Mineralization, alteration and geochemical characteristics of host rocks in the Rangraz iron oxide-copper mineralization area, north Saveh, central part of Urumieh–Dokhtar magmatic arc

Abstract Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.

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The Discovery of the Romero VMS Deposit and Its Bearing on the Metallogenic Evolution of Hispaniola during the Cretaceous

Minerals ◽

10.3390/min8110507 ◽

2018 ◽

Vol 8 (11) ◽

pp. 507 ◽

Cited By ~ 1

Author(s):

Lisard Torró ◽

Joaquín Proenza ◽

Julio Espaillat ◽

Albert Belén-Manzeta ◽

María Román-Alday ◽

...

Keyword(s):

Open Space ◽

Massive Sulfide ◽

Axial Position ◽

Greater Antilles ◽

Stratigraphic Sequence ◽

Copper Mineralization ◽

Seawater Sulfate ◽

Extensional Tectonic ◽

Volcaniclastic Rocks ◽

Host Rocks

The recently discovered Romero deposit, located in the Tres Palmas district, Cordillera Central of the Dominican Republic, has probable reserves of 840,000 oz gold, 980,000 oz silver and 136 Mlb copper. Mineralization is hosted by intermediate volcanic and volcaniclastic rocks of the lower stratigraphic sequence of the Cretaceous Tireo formation. The andesitic host rocks yield a U-Pb zircon concordia age of 116 ± 10 Ma. Au–Ag–Cu(–Zn) mineralization is divided into: (1) an upper domain with stacked massive sulfide lenses and sulfide dissemination within a 20-m-thick level of massive anhydrite-gypsum nodules, and (2) a lower domain with a high-grade stockwork mineralization in the form of cm-scale veins with open space fillings of fibrous silica and chalcopyrite, sphalerite, pyrite (+electrum ± Au–Ag tellurides). The δ34S values of sulfides from the upper (−7.6 and +0.9‰) and lower (−2.4 and +5.6‰) domains are consistent with a heterogeneous sourcing of S, probably combining inorganically and organically induced reduction of Albian-Aptian seawater sulfate. Despite this, a magmatic source for sulfur cannot be discarded. The δ34S (+19.2 and +20.0‰) and δ18O (+12.5 and +14.2‰) values of anhydrite-gypsum nodules are also consistent with a seawater sulfate source and suggest crystallization in equilibrium with aqueous sulfides at temperatures higher than 250 °C. These data point to a classification of Romero as a volcanogenic massive sulfide (VMS) deposit formed in an axial position of the Greater Antilles paleo-arc in connection with island arc tholeiitic magmatism during a steady-state subduction regime. Circulation of hydrothermal fluids could have been promoted by a local extensional tectonic regime expressed in the Tres Palmas district as a graben structure.

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Geochemical characteristics of igneous host rocks of Lubin-Zardeh Au-Cu deposit, NW Iran

Ore Geology Reviews ◽

10.1016/j.oregeorev.2020.103496 ◽

2020 ◽

Vol 122 ◽

pp. 103496 ◽

Cited By ~ 1

Author(s):

H. Zamanian ◽

S. Rahmani ◽

R. Zareisahamieh ◽

A. Pazoki ◽

X.Y. Yang

Keyword(s):

Geochemical Characteristics ◽

Nw Iran ◽

Host Rocks

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Ore Formation During Jurassic Subduction of the Tethys Along the Eurasian Margin: Constraints from the Kapan District, Lesser Caucasus, Southern Armenia

Economic Geology ◽

10.5382/econgeo.4640 ◽

2019 ◽

Vol 114 (7) ◽

pp. 1251-1284 ◽

Cited By ~ 4

Author(s):

Johannes Mederer ◽

Robert Moritz ◽

Massimo Chiaradia ◽

Richard Spikings ◽

Jorge E. Spangenberg ◽

...

Keyword(s):

Middle Jurassic ◽

Late Jurassic ◽

Ore Deposits ◽

Sulfide Deposit ◽

Short Time Interval ◽

Ore Formation ◽

Magmatic Arc ◽

Argillic Alteration ◽

Lesser Caucasus ◽

Host Rocks

Abstract The Kapan mining district in the southernmost Lesser Caucasus is one of the few locations along the central Tethyan metallogenic belt where ore-forming processes were associated with magmatic arc growth during Jurassic Tethys subduction along the Eurasian margin. Three ore deposits of the Kapan district were investigated in this study: Centralni West, Centralni East, and Shahumyan. The ore deposits are hosted by Middle Jurassic andesitic to dacitic volcanic and volcaniclastic rocks of tholeiitic to transitional affinities below a late Oxfordian unconformity, which is covered by calc-alkaline to transitional Late Jurassic-Early Cretaceous volcanic rocks interlayered with sedimentary rocks. The mineralization consists of veins, subsidiary stockwork, and partial matrix replacement of breccia host rocks, with chalcopyrite, pyrite, tennantite-tetrahedrite, sphalerite, and galena as the main ore minerals. Centralni West is a dominantly Cu deposit, and its host rocks are altered to chlorite, carbonate, epidote, and sericite. At Centralni East, Au is associated with Cu, and the Shahumyan deposit is enriched in Pb and Zn as well as precious metals. Both deposits contain high-sulfidation mineral assemblages with enargite and luzonite. Dickite, sericite, and diaspore prevail in altered host rocks in the Centralni East deposit. At the Shahumyan deposit, phyllic to argillic alteration with sericite, quartz, pyrite, and dickite is dominant with polymetallic veins, and advanced argillic alteration with quartz-alunite ± kaolinite and dickite is locally developed. The lead isotope composition of sulfides and alunite (206Pb/204Pb = 18.17–18.32, 207Pb/204Pb = 15.57–15.61, 208Pb/204Pb = 38.17–38.41) indicates a common metal source for the three deposits and suggests that metals were derived from magmatic fluids that were exsolved upon crystallization of Middle Jurassic intrusive rocks or leached from Middle Jurassic country rocks. The δ18O values of hydrothermal quartz (8.3–16.4‰) and the δ34S values of sulfides (2.0–6.5‰) reveal a dominantly magmatic source at all three deposits. Combined oxygen, carbon, and strontium isotope compositions of hydrothermal calcite (δ18O = 7.7–15.4‰, δ13C = −3.4−+0.7‰, 87Sr/86Sr = 0.70537–0.70586) support mixing of magmatic-derived fluids with seawater during the last stages of ore formation at Shahumyan and Centralni West. 40Ar/39Ar dating of hydrothermal muscovite at Centralni West and of magmatic-hydrothermal alunite at Shahumyan yield, respectively, a robust plateau age of 161.78 ± 0.79 Ma and a disturbed plateau age of 156.14 ± 0.79 Ma. Re-Os dating of pyrite from the Centralni East deposit yields an isochron age of 144.7 ± 4.2 Ma and a weighted average age of the model dates of 146.2 ± 3.4 Ma, which are younger than the age of the immediate host rocks. Two different models are offered, depending on the reliability attributed to the disturbed 40Ar/39Ar alunite age and the young Re-Os age. The preferred interpretation is that the Centralni West Cu deposit is a volcanogenic massive sulfide deposit and the Shahumyan and Centralni East deposits are parts of porphyryepithermal systems, with the three deposits being broadly coeval or formed within a short time interval in a nascent magmatic arc setting, before the late Oxfordian. Alternatively, but less likely, the three deposits could represent different mineralization styles successively emplaced during evolution and growth of a magmatic arc during a longer time frame between the Middle and Late Jurassic.

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Mineral Exploration in Mawat Region, Kurdistan-Iraq, Based on Satellite Data and Terrain Prospection

Athens Journal of Sciences ◽

10.30958/ajs.8-4-2 ◽

2021 ◽

Vol 8 (4) ◽

pp. 249-272

Author(s):

Marinko Oluić ◽

Sreten Romandić ◽

Ratko Vasiljević

Keyword(s):

Satellite Data ◽

Mineral Exploration ◽

Digital Processing ◽

Field Work ◽

Measured Concentration ◽

Copper Mineralization ◽

Rock Formations ◽

Lithological Composition ◽

Color Composite ◽

Host Rocks

The main goal of the presented exploration was to estimate potential for mineralization in the Mawat ophiolitic massif in Kurdistan, Iraq. The aim of the study was to explore existing copper mineralization and assessor elements gold, platinoids and chromium. Geological exploration detected two types of Cu occurrence a) secondary Cu carbonates (malachite) and b) Cu sulfides (chalcopyrite-pyrite). The Mawat region is mostly built of ultrabasic and basic rocks: peridotites, gabbros, serpentinites and basalts which are heavily deformed, with faults mostly oriented NNW-SSE, and NE-SW. The first phase of exploration comprised digital processing of ASTER and QuickBird satellite images, with appropriate geometrical and radiometric corrections and transformation into coordinate system. Color composite images were produced in different scales. They served to define lithological composition, tectonic settings, location of the points of interest etc. The field work was designed to check satellite data in situ, with focus on perspective rock formations, which might host copper mineralization, and other elements. The host rocks of the ore occurrences are primarily gabbros and metagabbros intersected by diabase dykes, epidote and quartz veins. Secondary mineralization is the product of surficial weathering and it is represented by malachite and limonite. The geophysical survey was very useful in the detection of area with elevated induced polarization and low resistivity. Three perspective areas have been selected for detailed explorations: Waraz, Mirava-Chenara and Konjirin-Kuradawi. The concentration of copper varies highly in very wide ranges; the maximum measured concentration of Cu was determined in Waraz area 6.7%. Some rock samples also show concentration of gold from 0.36 to 2.59 ppm Au. Keywords: Mawat ophiolitic massif, geologic-geophysical explorations, copper mineralization, Kurdistan-Iraq

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Ballooning emplacement and alteration of the Chah-Musa subvolcanic intrusion (NE Iran) inferred from magnetic susceptibility and fabric

Geological Magazine ◽

10.1017/s0016756819001158 ◽

2019 ◽

Vol 157 (4) ◽

pp. 621-639

Author(s):

Ali Seifivand ◽

Maryam Sheibi

Keyword(s):

Magnetic Susceptibility ◽

Small Diameter ◽

Copper Deposit ◽

Magmatic Arc ◽

Degree Of Anisotropy ◽

Bulk Magnetic Susceptibility ◽

Intense Deformation ◽

Magnetic Lineations ◽

Host Rocks ◽

Subvolcanic Intrusion

AbstractThe porphyritic diorite Chah-Musa subvolcanic intrusion is located in the Toroud-Chah Shirin magmatic arc in the northern Central Iranian structural zone. The elliptical Chah-Musa body hosts a copper deposit and intrudes an Eocene sequence of volcanic breccia, agglomerate and red tuffaceous sediment. High magnetic susceptibility values are attributed to the presence of magnetite as a magnetic carrier. Changes in bulk magnetic susceptibility correlate with zonation of alteration in the intrusion. Although the degree of anisotropy of magnetic susceptibility decreases due to hydrothermal alteration, the field observations confirm that this parameter can be used as a strain marker. Strongly oblate magnetic ellipsoids are found in the eastern half of the intrusion where isolated outcrops of flat-lying tuffaceous host cover dioritic rocks (roof zone). Stations with prolate ellipsoids mostly belong to the centre of the intrusion where the magnetic lineations plunge steeply. They are interpreted as indicating the main feeder zone. The concentric fabric pattern at the periphery of intrusion, the oblate magnetic ellipsoids at the roof, the highest anisotropy degree along the small diameter of the intrusion, and an intense deformation of the host rocks, especially at the western margin, all are evidence that the intrusion was ballooning during the late stages of its emplacement. Ascent and emplacement of the Chah-Musa body is ascribed to the tensional space provided by a dextral shear zone created by the regional left-lateral movement on the bounding Anjilow and Toroud strike-slip faults.

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The Onto Cu-Au Discovery, Eastern Sumbawa, Indonesia: A Large, Middle Pleistocene Lithocap-Hosted High-Sulfidation Covellite-Pyrite Porphyry Deposit

Economic Geology ◽

10.5382/econgeo.4766 ◽

2020 ◽

Vol 115 (7) ◽

pp. 1385-1412

Author(s):

David R. Burrows ◽

Michael Rennison ◽

David Burt ◽

Rod Davies

Keyword(s):

Sea Level ◽

Shallow Depth ◽

Middle Pleistocene ◽

High Sulfidation ◽

Copper Mineralization ◽

Argillic Alteration ◽

Zircon Crystallization ◽

Current Resource ◽

Advanced Argillic Alteration ◽

Host Rocks

Abstract In 2013, a diamond drill program tested an extensive advanced argillic alteration lithocap within the Hu’u project on eastern Sumbawa Island, Indonesia. A very large and blind copper-gold deposit (Onto) was discovered, in which copper occurs largely as disseminated covellite with pyrite, and as pyrite-covellite veinlets in a tabular block measuring at least 1.5 × 1 km, with a vertical thickness of ≥1 km. Copper and gold are spatially related with a series of coalesced porphyry stocks that intrude a polymictic diatreme breccia capped by a sequence of intramaar laminated siltstones, volcaniclastic and pyroclastic rocks, and overlain by andesite flows and domes. The porphyry intrusions were emplaced at shallow depth (≤1.3 km), with A-B–type quartz veinlet stockworks developed over a vertical interval of 300 to 400 m between ~100 and 500 m below sea level (bsl), 600 to 1,000 m below the present surface, which is at 400 to 600 m above sea level. In the area drilled at Onto, the diatreme breccia, all porphyry intrusions and, to a lesser extent, the surrounding older andesite sequence have all been overprinted by intense subhorizontal advanced argillic alteration, zoned downward from illite-smectite, quartz-dickite to quartz-alunite and quartz-pyrophyllite ± diaspore alteration. The alteration package includes two particularly well-developed zones of residual quartz with vuggy texture in subhorizontal zones at shallow depth, the upper one is still porous but the lower horizon, ~100 m thick, is largely silicified and is located at or near the top of the quartz-alunite alteration. Mineralization starts below the lowermost silicic horizon with more than 90% of the current resource in quartz-pyrophyllite-alunite and quartz-alunite alteration. Mineralization is dominated by a high-sulfidation assemblage of covellite-pyrite ± native sulfur largely in open-space fillings and replacements, but also as discrete pyrite-covellite and covellite only veins down to at least 1 km. Although the greatest amount of copper occurs as paragenetically late covellite deposited during formation of the advanced argillic alteration, approximately 60% of resource at 0.3% Cu cutoff still occurs within the porphyry stocks, indicating the porphyry stocks are a fundamental control on mineralization. There is considerable remobilization and dispersion of copper and, to a lesser extent, gold into the surrounding pre-mineral breccia and the late intermineral intrusions from the two earliest porphyry phases, resulting in quite consistent copper and gold grades throughout the currently delineated mineral resource. The very high sulfidation state of the mineralization is thought to be a consequence of the metal-bearing ore fluids cooling in the advanced argillic-altered host rocks in the absence of a rock buffer. Early chalcopyrite-bornite ± pyrite mineralization with potassic ± chloritic and sericitic alteration is only preserved on the margins of the system and more rarely at depth in a few holes 600 m bsl (~1,100 m below surface) but makes up only a small proportion (~8%) of the current resource. The Onto system is exceptionally young and formed rapidly in the middle Pleistocene and is not significantly eroded. A U-Pb zircon age for the andesite that caps the volcanosedimentary host rocks provides a maximum age of 0.838 ± 0.039 Ma, with a slightly younger porphyry zircon crystallization age of 0.688 ± 0.053 Ma. Re-Os dating of molybdenite that is associated with both the quartz vein stockwork and high-sulfidation assemblage copper mineralization shows overlap between 0.44 ± 0.02 and 0.35 ± 0.0011 Ma. 40Ar/39Ar ages for alunite within the advanced argillic alteration block ranges from 0.98 ± 0.22 to 0.284 ± 0.080 Ma, and alunite closely associated with covellite spans a period from 0.537 ± 0.064 to 0.038 ± 0.018 Ma.

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Fault reconstructions using aeromagnetic data in the Great Bear magmatic zone, Northwest Territories, Canada

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2014-0035 ◽

2014 ◽

Vol 51 (10) ◽

pp. 927-942 ◽

Cited By ~ 6

Author(s):

Nathan Hayward ◽

Louise Corriveau

Keyword(s):

Iron Oxide ◽

Vertical Axis ◽

Fault System ◽

Aeromagnetic Data ◽

Block Rotation ◽

Magmatic Arc ◽

The North ◽

Copper Gold ◽

Great Bear Magmatic Zone ◽

Transcurrent Faults

The Great Bear magmatic zone, located in Wopmay orogen, is a 1.875–1.84 Ga belt, 450 km long by 100 km wide of volcanic and allied plutonic rocks interpreted as a Paleoproterozoic magmatic arc. The belt, which contains economically important mineralization, was folded and subsequently cut by a swarm of northeast-striking transcurrent faults, which are part of a regional conjugate fault system interpreted to result from terminal collision of the Nahanni – Fort Simpson terrane. Fault reconstructions based on the interpretation of aeromagnetic data and geological maps provide first-order models of deformation mechanisms associated with, and the configuration of the Great Bear magmatic zone prior to, its dissection by northeast-striking transcurrent faults. The models show that vertical axis block rotation (plane strain) of ∼4.5° can explain fault offsets in the south, but that greater rotation is required to explain many of the displacements in the north. However, offsets on transcurrent faults that border the Camsell River district are greater than can be explained by vertical axis block rotation model alone and may include a component of Mesoproterozoic contractional deformation associated with the Racklan–Forward orogeny. Following reconstruction, iron oxide alkali alteration and associated mineralization, which pre-date transcurrent faulting, form a pair of northerly trending zones on the east and west margins of the belt. We suggest that these zones, whose exposure is related to broad synclinal folding of some of the oldest rocks in the Great Bear magmatic zone, are where iron oxide copper–gold (IOCG)-targeted exploration efforts should be focused on these areas in both outcrop and subcrop.

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