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.

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.

Tracing Mineralogy and Alteration Intensity Using the Spectral Alteration Index and Depth Ratios at the Northwest Zone of the Lemarchant Volcanogenic Massive Sulfide Deposit, Newfoundland, Canada

2020 ◽  
Vol 115 (5) ◽  
pp. 1055-1078
Author(s):  
Jonathan Cloutier ◽  
Stephen J. Piercey
Keyword(s):  
Mineral Exploration ◽  
Massive Sulfide ◽  
White Mica ◽  
Sulfide Deposit ◽  
Hyperspectral Reflectance ◽  
Volcanogenic Massive Sulfide ◽  
Novel Approach ◽  
Vms Deposits ◽  
Alteration Processes ◽  
Absorption Features

Abstract The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration parameters that can be used in real time. The precious metal-bearing, bimodal-felsic Northwest zone of the Lemarchant volcanogenic massive sulfide (VMS) deposits, Newfoundland, Canada, is used as a case study. Alteration associated with the Northwest zone includes intense and localized sulfide (pyrite, chalcopyrite, sphalerite, and galena) and barite enrichment, as well as quartz, white mica, and chlorite alteration. Zones of elevated Zn (>5,000 ppm) are associated with high chlorite carbonate pyrite index (CCPI), Ishikawa alteration index (AI), Ba/Sr, and low Na2O values and elevated SiO2 and K2O, Fe2O3, Na2O, and BaO contents, similar to global alteration signatures in VMS deposits. Mineralized areas contain phengitic white micas with 2,200-nm absorption features longer than 2,215 nm and Mg-rich chlorites with 2,250-nm absorption features shorter than 2,252 nm. Together, these data are consistent with the Northwest zone having undergone intense hydrothermal alteration during the mineralization event. A new lithology-normalized spectral alteration index (SAI) for white mica and chlorite was developed in order to map and characterize the alteration intensity surrounding the deposit. In addition, depth ratio parameters (2200D/2340D vs. 2250D/2340D) were used to characterize mineralogical changes and zonation. Together, these features document a paleofluid pathway with Mg chlorite alteration extending to at least 300 m away from the mineralization, outside the study area, within the andesitic and dacitic units. The use of hyperspectral reflectance coupled with geochemical alteration proxies permitted the identification of areas of intense alteration, the chemical affinities of the minerals, and their relationships to alteration processes (i.e., seawater alteration versus silicification), which would not be possible using geochemistry alone.

Interpretation of borehole gravity data of the Lalor volcanogenic massive sulfide deposit, Snow Lake, Manitoba, Canada

2015 ◽  
Vol 3 (3) ◽  
pp. T145-T154 ◽  
Author(s):  
Ernst Schetselaar ◽  
Pejman Shamsipour
Keyword(s):  
Gravity Data ◽  
Hanging Wall ◽  
Bouguer Anomaly ◽  
Massive Sulfide ◽  
Geological Mapping ◽  
Sulfide Deposit ◽  
Massive Sulfide Deposit ◽  
Volcanogenic Massive Sulfide ◽  
Volcanogenic Massive Sulfide Deposit ◽  
Gamma Density

We have acquired borehole gravity data along five drillholes intersecting the Lalor volcanogenic massive sulfide deposit hosted in the eastern Flin Flon greenstone belt at Snow Lake, Manitoba, Canada. Inverted apparent interval density (IAID) logs were calculated from the borehole gravity data and compared with lithofacies and [Formula: see text] logs; the latter of which is a geochemical proxy for differentiating volcanic rocks of felsic to mafic composition. The IAID anomalies predominantly reflect alternating mafic and felsic volcanic rock units in the footwall and hanging wall of the massive sulfide deposit. IAID lows are associated with [Formula: see text] highs that correspond to rhyolite and rhyodacite intervals in the hanging wall. IAID lows with associated [Formula: see text] peaks in the footwall occur within intervals of gneiss and schist formed by metamorphism of hydrothermally altered rocks, suggesting that these IAID lows still reflect the felsic composition of their volcanic protoliths. A significant peak-to-peak Bouguer anomaly of 0.66 mGal caused by an estimated excess mass of 0.7 mT can be correlated with gamma-gamma density signature of the main sulfide ore zone in three boreholes. This anomaly is aligned with the ore zone after restoring the displacement along a northeast-dipping structure. When integrated with drillhole lithology and lithogeochemistry logs, gravity borehole data can, in addition to the direct detection of mineralization, be used as a subsurface geological mapping tool.

Sign in / Sign up

Export Citation Format

Share Document