scholarly journals Vectors to ore in replacive volcanogenic massive sulfide (VMS) deposits of the northern Iberian Pyrite Belt: mineral zoning, whole rock geochemistry, and application of portable X-ray fluorescence

Solid Earth ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1931-1966
Author(s):  
Guillem Gisbert ◽  
Fernando Tornos ◽  
Emma Losantos ◽  
Juan Manuel Pons ◽  
Juan Carlos Videira
Keyword(s):  
Hydrothermal Alteration ◽  
Hanging Wall ◽  
Massive Sulfide ◽  
Iberian Pyrite Belt ◽  
Major Elements ◽  
Alteration Zone ◽  
Volcanogenic Massive Sulfide ◽  
X Ray ◽  
Sequence Characterization ◽  
Vms Deposits

Abstract. In this work we have performed a detailed study of vectors to ore to a representative volcanic-rock-hosted replacive volcanogenic massive sulfide (VMS) deposit located in the northern Iberian Pyrite Belt (Spain), the Aguas Teñidas deposit. The investigated vectors include the following: (1) mineralogical zoning, (2) host sequence characterization and mineralized unit identification based on whole rock geochemistry discrimination diagrams, (3) study of the characteristics and behaviour of whole rock geochemical anomalies around the ore (e.g. alteration-related compositional changes, characteristics and extent of geochemical halos of indicative elements such as Cu, Zn, Pb, Sb, Tl, and Ba around the deposit), and (4) application of portable X-ray fluorescence (p-XRF) analysis to the detection of the previous vectors. In the footwall, a concentric cone-shaped hydrothermal alteration zone bearing the stockwork passes laterally, from core to edge, from quartz (only local) to chlorite–quartz, sericite–chlorite–quartz, and sericite–quartz alteration zones. The hydrothermal alteration is also found in the hanging wall despite being tectonically allochthonous to the orebody: a proximal sericite alteration zone is followed by a more distal albite-rich one. Whole rock major elements show an increase in alteration indexes (e.g. AI, CCPI) towards the mineralization, a general SiO2 enrichment, and FeO enrichment as well as K2O and Na2O depletion towards the centre of the hydrothermal system, with MgO showing a less systematic behaviour. K2O and Na2O leached from the centre of the system are transported and deposited in more external areas. Copper, Pb, and Zn produce proximal anomalies around mineralized areas, with the more mobile Sb, Tl, and Ba generating wider halos. Whereas Sb and Tl halos form around all mineralized areas, Ba anomalies are restricted to areas around the massive sulfide body. Our results show that proposed vectors, or adaptations designed to overcome p-XRF limitations, can be confidently used by analysing unprepared hand specimens, including the external rough curved surface of drill cores. The data presented in this work are not only applicable to VMS exploration in the Iberian Pyrite Belt, but on a broader scale they will also contribute to improving our general understanding of vectors to ore in replacive-type VMS deposits.

scholarly journals Vectors to ore in replacive VMS deposits of the northern Iberian Pyrite Belt: mineral zoning, whole rock geochemistry, and use of portable XRF

2021 ◽  
Author(s):  
Guillem Gisbert ◽  
Fernando Tornos ◽  
Emma Losantos ◽  
Juan Manuel Pons ◽  
Juan Carlos Videira
Keyword(s):  
Hydrothermal Alteration ◽  
Hanging Wall ◽  
Iberian Pyrite Belt ◽  
Major Elements ◽  
Massive Sulphide ◽  
Alteration Zone ◽  
Portable Xrf ◽  
Sequence Characterization ◽  
Vms Deposits ◽  
Mineral Zoning

Abstract. Volcanogenic Massive Sulphide (VMS) deposits represent a major source of base, precious and other metals of economic and industrial importance. As in other mineral systems, progressive exhaustion of the shallowest and most easily accessible deposits is leading to increasingly complex exploration. In this context vectors to ore play a vital role. The Iberian Pyrite Belt (IPB) is an outstanding VMS district located in the SW Iberian Peninsula, which represents the main mining area in Spain and one of the main zones of base metal production in Europe. But the work on vectors to ore in the IPB is far from systematic or complete. In this work we have performed a detailed study of the main vectors to ore related to mineral zoning and whole rock geochemistry that are currently used in the exploration of VMS systems to a representative volcanic rock hosted replacive VMS deposit located in the northern IPB, the Aguas Teñidas deposit. Results have been compared to other deposits in the IPB and in other VMS districts. The investigated vectors include: mineralogical zoning, host sequence characterization and mineralized unit identification based on whole rock geochemistry, the study of the characteristics and behaviour of whole rock geochemical anomalies around the ore (e.g. alteration-related compositional changes, characteristics and extent of geochemical halos around the deposit), with definition of threshold values for the mineralization-related indicative elements, and application of portable XRF analysis to the detection of the previous vectors. In the footwall, a concentric cone-shaped hydrothermal alteration bearing the stockwork passes laterally, from core to edge, from quartz (only locally), to chlorite, sericite–chlorite, and sericite alteration zones. The hydrothermal alteration is also found in the hanging wall despite its thrusted character: a proximal sericite alteration zone is followed by a more distal albite one, which is described here for the first time in the IPB. Whole rock major elements show an increase in alteration indexes (e.g. AI, CCPI) towards the mineralization, with a general SiO2 enrichment, FeO enrichment in the central portion of the system, K2O and Na2O leaching towards the outside areas, and a less systematic MgO behaviour. Copper, Pb and Zn produce proximal anomalies around mineralized areas, with the more mobile Sb, Tl and Ba generating wider halos. Whereas Sb and Tl halos form around all mineralized areas, Ba anomalies are restricted to areas around the massive sulphide body. Our results show that proposed vectors, or adaptations designed to overcome p-XRF limitations, can be confidently used by analysing unprepared hand specimens, including the external rough curved surface of drill cores. The data presented in this work are not only applicable to VMS exploration in the IPB, but on a broader scale they will also contribute to improve our general understating of vectors to ore in replacive-type VMS deposits.

Petrochemistry, hydrothermal alteration, mineralogy, and sulfur isotope geochemistry of the Turgeon Cu–Zn volcanogenic massive sulfide deposit, northern New Brunswick, Canada

2015 ◽  
Vol 52 (4) ◽  
pp. 215-234 ◽  
Author(s):  
Erik Lalonde ◽  
Georges Beaudoin
Keyword(s):  
New Brunswick ◽  
Hydrothermal Alteration ◽  
Hanging Wall ◽  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Trace Element Geochemistry ◽  
Volcanogenic Massive Sulfide ◽  
Element Geochemistry ◽  
Vms Deposits ◽  
Ocean Ridge

The Turgeon deposit is a mafic-type, Cu–Zn volcanogenic massive sulfide (VMS) deposit. It is hosted by Middle Ordovician pillow basalts of the Devereaux Formation of the Fournier Group within the Elmtree-Belledune inlier, near the Bathurst Mining Camp (BMC) in northern New Brunswick, Canada. The Turgeon deposit consists of two Cu–Zn massive sulfide lenses (“100m Zn”, “48-49”) composed of pyrite, chalcopyrite, pyrrhotite, and sphalerite, which are underlain by chalcopyrite–pyrite stockwork veins. Pyrite is overprinted and replaced by chalcopyrite in the stockwork and vent complex sulfide facies, where both minerals are enriched in Se and Co relative to pyrite and chalcopyrite in the massive pyrite and breccia sulfide facies. In, Se, and Co display a positive covariation with Cu, whereas Zn displays a positive covariation with Cd. Trace element geochemistry indicates that the host rocks are primarily tholeiitic basalts and andesites that have signatures between that of mid-ocean ridge basalt and island-arc tholeiite. The hanging wall rhyolite plots as an ocean ridge rhyolite and is geochemically similar to VMS-bearing FIIIa-type rhyolites. Hydrothermal alteration mineral assemblages in the footwall basalts proximal to mineralization are dominantly chlorite ± quartz in the stockwork zone, which is characterized by compositional gains in Fe and Mg and losses in Na and Ca. The chlorite-altered basalts and andesites have undergone up to 35% mass loss. Stockwork chlorite is an Fe-rich chamosite, whereas chlorite in the massive sulfides is a Mg-rich clinochlore. Chlorite geothermometry yields temperatures of 329–361 °C for chamosite and 246–286 °C for clinochlore. Sulfides at Turgeon have an average δ34SCDT of +6.9‰ (range: +5.8‰ to +10‰), indicating that sulfur was mostly derived from thermochemical reduction of Ordovician seawater sulfate. The Turgeon VMS deposit differs from those of the BMC, which is a reflection of their different tectonic settings; but it is similar to other mafic-type VMS deposits, such as the Betts Cove, Tilt Cove, and Rambler VMS deposits in Newfoundland, Canada.

Early thrusting and folding in the Snow Lake camp, Manitoba: tectonic implications and effects on volcanogenic massive sulfide deposits

2018 ◽  
Vol 55 (8) ◽  
pp. 935-957 ◽  
Author(s):  
Margaret S. Stewart ◽  
Bruno Lafrance ◽  
Harold L. Gibson
Keyword(s):  
Hanging Wall ◽  
Precious Metals ◽  
Massive Sulfide ◽  
Deformation History ◽  
Volcanogenic Massive Sulfide ◽  
Sulfide Deposits ◽  
The North ◽  
Vms Deposits ◽  
Deformation Event ◽  
Primary Base

The Chisel sequence occurs within the Snow Lake arc assemblage (SLA) of the Paleoproterozoic Trans-Hudson Orogen. It is host to six economic volcanogenic massive sulfide (VMS) deposits that formed within a single time-stratigraphic ore interval. The SLA was previously interpreted to share the same deformation history as the ca. 1.86–1.84 Ga Burntwood Group turbidites of the Kisseynew Basin to the north; however, early isoclinal folds identified in the arc assemblage cannot be correlated with structures in the turbidites and therefore developed prior to Burntwood Group deposition. This indicates that the SLA underwent a significant deformation event prior to 1.86 Ga, likely due to intraoceanic accretion or pre-1.86 Ga accretion to the Amisk collage during closure of the ancestral Manikewan Ocean. Evidence for this early folding event is recorded in the Chisel sequence deposits where it has influenced the geometry of the deposits and the location of the ore interval. The deposits are isoclinally folded by these folds, and a major early thrust fault at the Lalor deposit, the Lalor-Chisel fault, displaced the hanging-wall rocks of the deposit and the ore interval. Further flattening, transposition, and elongation of the ore lenses occurred during post-1.84 Ga collision of the SLA with the partially hidden Archean Sask craton. Although the VMS deposits are polydeformed and sulfides and precious metals were mechanically and hydrothermally remobilized at the metre scale, their primary base metal zoning remains intact and provides a tool to reconstruct the geometry of the deposits.

Pb-Nd-Sr Isotope Geochemistry of Metapelites from the Iberian Pyrite Belt and Its Relevance to Provenance Analysis and Mineral Exploration Surveys

2021 ◽  
Author(s):  
Filipa Luz ◽  
António Mateus ◽  
Ezequiel Ferreira ◽  
Colombo G. Tassinari ◽  
Jorge Figueiras
Keyword(s):  
Isotope Geochemistry ◽  
Mineral Exploration ◽  
Hanging Wall ◽  
Massive Sulfide ◽  
Iberian Pyrite Belt ◽  
Isotopic Signature ◽  
Sr Isotope ◽  
Provenance Analysis ◽  
Basement Rocks ◽  
World Class

Abstract The boundary in the Iberian Pyrite Belt is a world-class metallogenic district developed at the Devonian-Carboniferous boundary the Iberian Variscides that currently has seven active mines: Neves Corvo (Cu-Zn-Sn) and Aljustrel (Cu-Zn) in Portugal, and Riotinto (Cu), Las Cruces (Cu), Aguas Teñidas (Cu-Zn-Pb), Sotiel-Coronada (Cu-Zn-Pb), and La Magdalena (Cu-Zn-Pb) in Spain. The Iberian Pyrite Belt massive sulfide ores are usually hosted in the lower sections of the volcano-sedimentary complex (late Famennian to late Visean), but they also occur in the uppermost levels of the phyllite-quartzite group at the Neves Corvo deposit, stratigraphically below the volcano-sedimentary complex. A Pb-Nd-Sr isotope dataset was obtained for 98 Iberian Pyrite Belt metapelite samples (from Givetian to upper Visean), representing several phyllite-quartzite group and volcano-sedimentary complex sections that include the footwall and hanging-wall domains of ore horizons at the Neves Corvo, Aljustrel, and Lousal mines. The combination of whole-rock Nd and Sr isotopes with Th/Sc ratios shows that the siliciclastic components of Iberian Pyrite Belt metapelites are derived from older quartz-feldspathic basement rocks (–11 ≤ εNdinitial(i) ≤ –8 and (87Sr/86Sr)i up to 0.727). The younger volcano-sedimentary complex metapelites (upper Tournaisian) often comprise volcanic-derived constituents with a juvenile isotopic signature, shifting the εNdi up to +0.2. The Pb isotope data confirm that the phyllite-quartzite group and volcano-sedimentary complex successions are crustal reservoirs for metals found in the deposits. In Neves Corvo, where there is more significant Sn- and Cu-rich mineralization, the higher (206Pb/204Pb)i and (207Pb/204Pb)i values displayed by phyllite-quartzite group and lower volcano-sedimentary complex metapelites (up to 15.66 and 18.33, respectively) suggest additional contributions to the metal budget from a deeper and more radiogenic source. The proximity to Iberian Pyrite Belt massive sulfide ore systems hosted in metapelite successions is observed when (207Pb/204Pb)i >15.60 and Fe2O3/TiO2 or (Cu+Zn+Pb)/Sc >10. These are important criteria that should be considered in geochemical exploration surveys designed for the Iberian Pyrite Belt.

The Westwood Deposit, Southern Abitibi Greenstone Belt, Canada: An Archean Au-Rich Polymetallic Magmatic-Hydrothermal System—Part II. Hydrothermal Alteration, Mineralization, and Geologic Model

2021 ◽  
Author(s):  
D. Yergeau ◽  
P. Mercier-Langevin ◽  
B. Dubé ◽  
V. McNicoll ◽  
S. E. Jackson ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Greenstone Belt ◽  
Massive Sulfide ◽  
Alteration Zone ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
The North ◽  
Vms Deposits ◽  
Ore Zones

Abstract The Westwood deposit, located in the Archean Doyon-Bousquet-LaRonde mining camp in the southern Archean Abitibi greenstone belt, contains 4.5 Moz (140 metric t) of gold. The deposit is hosted in the 2699–2695 Ma submarine, tholeiitic to calc-alkaline volcanic, volcaniclastic, and intrusive rocks of the Bousquet Formation. The deposit is located near the synvolcanic (ca. 2699–2696 Ma) Mooshla Intrusive Complex that hosts the Doyon epizonal intrusion-related Au ± Cu deposit, whereas several Au-rich volcanogenic massive sulfide (VMS) deposits are present east of the Westwood deposit. The Westwood deposit consists of stratigraphically stacked, contrasting, and overprinting mineralization styles that share analogies with both the intrusion-related and VMS deposits of the camp. The ore zones form three distinct, slightly discordant to stratabound corridors that are, from north (base) to south (top), the Zone 2 Extension, the North Corridor, and the Westwood Corridor. Syn- to late-main regional deformation and upper greenschist to lower amphibolite facies regional metamorphism affect the ore zones, alteration assemblages, and host rocks. The Zone 2 Extension consists of Au ± Cu sulfide (pyrite-chalcopyrite)-quartz veins and zones of disseminated to semimassive sulfides. The ore zones are spatially associated with a series of calc-alkaline felsic sills and dikes that crosscut the mafic to intermediate, tholeiitic to transitional, lower Bousquet Formation volcanic rocks. The metamorphosed proximal alteration consists of muscovite-quartz-pyrite ± gypsum-andalusite-kyanite-pyrophyllite argillic to advanced argillic-style tabular envelope that is up to a few tens of meters thick. The North Corridor consists of auriferous semimassive to massive sulfide veins, zones of sulfide stringers, and disseminated sulfides that are hosted in intermediate volcaniclastic rocks at the base of the upper Bousquet Formation. The Westwood Corridor consists of semimassive to massive sulfide lenses, veins, zones of sulfide stringers, and disseminated sulfides that are located higher in the stratigraphic sequence, at or near the contact between calc-alkaline dacite domes and overlying calc-alkaline rhyodacite of the upper Bousquet Formation. A large, semiconformable distal alteration zone that encompasses the North Corridor is present in the footwall and vicinity of the Westwood Corridor. This metamorphosed alteration zone consists of an assemblage of biotite-Mn garnet-chlorite-carbonate ± muscovite-albite. A proximal muscovite-quartz-chlorite-pyrite argillic-style alteration assemblage is associated with both corridors. The Zone 2 Extension ore zones and associated alteration are considered synvolcanic based on crosscutting relationships and U-Pb geochronology and are interpreted as being the distal expression of an epizonal magmatic-hydrothermal system that is centered on the upper part of the synvolcanic Mooshla Intrusive Complex. The North and Westwood corridors consist of bimodal-felsic Au-rich VMS-type mineralization and alteration produced by the convective circulation of modified seawater that included a magmatic contribution from the coeval epizonal Zone 2 Extension magmatic-hydrothermal system. The Westwood Au deposit represents one of the very few documented examples of an Archean magmatic-hydrothermal system—or at least of such systems formed in a subaqueous environment. The study of the Westwood deposit resulted in a better understanding of the critical role of magmatic fluid input toward the formation of Archean epizonal intrusion-related Au ± Cu and seafloor/subseafloor Au-rich VMS-type mineralization.

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