Kuroko-type Massive Sulfide Deposits Research Articles

Exhalative deposits in eocene volcano-sedimentary rocks in the middle part of the Urumieh-Dokhtar magmatic belt: Detailed evidence from nabar deposit, west of Kashan, Urumieh – Dokhtar Magmatic Belt

Meso-Cenozoic magmatic belt of Urumieh–Dokhtar resulted from subduction of Neothetys oceanic crust beneath the Central Iran Block with Gondwanic signature is dominated by calc-alkaline to alkaline igneous rocks. The magmatic rocks has mainly occurred in submarine environments as volcanic-volcanoclastics with interlayers of sedimentary rocks in the Eocene, while it has occurred as intrusive and subvolcanics in the Neogene. In the Nabar area volcano-sedimentary rocks of Eocene have been covered unconformably by Oligo-Miocene sedimentary rocks (Qom Formation). The Eocene and Oligo-Miocene sequences are intruded by Middle-Upper Miocene intrusive and subvolcanic bodies. Igneous rocks of Eocene and Middle-Upper Miocene are of I-type and calc-alkaline belonging to arc and post-collisional setting of continental margin, respectively. The mineralization consists of pyrrhotite, pyrite, minor chalcopyrite and sphalerite, mainly hosted by Eocene volcanoclastics and particularly by the contact metamorphic halos of Qom formation. Irregular veinlets (stringer zone) in the lower part change to massive lenses upward which conformable with Eocene enclosing rocks, and have sharp contact with overlying Qom formation. Low grad ores with irregular shape (patches, veinlets, cavity and fracture filling) which are resulted from remobilization of previous mineralization, occurred within the contact metamorphic halos of Middle-Upper Miocene intrusions. According to geochemical analysis and mineralogical studies, iron, copper, gold, silver, arsenic, lead and zinc are enriched in the ore zone. Two types of fluid inclusion (L-V and L-VS) were distinguished in quartz veinlets. The homogenization temperature and salinity of fluid inclusions vary from 121 °C – 537 °C and 9–45 wt% NaCl equivalent, respectively. These data indicating the mixing of magmatic water with meteoric water in the later stage of mineralization. The δ34S values of pyrite and pyrrhotite which varies from 10.5 to 11.6 wt% compatible with massive sulfide and skarn type deposits. Field observations, mineralogical, geochemical, fluid inclusion and isotopic data suggest that, the Nabar deposit is probably a Kuroko type massive sulfide deposit which has been partly changed to skarn during penetration of Middle-Upper Miocene subvolcanic intrusions. The Kuroko type barite deposit of Dorreh and exhalative Mn deposit of Venarch and Shahrestanak were formed at the same time, within the Eocene volcanoclastic sequences.

Geological, geochemical and fluid inclusion studies on the evolution of barite mineralization in the Badroud area of Iran

A sequence of andesitic to dacitic volcanic and volcano-sedimentary rocks from the Late Eocene in the central part of the Urumieh–Dokhtar Magmatic Arc (UDMA) hosts a number of barite occurrences. The Badroud barite deposit is economically important deposit in the study area. The petro-geochemical characteristics of the deposit indicate that the least-altered volcanic host rock was produced as orogenic volcanic rock in the continental margin arc setting. It displays characteristics of a high-K and calc-alkaline series. Mineralized host rock mostly consists of barite crystals, and subordinate quartz, calcite, gypsum, fluorite and rare pyrite, chalcopyrite, galena, stibnite and cinnabar minerals. Petrographic studies revealed three types of barite. The early stage barite occurs as stockworks of large tabular and bladed crystals trending NW-SE in dextral strike-slip faults. The second stage barite precipitated as thick lensoid veins (50 × 3 m) of medium tabular crystals extending in a N-S direction. The third stage of barite mineralization occurs as thin acicular veins trending in a NW-SE direction. Chemically, the barite deposit is characterized by the low amounts of Sr, K, Ca and low Sr/Ba ratio. Fluid inclusion studies, applied to the first stage of bladed crystals of barite veinlets, show a high homogenization temperature of 256–338 °C and 8–13% (wt.) NaCl eq. salinity. Fluid inclusions in the second stage of barite mineralization are characterized by low salinity of 1–9% (wt.) NaCl eq. at a 160–214 °C homogenization temperature. The fluid inclusions occurring in the third stage of thin barite veins revealed high salinity of 19% (wt.) NaCl eq. with a 166–212 °C homogenization temperature. The fluid inclusion characteristics of the first stage barite show a hydrothermal origin with a deeper-seated source on the seafloor associated with a lower sequence of the Late Eocene felsic rock. The second stage barite, exposed beneath the upper sequence of Late Eocene andesite, was formed due to increased dilution, possibly with seawater. The third stage barite mineralization is associated with saline water and the interaction of fluid with volcanic and conglomerate host rocks. The obtained data show that the mineralization at Badroud barite deposit is similar to the Kuroko-type massive sulfide deposits in an arc setting.

مراحل تشکیل و تکوین کانسار سولفید توده ای غنی از طلای باریکا، خاور سردشت، شمال باختر پهنه دگرگونه سنندج- سیرجان: بر اساس مطالعه ساخت، بافت و میکروترمومتری سیالات درگیر

Barika gold (and silver) rich massive sulfide deposit is located 18 km east of Sardasht, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are Cretaceous metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesite, meta-tuffite, phyllite and slate rocks, where the meta-andesitic unit (Kmv1) is host rock to the deposit. Barika deposit is composed of stratiform ore and stringer zone. Stratiform part contains massive and banded sulfide and barite associated with subordinary silica bands underlain by stringer silicic zone. The massive and banded ore is surrounded by an extensive zone of silicic stringer veins and disseminated mineralization within strongly altered and deformed andesitic volcanic rocks. Ore mineral assemblages in stratiform part of the deposit are quite variable and consist of pyrite, sphalerite, galena, stibnite, a variety of sulfosalt minerals and gold (electrum). Ore mineral assemblages in silicic veins in the stringer zone are simpler and consist of pyrite, galena, sphalerite, tetrahedrrite and trace chalcopyrite. Average gold and silver grades in stratiform ore are 8.3 and 420 g/t respectively and in silicic stringer veins are 0.7 and 30 g/t. Base metal content in both parts of the deposit are less than 1%. Based on our research, Barika is an immature Kuroko type massive sulfide deposit, which contains only black ore. The Barika deposit underwent low-grade metamorphism and high grade deformation after the ore deposition event. Geologic processes appear to control the mode of occurrence of gold in the deposit. In synvolcanism stage, deposition of a gold–bearing low temperature (140-200°C) and low salinity (1-9.6 wt% NaCl) hydrothermal fluid formed a Kuroko black ore type deposit. In the stage of mineralization, invisible gold was concentrated in framboidal pyrite and other sulfide minerals. The main effect of progressive metamorphism (D1) on gold mineralization is recrystallization of the framboidal pyrite and migration of submicroscopic gold to the crystal boundary to form electrum under low to moderate strain. Highly strain and deformation (D2) on the deposit caused the remobilization of gold and accompanied As, Sb, Ag, and Pb minerals and continued to form coarse-grained electrum (up to 3 mm) in open space fractures. The formation of barren silica veins (D3) and high angle normal faults (D4) are the results of retrograde metamorphism.

Environmental geochemistry of a Kuroko-type massive sulfide deposit at the abandoned Valzinco mine, Virginia, USA

Abstract The abandoned Valzinco mine, which worked a steeply dipping Kuroko-type massive sulfide deposit in the Virginia Au–pyrite belt, contributed significant metal-laden acid-mine drainage to the Knight’s Branch watershed. The host rocks were dominated by metamorphosed felsic volcanic rocks, which offered limited acid-neutralizing potential. The ores were dominated by pyrite, sphalerite, galena, and chalcopyrite, which represented significant acid-generating potential. Acid–base accounting and leaching studies of flotation tailings – the dominant mine waste at the site – indicated that they were acid generating and therefore, should have liberated significant quantities of metals to solution. Field studies of mine drainage from the site confirmed that mine drainage and the impacted stream waters had pH values from 1.1 to 6.4 and exceeded aquatic ecosystem toxicity limits for Fe, Al, Cd, Cu, Pb and Zn. Stable isotope studies of water, dissolved SO 4 2 - , and primary and secondary sulfate and sulfide minerals indicated that two distinct sulfide oxidation pathways were operative at the site: one dominated by Fe(III) as the oxidant, and another by molecular O2 as the oxidant. Reaction-path modeling suggested that geochemical interactions between tailings and waters approached a steady state within about a year. Both leaching studies and geochemical reaction-path modeling provided reasonable predictions of the mine-drainage chemistry.

Relationship between Kuroko Mineralization and Paleostress Inferred from Vein Deposits and Tertiary Granitic Rocks In and Around the Hokuroku District, Northeast Japan

In the inner zone of the northeastern Japan arc, kuroko-type massive sulfide deposits of copper, lead, and zinc are related to submarine dacitic volcanism. There are four horizons that host such deposits in and around the Hokuroku district, the main deposits occurring at 14.32 Ma and coinciding with the end of an extensional regime followed by a weakly compressive regime. The change in tectonic style is indicated by the fracturing patterns in the vein deposits and Tertiary granitic rocks that were emplaced at 13.9 to 6.0 Ma and show similar alignment. They are also associated with explosive dacitic volcanism that occurred after the main kuroko mineralization. During the middle of the extensional regime, which was characterized by intensive submarine bimodal volcanism, no kuroko mineralization took place. Therefore, the observed change in tectonic regime might have been the trigger for kuroko mineralization. In addition to the main kuroko deposits, small-scale kuroko deposits can be found at different horizons. Two deposits are hosted within the first dacitic lava after the beginning of a marine transgression that coincided with the beginning of the extensional regime earlier than the main kuroko mineralization, and three deposits are hosted within dacitic rocks emplaced in the weakly compressive regime after the main kuroko mineralization. However, large-scale kuroko deposition appears to have been inhibited by explosive volcanism during this stage.

Contribution of Magmatic Fluid to the Active Hydrothermal System in the JADE Field, Okinawa Trough: Evidence from Fluid Inclusions, Oxygen and Helium Isotopes

The Okinawa trough is an active, backarc-spreading basin in which hydrothermal fluids are venting from black and white smoker chimneys along a felsic volcanic ridge. The Okinawa seafloor hydrothermal precipitates are comparable to Kuroko-type massive sulfide deposits in many respects. Both systems occur in backarc settings and are hosted by a suite of bimodal volcanic rocks. They show mound-like features and contain predominantly Zn-Pb-Cu metal associations. Aqueous and CO2-rich hydrothermal fluids from the JADE field exhibit high trapping temperatures (up to 420°C), and moderate salinities (up to 8% NaCl equiv.). We provide evidence for the contribution of volatiles from a magmatic source to the actively forming submarine hydrothermal system. The following features in the JADE field support a magmatic component within this system: (1) the presence of a shallow-level felsic magma chamber 1-2 km beneath the seafloor; (2) anomalously high heat flow within the hydrothermal field; (3) a high content of CO2 and CH4 in the hydrothermal plume; (4) effervescence of volatile species (e.g., CO2, CH4, H2, N2,) in the hydrothermal fluid that forms independent discharges as CO2-rich fluid through CO2 hydrate pipes near black smoker chimneys; (5) helium isotope data demonstrating that these gases were derived from a mantle source; (6) high-temperatures and moderate to high fluid-inclusion salinities; (7) oxygen isotopic compositions of altered rocks and quartz indicating that mineralizing fluids have a δ18O composition consistent with a mixture of magmatic fluid and seawater.

Neural network-based estimation of principal metal contents in the Hokuroku District, Northern Japan, for exploring kuroko-type deposits

The Hokuroku district, extending over 40 × 40 km2 in northern Japan, is known to be dominated by kuroko-type massive sulfide deposits that have a genetic relation to submarine volcanic activity. The deposits are hosted in a specific stratigraphic zone of Miocene volcanic rocks. Because kuroko-type deposits are under exploration in several countries, it is important to integrate the geologic and geochemical data that have been accumulated in the Hokuroku district to characterize the distribution of deposits and produce a map of mineral potential. Thus, we collected data on multiple chemical components from 1917 rock cores at 143 drillhole sites and concentrated on components with relatively large amounts of data, which are SiO2, Al2O3, and Fe2O3 as major elements and Cu, Pb, and Zn as trace elements. Although frequencies of these data can be approximated by normal or lognormal distributions, spatial correlation structures cannot be extracted from the semivariograms of each component nor from the cross-semivariograms between two components of the major or minor elements. To handle such complexity, a spatial method of modeling content distribution, SLANS, is developed by applying a feedforward neural network. The principle of SLANS is to train a network repeatedly to recognize the relation between the data value and the location and lithology of a sample point. One-hundred outputs for each element are obtained by changing the numbers of neurons in a middle layer from 1 to 10 and sample data used for training from 3 to 12, and finally one output is selected based on the estimation precision of the network which is restricted near the target point. After constructing a geologic distribution model from the geological column classified into 25 rock codes, three-dimensional distributions of Cu, Pb, and Zn contents are estimated over the study area. The content models are considered to be valid because high-content zones are located on the known mine sites and the margins of ancient volcanoes or calderas. Some zones are distributed along strikes of major deep-seated fractures in the district.

Incipient bitumen generation in Miocene siliceous sedimentary rocks from the Japan Sea

Samples of Quaternary through Miocene diatomaceous sediment and siliceous sedimentary rock from the Japan Sea (ODP Leg 128, Site 799) were examined to determine the origin of bitumen encountered during drilling, whether previously published studies using Rock-Eval pyrolysis have accurately assessed organic matter type and maturity, and if evidence exists to postulate the presence of a Kuroko-type massive sulfide deposit at depth or along depositional strike. Whole-rock total organic carbon:total nitrogen ratios have values ranging from 31 to 4. Elemental atomic H:C and O:C kerogen ratios decrease from ca 1.3 and 0.3, respectively, in Quaternary and Pliocene samples to 1.2 and 0.1, respectively, in samples obtained from the bottom of the hole. The bitumen ratio of these rocks increases from 50 mg bitumen/g OC at 700 mbsf to 150 mg bitumen/g at 1000 mbsf. The kerogen in these samples comprises a mixture of marine and terrigenous organic material that reaches the earliest stages of catagenesis in the bottom part of this hole. The bitumen is dominated by asphaltenes, resins and polar components. Because these compounds have very high boiling points, Rock-Eval pyrolysis does not assess the thermal maturity, or organic matter type accurately in the early stages of catagenesis. The bitumens have a very low thermal maturity and the observed degree of thermal alteration is consistent with the modern geothermal gradient in the Kita-Yamato trough.

A sulfur isotope study of volcanogenic massive sulfide deposits of the Eastern Black Sea province, Turkey

Kuroko-type massive sulfide deposits of the Eastern Black Sea province of Turkey are related to the Upper Cretaceous felsic lavas and pyroclastic rocks, and associated with clay and carbonate alteration zones in the footwall and hangingwall lithologies. A complete upward-vertical section of a typical orebody consists of a stringer-disseminated sulfide zone composed mainly of pyrite and chalcopyrite; a massive pyrite zone; a massive yellow ore consisting mainly of chalcopyrite and pyrite; a black ore made up mainly of galena and sphalerite with minor amounts of chalcopyrite, bornite, pyrite and various sulfosalts; and a barite zone. Most of the deposits in the province are associated with gypsum in the footwall or hangingwall. The paragenetic sequence in the massive ore is pyrite, sphalerite, chalcopyrite, bornite, galena and various sulfosalts, with some overlap between the mineral phases. Massive, stringer and disseminated sulfides from eight kuroko-type VMS deposits of the Eastern Black Sea province have a δ 34S range of 0–7 per mil, consistent with the δ 34S range of felsic igneous rocks. Sulfides in the massive ore at Madenkoy (4.3–6.1 per mil) differ isotopically from sulfides in the stringer zone (6.3–7.2 per mil) suggesting a slightly increased input of H2S derived from marine sulfate with time. Barite and coarse-grained gypsum have a δ 34S range of 17.7–21.5 per mil, a few per mil higher than the δ 34S value of contemporaneous seawater sulfate. The deposits may, therefore, have formed in restricted basins in which bacterial reduction of sulfate was taking place. Fine-grained, disseminated gypsum at Kutlular and Tunca has δ 34S values (2.6–6.1 per mil) overlapping those of ore sulfides, indicating sulfide oxidation during waning stages of hydrothermal activity.

Geodynamic setting of Early Devonian kuroko-type sulfide deposits in the eastern Klamath Mountains (Northern California) inferred by the petrological and geochemical characteristics of the associated island-arc volcanic rocks

In the West Shasta copper-zinc district, Kuroko-type massive sulfide deposits are present in Early Devonian volcanic rocks consisting of the Copley Greenstone and the overlying Balaklala Rhyolite. The Copley Greenstone is composed of pillow lava (mainly basalts with subordinate andesites) and pyroclastic deposits. High Mg andesites occur near the top of the 1,800-m-thick volcanic succession. The Balaklala Rhyolite, 1,000 m thick, consists of highly siliceous rhyolite flows, conglomerates, and tuffs. Both units were deposited in a submarine environment. The sulfide deposits are localized in the rhyolitic flows of the upper part of the middle unit of the Balaklala Rhyolite.Petrological and geochemical data show that these lavas belong to a tholeiitic suite formed in an immature island arc. At the close of Copley eruptions, the island arc underwent rifting and tectonic extension. This is suggested by the presence of boninites, a feeder dike system for the Balaklala Rhyolite, and bimodal volcanism. The extensional environment is similar to that classically observed in the domain of the Kuroko massive sulfide deposits. This rifting led subsequently to the development of a back-arc basin represented by the Trinity basalts associated with an ophiolitic sequence.

Ore-related breccias in volcanoplutonic arcs

An overview of breccias related to a variety of base metal, precious metal, and lithophile element deposits in volcanoplutonic arcs permits definition of six possible mechanisms for subsurface brecciation.1. Release of magmatic-hydrothermal fluids from high-level hydrous magma chambers during second boiling and subsequent decompression generates a spectrum of breccia types in which fragments may suffer collapse and/or ascent. Single or multiple intrusion-related breccia pipes and pre- and intermineral breccias in porphyry copper deposits provide widespread examples.2. Magmatic heating and expansion of meteoric pore fluids may lead to brecciation, commonly of late or postmineral age and including pebble dikes, in porphyry-type and related deposits. Magmatic heating of rocks saturated with seawater may cause submarine hydrothermal eruptions late in the emplacement histories of Kuroko-type massive sulfide deposits; many of the resultant breccias underwent limited sedimentary transport. Overpressuring of heated fluids beneath semipermeable, partly self-sealed cap rocks may lead to brecciation and subaerial hydrothermal eruptions in shallow epithermal precious metal settings; magmatic heating or tectonic disturbance may have triggered brecciation.3. Interaction of cool ground waters with subsurface magma can generate phreatomagmatic explosions. Postmineral phreatomagmatic diatremes associated with porphyry systems and premineral diatremes with epithermal precious (+ or - base) metal deposits were generated in this manner; these attained the palcosurface to produce pyroclastic base surge and fall deposits that accumulated as tuff rings around maar craters.4. Magmatic-hydrothermal brecciation may lead to disruption of rocks through to the paleosurface, decompression, and fragmentation and eruption of the top part of an underlying magma chamber. Pre- and postmineral magmatic diatremes of this sort are inferred to accompany a few porphyry-type and other base and precious metal systems; they were manifested at the palcosurface by accumulations of pyroclastic fall and flow deposits.5. Breccias may result from mechanical disruption of wall rocks during subsurface movement of magma. Any intrusion-related deposit may include such intrusion breccias.6. Tectonic breccias resulting from fault displacement may accompany any type of ore deposit.A continuum exists between many of these breccia types and it is difficult to identify unique criteria for their unambiguous distinction.

Are porphyry copper and Kuroko-type massive sulfide deposits incompatible?

Research Article| January 01, 1980 Are porphyry copper and Kuroko-type massive sulfide deposits incompatible? Richard H. Sillitoe Richard H. Sillitoe 1Department of Mining Geology, Royal School of Mines, Imperial College of Science and Technology, Prince Consort Road, London SW7 2BP, England Search for other works by this author on: GSW Google Scholar Author and Article Information Richard H. Sillitoe 1Department of Mining Geology, Royal School of Mines, Imperial College of Science and Technology, Prince Consort Road, London SW7 2BP, England Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1980) 8 (1): 11–14. https://doi.org/10.1130/0091-7613(1980)8<11:APCAKM>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Richard H. Sillitoe; Are porphyry copper and Kuroko-type massive sulfide deposits incompatible?. Geology 1980;; 8 (1): 11–14. doi: https://doi.org/10.1130/0091-7613(1980)8<11:APCAKM>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract It is suggested that porphyry copper deposits and Kuroko-type massive sulfide deposits are incompatible because the former are generated beneath andesitic-dacitic stratovolcanoes, whereas the latter are precipitated during or after rhyolitic to rhyodacitic volcanism within resurgent calderas. Episodes of lithospheric tension in subduction-related arcs may favor cauldron subsidence at the expense of stratovolcano development. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.