0 ± 1.0 Ma). The agreement between the mineralization and porphyry emplacement ages of Nihe and Shaxi indicates a temporal coincidence and supports a possible genetic link between the two deposits, considering their close spatial relationship (in the same ore district, 15 km). The zircon Hf isotopes and trace elements support the evolution of both deposits from an enriched lithospheric mantle, although the Shaxi deposit may have experienced contamination of the Jiangnan-type basement. Both deposits lie above the fayalite-magnetite-quartz buffer, but the Nihe magmatic zircons are of lower temperature and less oxidized than that of Shaxi. The much higher Eu/Eu* and Yb/Dy values of zircons from Shaxi are likely caused by the suppression of early plagioclase crystallization and the prevalence of amphibole fractionation, thus indicating more hydrous content of the Shaxi ore-related magma. Additionally, the Shaxi ore-related porphyry has higher zircon Hf concentrations, suggesting that the porphyry Cu-Au deposit has experienced a greater degree of magma fractionation. Our study highlights that the Nihe IOA deposit and the Shaxi porphyry Cu-Au deposit have a common magma source, while different extent of crust contamination, magma oxidation state, hydrous content, and degree of magma fractionation collectively result in the two distinct ore deposits. This possible genetic link suggests a great potential of porphyry Cu-Au-PGE mineralization in the Middle-Lower Yangtze River metallogenetic belt, especially in the deep part of the IOA district in the Luzong Cretaceous volcanic basin.
... The Río Blanco-Los Bronces district is situated in the Miocene-Pliocene volcanic arc (western Cordillera) of the southern Central Andes at about 33.15°S longitude, 70.25°W latitude, and 3,500 to 4,000 meters above sea level. The district is located in the Central Chilean copper belt described by Sillitoe and Perelló (2005) along with two other supergiant porphyry copper deposits: Los Pelambres-El Pachón and El Teniente (Fig. 1). In a geodynamic context, the Central Chilean belt is within the "flat-slab" region of the Andes, which is characterized by a shallow dip of the subduction zone and a lack of post-Pliocene volcanism, both features being attributed to subduction of the Juan Fernández Ridge (e.g., Kay and Mpodozis, 2001;Yañez et al., 2001). ...
... In a geodynamic context, the Central Chilean belt is within the "flat-slab" region of the Andes, which is characterized by a shallow dip of the subduction zone and a lack of post-Pliocene volcanism, both features being attributed to subduction of the Juan Fernández Ridge (e.g., Kay and Mpodozis, 2001;Yañez et al., 2001). Kay et al. (1999) and Sillitoe and Perelló (2005) reviewed possible relationships between copper mineralization and geodynamic factors for the Central Andean copper province as a whole (e.g., crustal thickening and uplift, ridge subduction, subduction erosion and arc migration, trans-arc lineaments), while Skewes and Stern (1995) discussed how these factors may relate to the genesis of the Río Blanco-Los Bronces and other supergiant copper deposits in the Central Chilean belt. ...
Tourmaline-cemented breccia bodies host much of the ore in the Río Blanco-Los Bronces porphyry Cu-Mo deposits. We determined the chemical and B isotope composition of tourmaline as well as S isotope ratios of anhydrite and sulfide minerals to shed light on the composition and origin of mineralizing fluids. Also, the utility of tourmaline as an indicator mineral was tested by comparing mineralized and barren breccias. Tourmaline in mineralized samples has a narrow Mg range (1.5–2 apfu) and variable, generally low Al contents (4–6.5 apfu). A strong negative correlation of Al with Fe indicates monovalent substitution of Al and Fe3+, implying relatively oxidizing fluids. In contrast, tourmaline from barren breccias has a narrower Al range (6–7 apfu), lower and more variable Mg (0.2–2.5 apfu), and a strong negative Mg-Fe correlation, suggesting more reduced fluids with a dominance of Fe2+. These features and the implications of redox contrast may have exploration significance. Tourmaline from all breccia samples yielded δ11B values from 1.8 to 7.9‰. A magmatic source of boron is concluded from the identical B isotope values of granite-hosted tourmaline in the district (1.2–7.7‰) and from the similar range of regional volcanic and porphyry rocks in the Central Andes. The δ34S values of coexisting anhydrite (11.6–14.5‰) and chalcopyrite (–1.5 to –0.2‰) in mineralized breccia give S isotope exchange temperatures of 377° to 437°C, consistent with fluid inclusion temperatures. Total sulfur δ34Sfluid estimates between 1.4 ± 3.9 and 8.8 ± 1.3‰ are broadly consistent with a magmatic source but not well constrained. However, published O and H isotope ratios of quartz and tourmaline from the Río Blanco-Los Bronces breccias have a clear magmatic signature, so this is the preferred scenario. Mass balance simulations of the boron budget show that typical magma flux rates, water contents, and boron concentration for the Central Andes can produce the estimated 107 tons of boron in the Río Blanco-Los Bronces breccias within the 4-m.y. duration of porphyry intrusions if (1) magma accumulated and evolved at midcrustal levels before emplacement and (2) boron partitioned strongly to the fluid phase (DBfluid/melt> 3).
... The distinct Andean segments present in Chile interact with the large-scale atmospheric circulation which defines latitudinal variations in precipitation and temperature, and therefore, climate (Inzunza, 2006). Furthermore, variable metallogenic provinces are observed in west to east profiles as a result of the eastward migration of the active arc since the Jurassic (Sillitoe and Perelló, 2005). These unique and variable characteristics make Chile an ideal country to study As variations in an active tectonic environment. ...
... Important volcanic edifices of this transect correspond to Nevado de Tres Cruces, Cerro Solo, Incahuasi, El Muerto, and Nevado Ojos del Salado (Fig. 2), which show compositions that range from dacite to andesite and basalt, and are found within the highest elevation volcanic zone of the planet (Mpodozis et al., 1996). In addition, this region is related to important metallogenic belts which show a north-south trend and were formed between Jurassic (IOCG belt), Paleocene (Cu), Eocene-Oligocene (Cu; Sillitoe and Perelló, 2005), and Miocene (Au) periods (Vila and Sillitoe, 1991). ...
Globally, arsenic (As) contamination is widespread in hydrological systems and the link between As enrichment and regional tectonic and climatic factors is still not well understood in orogenic environments. This work provides new insights on the relationship between As, tectonics, and climate by assessing the hydrogeochemistry of Chile, an active subduction zone with highly diverse natural settings. Chosen study sites include fluvial courses along four regional transects connecting the Chilean coast to the Andes Cordillera in the northern, central, and southern areas of the country.
Results indicate that As concentrations in surface water and fluvial sediments show a general positive correlation to crustal thickness and they tend to decrease progressively from northern to southern Chile. In contrast, As concentrations are negatively correlated to average annual precipitation which shows a significant increase toward southern Chile. From a regional tectonic perspective, northern Chile presents greater Andes shortening and higher crustal thicknesses, which induces increased crustal contamination and As content at the surface. Extremely low precipitation rates are also tied to local As enrichment and a sediment-starved trench that might favor higher plate coupling and shortening. On the contrary, decreased shortening of the Andes in southern Chile and related lower crustal thickness induces lower crustal contamination, thus acting as an As-poor provenance for surficial sediments and surface water. High precipitation rates further induce dilution of surface water, potential mobilization from the solid phase, and a significant amount of trench sediments that could induce lower plate coupling and lower shortening.
At the local scale, a low potential for As mobilization was found in northern Chile where a greater distribution of As-bearing minerals was observed in sediments, mostly as finer particles (<63 μm). The abundance of Fe-oxides potentially acts as a secondary surficial sink of As under the encountered physicochemical conditions.
... El yacimiento Rio Blanco -Los Bronces se localiza en un cinturón de mineralización conocido como franja metalogénica de pórfidos de Cu-Mo del Mioceno tardío-Plioceno temprano (Toro et al., 2012) en la Cordillera Principal de Chile central entre las latitudes 32° y 35°S (Sillitoe y Perelló, 2005). La franja metalogénica se encuentran los yacimientos de categoría mundial Los Pelambres-El Pachón, Río Blanco-Los Bronces y El Teniente, cercano al límite de la Zona Volcánica Sur (ZVS) y el segmento de "flat-slab" o segmento de bajo ángulo (Skewes y Stern, 1994). ...
... El distrito Rio Blanco -Los Bronces se localiza en sector sur de la franja metalogénica del Mioceno al Plioceno inferior, la cual se extiende de manera semicontinua por aproximadamente 6000 km a lo largo de la cordillera, desde el suroeste de Colombia hasta la parte central de Chile y Argentina. Regionalmente el yacimiento se ubica en la sub-franja de Chile Central, la cual se extiende por aproximadamente 400 km a lo largo de la Cordillera de Los Andes, entre los 32° y 35° latitud sur (Sillitoe y Perelló, 2005). La mitad sur de esta sub-franja, desde aproximadamente los 33°S, es donde se encuentran los principales yacimientos de cobre, la cual sobreyace el segmento norte de la zona de subducción normal caracterizada por la presencia del volcanismo activo de la Zona Volcánica Sur. ...
The analysis and validation of data is a practice that is fundamental to ensuring that any measured data is highly reflective of reality, which allows for greater confidence in the modelling of a mining project.
The use of televiewer is a methodology that has efficiently contributed to the characterization of the orientation of deep structures, such as: seams, veinlets, fractures and faults. At the same time, its impact has generated significant improvements in the implicit 3D modelling and the structural models of the ‘Los Bronces’ mine. The uplifting of this information is considered mainly in the Superintendence of Geotechnics focused on geomechanics and structural geology, however, despite the fact that this data is available, other departments do not use it. On one side, there haven’t been studies focused on evaluating the potential and contributions that this data could generate for other areas while, on the other side, there haven’t been validations of this technique so that it may be applied in geological interpretation.
Faced with these circumstances, this study documents an analysis of optical and acoustic televiewer data in order to take advantage of this available information, generate continuous improvements and use it in the exploratory field. The objective is to determine trends in the orientation of veinlets through a data selection criteria designed to comprehend the structural behavior and define predictive exploratory indicators.
Based on the statistical and graphical analyzes of intrusive rocks, a clear trend is evidenced with regards to the direction of veinlets in alteration zones, generally displaying a first-order group in an almost E-W direction and a second-order group in a N-S direction. Other groups of trending veinlets are also identified in a subordinate manner. Other analyzes of veinlets classified according to their type also indicate trends, which have a direct correlation with the larger structures described in the structural models, potentially having the capacity to comprehend the direction of the emplacements of structures and allowing for interpretations to be generated with greater confidence. Finally, and as a generated impact, the data allows for complementing missing information, for example, in reverse air boreholes and to mostly validate the indirect mapping through quantitative data.
... The Miocene metallogenic belt of northern Peru and southern Ecuador includes numerous Au-rich porphyry and epithermal Au-Ag deposits (Fig. 1A). These formed between 20 and 6 Ma (Macfarlane et al., 1994;Noble and McKee, 1999;Davies, 2002;Gustafson et al., 2004;Davies and Williams, 2005;Longo, 2005;Sillitoe, 2005;Schütte, 2009;Thomas et al., 2011;Montgomery, 2012). The region includes the Hualgayoc (Longridge, 2016), Alto Chicama (Montgomery, 2012;Cerpa et al., 2013), and Cajamarca mining districts; the latter is the world's largest cluster of high-sulfidation epithermal gold deposits and includes Yanacocha (Longo, 2005;Chiaradia et al., 2009a;Teal and Benavides, 2010;Fig. ...
... 1A). This belt, extending between 3° S and 8° S, marks the transition from the Central to the Northern Andes (Mitouard et al., 1990;Jaillard et al., 2000;Sillitoe, 2005). Several distinct domains, some interpreted as exotic terranes, are defined (Fig. 1B). ...
The Rio Blanco porphyry Cu-Mo deposit occurs at the north end of the Miocene metallogenic belt of northern Peru. It has a thick supergene enrichment blanket; while normal for hyperarid Chile, this is unusual in mountainous, cloud forest terrain. Rio Blanco is hosted by the Portachuela batholith. Zircon U-Pb dating shows that the youngest part of the batholith was emplaced at 12.43 ± 0.13 Ma.
The deposit formed during three magmatic-hydrothermal cycles. Cycle 1, by far the most important, occurred at 11.50 ± 0.17 to 10.92 ± 0.14 Ma (zircon U-Pb). Two intermineralization intrusions caused early potassic and propylitic alteration. This was then overprinted by a blanket of quartz-sericite, grading down into sericite-chlo-rite alteration. Cycle 1 was finally cut by a quartz-sericite–cemented breccia, which contains the highest-grade hypogene Cu-Mo grades. A cycle 1 molybdenite-bearing vein has a molybdenite Re-Os model age of 11.43 ± 0.16 Ma. Molybdenite Re-Os dating of the quartz-sericite–cemented breccias shows brecciation occurred at 11.28 ± 0.24 to 11.11 ± 0.18 Ma.
Cycle 2 was restricted to the east side, where narrow porphyritic dacite 1 dikes (dated by zircon U-Pb at 10.62 ± 0.16 Ma) show biotite alteration and economic copper. Cycle 3, at 10.02 ± 0.12 to 9.06 ± 0.09 Ma (zircon U-Pb), was triggered by a swarm of NE-striking quartz-plagioclase porphyry and porphyritic dacite 2 dikes. Alteration was milder, and this cycle did not introduce economic copper. Nonmineralized pebble dikes cut the system, emanating from a major diatreme, about 3 × 1.3 km in size, on the north side of the deposit.
The magmatic-hydrothermal history spanned about 2.5 m.y., with economic mineralization over about 1.48 m.y. However, metals were mostly introduced during cycle 1, which lasted approximately 0.58 m.y. Our work shows that while multiple magmatic-hydrothermal cycles produced Rio Blanco, sufficient metals were introduced to form a giant porphyry deposit within a single magmatic-hydrothermal cycle.
... The El Indio belt (Fig. 2) occurs within a north-south trending graben system, controlled by high-angle faults, that comprises Carboniferous-Triassic-aged basement blocks Fig. 1 a Location of the Taguas Project within the Pampean flat slab segment, in the northwest of San Juan Province, Argentina. Porphyry and high-sulfidation epithermal belts (Maricunga, Vicuña, El Indio, and Central Chile) are shown (Siddeley and Araneda 1990;Vila and Sillitoe 1991;Sillitoe and Perelló 2005;Perelló et al. 2023;Gamonal et al. 2024). The main deposits of El Indio belt are indicated with red symbols. ...
Cerros Taguas is one of the high-sulfidation epithermal Au-Ag deposits (131.35 Mt @ 0.29 g/t Au, 8.8 g/t Ag, 0.11% Cu) of the Taguas project, located in the northern sector of the El Indio belt (~ 29°S), Central Andes, Argentina. Zircon LA-ICP-MS U-Pb dating of a rhyolitic tuff that hosts Au-Ag mineralization constrain the timing of volcanism to the middle Miocene (12.14 ± 0.14 to 11.85 ± 0.26 Ma). Above 3800 m.a.s.l., the rocks display advanced argillic alteration, characterized by alunite + pyrophyllite + dickite ± diaspore ± topaz. Hypogene alunite associated with epithermal Au-Ag mineralization yielded a ⁴⁰Ar/³⁹Ar plateau date of 9.5 ± 0.4 Ma. Below 3800 m.a.s.l., the presence of sericitic alteration (muscovite + illite + quartz) and a molybdenum halo associated with molybdenite-bearing B-type and pyrite ± quartz D-type veins suggests a transition from epithermal to porphyry-style mineralization. Molybdenite in quartz-dominated B-type veins and molybdenite ± quartz veins cross-cutting the rhyolitic tuff yielded ID-NTIMS Re-Os dates of 10.60 ± 0.06 and 10.48 ± 0.05 Ma. A nominally older molybdenite ID-NTIMS Re-Os date (11.10 ± 0.11 Ma) was obtained for the hydrothermal cement of a breccia. The timing of molybdenum mineralization at Cerros Taguas was broadly coeval with the emplacement of inter-mineralization porphyritic stocks and slightly older than molybdenite mineralization in the nearby Valeriano and El Encierro porphyry deposits. The occurrence of a porphyry-style mineralization at Cerros Taguas reflects the prospectivity for porphyry deposits beneath Miocene-age volcanic rocks and advanced argillic alteration zones in the northern sector of the El Indio belt.
... Thermochronological work by Sanchez et al. (2017) has also suggested that rapid uplift occurred at 40 to 30 Ma at Centinela; hence exhumation and the concomitant accumulation of synorogenic gravels occurred shortly after the formation of the hypogene sulfide mineralization at Encuentro (e.g., Perelló et al., 2004Perelló et al., , 2010Mpodozis et al., 2009;Riquelme et al., 2018). In agreement with the regional setting of the late Eocene to early Oligocene porphyry Cu belt of northern Chile (e.g., Maksaev and Zentilli, 1999;Sillitoe and Perelló, 2005) and southern Peru (Perelló et al., 2003). ...
The enormous economic potential of porphyry systems makes them the most explored and researched ore deposits in the last century. Despite all these efforts, debate remains around the timing and pressure-temperature conditions of metal introduction and precipitation. In this study, we document the abundance and spatial distribution of each vein type in the porphyry environment, followed by cathodoluminescence (CL) imagery, Ti-in-quartz, and fluid inclusion microthermometry to estimate the timing and conditions of metal-bearing sulfide deposition. Below, we provide evidence that most of the Cu-Fe sulfides were deposited early in the evolution of the system, at relatively high temperature, and synchronously with K-silicate alteration.
We recognized a sequence of at least five porphyry intrusions that are linked spatially, temporally, and genetically to the bulk of Cu-Au mineralization. Each Encuentro porphyry developed a similar sequence of biotite veinlets, early dark micaceous halos, and A quartz veins with Au-bearing chalcopyrite ± bornite. A veins are the most abundant at Encuentro and constitute 80 vol % of all quartz veins in the deposit. Their distribution and abundance define the shape and geometry of the quartz vein stockwork and the Cu and Au grade shells. The abundance of A veins, Cu-Fe sulfide content, and Cu and Au grades progressively decreased in each cycle of intrusion, consistent with a decline of the magmatic-hydrothermal fluid flux with time. Continuous extraction of Cu-Au–rich fluids impoverished the hidden underlying magma chamber in these metals but generated younger Mo-rich fluid that formed B veins and later quartz-anhydrite-molybdenite (QAM) veins. This process produced Cu-Au and Mo mineralization zones that are decoupled in time and space at the deposit scale. Single-phase intermediate-density fluid inclusions were trapped in A, B, and QAM veins and may include parental fluids modified by postentrapment processes. Depressurization of similar fluids from lithostatic to near hydrostatic pressures along near adiabatic paths caused unmixing to form brine-rich and vapor-rich fluids and furthermore caused the quartz precipitation in these veins and formation of associated K-silicate alteration at >500°C and 0.4- to 1.0-kbar pressures (~3- to 4-km depth). Copper-Fe and Mo sulfides in A, B, and QAM veins were found intimately associated with high-temperature bright- and gray-CL quartz, K-feldspar, and anhydrite, implying that vein formation and sulfide deposition occurred concomitantly during K-silicate alteration.
The K-silicate alteration and associated early veins are cut by four vein types stable with sericitic alteration. Three of these vein sets are closely related and zoned upward and outward from deep C-type chalcopyrite-pyrite veinlets, to chlorite-white mica-chalcopyrite-pyrite veinlets, to distal pyrite-rich D veins with well-developed sericitic selvages. The spatial zonation and similar mineral assemblages suggest that these veins were produced by the same fluid, which was more deeply sourced, less voluminous, and cooler than early fluids and, therefore, lower in pH upward as a result of acid dissociation. The youngest fluids at Encuentro are associated with the formation of tourmaline veins along the eastern side of the deposit, which cut and offset all previous veins. Sericitic alteration and associated veins formed at 350° to 460°C and 0.2 to 0.4 kbar (~2.4- to 5-km depth) via depressurization and cooling through the pressure-temperature zone of retrograde quartz solubility, consistent with paucity of quartz in C-type, D, and tourmaline veins. Liquid-rich fluid inclusions trapped in tourmaline veins indicate that the latest fluids remained as single-phase without intercepting the brine-vapor solvus. Veins stable with sericitic alteration are volumetrically minor in the center of the deposit, only contain Cu-Fe sulfides when transgressing high-grade zones, and do not correlate with Cu and Au grade shells, implying that most of the Cu they contained was derived from early-deposited sulfides.
... Estos depósitos se formaron bajo un contexto tectónico de régimen compresivo y de migración magmática hacia el este desde el Cretácico Tardío hasta el Cenozoico. (Sillitoe, 2005;Richards et al., 2017;Creixell et al., 2020) ...
La zona de estudio, situada entre los 31° y 31° 30’ S dentro de la Franja Metalogénica Cretácica, alberga los Distritos El Espino, Llahuín y La Crucita en secuencia de oeste a este. Esta área ofrece una oportunidad única para analizar y comprender las características tectono-metalogénicas que influyen en la formación de diversos estilos de mineralización, tales como óxidos de hierro-cobre-oro (IOCG), pórfidos Cu-Au-Mo y epitermales de baja a intermedia sulfidización, entre otros, dentro del contexto del flat-slab Pampeano, donde se produce una coalescencia entre la Cordillera de la Costa y la Cordillera Principal.
En este trabajo se presentan nuevos datos cinemáticos, regionales y metalogénicos del Distrito La Crucita, los cuales se integran con datos recopilados previamente por diversos autores y empresas mineras de los Distritos El Espino y Llahuín. Se definieron dos dominios estructurales (este y oeste) y se confeccionó una sección estructural que abarca los tres distritos (SO-NE). Además, se estudiaron las geometrías en profundidad y se analizó la cinemática del Distrito La Crucita. Finalmente, se relacionaron estos resultados con las arquitecturas estructurales de los Distritos el Indio/Tambo (epitermales de Au) y Pelambres (pórfido Cu-Mo), ubicados al norte y sur de la zona de estudio.
Los Distritos El Espino, Llahuín y La Crucita presentan arquitecturas estructurales asociadas a procesos de inversión tectónica y reflejan un cambio tectónico regional desde un periodo extensional a uno compresivo durante el Cretácico. A nivel local, se observan cambios en los campos de deformación. Se observa una transición desde cinemáticas compresivas (presión E-O) a componentes de rumbo con características extensivas. Esto genera tensiones principalmente verticales a subverticales con direcciones NE-SO/NO-SE, oblicuas al régimen tectónico regional. Las cinemáticas de rumbo habrían favorecido la formación de los diversos tipos de depósitos minerales del Cretácico, como IOCGs, pórfidos Cu-Au-Mo, epitermales, entre otros, y representan un factor de primer orden en la mineralización, al igual que en la zona del Distrito El Indio/Tambo y Distrito Pelambres.
... Porphyry Cu systems, one of the most important types of copper deposits, are usually situated in linear patterns extending from tens to hundreds of kilometers, such as the porphyry system in the Andes (Sillitoe and Perelló, 2005;Sillitoe, 2010). Porphyry Cu deposits generally have consistent and extensive hydrothermal alteration zoning that includes potassic, phyllic, advanced argillic, and propylitic alteration zones (Lowell and Guilbert, 1970;Sillitoe, 2010). ...
The Chagai porphyry Cu belt in Pakistan is an important metallogenic terrain extending approximately 400 km in an east-west direction. Most of the known porphyry Cu deposits, such as the world-class Reko Diq deposit and Saindak deposit, are located in the western Chagai belt. In this study, the ZY1-02D hyperspectral data acquired by a recently launched spaceborne imaging spectrometer with 166 bands within a 0.4- to 2.5-μm spectral region were used to map mineral information over 8,000 km2 for exploring potential targets of porphyry Cu mineralization in the western Chagai belt. False color composite, spectral angle mapper, and wavelength position mapping methods were used in this research leading to the identification of a series of alteration minerals (including muscovite [sericite], kaolinite, alunite, epidote, chlorite, and calcite) from ZY1-02D data. The alteration mineral maps derived from ZY1-02D data match well with the known deposits and field inspections. Twenty-three new targets were identified as potential porphyry Cu mineralization targets for further exploration in the study area. Three targets, north of Saindak, Koh-i-Sultan, and Durban Chah, and six alteration sites in the southwest of Durban Chah, were inspected in the field, and Cu-Au mineralization was confirmed in all these inspected areas. As the ZY1-02D hyperspectral data covers most of the land area of the earth, this study provides new insights for mineral exploration and lithologic mapping in remote regions.
... The FNVC is a preeminent Cu-Au district hosted in the Sierras Pampeanas of northwest Argentina, on the southern margin of the Puna physiographic province, in South America ( Fig. 1; Halter et al., 2004a;Sasso and Clark, 1998). As a back-arc expression of the highly productive Central Andean Miocene-Pliocene metallogenic belt (Rubinstein et al., 2021;Sillitoe and Perelló, 2005), it hosts the Cu-Au Bajo de la Alumbrera and Cu-Au-Ag Agua Rica porphyries as well as the Au-Ag intermediate sulfidation, epithermal Farallon Negro deposits within an andesitic to dacitic volcanic complex (Halter et al., 2004a;Proffett, 2003;Sasso, 1997). ...
... Monogenetic mafic volcanism from Haag et al. (2019) and Morfulis et al. (2020). Cu-Au porphyry from Sillitoe and Perelló (2005). Note the presence of the three Tranversal Volcanic Chains (TVCs). ...
... Finally, we want to highlight that the sub-volcanic intrusive bodies (e.g., the Sierra Gorda, Spence, and the Lomas Bayas mines, see Fig. 3), associated with the Upper Cretaceous-Paleocene metallogenetic belt (Sillitoe, 1992;Sillitoe and Perelló, 2005;Camus, 2003), were emplaced in a structural position related to partly or entirely reversereactivated normal faults and/or inversion structures such as short-cut faults or inversion anticline-and-syncline folds (Fig. 13). The position and distribution of the Upper Cretaceous and Paleocene magmatic and volcanic arc had a strong structural control, and its development would be related to positive tectonic inversion processes, and possibly to the continued development of thin-skinned thrust systems during the early Cenozoic. ...
... They represent a mix of regional N-S-to-NNE strike-slip faults, interpreted as the main structural styles developed during the Eocene and the Oligocene (Steinmann, 1929;Maksaev and Zentilli, 1999;Mpodozis and Perelló, 2003;Niemeyer and Urrutia, 2009;Charrier et al., 2009). The magmatism was associated with the emplacement of syn-orogenic magmatic bodies and giant porphyry-copper deposits (Sillitoe and Perelló, 2005). ...
The relationship between parallel and oblique to the orogen faults and the magmatic evolution is key to understanding the evolution of a hot orogen, such as the Central Andes. The Andean orogenesis along the southern Central Andes, during the Neogene is characterized by regional compression and magmatic processes associated with subduction. The outcome of this dynamic interaction between plate tectonics and magmatism has generated reverse, normal and strike-slip faults, both parallel and oblique to the trench. Despite the progress made on studying these fault systems, both their relationship with the stress field and their role in magma propagation into the shallow crust are still enigmatic. In this work, geomorphological observations are coupled with kinematic and dynamic analyses, as well as with kinematic forward modeling, to reconstruct the evolution of two main faults affecting the western slope of the Puna plateau, the Barrancas Blancas fault and the Tocomar fault, during the Neogene. The obtained data reveal that, between 17 and 10 Ma, the Barrancas Blancas fault had reverse activity, while the Tocomar fault had left-lateral strike-slip movement. At 10 Ma, the area was affected by the coeval reactivation of the Volcan de Punta Negra fault and the right-lateral activity of the Tocomar fault. During the last stage, strike-slip movement along the Tocomar fault favored the rise of magma, while the hydrothermal activity evolved along the Barrancas Blancas fault. The study results reveal that the oblique-to-the-orogen faults play a role in the segmentation of the reverse parallel-to-the-trench deformation and control the position of the volcanic centers, while the parallel-to-the-orogen faults control the relief development and the evolution of hydrothermal systems. The proposed model helps in understanding how magma rises to the surface associated with movement along reverse and strike-slip faults during the thickening of the crust.
... The Andes host the most important porphyry Cu-Mo-Au ore belts in the world (Mao et al., 2018;Sillitoe and Perelló, 2005). The deposits in these belts were formed mainly during the Cenozoic, although some smaller Jurassic-Cretaceous porphyry deposits have been discovered (Clark et al., 1990;Drobe et al., 2013;Maksaev et al., 1999), which caused the northwestward magmatic migration and widening of the Toquepala arc ( Fig. 2C) (Mamani et al., 2010). ...
The Paleocene–Eocene southern Peru metallogenic belt contains numerous very large to supergiant porphyry Cu‒Mo deposits. The deposits were dated previously as coeval with the Incaic I orogeny at ca. 60 Ma. However, tectono-magmatic processes during the formation of the deposits are poorly constrained. Here, we integrate published geochronological, geochemical, and mineralogical data from barren and ore-related granitoids in the region. The syn-orogenic unit (60–53 Ma) has significantly higher average ratios of Sr/Y (104.4), La/Yb (29.6), Dy/Yb (1.9), and EuN/Eu* (1.07) than the pre-orogenic unit (69–60 Ma; Sr/Y = 18.6, La/Yb = 11.5, Dy/Yb = 1.7, and EuN/Eu* = 0.66). The syn-orogenic unit exhibits high Dy/Yb ratios in relatively primitive rocks and has a lower average Dy/Yb(zircon) ratio (0.23) and higher EuN/Eu*(zircon) ratio (0.43) than the pre-orogenic unit (Dy/Yb(zircon) = 0.29 and EuN/Eu*(zircon) = 0.21). These integrated data suggest that the syn-orogenic magmas underwent high-pressure, garnet-dominated fractionation prior to amphibole-dominated fractionation, distinct from the pre-orogenic magmas which underwent low-pressure, plagioclase-dominated fractionation. Comprehensive investigation of the geological background suggests that the geochemical variations between pre- and syn-orogenic units were caused by the long-term evolution of mantle-derived magmas at the crust‒mantle boundary during arc compression, instead of crustal thickening. Fractionation of ferric iron-depleted minerals (e.g., garnet and amphibole) in the mantle-derived basaltic magmas probably has positive effects on magmatic fertility. The dataset presented highlights the critical role of high-pressure differentiation, thus providing an insight into the relationship between the arc compressional regime and giant porphyry Cu deposit formation in the Andes. Zircon trace elements can be useful indicators for porphyry deposit exploration in the Toquepala arc in southern Peru. However, the regional tectonic settings of the Andean arcs should be studied thoroughly before applying these indicators.
... A late Middle Eocene (43 - Fig. 1. A. Map showing the location of the Late Oligocene porphyry-epithermal belt relative to other copper belts of the Andes. Modified from Sillitoe and Perelló (2005). The position of the belt within Peruvian flatslab (amagmatic flat-slab) and South American Pacific margin (modified after Ramos and Folguera, 2009). ...
... Early, intermineral, and late-mineral porphyry phases are recognized and span porphyry copper formation. Molybdenite accompanying the copper mineralization was dated by the Re-Os method at 9.95 ± 0.04 Ma, confirming that the porphyry system is part of the Miocene to early Pliocene metallogenic belt of northern Chile and contiguous Argentina (Sillitoe and Perelló, 2005) and intermediate in age between the Veladero (11.9-10.3 Ma) and Pascua-Lama (9.4-8.1 Ma) high-sulfidation epithermal deposits (Bissig et al., 2001;Holley et al., 2016;Figs. ...
Exploration for porphyry copper deposits beneath barren or poorly mineralized, advanced argillic lithocaps is becoming commonplace; however, there have been few discoveries except in cases where the copper ± gold ± molybdenum mineralization has been partly exposed, typically as a result of partial lithocap erosion. At Valeriano, in the high Andes of northern Chile, completely concealed Miocene porphyry copper-gold mineralization was recently discovered beneath a lithocap. Here, the results of the staged drilling program that led to the discovery are summarized, with emphasis on the key geologic, alteration, and mineralization features that provided guidance. The final deep drill holes of the 16-hole program cut well-defined advanced argillic and sericitic alteration zones before entering chalcopyrite ± bornite–bearing, potassic-altered porphyry, with grades of 0.7 to 1.2% Cu equiv, at depths of ~1,000 to >1,800 m.
... Giant or large porphyry copper deposit (PCD) may not be solely produced by oceanic subduction [6][7][8], but might also be emplaced in the continental collision during the post-collisional extension of the intra-continental setting, which also favors large or even giant porphyry deposit [9][10][11][12]. Generally, in an arc setting, the porphyry Cu deposits are associated with a calc-alkaline suite whereas in the continental settings are associated with high-K to shoshonitic suites [13,14]. The Gangdese metallogenic belt is an important porphyry copper belt in the Tethyan metallogenic domain that host some famous largesize Cu (Au ± Mo) deposits, e.g., Qulong, Jiama, and Xiongcun, which were discovered over a decade [15][16][17]. ...
Demingding is a promising porphyry Mo-dominated deposit recently discovered in the eastern Gangdese metallogenic belt in Tibet, China. We present zircon U-Pb-Lu-Hf isotopic studies, as well as geochemical data of the late monzogranites and the prior rhyolites from the Demingding porphyry deposit to uncover their origin and geodynamic mechanism. Zircon U–Pb dating yielded precise crystallization ages of 17.3 ± 0.6 Ma (MSWD = 2.5) and 186.5 ± 3.0 Ma (MSWD = 2.0) for monzogranite and rhyolite, respectively. The monzogranite is characterized by high-K calc-alkaline, adakitic affinities, and positive zircon εHf(t) values (+0.9∼+5.6, avg.+3.1) with TDM2 (0.73–1.04 Ga), while the rhyolite has εHf(t) values of (+2.1∼+7.3, avg.+5.2) and TDM2 of (0.76–1.09 Ga) similar to the monzogranite. Our results suggest that the Demingding porphyry Mo (Cu) deposit is related to magma generated from the Neo-Tethyan oceanic subduction. The subsequent monzogranite porphyry was likely formed by the remelting of previously subduction-modified arc lithosphere, triggered by continental collision crustal thickening in Miocene. The lower positive εHf(t) values of monzogranites suggest minor inputs from the Mo-rich ancient crust, suggesting that Mo favors the silicate melt. Such magmatic events and special metallogenesis typify intracontinental processes and porphyry copper deposits, which are normally confined to oceanic subduction and Cu-dominated style, thereby making the continental setting and Mo-dominated style of Demingding exceptional and possibly unique.
... Oligocene (Tosdal & Richards, 2001;Sillitoe & Perelló, 2005;Richards, 2003Richards, , 2013 O R I G Cooke et al., 2005;Rosenbaum et al., 2005;Wilkinson, 2013). Many studies suggest that the porphyry Cu deposits in the South American Andes are commonly associated with topographic anomalies on subducted oceanic crust, such as oceanic plateaus, oceanic ridges, and island chains Rosenbaum et al., 2005;Sun et al., 2010). ...
The Rio Blanco deposit, which is one of the largest porphyry Cu-Mo deposits in northern Peru, formed coevally with the subduction of the Inca Oceanic Plateau at 12–10 Ma. However, the genetic relationship between the subduction of oceanic plateaus and the porphyry deposit formation remains unclear. Igneous rocks emplaced at 23–12 Ma in northern Peru, including the Portachuela batholith (which hosts the Rio Blanco porphyry complex), are normal calc-alkaline to weakly adakitic. In comparison, the 12–8 Ma igneous rocks, including the ore-related Rio Blanco porphyry complex, have typical adakitic signatures, such as high Sr/Y ratios (up to 180) and LaN/YbN ratios (up to 32). The Rio Blanco igneous rocks (Portachuela batholith and Rio Blanco porphyry complex) have uniform zircon εHf(t) values (+0.3 ± 1.2) and δ18O values (6.5 ± 0.14‰). These geochemical characteristics indicate that the Rio Blanco igneous rocks evolved from mantle-derived parental melts in a long-lived, stable, homogeneous isotopic reservoir at the crust–mantle boundary. However, whereas both the Portachuela batholith and the Rio Blanco porphyry complex formed from hydrous parental magmas (>5 wt %; based on plagioclase hygrometry), the ones of the Rio Blanco porphyry complex seem to be more oxidized compared with the older batholitic rocks.
Reverse zoning in plagioclase phenocrysts, with a systematic core–mantle–rim variation in An (anorthite) and Fe (total iron) contents, are common in the intermineralization rocks. The An content of the mantles of the plagioclase phenocrysts correlates positively with the Fe content, but in the rims, the An contents significantly decrease while Fe remains constant. The apatite inclusions in the mantles are richer in S (0.24 ± 0.06 wt %) and Cl (1.42 ± 0.32 wt %) than those in the phenocryst cores (S: 0.09 ± 0.07 wt % and Cl: 1.03 ± 0.56 wt %) and rims (S: 0.14 ± 0.09 wt % and Cl: 0.83 ± 0. 35 wt %). These systemic geochemical variations in the plagioclase phenocrysts suggest recharge by S- and Cl-rich melts followed by fluid exsolution. This magma recharge and subsequent fluid exsolution may have triggered porphyry Cu mineralization at Rio Blanco.
The coincidence of timing between the geochemical transition and collision (initial subduction) of the Inca Oceanic Plateau with the South American plate may indicate a change in the tectonic regime to a compressional state of stress and a thickening of the crust during the collision. The tectonic transition would have facilitated the fractionation of mantle-derived magma in a deep crustal hot zone, resulting in oxidized, volatile-rich residual melts. Replenishment of the upper-crustal magma chamber by such volatile-rich magmas and the subsequent discharge of fluids are interpreted to be fundamental for porphyry Cu mineralization at Rio Blanco and plausibly for the formation of Late Miocene porphyry ore deposits in northern Peru in general.
Zircon is a common mineral in igneous rocks, which is resistant to both chemical weathering and physical abrasion. Its chemistry can potentially be used to distinguish ore-forming porphyry magmas from barren magma systems. This study compiles >23,000 zircon analyses from >30 porphyry deposits, barren intrusions, and rivers to determine the principal geochemical characteristics of fertile zircons using predictive modeling, and compares them with traditional geochemical thresholds. The results show that the Eu/Eu* and Dy/Yb ratios, P content, and the curvature at the end of rare earth element (REE) patterns (λ3) are the most diagnostic characteristics of fertile zircons. The use of geochemical thresholds, as Boolean conditions, reach their maximum performance for Eu/Eu* and Dy/Yb (sensitivity [sens] = 0.73, specificity [spec] = 0.90), but it is outperformed by the random forest model (sens = 0.91, spec = 0.93) in the testing set. Explanatory analysis of the models shows that the fertility signal in zircons becomes stronger as the porphyry system evolves and is accompanied by an overall decrease in the middle to light REE and P content, characteristics that are absent in barren zircons. We attribute the observed difference in λ3 to the co-crystallization of other accessory phases, suggesting that the changes in the zircon Ce anomaly is controlled by the depletion of light and middle REE. The low P content in fertile zircons is caused by extensive crystallization of apatite. Fertile zircons have an excess of (REE + Y)3+, which we attribute to charge-balance by H+ in hydrous magmas. Simple machine learning algorithms outperform the traditional geochemical discriminators in their predictions and provide insights into characteristics that have not previously been considered for evaluating porphyry copper fertility using zircon geochemistry. We propose simplified methods that can be easily incorporated into exploration workflows.
Porphyry-related mineral deposits are giant geochemical anomalies in the Earth’s crust with orders-of-magnitude differences in the content and proportion of the three main ore metals Cu, Au, and Mo. Deposit formation a few kilometers below surface is the product of a chain of geologic processes operating at different scales in space and time. This paper explores each process in this chain with regard to optimizing the chances of forming these rare anomalies.
On the lithosphere scale, deposits with distinct metal ratios occur in provinces that formed during brief times of change in plate motions. Similar metal ratios of several deposits in such provinces compared with global rock reservoirs suggest preceding enrichment of Au or Mo in lithospheric regions giving rise to distinct ore provinces. The largest Cu-dominated deposits and provinces are traditionally explained by selective removal of Au during generation or subsequent evolution of mantle magmas, but the possibility of selective Cu pre-enrichment of lithosphere regions by long-term subduction cannot be dismissed, even though its mechanism remains speculative.
Evolution of hydrous basaltic melts to fertile magmas forming porphyry Cu deposits requires fractionation toward more H2O-rich magmas in the lower crust, as shown by their adakite-like trace element composition. The prevailing interpretation that this fractionation leads to significant loss of chalcophile ore metals by saturation and removal of magmatic sulfide might be inverted to a metal enrichment step, if the saturating sulfides are physically entrained with the melt fraction of rapidly ascending magmas.
Ascent of fertile magma delivers a large mass of H2O-rich ore fluid to the upper crust, along points of weakness in an overall compressive stress regime, within a limited duration as required by mass and heat balance constraints. Two mechanisms of rapid magma ascent are in debate: (1) wholesale emplacement of highly fractionated and volatile-rich granitic melt into a massive transcrustal channelway, from which fluids are exsolved by decompression starting in the lower crust, or (2) partly fractionated magmas filling a large upper crustal magma chamber, from which fluids are expelled by cooling and crystallization.
Transfer of ore-forming components to a hydrothermal ore fluid is optimized if the first saturating fluid is dense and Cl rich. This can be achieved by fluid saturation at high pressure, or after a moderately H2O rich intermediate-composition melt further crystallizes in an upper crustal reservoir before reaching fluid saturation. In either case, metals and S (needed for later hydrothermal sulfide precipitation) are transferred to the fluid together, no matter whether ore components are extracted from the silicate melt or liberated to the ore fluid by decomposition of magmatic sulfides.
Production and physical focusing of fluids in a crystallizing upper crustal magma chamber are controlled by the rate of heat loss to surrounding rocks. Fluid focusing, requiring large-scale lateral flow, spontaneously occurs in mushy magma because high water content and intermediate melt/crystal ratio support a network of interconnected tubes at the scale of mineral grains. Calculated cooling times of such fluid-producing magma reservoirs agree with the duration of hydrothermal ore formation measured by high-precision zircon geochronology, and both relate to the size of ore deposits.
Ore mineral precipitation requires controlled flow of S- and metal-rich fluids through a vein network, as shown by fluid inclusion studies. The degree of hydrothermal metal enrichment is optimized by the balance between fluid advection and the efficiency of cooling of the magmatic fluid plume by heat loss to convecting meteoric water. The depth of fluid production below surface controls the pressure-temperature (P-T) evolution along the upflow path of magmatic fluids. Different evolution paths controlling density, salinity, and phase state of fluids contribute to selective metal precipitation: porphyry Au deposits can form at shallow subvolcanic levels from extremely saline brine or salt melt; high-grade Au-Cu coprecipitation from coexisting and possibly rehomogenizing brine and vapor is most efficient at a depth of a few kilometers; whereas fluids cooling at greater depth tend to precipitate Cu ± Mo but transport Au selectively to shallower epithermal levels.
Exhumation and secondary oxidation and enrichment by groundwater finally determine the economics of a deposit, as well as the global potential of undiscovered metal resources available for future mining.
Libro Guía para Transecta "Cruce de Cordillera Santiago-Mendoza", realizada en el Contexto del XVI Congreso Geológico Chileno XVICGCh-2023
Geology, magmatic evolution and mineralization history, Los Pelambres porphyry popper, central Chile
Porphyry deposits in magmatic arcs form coincident with changes to steady-state oceanic subduction conditions, such as changes in plate convergence rate and vector or angle of subduction. However, it remains unclear whether such processes also operated during formation of postsubduction porphyry deposits. The Yulong magmatic belt in the eastern Tibetan Plateau consists of middle to late Eocene igneous rocks (~51–35 Ma) that formed during the India-Asia collision, whereas all known porphyry deposits are associated with late Eocene rocks (43–35 Ma). A synthesis of new and published geochemical data shows marked variations from the middle to late Eocene, including increasing whole-rock La/Yb, Sr/Y, and EuN/EuN* values, as well as zircon EuN/EuN* values. These geochemical variations, together with petrographic observations, indicate a transition from plagioclase-dominated to amphibole-dominated fractionation from the middle to late Eocene.
Coupled changes of magma compositions and porphyry Cu metallogeny from the middle to late Eocene coincided with, or were slightly preceded by, the onset of regional uplift and crustal thickening, triggered by the India-Asia hard collision and rapid deceleration of the India-Asia convergence rate at ca. 50 to 44 Ma. Crustal thickening may have caused prolonged magma differentiation at greater depths and accumulation of dissolved H2O, both of which contributed to amphibole-dominated fractionation and generation of hydrous melt that are prospective for porphyry Cu mineralization. Our study highlights the importance of tectonic changes in the formation of the Yulong and other postsubduction porphyry Cu belts—a scenario similar to that operated in subduction-related settings such as the Andes.
Global political and economic developments shape both the demand for minerals and primary metals and their supply. Overall, demand has moved broadly in step with economic activity over the past 30 years. Notwithstanding the collapse of the Soviet Union and Eastern Bloc countries, demand grew more rapidly in the second half of the period than the first. The performance of individual products within this general trend largely reflects the specific nature of their main end uses. The geographic center of demand has shifted away from the mature industrial economies of North America, Western Europe, and Japan toward the newly industrializing countries of the Pacific Rim, China, and India. Mine production rose with demand, but not always in precise step. New capacity was required not just to meet demand, even where that was static, but also to offset the continuing effects of ore depletion. There were also changes in the location of production in response to geopolitical forces, the depletion of ore reserves, and the changing economics of extraction and processing. The number of mines contracted, especially during the 1990s, and the scale of mining operations was increased in order to achieve the requisite cost savings. Prices fluctuated in response to changing balances between supply and demand, trending downward from the early 1970s until the early 2000s. Most products witnessed at least one sharp price spike during the period, usually with continuing repercussions. Prices picked up from 2003, but generally not back to their earlier peak in real terms. Profitability varied according to the products concerned. In many years the average rates of return on capital employed have been insufficient to cover the risks involved.
The porphyry copper deposit of Dahane-ye Gomrokan is located 70 km east of Jiroft. The deposit is situated in the southeastern part of the Kerman belt (Jebal Barez) of the Urumieh-Dokhtar magmatic arc. The main outcrops in the studied area are composed of Eocene volcanic rocks and plutonic phases including granodiorite, quartz monzonite-quartz monzodiorite, and tonalite. In this area, two fault systems aligned with the general structures of
the Jebal Barez zone have functioned. These two fault systems include a) NW-SE trending faults and b) NE-SW trending faults. The NW-SE faults have controlled the placement of quartz monzonite-quartz monzodiorite masses, and tonalites; therefore, these plutonic phases are aligned with the faults of this outcrop. On the other hand, the mineralized quartz stockworks formed in the granodiorite phase extend in the same direction and parallel to the general NW-SE trend. The performance of both mentioned fracture systems in the Gomrokan area has played a role in the placement of plutonic phases, in the development and expansion of hydrothermal alteration zones (potassic, phyllic, argillic, and propylitic), and also in the control of copper mineralization.
The Río Blanco-Los Bronces deposit is the largest Cu-Mo porphyry deposit in the world in terms of contained Cu metal. It is the product of protracted superposed magmatic and hydrothermal activity associated with multiple intrusive and brecciation events, with simultaneous regional uplift, erosion and unroofing, and decompression. Magmatism resulted in three major mineralization-alteration stages. The premineralization stage occurred during the emplacement of the San Francisco batholith, resulting in late magmatic and early hydrothermal events. The synmineralization stage corresponds to the main hydrothermal events associated with the Río Blanco-Los Bronces porphyry and breccia complexes, which were related to three intrusion phases, widespread brecciation, and an epithermal-style advanced argillic alteration. Late-stage magmatism, followed by hydrothermal activity, was associated with the emplacement of subvolcanic rhyolite complexes and late-stage porphyry intrusions. The synmineralization intrusions are associated with high-grade breccia bodies that have well-defined alteration-zonation patterns.
Compilation and analysis of the historical Río Blanco structural data sets from the different mines, tunnels, and pits have allowed the assignment of all mapped structures to four hierarchical orders based on their continuity, crosscutting relationships, and infill compositions. The larger structures (orders 0 and 1) have along-strike continuity, correlate between drifts and/or mine levels, whereas smaller structures (orders 2 and 3) were grouped according to their dimensions and distributions within the larger-order structure-defined panels. All orders 0 and 1 structures were modeled in three dimensions, while orders 2 and 3 were in two dimensions. The structures mapped at Río Blanco have an intimate relationship with the pre- to the late-stage geologic evolution of magmatism and mineralization. The regional- and to a lesser extent district-scale structural evolution was related to premineralization basin-opening and subsequent tectonic inversion, whereas at the camp scale, syn- to late mineralization intrusions and related hydrothermal features were superimposed on this inherited structural architecture.
Porphyry Cu deposits in China contain a total resource of ~47 million tonnes (Mt) Cu at average grades ranging mostly from 0.2 to 0.7% Cu (most <0.5% Cu), accounting for 42% of China’s Cu reserves. In terms of contained Cu, 14 Cu-rich porphyry deposits are classified as giant (≥2.0 Mt Cu), and 38 are classified as intermediate (≥0.06 Mt Cu). These giant and intermediate deposits are mainly concentrated in seven belts or districts: Gangdese belt, southern Tibet; Yulong and Zhongdian belts, eastern Tibet; Duolong district, central Tibet; Dexing district and Middle-Lower Yangtze River Valley belt, eastern China; and the Central Asian orogenic belt in northern China. Other isolated giant deposits (e.g., Tongkuangyu) occur in the North China craton. These deposits were formed during Paleoproterozoic (~2100 Ma), Ordovician (~480–440 Ma), Carboniferous (~330–310 Ma), Late Triassic to Early Cretaceous (~215–105 Ma), and Eocene to Miocene (~40–14 Ma), with the majority forming during the latter two time periods. Adakite-like (e.g., high Sr/Y ratio) magmas are most favorable for the formation of the porphyry Cu deposits in China, although some deposits in the Central Asian orogenic belt and the Duolong district are associated with normal calc-alkaline intrusions with low Sr/Y ratios.
Approximately 50% of the giant and ~35% of the intermediate porphyry Cu deposits in China formed in arc settings. The Xiongcun, Pulang, Duobuza, Bolong, and Naruo deposits in Tibet formed in continental arc settings, and the Central Asian porphyry Cu belt deposits (e.g., Tuwu-Yandong, Duobaoshan, Wushan, Baogutu, and Bainaimiao) formed in island-arc settings. Ore-forming porphyry magmas in arc settings in China probably formed by partial melting of metasomatized mantle wedge. Ascent and emplacement of porphyry magmas in arc settings was controlled by transpressional (e.g., strike-slip fault systems) or compressional deformation (e.g., arc-parallel thrust fault systems). Approximately 40% of the giant and ~65% of the intermediate porphyry Cu deposits in China occur in postcollisional settings. These deposits are mainly concentrated in the Tibetan Plateau, including four giant (e.g., Qulong, Jiama, Zhunuo, and Yulong) and more than 15 intermediate-size deposits. The mineralized intrusions in postcollisional settings were generated by partial melting of subduction-modified mafic lower crust. Ore-forming metals and sulfur were derived from remelting of sulfide phases that were introduced during precollisional arc magmatism, and the water in the Cu-forming porphyry magmas was concentrated during dehydration reactions in the upper parts of the subducting continental plate and/or degassing of mantle-derived H2O-rich ultrapotassic and/or alkaline mafic magmas. Porphyry magma ascent and emplacement were controlled by regional shear zones (e.g., strike-slip fault systems) or extensional fracture arrays (e.g., normal fault systems) in postcollisional settings.
Porphyry Cu deposits in China mostly show typical alteration zoning from inner potassic to outer propylitic zones, with variable phyllic and argillic overprints. Potassic alteration can be generally subdivided into inner K-feldspar and outer biotite zones, with K-feldspar–rich alteration mostly earlier than biotite-rich alteration. Phyllic alteration generally comprises early-stage chlorite-sericite and late-stage quartz-sericite alteration, and the chlorite-sericite zone typically occurs beneath the quartz-sericite zone. Lithocaps are absent in most of the porphyry Cu deposits in China, even for those in the youngest (~30–14 Ma) ores in the Gangdese belt. Alteration architecture of the porphyry Cu deposits in China is mainly dependent on the structural setting and degree of telescoping. Telescoping of alteration assemblages in the postcollisional porphyry Cu deposits is more strongly developed than that in island and continental arc porphyry Cu deposits. This is probably because postcollisional porphyry Cu deposits and districts in China either experienced higher rates of synmineralization uplift or suffered more complex structural superposition, compared with those formed in magmatic arcs. Hypogene Cu mineralization in some giant porphyry deposits in China (e.g., Xiongcun, Qulong) is associated with potassic alteration and particularly with late-stage biotite alteration. But hypogene mineralization for more than 50% of giant porphyry Cu deposits, including the Dexing, Yulong, Tuwu-Yandong, Duobaoshan, and Tongkuangyu deposits, is characterized by a Cu sulfide assemblage with phyllic alteration, particularly with chlorite-sericite alteration. The presence of several world-class postcollisional porphyry Cu provinces in China demonstrates that the generation of porphyry Cu deposits does not always require a direct link to oceanic plate subduction.
El Distrito Minero Casale se encuentra ubicado en la porción sur de la Franja de Maricunga, el cual corresponde a un cluster de pórfidos con edades entre los y . Este incluye los depósitos porfídicos Cerro Casale y el sub-cluster Luciano, conformado por los depósitos Luciano ( ), Luciano Norte y Úrsula, entre otros.
La litología del cluster de pórfidos Luciano se compone de Unidades Preminerales conformadas de Tobas daci-andesíticas, Conglomerados y los Complejos andesítico Juanes y Autobrechizado (intrusivo diorítico y brecha intrusiva, respectivamente). Los procesos de alteración y mineralización se encuentran relacionados a intrusiones multifásicas porfídicas dioríticas agrupadas en las unidades Pórfido Diorítico I, II y III, ubicadas en posiciones intermineral temprano, intermineral y tardío mineral dentro de la evolución magmática-hidrotermal. Cuerpos de Brechas Intrusivas, Intrusivas alteradas, Magmáticas-hidrotermales y Freatomagmáticas se consideran eventos subordinados de mineralización y representan un volumen menor al de los depósitos en estudio.
Las zonas de mineralización de oro mayores a se asocian principalmente a Unidades Porfídicas (Pórfido Diorítico I y II) en el sector de Luciano y Luciano Norte. Mientras que para el sector de Úrsula el evento principal de mineralización corresponde a un cuerpo de Brecha Intrusiva alterada con mineralización de oro mayor asociada a fragmentos de pórfido mineralizado con vetillas truncadas de cuarzo.
Se ha determinado una zonación vertical de la alteración hidrotermal, mineralización sulfurada y asociación mineralógica del oro, relacionada a alteración potásica y propilítica I. Una zona profunda potásica, con un predominio de vetillas de cuarzo A y B, mineralización sulfurada hipógena de cobre, galena y menor esfalerita (Sector Luciano); a una zona superior propilítica I, con predominio de vetillas de cuarzo transicionales bandeadas, escasas de cuarzo bandeadas, mineralización sulfurada de esfalerita, pirita, galena y escasos sulfuros de cobre (Sector Luciano Norte y Úrsula).
La alteración potásica y propilítica I gradarían de manera lateral y distal hacia una propilítica II, y son sobreimpuestas en la parte profunda por una sódico-férrica (Sector Luciano y Luciano Norte). En superficie se sobreimpone una alteración argílica y silicificación (Luciano Norte y Úrsula).
El oro de carácter principalmente nativo ) presenta dos asociaciones mineralógicas principales: (bornita, calcopirita) y (esfalerita y galena). Las asociaciones y se relacionan a alteración potásica y se relaciona a alteración propilítica I.
Las características de alteración, estilos de vetillas y mineralización descritas anteriormente indicarían que los depósitos porfídicos en estudio presentarían distintos niveles de erosión o exhumación, donde Luciano es el depósito más erodado o exhumado, seguido de Luciano y finalmente Úrsula.
El Distrito Minero Casale se encuentra ubicado en la porción sur de la Franja de Maricunga, el cual corresponde a un cluster de pórfidos con edades entre los y . Este incluye los depósitos porfídicos Cerro Casale y el sub-cluster Luciano, conformado por los depósitos Luciano ( ), Luciano Norte y Úrsula, entre otros.
La litología del cluster de pórfidos Luciano se compone de Unidades Preminerales conformadas de Tobas daci-andesíticas, Conglomerados y los Complejos andesítico Juanes y Autobrechizado (intrusivo diorítico y brecha intrusiva, respectivamente). Los procesos de alteración y mineralización se encuentran relacionados a intrusiones multifásicas porfídicas dioríticas agrupadas en las unidades Pórfido Diorítico I, II y III, ubicadas en posiciones intermineral temprano, intermineral y tardío mineral dentro de la evolución magmática-hidrotermal. Cuerpos de Brechas Intrusivas, Intrusivas alteradas, Magmáticas-hidrotermales y Freatomagmáticas se consideran eventos subordinados de mineralización y representan un volumen menor al de los depósitos en estudio.
Las zonas de mineralización de oro mayores a se asocian principalmente a Unidades Porfídicas (Pórfido Diorítico I y II) en el sector de Luciano y Luciano Norte. Mientras que para el sector de Úrsula el evento principal de mineralización corresponde a un cuerpo de Brecha Intrusiva alterada con mineralización de oro mayor asociada a fragmentos de pórfido mineralizado con vetillas truncadas de cuarzo.
Se ha determinado una zonación vertical de la alteración hidrotermal, mineralización sulfurada y asociación mineralógica del oro, relacionada a alteración potásica y propilítica I. Una zona profunda potásica, con un predominio de vetillas de cuarzo A y B, mineralización sulfurada hipógena de cobre, galena y menor esfalerita (Sector Luciano); a una zona superior propilítica I, con predominio de vetillas de cuarzo transicionales bandeadas, escasas de cuarzo bandeadas, mineralización sulfurada de esfalerita, pirita, galena y escasos sulfuros de cobre (Sector Luciano Norte y Úrsula).
La alteración potásica y propilítica I gradarían de manera lateral y distal hacia una propilítica II, y son sobreimpuestas en la parte profunda por una sódico-férrica (Sector Luciano y Luciano Norte). En superficie se sobreimpone una alteración argílica y silicificación (Luciano Norte y Úrsula).
El oro de carácter principalmente nativo ) presenta dos asociaciones mineralógicas principales: (bornita, calcopirita) y (esfalerita y galena). Las asociaciones y se relacionan a alteración potásica y se relaciona a alteración propilítica I.
Las características de alteración, estilos de vetillas y mineralización descritas anteriormente indicarían que los depósitos porfídicos en estudio presentarían distintos niveles de erosión o exhumación, donde Luciano es el depósito más erodado o exhumado, seguido de Luciano y finalmente Úrsula.
Novel resource recovery technologies are required for metals-bearing hazardous wastes in order to achieve circular economy outcomes and industrial symbiosis. Iron oxide and co-occurring hydroxysulphate-bearing wastes are globally abundant and often contain other elements of value. This work addresses the biostimulation of indigenous microbial communities within an iron oxide/ hydroxysulphate-bearing waste and its effect on the subsequent recoverability of metals by hydrochloric, sulphuric, citric acids, and EDTA. Laboratory-scale flow-through column reactors were used to examine the effect of using glycerol (10% w/w) to stimulate the in situ microbial community in an iron oxide/ hydroxysulphate-bearing mine waste. The effects on the evolution of leachate chemistry, changes in microbiological community, and subsequent hydrometallurgical extractability of metals were studied. Results demonstrated increased leachability and selectivity of Pb, Cu, and Zn relative to iron after biostimulation with a total of 0.027 kg of glycerol per kg of waste. Biostimulation, which can be readily applied in situ, potentially opens new routes to metal recovery from globally abundant waste streams that contain jarosite and iron oxides.
Novel resource recovery technologies are required for metals-bearing hazardous wastes in order to achieve circular economy outcomes and industrial symbiosis. Iron oxide and co-occurring hydroxysulphate-bearing wastes are globally abundant and often contain other elements of value. This work addresses the biostimulation of indigenous microbial communities within an iron oxide/ hydroxysulphate-bearing waste and its effect on the subsequent recoverability of metals by hydrochloric, sulphuric, citric acids and EDTA. Laboratory-scale flow-through column reactors were used to examine the effect of using glycerol (10% w/w) to stimulate the in situ microbial community in an iron oxide/ hydroxysulphate-bearing mine waste. The effects on the evolution of leachate chemistry, changes in microbiological community and subsequent hydrometallurgical extractability of metals were studied. Results demonstrated increased leachability and selectivity of Pb, Cu, and Zn relative to iron after biostimulation with a total of 0.027 kg of glycerol per kg of waste. Biostimulation, which can be readily applied in situ , potentially opens new routes to metal recovery from globally abundant waste streams that contain jarosite and iron oxides.
Abri and Rahbari deposits are located 23 km NW Darooneh and are located in the part of the Khaf-Darooneh volcanic-plutonic belt and the Sabzevar Sub- Zone. The studied area rock units consisted of three categories with the age of Middle Eocene include: 1- submarine lava (andesite, basalt, porphyry andesite-basalt, trachy andesite), 2- pyroclastic (tuff and agglomerate) and 3- sedimentary (limestone, limestone marl, Siltstone and shale). The volcanic rocks belong to medium to high K calc-alkaline magmatic series and have been formed during a volcanic arc tectonic regime of active continental margin. Mineralization in Abri and Rahbari areas has occurred, on the border of limestone units with pyroclastic rocks and lava as strata bound and the mineral is formed as veins and vein- veinlet, cavities and open space filling and disseminated. the main minerals formed the deposits are classified in three groups of sulfide minerals (chalcocite, covellitis, bornite, chalcopyrite and pyrite), carbonate minerals (malachite, azurite) and oxide minerals (cuprite, magnetite, hematite and limonite). Based on the micro thermometry studies the average of fluid inclusions homogenization temperature in Abri and Rahbari area is 198 ˚C and The average of salinity is 8.9 wt% NaCl. Based on the geochemical studies copper in the base metals has the highest production coefficient (The equivalent of 4 to 5 weight percent). According to the studies, it can be said that mineralization in the Abri and Rahbari area is epigenetic, strata bound that is similar to the manto type copper deposits.
The Don Javier porphyry Cu–Mo deposit formed contemporaneously with the Incaic I orogeny (∼60 Ma) in southern Peru. The causative dacite porphyry is hosted by the Yarabamba Superunit, which is the youngest batholithic unit in the Toquepala arc. In this study, we conducted elemental and isotopic analyses on samples from the dacite porphyry and Yarabamba Superunit in an effort to clarify the origins and formation mechanism of the deposit. Zircon U–Pb dating shows that the young part of the Yarabamba Superunit was emplaced at 65.4 ± 0.7 to 63.5 ± 0.8 Ma, and the causative dacite porphyry was emplaced at Don Javier between 59.2 ± 1.1 and 59.9 ± 0.4 Ma. The Yarabamba Superunit and dacite porphyry have similar εHf(t) and δ¹⁸O isotope values, ranging from –4.6 to +1.9 and 5.1‰ to 6.4‰, respectively. The Yarabamba Superunit has initial Sr and Nd isotope values of 0.7053–0.7058 and 0.51242–0.51244, respectively. Isotopic data suggest that the Yarabamba Superunit and dacite porphyry evolved from an isotopically homogeneous magma reservoir with minor crustal assimilation. However, the dacite porphyry has whole-rock and zircon Eu/Eu* values of 0.9 and 0.34, respectively, higher than those of the Yarabamba Superunit (0.6 and 0.13).
Additionally, the dacite porphyry has significantly higher apatite S content (0.07) and XCl values (0.21) than those of the Yarabamba Superunit (apatite S: 0.04; XCl values: 0.15). The calculated magmatic oxidation state shows that the dacite porphyry has a significantly higher magmatic oxygen fugacity (ΔFMQ +1.1) than the Yarabamba Superunit (ΔFMQ –0.5).
Together, the data suggest that the magmas that formed the Yarabamba Superunit and causative dacite porphyry are characteristics of distinct tectonic regimes. The magma of the Yarabamba Superunit was generated during normal subduction and underwent low-pressure, H2O-poor, plagioclase-dominated fractionation while the magma of the dacite porphyry was generated during arc compression and underwent high-pressure, H2O-rich, amphibole-(garnet) dominated fractionation, which led to a high oxidation state and volatile-rich magma that promoted porphyry mineralization at Don Javier. This rapid elevation of the magmatic oxidation state and volatile content occurred synchronously with the Incaic I orogeny (∼60 Ma), which indicates that this orogeny had a significant impact on the formation of the very large–giant porphyry ore systems in southern Peru.
В монографии рассмотрена геологическая история Земли от ее зарождения до настоящего времени. Отмечено, что Земля зародилась в составе Солнечной системы спустя ~9.2 млрд лет после образования Вселенной. В истории Земли выделяются: хаотичный, ранний (гадейский и ранне-среднеархейский этапы), переходный и поздний периоды. В хаотичный период (4568–4500 млн лет) произошла аккреция Земли и дифференциация ее на ядро и мантию. В этот же период произошло столкноваение с планетоидом Тейя и формирование Луны. В Гадейский эон (4,5 – 4,0 млрд лет) началась геологическая история Земли, развитие планеты контролировалось постоянными космическими бомбардировками. Об этом времени позволяют судить цирконы, наблюдаемые в ядрах цирконов более молодых пород. Начиная с архея, Земля развивалась в режиме самоорганизации. В раннем и среднем архее (4 – 3.1 млрд лет) динамика развитии Земли определялась процессами тектоники покрышки (LID или вертикальной тектоники) и мантийных переворотов. В этот этап в ее недрах зарождается твердое железное ядро. В переходный период (3,1-2,0 млрд лет) произошли важные изменения в строении каменных оболочек нашей планеты. Определяющим тектоническим режимом стала тектоника малых литосферных плит, благодаря которой резко возросла скорость корообразования, в строении верхней мантии выделилась астеносфера, а в глубинах мантии сформировался слой D”. Поздний период развитии Земли (<2 млрд лет) контролировался процессами глобальной тектоники, включающей тектонику литосферных плит и тектонику мантийных плюмов. Наряду с общей направленностью эволюции геологических процессов рассмотрены вопросы формирования суперконтинентов и суперконтинентальных циклов, проблемы палеотектонических реконструкций, а также металлогенической эволюции в истории Земли.
Помимо геологических аспектов развития Земли рассмотрены также вопросы эволюции биосферы. Отдельные главы посвящены появлению человека и возникновению ноосферы – еще одной геологической сферы Земли.
Книга рассчитана на специалистов, занимающихся проблемами эволюции геологических процессов, а также на молодых ученых, студентов и преподавателей геологических специальностей ВУЗов.
Full text is available from http://repository.geologyscience.ru/handle/123456789/39616
The Early Cretaceous Halasheng Ag-Pb-Zn deposit in NE China, which is mainly hosted in Jurassic rhyolitic tuff, andesite, and volcanoclastic rocks, comprises both proximal skarns and more distal hydrothermal discordant ore veins and stockworks with associated Fe-Mn-carbonate, illite, and silica alteration in NNW-trending extensional faults. Suggestions of a magmatic-hydrothermal relationship are tested by LA-ICP-MS trace-element and sulfur isotope studies of ore minerals, particularly sphalerite which is a major ore mineral.
Sphalerite has at least three types: SpS, anhedral, mainly dark red sphalerite in skarns; Sp1, euhedral, normally pale yellow coarse-grained, and rarely oscillatory zoned sphalerite formed in Stage 2 of hydrothermal vein mineralization; and Sp2, fine-grained, red, non-zoned sphalerite formed in Stage 3 of hydrothermal mineralization. Sphalerite with different textures have As, Ag, Cd, Sb, and Pb contents that increase from proximal skarn to distal hydrothermal mineralization consistent with the increase in sulfosalt minerals in the late hydrothermal stage. In situ time-resolved depth profiles, together with tangential profiles, and LA-ICP-MS element mapping of sphalerite indicate that trace elements are largely in solid solution in Halasheng sphalerite with substitution mechanisms including: Zn²⁺ ↔ Fe²⁺, Cd²⁺, Mn²⁺, and 3Zn²⁺↔ (As³⁺, Sb³⁺) + Ag⁺+Pb²⁺. Enrichment of In and Sn, and depletion of Ga and Ge, together with In/Sn ratios indicate the high-temperature ore-forming fluids at Halasheng that are most likely closely related to intrusions. In situ mean δ³⁴SV-CDT values of SpS, Sp1, and Sp2 sphalerites are 5.3‰, 7.6‰, and 8.3‰, respectively, indicating that sulfur was derived both from magmatic-hydrothermal fluids and from wall rocks with higher (> 10‰) values.
These data help confirm that the Halasheng Ag-Pb-Zn deposit is an intrusion-related deposit with local proximal skarn mineralization at the contact of Tamulangou Formation andesite with Ergunahe Formation crystalline limestone, and more distal vein-type volcanic-hosted hydrothermal mineralization, with both ore and gangue mineral assemblages and available fluid inclusion data suggesting an intermediate-sulfidation epithermal association. As ore-forming hydrothermal fluids cooled and evolved they became enriched in silver, with silver-bearing sulfosalt minerals and silver-rich sphalerite precipitated in the latter stages of deposition.
In terms of future exploration, there is potential for the concealed Lower Cretaceous Pb-Zn skarns and intermediate sulfidation Ag-Pb-Zn epithermal deposits at Halasheng to be part of a larger porphyry-related mineral system with porphyry Cu-Au-Mo deposits, similar to those of Middle Triassic to Early Jurassic age in the same metallogenic belt, at deeper crustal levels than the known deposits.
Hypogene mineralization in porphyry Cu deposits is typically associated with crustal thickening and rapid exhumation, whereas supergene enrichment requires slow exhumation to allow sufficient time for leaching and downward transport of Cu before it is lost to surface erosion. Therefore, spatial and temporal patterns of exhumation within a metallogenic belt can highlight favorable locations for hypogene mineralization, supergene enrichment, and preservation. Here, we determine average pluton exhumation rates along an ~730-km segment of the middle Eocene-early Oligocene metallogenic belt in northern Chile (17.8°–24.2°S). By combining zircon U-Pb geochronology with Al-in-hornblende geobarometry, we pinpoint the time and depth at which each pluton was emplaced and use the age of overlying cover units or supergene minerals to date its arrival at the surface (or near-surface) environment.
Uranium-Pb zircon ages for 49 samples from plutons and porphyries range from Carboniferous to Eocene (~314–35 Ma). Al-in-hornblende emplacement depths for 19 plutons are ~4–7 km, with one Carboniferous pluton emplaced at ~12 km. Two phases of net exhumation are identified: early Permian-Middle Triassic and middle Eocene-late Oligocene, with an intervening period of net burial. The highest exhumation rates (>0.30 km/m.y.) derive from the second phase, coeval with the Incaic orogeny and the main phase of hypogene mineralization. Present-day preservation of plutons and porphyry Cu deposits required low post-Oligocene average exhumation rates of <~0.01 km/m.y.—favorable for the development of many world-class supergene blankets. However, spatial variability in exhumation and burial across the belt led to poor conditions for supergene development locally: enrichment was hampered in some places by rapid exhumation after hypogene mineralization (e.g., ≥~4 km at El Abra), by burial beneath significant cover (e.g., Ministro Hales, Queen Elizabeth), or, in the Inti region of northernmost Chile, by a combination of the two.
The Don Javier porphyry Cu-Mo deposit is located in the Yarabamba district of the Arequipa region, Peru, which represents the northwestern end of the Paleocene-early Eocene Cu belt of the central Andes, extending from northern Chile into southwestern Peru. The deposit occurs around the contacts of a dacite porphyry stock emplaced into the pre-mineralization and Yarabamba granodiorite batholith. The intrusions display a telescoped sequence of alteration, from shallow sericitic to deeper chloritic-sericitic, with minor remnant potassic assemblages, which are surrounded by propylitic zones. EB-, M-, EQ-, SQ-, and D-type veinlets occur in all alteration zones. The higher Cu and Mo grades are mainly associated with the widely distributed sulfide-quartz veinlets within the potassic and chlorite-sericite overlapping zones. The mineralized zone measures ∼500 m in width (NE-SW) by ∼ 800 m in length (NW-SE). Uranium-Pb zircon ages show that the Yarabamba granodiorite plutons were emplaced at ∼64.6 Ma and subsequently intruded by the inter-mineralization dacite porphyry intrusions at ∼59.9 to 59.5 Ma. Molybdenite Re-Os ages indicate that the deposit formed between ∼60.5 and 59.6 Ma. Younger molybdenite Re-Os ages (∼45.4 to 44.4 Ma) obtained in the deep parts of the altered rocks suggest that the deposit might have been overprinted by later hydrothermal activity in the Eocene. The success of exploration at Don Javier emphasizes that traditional methods such as geologic and geophysical mapping followed by timely drilling tests can still be effective in a mature metallogenic belt.
Como resultado del programa de reconocimiento geoquímico de la cordillera Occidental, iniciado por el Ingeominas en el año de 1970, se localizaron varias áreas de interés por sus contenidos anómalos de cobre y elementos asociados.
Posteriormente se acordó adelantar trabajos en detalle sobre estas áreas, iniciándolos en la región de Pantanos-Pegadorcito. Este tipo de trabajos comprendió el muestreo geoquímico sobre un área de aproximadamente 140 km2 en la cual se colectaron y analizaron 981 muestras de roca, 1199 muestras de suelo, 1502 muestras de sedimentos
finos y 934 muestras de concentrados de batea. Además, se efectuó la cartografía geológica a escala 1: 10 000 de 13 km2 y se perforaron 556 metros distribuidos en 9 pozos.
Las relaciones geológicas conocidas en la parte norte de la cordillera Occidental indican que una secuencia sedimentaria-volcánica de edad cretácica ha sido intruida por el Batolito de Mandé, de composición cuarzodiorita-diorita, y plutones menores considerados de edad terciaria media.
En el área Pantanos-Pegadorcito, la cuarzodiorita, que tentativamente se ha considerado como parte del Batolito de Mandé, ha sido cortada a su vez por cuerpos de pórfidos cuarzodioríticos que fueron agrupados en tres tipos, con pequeñas diferencias entre sí. Además de estas rocas, se cartografiaron parcialmente varios cuerpos de brecha intrusiva.
Alteración sericítica y en menor proporción la argílica y silicificación se observan preferencialmente en los pórfidos; la cuarzodiorita muestra generalmente alteración proptlica. La alteración potásica solo se observó muy localmente y pobremente desarrollada.
Pirita, calcopirita y bomita en forma diseminada y en venillas se presentan preferencialmente en el pórfido tipo A y en la cuarzodiorita cerca al contacto con los pórfidos; de las rocas cartografiadas, la brecha intrusiva es la menos mineralizada.
La prospección geoquímica detallada permitió la delimitación de dos zonas anómalas para cobre y molibdeno. La zona más extensa tiene una longitud aproximada de 5,0 km y ancho promedio de 500 m y está relacionada con el Cerro Pantanos; la segunda zona está localizada 1,5 km al noroeste de la primera y tiene una longitud de 1 km y ancho promedio de 500 m.
Las perforaciones efectuadas indicaron la presencia de mineralización de cobre en las zonas anómalas detectadas por geoquímica y la ausencia de valores significativos de cobre en los pozos perforados lejos de dichas zonas.
Por las observaciones litológicas, estructurales, de mineralización, alteración y por las anomalías geoquímicas reconocidas en Pantanos-Pegadorcito, se puede concluir que el área presenta características muy favorables para el desarrollo de un depósito de pórfido cuprífero cuyo verdadero potencial económico queda aún por determinar.
Significant metallic mineralization throughout the Mesozoic-Cenozoic Andean Province of northern Chile and northwestern Argentina has consistently been related to the emplacement of granitic plutons or to andesitic-to-rhyolitic volcanism. Between latitudes 26° and 29°S epigenetic, hydrothermal deposits of copper and other metals formed immediately following the intrusion of felsic stocks of Upper Jurassic (140-155 m .y.), Middle Cretaceous (90-120 m.y .), Lower Paleocene (60-67 m.y.), Upper Eocene (39-44 m.y.), Oligocene-Miocene (22-23 my) and Miocene-Pliocene (5-12 m.y.) age. The Cenozoic intrusions, associated with essentially contemporaneous volcanics, exhibit local prophyritic facies, and mineralization was concentrated close to the intrusive-extrusive interface. Ore deposits of the porphyry copper clan occur in all post-Mesozoic intrusive provinces, but major centres have so far been recognized only in Upper Eocene and Miocene-Pliocene stocks. Disseminated copper and copper-silver deposits, stratabound but not strictly syngenetic, have developed in marine and continental andesites of Middle Jurassic to Cretaceous age, and in co ntinental Tertiary rhyolites. Large bodies of magnetite, of apparent contact metasomatic origin, are, with few exceptions, restricted to sequences of andesite intruded by Middle Creta-ceous plutons. , From the initiation of the Andean orogen, in Triassic-Jurassic times, to the mid-Tertiary, the locus of epizonal magmatism and associated mineralization has migrated east-southeastward at a gradaully increasing rate (from ca. 0.06 to 0.10 cmJyr), to form a series of discrete longitudinal metallogenetic sub-provinces, each of which eyolved within a specific metallogenetic phase. This systematic progression was abruptly terminated in the Oligocene, and, by the Mio-cene, calc-alkaline volcanism was taking place simultaneously in several areas across a 250-km-wide belt to the east of the Eocene sub-province. Subsequently from the Pilocene to the Recent, volcanism has been focused at an intermediate position to form the strato-volcanoes of the High Andes. Porphyry copper mineralization associated with this magmatic activity in Argentina has possibly shown a parallel westward recession since the Miocene. The emplacement of high-level igneous rocks and hydrothermal ore deposits in this region is co nsidered to have resulted from the generation of magmas through subduction of oceanic lithosphere beneath continental South America. The structural framework of a Benioff zone may have been imposed in the Jurassic, but the present general configuration of the continental margin probably derives from a major reorientation of plate motions in the Miocene. The pre-Mesozoic basement, in general sparsely mineralized, appears to have contributed li ttle to the development of the igneous rocks and mineralization of the overprinted Andean mo bile belt at this latitude. The recurrent copper specialization of this metallogenetic province reflects a consistency in the source materials and processes of sub-crustal magma generation. 261
Antamina, the world’s largest copper-zinc skarn deposit, entered production in 2001. This paper describes
the development of the geologic model for the feasibility study (1996–1998). Antamina is located in the eastern
part of the Western Cordillera of northern Peru at latitude 9º 32' S and longitude 77º 03' W and 4,200 to
4,800 m in elevation.
Antamina has a long history of exploration and is a case study of successful creation of an orebody from a
mineral resource. While small-scale mining is recorded intermittently since 1860, the first serious exploration
was not begun until a century later by Cerro de Pasco Corporation (1952–1970), followed by a Minero Peru-
Geomin (Romania) partnership, which conducted a feasibility study (1970–1976) with a reserve of 128.6 million
metric tons (Mt) at 1.6 percent Cu and 1.3 percent Zn.
Privatization of the project was won by Compañía Minera Antamina in 1996. This consortium undertook a
major exploration program and completed a full feasibility study in 1998 that defined a minable, open-pittable
resource of 500 Mt at 1.2 percent Cu, 1.0 percent Zn, 0.03 percent Mo, and 12 g/t Ag within a global resource
of 1,500 Mt. Production is by open pit and flotation at 70,000 t/d, producing 270,000 t of copper and 162,000
t of zinc in concentrates per year. This makes Antamina the seventh largest copper and the third largest zinc
mine in the world.
Antamina is located in the polymetallic belt of central Peru, which comprises copper, zinc, silver, lead and
gold deposits related to mid to late Miocene calc-alkaline stocks. The regional geologic setting comprises Late
Jurassic to Late Cretaceous siliciclastic to carbonate sequences in a northwest-trending foreland fold-thrust
belt of mid-Eocene age, the Incaic II deformation phase. Antamina is hosted by calcareous siltstone and mudstone of the Late Cretaceous Upper Celendin Formation. Skarn mineralization forms a shell over and around a quartz monzonite porphyry stock of late Miocene age, which itself hosts subeconomic porphyry copper-molybdenum mineralization. The skarn body is approximately 2,500 m long in a northeasterly direction and up to 1,000 m wide, with a known vertical extent of 1,000 m. The skarn consists mainly of andraditic garnet. It is symmetrically zoned around the intrusion from proximal brown garnet endoskarn and exoskarn outward to green garnet exoskarn, with peripheral wollastonite-diopside exoskarn. Significant copper mineralization is hosted by endoskarn. Retrograde chlorite skarn and hydrothermal breccia are minor.
Metals are zoned laterally from a central copper-only zone to a peripheral copper-zinc zone. Chalcopyrite is
distributed throughout all skarn zones. Appearance of sphalerite approximately coincides with the transition
from brown to green garnet. The copper-zinc zone thins at depth and originally appears to have closed over the
top of the intrusion, although most of it has been eroded. The main copper mineral in the wollastonite-diopside
skarn is bornite, and this zone also has elevated gold values. Silver, lead, and bismuth values are highest in
the outer part of the copper-zinc zone and adjacent marble. Molybdenite occurs in the intrusion and adjacent
skarn, as well as being abundant in the wollastonite-diopside skarn. Sulfides were deposited during the late prograde and retrograde phases and occur disseminated interstitial to garnet; as irregular massive sulfide zones; and as veinlets. The deposit was unroofed by glaciation and is exposed in a glacial valley; hence there is no significant oxidation or enrichment.
Antamina is an oxidized calcic copper skarn related to a calc-alkaline quartz monzonite porphyry stock containing subeconomic porphyry copper-molybdenum mineralization. The outer zinc zone is unusually well developed.
Features that appear to have contributed to Antamina’s world-class status include a possible mantle
origin of the intrusions, the basin-margin setting of the host sedimentary rocks, favorable structural preparation,
limited retrograde alteration, and partial preservation of the intrusion roof zone.
The work demonstrated that, superimposed on a pre-Mesozoic basement, the magmatic front in the Central Andes migrated systematically eastward from the coast in the Jurassic (200 Ma) to the present location in the Chile-Argentina border, forming mineral deposits at every site. However, at these latitudes only the Eocen-Oligocene (41-31 Ma) formed supergiant porphyry copper-molybdenum deposits such as Chuquicamata and El Salvador. Much of this work was based on a PhD by Zentilli, M (1974) and theses by Haynes, S. and Quirt, S. at Queen's University, Kingston, Ontario.
Chuquicamata, one of the largest porphyry copper deposits of the world, may owe its giant size to unusually favourable conditions of magma emplacement and structural control. New geochronological data indicate that the deposit formed in at least two discrete hydrothermal pulses, one around 35 Ma and one around 31 Ma, with an intervening period of exhumation. Hence the older, deeper, potassic alteration pulse brought a first input of metals, and the second, shallower, sericitic alteration phase overprinted the potassic and contributed a second metal input, accompanied by impurities such as arsenic. This sequence gave rise to a reversed pattern of zoning with a central quartz-sericite zone followed outwards by potassic and propylitic alteration. Rare earths and radiogenic isotopes indicate a rather deep source for the magmas. Mineralogical studies document. for the first time in the deposit the presence of abundant hypogene anhydrite, and hypogene covellite in addition to supergene covellite. Scant stable isotope data suggest that supergene enrichment may have developed at temperatures warmer than normal groundwater. A relatively fresh (Fortuna) granodiorite west of the (Falla Oeste) fault system, which had been previously interpreted as a magmatic precursor of the Chuquicamata porphyries, or their exhumed deep equivalent, docked structurally in the Neogene and is therefore not genetically related to Chuquicamata.
Paleozoic and Mesozoic-Cenozoic granitoids of the Chilean Andes were studied magnetically in the area between Latitude 22-35°S. The Paleozoic granitoids are found to be composed of the ilmenite-series and weakly magnetic magnetite-series, whereas all the Mesozoic-Cenozoic ones appear to be the magnetite-series. Lack of significant sulfide deposits in the Paleozoic terrains may have been resulted from the reducing nature of the granitic magmatism.
Within the magnetite-series terrains of Mesozoic-Cenozoic age, magnetic susceptibility of the granitoids seems to increase continentward. Granitoids related to porphyry copper deposits in the Andean Cordillera have higher magnetic susceptibility than those occurring in the Coast Range which could be genetically associated with manto-type deposits. The different styles of mineralization may possibly be in consequence of the different oxidation status of the granitic magmatism.
Antamina, located at latitude 9° 32' S and longitude 77° 03' W in the Ancash Department of north-central Peru, is the largest known Cu-Zn skarn ore deposit. It incorporates a mineral reserve of 561 Mt, which has an average grade of 1.24 percent Cu, 1.03 percent Zn, 13.71 g/t Ag and 0.029 percent Mo, calculated at a 0.7 per- cent Cu equiv cutoff grade. The grandite-dominated calcic skarn formed in and around an upper Miocene porphyritic monzogranite stock emplaced into Upper Cretaceous carbonate strata that had experienced thin- skinned, northeast-verging thrusting and folding in the late Eocene Incaic orogeny. The exoskarn Cu-Zn ore is discordant to the strata of the Jumasha and overlying Celendín Formations, which comprise, respectively, mas- sive to thick-bedded, relatively pure limestones and thin-bedded, predominantly marly limestones. The Jumasha Formation, the upper contact of which is locally defined as the top of the uppermost thick-bedded limestone or marble unit, hosts approximately three-quarters of the known exoskarn. Approximately the same fraction of the contiguous endoskarn Cu ore occurs adjacent to this formation. The overlying Celendín Formation is less extensively mineralized but, because it is widely metamorphosed to hornfels and locally converted to diopsidic skarnoid, may have inhibited the upward and outward migration of hydrothermal fluids, thereby promoting the development of the unusually large endoskarn ore zone. Ore also occurs in late hydrothermal breccias emplaced during the formation of mineralized endoskarn.
The preskarn thermal metamorphic aureole around the ore deposit is expressed differently in the two host formations. Jumasha Formation limestone is coarsened and bleached to banded gray marble and locally to white marble peripheral to the intrusion and skarn. Minor scapolite occurs in dark gray bands in marble, concentrated in a discontinuous halo tens of meters wide and commonly separated from the skarn by tens of metres. Three facies of calc-hornfels are recognized in the marl beds of the Celendín Formation adjacent to the intrusion extending hundreds of meters beyond sulfide-bearing skarn: a peripheral, very fine grained, light brown phlogopitic facies; an intermediate, fine-grained, gray tremolitic facies; and a proximal, medium-grained, light green diopsidic facies. At an XCO₂ of 0.1 to 0.9 and P = 100 MPa, these zones reflect temperatures in- creasing to circa 495°C adjacent to the intrusion. In addition, in nodular beds of the Celendín Formation that have been metamorphosed to hornfels, diagenetic calcite nodules are selectively replaced by diopside for distances of tens of meters beyond the skarn front. Such calc-silicate formation through both metamorphism and metasomatism, together with a 9 km² cluster of Pb-Zn-Ag vein deposits, provides district-scale vectors to ore.
The Antamina deposit lies on a newly recognized cross-strike structural discontinuity in the segmented Incaic Marañón thrust and fold belt, the northeast-trending Querococha arch. Southeast of the arch, Incaic folds and thrust faults strike north-northwest, but northwest of the arch they strike northerly. The plunge of fold axes concomitantly changes from south-southeast to north. Stratigraphic relationships indicate that the arch was a paleo-high, at least in the Jurassic and possibly throughout the late Paleozoic-early Mesozoic interval. The middle Miocene Carhuish pluton is exposed on the arch 30 km southwest of Antamina, whereas coeval Calipuy Supergroup volcanic units lie at similar altitudes to the north and south. Only scattered hydrothermal centers of late Miocene age are known in the Cordillera Negra, but an apparent swarm of intrusions, including the Antamina stock, occurs along the Querococha arch.
Antamina is situated where the locus of changes in the strike of folds and faults and the plunge of folds steps left along the arch. At Antamina, a pair of fault-bend folds above frontal thrust ramps show approximately 500 m of dextral apparent offset across the deposit and are inferred to have been separated by a northeast-striking transfer fault or lateral ramp, itself localized by a left-stepping jog in the Valley fault, an underlying, similarly oriented transverse structure. The jog in the Valley fault is inferred to have also controlled intrusion and skarn development. This local-scale jog in the Valley fault mimics the regional step along the arch. The arch may reflect a transform segment of the originally jagged, rifted continental margin, which persisted as a transverse basement weakness. Northeast-striking, originally sinistral, basement structures affected regional-scale sedimentation and structural patterns, including articulation of the thrust and fold belt. At a local scale, they influenced lateral ramp formation and related fracture development in the overlying thrust sheets. In the proposed model, they also localized later uplift and the rapid transit of small volumes of productive melt into a shallow crustal setting, conditions favorable for formation of a giant magmatic-hydrothermal ore deposit.
The Susana copper deposit is located at an elevation of 860 m above sea level in the coastal Cordillera of northern Chile (Carolina de Michilla district), 110 km north of Antofagasta at 70°10′W and 22°40′S. Initial mining began in 1981 by surface mining methods with production coming from one open bit. Due to subsequent geologic reconnaissance that resulted in the discovery of a mineralized breccia pipe structure, underground mining started in 1983. By 1983, 36000 m of drilling had shown the presence of 8 million metric tons of oxide/sulfide ore averaging 2% copper at 0.5% cutoff (Valdebenito 1983) with probable reserves several million tonnes greater. Mine production in 1985 was 1700 mt/day with Cu >3% and 20 g/mt Ag.
New Rb/Sr whole-rock data (approx 20 isochrons) and K/Ar data (approx 30 ages) are presented and interpreted within a complete geochronological review of the Coastal batholith. In particular the superunit concept of synchronous emplacement throughout the batholith is tested, in most cases with the data justifying observed stratigraphic order. Some superunits, however, exhibit considerable diachroneity, e.g. Santa Rosa (100-50 m.y.). The overall ages for the segments range approx 190-60 m.y. for Toquepala, approx 100-24 m.y. for Arequipa and approx 100-37 m.y. for Lima. Some superunits yield ages much younger than expected, e.g. the newly defined Linga-Arequipa (Toquepala segment). Initial 87Sr/ 86Sr ratios are mostly 0.7040-0.7043 for the Lima segment, indicating a uniform mantle source region, but range <0.708 in the Arequipa segment due to contamination from the Precambrian envelope. K/Ar ages of approx 10 m.y. for the Cordillera Blanca batholith and 11 O-isotope analyses are also reported.-R.J.P.
By examining published data on geology, geochemistry and mineralogy of host rocks and ore deposits, it is suggested that dehydration processes due to advanced burial metamorphism might be responsible for the formation of the Chilean manto type copper deposits. Accumulation of thick eugeosynclinal piles containing abundant Cu-rich volcanic rocks in the western part of the Andean geosyncline during the Jurassic and Cretaceous times, may explain why the Chilean Coastal Range is rich in this unique type of copper deposit.-Y.K.
The main copper oxide minerals in the Radomiro Tomic deposit are atacamite, copper clays, chrysocolla, and copper wad. Their relative abundance provides the basis for dividing the oxide zone into two major geologic units: the Upper Oxide unit and the Lower Oxide unit. Furthermore, the study of mineral abundances in the oxide zones allowed the definition of an oxide mineral zonation that consists of five mineral assemblages, based on the relative proportion of the three main copper oxide components: atacamite, copper clays, and chrysocolla. These classifications allow both an understanding of the distribution of copper minerals throughout the zone and an interpretation of the supergene processes that formed it. The Upper Oxide unit is mineralogically heterogeneous. The copper content is furnished, on average, by 40 vol percent atacamite, 31 vol percent copper clays with minor chysocolla and copper wad. The Lower Oxide unit is more homogeneous. Atacamite accounts for 70 vol percent of the copper ore minerals with minor amounts of copper clays and chrysocolla. Copper and chlorine concentrations and porosity are greater in the Upper Oxide unit, whereas hematite, chalcocite, and molybdenite concentrations and specific gravity are greater in the Lower Oxide unit. The vertical distribution of the Cl/Cu ratio shows a chlorine-deficient zone located between elevations of 2,780 and 2,870 m. Between these elevations, the proportion of atacamite is lower and the proportion of copper clays, chrysocolla, and copper wad is higher than in other portions of either the Upper Oxide or Lower Oxide units. The oxide zone at Radomiro Tomic was originated through the in situ oxidation of a preexisting secondary sulfide enrichment blanket. Oxidation produced an extensive zone of atacamite, accompanied by weakly developed argillic alteration. The upper part of the deposit was further enriched by lateral migration of copper-rich solutions to the north and east, where copper precipitated as chrysocolla, copper wad, and copper in clays. In these areas, strong argillic alteration, characterized by the presence of montmorillonite, was developed. This second alteration phase impacted only the uppermost portion of the oxide zone and the base of overlying gravels.
Chemical data are used to subdivide the Mitu group into alkali basaltic, shoshonitic and peralkaline suites. REE data for the first two demonstrated mantle melting with residual garnet. Uniformly low initial 87Sr/86Sr ratios (<0.705) rule out crustal contamination but the three suites are not interrelated by liquid-crystal fractionation processes. The first two suites are 250-270 m.y. old but the peralkaline suite may be Jurassic. Petrological and geochemical data (including biotite chemistry) are also summarized for the peralkaline intrusive rocks. U/Pb zircon ages of 234 and 238 m.y. are interpreted as dating initial intrusion, and discordant Rb/Sr and K/Ar ages of 211-176 m.y. are related to uplift and erosion. It is suggested that the granites resulted from melting of the lower crust triggered by 'ponding' of the Mitu group basalt magmas during crustal rifting and comparison is made with the Oslo graben.-R.J.P.
