scholarly journals An abrupt switch in magmatic plumbing taps porphyry copper deposit-forming magmas

2021 ◽  
Author(s):  
Lawrence Carter ◽  
Simon Tapster ◽  
Ben Williamson ◽  
Yannick Buret ◽  
David Selby ◽  
...  
Keyword(s):  
Porphyry Copper ◽  
Copper Deposit ◽  
Ore Deposits ◽  
Green Technology ◽  
Ore Formation ◽  
Porphyry Deposits ◽  
Order Of Magnitude ◽  
Magmatic Plumbing System ◽  
Lower Crustal ◽  
Melt Evolution

Abstract Porphyry-type deposits are a vital source of green technology metals such as copper and molybdenum. They typically form in subduction-related settings from large, long-lived magmatic systems. The most widely accepted model for their formation requires that mantle-derived magmas undergo a multi-million year timescale ramp-up in volatiles and ore-forming constituents in mid- to lower-crustal reservoirs, however this does not explain why porphyry deposits are absent from the vast majority of arc magmatic systems. To address this, we have carried out geochemical and geochronological studies on the tilted, ~8 km depth equivalent, cross-section through the classic Yerington magmatic system, Nevada. Here we show that the magmas underwent a major and abrupt change in chemistry over a period of 100 kyrs which is coincident with the initiation of ore formation. This is attributed to a wholesale switch in the magmatic plumbing system whereby volatile-rich granitic melts were extracted from an estimated ~30 km depth and transported to shallow levels (~3-8 km) where exsolving fluids were focussed through highly permeable pathways to form porphyry deposits. The change in magma chemistry is documented across the entire plutonic to volcanic record. Its rapidity suggests that the increase in a magma’s ore-forming potential is not solely driven by tectonic factors, that occur over multi-million year scales, but through internal processes within the melt evolution zone, operating at more than an order of magnitude faster than previously envisaged. This short timescale narrows the temporal-geochemical footprint of magmas associated with porphyry mineralisation which will aid in targeting the next generation of ore deposits.

Application of plurigaussian simulation to delineate the layout of alteration domains in Sungun copper deposit

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Hassan Talebi ◽  
Omid Asghari ◽  
Xavier Emery
Keyword(s):  
Numerical Models ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Ore Deposits ◽  
Accurate Estimation ◽  
Deterministic Models ◽  
Plurigaussian Simulation ◽  
Domain Boundaries ◽  
Drill Holes

AbstractAn accurate estimation of mineral grades in ore deposits with heterogeneous spatial variations requires defining geological domains that differentiate the types of mineralogy, alteration and lithology. Deterministic models define the layout of the domains based on the interpretation of the drill holes and do not take into account the uncertainty in areas with fewer data. Plurigaussian simulation (PGS) can be an alternative to generate multiple numerical models of the ore body, with the aim of assessing the uncertainty in the domain boundaries and improving the geological controls in the characterization of quantitative attributes. This study addresses the application of PGS to Sungun porphyry copper deposit (Iran), in order to simulate the layout of four hypogene alteration zones: potassic, phyllic, propylitic and argillic. The aim of this study is to construct numerical models in which the alteration structures reflect the evolution observed in the geology.

Sparse 3D seismic and magnetic imaging at Escondida porphyry copper mine, Chile

2021 ◽  
Vol 40 (2) ◽  
pp. 114-121
Author(s):  
Heather Schijns ◽  
Gabriel Madero ◽  
Jorge Bugueño ◽  
Andres Salazar ◽  
Todd Grant
Keyword(s):  
Low Cost ◽  
Porphyry Copper ◽  
Magnetization Vector ◽  
Copper Deposit ◽  
Seismic Survey ◽  
3D Seismic ◽  
Mining Operations ◽  
Porphyry Deposits ◽  
Magnetic Imaging ◽  
Airborne Survey

Seismic is often inferred to be synonymous with high cost. In a mineral environment, it is typically assumed to be viable only for mining operations or brownfield exploration. For greenfield exploration, other geophysical and geochemical/lithogeochemical methods are usually preferred, due in part to their affordability. We show results of a low-cost seismic survey over the Escondida porphyry copper deposit. The results show that low-cost 3D acquisition can improve structural understanding of established porphyry deposits and that there is potential for 3D seismic to be applied in brownfield and perhaps even greenfield exploration. The sparse 3D seismic reflection survey acquired at Escondida illuminates the structural setting and images stock genetically related to the Escondida intrusive complex at depth. The seismic results are compared to a magnetization vector inversion calculated from a regional airborne survey. This illustrates the potential for jointly utilizing the two methods to identify and prioritize anomalies for targeted drilling-based follow-up in exploration settings.

scholarly journals Base metal mineralization of the Kolyma terrain in Northeast Russia: Overview and genetic classification

LITOSFERA ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 717-730
Author(s):  
A. N. Glukhov
Keyword(s):  
Porphyry Copper ◽  
Copper Deposit ◽  
Genetic Classification ◽  
Northeast Russia ◽  
Ore Formation ◽  
Quartz Veins ◽  
Cyclic Changes ◽  
Academy Of Sciences ◽  
Far Eastern ◽  
Base Metal Mineralization

Research subject. The Prikolyma terrain located in the Northeastern part ofRussia constitutes a long-lived Precambrian thrust-faulted structure hosting numerous Cu, Pb and Zn deposits of different types.Materials and methods. The mineralization of the terrain was examined during a course of research and exploration works over the 2007–2012. The rock geochemistry was studied using ICP-OES analysis at the Stuart Geochemistry and Essay laboratory (Moscow). The microprobe analysis of minerals was carried out at the facilities of the Far Eastern Branch of the Russian Academy of Sciences (Magadan) using a Camebax X-ray microanalyzer. The isotopic ratios of sulphur in sulphides were measured using a Finnigan MAT 253 isotope mass spectrometer.Results. The porphyry-copper deposit Nevidimka is represented by skarns and sulphide-quartz stockworks embedded in porphyry granites. The vein deposits Opyt and Glukhoye constitute sulphide-carbonate-quartz veins, the composition of which corresponds to copper-polymetallic ores of the peripheral parts of the copper-porphyry formation. These deposits feature a similar geochemistry and composition of sulphides and sulphur isotopes, which is characteristic of the Riphean complexes of the Prikolyma terrain. The stratiform Pb-Zn veins Nadezhda-3 and Khaya enclosed in Proterozoic dolomites represent parallel-bedding disseminated sulphides. The composition of these ores indicates their diagenetic origin. Tne stratiform copper deposit Oroyok is embedded in Proterozoic shales and can be referred to sediment-hosted copper deposits of a transgressive type.Conclusions. The diversity of Cu-Pb-Zn mineralization types in the Prikolyma terrain is established to have resulted from multiple cyclic changes of the geodynamic ore formation regime. During each such cycle, syngenetic mineralization was followed first by epigenetic and then by vein mineralization. The mobile, thrust-faulted structure caused repeated rejuvenation of ores, which inherited the geochemical features of hosting rocks. 

scholarly journals Porphyry copper deposit formation in arcs: What are the odds?

Geosphere ◽  
2021 ◽  
Author(s):  
Jeremy P. Richards ◽  
Matthew Leybourne
Keyword(s):  
Hydrothermal Fluid ◽  
Subduction Zones ◽  
Porphyry Copper ◽  
Fluid Phase ◽  
Copper Deposit ◽  
Ore Deposits ◽  
Water Soluble ◽  
Cumulative Probability ◽  
High Threshold ◽  
Porphyry Cu

Arc magmas globally are H2O-Cl-S–rich and moderately oxidized (ΔFMQ = +1 to +2) relative to most other mantle-derived magmas (ΔFMQ ≤ 0). Their relatively high oxidation state limits the extent to which sulfide phases separate from the magma, which would otherwise tend to deplete the melt in chalcophile elements such as Cu (highly siderophile elements such as Au and especially platinum-group elements are depleted by even small amounts of sulfide segregation). As these magmas rise into the crust and begin to crystallize, they will reach volatile saturation, and a hydrous, saline, S-rich, moderately oxidized fluid is released, into which chalcophile and any remaining siderophile metals (as well as many other water-soluble elements) will strongly partition. This magmatic-hydrothermal fluid phase has the potential to form ore deposits (most commonly porphyry Cu ± Mo ± Au deposits) if its metal load is precipitated in economic concentrations, but there are many steps along the way that must be successfully negotiated before this can occur. This paper seeks to identify the main steps along the path from magma genesis to hydrothermal mineral precipitation that affect the chances of forming an ore deposit (defined as an economically mineable resource) and attempts to estimate the probability of achieving each step. The cumulative probability of forming a large porphyry Cu deposit at any given time in an arc magmatic system (i.e., a single batholith-linked volcanoplutonic complex) is estimated to be ~0.001%, and less than 1/10 of these deposits will be uplifted and exposed at shallow enough depths to mine economically (0.0001%). Continued uplift and ero­sion in active convergent tectonic regimes rapidly remove these upper-crustal deposits from the geological record, such that the probability of finding them in older arc systems decreases further with age, to the point that porphyry Cu deposits are almost nonexistent in Precambrian rocks. A key finding of this paper is that most volcanoplutonic arcs above subduction zones are prospective for porphyry ore formation, with prob­abilities only falling to low values at late stages of magmatic-hydrothermal fluid exsolution, focusing, and metal deposition. This is in part because of the high threshold required in terms of grade and tonnage for a deposit to be considered economic. Thus, the probability of forming a porphyry-type system in any given arc segment is relatively high, but the probability that it will be a large economic deposit is low, dictated to a large extent by mineral economics and metal prices.

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