scholarly journals Geodynamic conditions of massive sulfide formation in the Magnitogorsk megazone

LITOSFERA ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 775-804
Author(s):  
A. М. Kosarev ◽  
V. N. Puchkov ◽  
Igor B. Seravkin ◽  
Gulnara T. Shafigullina
Keyword(s):  
Deep Structure ◽  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Southern Urals ◽  
Island Arcs ◽  
The Southern Urals ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits ◽  
Deep Wells ◽  
Geodynamic Reconstructions

Research subject. Volcanism, rock geochemistry, geodynamics, and massive sulfide formation in the Magnitogorsk megazone (MMZ) of the Southern Urals in the Middle Paleozoic.Materials and Methods. Across the largest part of the massive sulfide deposits under investigation, the authors conducted route studies, including geological surveys of individual ore fields and quarries of deposits, core samples of deep wells and transparent sections. Representative analyses of petrogenic and microelements were performed using wet chemistry and ICP-MS in analytical centers in Russia and Europe. Along with the authors’ data, analytical materials published by Russian and foreign researchers were used. Geodynamic reconstructions were carried out taking into account regional data on gravics, thermal field, magnetometry, and seismic stu dies, including «Urseis-95».Results. The geodynamic reconstructions established that the main elements of the paleostructure of the Southern Urals in the Devonian were the subduction zone of the eastern dip and asthenospheric diapirs that penetrated into the «slab-window», which determined the type of volcanic belts, the composition and volume of volcanic rocks of pyrite-bearing complexes, and ore matter of pyrite deposits. The following geodynamic zones in the MMZ were identified: 1 – polychronous accretion prism; 2 – frontal and developed island arcs (D1e2–D2ef1); 3 – zone of back-arc spreading (D1e2); 4 – rear island arc (D2ef1).Conclusions. All investigated zones and ore areas are characterized by an autonomous development of volcanism, a special deep structure and a different composition, as well as by a different volume of massive sulfide deposits that vary in the Cu and Zn ratios and Pb, Ba, Au amounts. In the MMZ volcanic complexes, three groups of plume source basalts are distinguished. The results can be used in predictive-estimation and search operations for massive sulfide mineralization.

Silver sulfotellurides from volcanic-hosted massive sulfide deposits in the Southern Urals

2006 ◽  
Vol 87 (3-4) ◽  
pp. 327-349 ◽  
Author(s):  
K. A. Novoselov ◽  
E. V. Belogub ◽  
V. V. Zaykov ◽  
V. A. Yakovleva
Keyword(s):  
Massive Sulfide ◽  
Southern Urals ◽  
The Southern Urals ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits

scholarly journals Geologic interpretation of aeromagnetic and chemical data from the Oaks Belt, Wabigoon subprovince, Minnesota: implications for Au-rich VMS deposit exploration

2016 ◽  
Vol 53 (2) ◽  
pp. 176-188 ◽  
Author(s):  
Michael D. Hendrickson
Keyword(s):  
Base Metal ◽  
Volcanic Rocks ◽  
Correlation Coefficients ◽  
Massive Sulfide ◽  
Iron Formation ◽  
Geochemical Data ◽  
Volcanic Complex ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits ◽  
Subvolcanic Intrusion

The Oaks Belt (OB) is a Neoarchean volcanic complex located in northwestern Minnesota, USA. It is part of the Wabigoon granite–greenstone terrane that hosts the world-class Rainy River gold deposit in nearby Ontario, Canada. Rocks in the OB form a north-dipping homocline in the fault-bounded pressure shadow of a sigma-shaped volcano-plutonic wedge that spans east–west for 220 km across the Minnesota, USA – Ontario, Canada border. Exploration drilling in the area delineated pyrrhotite–pyrite massive sulfide deposits, iron formation, chert, and semi-massive sphalerite mineralized zones. High-resolution aeromagnetic data indicate a large (∼60 km2) composite subvolcanic intrusion underlies these iron-rich strata in the OB. The position of this inferred intrusion elucidates the low base metal content of known massive sulfide deposits, as they were too far away (6–10 km) from a heat source to have been favorable sites for base metal deposition. The relative abundance of Au and Zn in the OB, alongside correlation coefficients between metals in massive sulfide deposits, iron formation, and chert, indicates the rocks were affected by a low-temperature hydrothermal system under relatively shallow water conditions (<1000 m). Negative correlation between Na2O and CaO in basalt, and their mutual moderate positive correlation with immobile corundum (Al2O3), implies alteration in the upper part of the volcanic pile did not result in substantial element mobility in most samples. Geochemical data from mafic and felsic volcanic rocks plot mainly in the calc-alkaline field. Thus, the OB is most prospective for hosting Au-rich VMS deposits and future exploration should focus on paleo-thermal corridors and favorable stratigraphic horizons near the newly inferred composite subvolcanic intrusion.

Peculiarities of some mafic–ultramafic- and ultramafic-hosted massive sulfide deposits from the Main Uralian Fault Zone, southern Urals

2008 ◽  
Vol 33 (1) ◽  
pp. 49-69 ◽  
Author(s):  
P. Nimis ◽  
V.V. Zaykov ◽  
P. Omenetto ◽  
I.Yu. Melekestseva ◽  
S.G. Tesalina ◽  
...  
Keyword(s):  
Fault Zone ◽  
Massive Sulfide ◽  
Southern Urals ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits

Massive sulfide deposits of the Noranda area, Quebec. II. The Aldermac mine

1991 ◽  
Vol 28 (9) ◽  
pp. 1301-1327 ◽  
Author(s):  
T. J. Barrett ◽  
S. Cattalani ◽  
F. Chartrand ◽  
P. Jones
Keyword(s):  
Volcanic Rocks ◽  
Parental Magma ◽  
Mass Gain ◽  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Calc Alkaline ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits ◽  
Fractionation Trend ◽  
Felsic Volcanic

The original Aldermac mine near Noranda contained several Cu–Zn massive sulfide lenses hosted by felsic to mafic volcanic rocks of the late Archean Blake River Group. The original Nos. 3–6 orebodies, which consisted of massive pyrite, with lesser magnetite, pyrrhotite, chalcopyrite, and sphalerite, contained 1.87 Mt of Cu–Zn ore that averaged 1.47% Cu (Zn was not recovered). The orebodies occurred within felsic breccias and tuffs up to 100 m thick that are stratigraphically overlain by an extensive dome of mainly massive rhyolite and rhyodacite (up to 250 m thick and at least 550 m across). Most of the volcanic rocks that laterally flank and overlie the felsic dome are dacitic to andesitic flows, breccia, and tuff, with minor rhyolites, and associated subvolcanic sills of quartz-feldspar porphyry and gabbro.The new massive sulfide deposit, discovered in 1988, lies 150–200 m east of the mined-out orebodies, at a similar stratigraphic level within altered felsic breccia and tuff. The sulfides are mainly in the No. 8 lens, which contains 1.0 Mt at an average grade of 1.54% Cu, 4.12% Zn, 31.2 g/t Ag, and 0.48 g/t Au. Pyrite forms porphyroblastic megacrysts in a groundmass of pyrrhotite, sphalerite, magnetite, and chalcopyrite. A funnel-shaped, chloritized stockwork zone underlies the No. 8 lens and contains Cu-stringer mineralization. The No. 8 lens appears to be zoned, with overall decreasing Cu:Zn ratios from the core to the fringes of the lens. Massive sulfides in this lens have high Ag, Cd, and Hg contents relative to other massive sulfide deposits near Noranda.Ti versus Zr trends for least-altered Aldermac volcanic rocks indicate a more or less continuous magmatic fractionation trend ranging from high-Ti andesite to andesite, dacite, rhyodacite, and two distinct rhyolites (A and B). Most volcanic rocks were derived from a common parental magma that was transitional between tholeiitic and calc-alkaline compositions, as indicated by Ti–Y–Zr–Nb data and rare-earth-element distributions.Ti versus Zr trends in altered volcanic rocks indicate that silicification (mass gain) has affected some of the andesitic to rhyodacitic rocks, whereas chloritization (mass loss) has affected many of the rhyolitic rocks. Intermediate to mafic volcanic rocks above and lateral to the felsic dome are commonly silicified, possibly the result of hydrothermally remobilized silica derived from underlying felsic volcanic rocks.The orebodies appear to have formed at an eruptive hiatus between mafic → felsic and felsic → mafic cycles, during explosive activity and accumulation of felsic breccia and tuff. Ore was deposited mainly within a felsic fragmental sequence (rhyolite A), but before emplacement of the dome of rhyolite B. In compositionally diverse volcanic terrains, the contact between successive mafic–felsic and felsic–mafic cycles may be a good exploration target, in particular specific geochemical contacts within the felsic stratigraphy.

Sign in / Sign up

Export Citation Format

Share Document